| With the progress and development of the society,the human living standard has gradually improved,and the requirements for environmental quality have been increasing.During the developing process of the human society,it is inevitable that people need to use the alloy or zinc products.When facing the increasing resources exhaustion and environmental destruction,resources utilization of zinc residue has been a general trend.There are numerous zinc residue utilization technologies,among them the alkaline leaching process is widely accept by researchers due to its unique advantages.During the process of alkaline leaching method,the properties of alkaline solution and the leaching conditions will greatly affect the final product yield.In this study,alkaline sodium hydroxide solution was selected as leaching solution because that it has a significant singular selectivity for zinc.The phase analysis of the samples was carried out by X-ray diffraction(XRD),the possible reaction processes and mechanisms were discussed by comparing the characteristics of the diffraction patterns that were before and after leaching.Firstly,Experiments toward five aspects(the leaching temperature.leaching liquid concentration,leaching time,liquid-solid ratio,leaching speed)were conducted to investigate the Zn leaching from waste residue and the influences of impurity ions(Pb,Cu,Cd and Cr)on leaching.Secondly,the experiment was carried out on the leaching solution with zinc powder,and the best optimum conditions were optimized by adding the amount of zinc powder,adding reaction time and adding reaction temperature.Thirdly.the zinc sulfide product was synthesized in the reaction of the purified solution and the sodium sulfide solution,the effects of the reaction time,the reaction temperature and the(rate)on productivity were also investigated.The main outcomes are listed below:(1)The scanning electron microscopy and the energy spectrum results showed that zinc's occurrence mode was relatively simple,mainly existing in the form of zinc oxide.In this experiment,sodium hydroxide solution was used to leach zinc from industrial waste.The maximum leaching rate was about 89.5%under appropriate conditions(fixed speed of 250 r·min-1,leaching time of 120 min,sodium hydroxide concentration of 5 mol L-1,solid-liquid ratio of 1:15 and leaching temperature of 75 ?).(2)The effects of three factors on leaching rate were investigated,we found that the optimum leaching conditions were zinc dosage of 0.1 g(zinc concentration of 2 g·L-1),the leaching temperature of 25 0 C and the leaching time of 120 min.The effects of the three factors on the removal of four impurity ions were different,the concentrations of four kinds of ions declined with the increase of the leaching time,high temperature might dissolve a part of leached zinc into the leaching solution,while the experiment temperature inconsistenly affected the concentrations of four ions.For Cu,the effect of temperature is not significant on it,its ion concentration in solution is not obvious,and the amount of zinc is positively correlated with the decrease of copper ion.The effect of leaching time on Cu is little,The rate of change is not obvious.As to Pb,the addition of zinc has a significant effect on it.The more the dosage is,the faster the concentration of lead ions decreases,in other words,the change of the ion concentration is larger;Leaching temperature of its impact there may be a reverse solution process,that is,a period of its ion concentration first increase,after the process of reduction,that is to say its removal rate of the first increase after the phenomenon of increased,it is obvious in leaching time on the impact of Pb before 90min.And the increase of Cd concentration in Cd and Cd can be reduced obviously,that is,the content of Cd is decreased significantly.For the temperature,the occurrence of Pb is related to the occurrence of Pb The effect of purification time on Cd is relatively small,but from 90min to 120min between the removal rate of a rising process,that is.this time significantly increased.For Cr,the effect of temperature on its removal rate was negatively correlated,the temperature increased to increase the ion concentration of Cr.and the removal rate decreased.(3)The reaction temperature and reaction time slightly affected the purity of zinc sulfide,while the dosing quantity of sodium sulfide(the molar rate of Na2S and ZnO22-)dominantly affected the product purity.The best reaction conditions in this study were concluded:the optimum molar rate of Na2S and ZnO22-was 1.1,the reaction time was 40 min and the best reaction temperature was 65 ?.The optimal mass fraction of zinc sulfide was 94.05%through the investigation of the reaction conditions. |
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