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FTIR (a) and XPS (b) spectra before and after Cd²⁺ adsorption by CS@BC. The high-resolution spectra of O 1s (c) and C 1s (d) before and after Cd²⁺ adsorption.
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In this study, by using coconut shell and chitosan (CS) as raw materials, mesoporous chitosan@coconut shell-derived biochar composites (CS@BC) were prepared and were used for Cd²⁺ removal from aqueous solutions. The tests of SEM, BET, XRD, FTIR, and XPS were used to identify the adsorbent structure and adsorption mechanisms. Batch adsorption experi...
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Citations
... Additionally, changed in the peak areas and binding energies corresponding to C = C/C-H and C = O after Bi adsorption suggested the occurrence of Bi-π interactions between Bi and the aromatic structures in OP-BC (Wu et al., 2023;Yang et al., 2022). Significant changes in the peak areas and binding energies for C-O and -OH also occurred, indicating that oxygen-containing functional groups, such as -COOH and -OH, reacted with Bi (Mo et al., 2023;Pan et al., 2022). ...
The dissemination of bismuth (Bi) into the environment has become a significant concern due to its wide application. The low-cost orange peel was used as a bio-sorbent to remove Bi from water. Influence of pH (4 ~ 12), biochar dosage (5 ~ 12.5 g L–1), temperature (25 ~ 55 °C), and coexisting ions (Mg²⁺ and Zn²⁺) on Bi adsorption were investigated. The removal rate was 91.90% when 10 g L–1 adsorbent was added at 25 °C in 40 mL Bi solution with an initial concentration of 50 mg L–1. The pseudo-second-order kinetic model could better describe the adsorption process than pseudo-first-order model, demonstrating that the adsorption of Bi by the orange peel biochar was predominantly chemisorption. Analytical techniques such as SEM, FTIR, XRD, and XPS indicated that the adsorption mechanism concerned electrostatic attraction, ion exchange, π-π electron donor–acceptor interaction, – OH and – COOH complexation, and pore filling. Orange peel biochar demonstrated a sustained performance, maintaining over 65% removal efficiency for Bi after three regeneration cycles. Orange peel biochar has a good application prospect as a cost-effective bio-sorbent for the treatment of Bi removal from water.
... The surface area and porosity of coconut residues biochar can also be impacted by the thermochemical method employed, feedstock characteristics, and process conditions, while modification typically increases biochar surface area, as can be observed in Table 4. However, excess modification might block the pores in the biochar, thereby leading to decreased surface properties (Mo et al., 2022). As a result, acid washing might be required to improve the surface properties of the biochar (Uchimiya et al., 2012). ...
The world's growing population and industrial activities have led to increased energy demand and the depletion of fossil fuels, causing environmental pollution and global warming. A paradigm shift from fossil fuel resources to sustainable energy sources is therefore inevitable. The production of biofuel, such as biochar, from biomass has been receiving increased research attention due to its benefits, which address several environmental issues while advancing the circular economy and sustainable development. This manuscript presents a comprehensive overview of the conversion of coconut biomass residue into biochar, focusing on production methods, physicochemical properties, and versatile applications. Various techniques that have been used for coconut biochar production, including pyrolysis, gasification, torrefaction, and hydrothermal carbonization, are examined in detail, considering their potential for sustainable resource utilization. The interplay between production parameters and resultant biochar characteristics is underscored, elucidating the influence of feedstock composition, pyrolysis conditions, and activation procedures. The findings revealed that the produced biochar has been employed in wastewater treatment, soil amendment, and carbon sequestration, among others. This vast application is a result of the biochar’s distinct physicochemical properties, including high porosity, substantial surface area, the presence of several surface functional groups, and thermal stability. Notwithstanding, biochar production from coconut residues faces several challenges. These challenges were addressed in this review, and relevant recommendations were proposed.
... Ni(II), Pb(II), and Cd (II) showed similar results (Guo et al., 2008). Mo et al. (2022) performed XPS and FTIR studies on chitosan-modified CS biochar before and after Cd 2+ adsorption. FTIR bands assigned to O-containing functional groups shifted to a higher wavenumber with a decreased intensity. ...
... 29.49% of the total Cd 2+ adsorption was caused by ion exchange for coconut shell biochar pyrolyzed at 400 • C (Wu et al., 2021). XRD patterns confirmed precipitations of cadmium salts (Cd(OH) 2 , CdCO 3 ) on coconut shell biochar (Mo et al., 2022;Wu et al., 2021). Π-Metal interaction similar to lead adsorption has also been reported (Wu et al., 2021). ...
... FTIR (a) and XPS (b) spectra before and after Cd 2+ adsorption by chitosan-modified CS biochar. The high-resolution spectra of O 1s (c) and C 1s (d) before and after Cd 2+ adsorption(Mo et al., 2022). ...
