[show abstract][hide abstract] ABSTRACT: Phosphate amendments in calcareous lead (Pb)-contaminated soils to immobilize Pb may be hindered due to competition of Pb with calcium (Ca) that may inhibit the retention of Pb as a precipitation mechanism. This study explored the retention of Pb in a calcareous soil spiked and aged with 500mgkg(-1) Pb(2+) and amended with H2PO4(-). In addition, Ca(2+) was added immediately or three days before or after phosphate, after which ryegrass (Lolium perenne) was planted. Diethylene triamine pentaacetic acid (DTPA)-extractable Pb of the soils in which Ca was added immediately after phosphate was lower than those only amended with phosphate or when Ca was added three days before or after phosphate. The addition of Ca immediately after phosphate resulted in the greatest reduction of ammonia acetate-exchangeable Ca concentration, Olsen-P concentration, and carbonate phase Pb. Higher plant biomass yields were observed for the simultaneous P and Ca treatment. The results of the study demonstrate that co-added Ca and P may help reduce Pb availability by forming fresh Ca-P sorbent phases to retain Pb through an adsorption-substitution mechanism, which may play an important role in the sequestration of Pb in calcareous soils with soluble phosphate in addition to the mechanism of the direct precipitation as pyromorphite.
Journal of hazardous materials 08/2013; 262C:250-255. · 4.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: A new cloud point extraction (CPE) procedure for preconcentration of cadmium prior to the determination by flame atomic absorption spectrometry (FAAS) was developed. The method is based on the fact that cadmium could form hydrophobic ion-associated complex in the presence of iodide and methyl green (MG), and the hydrophobic ion-associated complex could be extracted into surfactant-rich phase. The main factors affecting CPE procedure, such as pH, concentration of KI, MG and surfactant, equilibrium temperature and incubation time, sample volume were investigated. Potential interference from co-existing ions was largely eliminated as most of co-existing ions can not form extractable ion-associated complex with iodide and MG. Under the optimum conditions, the limit of detection (3σ) and limit of quantity (10σ) were 0.90ngmL−1 and 3.0ngmL−1 for cadmium, respectively, and relative standard deviation was 4.2% (c=50ngmL−1, n=7). The proposed method was successfully applied to determination of cadmium in the certified reference rice sample (GBW08510) and food samples with satisfactory results.
[show abstract][hide abstract] ABSTRACT: Peanut shell was chemically modified with phosphoric acid and used as a solid phase extraction material for the determination
of trace amounts of Pb2+ and Cd2+ in food samples by flame atomic absorption spectrometry. The effect of pH, sample flow rate and volume, elution flow rate
and volume, and of potentially interfering ions on the recovery of the analytes were investigated. The results showed that
Pb2+ and Cd2+ can be adsorbed at pH6 and eluted with 1.5mL of 0.1mol L−1 HCl. Under the optimized conditions, the adsorption capacity of modified peanut shell was found to be 116.7mg g−1 and 37.5mg g−1 for Pb2+ and Cd2+, respectively. The limits of detection were as low as 2.3 and 0.2ngmL−1 for Pb2+ and Cd2+, respectively, with a theoretical concentration factor of 40. The analytical results for the certified reference tea sample
(GBW07605) were in a good agreement with the certified value. The method has also been applied to the determination of trace
Pb2+ and Cd2+ in tea, liquor and milk powder, and the recovery of Pb2+ and Cd2+ for spiked food samples was between 90 and 114%.
[show abstract][hide abstract] ABSTRACT: Soybean hull was chemically modified with citric acid and used as a solid phase extraction adsorbent for the determination of trace amounts of Cu(2+) in food samples by flame absorption spectrometry (FAAS). The effect of pH, sample flow rate and volume, elution flow rate and volume and co-existing ions on the recovery of the analyte were investigated. The results showed that Cu(2+) could be adsorbed on the modified soybean hull at pH 8.0 and eluted by 2.0 mL of 1.0 mol L(-1) HCl. Under the optimized conditions, the adsorption capacity of modified soybean hull was found to be 18.0 mg g(-1) for Cu(2+). The detection limit of the proposed method was 0.8 ng mL(-1) for Cu(2+) with an enrichment factor of 18. The analytical result for the certified reference tea sample (GBW07605) was in a good agreement with the certified value. The proposed method has also been successfully applied to the determination of trace Cu(2+) in dried sweet potato, lake water and milk powder, the recovery of Cu(2+) for spiked samples was between 91% and 109.6%.
Journal of hazardous materials 03/2010; 179(1-3):521-5. · 4.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: A simple, sensitive method for the speciation of inorganic antimony by cloud point extraction combined with electrothermal atomic absorption spectrometry (ETAAS) is presented and evaluated. The method based on the fact that formation of a hydrophobic complex of antimony(III) with ammonium pyrrolidine dithiocarbamate (APDC) at pH 5.0 and subsequently the hydrophobic complex enter into surfactant-rich phase, whereas antimony(V) remained in aqueous solutions. Antimony(III) in surfactant-rich phase was analyzed by ETAAS after dilution by 0.2 mL nitric acid in methanol (0.1M), and antimony(V) was calculated by subtracting antimony(III) from the total antimony after reducing antimony(V) to antimony(III) by l-cysteine. The main factors affecting the cloud point extraction, such as pH, concentration of APDC and Triton X-114, equilibrium temperature and incubation time, sample volume were investigated in detail. Under the optimum conditions, the detection limit (3 sigma) of the proposed method was 0.02 ng mL(-1) for antimony(III), and the relative standard deviation was 7.8% (c=1.0 ng mL(-1), n=7). The proposed method was successfully applied to speciation of inorganic antimony in the leaching solutions of different food packaging materials with satisfactory results.
Journal of hazardous materials 10/2009; 175(1-3):146-50. · 4.14 Impact Factor