Preparation, characterisation and sorptive properties towards noble metals of the resins from poly(vinylbenzyl chloride) copolymers

Polyethylenimine-Functionalized Corn Bract, an Agricultural Waste Material, for Efficient Removal and Recovery of Cr(VI) from Aqueous Solution

In this study, polyethylenimine-functionalized corn bract (PEI-CB) was first used to remove aqueous Cr(VI) via the "waste control by waste" concept. The results indicated that PEI-CB had an excellent performance for Cr(VI) removal and the maximum removal capacity was 438 mg/g. The adsorption of Cr(VI) was fitted to the Langmuir model, and kinetics of uptake could be described by a pseudo-second-order rate model well. Amine was proven to be the active center for Cr(VI) adsorption and partial reduction to Cr(III), while removal efficiency was enhanced at a lower pH value and higher temperature. Besides, nanosized Cr₂O₃ with a high purity was obtained by simple calcination of a Cr(VI)-laden adsorbent. Hence, this study provided a novel strategy for Cr(VI) wastewater remediation and pure Cr₂O₃ recovery. Prepared PEI-CB was then a promising alternative of low cost for replacement of the current expensive absorbent of removing Cr(VI) from wastewater from the view of sustainability.

Guanidylated hollow fiber membranes based on brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO) for gold sorption from acid solutions

Novel guanidylated hollow fiber membranes are prepared based on brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO) under mild reaction conditions. 1H-pyrazole-1-carboxamidine hydrochloride (HPCA) is employed for the guanidylation in aqueous solution at room temperature. The obtained guanidylated PPO hollow fiber membranes (GPPO HFMs) contain 0.31-0.95 mmol/g guanidyl groups and show high affinity to tetrachloroauric anions (AuCl(4)(-)) in acid solutions. For 0.1M HCl solution containing 57.8 mg gold/L, the sorption amount can get as high as 130 mg/g. Besides, the GPPO HFMs show preferable selectivity toward gold in multicomponent solution containing Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II). A system of comparison experiments involving the sorption behavior of GPPO HFMs and quaternary aminated HFMs are also performed. The results reveal that driving forces for the high adsorption of gold mainly involve complexation mechanism. Overall, the obtained GPPO HFM is a promising chelating material for the recovery of gold.

Polymer resins for recovery of valuable metals

Vinylbenzyl chloride/divinylbenzene gel copolymer beads have been modified using piperidine, hexamethyleneimine, piperazine, 1-(2-aminoethyl)piperazine, and N-cyclohexyl-1,3-propanediamine. These resins were then tested for the sorption of noble metal ions, namely, Re(VII), Pd(II), Pt(IV), and Au(III), from a 0.1 M HCl solution. The effect of these resins on the sorption of other coexisting ions, such as Cu, Ni and Fe, was also studied. Of the resins tested, resin 4 [1-(2-aminoethyl)piperazine groups] showed the highest sorption capacity for Pt(IV) and Re(VII) from single and multicomponent solutions, with the sorption of Pt(IV) from the multicomponent solution (Re, Au, Pd, Pt, Cu, Ni Fe) in 0.1 M HCl reaching 68 mg Pt/g.

Trends in Sorption Preconcentration Combined with Noble Metal Determination

Nowadays much attention is being paid to the determination of trace amounts of noble metals in geological, industrial, biological and environmental samples. The most promising techniques, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS) are characterized by high sensitivity. However, the accurate determination of trace noble metals has been limited by numerous interferences generated from the presence of matrix elements. To decrease, or eliminate, these interferences, the sorption preconcentration of noble metals is often used prior to their instrumental detection. A great number of hyphenated methods of noble metal determination using sorption preconcentration have been developed. This review describes the basic types of available sorbents, preconcentration procedures and preparations of the sorbent to the subsequent determination of noble metals. The specific features of instrumental techniques and examples of ETAAS, FAAS, ICP-AES, ICP-MS determinations after the sorption preconcentration of noble metals are considered. The references cited here were selected mostly from the period 1996 - 2006.