N235从石煤酸浸液中萃取提钒的研究
发布时间：2018-11-27 18:38
【摘要】：目前,对于石煤酸浸液常采用二(2-乙基己基)膦酸酯(P204)萃取,而该工艺一般需用石灰调整酸浸液pH值为2,萃取前需对酸浸液进行还原处理,萃取后再对反萃液进行氧化。流程复杂,药剂成本较高,且在调节pH时固液分离也较为困难。同时,由于P204为阳离子萃取剂,所以对于酸浸液中大量存在的铁、铝、镁等杂质分离效果一般,较难分离完全。为了缩短工艺流程,降低成本,本文提出了在较低的pH值下采用叔胺类萃取剂N235(三烷基胺)萃取石煤酸浸液,水洗后再反萃回收钒。试验研究了N235对酸浸液中主要离子的萃取性能。结果表明,在同等条件下,N235萃取V(V)的萃取率显著高于V(Ⅳ)。升高溶液pH有利于V(V)的萃取,在pH为1时V(V)的单级萃取率可达97.21%。在pH=0~2时,N235对Fe2+、Al3+、Mg2+、PO43-、Si2O32-的萃取能力均较弱,而控制体系pH值小于1.5,可以显著降低N235对Fe3+的萃取。整体上Fe3+、Al3+、Mg2+、PO43-、Si2O32-的共萃程度较弱,对钒萃取影响较小。研究确定了N235萃取石煤酸浸液的工艺参数。在25℃下,有机相为40%N235、60%煤油,萃取相比O/A为1:4,萃取6分钟,经过2级萃取,钒的萃取率达97.82%;洗涤条件为55℃水洗,洗涤相比O/A为1:1,洗涤10分钟,两级硫酸洗脱率为52.5%;反萃剂采用0.8 mol/L碳酸钠溶液,反萃过程中,反萃相比O/A为3:1,反萃6分钟,经2级反萃,钒的总反萃率大于99%。而且大部分杂质离子被分离,其中铁、铝、钙、镁等主要杂质离子的去除率均高于95%。对于反萃后有机相作红外光谱分析可知,其与萃取前有机相红外图谱特征峰几乎一致,说明N235萃取剂经过反萃后可以循环利用。采用饱和容量法以及斜率法研究了N235萃取钒的机理,确定N235萃取钒的萃合物为[R3NH]4[H2V10O28]。通过试验,拟合数据后得到N235萃取钒的反应平衡常数K为195.434 mol-1·L·s-1,且此时,萃取反应焓变H=-10.683 kJ/mol,自由能变G=-13.076 kJ/mol,熵变S=8.032 J/(mol·K)。说明N235萃取钒的反应为放热反应,萃取温度的升高不利于N235萃取钒。自由能变G为负值,说明反应可以自发进行,反应较易发生。
[Abstract]:At present, bis (2-ethylhexyl) phosphonic acid ester (P204) is often used to extract the acid leachate of stone coal, but this process usually requires lime to adjust the pH value of the acid leaching solution to 2, and the acid leaching solution should be reduced before extraction. After extraction, the stripping solution is oxidized. The process is complex, the medicament cost is high, and the solid-liquid separation is difficult to adjust pH. At the same time, because P204 is a cationic extractant, it is difficult to separate the impurity such as iron, aluminum, magnesium and so on. In order to shorten the technological process and reduce the cost, the tertiary amine extractant N235 (trialkylamine) was used to extract the bituminous coal acid leachate at low pH value. The extraction properties of main ions in acid leaching solution by N235 were studied. The results showed that the extraction rate of V (V) by N235 was significantly higher than that of V (鈪，
本文编号：2361696
[Abstract]:At present, bis (2-ethylhexyl) phosphonic acid ester (P204) is often used to extract the acid leachate of stone coal, but this process usually requires lime to adjust the pH value of the acid leaching solution to 2, and the acid leaching solution should be reduced before extraction. After extraction, the stripping solution is oxidized. The process is complex, the medicament cost is high, and the solid-liquid separation is difficult to adjust pH. At the same time, because P204 is a cationic extractant, it is difficult to separate the impurity such as iron, aluminum, magnesium and so on. In order to shorten the technological process and reduce the cost, the tertiary amine extractant N235 (trialkylamine) was used to extract the bituminous coal acid leachate at low pH value. The extraction properties of main ions in acid leaching solution by N235 were studied. The results showed that the extraction rate of V (V) by N235 was significantly higher than that of V (鈪，
本文编号：2361696
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