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ABSTRACT
Chromium is present in wastewaters resulted from a lot of industrial processes such as electroplating, dye, cement, leather tanning, and paint. Its presence at values higher than maximum admitted value of 0.05 mg/L can affect the human health and the environment. Therefore, it is essential to remove chromium from wastewaters before discharge. In this study, the adsorption potential of three types of Co (II)-based phosphonate metal organic frameworks, obtained by the reaction of CoSO4.7H2O with phosphonoacetic acid (CP), N,N-bis(phosphonomethyl)glycine (Gly), or vinyl phosphonic acid (VP) in hydrothermal conditions, has been investigated. The study involves batch types experiments investigating the effects of the solution pH, solid:liquid ratio, initial concentration of Cr(VI), and contact time upon the adsorption efficiency of the studied materials. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich were applied to adsorption equilibrium data to find the best among these models. The kinetics of adsorption was found to follow the pseudo-second-order model. It was found that the adsorption efficiency of the studied materials in the removal process of Cr(VI) ions from aqueous solutions is in the following order: Co-CP<Co-Gly< Co-VP.
Funding
This work was supported partially by Program no 2 from the Institute of Chemistry Timisoara of Romanian Academy and by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-RU-TE-2014-4-1398. Dedicated to the 150th anniversary of the Romanian Academy.