| Thallium is a kind of heavy metal elements, which is located in the periodic table ?A clan, 6 cycles. Thallium has two chemical valence state, there was a price and are three price. Thallium ion(?) with its compounds were relatively stable, higher solubility; Thallium ion(?) with its compounds were not stable, volatile halogen water loss, the two valence state under certain conditions can change each other. In nature, thallium occurrence in sulfide ore, but with the industrial demand, mining and ore smelting, thallium release, threats to human health, so the thallium pollution control is a difficult problem to be solved.Taking a lead and zinc smelter wastewater as test samples, through the oxidation-precipitation and ion exchange resin method to analysis the thallium(?) and the distribution of thallium(?) ion content, and in addition to the thallium method on this experimental research. In addition, also analyzed the interference in the process of practical analysis of heavy metals in waste water source, put forward the reasonable solution.The main research results are as follows:1.Using hydrogen peroxide to oxidized Tl(?) into Tl(?) before ferric sulfate co-precipitation and enrichment under the condition of alkaline, that was the total amount of thallium. Tl(?) was obtained by the precipitation and enrichment of original wastewater under the condition of alkaline, and the Tl(?) was acquired by the total amount of Tl minus that of Tl(?).The results showed that synergistic effects of hydrogen peroxide and ferric sulfate performed better than single reagent did. The dosages of hydrogen peroxide and ferric sulfate were optimized. The matrix effect and pH were also studied. The relative standard deviation method(n=4) was between 3.1% and 5.5%. Analysis of the Lead-Zinc smelting wastewater, Tl(?) accounted for 26.8%~31.7%, and Tl(I) for 68.3%~73.2%, respectively, which showed that the content of Tl(?) and Tl(?) appeared a relatively stable distribution.2.Using hydrogen peroxide as oxidant and ferric sulfate as precipitant agent to remove the thallium in the smelting wastewater. The results of the total precipitation experiment of thallium showed that the ratio of hydrogen peroxide and water volume were 1:10, the dosage of precipitant agent ferric sulfate was 0.1g, the reaction time was 30 minutes, aging time was 1 hour, the pH value was 10, so the removal of thallium rate can reached 99%.3.According to the characteristic of high metal ions have strong coordination ability and strongly basic anion exchange resin is selective for complex anion, a method for analyzing the speciation of thallium on 717 resin for separation and enrichment by atomic absorption spectrophotometer was investigated. Tl(III) was complexed with DTPA(penta-carboxymethyl-diethylenetriamine) to form a Tl(DTPA)2- anionic complex which can be quantitatively adsorbed on 717 anion exchange resin, then the retained were eluted with a reducing agent Na2SO3 to break the complexation. The dosages of organic chelator(DTPA) and reductant(Na2SO3) were optimized. adsorption acidity, adsorption time and the effect of common coexisting ions were studied. Using this method to analysis the speciation of thallium in smelting wastewater, the recovery of the total amount of Tl ranged from 95.3% to 98.1%, with the RSD(n=4) was 1.6%~3.4%; the proportion of Tl(III) was 28.4%~32.5%% and Tl(I) was 67.5%~71.6%, respectively. This reveals that both Tl(III) and Tl(I) were present with a certain proportion in the smelting wastewater.4.Tl(III) were quantified by FAAS using the complexation of Tl(DTPA)2- and separation by ion-exchange resin 717 and D301 to realize the speciation analysis of Tl(I)/Tl(III). The adsorption isotherm equation and the thermodynamic parameters were studied, and the effect of pH, contact time, temperature, initial concentration and ionic strength was discussed. Before and after the adsorption, the ion-exchange resin was characterized with Fourier Transform Infrared Spectrometry and Energy Dispersive Spectrometer. The kinetic data were fitted by pseudo-first-order equation, pseudo-second-order equation model, respectively; the thermodynamics data were matched with Langmuir equation Freundlich equation model, respectively. The results showed that the pseudo-first-order equation and Langmuir equation could provide the best correlation coefficient to the results. The thermodynamic parameters showed that adsorption was a spontaneous and endothermic process. Both resin 717 and D301 had better adsorption ability, but adsorption rate of 717 is faster, which can be finished within 40 min. The chemical speciation of thallium aqueous solution on resin 717 and D301 showed that the total thallium recovery is 96.9~107.0% and 95.9~104.2%, respectively. It is meaningful to the development of the speciation analysis of Tl in the future.5.Analysis the interference of high salinity on determination of Tl Pb Cd by flame atomic absorption spectrometry in solution. The pure solution NaCl KCl MgSO4 and MnSO4 within the concentration gradient 0~60 mg/m L for the absorbance absorption of detecting Tl Pb Cd were analyzed, and the concentration in high salinity wastewater were also measured. The results indicated that 25 mg/m L of NaCl, 30 mg/m L of KCl?MgSO4 and MnSO4 had no influence on the determination of Tl;20 mg/m L of NaCl and KCl, 10 mg/mL of MgSO4, 50 mg/mL of MnSO4 had no influence on the determination of Pb;15 mg/m L of NaCl and MnSO4, 40 mg/mL of KCl 60 mg/m L of MgSO4 had no influence on the determination of Pb, and the salts concentration within 0~30 mg/m L, the elevating amount of atomizer were all 5.5 mL/min.The results of high salinity wastewater of low concentration of heavy metal element determination was not credible;there were mainly physical interference, background absorption interference and acid interference. The mixing matrix solution within 20 mg/mL were found no interference for 1.00 mg/L of Tl,1.00 mg/L of Pb ?0.50 mg/L of Cd. The values of Tl Pb Cd found by standard addition method were in the ranges of 102%~104%,103%~105%,98.0%~104%, respectively with values of RSD's less than 1.82%. |
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