Arsenic Adsorption by TiO2 Nanoparticles Under Conditions Similar to Groundwater: Batch and Column Studies

Abstract

Nano-sized TiO2 particles containing anatase and rutile were applied to arsenic removal from water in natural groundwater conditions in the batch and column experiments. Arsenic concentrations were 200 µg L−1 and the pH range was 6–8.5 (similar to groundwater conditions). The results showed that anatase and rutile could adsorb 95.5% and 63.5% of arsenic in a solution after 60 min, respectively. In both adsorbents, arsenic adsorption was increased by increasing the adsorbent concentration. Increasing pH results increased adsorption in rutile more than anatase. The maximum adsorption capacity of 2.58 mg g−1 and 1.86 mg g−1 were calculated for anatase and rutile, respectively at the adsorbent concentration of 3 g L−1. Isotherm studies showed Freundlich model was more valid to the empirical adsorption data for both nanoparticles. The kinetics of the adsorption processes fitted well the pseudo-first-order adsorption model. To investigate the dynamic sorption, column study was carried out with fine and coarse silica sand porous media. According to the batch experiments, only anatase nanoparticles were injected into the column as an adsorbent at different doses. Breakthrough curves (BTC) showed the best efficiency of arsenic removal can be obtained by an adsorbent dose of 8 g L−1 in the fine sand column.