Rubber Foam Incorporating Activated Carbon and TiO2 for the Adsorptive Removal of Rice Starch Wastewater

White rice starch is a major pollutant in wastewater from rice noodle production. This study developed a composite adsorbent (RFAcTD) by incorporating activated carbon (Ac) and TiO 2 (TD) into rubber foam (RF) at varying Ac:TD ratios (4:1, 2.5:2.5, and 1:4). Adsorption behavior followed the Langmuir isotherm for RFAcTD (4:1 and 2.5:2.5), while the TiO 2 -rich RFAcTD (1:4) fit the Freundlich model, indicating multilayer adsorption. Thermodynamic analysis via the Van’t Hoff plot yielded a ΔH of -83.82 kJ/mol, confirming an exothermic adsorption mechanism driven by strong hydrogen bonding between starch hydroxyl groups and surface functionalities on the activated carbon and TiO 2 of the RFAcTD adsorbent. DFT calculations confirmed that rice starch forms a stable complex with the modified rubber (RFAcTD) through hydrogen bonding, with interaction energies of -97.72 kJ/mol in the gas phase and -71.86 kJ/mol in the aqueous phase. Application to real wastewater from Thai rice noodle factories demonstrated effective starch removal, supporting the potential of RFAcTD for practical wastewater treatment.