NEW IRON CONTAINING HYBRID SILICATES FOR THE SELECTIVE REMOVAL OF ARSENIC OXYANIONS FROM CONTAMINATED WATER

Abstract

A series of hybrid silicates containing iron oxides was synthesized via loading with hydrated iron oxide species (HFO) using a post precipitation mechanism from aqueous solution using different amounts of iron into the silica. The obtained materials were characterized by XRD, SEM, TEM, FTIR and low temperature nitrogen sorption. XRD analysis confirmed that HFO- Si was amorphous and iron oxide crystals in the silica cannot be detected due to both the lower size of HFO and the probability that occupying interstitial positions inside the silicate matrix. However, TEM image showed the presence of nano-sized HFO located inside the silicate matrix. The adsorption properties and selective efficiency of the synthesized materials were exam�ined in the removal of As (V) and As (III) species from contaminated water under different experimental conditions as well as in the presence of competing anions. The increasing iron loading enhanced the arsenic adsorption capacity of HFO-Si and the maximum arsenic removal was found to be 623 mg Fe/g silica after five successive loading times. The synthesized materials possess a unique adsorption capacity and their adsorption capacity reaches 303 mg As/g HFO-Si. Adsorption isotherm data for As (V) on HFO-Si fitted well the Langmuir equation. In addition, the intraparticle diffusion models fitted the experimental kinetic data, suggesting that the rate limiting step of adsorption is most probably diffusion of arsenic ions into pores. Further�more, the use of HFO-Si in column run and its easy regeneration makes it more sustainable to reuse several times to reduce the volume of arsenic laden waste.