Kinetics and equilibrium studies on biosorption of hexavalent chromium from leather tanning wastewater by Sargassum tenerrimum from Chabahar-Bay Iran

The traditional leather tanning is one of the oldest technologies which produces effluents containing different pollutants, including Cr(VI) oxyanions. In this lab-scale study, batch experiments were conducted to measure Cr(VI) removal capacity of Sargassum tenerrimum. The efficacy of biosorption was optimized considering variables including pH, temperature, initial chromium concentration, as well as biomass particle size and dosage. Surface characteristics of S. tenerrimum and its changes after Cr(VI) adsorption were investigated by BET/BJH, SEM-EDX and FT-IR techniques. Desorption studies were carried out to investigate the capability of multiple uses of the algal biomass, with the results showing a high performance of five successive sorption/desorption cycles. The maximum biosorption was obtained with the biomass particle size of 0.6 mm at 25 °C at pH 2. The Langmuir isotherm model was recognized as the most correlated model of biosorption where the maximum biosorption capacity (qmax) was obtained to be 37.7 mg/g dry biomass. The batch experiments were repeated using real tannery wastewater under the optimized conditions and the biosorbent could remove about 88% of Cr(VI) from the real wastewater. •Efficacy of biosorption of Cr(VI) by Sargassum tenerrimum was investigated.•The Langmuir isotherm kinetic model (qmax, 83.3 mg/g) was properly fitted.•The biosorbent could successfully pass eight successive sorption/desorption cycles.•Cr(VI) was efficiently (88.5%) removed from tanning wastewater effluent sample.•SEM-EDX and FT-IR analysis revealed the mechanism of chromium sorption.