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Remediation of Soil Contaminated by Heavy Metals Using Biochar: Strategies and Future Prospects
... Depending on how they will be used to remove particular contaminants, different dopants are added to the biochar made from different biomass sources. To prepare active biochar compounds, a variety of traditional synthesis processes are used, but the process requires a significant investment of time, money, and energy (Zakaria et al. 2023;Chen et al. 2023). ...
The access to drinkable water is a critical challenge in the context of the rising urbanization and industrialization, calling for advanced technologies to clean contaminated waters and wastewater. Here we review the use of metal oxides biochar composites to treat pollution by hevay metals and dyes. We focus on the synthesis of metal oxide nanobiochar; the treatment of pollution by mercury, lead, methylene blue and methyl orange; life cycle analysis; and techno-economical assessment. Metal oxide nanoparticles can act as photocatalysts to allow for the complete mineralization of organic pollutants. For instance, the doping of tin oxide nanoparticles into biochar surface degraded 99.5% of methylene blue dye after 105 min. Ball-milled magnetic nanobiochar achieves 99% mercury removal in 720 min. The presence of biochar enhanced the uptake of contaminants on nanoparticles and facilitated the photocatalytic reaction
... Particularly, biochar obtained from different raw materials shows different attributes such as functional groups, permeability, and surface area (Lebrun et al., 2020). Chen et al. (2023) applied 12 kinds of biochar to evaluate the feedstocks effects and pyrolysis parameters on the soil characteristics and by key impacts on soil biological and physicochemical traits, nutrient contents under polluted conditions via several mechanisms, and eventually donating toward carbon sequestration with reduced emission of greenhouse gases and climate change mitigation (Murtaza et al., 2021b). Gathering feedstock, performing pretreatments, and converting organic wastes into biochar using a variety of techniques are all processes in the synthesis of biochar from organic wastes. ...
... For example, biochar is typically alkaline, which can reduce the mobility of certain heavy metals that are more mobile under acidic conditions. The exudates from hyperaccumulator plants can affect pH and redox conditions locally within the rhizosphere, potentially altering heavy metal mobility (Chen et al., 2023b). Moreover, biochar and pyrolysis significantly increase the soil's cation exchange capacity (CEC) due to their negatively charged surface, which allow them to attract and hold onto cations, including heavy metals (Sun et al., 2022). ...
... Two other characteristics of fundamental relevance to the adsorptive process of biochar are the surface charge, typically negative, which enhances the interaction between biochar and cationic compounds, and porosity, which, when associated with the presence of functional groups, contributes to the increased adsorption capacity of contaminants, essentially heavy metals (Sackey et al., 2021;Chen et al., 2022;Krishnasamy et al., 2022). ...
O biochar é um produto de biomassa submetido ao processo de pirólise, sob altas temperaturas e ausência de oxigênio. É um material que dispõe de uma produção de baixo custo e com vastas opções de aplicabilidade, entre as mais exploradas estão: recuperação de solos degradados pelas atividades agropecuárias e sorção de contaminantes através da biorremediação de áreas poluídas. Deste modo, este material objetiva demonstrar a produção e caracterização do biocarvão, e discutir suas aplicações para melhoramento de solos e redução da concentração de substâncias tóxicas e nocivas, como corantes têxteis e metais pesados, descartados indevidamente no meio ambiente, tudo isso a partir da seleção de referências relevantes que abordam de modo claro e consistente a aplicação do biochar e seus efeitos. A partir dos trabalhos analisados constatou-se que o biochar exerce um alto poder de sorção de uma variedade de poluentes emergentes, como: fármacos, pesticidas, corantes têxteis e metais pesados, retendo, em algumas aplicações, até 90% da concentração original do contaminante. Além disso, o biocarvão é uma das principais alternativas para recuperação de solos explorados por longos períodos como áreas de cultivo ou de pastagens, obtendo, para a grande maioria das aplicações do biochar a melhoria das propriedades do solo, como: pH, retenção de nutrientes e teor de carbono. Portanto, o biochar é um material carbonáceo com alta viabilidade produtiva e grande eficiência nos processos de biorremediação e recuperação de áreas degradadas.
The objective of the study was to determine the influences of biochar amendments and Azolla sp application on soil chemical value, lead (Pb) content, and growth of paddy. The research was conducted in Growth Centre LLDIKTI I, Medan, Sumatera Utara, Indonesia, from April to July 2014. The research design used a factorial randomized block design with three replications. The first factor was Azolla sp application: without Azolla (A0); Azolla pinnata (A1); Azolla mikropilla (A2)] and the second factor was biochar amendment without biochar (B0); RSB-Rice straw biochar (B1), RHB-Rice husk biochar (B2), CPB-coconut peat biochar (B3), OPB-Oil Palm Empty Bunch biochar (B4)]. The result showed that the biochar amendment treatments had significant differences (P<0.05) in all soil chemical values and growth parameters of paddy. The Azolla application showed significant differences (P<0.05) in plant height, number of tillers, shoot dry weight, root dry weight, and Pb content in the root. The interaction among the Azolla sp and the biochar amendments showed significant differences (P<0.05) in a number of the tillers. It was concluded that the application of rice husk biochar and Azolla microphylla was able to increase soil chemical properties, increase the growth of paddy, and also increase the Pb content in soil, leaves, and roots.
The study has been conducted on the water quality level of the Babak River around Kebon Kongok landfill, Lombok. This research was conducted considering that water has many benefits in the daily lives of people. This research uses an experimental method by analyzing physical parameters (temperature, conductivity, pH, and total dissolved solids (TDS)), and chemical parameters in the form of heavy metal content lead (Pb), iron (Fe), manganese (Mn), and copper (Cu)). Analysis results were compared with quality standards based on Ministry of Health Regulation No. 32 of 2017 concerning water quality. Based on the study, it was found that the farther the distance of water measured from the source of pollution, the value of the physical and chemical parameters of water will be smaller. Most of the physical parameter test results show the Babak River water quality is still at the safe threshold limit but there is 1 point of river water that is polluted due to the distance that is too close to the active zone. Chemical parameters show the results of heavy metal content below the threshold limit. Analysis of the water quality shows that the water is still in good condition, which is below the threshold set by the Indonesian government.
Biochar production and application have become increasingly popular in the past 15 years. Biochar, derived from diverse biomass types, offers a rich carbon source created through thermal combustion. Biochar production primarily depends on pyrolysis conditions and feedstock type. This review focuses on the multifaceted aspects of biochar, encompassing hydrothermal carbonization, gasification, and pyrolysis temperatures in biochar production and its role in bioeconomy and soil remediation. Biochar has yielded valuable insights, notably in decreasing nutrient leaching, curbing greenhouse gas (GHG) emissions, reducing the bioavailability of environmental pollutants, sequestering carbon (C) in soils, and enhancing agricultural productivity. Consequently, it has emerged as a valuable commodity for the bioeconomy, which involves harnessing bioresources through bioengineering to create economically valuable products. As a marketable output, biochar finds application in energy, diverse biochar-based product manufacturing, and the agricultural sector. Thus, biochar production not only enhances soil quality but also unlocks additional revenue streams. This review underscores the critical role of feedstock selection and pyrolysis conditions in optimizing biochar production. Furthermore, it highlights biochar as a sustainable and effective tool for improving various soil types and remediating soil contamination caused by organic impurities, including persistent organic compounds and antibiotics.
