Abstract
The industrial waste, bauxite residue generated in the Bayer chemical process of alumina production, commonly known as red mud (RM) has been used as the adsorbent for selective removal of phosphate in aqueous solutions. RM collected from the storage area of alumina industry was characterized by chemical analysis and physical methods such as BET surface area, Scanning Electron Microscopy (SEM), particle size analysis, and X-ray diffraction (XRD) methods. Among the various red mud samples (0.2–200 μ) studied, the samples treated with 1 M HCl for 2 h were found better for the selective adsorption of phosphate in comparison with untreated and heat treated RM samples. The presence of phosphate in the aqueous samples collected after adsorption studies with red mud was determined by standard spectrophotometric procedure using ammonium molybdate and ascorbic acid in nitrate medium at λmax 880 nm. The studies reported significant adsorption of phosphate on acid treated red mud in comparison with adsorption of phosphate on untreated and heat treated red mud, respectively. The adsorption of phosphate on raw red mud and activated red mud was further investigated with respect to stirring time, pH of the solution, dose of adsorbent, and varying phosphate concentration. Acid treated RM is observed as an efficient and cost-effective adsorbent for selective removal of phosphate in aqueous solutions.
Highlights
Phosphorus as phosphate ions is one of the important soil elements for living organisms
The biological method is of low cost but not effective due to variability in temperature of waste water that would make the execution of this process inaccessible for waste water treatment
Chemical treatments such as alum, lime, and ferric chloride are common precipitants used for phosphate removal but this is cost-ineffective and sludge formation makes this as a tedious method for waste water treatments
Summary
Phosphorus as phosphate ions is one of the important soil elements for living organisms. We have used red mud as an effective adsorbent for the removal of phosphates from aqueous solution. We report the spectroscopic characterization and investigation of the adsorption studies on raw and activated red mud for phosphate removal from aqueous solution. We have investigated the effect on morphology and adsorptive behaviour of the modified red mud by heat and acid treatment. This is done with the help of BET surface analyser, particle size analyser, X-ray diffraction, and Scanning Electron Microscopy
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