两种白钨矿碱分解溶液的蒸发与结晶过程研究

本文采用旋转薄膜、玻璃真空蒸发器,对两种组成不同的白钨矿的苛性钠浸出溶液,选择了两种蒸发温度（90℃和80℃）下的蒸发-结晶试验。蒸发-结晶过程是按照流程设计的要求,所进行的承上启下的中间过程。目的是取得含有与不含有钼酸钠的钨酸钠结晶,以方便萃取分离钨/钼过程使用,并节省调整酸度过程的耗酸量;同时,取得高浓度氢氧化钠溶液,以便循环使用苛性钠试剂,并节省浸出试剂的消耗量。试验结果表明,对于含钼的钨酸钠-苛性碱浸出溶液而言,蒸发-结晶温度为90℃时（-0.098 MPa,56 r/min）,尽管,氢氧化钠的回收率达到了尽善尽美,ηNa OH=100%,但是,美中不足的结晶率分别是：ηW=84.39%和ηM o=69.60%。即钨酸钠和钼酸钠的循环率分别为：ρw=16.17%和ρMo=31.29%。对于不含钼的钨酸钠-苛性碱溶液而言,蒸发-结晶温度为80℃,（-0.098 MPa,56 r/min）,尽管,氢氧化钠的回收率接近完美,ηNa OH=100.0%,但是,美中不足是钨酸钠的循环率达到了,ηW=17.00%。两种结果表明,蒸发-结晶温度范围为80~90℃下,氢氧化钠的回收率,尽如人意,美中不足的是钨酸钠的循环率达到了16.1%~17.0%,钼酸钠的循环率达到31.29%。钨酸钠和钼酸钠之间的分离系数范围是1.21~1.56。

Studies on Recovery Efficiencies of Phenols from Phenol Fraction Using Alkali Treatment

Experiments were conducted for the extraction of phenols from the phenol fraction obtained from the coal tar distillate. The phenol fraction for the present investigation has been procured from Visakhapatnam Steel Plant, Visakhapatnam whose composition is known. The phenol fraction from coal tar distillate can be treated for extracting phenols using caustic soda. An attempt has been made to find out whether the existing practice of using only 8%-15% can be modified by increasing the strength of sodium hydroxide and also explore the possibilities of substituting the sodium hydroxide with KOH as an extractant. The different streams of liquids obtained during experimentation have been analyzed by gas chromatograph. Salient features of the study are that higher concentrations of the alkali significantly improved the separation efficiencies of phenols and also regenerate the phenolate with higher phenol content. Increase in the alkali strength has greatly improved the separation as well as the phenol content in the regenerated phenols. Disposal of effluents containing phenols may lead to environmental problem of ground water pollution and the study throws a light on the removal of phenols from the effluents to the extent possible by using higher strength alkali solutions.