Synthesis, characterization and evaluation of novel HIPE hydrogels: Application for treatment of hazardous waste incineration plant effluent

Abstract

Novel high internal phase emulsion (HIPE) hydrogels were prepared by oil-in-water emulsion copolymerization of 2-hydroxyethyl methacrylate (HEMA) and N-isopropylacrylamide (NIPAm) in the presence of N,N′-methylene-bis-acrylamide (MBAm) as a crosslinker. Poly(ethylene oxide) based macroinimer was also used as an additional co-surfactant and co-crosslinker. The amount of NIPAm and macroinimer was varied to optimize composition of the hydrogels which sequentially enhanced swelling and metal ion binding capabilities. Swelling properties of all HIPE hydrogels were investigated at different temperatures with a maximum swelling percentage value of ∼2100% determined at 25 °C. Young’s modulus (E) of HIPE hydrogels which is a critical property for understanding their mechanical bevaiors was also calculated and the value increased from 5 to 13 MPa by increasing macroinimer amount. Finally, the use of the prepared HIPE hydrogels in a process to identify the best fitting hydrogel composition was applied as binding materials for the recovery of heavy metals ions such as Pb2+, Cu2+ and Hg2+ from hazardous waste incineration plant effluent. Results deduced a decrease in heavy metal ion binding capacity with increasing temperature in the studied range from 25 °C to 40 °C. Furthermore, heavy metal ion removal based on Venturi scrubber and physicochemical (P/C) plant effluent as wastewater was determined and the maximum binding capacities of the hydrogels were in the magnitude of Cu2+≅ Hg2+ > Pb2+ and Cu2+ > Pb2+ > Hg2+ for Venturi scrubber and P/C plant effluent, respectively.