Effective adsorption of Cr(VI) on mesoporous Fe-functionalized Akadama clay: Optimization, selectivity, and mechanism

• Published in: Applied surface science Vol. 344; pp. 128 - 136
• Main Authors: Ji, Min, Su, Xiao, Zhao, Yingxin, Qi, Wenfang, Wang, Yue, Chen, Guanyi, Zhang, Zhenya
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.07.2015
• Subjects: Adsorbents; Adsorption; Clay (material); Contact; Contribution; Cr(VI) adsorption; Fe-functionalized Akadama clay; Mechanism; Selectivity; Surface chemistry; Wastewater treatment; Cr(VI) adsorption; Selectivity; Fe-functionalized Akadama clay; Contribution; Mechanism
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.03.006

•Fe-functionalized Akadama Clay (FFAC) was prepared with FeCl3.•Independent contribution of influencing factors on Cr(VI) adsorption was tested.•The influence order of coexisting ions followed PO43−>SO42−>Cl−.•Cr(VI) removal was controlled by electrostatic attraction, ligant exchange and redox.•FFAC had four times higher adsorption capacity of Cr(VI) than pristine AC. A Japanese volcanic soil, Akadama clay, was functionalized with metal salts (FeCl3, AlCl3, CaCl2, MgCl2, MnCl2) and tested for Cr(VI) removal from aqueous solution. FeCl3 was selected as the most efficient activation agent. To quantitatively investigate the independent or interactive contribution of influencing factors (solution pH, contact time, adsorbent dose, and initial concentration) to Cr(VI) adsorption onto Fe-functionalized AC (FFAC), factorial experimental design was applied. Results showed initial concentration contributed most to adsorption capacity of Cr(VI) (53.17%), followed by adsorbent dosage (45.15%), contact time (1.12%) and the interaction between adsorbent dosage and contact time (0.37%). The adsorption showed little dependence on solution pH from 2 to 8. Adsorption selectivity of Cr(VI) was evaluated through analyzing distribution coefficient, electrical double layer theory, as well as the valence and Pauling's ionic radii of co-existing anions (Cl−, SO42−, and PO43−). EDX and XPS analyses demonstrated the adsorption mechanism of Cr(VI) onto FFAC included electrostatic attraction, ligant exchange, and redox reaction. Improved treatment for tannery wastewater shows a potential application of FFAC as a cost-effective adsorbent for Cr(VI) removal.