With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environmen...With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.展开更多
A well-known hazardous metal and top contaminant in wastewater is hexavalent chromium. The two forms of most commonly found chromium are chromate ( CrO 4 2− ) and dichromate ( Cr 2 O 7 2− ). Leather tanning, cooling t...A well-known hazardous metal and top contaminant in wastewater is hexavalent chromium. The two forms of most commonly found chromium are chromate ( CrO 4 2− ) and dichromate ( Cr 2 O 7 2− ). Leather tanning, cooling tower blow-down, plating, electroplating, rinse water sources, anodizing baths etc. are the main sources of Cr (VI) contamination. The Cr (VI) is not only non-biodegradable in the environment but also carcinogenic to living population. It is still difficult to treat Cr contaminated waste water effectively, safely, eco-friendly, and economically. As a result, many techniques have been used to treat Cr (VI)-polluted wastewater, including adsorption, chemical precipitation, coagulation, ion-exchange, and filtration. Among these practices, the most practical method is adsorption for the removal of Cr (VI) from aqueous solutions, which has gained widespread acceptance due to the ease of use and affordability of the equipment and adsorbent. It has been revealed that Fe-based adsorbents’ oxides and hydroxides have high adsorptive potential to lower Cr (VI) content below the advised threshold. Fe-based adsorbents were also discovered to be relatively cheap and toxic-free in Cr (VI) treatment. Fe-based adsorbents are commonly utilized in industry. It has been discovered that nanoparticles of Fe-, Ti-, and Cu-based adsorbents have a better capacity to remove Cr (VI). Cr (VI) was effectively removed from contaminated water using mixed element-based adsorbents (Fe-Mn, Fe-Ti, Fe-Cu, Fe-Zr, Fe-Cu-Y, Fe-Mg, etc.). Initial findings suggest that Cr (VI) removal from wastewater may be accomplished by using magnesium ferrite nanomaterials as an efficient adsorbent.展开更多
Methacrylic acid was used together with a molecular imprinting technique to modify chitosan. In addition, the adsorption kinetics and adsorption isotherms were recorded and the results were analyzed to investigate rep...Methacrylic acid was used together with a molecular imprinting technique to modify chitosan. In addition, the adsorption kinetics and adsorption isotherms were recorded and the results were analyzed to investigate reparative adsorption for Cr（VI） from the polluted Xiangjiang River water. A comparative X-ray analysis shows that the degree of crystallization in the imprinted polymer was significantly weakened, the area of the non-crystalline region was larger. There were more adsorption sites in the imprinted polymer, and the adsorption capacity towards Cr（VI） was increased. The adsorption capacity of the imprinted polymer towards Cr（VI） increased with time and reaches saturation after 8 h. The optimal adsorption time was 4-8 h after the adsorption starting and the optimal pH value for the solution was in the range of 4.5-7.5. When the chitosan reaches saturation, the adsorption capacity achieves a state of equilibrium, and the maximum Cr（VI） extraction rate reaches 33.7%. Moreover, the adsorption capacity of the imprinted polymer towards Cr（VI） increases with increasing chitosan concentration. In this situation, the Cr（VI） extraction rate shows little variation, and the maximum removal rate can reach 98.3%. Furthermore, the Cr（VI） extraction rate increases with an increase in the degree of deacetylation in the chatoyant and chitosan, with the best adsorption effect corresponding to 90% deacetylation. Fitting the adsorption data to the quasi first- and second-order kinetic models yields correlation coefficients of 0.9013 and 0.9875, respectively. The corresponding rate constants for the two models are 0.0091 min-1 and 7.129 g/（mg.min）, respectively. Hence, the adsorption using Cr（VI）-imprinted chitosan is more consistent with the second-order kinetics. Comparing the data to Freundlich and Langrnuir adsorption isotherms shows that the latter has a better linear fit and a maximum adsorption capacity of 15.784 mg/g.展开更多
