Treatment of Lead-Contaminated Water Using Poly(2-Hydroxy 4-MethacryloyloxyBenzophenone): Adsorption Isotherms, Kinetics, and Thermodynamic Studies

Lead (Pb²⁺) is a pervasive, highly toxic pollutant that adversely affects human health and contaminates aquatic ecosystems through industrial discharges. This study evaluates the effectiveness of a novel material, poly(2-hydroxy4-methacryloyloxybenzophenone)(PHMB), for the removal of Pb⁺² from water. The monomer 2-hydroxy4-methacryloyloxybenzophenone (HMB) was synthesized and polymerized <i>via</i> free-radical polymerization to obtain the adsorbent PHMB. PHMB and HMB were characterized by spectroscopic techniques (FTIR,¹H and ¹³C NMR). Removal efficiency of Pb²⁺ from water samples was examined using UV-Visible spectroscopy. Results showed that optimal Pb²⁺ removal was achieved at pH 6 with a PHMB dosage of 0.75 g/L, and equilibrium was attained within 180 min. Isotherm analysis showed that the Freundlich model provided the best fit, indicating favorable multilayer adsorption of Pb²⁺, with a maximum adsorption capacity of 142.68 mg/g. The kinetic study revealed that the adsorption process was well-fitted by the pseudo-second-order kinetic model, indicating that chemisorption was the dominant adsorption mechanism. Additionally, thermodynamic data confirmed that the adsorption process was spontaneous and exothermic; the ΔG and ΔH values were −72 J/mol and −10kJ/mol, respectively. Furthermore, PHMB retained about 80% of its efficiency across multiple regeneration cycles; its reusability and high affinity for Pb²⁺ make it a strong candidate for sustainable practical water purification.