Papers by Author: Dong Zhang

Abstract: A sensitive method has been developed for the speciation of Cr(III) and Cr(VI) in natural water using a porous nano-barium-strontium titanate by sorghum straw template method (SPBST) and flame atomic absorption spectrometry (FAAS). The procedure presented based on Cr(III) and Cr(VI) show different adsorption capacities on the SPBST at different pH values, that is, Cr (III) selectively retained at pH 13, but Cr(Ⅵ) can’t be adsorbed. Whereas Cr (VI) retained at pH 1, but Cr(Ⅲ) can’t be adsorbed. Hence, Cr(Ⅵ) and Cr(Ⅲ) can be separated through changing pH value of medium. Cr(Ⅵ) and Cr(Ⅲ) adsorbed on the SPBST can be completely eluted using 1•0 mol•L⁻¹ NaOH and 1.0 mol•L⁻¹ HCl, respectively. And Cr(Ⅵ) and Cr(Ⅲ) were determined by FAAS, The preconcentration factor of the method was 100. At the optimum conditions determined experimentally, the adsorption capacities were calculated to be 21.6 mg•g⁻¹ and 7.3 mg•g⁻¹, respectively. The proposed method was applied to the determination and speciation of chromium in tap water, lake water and wastewater samples with satisfactory results.

Abstract: The micro-column packed with porous nano-barium- strontium titanate microspheres, joining with injector, a new manual-controlled injection porous nano-barium- strontium titanate microspheres enricher (PBSTME) was prepared. The enrichment capability of the PBSTME for the heavy metal ions, such as zinc, nickel, copper, manganese, cobalt and silver was investigated. The results showed that all the heavy metals studied could be quantitatively retained by the PBSTME in the pH range of 5–8, and then eluted completely with 2 mol•L^-1 HNO₃. The detection limits of this method for zinc, nickel, copper, manganese, cobalt and silver ions were 0.028 μg•L^-1, 0.2μg•L^-1, 0.031 μg•L^-1, 0.022 μg•L^-1, 0.057μg•L^-1 and 0.039 μg•L^-1 with an enrichment factor of 50, respectively. A new method has been developed for the determination of trace heavy metal ions based on pre-concentration with a PBSTME prior to their determination by flame atomic absorption spectrometry. The method has been applied to the simultaneous determination of trace amounts of zinc, nickel, copper, manganese, cobalt and silver ions in water sample with satisfactory results.

Abstract: A manual-controlled injection barium-strontium titanate based on glass fiber filter enricher(MIBSTE) was prepared, and its application in speciation of Cr(III) and Cr(VI) from water was studied. The optimum experimental parameters for preconcentration and separation of the Cr(III) and Cr(VI) have been investigated. The results showed that the BBST had adsorption capacity towards the Cr(III) and Cr(VI) at the different conditions. And two forms of chromium show different adsorption capacities at different pH values, Cr (III) could be adsorbed at pH ≥ 10, but Cr(VI) can’t be adsorbed. Whereas Cr (VI) retained at pH ≤ 2, but Cr(III) can’t be adsorbed. Therefore, it is possible that the two forms of chromium are complete separated. The Cr(III) and Cr(VI) could be completely eluted with 1 mol•L⁻¹ HCl and 1 mol•L⁻¹ NaOH, respectively. The chromium concentration was measured by atomic absorption spectroscopy. A new method for determination of the speciation of chromium in environmental water samples based on the manual-controlled injection enricher and atomic absorption spectroscopy determination was proposed. The method was successfully applied for the determination of Cr(III) and Cr(VI) in environmental waters with satisfactory results.

Abstract: A new method for the preconcentration and separation of cobalt ion in water was described. The methodology combines determination using a flame atomic absorption spectrometry (FAAS) with adsorption and desorption of cobalt on the nano-barium-strontium titanate powder coated by dithizone (BST-dithizone). The operation conditions for the pre-concentration and separation of the cobalt, including pH, contact time, eluent condition and co-existing ions have been investigated. The result showed that the cobalt ion could be adsorbed by BST-dithizone. The adsorption quantity was affected by the pH value of medium and shaking time. In the medium of pH 6.0, the adsorption capacity of BST-dithizone to cobalt ion was 8.92 mg·g^-1 when the shaking time was more than10 min. The cobalt adsorbed on the adsorbent could be completely eluated and recovered using 10 g·L⁻¹ ethylene diamine tetraacetic acid (EDTA) solution. The enrichment factor was 100. The detection limit of cobalt was 0.53 ng·L⁻¹. The purposed method has been applied to the pre-concentration and separation of cobalt in the water sample with satisfied results.

