Highly Efficient Cationic Surfactant Functionalized Alginate Hydrogel for Perfluorooctanoic Acid Adsorption: Optimization through Response Surface Methodology and Performance Evaluation for Aqueous Media
M.A. Shaikh, Tabish Nawaz
Abstract
This study presents a sustainable treatment of perfluoroalkyl or polyfluoroalkyl substances in aquatic environments, focusing on perfluorooctanoic acid (PFOA), through adsorption. The study employs response surface methodology to assess the influence of the adsorbent’s synthesis parameters─specifically, quantities of calcium, sodium alginate, and cetyltrimethylammonium bromide (CTAB)─on the adsorption efficiency of alginate hydrogel. The optimally synthesized hydrogel exhibits an average PFOA removal efficiency of 94.8 ± 2.1% at a 50 mg/L PFOA concentration. The experimental data for the hydrogel closely align with the pseudo-second-order rate kinetic model ( R 2 = 0.97) and the Sips isotherm model ( R 2 = 0.99), with a maximum possible adsorption capacity of 382.1 mg/g. Hydrogen bonding and electrostatic and hydrophobic interactions are identified as the primary mechanisms driving PFOA removal by the hydrogel. The hydrogel exhibits high values of selectivity parameters, indicative of its preference for PFOA even in the presence of a background river water matrix. A regenerant solution of 50% ethanol with 0.25% ammonium hydroxide demonstrates ∼80% regeneration capability, although it falls to ∼70% after three adsorption–desorption cycles. This study provides insights into the performance of CTAB-functionalized alginate hydrogel, showcasing its high uptake capacity and selectivity for PFOA.