Method for preparing MHP from laterite-nickel ore by using active magnesium oxide and recycling tail water

Abstract

The invention discloses a method for preparing MHP from laterite-nickel ore by using active magnesium oxide and recycling tail water, which comprises the following steps: carrying out high-pressure acid leaching treatment on the laterite-nickel ore, removing iron and aluminum to obtain a solution to be refined, adding a certain amount of active magnesium oxide, and fully reacting; concentrating the reacted mixed solution to obtain clear liquid and solid-containing slurry; the solid-containing slurry is filtered and washed to obtain MHP, clear liquid and filtrate, after water washing liquid is collected, a certain amount of tail water treatment reagent is added, the filtrate is filtered after reaction, the filtrate is recycled as acid leaching water or washing water, magnesium and calcium-containing solid residues obtained after tail water treatment are subjected to reselection to separate out by-products of calcium sulfate and magnesium hydroxide, and magnesium hydroxide is calcined to obtain active magnesium oxide; further, the method is used for preparing the MHP. The method for preparing the MHP from the laterite-nickel ore by using the active magnesium oxide and recycling the tail water is simple in process and low in cost, the production efficiency can be remarkably improved, and recycling of magnesium resources and water resources is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and more specifically to a method for preparing MHP from laterite nickel ore by using active magnesium oxide and recycling tail water. Background Art

[0002] In the face of climate change, countries around the world are actively promoting the low-carbon transformation of energy, and the new energy vehicle industry has also developed rapidly. Nickel (Ni), cobalt (Co), and lithium (Li), as key raw materials for power batteries, are also experiencing a rapid increase in demand.

[0003] At present, the main process for preparing nickel is the wet refining of laterite nickel ore. In a high temperature and high pressure environment, laterite nickel ore is selectively leached with sulfuric acid to extract Ni, Co, Mg, Mn, Cu, etc. The ore pulp is neutralized, washed, and impurities are removed before adding a precipitant to obtain the intermediate product MHP (nickel cobalt hydroxide). At present, the precipitation process mostly uses sodium hydroxide as a precipitant. Although this method is simple in process, the consumption of the precipitant sodium hydroxide is large, and due to the strong alkalinity of sodium hydroxide, the generated precipitate particles are small, which increases the difficulty of sedimentation and filtration during solid-liquid separation, affecting production efficiency. In addition, the filter cake has a high moisture content, which increases the cost of subsequent transportation and processing. Using sodium hydroxide as a precipitant, while preparing MHP, Na + Ions, including Na + Direct discharge of ion tail water will pollute land and water resources, and the cost and difficulty of tail water treatment are high, which increases production costs. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a wet refining method for laterite nickel ore in which the precipitate is easy to settle and filter and the tail water can be recycled.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water comprises the following steps:

[0007] (1) high pressure acid leaching of laterite nickel ore to obtain a solution to be refined;

[0008] (2) adding active magnesium oxide to the solution to be extracted in step (1) to allow it to react fully;

[0009] (3) the mixed solution after the reaction is concentrated to obtain a clear liquid and a solid slurry;

[0010] (4) filtering and washing the solid slurry to obtain MHP;

[0011] (5) using a tail water treatment reagent to treat the tail water consisting of the clear liquid in step (3), the filtrate in step (4) and the washing liquid, wherein the tail water treatment reagent is quicklime, modified quicklime or slaked lime, which reacts with the tail water to obtain a solid slag containing calcium and magnesium, and the solid slag containing calcium and magnesium is separated by gravity separation to obtain calcium sulfate and magnesium hydroxide, and the magnesium hydroxide is calcined to prepare active magnesium oxide for use in step (2), thereby realizing the circulation of magnesium resources.

[0012] In the above method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water, in step (1): the acid used for high-pressure acid leaching of laterite nickel ore is sulfuric acid solution.

