Kaolinite adsorption-regeneration system for dyestuff treatment by Fenton based processes

Highlights: • Kaolinite proved to be a viable low cost adsorbent in the removal of dye from wastewater. • Feasible regeneration of spent adsorbent by Fenton techniques using different solid:liquid ratios • Adsorption-degradation cycles were successfully carried out. • No alteration of the kaolinite was detect after the successive cycles. The regeneration and reuse of adsorbents is a subject of interest nowadays in order to reduce the pollution and the wastes generated in the adsorption wastewater treatment. In this work, the regeneration of the spent kaolinite by different advanced oxidation processes (Fenton, electro-Fenton and electrokinetic-Fenton) was evaluated. Initially, it was confirmed the ability of a low cost clayey material, kaolinite, for the adsorption of model dye such as Rhodamine B showing Freundlich isotherm fitting. Then, the regeneration and consequent degradation of the pollutant in the adsorbent by Fenton based processes was carried out. The role of different parameters affecting the regeneration process (H₂O₂:Fe^{2 +} ratio, liquid:solid ratio) were evaluated. Working at 100:1 H₂O₂:Fe^{2 +} ratio and 30 min near complete dye removal (around 97%) from kaolinite was obtained by Fenton treatment. After that, a two-stage treatment for adsorption-regeneration was evaluated during five treatment cycles demonstrating its viability for regeneration of the adsorbent through dye degradation. Based on the successful application of Fenton technique, the improvement of the treatment by electro-Fenton and electrokinetic-Fenton were studied for different solid:liquid ratios achieving satisfactory regeneration values.