Recovery of titanium from undissolved residue(tionite) in titanium oxide industry via NaOH hydrothermal conversion and H_2SO_4 leaching

To recover titanium from tionite, a new process consisting of NaOH hydrothermal conversion, water washing, and H2SO4 leaching for TiO2 preparation was developed. The experimental results show that under the optimum hydrothermal conversion conditions, i.e., 50% NaOH （mass fraction） solution, NaOH/tionite mass ratio of 4：1, reaction temperature of 240 ℃reaction time of 1 h and oxygen partial pressure of 0.25 MPa, the titanium was mainly converted into Na2TiO3, and the conversion was 97.2%. The unwanted product Na2TiSiO5 remained stable in water washing, and its formation was prevented by improving NaOH concentration. In water washing process, about 97.6% of Na＋ could be recycled by washing the hydrothermal product. The NaOH solutions could be reused after concentration. 96.7% of titanium in the washed product was easily leached in H2SO4 solution at low temperatures, forming titanyl sulfate solution to further prepare TiO2.

Leaching kinetics of gold bearing pyrite in H_2SO_4-Fe_2(SO_4)_3 system

Gold bearing pyrite leaching was conducted in H2SO4-Fe2（SO4）3 system at different reaction temperatures,with different ferric ion concentrations,sulfuric acid concentrations and stirring speeds.The leaching kinetics and mechanism were studied.When the temperature ranged between 30-75 °C,the pyrite leaching was mainly controlled by chemical reaction with positive correlation to the ferric ion concentration.The activation energy obtained from Arrhenius empirical formula is 51.39 k J/mol.The EDS and XPS analyses suggest that the oxidation of sulfur within pyrite is through a series of intermediate stages,and eventually is oxidized to sulphate accompanied with the formation of element sulfur.This indicates a thiosulfate oxidation pathway of the gold bearing pyrite oxidation in H2SO4-Fe2（SO4）3 system.

从含锂废渣中回收制备碳酸锂的工艺研究

针对含Li废渣中Li资源得不到充分利用的问题,采用H_2SO_4浸出、NaOH除杂及EDTA深度除杂、Na_2CO_3沉锂工艺从含Li废渣中回收制备Li_2CO_3。实验结果表明,优化的工艺参数为:H_2SO_4酸浸过程,H_2SO_4浓度5%(体积分数)、浸出温度70℃、浸出时间60min;NaOH除杂及EDTA深度除杂过程,加入NaOH至酸浸液pH值为12,之后加入2.0g/L的固体EDTA进行深度除杂;Na_2CO_3沉锂过程,溶液中Li+浓度23g/L,Na_2CO_3浓度为300g/L、用量为理论量的1.10倍,水浴温度95℃,反应时间40min。在优化工艺参数条件下,制备出的Li_2CO_3各项指标基本达到Li_2CO_3-0级要求,且Li综合回收率达到95%以上。