Swelling and dye sorption studies of acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid/bentonite highly swollen composite hydrogels

Abstract

Water uptake and the sorption properties of polyelectrolyte composite hydrogels made by the polymerization of acrylamide (AAm) with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and a clay such as bentonite (Bent) were investigated as a function of composition to find materials with swelling and dye sorption properties. Highly swollen AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with AMPS as comonomer and a multifunctional crosslinker such as ethylene glycol dimethacrylate (EGDMA). FT-IR analyses were made. Swelling experiments were performed in water and dye solution at 25oC, gravimetrically. Highly swollen AAm/AMPS and AAm/AMPS/Bent hydrogels were used in experiments on sorption of water–soluble monovalent cationic dye such as Lauths violet “LV, (Thionine)”. Swelling of AAm/AMPS hydrogels was increased up to 2282–12,603% in water and 921–3575% in LV solutions, while AAm hydrogels swelled 927% in water and swelling of AAm/AMPS/Bent hydrogels was increased up to 3225–15,421% in water and 1360–4189% in LV solutions, while AAm/Bent hydrogels swelled 828% in water. Some swelling kinetic and diffusional parameters were found. Water and LV diffusion into hydrogels was found to be non-Fickian in character. For sorption of cationic dye, LV into AAm/AMPS and AAm/AMPS/Bent hydrogel was studied by batch sorption technique at 25oC. AAm/AMPS and AAm/AMPS/Bent hydrogels in the dye solutions showed coloration. The amount of the dye sorbed per unit mass removal efficiency and partition coefficient of AAm/AMPS and AAm/AMPS/Bent hydrogels was investigated. The influence of AMPS content in hydrogels to sorption was examined.