This paper studied the leaching effect of various strains on the heavy metal contaminated soil around the mining area of Dong’an County, Hunan Province. By measuring the form of heavy metals of antimony and arsenic in the soil and the concentration of heavy metals in the solution, the remediation effect of microorganisms in different pH conditions and different soil environments on the heavy metal contaminated soil was explored. The results showed that Acidithiobacillus thiooxidans ( A.c ) and Acidithiobacillus thiooxidans ( A.t ) had better leaching effect. Under the initial conditions of pH equal to 1, 10% bacteria content and 10 g/L S, the active metal components in the soil could be dissolved. The results showed that microorganism could remediate the soil contaminated with heavy metals and make the available metal components in the soil reach the safety standard.
With the increasing threat of soil heavy metal pollution to the quality of agricultural products and human health, biochar has been widely studied as a substance that can effectively adsorb heavy metals. This study reviewed the preparation of biochar as well as its types and properties and discussed the role and potential risks of biochar in the remediation of heavy metals in soil. Heavy metal pollution in the soil mainly comes from industrial pollution discharge, good drainage, the usage of chemical fertilizers, pesticides and other illegal applications, and it has great influence on plants, human health and soil environment. Biochar can not only adsorb heavy metals in the soil effectively, but also keep the soil fertile and improve crop yields. In addition, different properties of biochar are controlled by different raw materials and production conditions, such as pH, specific surface area and cation exchange capacity. These properties also determine their different interaction mechanisms. The direct effects mainly include complexation, reduction, ion exchange, electrostatic attraction and precipitation, while the brief effects affect the mobility and bioavailability of heavy metals in soil. The risk of biochar application that provides the basis for the production and utilization of biochar in the future was also discussed in the end.
Temperature, light intensity (LI), adsorbent source and concentrations are key external factors affecting algal metabolism and thus metal-accumulation mechanisms. In this study, the alga Sarcodia suiae was exposed individually to a range of temperature (15, 20, and 25 °C), and LI (30, 55, and 80 μmol photons m-2 s-1) at initial arsenate [As(V)] concentration (iconc: 0, 62.5, 125, 250, and 500 μg L-1) conditions, to investigate the variations of total arsenic (TAs) and inorganic arsenic (iAs) accumulation mechanisms in the algal body. Temperature significantly affected TAs and arsenite [As(III)] production and maximum absorption were obtained at 15 °C, which was significantly stimulated by increasing iconc. However, the temperature did not affect As(V) production. LI had no significant effect on TAs or iAs production, although maximum absorption was estimated in 80 μmol photons m-2 s-1. The iAs component of TAs was much greater in the temperature experiment particularly under 250-500 μg L-1iconc than in the LI experiment, is witnessed. Overall, temperature and iconc strongly affected As accumulation. The predominant iAs produced was As(III), regardless of temperature or LI, suggesting that the alga favored As(III) biosorption. Also, visible effects on the morphology of this alga were adverse with increased concentration and environmental factors did affect the difference somewhat. Our results contribute to improving our understanding of the effects of the tested factors on As cycling, which is necessary for maximizing biosorption of algae if utilized for bioremediation studies as well as in the wastewater treatment implementation approach in the environment.
Abstract This study exclusively focused on the potential application of an inexpensive and sustainable waste macro-algal biomass as an adsorbent for biosorption of copper ions from aqueous medium. After extraction of agar from brown macro-marine algae Gelidiella acerosa, the residual biomass without any further treatment was used as an adsorbent for the expulsion of copper from wastewater. Physicochemical parameters of biosorption like initial pH, initial concentration of Cu(II) solution and biosorbent dosage were optimized using response surface methodology. The maximum copper biosorption potential of 96.36% was observed at optimum conditions of pH of 5.31, initial concentration of 23.87 mg/l and biosorbent dosage of 0.41 g/l. Adopting FTIR and SEM techniques, the surface morphological features of biosorbent were studied. The pseudo-second-order kinetic model was found to be a proper approach to describe biosorption kinetics. All these results confirmed that spent G. acerosa could be considered as an efficient, eco-friendly and economic alternative for Cu(II) removal from aqueous solution.
The uptake of nickel [Ni(II)] by Paenibacillus sp., Methylobacterium sp., Paraburkholderia sp., and Pseudomonas sp. strains isolated from a boreal bog was studied using batch experiments. All strains removed Ni(II) from the solution and the uptake efficiency was affected by the nutrient source, incubation temperature, time, and pH. As highest Ni uptake (with a maximum Kd of 1890 L/kg DW) was recorded for the Pseudomonas sp. strains, these bacteria were used in the following protein expression (SDS-PAGE and MALDI-TOFF), transmission electron microscopy (TEM) and EDS experiments. In addition, Freundlich and Langmuir sorption isotherms were determined. In the Ni(II) treated cells, dense crystalline intra-cellular accumulations were observed in TEM examinations, which were identified as Ni accumulations using EDS. SDS-PAGE and MALDI-TOFF spectra of Ni(II) treated cells showed several changes in the protein profiles, which can indicate active accumulation of Ni in these bacteria. Concurrently, we observed Ni(II) uptake to follow Freundlich and Langmuir isotherms, suggesting straight cellular biosorption in addition to the intra-cellular accumulation. The role of cellular (cell membrane and cell wall) functional groups involved in Ni(II) binding were therefore studied using Fourier transformation infrared spectroscopy. These analyses supported the potential role of the alcoholic hydroxyl, carboxyl and amine groups in Ni(II) binding in these bacteria, therefore suggesting two different Ni(II) uptake mechanisms; (i) intra-cellular accumulation [possibly connected to detoxification of Ni(II)], and (ii) straight biosorption on cell membrane/wall functional groups.
Biosorption by algae is an effective process for the removal of heavy metals from the aqueous solutions. The present work deals with the biosorption of Cd(II) by Chlorella vulgaris in a batch system. The biosorption efficiency of Cd(II) removal was studied at different pH (3-8), initial metal concentrations (20-100 ppm), agitation time (5-120 min.), agitation speed (50-250 rpm), and biomass dosage (0.01-0.1 g/50 ml of metal solution). The optimum conditions for maximum biosorp-tion capacity for C. vulgaris were at pH 6, initial Cd(II) concentration 75 mg/l, biomass dosage 0.08 g/50 ml metal solution, temperature 25 °C, agitation speed 250 rpm, and agitation time 30 min. The cadmium removal efficiency of the raw and pretreated algal biomass was studied under the optimum conditions. The results showed that pretreatment with acetic acid gave 99.346% as compared with raw biomass. Different algal weights (0.2, 0.15, 0.1, 0.05, and 0.025 g) were immobilized with 10 ml of 4% calcium alginate. The results showed that the highest cadmium biosorption efficiency was 76.448% for 0.025 g as compared with the control. The biosorption mechanisms were examined by Fourier-transform infrared analysis and scanning electron microscopy for raw and pretreated algal biomasses before and after cadmium biosorption. It was found that hydroxyl, amide with hydrogen bond, and carbonyl stretching in carboxyl groups played an important role in biosorption. Article Highlights • Removal of heavy metals in aqueous solutions • Biosorption of Cd(II) by Chlorella vulgaris in a batch system • Immobilization of Chlorella vulgaris increased the biosorption capacity • Culture conditions and environmental conditions affected biosorption capacity
Biosorption is an effective way of extracting heavy metal ions from aqueous solutions of various compositions. The brown algae, Cystoseria indica, when treated with sodium chloride, demonstrates significant capacity to extract cadmium and nickel, simultaneously, from aqueous solutions. The batch system was running over wide ranges of initial metal ion concentrations (5–150 mg/L), pH (2–6), adsorbent mass (1–4 g/L), and contact times (20–300 min), at a temperature of 25 °C. The results obtained when applying the system in these conditions exhibit higher removal capacities for cadmium than nickel. The optimal conditions of the biosorption process were found as the adsorbent mass of 1 g/L, initial concentration of adsorbates of 100 mg/L and pH of 6. The equilibrium data obtained are better described by the extended-Freundlich isotherm for nickel and cadmium. The maximum biosorption of nickel and cadmium in binary-metal-component system were 18.17 and 55.34 mg/g, respectively. The kinetic data derived from these experiments were evaluated with pseudo-first-order, pseudo-second-order and intra-particle-diffusion kinetic models. Kinetic examination of the equilibrium data derived from these models suggest that the adsorption of nickel and cadmium both follow the intra-particle-diffusion kinetic model.
