Sustainable approach for removal of reactive dyes: optimization of process performance and sorbent regeneration

We investigated the removal of the reactive dye Remazol Red from segregated dye bath with an integrated physical-biological approach combining easy applicability and fast kinetics of the sorption process with intrinsic sustainability of biological treatments. The proposed process consists in a first step dye removal by sorption on a cheap commercial polymer (Hytrel 8206) followed by anaerobic polymer bioregeneration. Excellent dye removals were achieved (up to 100%) under acidic conditions with fast kinetics (in most cases, 4 h are sufficient to reach efficiencies >= 80%). Experimental sorption data were well correlated with the Freundlich isotherm and pseudo-first-order kinetic model. The sorption process was optimized with response surface methodology. Practically complete removal was achieved with pH of the solution, initial dye concentration and polymer-to-water ratio equal to 4, 50 mg/L and 8.03% v/v, respectively. High desorption performance under neutral conditions makes Hytrel suitable for bioregeneration in a two-phase partitioning bioreactor. Polymer bioregeration reached 82% efficiency with the added value of achieving effective biodegradation (> 50% in 4 days) of the dye desorbed from the polymer. The study demonstrated the two-step process feasibility, which is characterized by the advantage of employing a cheap commercial polymer and has the potential of achieving complete dye mineralization.