Development of clay composites for the removal of textile dyes from aqueous solutions

Abstract

In the present research project, the adsorption capability of clay and the magnetic properties of iron oxides were combined in composite forms for the preparation of magnetic adsorbents. Biocomposites of clay were also prepared with biomass. The prepared magnetic composites may well be efficiently used as adsorbent for a large variety of pollutants in water which could be efficiently excluded from the medium by an easy magnetic process. Clay and iron oxide magnetic composites were prepared by using different molar ratio of MnCl2 and FeCl3 i.e., 1:2, 1:3, 2:3 and characterized by powder XRD, TGA, and FTIR. The batch mode experiments were established for comparing the adsorption capability of native clay, the prepared MnFe2O4/clay composite and biocomposite forms of adsorbents for elimination of the basic dyes. Imperative method parameters like adsorbent dose, pH, initial concentration of dyes, operating temperature and contact time were optimized through batch mode of study. The experimental results showed that pH 6-9, low adsorbent dosage and lower temperature were the viable conditions for maximum adsorptive exclusion of dyes. Different kinetic models were employed to the records obtained by adsorptive removal of the four basic dyes and was noticed that pseudo-second-order kinetic model fitted the best onto the experimental results. Mechanism of the adsorption phenomenon was explained by application of different equilibrium isotherms on the data and Langmuir adsorption isotherm was observed to be the most fitted model on experimental results of the studied dyes. Thermodynamic study revealed that adsorption phenomenon was more viable at lower temperatures as shown by lower ΔG values. The negative values of ΔH indicated the exothermic nature of adsorption phenomenon. The column mode study was performed to optimize the initial dye concentration, bed height and flow rate. Higher bed heights, higher initial dye concentrations and lower flow rates were observed to be more complimentary conditions for maximum adsorptive removal in column mode experiments. The whole study proved that the prepared clay composites can be efficiently utilized for the removal of dyes for wastewater treatment.