: Bioremediation is an environmentally-benign and cost-effective approach to removing arsenic from contaminated areas. A fungal strain hyper-tolerant to arsenic was isolated from soil from a mine site and used for the removal of arsenic. The isolated fungus was identified as Talaromyces sp., and its growth rate, arsenic tolerance, and removal rates were investigated for As(III) and As(V). Arsenic tolerance tests revealed that the fungus was highly resistant to arsenic, tolerating concentrations up to 1000 mg/L. Robust mycelial growth was observed in potato dextrose broth containing either As(III) or As(V), and there was no difference in growth between that in arsenic-free medium and medium amended with up to 300 mg/L of either arsenic species. The isolate showed relatively low growth rates at As(V) concentrations >500 mg/L, and almost no growth at As(III) concentrations >300 mg/L. Both arsenic species were effectively removed from aqueous medium (>70%) in tests of the biosorption of arsenic onto mycelial biomass. Surface modification of the biomass with Fe(III) (hydr)oxides significantly enhanced arsenic removal efficiency. The findings indicate that this soil fungal strain has promise for use in bioremediation strategies to remove arsenic from highly contaminated aqueous systems.
Heavy metals polluted soils have turned out to be a common environmental problem across the globe due to their toxic effects and accumulation through the food chain. Heavy metals have lethal effects on all forms of life. For instance, plants grown on heavy metal polluted soil show a reduction in growth and yields. A surge in anthropogenic activities and industrial operations has substantially increased the level of heavy metal pollution and release into the environment; hence, there is need to remediate these heavy metal pollutants. Biosorption is an efficient, economical, ecofriendly and convenient techniques of remediating heavy metal polluted soils. It is a widely accepted method that utilizes biomaterials such as natural biomass as biosorbents. The current study was based on the biosorption of copper, chromium, cadmium and nickel polluted soil using bacteria and fungi isolated from soil. Bacterial species isolated were Pseudomonas, Bacillus, Micrococcus, Escherichia, Streptococcus, Enterobacter and Staphylococcus while fungi isolated were Aspergillus niger, Penicillium notatum and Aspergillus flavus. The isolated bacteria were screened for potential to biosorb copper and chromium likewise fungi for cadmium and nickel. Biosorption rate was determined using atomic absorption spectrophotometry. Five milliliters each of a-day-old culture of the screened bacteria and fungi was inoculated into 45 ml of nutrient broth (bacteria) and potato dextrose broth (fungi) having concentrations of 5, 10, 15 and 20 ppm, respectively, of copper, chromium, cadmium and nickel. The conical flasks were incubated at a temperature of 37 °C and 28 °C ± 2 for bacteria and fungi, respectively, for a period of 35 days of inoculation. For the bacterial isolates, the highest biosorption rates of chromium (89.67%) and copper (90.89%) by Pseudomonas aeruginosa were observed at 20 ppm on day 21 and 15 ppm on day 14, respectively, while for the fungi isolates, P. notatum showed highest biosorption rate for cadmium at 10 ppm with 77.67%. Aspergillus niger showed highest biosorption rate for nickel with 81.07% after 28 days of incubation. The results of this study revealed the ability of Pseudomonas aeruginosa to biosorb copper and chromium and also A. niger and P. notatum to biosorb cadmium and nickel from the environment and can be developed for the biosorption of soils polluted with copper, chromium, cadmium and nickel.
Biological approaches are considered promising and eco‐friendly strategies to remediate Hg contamination in soil. This study investigated the potential of two ‘green’ additives, Hg‐volatilizing bacteria (Pseudomonas sp. DC‐B1 and Bacillus sp. DC‐B2) and sawdust biochar, and their combination to reduce Hg(II) phytoavailability in soil and the effect of the additives on the soil bacterial community. The results showed that the Hg(II) contents in soils and lettuce shoots and roots were all reduced with these additives, achieving more declines of 12.3–27.4%, 24.8–57.8% and 2.0–48.6%, respectively, within 56 days of incubation compared to the control with no additive. The combination of DC‐B2 and 4% biochar performed best in reducing Hg(II) contents in lettuce shoots, achieving a decrease of 57.8% compared with the control. Pyrosequencing analysis showed that the overall bacterial community compositions in the soil samples were similar under different treatments, despite the fact that the relative abundance of dominant genera altered with the additives, suggesting a relatively weak impact of the additives on the soil microbial ecosystem. The low relative abundances of Pseudomonas and Bacillus, close to the background levels, at the end of the experiment indicated a small biological disturbance of the local microbial niche by the exogenous bacteria.
Exchangeable lead (Pb) extracted by ammonium acetate from three independent incubation studies was assessed to understand the influence of feedstock, pyrolysis temperatures, and production conditions on Pb immobilization capacities of different biochars. Vegetable waste biochar, pine cone, wood bark, cocopeat, red pepper stalk, and palm kernel shell were used as feedstocks (food supply and agricultural wastes) to produce biochars at 200–650 °C with and without N2/CO2. Biochars were applied at 5 and 2.5% (w w−1) to a Pb contaminated (i.e., 1445 mg kg−1) agricultural soil collected near an old mine. Lead immobilization in biochar treated soils at the end of incubation period was normalized per gram of biochar applied. Biochar produced from vegetable waste at 500 °C showed the highest Pb immobilization (87%) and highest total exchangeable cations (13.5 cmol(+) kg−1) at the end of the 45 d incubation period. However, on the basis of Pb immobilization per gram of biochar, red pepper stalk biochar produced in CO2 at 650 °C was the best in Pb immobilization (0.09 mg kg−1 g−1 biochar) compared to the other biochars. The enhanced ability to immobilize Pb by biochar produced in CO2 could be due to the presence of siloxanes (SiOSi) on biochar surface. Pearson correlation analysis revealed that alkaline pH, ash%, and N% of biochars influence in Pb immobilization and exchangeable cation availability in soil. Biochar production atmosphere considerably change its properties that influence Pb immobilization. Further studies are needed on the modification of properties and Pb immobilization by biochars produced from various feedstocks in CO2. Keywords: CO2 pyrolysis, Soil stabilization, Metals/metalloids, Waste valorization/recycling, Black carbon, Engineered biochar
Addressing heavy metal pollution is one of the hot areas of environmental research. Despite natural existence, various anthropomorphic sources have contributed to an unusually high concentration of heavy metals in the environment. They are characterized by their long persistence in natural environment leading to serious health consequences in humans, animals, and plants even at very low concentrations (1 or 2 μg in some cases). Failure of strict regulations by government authorities is also to be blamed for heavy metal pollution. Several individual treatments, namely, physical, chemical, and biological are being implied to remove heavy metals from the environment. But, they all face challenges in terms of expensiveness and in-situ treatment failure. Hence, integrated processes are gaining popularity as it is reported to achieve the goal effectively in various environmental matrices and will overcome a major drawback of large scale implementation. Integrated processes are the combination of two different methods to achieve a synergistic and an effective effort to remove heavy metals. Most of the review articles published so far mainly focus on individual methods on specific heavy metal removal, that too from a particular environmental matrix only. To the best of our knowledge, this is the first review of this kind that summarizes on various integrated processes for heavy metal removal from all environmental matrices. In addition, we too have discussed on the advantages and disadvantages of each integrated process, with a special mention of the few methods that needs more research attention. To conclude, integrated processes are proved as a right remedial option which has been detaily discussed in the present review. However, more research focus on the process is needed to challenge the in situ operative conditions. We believe, this review on integrated processes will surely evoke a research thrust that could give rise to novel remediation projects for research community in the future.
