淀粉水热还原铬酸钾制备氧化铬应用基础研究

Chromium oxide is widely applied in metallurgy, ceramics and refractory materials for its good properties of hardness, thermal stability and corrosion resistance. The resource utilization rate was low in the traditional process for production of chromium oxide. And high toxicity chromium slag, contaminative sodium bisulfate and liquid waste were generated from the process, resulting in serious environmental pollution. In the project, hydrothermal reduction of potassium chromate by starch is used to process the leach liquor form chrome by sub-melton salt method. The key scientific problem is to understand the reaction process and adjustment mechanism in the key process of the chromium oxide preparation by hydrothermal reduction. Then by strengthening and controlling the related regulation of aggregation and mass transfer in the sintering process of chromium hydroxide, the reduction process can realize the collaborative adjustment mechanism between reaction and chromium oxide particle size. Using mineral processing, chemical and materials multidisciplinary research methods, we study the starch degradation mechanism, phase transfer law of hydrothermal reduction product and aggregation mechanism of chromium hydroxide in order to explain the reaction process between potassium chromate and starch and reveal the component control of hydrothermal reduction product and particle size adjustment law of chromium oxide during hydrothermal process in the potassium hydroxide/potassium carbonate system. The project can expand the scope of hydrothermal reduction applied in the leaching liquor from chrome and provide a theoretical basis for the low-cost, short process and high efficiency technology.

氧化铬硬度高、热稳定性高、耐腐蚀性好，广泛应用于冶金、陶瓷、耐火材料等领域。传统的氧化铬工业生产方法资源利用率低，产生高毒性铬渣、含铬硫酸氢钠和废液等，造成严重的环境污染。本项目以亚熔盐法得到的铬铁矿浸出液为研究对象，围绕淀粉水热法制备氧化铬的反应过程和水热产物调控等关键科学问题，通过强化和调控关键组分氢氧化铬的团聚和烧结传质的相关规律，实现水热反应过程与氧化铬颗粒形成的协同调控机制。采用冶金、化工与材料多学科交叉分析方法，开展水热反应过程中淀粉降解机制、水热产物物相转变规律和氢氧化铬团聚机制的研究，旨在明确氢氧化钾/碳酸钾体系，淀粉水热还原铬酸钾的反应历程，揭示水热条件下水热产物组分控制和氧化铬产物颗粒调控规律。本项目的实施，将扩展水热法在实际铬铁矿浸出液体系中的应用，同时为亚熔盐法低成本、高效和清洁生产氧化铬奠定理论基础。

传统的氧化铬工业生产方法资源利用率低，产生高毒性铬渣、含铬硫酸氢钠和废液等，造成严重的环境污染。本项目以亚熔盐法得到的铬铁矿浸出液为研究对象，围绕淀粉水热法制备氧化铬的反应过程和水热产物调控等关键科学问题，通过强化和调控关键组分氢氧化铬的团聚和烧结传质的相关规律，实现水热反应过程与氧化铬颗粒形成的协同调控机制。低温下，氢氧化钾和碳酸钾可促进淀粉的水解过程。水热条件下，氢氧化钾、碳酸钾和铬酸钾均会加速水解和葡糖糖的裂解反应。根据红外、UV-Vis和MS对还原母液的分析，证明了淀粉在铬酸钾与碳酸钾作用下的主要产物为碳酸盐和3,5–二羰基–6–羟基己醛。热力学分析表明，CO2的参与增加了铬酸钾水热还原反应的趋势。实验研究进一步表明较高的二氧化碳压力会导致大量中间产物碱式碳酸铬钾的生成。采用预碳化的方式可以显著减少含铬碱式碳酸盐的生成，从而减少煅烧氧化铬的可溶性铬含量，提高总回收率。重复试验铬酸钾体系的还原转化率稳定(97-98wt%)，氢氧化铬煅烧过程中铬酸钾的损失率约3-5wt%，铬酸钾总的回收率较高（93-95wt%）。200L碳分-液相还原扩试验证了实验室的工作，还原转化率接近100wt%。氧化铬的纯度大于99wt%，达到行业要求。