[0013] In the above method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water, in step (2): the magnesium oxide content in the activated magnesium oxide is 88-99.8wt.%, preferably 92.5-95.5wt.%; the citric acid activity value of the activated magnesium oxide is 10-100s, preferably 10-40s.

[0014] The above method for preparing MHP from laterite nickel ore using active magnesium oxide and recycling tail water comprises the following steps: in step (2): the amount of active magnesium oxide added is the amount of Ni in the solution to be extracted in step (1); 2+ and Co 2+ 0.5 to 1.0 times, preferably 0.6 to 0.75 times the total mass.

[0015] In the above method for preparing MHP from laterite nickel ore using active magnesium oxide and recycling tail water, in step (3): the mixed solution after the reaction is concentrated by natural sedimentation using a thickener, and the clear liquid and the solid slurry are obtained by layering.

[0016] In the above method for preparing MHP from laterite nickel ore using active magnesium oxide and recycling tail water, in step (4) and step (5): filtration is performed by plate and frame filter pressing, vacuum filtration or centrifugal filtration.

[0017] The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water, in step (5): the tail water treatment reagent is added by dry powder addition or slurry addition, preferably slurry addition; the tail water treatment reagent slurry concentration is greater than or equal to 0wt.% and less than or equal to 70wt.%, preferably 30wt.% to 55wt.%; the slurry is mechanically stirred, and the stirring rate is 100 to 500r / min, preferably 200 to 300r / min; the slurry mixing time is 3 to 300min, preferably 5 to 10min; the amount of tail water treatment reagent added is 0.85 to 2.50 times the total mass of Mg in the tail water to be treated, preferably 1.50 to 1.84 times; the tail water treatment temperature is 10 to 60°C, preferably 20 to 40°C, and the reaction time between the tail water and the tail water treatment reagent is 10 to 180min, preferably 30 to 60min.

[0018] In the above method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water, the modified quicklime preparation method in step (5) is as follows:

[0019] (a) adding aminosilane coupling agent and quicklime to ethanol and stirring to react for 0.5 to 2 hours;

[0020] (b) adding carboxymethyl-β-cyclodextrin to water, stirring and mixing, and then adding to the mixture obtained in step (a), stirring and reacting for 1 to 3 hours;

[0021] (c) adding magnesium hydroxide seed particles to the mixture obtained in step (b), stirring and heating to 60-80° C. and maintaining stirring for 2-5 hours, filtering after the reaction is completed, and drying the filter residue to obtain modified calcium oxide.

[0022] The method for preparing MHP from laterite nickel ore using active magnesium oxide and recycling tail water comprises the following steps: in step (a), the volume ratio of aminosilane coupling agent to ethanol is 0.01-0.1:1, and the mass volume ratio of quicklime to aminosilane coupling agent is (100-200):1 g / mL; in step (b), the mass volume ratio of carboxymethyl-β-cyclodextrin to water is (300-400):1 g / L, and the amount of carboxymethyl-β-cyclodextrin is 1.1-1.5 times the amount of aminosilane coupling agent; and in step (c), the amount of magnesium hydroxide seed particles added is 5-10% of the mass of carboxymethyl-β-cyclodextrin.

[0023] The method for preparing MHP from laterite nickel ore using active magnesium oxide and recycling tail water comprises the following steps: in step (a), the volume ratio of aminosilane coupling agent to ethanol is 0.05:1, and the mass volume ratio of quicklime to aminosilane coupling agent is 150:1 g / mL; in step (b), the mass volume ratio of carboxymethyl-β-cyclodextrin to water is 350:1 g / L, and the amount of carboxymethyl-β-cyclodextrin is 1.2 times the amount of aminosilane coupling agent; and in step (c), the amount of magnesium hydroxide seed particles added is 6% of the mass of carboxymethyl-β-cyclodextrin.

[0024] The separation of solid slag containing calcium and magnesium utilizes the density difference between magnesium hydroxide and calcium sulfate and adopts gravity separation method to separate the two.