This study was performed to investigate the effect of biochar manufactured from agriculture residues for the stabilization of lead, cadmium and chromium (Pb, Cd and Cr) in artificially contaminated soil. A surface loamy sand soil was spiked with Pb, Cd and Cr at 200, 400 and 600 mg kg ⁻¹ . Thereafter, the spiked soil was treated with biochar at different rates of 0.0, 1.0, 2.5, 5.0 and 10% (weight basis) and incubated for 30 days. The treated soil was cultivated with maize plant (Zea mays) lasting 30 days. Addition of biochar significantly increased the soil reaction (pH), organic matter (OM) and nutrient content of nitrogen, phosphorus and potassium (N, P and K). Moreover, the addition of biochar considerably decreased the solubility of Pb and Cd in terms of water soluble, exchangeable (extracted by ammonium nitrate), physiological based extraction test (PBET) and toxicity characteristics leaching procedure (TCLP) extracts. The highest reduction of expendable Pb and Cd were 28.68% and 85.14%, respectively. On the other hand, addition of biochar might facilitated Cr solubility through the transformation of Cr(III) into Cr(VI) due to increasing soil pH, and increased its uptake by maize plant. The phytotoxicity test revealed that biochar significantly increased maize biomass (shoots and roots), especially with applications of 5% and 10% treatments. Our findings provide evidence that biochar application decreased Pb and Cd toxicity by immobilizing them into more stable forms and improved soil quality. However, attention should be paid when treating the soil that is co-contaminated by Cr with biochar.
The present study investigated the effect of contact time, the initial concentration of metal ions, and the biomass dose on the Cu(II) biosorption from an aqueous solution using dead biomass of filamentous fungus Penicillium ochrochloron, which was isolated at the Sossego mine, a copper-contaminated site located in Canaã dos Carajás city, Brazil. The Cu(II) biosorption started rapidly and increased gradually until the equilibrium was reached at 20 min. The Cu(II) uptake decreased as the initial Cu(II) concentration increased, reaching the saturation at 200 mg/L. The Cu(II) biosorption was considerably higher using 0.2 g than 0.5 g of the biomass in 50 mL of solution. The average biosorption capacity of Cu(II) was 7.53 mg/g and the maximum Cu(II) removal 75.0%. The Freundlich and Langmuir isotherm models adequately described the adsorption data. Our results evidenced that the dead biomass of P. ochrochloron has a great potential as a biosorbent to remove copper from an aqueous solution. Therefore, it could be explored for the development of the environmental recovery process.
Certain rhizobacteria can be applied to remove arsenic in the environment through bioremediation or phytoremediation. This study determines the minimum inhibitory concentration (MIC) of arsenic on identified rhizobacteria that were isolated from the roots of Ludwigia octovalvis (Jacq.) Raven. The arsenic biosorption capability of the was also analyzed. Among the 10 isolated rhizobacteria, five were Gram-positive (Arthrobacter globiformis, Bacillus megaterium, Bacillus cereus, Bacillus pumilus, and Staphylococcus lentus), and five were Gram-negative (Enterobacter asburiae, Sphingomonas paucimobilis, Pantoea spp., Rhizobium rhizogenes, and Rhizobium radiobacter). R. radiobacter showed the highest MIC of >1,500 mg/L of arsenic. All the rhizobacteria were capable of absorbing arsenic, and S. paucimobilis showed the highest arsenic biosorption capability (146.4 ± 23.4 mg/g dry cell weight). Kinetic rate analysis showed that B. cereus followed the pore diffusion model (R2 = 0.86), E. asburiae followed the pseudo-first-order kinetic model (R2 = 0.99), and R. rhizogenes followed the pseudo-second-order kinetic model (R2 = 0.93). The identified rhizobacteria differ in their mechanism of arsenic biosorption, arsenic biosorption capability, and kinetic models in arsenic biosorption.
The biosorption of two Arsenic (As) species [As (III) and As (V)] from aqueous solution onto activated biochar derived from Cassia fistula, belonging to Fabaceae family was studied. SEM/EDX characterization of the adsorbent showed an irregular, porous, and heterogeneous surface morphology with calcium and iron available for As binding. FTIR also showed the presence of groups responsible for As adsorption. Batch adsorption experiments were conducted to determine the optimum conditions for As adsorption to the biomass with optimum adsorbent dose, ambient temperature, initial concentration
of As, pH, and stirring rate. Under optimized conditions, the maximum removal percentage was 78.1% [uptake capacity (qe) = 0.78 mg/g] for As (III) and 84.8% [uptake capacity (qe) = 0.42 mg/g] for As (V). The Freundlich isotherm model, characteristic of multilayer binding, fit the data best with R2 values of 0.92 for As (III) and 0.96 for As (V). Fitting of the data to the Dubinin–Radushkevich model indicated physisorption, while the kinetics study suggested a pseudo-second-order reaction. Thermodynamic parameters indicated adsorption was spontaneous. In aqueous solutions, phosphate hindered As removal
more than the any other ions. Regeneration studies showed a 23.0% and 21.1% recovery for arsenite and arsenate, respectively, indicating limited leaching under both acidic and alkaline conditions. The absorptive capacity of C. fistula biomass for arsenic removal was compared with a number of other reported biosorbents and was found to be considerably efficient.
Lead (Pb2+) is among the most toxic heavy metals even in low concentration and cause toxicity to human’s health and other forms of life. It is released into the environment through different industrial activities. The biosorption of Pb2+ from aqueous solutions by biomass of commonly available, marine alga Gelidium amansii was studied. The effects of different variables on Pb2+ removal were estimated by a two-level Plackett–Burman factorial design to determine the most significant variables affecting Pb2+ removal % from aqueous solutions. Initial pH, Pb2+ concentration and temperature were the most significant factors affecting Pb2+ removal chosen for further optimization using rotatable central composite design. The maximum removal percentage (100%) of Pb2+ from aqueous solution by Gelidium amansii biomass was found under the optimum conditions: initial Pb2+ concentration of 200 mg/L, temperature 45°C, pH 4.5, Gelidium amansii biomass of 1 g/L and contact time of 60 minutes at static condition. FTIR analysis of algal biomass revealed the presence of carbonyl, methylene, phosphate, carbonate and phenolic groups, which are involved in the Pb2+ ions biosorption process. SEM analysis demonstrates the ability of Gelidium amansii biomass to adsorb and removes Pb2+ from aqueous solution. EDS analysis shows the additional optical absorption peak corresponding to the Pb2+ which confirms the involvement of Gelidium amansii biomass in the adsorption of Pb2+ ions from aqueous solution. Immobilized Gelidium amansii biomass was effective in Pb2+ removal (100%) from aqueous solution at an initial concentration of 200 mg/L for 3 h. In conclusion, it is demonstrated that the red marine alga Gelidium amansii biomass is a promising, efficient, ecofriendly, cost-effective and biodegradable biosorbent for the removal of Pb2+ from the environment and wastewater effluents.
