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| Effect of bed height on the removal of Cr(VI) in the fixed bed column. (Initial concentration: 10 mg/L; Flow rate: 0.5 mL/min; PH: 7 and Temperature: 30 °C).
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In this study, the removal of hexavalent chromium from aqueous solution were examined using activated charcoal derived from Sapindus trifoliate L fruit biomass in continuous fixed-bed column studies. The activated S. trifoliate L fruit charcoal was prepared by treating the fruit powder using concentrated nitric acid solution. Experiments were perfo...
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... breakthrough curve was expressed the ratio of inlet initial concentration of chromium solutions (C t /C 0 ) against the flow time (t). The continuous fixed bed column adsorption studied of Cr(VI) ions at different bed heights (5 cm, 10 cm, & 15 cm) a constant initial concentration 10 mg/L and flow rate 0.5 mL/min, neutral pH, temperature 30 °C and results are presented in Figure 4. Table 2 shows mathematical results of breakthrough curve and saturation time increases with increase in bed-height and contact time of chromium solutions. ...
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... Biochar and compost are mixed evenly into the soil to be repaired at the weight ratios of 0:100, 10:90, 20:80, 40:60, 60:40, and 100:0, respectively. Soil remediation was conducted at 25ºC for two months, during which irrigation was conducted regularly to keep 60% water in the soil [36,37]. Table 3 shows the specific design of the SR experiment. ...
... The eluted metal can also be used for various purposes (Lata and Samadder 2014;Wang et al. 2015). Activated biochar prepared from S. trifoliate L fruit adsorbed Cr (VI) by 1.719 mg g −1 in the bed height of 15 cm with initial concentration of 10 mg L −1 (Mohanta et al. 2021). In another study, 58.54 mg g −1 of Cr (VI) was removed by the Neem Leaf Biochar at pH 2 (Thangagiri et al. 2022). ...
... To study the specific effect of the combination of flat bamboo flowers and cadmiumtolerant strains on the treatment of cadmium-contaminated wastewater from nuclear emissions, cadmium-tolerant strains isolated and screened from soil contaminated with cadmium from nuclear emissions were selected for hydroponic experiments [37,38]. The specific validation of the treatment effect of the flat bamboo flowers and cadmium-resistant strain on cadmium-polluted water bodies was conducted. ...
The continuous development of China’s nuclear industry has caused an increasingly serious problem of heavy metal pollution in the ecological environment. A survey of the current situation shows that the quality of China’s groundwater bodies and their surrounding ecological environment has been severely affected. China has started to devote more attention to the issue of nuclear emissions and pollution. In view of this, this study takes an area contaminated by nuclear power plant emissions as the object of research and uses plant–microbe synergy to remediate the cadmium-contaminated environment. Cadmium-tolerant strains were isolated from the soil and identified as Serratia marcescens. The morphological characteristics of the cadmium-tolerant strains were observed with electron microscopy in the presence or absence of cadmium ions. The removal of Cd2+ from wastewater was analyzed in four experimental groups: Cd2+ removal from Cd2+-contaminated wastewater by combining a Cd-tolerant strain with Cd-flower, Cd-tolerant strain with Cd-flower, Cd-flower with alkali treatment, and Cd-tolerant strain with alkali treatment. This study innovatively treated Cd ion concentrations of 50 mg/L, 100 mg/L, 200 mg/L, and 300 mg/L. The results showed that the cadmium-tolerant strains were more densely concentrated in the treated Phyllostachys than in the untreated condition. This indicates that the Cd-tolerant strains were effectively enhanced by the alkali treatment of Phyllostachys spp. and that the adsorption of Cd ions to the Cd-tolerant strains was improved. In the presence of Cd2+ flowers only, the best removal of Cd2+ was achieved at a concentration of 50 mg/L, with a removal rate of 74.10%; the addition of Cd-tolerant strains resulted in a removal rate of 91.21%. When the alkali treatment was applied to the flat bamboo flowers, the removal rate was 84.36% when the concentration of Cd2+ was 100 mg/L. Then, when the cadmium-tolerant strain was added to the treated flat bamboo flower group, the maximum removal rate was 89.74% when the concentration of Cd2+ was 100 mg/L. The cadmium ion content of Cd2+ increased positively with increasing experimental time. In addition, the quasi-secondary correlation coefficients for cadmium ions in Lobelia were all greater than 0.9905, indicating that the adsorption kinetics were significantly correlated with the quasi-secondary kinetics. The analysis of heavy metal enrichment in Lobelia was divided into four groups, with Lobelia showing the best tolerance and cadmium adsorption capacity at a cadmium concentration of 20 mg/L. The results of super-enrichment coefficients showed that the enrichment coefficients of Lobelia ranged from 1.03 to 1.97, with values greater than 1. All these results indicate that the combination of cadmium-tolerant strains and plants can effectively remediate nuclear-contaminated soil and wastewater, thus improving soil availability and water regeneration, and improving the human living environment.
