高硫铝土矿溶出液中硫离子赋存形态分析

Analysis on the occurrence of sulfur ions in the digestion solution of high-sulfur bauxite

铝土矿中杂质硫在拜耳法溶出工序大量以不同硫离子形态进入溶液,对氧化铝生产及产品质量带来诸多不利影响。利用GuassView 5.0对不同硫离子形态建模,采用密度泛函理论(DFT)方法中的B3LYP/6-31G(d,p)计算优化目标离子,获得了S^(2-)、S_(2)^(2-)、SO_(3)^(2-)、S_(2)O_(3)^(2-)以及SO_(4)^(2-)等离子的最高占有轨道能(E_(HOMO))和最低空轨道能(E_(LUMO))。计算结果显示,五种含硫离子能量差ΔE_(LUMO-HOMO)大小如下:S^(2-)>SO_(4)^(2-)>S_(2)O_(3)^(2-)>S_(2)^(2-)>SO_(3)^(2-)。即在无外来氧化剂、还原剂存在的条件下,溶液中S^(2-)形式的硫可以稳定存在,其次是SO_(4)^(2-),S_(2)^(2-)、SO_(3)^(2-)和S_(2)O_(3)^(2-)则相对稳定性较弱,这与化学定量分析检测获得的高硫铝土矿溶出液中硫离子的赋存形态及分布情况较吻合,可为高硫铝土矿选择性湿法脱硫提供理论支撑。

The sulfur impurity of bauxite enters into the solution as different sulfur ions in Bayer digestion process,which adversely affects the alumina production and product quality in many ways.The modeling of different sulfur ions is established via Guassview 5.0,then the target ions are calculated and optimized via the DFT B3 LYP/6-31 G(d,p),so the E_(HOMO)energy and E_(LUMO)energy of S^(2-)、S_(2)^(2-)、SO_(3)^(2-)、S_(2)O_(3)^(2-)and SO_(4)^(2-)are obtained.The calculation results show thatΔE_(LUMO-HOMO)of the five kinds of sulfur ions from high to low is S^(2-)>SO_(4)^(2-)>S_(2)O_(3)^(2-)>S_(2)^(2-)>SO_(2)^(2-).That is to say,in the absence of external oxidants and reducing agents,sulfur in the form of S^(2-)can exist stably in the solution,followed by the form of SO_(4)^(2-),while S_(2)^(2-),SO_(2)^(2-)and S_(2)O_(3)^(2-)are relatively weak in stability,which are consistent with the occurrence and distribution of sulfur ions in digestion solution of high-sulfur bauxite measured by chemical quantitative analysis,thus providing theoretical support for the selective wet desulfurization of high-sulfur bauxite.