Synthesis of hydrogel based on acrylic acid and its application in the absorption of methyl orange from aqueous solutions

Poly(acrylic acid-co-acrylamide) PAM-AA hydrogel by solution polymerization of acrylic acid (AA) and acrylamide (AM) using ammonium persulfate (APS) as initiator and N',N-methylenebisacrylamide ( MBA) was prepared as a binder. PAM-AA was used to adsorb methyl orange from aqueous solutions. Factors affecting the absorption capacity such as absorption time, initial concentration of methyl orange, amount of superabsorbent hydrogel, pH value were investigated in detail and it was found that PAM-AA is very effective for removing methyl orange from its aqueous solutions. The equilibrium adsorption capacity was 359.89 mg/g at room temperature as initial. The concentration of methyl orange was equal to 3000 mg/liter. The mechanism of the adsorption process was also speculated. The study on the equilibrium adsorption isotherms showed that the adsorption was in accordance with the Langmuir and Freundlich model. Further investigation of the sorption kinetics showed that the sorption process was compatible with the pseudo-second order kinetic model.