For several decades, water pollution has become a major threat to aquatic and non-aquatic species, including
humans. Different treatment techniques have already been proposed and implemented depending on wastewater
characteristics. But many of these treatment techniques are expensive and inefficient. Adsorption-based tech-
niques have shown impressive performances as an inexpensive treatment method previously. Coconut-based
resources have been considered as adsorbents for wastewater treatment because of their abundance, low cost,
and favorable surface properties. However, over the last decade, no comprehensive study has been published
regarding biochar from coconut-based materials for wastewater treatment and CO2 capture. This review dis-
cusses biochar production technology for coconut-based materials, its modification and characterization, its
utilization as an adsorbent for removing metals and organics from wastewater, and the associated removal
mechanisms and the economic aspects of coconut-based biochar. Coconut-based materials are cheap and
effective for removing various organic compounds such as pesticides, hormones, phenol, and phenolic com-
pounds from solutions and capturing CO2 from air mainly through the pore-filling mechanism. Utilizing coconut-
based biochars in a hybrid system that combines adsorption and other techniques, such as biotechnology or
chemical coagulation is a promising way to increase their performance as an adsorbent in wastewater treatment.
... After Cd(II) adsorption, the vibrating peak of -OH, -COOH, C-O-C, P-O/P = O and Si-O weakened or shifted, indicating that O-containing functional group on BC and HAP@BC underwent chemical interaction with Cd(II) Yang et al. 2022). The C = C and -CH 2 groups weakened after adsorption, suggesting that the aromatic structure in BC and HAP@BC provided π-electron and formed Cd(II)-π interaction for the Cd(II) removal (Mo et al. 2022;Wu et al. 2022). This result indicated that the O-containing functional group and aromatic structure were involved in the Cd(II) removal (Meng and Hu 2021). ...
... Dosage Figure active sites, which resulted in a decrease in the amount of adsorption per unit area (Mo et al. 2022;Zhao et al. 2022a). Therefore, considering the removal efficiency and economic benefit, the optimal dosage of adsorbent was 0.4 g/L. ...
... This indicated an electrostatic interaction between Cd(II) and sorbent (Zahedifar et al. 2021). The nature of electrostatic interaction was that when the solution pH was below pH pzc , H + occupied the -OH/-COOH groups on the sorbent surface making the sorbent protonated and mutually exclusive with Cd 2+ (Mo et al. 2022;Zhao et al. 2022a). At solution pH > pH pzc , the -OH/-COOH groups deprotonated and enhanced the adsorption of Cd 2+ (Wu et al. 2023). ...
Biochar with well-developed pore structure is an ideal carrier for easily agglomerated hydroxyapatite (HAP). Hence, a novel multifunctional hydroxyapatite/sludge biochar composite (HAP@BC) was synthesized by chemical precipitation method and used for mitigating Cd(II) contamination form aqueous solution/soil. Compared to sludge biochar (BC), HAP@BC exhibited rougher and more porous surface. Meanwhile, the HAP was dispersed on the sludge biochar surface, which reduced the agglomeration of HAP. The adsorption performance of HAP@BC on Cd(II) was better than that of BC under the influence of different single-factor batch adsorption experiments. Moreover, the Cd(II) adsorption behavior by BC and HAP@BC was uniform monolayer adsorption, and this reaction process was endothermic and spontaneous. The Cd(II) maximum adsorption capacities of BC and HAP@BC were 79.96 and 190.72 mg/g at 298 K, respectively. Moreover, the Cd(II) adsorption mechanism on BC and HAP@BC included complexation, ion exchange, dissolution-precipitation and Cd(II)-π interaction. According to the semi-quantitative analysis, ion exchange was the main mechanism for Cd(II) removal by HAP@BC. Notably, HAP played a role in the Cd(II) removal by dissolution-precipitation and ion exchange. This result suggested that there was a synergistic effect between HAP and sludge biochar for the Cd(II) removal. HAP@BC reduced the leaching toxicity of Cd(II) in soil better than BC, indicating that the HAP@BC was able to mitigate Cd(II) contamination in soil more effectively. This work demonstrated that sludge biochar was an ideal carrier for dispersed HAP and provided an effective HAP/biochar composite for the mitigation of Cd(II) contamination in aqueous solution/soil.
... Alkali metals play the role of ion exchange in the process of metal adsorption. Among them, Ca ions play an important role in the ion exchange of metal cations under medium acidic conditions 73,74 . In the present study, the experiment on Cd adsorption was performed at pH 5.0, and Ca release was observed from both ALG and ALP-AGS. ...
