Preparation and characterization of homopolymer polyacrylonitrile-based fibrous sorbents for arsenic removal

This research investigated the modification of homopolymer polyacrylonitrile (PAN) fibers for use as an adsorbent for removing arsenic from drinking water. Fibers were chemically modified and cross-linked using combinations of hydrazine hydrate and sodium hydroxide (NaOH) before being loaded with ferric hydroxide using two different iron loading procedures. Effects of reagent concentrations and reaction times on degree of chemical modification and fiber properties were investigated using Fourier transform infrared spectroscopy and ion-exchange measurements. Arsenate adsorption was a function of both the iron loading and the properties of the underlying fiber. For fibers treated with only a single reagent, both Fe3+ and arsenate adsorption could be understood in terms of ion-exchange properties of the fiber surfaces. However, for fibers treated with both hydrazine and NaOH, the ion-exchange properties of the surface could not explain the Fe3+ and arsenate adsorption behavior. The best arsenate removal performance was obtained using the simplest pretreatment procedure of soaking in 10% NaOH at 95°C for 90min, followed by precipitation coating of ferric hydroxide. This simple preparation procedure involves only two commonly available and inexpensive reagents and can be carried out without any specialized equipment. This suggests that adsorbents based on inexpensive homopolymer PAN fabric may be produced in developing areas of the world where commercial products may not be available.