Herein,iron oxide/hydroxides deposits(gossans)were utilized,for the first time,in the fabrication of magnetite nanoparticles(MNPs)to load modified coal(MC).The as-synthesized MNPs@MC composite was characterized via di...Herein,iron oxide/hydroxides deposits(gossans)were utilized,for the first time,in the fabrication of magnetite nanoparticles(MNPs)to load modified coal(MC).The as-synthesized MNPs@MC composite was characterized via different techniques and utilized for the Cr(Ⅵ)remediation.Experimental studies supported by theoretical treatment were applied to offer a new overview of the Cr(Ⅵ)adsorption geometry and mechanism at 25-45℃.Experimental results suggested that the Cr(Ⅵ)uptake was mainly governed by adsorption-reduction coupled mechanism.The Langmuir model fitted well the Cr(Ⅵ)adsorption data with maximum adsorption capacities extended from 115.24 to 129.63 mg·g^(-1).Theoretical calculations indicated that Cr(Ⅵ)ions were adsorbed on the MNPs@MC following the theory of the advanced monolayer statistical model.The number of ions removed per site ranged from 1.88 to1.23 suggesting the involvement of vertical geometry and multi-ionic mechanism at all temperatures.The increment of the active sites density and the adsorption capacity at saturation with improving temperature reflected an endothermic process.Energetically,the Cr(Ⅵ)adsorption was controlled by physical forces as the adsorption energies were less than 40 kJ·mol^(-1).The calculated free enthalpy,entropy.and internal energy explained the spontaneous nature and the viability of Cr(Ⅵ)adsorption on the MNPs@MC adsorbent.These results offer a new approach in utilizing the iron-rich deposits as gossans in the preparation of magnetic and low-cost adsorbents for wastewater remediation.展开更多
基金supported by the National Natural Science Foundation of China (No.52364022)the Natural Science Foundation of Guangxi Province,China (Nos.2023JJA160192 and 2021GXNSFAA220096)+1 种基金the Guangxi Science and Technology Major Project,China (No.AA23073018)the Guangxi Chongzuo Science and Technology Plan,China (No.2023ZY00503).
文摘With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(Ⅵ) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(Ⅵ). The waste amidoxime resin was first modified with H3PO4 and ZnCl_(2), and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(Ⅵ) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(Ⅵ) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(Ⅵ) to Cr(Ⅲ) and decrease the toxicity of Cr(Ⅵ) during adsorption. PPR-Z exhibited Cr(Ⅵ) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(Ⅵ) adsorption are the chemical reduction of Cr(Ⅵ) into Cr(Ⅲ) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(Ⅵ) pollution and realizes the concept of “treating waste with waste”.
文摘A well-known hazardous metal and top contaminant in wastewater is hexavalent chromium. The two forms of most commonly found chromium are chromate ( CrO 4 2− ) and dichromate ( Cr 2 O 7 2− ). Leather tanning, cooling tower blow-down, plating, electroplating, rinse water sources, anodizing baths etc. are the main sources of Cr (VI) contamination. The Cr (VI) is not only non-biodegradable in the environment but also carcinogenic to living population. It is still difficult to treat Cr contaminated waste water effectively, safely, eco-friendly, and economically. As a result, many techniques have been used to treat Cr (VI)-polluted wastewater, including adsorption, chemical precipitation, coagulation, ion-exchange, and filtration. Among these practices, the most practical method is adsorption for the removal of Cr (VI) from aqueous solutions, which has gained widespread acceptance due to the ease of use and affordability of the equipment and adsorbent. It has been revealed that Fe-based adsorbents’ oxides and hydroxides have high adsorptive potential to lower Cr (VI) content below the advised threshold. Fe-based adsorbents were also discovered to be relatively cheap and toxic-free in Cr (VI) treatment. Fe-based adsorbents are commonly utilized in industry. It has been discovered that nanoparticles of Fe-, Ti-, and Cu-based adsorbents have a better capacity to remove Cr (VI). Cr (VI) was effectively removed from contaminated water using mixed element-based adsorbents (Fe-Mn, Fe-Ti, Fe-Cu, Fe-Zr, Fe-Cu-Y, Fe-Mg, etc.). Initial findings suggest that Cr (VI) removal from wastewater may be accomplished by using magnesium ferrite nanomaterials as an efficient adsorbent.
