Study of the adsorption/desorption of MB dye solution using bentonite adsorbent coating

Re-usability of exhausted or spent adsorbent in water treatment plant is became a complicated issue. In this regard, exhausted bentonite adsorbent has been employed for desorption/regeneration using combined effect of heating and solvent regeneration method. Exhausted adsorbent has been characterized using FTIR, and SEM analyses. The results of regeneration study reveal effective desorption of methylene blue (MB) dye up to seven successive cycles. Among different solvents (aqueous solution of hydrochloric acid, ethanol, acetone, propanol, nitric acid, water, NaCl and NaOH), significant desorption of MB (70 %) was achieved using aqueous HCl solution. To optimized maximum desorption of MB, different physico-chemical parameters such as temperature, initial dye concentration, contact time and lifespan of adsorbent have been studied. In addition, desorption isotherm and desorption kinetics were also found to be fitted with Sips isotherm (R-2 = 0.995) and second-order kinetics models (R-2 = 0.990), respectively. Moreover, chemically treated adsorbent (Paintosorp (TM)) can be effectively used up to seven adsorption/desorption cycles.