Simultaneous removal of cationic dyes from simulated industrial wastewater using sulfated alginate microparticles

Abstract

Double crosslinked sulfated alginate (DCSA) microparticles were applied as adsorbent for simultaneous removal of methylene blue (MB) and rhodamine B (RhB) dyes by the batch method. The adsorption process was optimized in terms of initial dyes concentrations, adsorbent amount, pH, and contact time. Equilibrium adsorption isotherm of dyes were assessed by Langmuir and Freundlich models. The results best fitted with the Langmuir adsorption isotherm model, which confirm the linearity of the process. Maximum adsorption capacities (Qm) of DCSA microparticles in single system were obtained as 612.3 and 545.2 mgg−1 for MB and RhB dyes, respectively. In contrast, Qm vales for the MB and RhB dyes in binary mixed system improved slightly up to 641.7 and 561.4 mgg−1, respectively. The adsorption kinetics for both MB and RhB dyes were well-described by pseudo-second-order model that confirm the rate-limiting step might be the chemical adsorption. The dyes-loaded DCSA microparticles were regenerated by desorption process with numerous solvents and were reused five times without a significant decrease in their adsorption performance in first three cycles (especially for MB dye). The adsorption process was computationally simulated via Grimme dispersion correction (D3) as well as radial distribution function (RDF) techniques, and the results exhibited acceptable accordance with experimental data.