Aerobic granular sludge (AGS) is a proven resource for the recovery of biopolymers like alginate-like polymers (ALP). This is the first report on the dynamics of ALP produced by AGS (ALP-AGS) in a full-scale wastewater treatment plant (WWTP), optimization of ALP recovery from AGS, and adsorption of cadmium (Cd ²⁺ ) by ALP. Recovery of ALP was highest when using 120 mL of 0.2 M Na 2 CO 3 at 70 °C for 45 min. Seasonal (1.5 years, over 3100 cycles) and intra-cycle changes in ALP-AGS in the WWTP were monitored. The ALP content in AGS increased in the transition period between winter and spring, reaching over 150 mg/g MLSS. In the batch reactor cycle, the ALP-AGS level peaked 2 h after the start of aeration (mean peak level: 120 mg/g MLSS), then decreased about two-fold by the end of the cycle. The ALP-AGS had a small surface area and a lamellar structure with crystalline outgrowths. The optimal conditions of Cd ²⁺ adsorption with ALP were a dosage of 7.9 g d.m./L, a pH of 4–8, and an equilibrium time of 60 min. Carboxyl and hydroxyl groups were the key functional groups involved in Cd ²⁺ adsorption. According to the Sips model, the maximum Cd ²⁺ adsorption capacity of ALP-AGS was 29.5 mg/g d.m., which is similar to that of commercial alginate. AGS is a richer source of ALP than activated sludge, which ensures the cost-effectiveness of ALP recovery and increases the sustainability of wastewater treatment. Information on the chemical properties and yields of ALP from full-scale WWTPs is important for downstream applications with the recovered ALP.
... The equilibrium adsorption amount q e (mg/g) and the percentage removal R (%) were calculated by Equations (1) and (2), respectively [40]: ...
Sericin is a by-product of the silk industry. Its recycling contributes to environmental protection and the sustainable development of the cocoon silk industry. In this paper, on the basis of realizing sericin enrichment in solution, the Cu(II) adsorption capacities of sericin-derived carbon (SC), prepared at different pyrolysis temperatures, were studied. SC was characterized using scanning electron microscopy (SEM) and the zeta potential. The effects of the initial concentration of Cu(II), pH, adsorption temperature, and contact time on the adsorption process were evaluated, followed by an investigation of the mechanism of Cu(II) adsorption by SC. The results showed that SC has a porous structure that provides sites for Cu(II) adsorption. The maximum adsorption capacity of Cu(II) onto SC1050, 17.97 mg/g, was obtained at an adsorption temperature of 35 °C and a pH of 5.5. In addition, the pseudo-second-order kinetic model and Langmuir isotherm model correctly described the adsorption process of Cu(II) onto SC1050. Therefore, SC can act as a potential adsorbent for removing Cu(II) from water. This study helps promote the effective use of cocoon silk resources.
... The initial solution pH is regarded as a critical factor in the adsorption of Cd(II) since it may affect the surface charge of adsorbent, Cd(II) species, and the dissolution of mineral constituents [37]. The influence of initial pH on Cd(II) adsorption was investigated using an initial pH range between 2 and 8 as shown in Fig. 4. In the pH range of 2-8, the predominant species was Cd 2+ (Fig. 4a). ...
The removal potential of cadmium (Cd(II)) from aqueous solution by waste mango kernel biochar (MKB) was investigated for the first time. MKB was prepared by pyrolyzing mango kernel waste at 300–700 °C for 2 h. The effects of pyrolysis temperature on physicochemical characteristics of MKB were described by Brunauer–Emmett–Teller (BET), scanning electron micrographs with energy dispersive system (SEM–EDS), Fourier transform infrared (FTIR), and X-ray diffractometer (XRD). Batch adsorption experiments were also performed to study adsorption properties for Cd(II) of MKB. The results indicated that the pH, C content, specific surface area, and pore volume increased obviously with the pyrolysis temperature increased, while the element ratio and surface functional groups decreased. The variation of Cd(II) adsorption capacity with time and initial concentration were better fitted by pseudo-second-order and Langmuir isotherm models, respectively, indicating that the MKB adsorption process was a monolayer adsorption dominated by chemical adsorption. Increasing the pyrolysis temperature increased the maximum adsorption capacity and MKB700 had the highest Langmuir sorption capacity for Cd(II) (27.81 mg g⁻¹) at pH 6.0. Multiple consecutive adsorption–desorption cycles revealed the good reusability of MKB. Further analysis showed that the Cd(II) adsorption mechanism on MKB700 was primarily attributed to complexation reaction with functional groups, ion exchange, and precipitation reaction. This study demonstrated that MKB could be a low-cost and recyclable adsorbent, which could be a promising method of mango kernel waste resourceful treatment.