The aim of this study was to isolate arsenic-resistant bacteria and to further exploit it for remediation purposes. In the present study, we have isolated arsenic-resistant strain from ground water of Pakistan AT-01. The strain was cultivated at 37 °C in Luria Bertani broth supplemented with different concentrations of arsenate and arsenite. The minimum inhibitory concentration of arsenic against the bacterial isolate was 7 g/L (7000 mg/L) for arsenate and 1.4 g/L (1400 mg/L) for arsenite salt. The bacterial isolate was also characterized both on molecular and biochemical basis. The isolated strain belonged to the Pseudomonas aeruginosa. The high resistance against arsenic offered by the bacteria was exploited further for bioremediation purposes. The bacterial biomass generated from AT-01 strain was able to efficiently remove arsenic with 98% efficiency. Arsenic contamination of ground water is a widespread worldwide problem. The present study shows the potential of high arsenic-resistant bacteria for efficient arsenic removal.
Cadmium (Cd)-contaminated rice (Oryza sativa) in Southern China is a great threat to food security, and the paddy soil remediation is urgently needed to reduce Cd accumulation in rice. Application of biochar could effectively immobilize soil Cd and reduce Cd uptake by rice. Fields that were applied with soil treatments including control and 15 and 30 t ha⁻¹ each hickory nut shell-derived biochar (KC) or maize straw-derived biochar (MC), and grown with two rice varieties (hybrid rice and late japonica rice) were selected for this study. The long-term effect of biochars on decreasing Cd bioavailability in paddy soils was evaluated. The results showed when MC was applied at 15 t ha⁻¹, DTPA-Cd (soil cadmium extracted by diethylenetriamine pentaacetic acid) was reduced by 20.0 and 34.5% in Field A (slightly Cd pollution) and B (moderately Cd pollution), respectively. In Field B, soil DTPA-Cd concentrations with application of 30 t ha⁻¹ biochars were all lower than that of 15 t ha⁻¹ biochar, but there were no significant differences between the two types of biochars. Cd concentration in rice grains and straws of hybrid rice are two times more than those of late japonica rice. Cd bio-concentration factor both of grains and straw was significantly increased by biochar application, which in Field A was higher than that in Field B. Our results suggest that biochars reduce Cd accumulation in rice grains by immobilizing soil Cd. KC has a higher potential in lowering Cd bioavailability than MC. Hybrid rice should be prohibited to cultivate in these areas.
Biochar is mainly used as a soil amendment and for carbon sequestration; while other applications such as environmental remediation may be equally important. Recently, different engineering methods have been developed and used to expand biochar's applications. A systematic literature review on the linkages between the production methods and applications of engineered biochar, therefore, is in critical need. In this work, the production and application prospects of engineered biochar are reviewed comprehensively based on the current literature. The application values and effect of engineered biochar in energy, environment, and agriculture are also expounded. Different from previous ones, this review is more focused on the unique properties and functions of various types of engineered biochars to explain their potential application, particularly environmental application. It not only summarizes recent advances in engineered biochar technology but also offers insights on new directions for development and research of engineered biochar in the future.
Biochar has been widely studied for its ability to reduce plant uptake of heavy metals by lowering metal bioavailabilities through adsorption and pH-driven fixation reactions. However, the long-term effect of biochar on heavy metal bioavailabilities in alkaline soils under natural redox condition is rarely studied. Here, we report a study examining the effects of biochar on bioavailability and partitioning of cadmium (Cd) and lead (Pb) among different soil fractions over 3 years in a field study with wheat (Triticum aestivum L.). Plots were established on two similar soils having low and high levels of contamination, both of which were amended in the first year with wheat straw biochar at 0, 20, and 40 t ha⁻¹. Precipitation patterns varied greatly over the study period, with 2014 having record drought, which was followed by 2 years having extreme flooding events. Results showed a significant increase in grain yield and reductions in Cd and Pb concentrations in wheat grain in the biochar-amended soils in 2014. In contrast, bioavailable (exchangeable) heavy metal concentrations and plant uptake of Cd and Pb were significantly higher in the subsequent very wet years in 2015 and 2016, where the effects of biochar were much more variable and had an overall lesser effect on reducing heavy metal uptake. The results suggest that fluctuations in soil pH and redox caused by periodic drought and flood cycles strongly drive metal cycling through mobilization and immobilization of metals associated with different mineral phases. Under these conditions, biochar may have reduced efficacy for reducing heavy metal uptake in wheat.
Two kinds of biochars, one derived from corn straw and one from pig manure, were studied as carriers of a mutant genotype from Bacillus subtilis (B38) for heavy metal contaminated soil remediation. After amendment with biochar, the heavy metal bioavailability decreased. Moreover, the heavy metal immobilization ability of the biochar was enhanced by combining it with B38. The simultaneous application of B38 and pig manure-derived biochar exhibited a superior effect on the promotion of plant growth and the immobilization of heavy metals in soil. The plant biomass increased by 37.9% and heavy metal concentrations in the edible part of lettuce decreased by 69.9-96.1%. The polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) profiles revealed that pig manure-derived biochar could enhance the proliferation of both exotic B38 and native microbes. These results suggest that B38 carried by pig manure-derived biochar may be a promising candidate for the remediation of soils contaminated by multiple heavy metals.
Nano zero valent iron/Ni bimetal materials (nZVI/Ni) were prepared by borohydride reduction method to remediate toxic Cr(Ⅵ) contaminated in soil leachate. nZVI/Ni was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). Different factors including pH value of soil leachate, reaction time, temperature, humic acid and coexisting anions (SO4²⁻, NO3⁻, HCO3⁻, CO3²⁻) were studied to analyze the reduction rate. Results showed that the reduction rate of Cr(Ⅵ) could reach 99.84% under the condition of pH of 5 and temperature of 303 K. pH values and temperature of soil leachate had a significant effect on the reduction efficiency, while humic acid had inhibition effect for the reduction reaction. SO4²⁻, HCO3⁻ and CO3²⁻ had inhibition effect for reduction rate, while NO3⁻ barely influenced the reduction process of nZVI/Ni. Moreover, Langumir-Hinshelwood first order kinetic model was studied and could describe the reduction process well. The thermodynamic studies indicated that the reaction process was endothermic and spontaneous. Activation energy was 143.80 kJ mol⁻¹, showing that the reaction occurred easily. Therefore, the study provides an idea for nZVI/Ni further research and practical application of nZVI/Ni in soil remediation.
The major frequent contaminants in soil are heavy metals which may be responsible for detrimental health effects. The remediation of heavy metals in contaminated soils is considered as one of the most complicated tasks. Among different technologies, in situ immobilization of metals has received a great deal of attention and turned out to be a promising solution for soil remediation. In this review, remediation methods for removal of heavy metals in soil are explored with an emphasis on the in situ immobilization technique of metal(loid)s. Besides, the immobilization technique in contaminated soils is evaluated through the manipulation of the bioavailability of heavy metals using a range of soil amendment conditions. This technique is expected to efficiently alleviate the risk of groundwater contamination, plant uptake, and exposure to other living organisms. The efficacy of several amendments (e.g., red mud, biochar, phosphate rock) has been examined to emphasize the need for the simultaneous measurement of leaching and the phytoavailability of heavy metals. In addition, some amendments that are used in this technique are inexpensive and readily available in large quantities because they have been derived from bio-products or industrial by-products (e.g., biochar, red mud, and steel slag). Among different amendments, iron-rich compounds and biochars show high efficiency to remediate multi-metal contaminated soils. Thereupon, immobilization technique can be considered a preferable option as it is inexpensive and easily applicable to large quantities of contaminants derived from various sources.
