聚合氯化铝去除浸出液中单宁酸的影响因素及机理

Influencing Factors and Mechanism of Polyaluminum Chloride to Removing Tannic Acid in Leaching Solution

湿法炼锌中采用单宁酸(TA)络合沉淀法回收金属锗,导致富集单宁酸的锌浸出液进入电解液,影响锌的析出。采用聚合氯化铝(PAC)为混凝剂,考察了混凝剂投加量、溶液pH值、溶液温度、搅拌时间和搅拌强度对去除锌浸出液中单宁酸的影响。对比研究了单宁酸去除前后对阴极锌电化学特性的影响,进一步探讨了PAC混凝去除单宁酸的去除机理。结果表明,在PAC投加量100 mg/L、溶液pH值4.5、温度35℃、搅拌时间10 min和搅拌强度100 r/min条件下,单宁酸的去除效果最佳,去除率可达到94%,锌离子保留率在93%以上;PAC对单宁酸的去除机制是吸附电中和与架桥协同作用;单宁酸富集会增加电解液的阴极极化程度,抑制锌的析出,单宁酸经PAC混凝去除后,电解液的阴极极化程度降低,有利于锌的析出。

The tannic acid(TA)complex precipitation method is used in the hydrometallurgical zinc smelting to recover metal germanium,which causes the zinc leaching solution enrich in tannic acid to enter the electrolyte and affect the precipitation of zinc.In this study,polyaluminum chloride(PAC)is used as a coagulant,and the effects of coagulant dosage,leachate pH,leachate temperature,stirring time and stirring intensity on the removal of tannic acid in the zinc leaching solution are investigated.The effect of tannic acid before and after removal on the electrochemical characteristics of cathode zinc is compared,and the removal mechanism of PAC coagulation to remove tannic acid is further discussed.The results show that when the dosage of PAC is 100 mg/L,the pH value of the solution is 4.5,the temperature is 35℃,the stirring time is 10 min,and the stirring intensity is 100 r/min,the removal effect of tannic acid is the optimal and has a removal rate of up to 94%.At this point,the retention rate of zinc ions is above 93%.The removal mechanism of PAC for tannic acid is the synergistic effect of adsorption,electric neutralization and bridging.The enrichment of tannic acid will increase the cathodic polarization of the electrolyte and inhibit the precipitation of zinc.The removal of tannic acid can reduce the cathodic polarization of the electrolyte,which is beneficial to the precipitation of zinc.