Desorption of Methylene blue dye from brown macroalga: Effects of operating parameters, isotherm study and kinetic modeling

Abstract

In this study, desorption of Methylene blue (MB) dye from brown macroalga, Nizamuddinia zanardinii was investigated. Batch experiments were conducted to determine the effects of various operating parameters namely, the effect of seventeen different eluents, eluents concentrations, dye saturated alga weight, different HCl:1-butanol ratios, different particle sizes, different alga mass washing modes (after sorption experiment), initial dye concentration in the sorption experiment and contact time on the desorption efficiency of MB dye from brown macroalga. Among the seventeen eluents tested, hydrochloric acid (HCl) was found to be the most effective eluent for dye desorption. The mixture of 1 M HCl (25%):1 M 1-butanol (75%) was found to increase the dye desorption efficiency up to 63.67 ± 1.67%. Dye desorption percentage increased by increasing the alga particle sizes from <75 μm to >250 μm. The highest and lowest desorption efficiencies were attained by wet and dry masses after water washing by shaker, respectively. Both isotherm and kinetic data were obtained and fitted very well with the Sips isotherm model and pseudo-second-order kinetic model. After five sorption/desorption cycles, the dye sorption efficiency decreased from 96.99 ± 0.90% to 48.16 ± 1.98%, and the dye desorption efficiency decreased from 68.70 ± 2.03% to 46.83 ± 1.49%. Overall, this study has demonstrated that brown macroalga is a promising sorbent for the removal of MB dye from aqueous solutions.