Papers by Author: Dong Zhang

Abstract: A preconcentration method based on the adsorption of palladium-dimethylglyoxime -anchored organobentonite (DMG-bentonite) for the determination of palladium at trace levels by flame atomic absorption spectrometry (AAS) has been developed. The optimum experimental parameters for the adsorption and preconcentration of the palladium, such as pH value of medium, contact time, eluent and coexisting ion, have been investigated. The results showed that the palladium ion could be quantitatively retained by the DMG-bentonite in the pH range of 3–5 using citric acid/citrate buffer, the adsorption time was 20 min, and capability of adsorption was 8.73 mg•g-1. The palladium ion adsorbed on the DMG-bentonite could be completely eluated by using 1 mol•L-1 HCl. The detection limits of this method for palladium was 1.02µg•L-1 with an enrichment factor of 60. The method has been applied to the determination of trace amounts of palladium ion in street dust and environmental water with satisfactory results.

Abstract: The adsorption capability of porous nano-barium-strontium titanate by sorghum straw template method (SBST) for nickel in water was studied. The optimum experimental parameters for the adsorption and preconcentration of the nickel, such as pH, time, eluent and coexisting ion, have been investigated. The results showed that the nickel in water could be adsorbed on the SBST. The adsorbed quantitively was affected by the pH value of medium and time. In the medium of pH 5-8, the adsorption time was 20 min, and capacity of adsorption was 13.27 mg•g-1. The adsorbed nickel could be completely eluated using 2 mol•L-1 HNO3. The pre-concentration factor for nickel was more than 100. The method has been applied to the preconcentration and flame atomic absorption spectrometry determination of nickel in water samples. The recoveries were 92.0%-104.0%.

Abstract: The adsorption capability of nano-barium-strontium titanate coated by dithizone(BST- dithizone) for mercury in environmental water samples was studied. The optimum experimental parameters for the adsorption and desorption of the mercury, such as pH values, contact time and eluent, have been investigated. The results showed that the mercury ion in water could be adsorbed on the BST- dithizone. The adsorption capability was affected by the pH value of medium and contact time. In the medium of pH 3-8, the adsorption time was more than 15 min, and capacity of adsorption was 15.3 mg·g-1. The used adsorbent could be completely regenerated using 2 mol·L-1 HNO3. A new method for the removal of mercury in water samples was proposed. The method has been applied to the removal of mercury in waste water samples with satisfied results.

Abstract: A new modified organo-bentonite using dithizone(D-O-bentonite) was used for preconcentration, separation and determination of silver(I) in natural water by flame atomic absorption spectrometry (FAAS). The experimental conditions for effective adsorption and elution of trace levels of silver (I) were optimized with respect to different experimental parameters. The influences of some common coexisting ions were also examined. The results show that the silver 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 4-8, the contact time was 15 min, and capacity of the sorbent was 19.7 mg·g^-1. The silver(I) adsorbed on the sorbent could be completely eluated by using 1 mol·L^-1 HNO₃. The preconcentration factor is 100. The detection limit of the method for silver was 0.02 µg·L^-1. The method was applied to the pre-concentration/separation of silver in the environmental water with satisfactory results.

Abstract: A new method for the adsorption and preconcentration of bismuth in urine was described. The methodology combines determined using a hydride generation-atomic absorption spectrometry (HG-AAS) with pre-concentration and separation of the bismuth on the nano-barium-strontium titanate powder coated by dithizone (BST-dithizone). The experimental conditions for the pre-concentration and separation of the bismuth, including pH value of the medium, shaking time, eluent condition and co-existing ions have been investigated. The result showed that the bismuth in urine could be adsorbed on the BST-dithizone. The adsorption percentage 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 bismuth (III) was 13.4 mg·g^-1 when the shaking time was 10 min. The bismuth adsorbed on the BST-dithizone could be completely eluated by 2 mol·L^-1 HNO₃. The enrichment factor was 100. The detection limit of bismuth (III) was 5.1 ng·L⁻¹.The method has been applied to the pre-concentration and separation of bismuth in the human urine and tap water with satisfied results.

Abstract: A new method based on the sorption of the nano-barium strontium titanate immobilized on the silica gel G(GBST) to heavy metal ions, included Mn(Ⅱ), Cu²⁺, Ni²⁺,Co²⁺ and Ag⁺, in waste water. The effects of process parameters such as pH, contact time, regeneration conditions and the effects of common coexisting ions on the ions uptake were investigated. The results showed that the manganese, copper, nickel, cobalt and silver ions studied could be quantitatively retained at a pH value range of 7~9. The adsorption capacities of GBST for manganese, copper, nickel, cobalt and silver ions were found to be 8.2 mg/g, 18.3 mg/g, 4.2 mg/g, 2.2 mg/g and 3.1 mg/g, respectively. The heavy metal ions adsorbed on the sorbent could be eluated completely with diluted HNO₃ solutions. The GBST can be used as an effective adsorbent for the treatment of wastewaters contaminated with manganese, copper, nickel, cobalt and silver ions.

Abstract: A new adsorption agent, nanosized strontium titanate immobilized on the silica gel G (GSTO) was prepared, and it was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The ability of the new adsorption to remove heavy metal Pb, Cd, Zn, Cu, Ni and Mn from water samples was assessed. The research results displayed that adsorbent has the highest adsorption capacity for Pb, Cd, Zn, Cu, Ni and Mn in ions mixture system. Optimal experimental conditions including pH and contact time have been established. Desorption studies were carried out successfully with diluted HNO3 solutions. Thus, nano-strontium titanate immobilized on the silica gel G is favorable and useful for the removal of these heavy metal ions, and the high adsorption capacity makes it a good promising candidate material for Pb, Cd, Zn, Cu, Ni and Mn removal.

Abstract: Porous nano-strontium titanate (PST) was successfully prepared by the reversed-phase suspension polymerization and sol-gel method using reversed-phase suspension droplets as the template, and characterized by XRD and SEM. The ability of the new adsorption to remove lead, cadmium, zinc, copper and nickel ions from water samples was assessed. The results showed that the sorbents were porous, perovskite strontium titanate, and the average particle diameter of crystalloid was 30 nm. The lead, cadmium, zinc, copper and nickel ions were quantitatively retained at pH 5-8; their adsorption capacities of PST for lead, cadmium, zinc, copper and nickel ions were 145.9 mg•g^-1, 4.3 mg•g^-1, 25.2 mg•g^-1, 19.6 mg•g^-1and 3.7 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, copper and nickel in water.