Efficient removal of chromium(VI) from dilute aqueous solutions using agro-industrial residue based on parboiled-rice husk ash

Abstract

The removal of Cr(VI) from wastewater by adsorption from agro-industrial residues remain an attractive option since combines reasonable cost with the quality of effluents treated. This paper employs of parboiled-rice husk ash (RHA) and parboiled-rice husk ash chemically treated (RHAH⁺) as adsorbents for Cr(VI). The RHA and RHAH⁺ were characterized. It was studied the adsorption efficiency on adsorbent dosage, pH, chromium concentration, and interaction time. RHAH⁺ presented superior Cr(VI) removal, although both adsorbents have shown satisfactory results. The best results are obtained at pH 1.0, presenting 90.9% and 97.7% of Cr(VI) removal for RHA and RHAH⁺, respectively, in 5 mg L⁻¹ of Cr(VI) concentration at about 30 minutes. The adsorption of RHAH⁺ is governed by the Freundlich isotherm (R²_adj = 0.989) and kinetically by the pseudo-second order model (R²_adj = 0.991). The rice rusk ash represents an alternative low-cost and environment-friendly material that efficiently removes Cr(VI) from dilute aqueous solutions.

Keywords:

• Adsorption
• agro-industrial residue
• Cr(VI)
• hexavalent chromium
• parboiled-rice husk ash

Acknowledgments

The authors acknowledge the kind support of the Cooperja Agroindustrial Cooperative, Center for Microscopy and Microanalysis (UFRGS), the X-ray Laboratory of the Institute of Physics (UFRGS) and the Multi-User Thermal Analysis Laboratory (UFRGS).