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HNO3再生对于褐铁型红土镍矿硝酸加压浸出技术的完善和工业应用意义重大.本文采用低成本的H2SO4从Ca(NO3)2溶液中再生HNO3,并同步制备CaSO4·2H2O副产物.作为理论基础,测定了CaSO4·2H2O在HNO3介质中的溶解度.结果表明,CaSO4·2H2O的溶解度随着温度的升高或HNO3浓度的增大而不断增大,这对后续的实验研究和结果分析具有指导意义.借助电感耦合等离子体原子发射光谱分析和扫描电子显微镜等检测手段考察了各因素对滤液残留Ca2+浓度、再生HNO3浓度和产物形貌的影响,并分析了其影响机理.结果表明,在最优条件下,再生HNO3浓度达116 g/L,滤液残留Ca2+浓度为9.7 g/L,同步制备的CaSO4·2H2O副产物具备高纵横比(长406.32μm;直径14.71μm;纵横比27.62).“,”An innovative technology, nitric acid pressure leaching of limonitic laterite ores, was proposed by our research team. The HNO3 regeneration is considerable significance for the improvement of the proposed technology and its commercial application, but it has not been systematically investigated. Herein, regenerating HNO3 from Ca(NO3)2 solution with low-cost H2SO4, and simultaneous synthesis of fibrous CaSO4·2H2O by-products were studied. As a theoretical basis, the solubility of CaSO4·2H2O in HNO3 medium is studied. It is concluded that the solubility of CaSO4·2H2O increases with increasing temperature or increasing HNO3 concentration, which has considerable guiding significance for the subsequent experimental research and analysis. Then, the effects of various factors on the residual Ca2+ concentration of filtrate, the regenerated HNO3 concentration and the morphology of synthesized products are investigated using ICP-AES and SEM. And the effect mechanism is also analyzed. The results indicate the regenerated HNO3 concentration reaches 116 g/L with the residual Ca2+ concentration being 9.7 g/L at the optimum conditions. Moreover, fibrous CaSO4·2H2O by-products with high aspect ratios (length, 406.32 μm; diameter, 14.71 μm; aspect ratio, 27.62) can be simultaneously synthesized.