In the present study a novel technique was proposed to prepare a polymer-supported hydrated ferric oxide (D201-HFO) based on Donnan membrane effect by using a strongly basic anion exchanger D201 as the host material and FeCl3-HCl-NaCl solution as the reaction environment. D201-HFO was found to exhibit higher capacity for arsenic removal than a commercial sorbent Purolite ArsenX. Furthermore, it presents favorable adsorption selectivity for arsenic removal from aqueous solution, as well as satisfactory kinetics. Fixed-bed column experiments showed that arsenic sorption on D201-HFO could result in concentration of this toxic metalloid element below 10 μg/L, which was the new maximum concentration limit set recently by the European Commission and imposed by the US EPA and China. Also, the spent D201-HFO is amenable to efficient regeneration by NaOH-NaCl solution.

A hydrophilic hyper-cross-linked polymer resin NDA-150 was developed to remove 1-naphthol from the contaminated waters. The sorption performance of 1-naphthol on NDA-150 was explored and compared with that on the commercial hydrophobic resin XAD-4. The sorption rates of 1-naphthol onto both of the two resins obey the pseudo-second-order kinetics, and are limited by the successive steps of film diffusion and intraparticle diffusion. The greater sorption rate on XAD-4 than NDA-150 is probably due to the larger average pore diameter of XAD-4. All the adsorption isotherms can be represented by Langmuir equation. The larger capacity and stronger affinity ofNDA-150 than XAD-4 probably result fromthe abundant microporous structure and polar groups of NDA-150. In aqueous phase hydrophobic XAD-4 adsorbs 1-naphthol driven principally by enthalpy change, while the adsorption onto hydrophilic NDA-150 driven mainly by entropy change. The breakthrough and the total sorption capacity of NDA-150 to 1-naphthol were obtained to be 1.10 and 1.58mmolmL−1 resin at 293K, respectively. Nearly 100% regeneration efficiency for the resin was achieved by ethanol at 313K.

Adsorption is one of the most widely applied techniques for environmental remediation. Its kinetics are of great significance to evaluate the performance of a given adsorbent and gain insight into the underlying mechanisms. There are lots of references available concerning adsorption kinetics, and several mathematic models have been developed to describe adsorption reaction and diffusion processes. However, these models were frequently employed to fit the kinetic data in an unsuitable or improper manner. This is mainly because the boundary conditions of the associated models were, to a considerable extent, ignored for data modeling. Here we reviewed several widely-used adsorption kinetic models and paid more attention to their boundary conditions. We believe that the review is of certain significance and improvement for adsorption kinetic modeling.

Hydrated ferric oxide-loaded hybrid sorbents are of considerable concern for arsenic removal from waters. In the current study, several nanosized hydrated ferric oxide (HFO)-loaded polymer sorbents were prepared and assayed to examine the effect of HFO loadings on arsenate sorption from aqueous solution. Batch and column sorption studies showed that the sorption capacity of arsenate increased with the increase of HFO loadings from 3 to 15% (in Fe mass); however, a further increase in the HFO loadings resulted in a dramatic decrease of the sorption capacity. At relatively low arsenate levels (e.g., <1mg/L), sorbents with lower HFO loadings exhibited higher distribution coefficients (Kd) than others, implying that HFO loaded at a relatively lower level exhibits stronger sorption affinity toward arsenate than the larger one. However, at relatively high arsenate levels, the sorbent with HFO loading of 15% displayed the highest sorption capacity. Additionally, all the exhausted sorbents are amenable to an efficient regeneration by a mixed NaOH-NaCl solution irrespective of their HFO loadings. The results obtained in the current study may serve as a reference for preparation of other hybrid sorbents with similar structures, i.e., composites of nanosized metal (hydro)oxide particles and porous substrates.

In the present study amorphous and crystalline zirconium phosphate (ZrP) were synthesized to explore their different behavior towards lead sorption. Both sorbents were characterized by X-ray diffraction (XRD), pH-titration and X-ray photoelectron spectroscopy (XPS). Lead sorption onto both sorbents was found to be pH-dependent due to the ion-exchange mechanism. Sorption isotherms onto both sorbents can bewell correlated by Langmuir model. By comparison with crystalline ZrP, the amorphous one exhibited more favorable sorption of lead ion particularly in terms of high capacity and selectivity, as indicated by the qm values from Langmuir model (1.50mequiv./g for amorphous ZrP and 0.20mequiv./g for crystalline ZrP) and the distribution coefficients even several orders higher than crystalline ZrP when calcium ion coexisted at a high level in solution. Besides, rapid sorption kinetics were observed for both sorbents, and both lead-laden sorbents were amenable to an efficient regeneration by dilute HCl solution. Results indicated that amorphous ZrP can be selected as an ideal inorganic exchanger in the preparation of inorganic-polymer composites for heavy metals removal from water.