基金Project(41271332)supported by the National Natural Science Foundation of ChinaProject(2010YBB186)supported by the Social Science Foundation of Hunan Province,Chian
文摘Methacrylic acid was used together with a molecular imprinting technique to modify chitosan. In addition, the adsorption kinetics and adsorption isotherms were recorded and the results were analyzed to investigate reparative adsorption for Cr（VI） from the polluted Xiangjiang River water. A comparative X-ray analysis shows that the degree of crystallization in the imprinted polymer was significantly weakened, the area of the non-crystalline region was larger. There were more adsorption sites in the imprinted polymer, and the adsorption capacity towards Cr（VI） was increased. The adsorption capacity of the imprinted polymer towards Cr（VI） increased with time and reaches saturation after 8 h. The optimal adsorption time was 4-8 h after the adsorption starting and the optimal pH value for the solution was in the range of 4.5-7.5. When the chitosan reaches saturation, the adsorption capacity achieves a state of equilibrium, and the maximum Cr（VI） extraction rate reaches 33.7%. Moreover, the adsorption capacity of the imprinted polymer towards Cr（VI） increases with increasing chitosan concentration. In this situation, the Cr（VI） extraction rate shows little variation, and the maximum removal rate can reach 98.3%. Furthermore, the Cr（VI） extraction rate increases with an increase in the degree of deacetylation in the chatoyant and chitosan, with the best adsorption effect corresponding to 90% deacetylation. Fitting the adsorption data to the quasi first- and second-order kinetic models yields correlation coefficients of 0.9013 and 0.9875, respectively. The corresponding rate constants for the two models are 0.0091 min-1 and 7.129 g/（mg.min）, respectively. Hence, the adsorption using Cr（VI）-imprinted chitosan is more consistent with the second-order kinetics. Comparing the data to Freundlich and Langrnuir adsorption isotherms shows that the latter has a better linear fit and a maximum adsorption capacity of 15.784 mg/g.
基金supported by Researchers Supporting Project number(RSP2023R455),King Saud University,Riyadh,Saudi Arabia。
文摘Herein,iron oxide/hydroxides deposits(gossans)were utilized,for the first time,in the fabrication of magnetite nanoparticles(MNPs)to load modified coal(MC).The as-synthesized MNPs@MC composite was characterized via different techniques and utilized for the Cr(Ⅵ)remediation.Experimental studies supported by theoretical treatment were applied to offer a new overview of the Cr(Ⅵ)adsorption geometry and mechanism at 25-45℃.Experimental results suggested that the Cr(Ⅵ)uptake was mainly governed by adsorption-reduction coupled mechanism.The Langmuir model fitted well the Cr(Ⅵ)adsorption data with maximum adsorption capacities extended from 115.24 to 129.63 mg·g^(-1).Theoretical calculations indicated that Cr(Ⅵ)ions were adsorbed on the MNPs@MC following the theory of the advanced monolayer statistical model.The number of ions removed per site ranged from 1.88 to1.23 suggesting the involvement of vertical geometry and multi-ionic mechanism at all temperatures.The increment of the active sites density and the adsorption capacity at saturation with improving temperature reflected an endothermic process.Energetically,the Cr(Ⅵ)adsorption was controlled by physical forces as the adsorption energies were less than 40 kJ·mol^(-1).The calculated free enthalpy,entropy.and internal energy explained the spontaneous nature and the viability of Cr(Ⅵ)adsorption on the MNPs@MC adsorbent.These results offer a new approach in utilizing the iron-rich deposits as gossans in the preparation of magnetic and low-cost adsorbents for wastewater remediation.
