Development of zirconia nanoparticle-loaded hydrogel for arsenic adsorption and sensing

A novel zirconia nanoparticle-loaded synthetic polymeric hydrogel was developed as an adsorbent and quartz crystal microbalance (QCM) sensor for arsenic in an aqueous solution. The bulk composite hydrogel was prepared by polymerizing a pre-gel aqueous solution containing N,N-dimethylacrylamide as the primary monomer, a crosslinking monomer, an initiator, and commercially available zirconia nanoparticles. The hydrogel-coated QCM sensor was simply fabricated by polymerizing the pre-gel aqueous solution onto the surface of a gold electrode on a quartz crystal. The hydrogel selectively adsorbed As(III) and As(V), and the adsorption equilibrium followed the Langmuir-type isotherm. The amount of arsenic adsorbed was higher in acidic and neutral solutions and decreased with an increase in pH. Moreover, the hydrogel adsorbed/desorbed arsenic repeatedly via the regeneration process using a NaOH aqueous solution. Furthermore, the investigation of the oscillation behavior of the hydrogel-coated QCM sensor revealed that the resonance frequency shift increases with an increase in arsenic concentration, which indicates that the adsorption of arsenic onto the sensor follows a Langmuir-type isotherm. The hydrogel-coated QCM sensor could detect arsenic with high selectivity and sensitivity even in the presence of Na(I), Mg(II), and Ca(II) ions. Thus, we successfully developed the world's first QCM sensor for arsenic.