Amine contaminants removal using alginate clay hybrid composites and its effect on foaming

Heat stable salts such as total organic acids (TOA) and heavy metals are well known contaminants in the acid gas removal systems operating using alkanolamines such as methyldiethanolamine (MDEA, 50 wt%). Decontamination of TOA and heavy metals from lean MDEA always remain as a challenge to the gas industry, as accumulation of TOA deteriorates the solvent quality, weakens the absorption capacity and enhances foaming problems leading to huge loss of MDEA and presence of heavy metals results in corrosion and fouling of equipment. Equilibrium batch adsorption were carried out using calcium alginate clay hybrid composites (CAH) containing sepiolite and bentonite for assessing the sorption performance of TOA and heavy metals such as chromium and iron from industrial lean MDEA solutions. The physiochemical properties of the adsorbent were elucidated using SEM, EDX and FTIR analysis. The effects of operational parameters such as amount of sorbent, contact time and temperature on the sorption capacity were also investigated. Kinetics results indicated that the chemisorption nature. The pseudo-second order model gave the best fit. The adsorption efficiency increased with increasing the temperature. Adsorption followed type VI isotherm according to the IUPAC classification, with sorption taking place in different stages. Regeneration studies revealed that 4% CaCl ₂ acts as an effective eluting agent and no reduction in capacity was observed even after 3 cycles of regeneration. Foaming studies carried out with treated lean MDEA confirmed the reduction in foam of MDEA solutions owing to the effective removal of foam creators such as TOA from lean MDEA by CAH composites. A 15.8% reduction in TOA content was found to decrease the foam height by 37.5%. Thus, CAH composites containing bentonite and sepiolite are having the potential to reclaim industrial lean MDEA solutions.