Graphical Abstract
Heavy metal pollution of soil is a global environmental issue that is of great concern to the public. Immobilization is a common method for the remediation of soil contaminated by heavy metalsBiomass-based carbon materials are gaining widespread attention in the field of remediation of heavy metal contaminated soil due to its wide sources, low price, environmental friendliness and high remediation efficiency. However, current studies on biomass-derived carbon materials mainly focus on pyrochar obtained by pyrolysis. There are few studies on carbon materials obtained by hydrothermal method, and the remediation mechanism for heavy metal contaminated soil is limited. This article focuses on the remediation mechanism and influencing factors of biomass-based carbon materials in remediation of heavy metal contaminated soil. VOSviewer software is used to provide visual analysis of the studies on biomass-derived carbon materials in remediation of heavy metal contaminated soil, providing reference for scientific and technological researchers.
The application of biochar in the remediation of heavy metal contaminated soil has received increasing global attention during the past decade. Although there has been some review work on the mechanism of heavy metals stabilization by biochar, the effects and mechanisms of interaction between biochar and functional microbes such as heavy metal tolerant, adsorption and transformation microbial strains remains unclear. In this paper, maize biochar and a heavy metal-tolerant strain Pseudomonas sp. NT-2 were selected to investigate the dynamic effects and potential mechanisms of biochar and bacteria loaded biochar on the stabilization of Cd and Cu mixed contaminated soil by a 75-day pot experiment. The results showed that, compared to the single biochar amendment, the application of biochar inoculated with NT-2 strain at the rate of 5% significantly increased the soil pH at the initial stage of incubation, and followed by a slight decline to a neutral-alkaline range during the reaction. The addition of NT-2 loaded biochar could also significantly increase the proportion of residual fraction of Cd and Cu, thus reduce the proportion of exchangeable and carbonate bound species in the soil, which lead to the decreasing of plant and human bioavailability of the metal in the soil indicated by DTPA and simulated human gastric solution extraction (UBM), respectively. Finally, the application of bacterial loaded biochar also markedly enhanced soil urease and catalase activities during the later stage of the incubation, and improved soil microbial community at the end of incubation, which indicates a recovery of soil function after the metal stabilization. The research results may provide some new insights into the development of functional materials and technologies for the green and sustainable remediation of heavy metal contaminated soil by the combination of biochar and functional microorganisms.
Despite considerable research
about biogeochemical behavior
of trace elements (TEs) in soil-
plant-human systems, there is still
a gap of knowledge regarding
dose–response relationship, espe-
cially for low-applied doses. Trace
elements such as mercury, cad-
mium, antimony and others are
highly toxic, without any known
essential function in plants.
Nevertheless, recent toxicology
and risk assessment studies revealed TE-induced hormesis in plants, i.e. stimulation in plant growth at low-doses while suppression at high-doses. This is the first review critic- ally reviewing the TE-induced phytohormetic. The review compares hormetic effects for 366 observations from various research articles among different (i) toxic TEs, (ii) plant species, (iii) plant response parameters (end points), and (iv) exposure durations. It was observed that various toxic TEs, especially Cd, induce hormesis in plants. The mean value of Maximum Stimulatory Response (MAX) was 27% higher compared to the con- trol response, with a range of 0.71 to 1122%. This review critically highlights the TE- induced phytohormesis by discussing possible mechanisms such as the (i) activation of plant tolerance mechanisms after TE-induced overproduction of reactive oxygen species (ROS), and (ii) interplay between phytohormones and TE-mediated ROS production towards plant growth.
Microbial adsorption of heavy metals has been attracted more interest in the recent years. However, there are very few studies in investigating the biosorption of heavy metals by Shewanella putrefaciens, which is a metal reducing bacterium. Firstly, the effects of contact time, pH value, temperature, biomass dosage and initial cadmium concentration on the cadmium adsorption by Shewanella putrefaciens were studied by single factor experiments. Then, the response surface methodology (RSM) based on Box-Behnken design was used to optimize the cadmium adsorption by Shewanella putrefaciens. The results showed that the empirical model was suitable for experimental data, and the maximum cadmium removal efficiency by Shewanella putrefaciens was 86.54% under the optimum conditions of contact time 4.0 days, pH value 5, initial cadmium concentration of 20 mg/L, which was further verified by experiments. In addition, scanning electron microscope - Energy Dispersive Spectrometer (SEM-EDS) analysis showed that the bacteria were seriously deformed, and a “bamboo” shape was observed on the surface which consisted of cadmium according to the EDS analysis. Fourier transform infrared spectroscopy (FT-IR) analysis was used to evaluate the possible functional groups involving in interaction between cells and metal ions. The results showed that the distribution of cadmium on the cell surface was related to the carboxyl, amide, hydroxyl and phosphoric acid groups of Shewanella putrefaciens. These studies can provide a comprehensive understanding of the process and mechanism of microbial removal of heavy metals, and theoretical support for the follow-up practice of using biological adsorbents to remediate heavy metal contaminated soil.
Zinc biosorption and bioaccumulation by a novel extremely Zn tolerant Streptomyces K11 strain isolated from highly alkaline environment were examined. Temperature, similarly as biosorbent preparation, has negligible effect on the biosorption capacity but very strong effect on the process kinetics. Initial adsorption rate increased almost 10 times with the temperature increase from 10 to 50 °C and it was 30 times higher when non-dried biomass was used. The biosorption study revealed that the process was mainly chemically controlled, however at lower temperature intra-particle diffusion played significant role in the zinc biosorption. The experimental data fitted the Langmuir isotherm model with the maximum biosorption capacity 0.75 mmol g⁻¹. The results of bioaccumulation onto a living biomass of Streptomyces K11 indicated very high bioaccumulation capacity of 4.4 mmol g⁻¹. Zinc extracellular uptake (43%) slightly exceeded the intracellular accumulation (36%). High zinc bioaccumulation capacity was obviously related to extremely high zinc tolerance of Streptomyces K11.
This study presents a multifaceted approach of Zn adsorption onto dry Fucus vesiculosus originating from the Irish Sea. Metal chemistry as well as algae surface charge properties were characterized before adsorption. Zn adsorption tests were run as function of: pH, algae concentration and metal source. A comparison with Co, Cd, and Cu adsorption – in mono-ion solutions was also performed. Adsorption kinetics, fitted with pseudo-first order (PFO) and pseudo-second order (PSO) kinetic model, allowed the uptake parameters to be found and a comparison of kinetic rates. Synchrotron X-Ray-Florescence and X-Ray Absorption Spectroscopy measurements of Zn on algae after exposure permitted the extraction of direct information about Zn spatial distribution and bonding environment. The results showed that the carboxylic groups are the ones involved in the heterogeneously distributed Zn adsorption at low pH, Zn being coordinated with 5–6 O at bond distances varying from 1.98 to 2.03 Å - as in Zn alginate. Synchrotron results provide confirmation that, relative to Zn, alginate is one of the main algae components responsible for metal binding.
