A new synthesis route of hydrothermally carbonized Na₂CO₃ activated bentonite-clay as a novel adsorbent for cadmium removal from wastewater

The study investigates the influence of the modification process on the structural properties of bentonite clay for the removal of Cadmium II (Cd) from electroplating wastewater. The work employs a novel process involving the combination of Na₂CO₃ activation, hydrothermal and/or carbonization leading to a successful preparation of a series of modified clay. The Na₂CO₃-Clay@HT-carbonized had better morphology and higher cation exchange capacity thereby exhibiting excellent performance for adsorptive removal of Cd in both batch and column experiment. At 1 min contact time q_e reached 84.8 mg/g and rapidly reached a maximum adsorption capacity of 307.87 mg/g at optimum conditions of concentration of 1400 mg/L, pH- 7 and Temperature of 40 °C in the batch study. In the column study, a q_e of 35.8 mg/g was attained by the Na₂CO₃-Clay@HT-carbonized. The Na₂CO₃-clay@HT-carbonized exhibited environmental adaptability showing a Cd removal in the presence of interfering ions from synthetic electroplating wastewater as well as maintaining an effective removal of Fe, Pb, Cu, Cr, and Zn suggesting that the modification process was successful. The kinetics and isotherms suggest that the data is well fitted to the pseudo second order, Elovic and Freundlich model respectively. In summary, the Na₂CO₃-clay@HT-carbonized has exhibited remarkable adsorption performance and also boasts of a simple modification process rendering it highly for applications in the removal of Cd from wastewater in both batch and column for treatment of electroplating wastewater.