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.

我们的研究团队提出了一项创新技术，即氧化铁皮红土矿石的硝酸压力浸出。HNO _3的再生对于改进所提出的技术及其商业应用具有重要意义，但是尚未对其进行系统的研究。本文研究了用低成本H ₂ SO ₄从Ca（NO ₃）₂溶液再生HNO ₃，同时合成纤维状CaSO ₄ ·2H ₂ O副产物的方法。作为理论基础，CaSO ₄ ·2H ₂ O在HNO _3中的溶解度媒体进行了研究。结论：CaSO ₄ ·2H ₂ O的溶解度随温度升高或HNO ₃浓度升高而增加，对后续的实验研究和分析具有重要的指导意义。然后，利用ICP-AES和SEM研究了各种因素对滤液中残余Ca ²⁺浓度，再生HNO ₃浓度和合成产物形态的影响。并分析了其作用机理。结果表明，在最佳条件下，再生的HNO ₃浓度达到116 g / L，残留的Ca ²⁺浓度为9.7 g / L。此外，纤维状CaSO可以同时合成长径比高（长406.32 µm；直径14.71 µm；长径比27.62）的₄ ·2H ₂ O副产物。