Study On Extraction Of Nickel From A Leaching Solution Of Laterite Ores Through Emulsion Liquid Membrane Technology

Emulsion Liquid Membrane (ELM) Technology has several key advantages in use such as:high efficiency, high selectivity, lowcost and energy saving. Based on these advantages, ELM technology was used for the first time in our research to extract nickel from a leaching solution of laterite ores. The nickel was extracted from the solution by the way of the water/oil/water-type (W/O/W) emulsion liquid membrane technique which contains the flow carrier. Various factors of this process were examined during extraction of the nickel. It was determined that the efficient liquid membrane and technological conditions continually increased the extraction efficiency. Three kinds of liquid membrane systems were selected with the following chemical compositions:NH3-H2O, NaOH and Na2S. The research carried out for this project included the study of:emulsion liquid membrane stability, liquid membrane extraction efficiency, liquid membrane reaction mechanisms, the membrane reactions of emulsion liquid membrane, emulsion breaking method, as well as practical (or applied research)application.Leaching experiments were carried out using the method of acidic leaching under pressure, and the leaching conditions were determined:reaction temperature250℃, stirring speed300r/min, acid ore ratio0.45g(H2SO4)/g(ore), temperature preservation time1.5h. Under the above conditions, leaching liquid composition was acid concentration29.5g/L, Fe3+concentration1.40g/L, Ni2+concentration1.89g/L, the leaching rate of nickel from laterite ores was95%then.Internal water phase complex emulsion liquid membrane method was used to make NH3·H2O system emulsion. By studying the effect of different factors on the stability of the emulsion and extracting of liquid membrane, the conditions of making and separating emulsion under the current system were determined to be:the volume ratio of Span80, TBP, liquid paraffin, kerosene is5:4:2:89, the concentration of internal water phase is1.5mol/L, the volume fraction of oil phase is50%, stirring speed of making emulsion is4000r/min, stirring time of making emulsion is20min. When separating, the emulsion water ratio is1:3, and Ni2+concentration of external water phase is500mg/L, the extracting rate of nickel from laterite ores can reach above90%then.Method of combining the effect of the stability of emulsion and extracting of liquid membrane was used to make emulsion. The conditions of making and separating emulsion under the current system were determined to be:the volume ratio of Span80, TBP, liquid paraffin, kerosene is6:4:2:88, the concentration of internal water phase is0.3mol/L, the volume fraction of oil phase is50%, stirring speed of making emulsion is4500r/min, stirring time of making emulsion is20min. When separating, the emulsion water ratio is1:3, and Ni2+concentration of external water phase is300mg/L, the removing rate of nickel can reach above91%.Based on the advantages of simple process, high enrichment ratio, internal precipitation ELM method was used to make Na2S system emulsion, and the method of combining the effect of the stability of emulsion and extracting of liquid membrane was also used. The conditions of making and separating emulsion under the current system were determined to be:the volume ratio of Span80, TBP, liquid paraffin, kerosene is5:4:2:89, the concentration of internal water phase Na2S is0.3mol/L, the volume fraction of oil phase is50%, stirring speed of making emulsion is4000r/min, stirring time of making emulsion is20min, the emulsion water ratio is1:3, and Ni2+concentration of external water phase is300mg/L, the removing rate of nickel can reach above91%.The emulsion liquid membrane system stability was studied through the way of conductivity method and polychrome microscopy method. As for the water/oil-type (W/O) emulsion, the continuous phase has been changed into oil phase and the emulsion is more stabilized by the conductivity getting smaller. The result by conductivity method shows that, the emulsion liquid membrane system is stabilized when the conductance of the emulsion is below5us/cm. The result by polychrome microscopy method indicates that the emulsion is more stabilized with the particle size being smaller and well-distributed, The extracting efficiency of nickel is higher with the emulsion being more stabilized.Dynamics process of Ni2+transferring by ELM was studied using differential method and apparent activation energy method. The extracting power of the ELM on nickel was discussed theoretically to guide the application of ELM technology used on the hydrometallurgy of laterite ores. Results show that the time series is2, while the concentration series is1in using NH3·H2O system ELM, which indicates that the time series is bigger than the concentration series; the extracting ratio of the system increases with the increasing of the temperature, the reaction activation energy is big enough to show that the reaction process belongs to chemical process. In the NaOH and Na2S system, the time series and the concentration series is equal to be1, which shows that the ELM reaction is pseudo-first-order reaction; the reaction activation energy is small which shows that the reaction in the NaOH and Na2S system is diffusion-controlled reaction process.Demulsification is an important work which influences the application of ELM technology. Ultrasonic demulsification, centrifugal demulsification, heating demulsification, heating-centrifugal demulsification and ultrasonic-heating demulsification were used in our work. Results of studying demulsification show that the demulsification rate of three kinds of ELM system of NH3·H2O, NaOH and Na2S can reach98%、96%and98%. On studying the demulsification, demulsification of the ELM systems of NaOH and Na2S were found to be harder than that of the system of NH3·H2O, which is because the solid sediment in the internal water phase generated in the former two systems,"the solid stabilizing" made the demulsification more difficult. The higher demulsification rate was attained by extending emulsion breaking time in our work.The membrane reactions were studied respectively by FT-IR spectra and Raman spectrum. Comparing the emulsion spectrogram before the separation with the emulsion spectrogram after the separation, we pointed out the reaction product in the membrane, and confirmed the reaction happening in the membrane. Contrasted the original oil spectrogram and the spectrogram of the oil after demulsification, estimated whether the oil phase can be reused preliminary. Collected broken emulsion oil phase, made the emulsion repeated and extracted nickel again. The results showed that, when the oil phase was recycle by four times, the extraction efficiency basically unchanged. This conclusion was the same with the three kinds of liquid membrane system.Extraction of Nickel from laterites ore by pressure acid leaching then emulsion liquid membrane, in accordance with" make emulsion,then separation, then emulsion breaking,then make emulsion again, and then separation", such a cycle of experimental research for practical system. The results showed that extraction efficiency can reach above92%. At the same time, obtained the principle process of extraction nickel for "the pressure acid leaching then emulsion liquid membrane". The three kinds of liquid membrane system were all effective, and the liquid membrane could be cyclic utilization.This thesis provided the technological process, which would be beneficial attempt for the low consumption, high efficiency and clean production on the laterites ore resource utilization.