Efficient removal of Cd2+ and Pb2+ from aqueous solution with amino- and thiol-functionalized activated carbon: Isotherm and kinetics modeling
Autor: | Guangming Zeng, Xue-Ting Li, Hai Guo, Cheng-Gang Niu, Ning Tang, Chao Liang, Chao-Wen Zheng, Li-Shen Lin |
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Rok vydání: | 2018 |
Předmět: |
Langmuir
Environmental Engineering Aqueous solution Chemistry Inorganic chemistry Langmuir adsorption model 02 engineering and technology 010501 environmental sciences 021001 nanoscience & nanotechnology 01 natural sciences Pollution symbols.namesake Adsorption Desorption symbols medicine Environmental Chemistry Freundlich equation 0210 nano-technology Waste Management and Disposal 0105 earth and related environmental sciences Activated carbon medicine.drug BET theory |
Zdroj: | Science of The Total Environment. 635:1331-1344 |
ISSN: | 0048-9697 |
Popis: | In order to address the increasingly severe pollution issue caused by heavy metals, activated carbon-based absorbents have gained considerable attention. Herein, two novel adsorbents, amino-functionalized activated carbon (N-AC) and thiol-functionalized activated carbon (S-AC), were successfully synthesized by stepwise modification with tetraethylenepentamine (TEPA), cyanuric chloride (CC) and sodium sulfide. The pristine and synthesized materials were characterized by BET analysis, SEM, FTIR spectroscopy, elemental analysis and zeta-potential analyzer. Meanwhile, their adsorption properties for Cd2+ and Pb2+ and the effects of various variables on the adsorption processes were systematically investigated. The findings confirmed that amino-groups and thiol-groups endowed the AC with a strong affinity for metal ions and that the pH of solution affected the uptake efficiencies of the adsorbents by influencing their surface charges. Furthermore, six isotherm models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Sips and Redlich-Peterson) and four kinetic models (pseudo-first-order, pseudo-second-order, Intra-particle diffusion and Elovich) were applied to interpret the adsorption process at three different temperatures (288 K, 298 K and 308 K). The results indicated that temperature played an important role and that the rate-limiting step was chemosorption. A better fit for all adsorption systems was obtained with Langmuir model, with the maximum adsorption capacities at 298 K of 79.20 mg Cd2+/g and 142.03 mg Pb2+/g for N-AC, 130.05 mg Cd2+/g and 232.02 mg Pb2+/g for S-AC, respectively. Subsequently, the thermodynamic parameters revealed the nature of the adsorption was endothermic and spontaneous under the experimental condition. The possible adsorption procedures and the underlying mechanisms comprising physical and chemical interactions were proposed. Moreover, the as-synthesized adsorbents exhibited excellent regeneration performance after five adsorption/desorption cycles. The overall results demonstrated that both N-AC and S-AC could be the promising efficient candidates for removing Cd2+ and Pb2+ from contaminated water. |
Databáze: | OpenAIRE |
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