Sustainable removal of Cu~(2+), Ni~(2+) and Zn~(2+) ions from severe contaminated water using kaolin/poly(glycine) composites, characterization and uptake studies

摘要

Kaolinite clay of Saint Catharine, Sinai, was treated by glycine molecules and then modified by various diamino-compounds like ethylenediamine, phenyl hydrazine and polyoxypropy-lenediamine. The native and modified clays were structurally and texturally characterized by XRD, FTIR, XRF, BET, pore size distribution and SEM in addition to exchange capacity parameters. Phenyl hydrazine and polyoxypropylenediamine organo-modifiers proved superior in function compared to ethylenediamine with regard to in situ glycine polymerization forming large fragments of ordered polypeptides which acted as super clay sheet binders. Adsorption of Cu(Ⅱ), Ni(Ⅱ) and Zn(Ⅱ) ions by the modified kaolinite under variable concentrations of metal ions and interacting time were studied. Adsorption isotherm investigation indicated that Freundlich equation was a better fit than Langmuir model reflecting surfaces of various accommodated active sites with analogue sites distribution. The adsorption rate constants sequence for all modified kaolinite derivatives proved to be Zn~(2+)＞Ni~(2+)＞Cu~(2+). Near 100% removal for Cu~(2+), Ni~(2+) and Zn~(2+) ions from contaminated water were performed via phenyl hydrazine and polyoxypropylenediamine modified kaolin/poly(glycine) composites due to the expected feature of layers expansion and ultimate exposure of hidden adsorption sites buried deeply in kaolinite interlayers.