... The materials used as adsorbents require previous treatments to improve their functionality. In the case of bioadsorbents, these treatments consist first in the removal of soluble organic matter, for which aqueous solutions of sodium hydroxide, sulfuric acid, nitric acid or hydrochloric acid are used, then they are washed with water and finally subjected to the drying and sieving process [16,17]. In the case of inorganic adsorbents, the previous treatment is simpler, only requiring washing with hot water, drying and sieving. ...
... The peaks at wavelengths 718, 875 and 1425 cm − 1 correspond to asymmetric bending and stretching vibrations of calcite [8,27], which do not show any shift changes. However, where the presence of chromium is clearly appreciated is in the band shift from 798 to 794 cm − 1 corresponding to the O-Si -O bending vibrations and in another band shift from 1010 to 1018 cm − 1 in the symmetric stretching vibration of the Si-O -Si functional group [16,28]. ...
The natural mineral known as Mexicalcite is native to the southern region of Mexico, and due to its abundance and accessibility characteristics, as well as its insolubility in water, it is recommended as an adsorbent material. For such reasons, in this work Mexicalcite was used as adsorbent material to remove Cr(VI) in a packed bed column. The effects of the parameters: bed column height (Z), flow rate (Q), and the initial chromium concentration (C0), on the adsorption capacity (q) and removal percentage (%R) were evaluated. The results show minimal changes in adsorption capacity, specifically a 4% difference; with a mean value of 4.98 mg/g. However, maximum removal percentage was obtained for a high height in the bed column, where there is more contact time. However, low removal percentages were obtained for high flow rate, where the contact time is considerably less. The maximum removal was 94.09%, which was obtained with the highest packed bed height (Z = 6 cm), initial concentration (C0 = 25 mg/L), and lowest flow rate (Q = 2 mL/min). The process was modeled using the Thomas, Adams-Bohart and Yoon-Nelson models. With the BDST model, it was possible to scale up the adsorption process and double the original column dimensions. In addition, the column dimensions were obtained theoretically, to operate continuously for 120 h. Finally, the chromium concentration at the outlet was 0.1 mg/L, using a value of 2 for the bed height/column diameter ratio (Z/d).
... Natural materials like plant husks, cereal brans, seeds, dried leaves, fruit peels, algae have an innate binding affinity for heavy metals and other pollutants and have been utilized by many researchers in their studies. Examples of biomaterial used by former researchers in column reactors are as cited: Igor et al. (2022) experimented on fluorescein removal in both batch and column reactors using modified dry bean pod waste (Phaseolus vulgaris) as the biosorbent; Mohanta et al. (2021) studied adsorption of Cr (VI) employing activated charcoal prepared from fruit biomass of Sapindus trifoliate L. in fixed bed column; Moringa oleifera was employed by Rajeswari et al. (2021) to assess the efficiency of the biomass for removal of Cd(II) in continuous mode from drinking water; adsorption of lead was studied by Srikanth et al. (2021) in fixed bed column reactor utilizing Liagora viscida as the biosorbent; Rajeswari et al. (2022) employed sugarcane bagasse to sequester Ni(II) in packed bed column reactor. ...
The presented study is an experimentation of bioadsorption of cadmium on lentil husk (LH) stacked in fixed bed column reactor. Here the concept of circular economy is integrated to demonstrate its compliance with biological adsorption. In addition sustainability evaluation of the work has been done with respect to environmental, economical and executional procedure. Regarding experimental parameters adsorption capacity, percentage adsorption and breakthrough time all found to be dependent on the variation of design parameters. Sorbate (cadmium) concentration in treated effluents was inversely proportional to bed height and directly related to flow rate owing to prolonged interaction with metal binding sites. Adsorption capacity (164.25 mg g⁻¹) peaked up at highest feed concentration due to formation of concentration gradient overcoming the resistance offered during transfer of solute. Desorption was fruitful (up to ~96%) and the fixed bed regained its performing capacity successively. Industrial effluents were reclaimed with high accuracy for considerable duration.
... Natural materials like plant husks, cereal brans, seeds, dried leaves, fruit peels, algae have an innate binding affinity for heavy metals and other pollutants and have been utilized by many researchers in their studies. Examples of biomaterial used by former researchers in column reactors are as cited: Igor et al. (2022) experimented on fluorescein removal in both batch and column reactors using modified dry bean pod waste (Phaseolus vulgaris) as the biosorbent; Mohanta et al. (2021) studied adsorption of Cr (VI) employing activated charcoal prepared from fruit biomass of Sapindus trifoliate L. in fixed bed column; Moringa oleifera was employed by Rajeswari et al. (2021) to assess the efficiency of the biomass for removal of Cd(II) in continuous mode from drinking water; adsorption of lead was studied by Srikanth et al. (2021) in fixed bed column reactor utilizing Liagora viscida as the biosorbent; Rajeswari et al. (2022) employed sugarcane bagasse to sequester Ni(II) in packed bed column reactor. ...
