Heavy metal adsorption using biogenic iron compounds

A significant number of industries produce large volumes of aqueous effluents containing heavy metals that discharge into the environment threatening biodiversity and human life. However, such effluents pose serious problems for the industry because of the high cost of metal decontamination using conventional technologies. The aim of this work is to study a suitable alternative through the use of iron compounds generated by a natural consortium with adsorptive properties appropriated for metal removal. The biogenic iron precipitates were identified as a mixture containing mainly siderite and magnetite. The use as sorbent was investigated to remove copper, zinc, arsenate and chromate from aqueous solutions. Variables such as the initial pH, contact time and initial metal concentration were evaluated. Three models were used to study the adsorption kinetic: pseudo first order, pseudo second order and Elovich models. Equilibrium data were fitted to Langmuir and Freundlich isotherm models. Higher metal uptakes were obtained with arsenic. Metal sorption was also investigated in the bimetallic system As-Cu.