Remediation of organic and inorganic arsenic contaminated groundwater using a nanocrystalline TiO2-based adsorbent
2009
Jing, Chuanyong | Meng, Xiaoguang | Calvache, Edwin | Jiang, Guibin
A nanocrystalline TiO₂-based adsorbent was evaluated for the simultaneous removal of As(V), As(III), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in contaminated groundwater. Batch experimental results show that As adsorption followed pseudo-second order rate kinetics. The competitive adsorption was described with the charge distribution multi-site surface complexation model (CD-MUSIC). The groundwater containing an average of 329 μg L⁻¹ As(III), 246 μg L⁻¹ As(V), 151 μg L⁻¹ MMA, and 202 μg L⁻¹ DMA was continuously passed through a TiO₂ filter at an empty bed contact time of 6 min for 4 months. Approximately 11 000, 14 000, and 9900 bed volumes of water had been treated before the As(III), As(V), and MMA concentration in the effluent increased to 10 μg L⁻¹. However, very little DMA was removed. The EXAFS results demonstrate the existence of a bidentate binuclear As(V) surface complex on spent adsorbent, indicating the oxidation of adsorbed As(III). A nanocrystalline TiO₂-based adsorbent could be used for the simultaneous removal of As(V), As(III), MMA, and DMA in contaminated groundwater.
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