... The impact of bed height on the breakthrough curves of TC was investigated, as shown in Figure 9, and the parameters were calculated as Equations (S9)-(S13) [60] and ...
... The impact of bed height on the breakthrough curves of TC was investigated, as shown in Figure 9, and the parameters were calculated as Equations (S9)-(S13) [60] and are given in Table 7. Notably, the breakthrough time, depletion time and Y all increased with rising bed height, but the Q f decreased. The rise in bed height meant the increase in the amount of adsorbent in the fixed bed, which had more adsorption active sites, so the breakthrough time was prolonged and Y was increased. ...
Tetracycline (TC) in the water body poses a huge threat to the ecological environment. There is a great challenge to develop highly efficient, green, low-cost and reusable adsorbents for TC removal from saline water. Herein, metakaolin-based geopolymer microspheres (MM) modified by oleic acid were proposed for the enhanced adsorption of TC from saline water. Experimental and characterization results showed that the introduction of oleic acid into the MM effectively adjusted the specific surface area, pore volume and zeta potential of the MM, thus accelerating the adsorption rate and enhancing the TC adsorption capacity of the MM. The adsorption process fitted well to the pseudo-second-order kinetic and Langmuir isothermal models. The Langmuir adsorption capacity of TC by the optimal MM, namely MM3 (0.3%, oleic acid), reached 645.7 mg·g−1 at 298 K, which was higher than many reported adsorbents. The adsorption process was endothermic and spontaneous. The MM3 had good adsorption performance of TC from saline water and regeneration performance. Moreover, the breakthrough curves of the MM3 in a column system were correlative with the Thomas and Yoon–Nelson models. The adsorption mechanisms of TC by the MM3 involved Van der Waals forces, electrostatic interactions, hydrogen–bonding interactions, and ion exchange.
Chromium hydroxide is an important form present in chromium chemicals and a major product in the reduction of hexavalent chromium pollutants, and the study of chromium hydroxide re-oxidation process is crucial in controlling chromium pollution. The aim of this research was to investigate the re-oxidation performance of different forms of chromium hydroxide in air: crystalline chromium hydroxide (C-Cr(OH)3), amorphous chromium hydroxide (A-Cr(OH)3), chromium hydroxide obtained by reduction (R-Cr(OH)3), and aged R-Cr(OH)3 (Aged-R-Cr(OH)3). The results showed that A-Cr(OH)3 had the highest re-oxidation efficiency and the largest re-oxidation rate constant (k), followed by R-Cr(OH)3, Aged-R-Cr(OH)3, and C-Cr(OH)3. The study found that the re-oxidation rate of chromium hydroxide was mainly affected by the surface Cr–O bond energy and physical water. The advantageous re-oxidation of chromium hydroxide could be attributed to its diminutive bond energy of Cr–O and the presence of physical water on its surface. It was observed that increasing the temperature and adding salt (Na2SO4 and Na2CO4) promoted the re-oxidation of Cr(III) for different chromium hydroxides. This effect was particularly noticeable under alkaline conditions induced by Na2CO3 or at a reaction temperature of 200 °C. The re-oxidation rate constant of chromium hydroxides was up to 39.4 times higher at a reaction temperature of 200 °C than at 80 °C. This would be of great significance for chromium contamination removal by controlling the hexavalent chromium reduction products and environmental conditions.
Carbon-centric adsorbents (CCA) are diverse forms, from simple biochar (BC) to graphene derivatives, carbon nanotubes (CNTs), and activated carbon (AC), which have been vastly explored for their removal of a plethora of pollutants, including heavy metals (HM). The prominent features of CCA are their operational attributes like extensive surface area, the occurrence of flexible surface functional groups, etc. This work offers a comprehensive examination of contemporary research on CCA for their superior metal removal aptitude and performances in simulated solutions and wastewater flows; via portraying the recent research advances as an outlook on the appliances of CACs for heavy metal adsorption for removal via distinct forms like AC, BC, Graphene oxide (GO), and CNTs. The bibliometric analysis tool was employed to highlight the number of documents, country-wise contribution, and co-occurrence mapping based on the Scopus database. The coverage of research works in this review is limited to the last 5 years (2017-2021) to highlight recent progress and prospects in using CCAs such as AC, BC, GO, and CNTs to remove HM from aqueous media, which makes the review unique. Besides an overview of the common mechanisms of CACs, the future scope of CAC, especially towards HM mitigation, is also discussed in this review. This review endorses that further efforts should be commenced to enhance the repertory of CCAs that effectively eliminate multiple targeted metals in both simulated and real wastewater.