The present study aimed to analyze simultaneous biosorption of Cd⁺² and Ni⁺² by living Phanerochaete chrysosporium as low-cost and eco-friendly biosorbent following optimization by applying a central composite design. The effect of operating parameters such as solution pH (4.0–8.0), temperature (20–40 °C), contact time (3–15 h), initial Cd⁺² and Ni⁺² concentrations (15–35, 5–25 mg L⁻¹, respectively) was evaluated by response surface methodology (RSM) for optimizing biosorption process. The Cd⁺² and Ni⁺² ions at 25 and 16 mg L⁻¹ were accumulated in P. chrysosporium with the efficiency of 96.23% and 89.48%, respectively, at pH of 6 and 36 °C after around 9 h under well mixing. The equilibrium data were fitted well with Langmuir isotherm model with maximum biosorption capacity of 71.43 and 46.50 mg g⁻¹ for Cd⁺² and Ni⁺², respectively. In addition, the pseudo-second order kinetic model could describe the kinetic data adequately. Further, possible interaction pathway among metals and P. chrysosporium functional groups were studied by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) techniques were applied for morphology investigation and semi elemental analysis.
Soil contamination by heavy metals and metalloids has been a major concern to human health and environmental quality. While many remediation technologies have been tested at the bench scale, there have been only limited reports at the field scale. This paper aimed to provide a comprehensive overview on the field applications of various soil remediation technologies performed over the last decade or so. Under the general categories of physical, chemical, and biological approaches, ten remediation techniques were critically reviewed. The technical feasibility and economic effectiveness were evaluated, and the pros and cons were appraised. In addition, attention was placed to the environmental impacts of the remediation practices and long-term stability of the contaminants, which should be taken into account in the establishment of remediation goals and environmental criteria. Moreover, key knowledge gaps and practical challenges are identified.
The safe disposal and utilisation of sewage sludge can be challenging because of the potential environmental risks posed by heavy metals in the sludge. Conversion of sewage sludge and agriculture biomass into biochars that can be used to improve or remediate contaminated soils is a promising solution to this problem. In this study, biochars were produced via co-pyrolysis of sewage sludge and cotton stalk (1:1, w/w) at temperatures ranging from 300 to 600 °C. Then, the potential environmental risks of heavy metals and properties of the biochars were investigated. The addition of cotton stalk promoted the migration and transformation of heavy metals from bioavailable to stable fractions, which significantly reduced the potential environmental risks of heavy metals in biochars. Moreover, compared with biochars obtained via pyrolysis of sewage sludge alone, the pH values, C contents, and adsorption capacities of biochars increased, while the yields, ash contents, specific surface areas and molar H/C ratios decreased. In summary, co-pyrolysis of sewage sludge and cotton stalk is a feasible method for alleviating the potential environmental risks of heavy metals in biochars used to treat soils.
Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO 2 capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.
Biochar is a solid by-product of thermochemical conversion of biomass to bio-oil and syngas. It has a carbonaceous skeleton, a small amount of heteroatom functional groups, mineral matter, and water. Biochar’s unique physicochemical structures lead to many valuable properties of important technological applications, including its sorption capacity. Indeed, biochar’s wide range of applications include carbon sequestration, reduction in greenhouse gas emissions, waste management, renewable energy generation, soil amendment, and environmental remediation. Aside from these applications, new scientific insights and technological concepts have continued to emerge in the last decade. Consequently, a systematic update of current knowledge regarding the complex nature of biochar, the scientific and technological impacts, and operational costs of different activation strategies are highly desirable for transforming biochar applications into industrial scales. This communication presents a comprehensive review of physical activation/modification strategies and their effects on the physicochemical properties of biochar and its applications in environment-related fields. Physical activation applied to the activation of biochar is discussed under three different categories: I) gaseous modification by steam, carbon dioxide, air, or ozone; II) thermal modification by conventional heating and microwave irradiation; and III) recently developed modification methods using ultrasound waves, plasma, and electrochemical methods. The activation results are discussed in terms of different physicochemical properties of biochar, such as surface area; micropore, mesopore, and total pore volume; surface functionality; burn-off; ash content; organic compound content; polarity; and aromaticity index. Due to the rapid increase in the application of biochar as adsorbents, the synergistic and antagonistic effects of activation processes on the desired application are also covered.
Organic and inorganic pollutants well known to interfere with the major functions of the endocrine system co-occur widely in contaminated ecosystems. The aim of the study was to evaluate the ability of Umbelopsis isabellina fungus to simultaneously remove and detoxify multiple environmentally significant endocrine disruptors: the heavy metals Cd(II), Zn(II), Mn(II), Pb(II) and Ni(II) and the phenolic xenobiotics nonylphenol (t-NP), 4-cumylphenol (CP) and 4-tert-octylphenol (4-t-OP). The effects of the metals on fungal growth and efficiency of single-metal uptake were also investigated. U. isabellina exhibited considerable tolerance to Zn(II), Mn(II), Pb(II) and Ni(II), with IC50/24 values ranging from 5.08 for Ni(II) to 13.1 mM for Zn(II). In the presence of CP, the maximum efficiency of Pb(II) removal increased 25% relative to that of the control. Supplementation with Mn(II) or Zn(II) enhanced the 4-t-OP degradation by 18 or 9%, respectively, after 6 h of cultivation. Ecotoxicological assays monitoring bioindicators from different aquatic ecosystems revealed detoxification coinciding with the removal of metals and organic xenobiotics from binary mixtures. This work indicates the potential of a single microorganism, U. isabellina, to remove both heavy metals and organic xenobiotics from co-contaminated sites, making it a suitable candidate for the development of bioremediation strategies.
The bioavailability of heavy metals in soils is closely related to their chemical fractions. In this study, four kinds（made from the common wastes of urban sludge and maize, cotton, and wheat straws）and two levels of biochar were added to soil contaminated with Cd and Pb to investigate their effects on the chemical fractions of Cd and Pb and to further analyze the immobilization and remediation of heavy metals in soil. The results showed that the physical and chemical properties of the soil were changed by biochar application and the pH, CEC, and SOM were significantly improved, especially with the 4% application treatments, with increases of 2.7%~11.6%, 12.7%~54.3%, and 252.0%~594.8%, respectively. Overall, adding the four kinds of biochar reduced the weak-acid-extractable and reducible fractions, whereas the oxidation and residue fractions increased. Regarding the immobilizing effect of soil Cd pollution, the cotton straw biochar showed the best passivation, followed by corn straw, wheat straw, and sludge biochar. When the cotton straw biochar was added at a rate of 4%, the weak-acid-extractable and reducible fractions of Cd decreased by 5.2% and 25.5%, respectively, and the oxidation and residue fractions increased by 177.8% and 166.7%, respectively. Similarly, adding the biochars showed passivation effects at different levels of the soil Pb pollution. Among the four kinds of biochars, the sequence of immobilizing effect was corn straw跃wheat straw跃cotton straw跃sludge. Correlation analysis showed that the changes in soil physical and chemical properties were likely to be important factors that induced the changes in the heavy metal forms of the soil. The results implicated that applying biochar can effectively change the chemical fractions of heavy metals in soil and reduce bioavailability, thus can be used as a solution to soil heavy metal pollution. © 2018 Editorial Board of Journal of Agro-Environment Science. All rights reserved.
Soil heavy metal pollution now is a major environmental concern in China particularly in some rapidly developing areas with intensified agricultural practices. High-spatial-resolution sampling (1664 surface (0–20 cm) and 416 deep (150–200 cm) soil samples) was undertaken in four typical agricultural Counties of Municipality Chongqing (SW China) and consequently eight priority heavy metals (HMs; As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) and other elements were measured. Classic and advanced multivariate statistics and multi-linear regression with factor analysis (FA-MLR) receptor modeling were applied for characterization and sources apportionment of HMs in soils. There was notably spatial variability in eight priority HMs with the mean concentrations decreasing as follows: Zn > Cr > Ni > Pb > Cu > As > Cd > Hg. Soil contamination was enhanced by As, Cd, Cr, while obvious enrichment of Cd and Hg in surface soils in comparison with deep soils should be noted. We revealed dominant anthropogenic contributions (64%–90%) of metal - bearing industrial emission, fuel consumption and agriculture to certain HMs, while the abundant elements of Si, Al and Fe were natural in origin. Our study will be helpful for improving soil environment and strengthening the capacity of multivariate statistic techniques and models in soil pollution research.
