Adsorption of cadmium (II) from aqueous solutions by coconut dregs residue: Kinetic and thermodynamic studies

IF 2.3 4区工程技术 Q3 CHEMISTRY, MULTIDISCIPLINARY

Separation Science and Technology Pub Date : 2023-06-25 DOI:10.1080/01496395.2023.2227914

Chamika K. Madawala, Tiron H. L. Jahinge, K. T. Rathnayake, B. A. Perera

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Abstract

ABSTRACT In this study, the potential of coconut dregs residue (CDR) as a low-cost biosorbent for the removal of cadmium (II) from aqueous solutions was investigated. The removal efficiency of Cd (II) by CDR was tested through batch adsorption experiments under different conditions including contact time, initial pH, initial Cd (II) concentration, adsorbent dose, and temperature. The optimal pH for removal was found to be 7.0 where an 87.6% removal was achieved with a metal concentration of 25 ppm, a 0.5 g/100.00 cm3 adsorbent dosage, and a 250–500 µm particle size within 120 minutes at 303 K. The Freundlich isotherm model was employed to explain the adsorption process, while the pseudo-second-order model proved to be the best-fit kinetic model. Results showed that the Gibbs free energy change in Cd (II) adsorption was −5.4 kJ mol−1 indicating a spontaneous process. The raw CDR exhibited an adsorption capacity of 4.31 mg/g. Scanning electron microscopic (SEM) analysis revealed the presence of tubular voids which contributed to the adsorption process. Additionally, activated carbon prepared from CDR showed a higher removal efficiency of 95.6% for Cd (II) as compared to the raw CDR biosorbent.

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椰渣渣对镉(II)的吸附:动力学和热力学研究

摘要本研究考察了椰渣渣(CDR)作为低成本生物吸附剂去除水中镉(II)的潜力。通过间歇式吸附实验，考察了不同接触时间、初始pH、初始Cd (II)浓度、吸附剂剂量、温度等条件下CDR对Cd (II)的去除效果。结果表明，在金属浓度为25 ppm、吸附剂用量为0.5 g/100.00 cm3、吸附剂粒径为250-500µm、温度为303 K、时间为120分钟的条件下，最佳pH为7.0，去除率为87.6%。采用Freundlich等温线模型来解释吸附过程，拟二阶模型被证明是最合适的动力学模型。结果表明，吸附Cd (II)的吉布斯自由能变化为−5.4 kJ mol−1，为自发过程。CDR的吸附量为4.31 mg/g。扫描电镜(SEM)分析显示，管状空隙的存在有助于吸附过程。此外，CDR制备的活性炭对Cd (II)的去除率为95.6%，高于原始CDR生物吸附剂。

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来源期刊

Separation Science and Technology 工程技术-工程：化工

CiteScore

6.10

自引率

3.60%

发文量

131

审稿时长

5.7 months

期刊介绍： This international journal deals with fundamental and applied aspects of separation processes related to a number of fields. A wide range of topics are covered in the journal including adsorption, membranes, extraction, distillation, absorption, centrifugation, crystallization, precipitation, reactive separations, hybrid processes, continuous separations, carbon capture, flocculation and magnetic separations. The journal focuses on state of the art preparative separations and theoretical contributions to the field of separation science. Applications include environmental, energy, water, and biotechnology. The journal does not publish analytical separation papers unless they contain new fundamental contributions to the field of separation science.