Papers by Keyword: Preconcentration

Abstract: In a batch system, The Cu(II) preconcentration parameters were optimized using chitosan-crosslinked dialdehyde carboxymethyl cellulose (CS-DCMC). The experiment was started with the oxidation of carboxymethyl cellulose by periodate to form DCMC. The CS-DCMC adsorbent was then prepared with a mass ratio of CS-DCMC=1:1. The adsorbent is characterized by FTIR for functional group analysis and SEM-EDX for morphological analysis and the percentage of elements in CS-DCMC adsorbent. In the optimization of preconcentration parameters, the optimal adsorption, desorption, and enrichment factors were obtained at pH 4, adsorbent mass of 90 mg, adsorption time of 95 min, Cu(II) concentrations of 7 mg/L, and Na₂EDTA 1 M. The application of CS-DCMC on wastewater containing Cu(II) under optimal conditions gave good results. Wastewater containing Cu(II) 0.1 mg/L can be concentrated to 0.53 mg/L with an enrichment factor of 5.26 times, 0.2 mg/L Cu(II) can be concentrated to 1.08 mg/L with an enrichment factor of 5.40 times, and 0.3 mg/L Cu(II) can be concentrated to 1.68 mg/L with an enrichment factor of 5.59 times. The enrichment factor obtained is almost close to the theoretical enrichment factor of 6 times.

Abstract: A new sorbent (PAMAM4.0GASG) with gallic acid as functional group has been prepared based on G4.0 polyamidoamine dendrimer modified silica gel (PAMAM4.0SG) and characterized with FTIR. It was employed for selective separation, preconcentration and determination of lead in different samples by flame atomic absorption spectrometry (FAAS). Experimental conditions for effective separation and preconcentration of lead were optimized. The preconcentration factor reaches 200 for lead. The relative standard deviation (R.S.D.) under optimum conditions was 2.1% for 5.0 μg ml¹ of Pb (II).The relative standard deviation (R.S.D.) was 2.1% for 5.0 μg ml¹ of Pb (II). The limit of detection (LOD) of 0.081μg ml¹ was achieved with a sample loading flow rate of 4.2 ml min¹ and a 10 ml sample volume in the proposed method. The proposed column enrichment method was applied for the preconcentration/separation and determination of Pb (II) in tap water and river water samples successfully.

Abstract: A new method for the separation and preconcentration of Chrome and Manganese using potassium titrationate whisker was developed prior to the determination by FAAS. The influences of analytical parameters including amount of sorbent, the adsorption capacity, the coexistence ion influence and the adsorption behavior were also studied by the flame atomic absorption spectrometry, the effects of concomitant ions were also examined. The detection limits (3s) were 15ng•mL^-1 and 44 ng•mL^-1. The method was applied to the determination of analytes in real samples, such as tea and environmental samples, etc. and good results were obtained(relative standard deviations93%).

Abstract: The results show that under the condition of grinding fineness(-200 mesh content) of 52.88% and magnetic field intensity of 0.2T, the index of concentrate yield is 13.25%, concentrate grade is 58.75% and concentrate recovery is 57.32% with preconcentration technology by magnetic separation.

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: 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: Exhaustion of high-grade magnetite resources and large demand for iron ore in the rapidly developing steel industry promotes the mining enterprises to exploit low-grade magnetite. Low-grade magnetite with a low content of valuable minerals is hard to be separated with the conventional separation process flow because of its high beneficiation costs. By preconcentration technology, enriching valuable minerals and discarding large amounts of gangue as soon as possible before grinding, low beneficiation costs can be achieved in low-grade magnetite’s beneficiation. After continuous researches and production practices and the development of relevant efficient crushing and separating equipments, preconcentration technology has made great progress: from crushing-dry magnetic separation technology to grinding-wet magnetic separation technology, then to ultrafine crushing-wet magnetic separation technology. Now preconcentration has become an indispensable stage in low-grade magnetite’s beneficiation.

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.