469820 Selenate Reduction from Mine Water By Redox Reaction and Adsorption Process
Several kinetics models including pseudo first-order, pseudo second-order, power function, Elovich equation, and parabolic diffusion were used to analyze the data. The high r2 (square of the correlation coefficient) value for the Elovich model suggests that the data are generally best described by this equation for selenate adsorption at the experimental condition. The results suggest that the adsorption kinetics could potentially be a chemisorptions process. Literature data indicate that the Elevoch equation has general application to the chemisorption kinetics. Thermodynamics study results reveal that increasing temperature increased the kinetics and adsorption capacity. The calculated heat of adsorption value [ΔH] ranged between 130 and 150 KJ/mol. The X-Ray Photon Spectroscopy (XPS) results indicate that after adsorption, selenium onto the spent media existed in the form of elemental selenium [Se0]. It is apparent that the elemental selenium is the product of the redox reaction. It is anticipated that the selenate removal by the media could be a combination of redox reaction and chemisorptions process.
Selenium concentration in the Toxic Characteristics Leaching Procedure (TCLP) extract of the spent media was less than the regulatory limit of 1 mg/l, the spent media can be disposed as a non-hazardous material.