Study On The Influencing Factors Of Iron And Aluminium Removal By Sodium Jarosite Precipitation In Nickel Containing Leaching Solution

With the depletion of nickel sulfide deposits and the increase in the nickel demand,laterite nickel ore is becoming an important resource for nickel processing.High-pressure acid leaching（HPAL）technology is a mature hydrometallurgical method for the treatment of laterite nickel ore that can rapidly decompose laterite nickel ore at high temperatures（≥200℃）.However,during the decomposition process,it is difficult to achieve selective leaching of nickel,and the iron and aluminum in the leaching solution can cause problems such as gel precipitation and extractant poisoning during the nickel hydroxide precipitation（MHP）process.In this study,Morowali’s laterite nickel ore leaching solution was used as the initial solution,and the iron and aluminum were removed by the jarosite precipitation method,and sodium sulfate reagent was added to promote the precipitation of jarosite.The behavior of iron and aluminum ions in sulfate solution was investigated,and based on the saturation index,the ionic morphology of iron and aluminum in the sulfate solution and solid phase was calculated by using Visual MINTEQ software at a given temperature and p H.The species of hydroxyl ions for iron and aluminum appear to increase with p H and temperature.When the temperature is maintained at 90°C,sodium jarosite precipitates at p H 1.4,while alunite precipitates easily at p H 1.5.The two-stage precipitation of sodium jarosite method was used to remove iron and aluminum from the laterite nickel ore leaching liquid.The main objective of the first stage precipitation is to remove most of the iron and part of the aluminum in the nickel leachate,reduce the loss of nickel,and investigate the effects of p H value,reaction time,temperature,sodium sulfate addition amount and different neutralising agents（Ca CO₃,Ca O,Na OH）on iron,aluminum removal rate and nickel loss rate during the first stage precipitation process.The results show that the concentration of iron and aluminum decreases with the increase of p H and time.The results of the X-ray diffractometer（XRD）study showed that around the p H value of1.71,a good crystalline phase predicted as sodium jarosite was formed during the precipitation process.Due to the interaction of calcium carbonate（Ca CO₃）with sulfuric acid at p H 2.32,the gypsum（Ca SO₄）phase dominates in the solid residue,the formation of the iron phase is not visible,and only a small peak is considered to be sodium yellow potassium iron alum.At p H 2.3,the iron removal rate did not change significantly as the reaction time increased from 2 h to 6 h.p H 2.3,reaction time 4h,iron and aluminum removal rates have reached 97.18%and 26.74%,respectively,so these p H and reaction time were selected as the best conditions for p H and time experiments.Iron and aluminum also increase with the increasing in temperature,as higher temperatures increase the hydrolysis of ions,thereby increasing the rate of precipitation,and according to experiments,the optimal temperature is 90℃.The addition of sodium sulfate is less significant than the addition of sodium sulfate to the increase in sodium concentration in solution,and the addition of 3.64 g of sodium sulfate per liter is sufficient for the precipitation process.Of the three precipitating agents,calcium oxide（Ca O）and sodium hydroxide（Na OH）produce less sediment weight compare to Ca CO₃,but Ca CO₃ has the highest iron removal rate and an aluminum removal rate comparable to Ca O.Ca CO₃ sample also have the fastest filtration rates compared to Na OH and Ca O samples,which are correlated with the larger particle size of Ca CO₃ samples,based on particle size analyzer（PSA）analysis results.Therefore,Ca CO₃ was chosen as the appropriate precipitant.Under optimized conditions,the precipitation rates of iron and aluminum in the first stage can reach 95.82%and 25.73%,respectively.The second stage of precipitation is based on the first stage of precipitation filtrate obtained under optimized conditions as the initial solution,the main goal is to remove most of the aluminum and residual iron in the nickel leachate,reduce the loss of nickel,and investigate the effect of p H value and reaction time on the precipitation rate during the second stage precipitation process.In the second stage,aluminum is removed in a higher p H range（from 3 to 4.5）due to its lower hydrolysis compared to iron.The results show that the aluminum removal rate increases with the increase of p H,and when the p H value is 4.5,the aluminum removal rate is the highest,which is 99.99%.However,approximately 44.50%nickel co-precipitation was observed at this p H.Considering the loss of nickel,the p H of 3.5 was chosen as the optimal p H for aluminum removal.The effect of reaction time was examined between1h and 6h,and over time,the removal rate of aluminum did not change significantly,about 99.22%of iron and 87.10%of aluminum were removed within 1h,and the best time was selected for 1h.Under the optimization conditions,the total iron removal rate and aluminum removal rate of the two stages reached 99.91%and 90.64%respectively,and the total nickel loss did not exceed 0.34%.42 Figures,32 Tables,94 References...