铬酸钠碳化母液制备氢氧化铬工艺优化 及三氧化二铬粒度分布的影响

研究了利用铬酸钠碳化母液制备氢氧化铬工艺优化及三氧化二铬粒度分布的影响，主要考察了恒温温度、氢氧化铬洗涤方式对产品质量的影响；还考察了在固定煅烧条件下，铬酸钠含量对三氧化二铬颗粒形貌的影响以及铬酸钠碳化母液碳化率与三氧化二铬粒度分布的关系。结果表明，随着铬酸钠碳化母液碳化率的提升，Cr（Ⅵ）达到最大还原率时所需恒温温度下降，经过3次洗涤的氢氧化铬滤饼煅烧后铬酸钠质量分数为13%~15%，制备的三氧化二铬呈类球体，颗粒粒径均匀，洗涤烘干后各项参数指标均优于GB/T 20785—2006《氧化铬绿颜料》。通过增加原料碳化率，三氧化二铬颗粒的中位径D50随之增大，在碳化率为39.87%时制得的三氧化二铬中位径D50为 3.13 μm，粒度分布为典型的正态分布，其特征粒径值均符合高端氧化铬绿产品的技术要求。

Process optimization of preparation of chromium hydroxide from sodium chromate carbonization mother liquor and effect of particle size distribution of chromium trioxide

The process optimization of prepartion of chromium hydroxide by using sodium chromate carbonization mother liquor and the effect of particle size distribution of chromium oxide were studied.The influence of constant temperature and washing method of Cr（OH）3 on product quality was investigated.Effects of sodium chromate content on the morphology of Cr2O3 particles and the relationship between the carbonation rate of sodium chromate carbonization mother liquor and the particle size distribution of Cr2O3 under fixed calcination conditions was studied.Results showed that with the increase of carbonation rate of sodium chromate carbonization mother liquor，the constant temperature requiring for the maximum reduc tion rate of Cr（Ⅵ） decreased.The chromium hydroxide filter cake was washed for three times and then calcined.The mass fraction of sodium chromate after calcination was 13%~15%.The prepared Cr2O3 was similar to sphere and its particle size was uniform.The parameters of the product after washing and drying were in line with Chromium Oxide Green Pigment， GB/T 20785—2006.By increasing the carbonation rate of the raw material，the D50 of Cr2O3 particles increased，and the Cr2O3 was obtained with a D50 of 3.13 μm at a carbonization rate of 39.87%.The particle size distribution was a typical normal di stribution，and the characteristic particle size values met the technical requirements of high end chromium oxide green products.