Antimony(V) removal from water by hydrated ferric oxides supported by calcite sand and polymeric anion exchanger

We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides （HFOs） using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents （denoted as HFO-201 and IOCCS） were employed for Sb（V） removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb（V） removal by both composites, while increasing temperature from 293 to 313 K only improved Sb（V） uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb（V） than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3 would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for 1OCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb（V） adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb（V） adsorption by both hybrids was attributed to the inner sphere complexation of Sb（V） and HFO, and Ca（II） induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb（V） in the synthetic water could be effectively removed from 30 μg/L to below 5μg/L （the drinking water standard regulated by China）, and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201.

Synthesis of novel hydrated ferric oxide biochar nanohybrids for efficient arsenic removal from wastewater

Hydrated ferric oxide(HFO)has high adsorption efficiency for As(Ⅲ).However,its high self-aggregation usually reduces the efficiency and limits the scaledup application.Herein,biochar(BC),with large surface area and amounts of surface functional groups was used to tune the loading and distribution of HFO to prepare an efficient adsorbent(HFO/BC)via in-situ synthesis method.The influence of the mass ratio of iron salt to BC on HFO/BC morphology was investigated,and the mechanism was discussed.The results showed that novel HFO was formed and distributed uniformly on the surface of BC when the mass ratio of iron salt to BC was 5:1.The adsorption kinetics and isotherms studies show that the novel HFO/BC(5:1)composite can fast treat As(Ⅲ)with a high adsorption capacity of 104.55 mg·g^(-1),indicating that it is a potential material for removing arsenic from polluted water.

Surface chemistry of polymer-supported nano-hydrated ferric oxide for arsenic removal: effect of host pore structure

Immobilization of hydrous ferric oxide(HFO) particles inside solid hosts of porous structure is an important approach to improve their applicability in advanced water treatment such as arsenic and heavy metal removal. Here, we fabricated three polystyrene(PS)-based nano-HFOs and explored the effect of host pore structure on the surface chemistry of the immobilized HFOs. Potentiometric titration of the hybrids and surface complexation modeling of their adsorption towards arsenite and arsenate were performed to evaluate the surface chemistry variation of the loaded HFOs. Polymer hosts of higher surface area and narrower pore size would result in smaller particle size of HFOs and lower the value of the point of zero charge. Also, the site density(normalized by Fe mass) and the deprotonation constants of the loaded HFOs increased with the decreasing host pore size. Arsenite adsorption did not change the surface charge of the loaded HFOs, whereas arsenate adsorption accompanied more of the negative surface charges. Adsorption affinity of both arsenic species with three HFO hybrids were compared in terms of the intrinsic surface complexation constants optimized based on the adsorption edges. HFO loaded in polystyrene host of smaller pore size exhibits stronger affinity with arsenic species.

Validation of polymer-based nano-iron oxide in further phosphorus removal from bioeffluent： laboratory and scaled- up study

The efficient removal of phosphorous from water is an important but challenging task. In this study, we validated the applicability of a new commercially available nanocomposite adsorbent, i.e., a polymer-based hydrated ferric oxide nanocomposite （HFO-201）, for the further removal of phosphorous from the bioefftuent discharged from a municipal wastewater treatment plant, and the operating parameters such as the flow rate, temperature and composition of the regenerants were optimized. Labora- tory-scale results indicate that phosphorous in real bioeffluent can be effectively removed from 0.92 mg· L^-1 to 〈 0.5 mg· L^-1 （or even 〈 0.1 mg·L^-1 as desired） by the new adsorbent at a flow rate of 50 bed volume （BV） per hour and treatable volume of 3500-4000BV per run. Phosphorous removal is independent of the ambient temperature in the range of 15℃-40℃. Moreover, the exhausted HFO-201 can be regenerated by a 2% NaOH ＋ 5% NaC1 binary solution for repeated use without significant capacity loss. A scaled-up study further indicated that even though the initial total phosphorus （TP） was as high as 2 mg·L^-1, it could be reduced to 〈 0.5 mg·L^-1, with a working capacity of 4.4-4.8 g·L^-1 HFO- 201. In general, HFO-201 adsorption is a choice method for the efficient removal of phosphate from biotreated waste effluent.