Abstract: Zinc ion was adsorbed and enriched by nano-barium-strontium titanate immobilized on aluminum oxide(ABST). The adsorption and elution conditions were investigated. The results showed that ABST had strong adsorption ability for zinc ion in water in the medium at pH more than 4.0. The maximum adsorption capability was up to 16.38 mg/g. The adsorbed zinc on ABST could be eluted and reclaimed with 0.5 mol/L of HNO₃. Zinc was determined by flame atomic absorption spectrophotometry (FAAS). The detection limit of this method for zinc ion was 2.5 μg/L. The method had been applied to the determination of trace zinc in surface water and tap water samples with recovery of 92.5%-98.7%. The results were found to be in agreement with the method of dithizone spectrophotometry.

Abstract: A new system for determination of trace mercury based on separation and preconcentration with porous nano-barium-strontium titanate microspheres (PBSTM) prior to its determination by a hydride generation-atomic absorption spectrometry (HG-AAS) was propounded. The optimum experimental parameters for preconcentration of mercury, such as pH of the sample, contact time, sample volume, eluent and interfering ions, have been studied. The result showed that mercury could be quantitatively retained by PBSTM in the pH range of 4-8, the shaking time was 10 min, and the amount adsorbed was 12.2 mg·g^-1. The mercury adsorbed on the sorbent could be eluated completely with 2 mol·L^-1 HNO₃. The detection limit of this method for mercury was 6.3 ng·L^-1 with an enrichment factor of 60. The method has been applied for the determination of trace amounts of mercury in whole blood and urine with satisfactory results.

Abstract: A new method was proposed for the preconcentration/separation of zinc at trace levels using a modified organo-bentonite with dithizone (D-O-bentonite) and determined by flame atomic absorption spectrometry (FAAS). The influences of some experimental parameters including pH of the sample solution, contact time, and volume of eluent have been investigated. The influences of some matrix elements were also examined. The results show that the zinc ion could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 4-5, the contact time was 20 min, and capacity of adsorption was 32.0 mg·g^-1. The zinc adsorbed on the sorbent could be completely eluated by using 0.5 mol·L^-1 HNO₃. The method has a good tolerance to matrix interference. The detection limit of the method for zinc ion was 0.013 µg·L^-1. The method was successfully applied to the pre-concentration/separation of zinc ion in the tap water and human urine with satisfactory results.

Abstract: A new method for the determination of traces of mercury in environmental and biological samples is described. The present methodology combines determined using a hydride generation-atomic absorption spectrometry (HG-AAS) with pre-concentration/separation of the analyte on dithizone-anchored organobentonite (D-O-bentonite). Optimal experimental conditions for the adsorption of the Hg, including pH, contact time, eluent concentration and volume and co-existing ions have been studied. The result showed that the mercury could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 5.0, the adsorption time was 15 min, and capacity of adsorption was 23.2 mg·g^-1. The mercury adsorbed on the sorbent could be completely eluated by using 3 mol·L^-1 HCl. The adsorption agent has been applied to the pre-concentration/separation of mercury in surface water and human hair samples with satisfied results.

Abstract: In this paper, a new method for the determination of bismuth in urine and tap water is described. The methodology combines determined using a hydride generation-atomic absorption spectrometry (HG-AAS) with pre-concentration of the bismuth on the modified organobentonite by dithizone (D-O-bentonite). Optimal experimental conditions for the adsorption and elution of the bismuth, including pH, contact time, eluent concentration, eluent volume and co-existing ions have been investigated. The result showed that the bismuth ion could be adsorbed on the D-O-bentonite. The adsorbed quantitive was affected by the pH value and contact time. In the medium of pH 5.0, the shaking time was 10 min, the adsorption capacity was 15.2 mg·g^-1. The bismuth adsorbed on the modified organobentonite by dithizone could be completely eluated by using 2 mol·L^-1 HNO₃. The method has been applied to the pre-concentration/separation of bismuth in the human urine and tap water samples with satisfied results.

Abstract: Nano-strontium titanate based on glass fiber filter (GFST) was successfully prepared by sol-gel method and characterized using XRD and SEM. The adsorptive potential of GFST for heavy metal ions, such as lead, cadmium, zinc and nickel, was investigated. The results showed that the nano-strontium titanate could crystal based on glass fiber, gaining a new block adsorbent like a leaf. The lead, cadmium, zinc and nickel ions were quantitatively retained at pH 6-9; their adsorption capacities of GFST for lead, cadmium, zinc and nickel ions were 153.21 mg•g-1, 8.32 mg•g-1, 21.36 mg•g-1 and 4.80 mg•g-1, respectively. The adsorbent can be regenerated completely by elution with 0.5 mol•L-1 HNO3. The adsorbent has a promising prospect in removal or enriching of lead, cadmium, zinc and nickel ions in water.