| Aimed at the v-bearing titanomagnetite smelting slag in Panzhihua, the determination of vanadium was investigated, and the leaching characteristics of vanadium, chromium and cadmium were studied using static leaching and dynamic leaching method. Also the effect of the additive(such as humic acid, clay, lime hydrate, montmorillonite, etc.) on the leaching rate of these heavy metals was examined. The research results can provide the basis for the establishment of the scheme which is to stop the migration of vanadium, chromium and cadmium from the slag.A new spectrophotometry method was successfully established for the determination of vanadium(V) in v-bearing titanomagnetite smelting slag at room temperature. A new vanadium colorating system was found for vanadium, phenolreagent(MBTH) and n-naphthyl ethlyenediamine dihydro-chloride(NEDA). The optimal experimental conditions are as following: added 2 m L of 4g·L-1 MBTH, 1 m L of 4g·L-1 NEDA, and 0.3 m L of 0.1 mol·L-1 hydrochloric acid solution to the testing liquid orderly in a colorimetric tube, placed 25 min, then tested the absorbance at 595 nm wavelength at 25 ℃ with reagent blank as reference. The detection limit is 0.045 ug/m L, linear range is 0.08 ~ 16 ug/m L, apparent molar absorptivity epsilon is 1.03×104 L·mol-1·cm-1, the labeled recovery is 97 % ~ 104 %, RSD is 1.37 % for the determination of six times. Most of the anion has no interfere with determination, except Fe3+, which interference can be masked using 2 % EDTA solution.Based on the static leaching experiment, the leaching characteristics of V, Cr and Cd was analyzed with different initial p H of drench filtrate, particle size of slag and liquid-solid ratio. The results show that the leaching rate of vanadium were 1.54 ‰, 1.37 ‰, 1.44 ‰, 1.11 ‰; chromium were 2.66 ‰, 1.54 ‰, 1.32 ‰, 0.93 ‰; cadmium were 91.73 ‰, 79.80 ‰, 86.03 ‰, 79.80 ‰ when the initial p H of extracting agent was 2,3,4 and 5, respectively. The leaching rate were 0.94 ‰, 1.48 ‰, 1.28 ‰ for vanadium; were 1.35 ‰, 1.38 ‰ and 1.38 ‰ for chromium; were 114.44 ‰, 103.03 ‰, 108.37 ‰ for cadmium when particle size of slag was 60 ~100 mesh, 100~200 mesh and >200 mesh, respectively. The leaching rate were 0.42 ‰, 1.43 ‰, 3.89 ‰ of vanadium, were 0.64 ‰, 1.37 ‰ and 1.37 ‰ of chromium, were 86.23 ‰, 101.31 ‰, 231.02 ‰ of cadmium when liquid-solid ratio was 5:1, 10:1 and 20:1, respectively.Based on the dynamic leaching experiment,the leaching rate were 1.32 ‰, 0.28 ‰, 0.39 ‰, 0.096 ‰ of vanadium, were 0.17 ‰, 0.20 ‰, 0.08 ‰, 0.20 ‰ of chromium when the initial p H of leacheate was 2, 3, 4 and 5, respectively. Compared with the static leaching experiment, the leaching rate of vanadium, chromium decreased significantly in dynamic leaching experiment.To stop the migration of vanadium, chromium and cadmium from the slag, the influence of four kinds of additives to the leaching characteristics of vanadium, chromium and cadmium was studied. The results show that montmorillonite, hydrated lime, clay, humic acid can reduce the leaching rate of vanadium by 29.7 %, 49.8 %, 34.3 %,-97.7 %, the leaching rate of chromium by 26.3 %, 14.7 %,-45.8 %,-239.5 %, the leaching rate of cadmium by 5.2 %, 47.8 %, 0.7 %,-213.4 %. Therefore, montmorillonite and hydrated lime can effectively check the leaching of vanadium, chromium, cadmium from slag in batch leaching, and clay checks the migration of vanadium better. However, humic acid can promote the migration of vanadium, chromium, cadmium from the slag.In column leaching process, clay and hydrated lime can make the leaching rate of vanadium reduce by 21.1 %, 12.7 %, the leaching rate of chromium decrease by 44.6 %, 64.3 %, the cadmium was not detection using ICP-MS. |
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