Coupled adsorption-phytoremediation treatment of cellulose-reactive blue dye in a sustainable multi-step pilot-scale...

A single-step dye removal strategy from wastewater is inadequate for concentrations above 100 mg/L. In order to address this limitation, the adsorption of high dye concentrations followed by phytoremediation is a potential approach for the treatment of dye-contaminated wastewater. This combined method utilizes physical adsorption and biological processes to remove dyes from wastewater. Herein, we investigated a pilot-scale multi-step cascaded process where batch adsorption and fixed-bed column adsorption were combined with phytoremediation to remove cellulose-reactive blue dye at 200 to 500 mg/L concentrations. The batch adsorption utilized low-cost water hyacinth root powder (WHRP) bioadsorbent having 670 m²/g surface area, whereas the fixed-bed column adsorption used sand having a surface area of 75 m²/g. The phytoremediation process utilized water hyacinth plants in a series of ponds. The effluent from one unit is fed to the next until the dye is removed to more than 98% for all concentrations considered in this study. Pilot-scale experimental data fitting to adsorption isotherms and kinetics were performed to gain insight into the pilot-scale adsorption mechanism. The fixed-bed sand column adsorption was conducted at different inlet dye concentrations, flow rates, and bed heights. The breakthrough curves were fit to the Thomas, Yoon-Nelson, and Bohart-Adams models. The effluent from the fixed-bed column was transferred to phytoremediation ponds, where complete dye removal was achieved. Overall, data collectively presented in this study demonstrated that the combined adsorption and phytoremediation approach offers a potential solution for the remediation of high dye concentration in wastewater, providing an effective and sustainable treatment option.