Efficient Arsenate Removal By Macroporous Anion Exchanger-Supported Nano-hydrated Zirconium Oxide (HZO)

It is a challenging task to employ HFO based adsorbent in solution of acidic pHs (e.g.,<3.0) or in the presence of organic ligands. Unfortunately, these scenarios are common in arsenic contaminated groundwater or industrial effluents. HZO is environmentally benign and is believed to be far more chemically stable in the presence of acid, organic ligands and oxidants than iron (hydro) oxides. On the other side, HZO based adsorbents exhibited excellent arsenic removal comparable to that of iron (hydro) oxides based ones.In this study, hydrous zirconium oxide (HZO)-originated nanocomposite adsorbent of excellent stability against pH variation and organic ligands was fabricated for efficient arsenate removal from water. The resultant adsorbent HZO-201 was obtained by encapsulating nanosized HZO particles inside a polystyrene anion exchanger D201. Negligible metal dissolution was observed from HZO-201 in solution of acidic pHs (to-1) and oxalate at high levels, while significant metal leaching occurred from a similar hydrated ferric oxide-based nanocomposite HFO-201of the same host. Arsenate adsorption by HZO-201 is a pH-dependent process with maximum capacity of 88.74 mg/g at pH 7.0 ±0.1, comparable to that of HFO-201 under similar conditions. As compared to sulfate, chloride, and bicarbonate, silicate and phosphate could strongly inhibit arsenate uptake by HZO-201. Fixed-bed adsorption tests indicated that arsenate in simulated groundwater could be effectively captured from 100 μg/L to<10 μg/L within 2600 BV (bed volume), and that in a real acidic mining effluent could be removed from 750 μg/L to< 50 μg/L within 2900 BV. The exhausted HZO-201 was also amenable to efficient regeneration with a binary NaCl-NaOH solution for repeated use without any significant capacity loss.