Synthesis and swelling properties of copolmeric acrylamide-crotonic acid superabsorbents

Abstract

Superabsorbent polymers of acrylamide (AAm)/crotonic acid (CA) were synthesized by foamed polymerization in the aqueous solution of AAm with CA as a comonomer, initiated by an initiator couple of ammonium persulfate and N,N,N’N’-tetramethylenediamine. The crosslinking agent N,N’-methylene bisacrylamide, the foaming agent sodium bicarbonate, and a foam stabilizer, a triblock copolymer of polyoxyethylene/polyoxypropylene/polyoxethylene, were used in the polymerization. The influences of the relative content of CA, crosslinking agent, initiator, reaction temperature and agitation rate on the swelling properties of the superabsorbent polymer systems were examined. The functional groups of synthesized copolymer were investigated by Fourier Transform Infrared Spectroscopy, surface morphology by scanning electron microscopy, and electrochemical characteristic by cyclic voltammetry technique. The efficiency of synthesized copolymer on removing dye such as Basic Blue 41 (cationic dye) at different pHs and Direct Blue 85 (anionic dye) was determinated using UV-Vis spectrophotometry. The superabsorbent polymer synthesized with an AAm/CA ratio of 98:2 by mole, 0.5% wt. of N,N’-methylene bisacrylamide and 1% wt. of ammonium persulfate at 250 rpm and 50°c for 30 min of polymerization time produced the highest water absorption of 211±9 times its dried weight and can absorb water up to 162±4 g per g of the dry copolymer within 10 min. The AAm/CA copolymer can only adsorb cationic dye upto 70% of its original concentration.