| To meet the demand of China for the antimony thioantimonate, the intensive processing product of antimony, new technique of antimony thioantimonate prepared from sodium pyroantimonate is researched. The processing technique is as follows: sodium sulfantimonate (pentavalent stibium) is prepared by sodium pyroantimonate leached in sodium sulfide solution, antimony trioxide is leached with sodium chloride saturated solution and hydrochloric acid, after the antimony trichloride (tervalence stibium) and sodium sulfantimonate are prepared, they are added to the reaction system of HCl+NaCl to synthesize into antimony thioantimonate. The technique can solve the traditional technique problem of tervalence stibium hydrolysis, products pollution from sulphur and environment pollution from after-reaction liquid. Meanwhile, good economic benefits can be achieved.The experimental process, in which sodium sulfantimonate is prepared by sodium pyroantimonate leached in sodium sulfide solution, is studied. The effect of temperature, concentration of sodium sulfide and leaching time on leaching rate of sodium antimonite is made. When the dosage of sodium sulfide is higher than 1.08 times of the theory dosage, the leaching rate of sodium pyroantimonate begins to decrease from the highest value; with the higher temperature and the longer time, the leaching of sodium pyroantimonate increases;and then the leaching solution is cooled slowly, when the temperature is about 18-20℃,the sodium sulfantimonate can be filted.The experimental results show that the leaching rate can reach 97.42% when the optimum is adopted which the weight ratio of sodium antimonate and antimony is 2.8, and the sodium antimonate is leached at 95℃for 3 hours. After filtration,the crystals of sodium sulfantimonate are produced. The crystals can be used as the raw materials of antimony thioantimonate as well as the products to sell, which can bring good economic benefits.Meanwhile, the influences of pH and concentration of NaCl on hydrolysis of antimony trichloride are studied. The result shows that when the same concentration of antimony ions are kept in different conditions, the concentration of antimony ion in the solution decreases rapidly with the increase of pH value; antimony ion concentration in solution increases with the increase of total antimony ion, the hydrolysates production of antimony trichloride are Sb4O5Cl2,SbOCl,Sb2O3 and Sb(OH)3 by order. When the total chlorine ion concentration is up to 6mol/L, the coordination of antimony ion leads to increase of the antimony ion in the balance solution; when the total antimony ion concentration is added in the same higher dosage, the antimony ion concentration in balance solution decreases with the increase of pH value.The influences of the reaction system of HCl+NaCl, pH value, concentration of sodium chloride, temperature, time and washing on the antimony thioantimonate synthesizing are researched. In order to avoid hydrolysis of tervalence stibium, the reaction of HCl+NaCl+H2O is designed. In the reaction system, NaCl is saturated.Then SbⅤ+ and SbⅢ+, whose mol ratio is 1:1, are dripped into the reaction system and continuously mixed. In the reaction process, HCl and NaOH are used to keep pH value at 2 and the room temperature in the reaction system. The filtrated products are washed with de-ionized water, whose pH value is 2, dried at 75℃for 24 hours. The chemical analyse shows that, the antimony content is 65.1% and the sulpur content is 34.2%.In the half industrial experiment, the direct recovery rate is 98.2%, antimony content is 64.1% and sulphur content is 33.8%, which are close to theoretical content of antimony(65.55%) and sulphur content(34.45%). The brick-red product is analyzed by XRD spectrogram which shows that the product is not compound of Sb2S3,Sb2S5 and S but antimony thioantimonate. |
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