Radiation synthesis and characterization of 2-hydroxyethyl-methacrylate- based hydrogels containing di- and tri-protic acid and its application on wastewater treatment

Radiation-crosslinked 2-hydroxyethylmethacrylate/citric acid (HEMA/CAc), 2-hydroxyethylmethacrylate/tartaric acid (HEMA/TA), and 2- hydroxyethylmethacrylate/succinic acid (HEMA/Sc) copolymers were prepared by using ⁶⁰Co γ-rays. The gel fraction yield and the swelling behavior of the prepared hydrogels were studied. It was shown that increasing irradiation doses was accompanied by an increase in yield of gel fraction and a decrease in swelling degree. The parameters of equilibrium swelling, maximum swelling, initial swelling rate, swelling exponent, and diffusion coefficient of the hydrogels were determined by studying the swelling behavior of the hydrogels prepared. It was seen that the equilibrium swelling degree increases as the content of acid increases, as a result of introducing more hydrophilic groups. When the hydrophilic polymer (acids) varies in the content range of40-80 mg, swelling exponents (n) decreases, thereby indicating a shift in the water-transport mechanism from the anomalous (non-Fickian)-type to the Fickian-type. Characterization and some selected properties of the prepared hydrogels were studied, and accordingly the possibility of its practical use in the treatment of industrial wastes such as dyes and heavy metals (Fe, Ni, Co, and Cu) were also studied. The effect of treatment time, pH of feed solution, initial feed concentration, and temperature on the dye and heavy metals uptake was determined. The uptake order for a given metal was HEMA/TA hydrogel > HEMA/CAc > HEMA/Sc hydrogel.