Biosorption of rhodamine B dye from dyeing stones effluents using the green microalgae Chlorella pyrenoidosa

Rhodamine B has been widely used in dyeing of semiprecious stones (agate), which are exported from the Southern Brazil, and in this dyeing process, colored effluents are generated. So, the objective of this study was the use green microalgae Chlorella pyrenoidosa for the removal of rhodamine B dye from dyeing stones effluents. Biosorption was carried out in order to evaluate effects of pH, contact time and temperature. Biosorption kinetics was studied for the dye concentration range of 20-500 mg L-1 using pseudo first order, pseudo second order and Elovich models. Equilibrium isotherms were analyzed by the Langmuir, Freundlich, Sips and Temkin models. Results showed that when the initial dye concentration was 100 mg L-1, the microalgae biomass presented the highest biosorption capacity, at pH 8.0 and temperature of 25 degrees C. The time required to reach the equilibrium was 120 min. The kinetic model that better fitted the experimental data was pseudo-second order, with an average relative error lesser than 2.4%. The Sips isotherm presented the best performance, being the calculated values of biosorption capacities of 63.14; 53.46 and 54.20 mg g(-1) for the temperatures of 25, 35 and 45 degrees C respectively, demonstrating that a temperature increase has a negative effect on the biosorption capacity. Results indicated that the biosorption using Chlorella pyrenoidosa has a great potential for rhodamine B removal from dyeing stones effluents. (C) 2018 Elsevier Ltd. All rights reserved.