Adsorption of Methylene Blue dye and Cu(II) ions on EDTA-modified bentonite: Isotherm, kinetic and thermodynamic studies

Dyes and metals are hazardous pollutants commonly found in industrial wastewaters requiring complex and expensive removal technologies. This study investigated the potential of ethylenediaminetetraacetic acid-modified Philippine bentonite (EMB) as a low-cost adsorbent material for the removal of Methylene Blue dye (MB) and copper ions (Cu(II)) from aqueous solutions. Batch adsorption experiments showed that EMB has superior adsorption capacity compared to the unmodified bentonite, with an enhancement of up to 40% for MB and more than 100% for Cu(II). The adsorption capacity of EMB improved with increasing solution pH and contact time and decreased with higher solution temperature and higher salt concentration in solution. The Langmuir isotherm model was found to best describe MB and Cu(II) adsorption on EMB with maximum capacity of 160 and 27 mg g−1, respectively. The pseudo-second order kinetic model best fit the experimental data with R2 > 0.99. Lastly, the thermodynamic study confirmed that the adsorption process was spontaneous, exothermic and reversible.