Sorption capacity of biochars obtained by gasification of rice husks and wild sugarcane: removal of malachite green and arsenic from water solutions

Abstract

The presence of contaminants in water has been of great concern worldwide, as it causes health risks to living organisms and general deterioration of the environment. Therefore, their elimination is essential. In the present study, rice husk (BRH) and wild sugarcane (BWS) biochars obtained by gasification were evaluated for their use as sorbents of malachite green dye (MG) and arsenite [As (III)] in aqueous solution. The chemical composition and physical structure of the two biochars were characterized by various techniques, including elemental analysis, N2 adsorption–desorption isotherms, FTIR, and Z potential. In addition, the adsorbate removal rate was determined using the pseudo-first-order and pseudo-second-order models. Batch sorption studies were carried out to remove arsenite and MG from aqueous solutions, considering the operating parameters such as initial solution pH, temperature, contact time, concentration, and temperature. The results showed that 120 min contact time is enough to reach sorption equilibrium. The percent removal of BRH and BWS to MG was 61.99% and 97.46%, respectively, while for arsenite, it was 82.79% and 82.36%, respectively. The kinetic analysis concluded that the sorption process predominantly followed the pseudo-second-order kinetic model for both case studies since the R 2 value is approximately one. The sorption capacity calculated based on this model fitted better with the sorption capacity experimental. Finally, it was demonstrated that BRH and BWS biochars obtained as a by-product of rice husk and wild sugarcane gasification could be used as low-cost sorbent materials to remove MG dye and arsenite from an aqueous solution.