Adsorption properties and mechanism for Fe(III) with solvent impregnated resins containing HEHEHP

Three solvent impregnated resins (SIRS) were first prepared using two types of nonreactive polystyrene-divinylbenzene polymers (HZ818 and HZ830) and one type of reactive weak basic ion exchange resin (D301) as supports and HEHEHP (2-ethylhexyl phosphonic acid mono(2-ethylhexyl) ester) as the extractant. Then the first two prepared SIRs were coated by poly-vinyl alcohol (PVA)-H3BO3 to improve their stability. The two types of coated SIRs were called HZ818-CSIR and HZ830-CSIR, and the third type of SIR was called D301-SIR. The three adsorbents were characterized by scanning electron microscopy and infrared spectrometer. The adsorption properties of iron (III) with three adsorbents were studied by batch method from sulfuric acid medium in the range of pH 0.9-1.9. The optimal pH values of all adsorbents were found at 1.5, and the saturated adsorption capacities of HZ818-CSIR, HZ830-CSIR and D301-SIR were determined as 16.7 mg.g(-1), 15.9 mg.g(-1) and 25.6 mg.g(-1) at 298 K, respectively. The adsorption isotherms were found to be fitted with Langmuir isotherms. The adsorption kinetic behaviors of HZ818-CSIR and HZ830-CSIR were fitted with pseudo-second-order kinetic model, while that of D301-SIR with Lagergren first-order kinetic model. The adsorption mechanisms of the three adsorbents were investigated with methods of saturation, equimolar series change and infrared adsorption spectra. It was found that the adsorption mechanism of Fe(III) with HZ818-CSIR and HZ830-CSIR could be deduced as cation exchange between Fe3+ and H+ from P-OH of HEHEHP accompanied with coordination between Fe(III) ion and the phosphoryl oxygen from HEHEHP. While for the D301-SIR, only a cation exchange between Fe3+ and H+ from P-OH of HEHEHP can be proposed. (C) 2013 Elsevier B.V. All rights reserved.