| Nickel is a nearly silver-white,hard and ductile metal element.It has good plasticity,corrosion resistance and magnetic properties.It is mainly used in steel,superalloy,electroplating and battery fields.Nickel is the main element of superalloys.The nickel content in high-end superalloys is generally more than 60%.By 2020,the demand for superalloys in China will be about 40,000 tons,corresponding to a market space of 9.05 billion yuan.At present,the actual output of superalloys in China is about 20,000 tons.The composite growth rate of superalloy demand in the next seven years is expected to exceed 20%.Nickel mainly comes from nickel sulfide ore and laterite nickel ore.With the decrease of nickel sulfide ore resources,the use of laterite nickel ore increases gradually.There are more than 20 kinds of impurity elements in nickel sulfide ores.Among them,Pb,As,Sb and Sn are difficult to remove.As high-performance superalloys control impurity elements very strictly,laterite nickel ores with simple element composition are more suitable for preparing high-purity nickel for superalloys.Therefore,it is particularly important to develop a new method for preparing high purity nickel from laterite nickel ore.In this paper,the preliminary impurity removal leaching solution from laterite nickel ore by hydrochloric acid leaching under atmospheric pressure developed by the author's research group was used as raw material to carry out the related research work,such as deep purifying the solution,high purity nickel electrodepositing,analysis method screening and establishing for annlysis impurity elements in high purity nickel metal and high purity nickel sulfate solution.The main conclusions are as follows:(1)An inductively coupled plasma atomic emission spectrometry(ICP-AES)method for the analysis of impurity elements in high purity nickel solution and high purity nickel metal was established.The accurate determination of trace impurity elements in high purity nickel solution and high purity nickel metal by ICP-AES was realized.The optimum parameters of the instrument are determined by experiments:the RF power is 1350W,the flow rate of the atomizer is 0.5L/min,the observation distance is 15mm,and the pump speed of the peristaltic pump is 1.0mL/mim.Matrix matching,standard addition and MSF correction methods were used to determine the high purity nickel solution.When the standard concentration was 0.10,0.20 mg/L and nickel concentration was 5 g/L,the three methods all obtained good recovery rates.The linear correlation coefficient was greater than 0.9996,the recovery rate was 95.0-102%,RSD was between 2.09-4.63%.Then The MSF method has the widest linear range(0.02-0.5 mg/L)and the lowest detection limit(0.002 mg/L).When the standard concentration is 0.02,0.06 mg/L and nickel concentration is 15 g/L,the results show that only MSF method can get accurate results.Its linear correlation coefficient is 0.9999,linear range is 0.02-0.1 mg/L,detection limit is 0.002 mg/L,recovery is 95,0-105%,RSD is between 3.92-4.60%.The result of analysis were basically consistent with that of glow discharge mass spectrometry(GD-MS)when the actual samples were tested by MSF method,which further verified the accuracy and accuracy of the method.The new method not only has strong anti-interference ability,simple operation,economy and practicability,but also has high precision,low detection limit,lower detection limit(0.0001%)and scope better than the national standard atomic absorption spectrometry(0.001%).It provides an important methodological means for the determination of trace impurity elements in high purity samples.(2)A high purity nickel solution(Nickel-cobalt ratio higher than 5000)for electrodepositing 99.99%nickel metal was prepared by deep purifying of the initial impurity removal leaching solution by solvent extraction.The optimum composition of organic phase is 10%Cyanex 272,5%TBP and 85%sulfonated kerosene.The optimum extraction conditions were as follows:saponification rate 60%,initial pH 3.5,water phase pH 5.10-5.70,optimum ratio 1.5:1(O/A),mixing oscillation time 5 min.The theoretical extraction stage was calculated by the extraction isotherms and McCabe-Thiele diagram.When the ratio was 1:1(O/A),the theoretical extraction stage was 4,when the ratio was 1.5:1(O/A),and the theoretical extraction stage was 3.Then the theoretical extraction stage was respectively simulated by 3 and 4 counter-current extraction.The results were consistent with the theoretical series.Dilute sulfuric acid solution was used for the reverse extraction of organic phase,and the optimum conditions of reverse extraction were sulfuric acid concentration 50g/L,and 2:1(O/A)ratio.(3)The electrodeposition process of high purity nickel solution was studied,and 99.99%of high purity nickel metal was prepared.The effects of boric acid concentration,pH,nickel ion concentration,current density,polar moment,electrolysis time,electrolysis temperature,sodium ion concentration and magnesium ion concentration on cell voltage,cathode current efficiency and energy consumption were investigated.Experiments show that when boric acid concentration was 3 g/L,initial pH was 3,nickel ion concentration was 60 g/L,current density was 200 A/m2,polar moment was 30 mm,electrolysis time was 1.5 h,electrolysis temperature was 40 C,sodium ion concentration was less than 20 g/L,magnesium ion concentration was less than 1.5 g/L,cell voltage was low to 2.82V,current efficiency was 95.7%,energy consumption was low to 2.690 kw·h/t.Under these conditions,nickel electrolysis obtained with smooth surface and the test result show that it met the requirements of brand Ni9999 in national standard GB/T 6516. |
PDF Full Text Request