Globally there are over 20millionha of land contaminated by the heavy metal(loid)s As, Cd, Cr, Hg, Pb, Co, Cu, Ni, Zn, and Se, with the present soil concentrations higher than the geo-baseline or regulatory levels. In-situ and ex-situ remediation techniques have been developed to rectify the heavy metal-contaminated sites, including surface capping, encapsulation, landfilling, soil flushing, soil washing, electrokinetic extraction, stabilization, solidification, vitrification, phytoremediation, and bioremediation. These remediation techniques employ containment, extraction/removal, and immobilization mechanisms to reduce the contamination effects through physical, chemical, biological, electrical, and thermal remedy processes. These techniques demonstrate specific advantages, disadvantages, and applicability. In general, in-situ soil remediation is more cost-effective than ex-situ treatment, and contaminant removal/extraction is more favorable than immobilization and containment. Among the available soil remediation techniques, electrokinetic extraction, chemical stabilization, and phytoremediation are at the development stage, while the others have been practiced at full, field scales. Comprehensive assessment indicates that chemical stabilization serves as a temporary soil remediation technique, phytoremediation needs improvement in efficiency, surface capping and landfilling are applicable to small, serious-contamination sites, while solidification and vitrification are the last remediation option. The cost and duration of soil remediation are technique-dependent and site-specific, up to $500ton-1soil (or $1500m-3soil or $100m-2land) and 15years. Treatability studies are crucial to selecting feasible techniques for a soil remediation project, with considerations of the type and degree of contamination, remediation goals, site characteristics, cost effectiveness, implementation time, and public acceptability.
In this study, a fungal isolate was isolated from avocado fruit collected from a market in Makkah city, Saudi Arabia, and identified as Neopestalotiopsis clavispora ASU1. The biomass of Neopestalotiopsis clavispora ASU1 was used as a natural bio-sorbent for removal of Cd(II) and Zn(II) from aqueous solutions. Characterization of fungal biomass was performed using Fourier transform infrared spectroscopy, X-ray Diffractometer, and BET surface area. Different factors on Cd(II) and Zn(II) biosorption were studied to evaluate the maximum conditions for metals biosorption. The (qmax) for Cd(II) and Zn (II) by N. clavispora ASU1 calculated from the Langmuir adsorption isotherm was 185±0.25 and 153±0.18 mg/g, respectively. Based on r², the equilibrium biosorption isotherms fitted well with Langmuir model than Freundlich isotherm. The adsorption kinetics was studied, and the biosorption followed to the pseudo-second-order model. Thus, the currunt study indicated the possibility of N. clavispora ASU1 biomass for the removal of heavy metals from aqueous solutions.
Bioaccumulation factors for heavy metals (Cd, Zn, Cu, and Pb) were examined for selected earthworm species (Metaphire californica, Amynthas homochaetus, Amynthas pecteniferus, and Amynthas heterochaetus) that inhabit metal-polluted soils in a subtropical area (Hunan Province) of South China. The earthworms had high plasticity in inhabiting in situ contaminated areas and showed high uptake of the heavy metals and capability for their accumulation in the tissues. The bioaccumulation factor (BAF) were greatest for cadmium and ranked as follows: Cd (10.6–18.8) >> Zn (1.15–1.75) > Cu (1.01–1.35) > Pb (0.56–0.95). Earthworm species with the similar BAF of heavy metals (p > 0.05) belong to the same ecological group. Within individual groups, Cd, Cu, Zn, Cu, and Pb concentrations in earthworms are consistently predicted by total and extractable fraction (DTPA-extractable) in soil. Our results provide insights into the ecological relationships and variations in the uptake and accumulation of heavy metals in different earthworm species in contaminated soils in China.
Batch absorption experiments were carried out in order to examine the effect of various parameters such as pH, contact time, biomass concentration, and initial metal ion concentration. Absorption process was strongly dependent on the pH value and the initial metal concentration. The equilibrium absorption capacity varied with the concentration of metal oxide nanoparticles and maximum removal efficiency was observed at pH 3.5 in both the materials. Equilibrium experimental data were tested using the most common isotherms and the results are best fitted by Langmuir model for Fe2O3 and Freundlich model for ZnO. Theoretical absorption capacities for metal oxide nanoparticles were 70% and 80% respectively for both Fe2O3 and ZnO. Absorption kinetics were fitted by models including pseudo-first-order and pseudo-second-order models and the results demonstrated that pseudo-second-order kinetic model best describes the biosorption of metal oxide nanoparticles from aqueous solutions. Characterization of the biomass was done using FTIR, SEM along with EDX. The functional group of amino, carboxyl, phenolic hydroxyl, sulphonic group and C-O, -NH stretch showed a shift in the bands which might have involved in absorption. © 2018, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.
Nickel accumulation and nickel effects on cellular growth, respiration, photosynthesis, ascorbate peroxidase (APX) activity, and levels of thiols, histidine and phosphate-molecules were determined in Euglena gracilis. Cells incubated with 0.5-1mM NiCl2 showed impairment of O2 consumption, photosynthesis, Chl a+b content and APX activity whereas cellular integrity and viability were unaltered. Nickel accumulation was depressed by Mg(2+) and Cu(2+), while Ca(2+), Co(2+), Mn(2+) and Zn(2+) were innocuous. The growth half-inhibitory concentrations for Ni(2+) in the culture medium supplemented with 2 or 0.2mM Mg(2+) were 0.43 or 0.03mM Ni(2+), respectively. Maximal nickel accumulation (1362mg nickel/Kg DW) was achieved in cells exposed to 1mM Ni(2+) for 24h in the absence of Mg(2+) and Cu(2+); accumulated nickel was partially released after 72h. GSH polymers content increased or remained unchanged in cells exposed to 0.05-1mM Ni(2+); however, GSH, cysteine, γ-glutamylcysteine, and phosphate-molecules all decreased after 72h. Histidine content increased in cells stressed with 0.05 and 0.5mM Ni(2+) for 24h but not at longer times. It was concluded that E. gracilis can accumulate high nickel levels depending on the external Mg(2+) and Cu(2+) concentrations, in a process in which thiols, histidine and phosphate-molecules have a moderate contribution.
Biochar has been widely studied for remediation of heavy metal polluted soil. In this study, biochar made from rice straw under 500℃ was added to Pb-Cd contaminated soil for 30 days, and then fractionations of heavy metals in soils were measured. Results showed that after adding biochar, the pH value of the yellow brown soil rose, and the contents of weak acid extractable, reducible and oxidizable Pb reduced, while the residual fraction Pb significantly increased. The weak acid extractable Cd decreased significantly in high level Cd soils in comparison to no biochar treatment, whereas the content of oxidizable Cd increased and the residual fraction Cd had no significant changes. These indicated that the application of biochar may transfer the weak acid extractable Cd to oxidizable Cd, and decrease their potential risk in soils. There was significant interaction between Pb and Cd in Pb-Cd contaminated soils, and the biochar application weakened the interaction impact on the content of the weak acid extractable Pb.
