Hydrogel-coated Fe.sub.3O.sub.4 nanoparticles as an efficient heterogeneous Fenton catalyst for degradation of phenol

Fe.sub.3O.sub.4 magnetic nanoparticles with carboxymethyl cellulose-g-poly(acrylic acid-co-acrylic amide) hydrogel coating (Fe.sub.3O.sub.4@hydrogel) were prepared by a coprecipitation method followed by an in situ graft copolymerization. Results of various characterization techniques indicated that hydrogel materials were successfully coated on the Fe.sub.3O.sub.4 surface with a weight percent of 17.5% and the Fe.sub.3O.sub.4@hydrogel has an average size of 10 nm and could be easily collected with the aid of an external magnet. Fe.sub.3O.sub.4@hydrogel was used as heterogeneous catalyst to degrade phenol in a Fenton-like reaction. Factors such as initial solution pH, H.sub.2O.sub.2 concentration and catalyst dosage on the degradation efficiency of phenol were evaluated. Experimental results revealed that about 98.2% phenol and 80.4% chemical oxygen demand (COD) could be removed in 180 min under optimal conditions. Besides, Fe.sub.3O.sub.4@hydrogel presented effective phenol degradation at relatively wide pH values ranging from 3.0 to 5.0, and about 50% COD could be eliminated at pH 5.0. The improved catalytic performance of the synthesized catalyst might be ascribed to the pH-sensitive swelling, excellent dispersion, hydrophilicity and permeability of the polymer hydrogel coating. Besides, Fe.sub.3O.sub.4@hydrogel showed favorable catalytic stability and reusability with more than 55% of COD removal efficiency after three cycles.