Preparation of polyacrylamide cryogels containing iron hydroxide oxide nanoparticles by particle addition method and their arsenic adsorption properties

Cryogel is super-macroporous material prepared by freezing of polymer or monomer solution at low temperature. The hybrid material of cryogels and iron hydroxide oxide(FeOOH) nano-particles, which have affinity to arsenic, are expected as a safe removal adsorbent of arsenic ions from aqueous solutions. In this study, polyacrylamide(PAA) cryogels containing FeOOH particles were prepared by freezing the monomer solution of acrylamide cross-linker N,N-methylene bis(acrylamide) dispersing the particles, which were prepared by mixing of iron(III) chloride solution (FeCl3) and sodium hydroxide aqueous solution, and polymerizing initiated by N,N,N',N'-tetramethyl ethylene diamine and ammonium peroxodisulfate at sub-zero temperatures. The particles added were observed on a whole of the cryogel wall. The polyacrylamide cryogel containing FeOOH particles successfully adsorbed a large amount of As(V) at both low and high concentrations. The adsorption property showed a Brunauer-Emmett-Teller(BET)-like isotherm. The adsorption amount of As(V) per weight of the FeOOH particles in the cryogel increased with a decrease in the amount of FeOOH in the cryogel. At the low concentration of As(V) in the aqueous solution, the adsorption amount of As(V) with the cryogel was not affect by pH values. On the other hand, at high concentration of the As(V), the adsorbed amount of As(V) with the cryogel decreased with an increase in the pH value higher than 6. The FeOOH particles entrapped in the cryogel wall prepared by the particle addition method was an amorphous in which that had higher adsorption capacity of As(V) than that having higher crystallinity.