Evaluation of Bassanite Efficiency as an Adsorbent for Iron Decontamination in Aqueous Solution

摘要

The advantages of natural adsorbents in adsorption of toxic ions from aqueous solution, comprises their low cost, easy handling, abundancy, and environmental-friendly characteristics, cause their expanding application in decontamination processes. In this study, natural calcium sulfate hemihydrate, which is termed as bassanite mineral, has been proposed as a novel suitable adsorbent for iron (Fe~(3+)) removal from aqueous solution. The properties of bassanite from Saveh region, located in north-western Iran, was characterized by XRD, XRF, and FTIR. The adsorption capacity of iron onto raw bassanite was investigated as a function of contact time, iron initial concentrations, ionic strength, bassanite dosage, and additive electrolyte (HCl, NaCl, and CH3COONa); so, the optimum condition was determined as using 5 g bassanite, particle size -150 μm at room temperature with iron initial concentration of 1000 mg/L, solid to liquid ratio of 50 g/L, contact time of 60 min, and stirrer speed 600 rpm. Afterwards, in order to enhance adsorption capacity, the bassanite was treated with sodium acetate as a modifier electrolyte. This modification was so appropriate and cause to increase adsorption to more than 95 percent of iron from 1 g/L iron solution. The equilibrium studies have been carried out by the consideration of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, which displayed that iron adsorption onto raw and modified bassanite were performed favorably and chemically by the homogenous process. Based on Langmuir model maximum adsorption capacity of raw and modified bassanite are 12.66 mg/g and 117.67 mg/g respectively.