辉钼矿超声电氧化分解新工艺的研究

【作者】 贾丽娟；

【导师】 钟宏；

【作者基本信息】 中南大学 ， 化学工艺， 2008， 硕士

【摘要】 由于辉钼矿的焙烧氧化工艺存在着资源利用率低、金属综合回收率不高、释放的二氧化硫气体污染环境等弊端,而全湿法分解工艺操作条件苛刻、氧化剂消耗量大、运输困难、成本高,因此研究新的分解辉钼矿的分解方法势在必行。超声电氧化工艺就是以电氧化工艺为研究对象,将超声波外场强化与矿物的电氧化分解工艺有机结合,以求从根本上解决现存工艺的弊端,实现企业的清洁生产和提升企业的综合竞争能力。通过对电氧化工艺的机理以及试验研究的基础上,发现了电氧化工艺钼浸出率和电解电流效率低的原因:电极表面生成的惰性膜阻滞了反应的进行。而超声波产生微射流能削弱或减弱边界层,加大传质速度,破坏或溶解矿物表面的钝化膜和阻力膜,使矿物表面裸露出来,扩大反应界面。提出采用复合外场（电场+超声场）的方法来强化产物与浸出剂等的扩散、剥离、快速化学溶解或氧化来破坏惰性膜,促进辉铝矿电氧化浸出过程中电化学反应的顺畅进行。以石磨做电极用单因素试验和正交试验考察了电解质浓度、液固比、pH值和电解电压、电解时间对超声电氧化工艺的影响,得到了超声电氧化工艺分解辉钼矿的最佳工艺条件:在超声波作用方式为每隔15min发射3min、电解质NaCl浓度为20%、矿浆初始pH为10、电解电压为3.5v、矿浆液固比L/S为50、电解温度为25℃的条件下Mo浸出率和电解电流效率分别为:91.9%和191.8%。经试验研究发现石墨电极存在着能耗大、易损坏等弊端,因此对电解槽体系进行了设计与优化,优化后的电极以DSA做阳极,不锈钢做阴极,并在新的电解体系下对超声电氧化工艺条件作了进一步的试验研究,电压由3.5伏降低到了3.0伏,钼的浸出率由91.9%上升到了94.2%,电流效率上升到了196.5%。另外,本文阐述了超声波对电氧化过程的影响以及电流效率高的原因:超声空化作用能进一步分散矿浆,增加液固反应的活性中心,使电解产生的NaClO的利用效率增加;在超声场作用下,覆盖的硫膜极易被剥离,最终被电解产生的强氧化剂——NaClO所氧化而进入水相;矿浆中的溶解氧可以作为氧化剂参与辉钼矿的分解浸出过程;矿浆中矿物颗粒与阳极的碰撞可以导致辉钼矿的直接阳极氧化;超声空化产生强氧化性的羟基自由基（·OH,φ⁰=2.8 v）直接参与氧化分解MoS₂（超声波有能量的给予,计算电流效率时未考虑了超声波电耗的消耗）,同时提出了超声波作用下的反应机理。更多还原

【Abstract】 According to the shortcomings of the roasting process （pollution of flue gas containing sulphur, poor metal comprehensive recovery） and clean process-hydrometallurgy of molybdenite, studying new decomposition method of molybdenite is necesary. Ultrasound electro-oxidation process was sudyied which can combine electric field and ultrasound on the basis of electro-oxidation process in order to solve the shortcomings of roasting process and process-hydrometallurgy.After studying the mechanism and experiments of electro-oxidation process,the reason of low Mo leaching rate and current efficiency was inert membranes during electro-oxidation process, which block the reaction.To promote electrochemistry reactions in electro-oxidation process for molybdenite, it’s necessary that mass transfer among leaching agent, mineral and product should be strengthened by using of the coupling between electric field and ultrasound, so that inert membranes could be destroyed by the role of stripping, rapid dissolution or chemical oxidation.Ultrasound electro-oxidation process was studied using of carbon electrodes in self made cell. The optimal reaction conditions were obtained.The optimal conditions are as follows: the emission of ultrasonic of three minutes per 15 minutes, electrolyte concentration C_NaCl of 10%, pulp initial pH of 10, cell voltage of 3.5 v, temperature of 25℃, liquid to solid ratio L/S of 50. Current efficiency and Mo leaching rate can reach 91.9% and 191.8% under the optimal conditions.There were many shortcomings of carbon electrode according to the small size experiments. In order to further perfect the ultrasonic electro-oxidation process, its cell system was designed and optimized. Verification tests’ results show that the new electrolysis device can achieve the coupling between electric field and ultrasound, and strengthen molybdenite oxidative decomposition and leaching. The voltage was decresed from 3.5V to3.0V. Mo leaching rate was increased from 91.9% to 94.2% and current efficiency increased to 196.5%.The influence of ultrasound to electrodes was studied. Reasonable explanation of high current efficiency in the electrolysis process in the novel process was put forward.The first reason is ultrasonic cavitation disperse pulp increasing activation center, which enhance the efficiency of hypochlorite. The second reason is inert membranes destroyed by the role of stripping, rapid dissolution and chemical oxidation entering solution. The third reason is that oxygen which dissolveing in solution decompose molybdenite. The fourth is the possibility of direct collision anodic oxidation and direct oxidation by ultrasound. The last one is that hydroxy oxidates and decomposes molybdenite. The mechanistic of decomposition molybdenite was brought forward at last.更多还原