| There are rich zinc oxide ore resources in China.The advantages of ammonia method are simple process,leaching solution can be recycled,little environmental pollution and so on. At present, although ammonia leaching treatment and purification technology has been mature,because that the lack of effective zinc electrowinning additive,the directly zinc electrowinning process is difficult to control and the final products is also difficult to get zinc plate.To solve the problem,study of zinc electrowinning additive is carried out in this paper.The new additive of benzyl-trimethyl-ammonium chloride, benzyl-trimtriethyl-ammo nium chloride were synthesised and single molecular amine ramification,macromolecular amine ramification,multi molecular amine ramification were homemade.The analysis of products were characterized by NMR and IR tests.The effects of different additives on current efficiency and surface morphology of zinc cathode were investigated.The results show that although there are the same groups in similar organic additives,because of the molecularstructure,carbon chain length are different,the effects on zinc electrowinning are not the same.The better additives of TA(improve surface morphology),macromolecular amine ramification and multi molecular amine ramification;TB(increase current efficie ncy),tetramethyl-ammonium chloride and benzyl-trimethyl-ammonium chloride were sele cted.The optimum concentrations of macromolecularamine ramification and multi mole cular amine ramification were 2m L·L-1,the optimum concentrations of tetramethyl-amm onium chloride and benzyl-trimethyl-ammonium chloride were 50mg·L-1 and 75mg·L-1.And there were large effects of macromolecularamine ramification and multi molecular amine ramification on cathodic polarization by analysis of electrochemical test.Through the different combination and concentration of additives were used,the results show that current efficiency was 95.37% with dense and smooth surface morphology, under the optimum combination and concentration of multi molecular amine ramification of 2m L·L-1 and benzyl-trimethyl-ammonium chloride of 65mg·L-1.Through the study of zinc electrowinning process,the results show that the optimum conditions including polar distance of 3cm,current density of 400A·m-2,time of 4h.When the initial concentration was more than 20g·L-1,the current efficiency was more than 90% with dense and smooth surface morphology under the optimum conditions.The optimum conditions of zinc electrowinning was stability and repeatability.The composite additive used in NH3-(NH4)2SO4-H2 O system and NH3-(NH4)2CO3-H2 O system were carried out.It can also increase the current efficiency and improve the surface morphology.The current efficiency were 92.59% and 93.52% with dense and smooth surface morphology.Through the analysis of electrochemical test,the above additive could improve cathodic polarization,so that lead to the rise of polarization overvoltage.It was conducive to crystal nucleus formation and grain refinement with dense and smooth surface morphology.But the current efficiency would be reduced if the cathode polarization was too strong. |
