| Hydrometallurgy of zinc is the mainstream process of zinc production.However,the quality of electric zinc,current efficiency can be affected due to the presence of excessive organic impurities during zinc hydrometallurgy,and result in high consumption of zinc powder in solution purification.Therefore,it is imperative to study the effect of organic impurities on the purification of zinc sulphate solution,the process of zinc electrowinning and the removal of organic impurities in solution.The zinc sulfate solution was employed as research objects in this paper,the gelatin and tannic acid were used as organic additives.Three parts of research content were conducted.Firstly,the effects of organic additives on the purification and electrowinning process of wet zinc smelting were investigated,and the limits in solution were determined.Then,in view of the current situation that the activated carbon could not be used due to the deactivation of activated carbon in the production process of acetic acid,a new process of microwave regeneration of zinc-containing waste activated carbon was proposed.Lastly,the regenerated product was used for the adsorption removal of tannic acid in zinc sulfate solution.The main research contents and results are as follows:(1)The effects reaction times and different concentrations of tannic acid and gelatin on the purification efficiency,cell voltage,energy consumption and current efficiency were studied,and the influence limits of tannic acid and gelatin in the purification liquid and electrolyte were determined.The results showed that the removal rate of copper by metal zinc powder and electric furnace zinc powder was reduced by 6%-13%,the removal rate of cadmium was reduced by 11%-48%,the removal rate of cobalt was reduced by 13%-38%,and the removal rate of nickel was reduced 21%-49%when the content of gelatin or tannic acid in the zinc sulfate cleaning solution was 50-400 mg/L.The effect of tannic acid and gelatin on the zinc electrowinning process indicated that the limit of tannic acid in the electrolyte was10 mg/L,and the limit of gelatin was 50 mg/L.When the content of tannic acid reached 50 mg/L,the cell voltage increased by 22 mV and the DC unit consumption increased 8.25%.The zinc sheet was remelted and burned.(2)Microwave regeneration of zinc-containing waste activated carbon was carried out,and the effects of temperature and time on iodine adsorption value and yield were investigated.A new process for microwave regeneration of zinc-containing waste activated carbon was proposed,the microwave absorbing properties of zinc-containing waste activated carbon and its components at different temperatures were measured.The optimized process conditions of microwave regenerated activated carbon were obtained.When the regeneration temperature was900oC and the holding time was 40 min,the specific surface area of activated carbon after regeneration was 743.6 m~2/g,the iodine adsorption value was 880.62 mg/g,and the average pore diameter was 28.83 nm.The conventional regeneration optimization process conditions were:regeneration temperature 900oC,holding time2 h,the specific surface area of the regenerated activated carbon obtained at this time was 628.5 m~2/g,the iodine adsorption value was 816.61 mg/g,and the average pore diameter was 30.88 nm.The results show that the zinc-containing waste activated carbon can absorb microwave well in microwave field and the microwave regeneration had a significantly higher ratio than the conventional regenerated micropores.The regeneration time was shortened by 80 min and the specific surface area was increased by 115.1 m~2/g.The microwave regeneration process can effectively open the blocked pores to form new pores.(3)The microwave regeneration of waste activated carbon was used as raw material to carry out the experimental study on the adsorption and removal of tannic acid in zinc sulfate solution.The optimal process conditions were as follows:oscillation time 200 min,activated carbon dosage 0.35 g,pH 4.0.The adsorption equilibrium data was obtained at different temperatures and analyzed by Langmuir and Freundlich adsorption isotherm.The Langmuir adsorption capacity of the regenerated product to tannic acid was 14.42 mg/g.The pseudo-second-order kinetic model was used to analyze the experimental results,and the initial adsorption rate and rate constant of the model were obtained.It can be found that the pseudo-second-order kinetic model can better describe the adsorption process.The concentration of tannic acid in the solution after adsorption was less than 7.5 mg/L to reach the limit of tannic acid in the electrolyte(less than 10 mg/L).The new technology of adsorption and removal of tannic acid by microwave regeneration spent catalyst had the advantages of short process,good regeneration performance of activated carbon and high adsorption efficiency of tannic acid.It had certain reference for the removal of organics. |
PDF Full Text Request