Removal of Cr(VI) by modified brown algae Sargassum bevanom from aqueous solution and industrial wastewater

•To modify the algae performance by a simple pretreatment.•Application of modified algae for removal of Cr(VI) from aqueous solution and industrial wastewater.•Study the desorption process and reusability of adsorbent.

The aim of this research work is to investigate sorption characteristic of acid treated brown algae Sargassum bevanom (acid treated S. bevanom) for the removal of Cr(VI) ions from aqueous solutions. The acid-treated alga was prepared by transferring the S. bevanom into 0.5 M HCl and then stirring the mixture at 300 rpm for 6 h at room temperature. The sorption of Cr(VI) ions by batch method is carried out. The optimum conditions of biosorption were found to be: a biomass dose of 0.7 g in 100 ml of Cr(VI), contact time of 110 min and pH 3, respectively. In optimum condition, removal efficiency was 89.64%. It was found that temperature has a positive effect on the removal efficiency. Four equations, i.e. Morris–Weber, Lagergren, Elovich and pseudo second order have been tested to track the kinetics of removal process. The Langmuir, Freundlich, Redlich–Peterson (R–P), Temkin and Dubnin–Radushkevic (D–R) are subjected to sorption data to estimate sorption capacity, intensity and energy. The thermodynamic parameters ΔH, ΔS and ΔG are evaluated. Thermodynamic parameters showed that the adsorption of Cr(VI) onto acid treated S. bevanom was feasible, spontaneous and endothermic under studied conditions. It can be concluded that acid treated S. bevanom has potential to remove Cr(VI) ions from aqueous solutions at different concentrations. Also it was achieved 80% desorption efficiency using NaOH and reusing of adsorbent shows high ability in the Cr(VI) removal from aqueous solution. Meanwhile acid treated S. bevanom was used for the removal of Cr(VI) from industrial wastewater that shows considerable results.