[0025] The chemical reactions involved in the present invention are mainly as follows:

[0026] Active magnesium oxide is added to the solution, and magnesium oxide hydrolyzes:

[0027] MgO+H2O→Mg(OH)2↓

[0028] Magnesium hydroxide ionizes in aqueous solution:

[0029] Mg(OH)2→Mg 2+ +2OH -

[0030] OH ionized from magnesium hydroxide - The ions combine with the nickel ions (or cobalt ions) in the solution to form nickel hydroxide precipitates (or cobalt hydroxide precipitates):

[0031] Mg(OH)2+NiSO4→Ni(OH)2↓+MgSO4

[0032] Mg(OH)2+CoSO4→Co(OH)2↓+MgSO4

[0033] When the active magnesium oxide and the laterite nickel ore acid leaching solution generate nickel hydroxide precipitation, the tail water is a solution containing MgSO4. To treat the tail water, one or more of quicklime or slaked lime is added:

[0034] CaO+H2O→Ca(OH)2↓

[0035] Ca(OH)2+MgSO4→Mg(OH)2↓+CaSO4↓

[0036] After the tail water is treated, the solid slag containing calcium and magnesium is separated to obtain by-products of calcium sulfate and magnesium hydroxide, and the magnesium hydroxide is calcined to prepare active magnesium oxide.

[0037]

[0038] The technical solution of the present invention achieves the following beneficial technical effects:

[0039] (1) In the present invention, active magnesium oxide is used to prepare MHP from laterite nickel ore, and the added amount is only Ni in the laterite nickel ore acid leaching solution. 2+ 0.5 to 1.0 times the total amount of ions, because the OH that can be ionized per unit mole of active magnesium oxide - The traditional NaOH precipitant ionizes OH - ions, so the unit consumption is small and the cost is low.

[0040] (2) The addition of active magnesium oxide produces a weaker alkaline solution, and the nickel hydroxide precipitate produced during use is easy to settle and filter, which effectively avoids the current problems of sedimentation and difficulty in filtering during the use of NaOH precipitant, and significantly improves production efficiency.

[0041] (3) When active magnesium oxide is added to prepare MHP from laterite nickel ore, the tail water generated is mainly a solution containing MgSO4. After the introduction of quicklime, modified quicklime or slaked lime, the filtrate can be used as acid leaching water or MHP washing water after filtration. Compared with the tail water containing Na2SO4 generated by the NaOH precipitant, the treatment method is efficient and simple, with low cost. The treated tail water can be recycled to achieve zero water discharge.

[0042] (4) The solid slag containing calcium and magnesium obtained after tail water treatment is separated by gravity separation to obtain by-products of calcium sulfate and magnesium hydroxide. The magnesium hydroxide is calcined to prepare active magnesium oxide, which is then used in the sedimentation process of MHP, thus realizing the recycling of magnesium resources and reducing production costs.

[0043] (5) The process of the present invention is simple, the cost is low, and the MHP is easy to settle and filter, which can significantly improve the production efficiency. The tail water treatment is simple and efficient. After the tail water treatment, the filtrate is recycled to achieve zero water discharge. The magnesium hydroxide obtained after solid slag separation is calcined to generate high-activity magnesium oxide, which is used as a precipitant, thereby achieving the recycling of magnesium resources.

[0044] (6) First, an aminosilane coupling agent is used to modify calcium oxide to increase its hydrophobicity and reduce its hydrophilicity, thereby slowing down the reaction between calcium oxide and water, and avoiding the formation of more calcium hydroxide precipitates while generating magnesium hydroxide precipitates, which collide with the magnesium hydroxide precipitates and agglomerate with them, making it difficult for the magnesium hydroxide to settle, filter and wash.

[0045] (7) In order to quickly generate larger particles of magnesium hydroxide that are easy to settle, filter and wash, and to avoid the poor dispersibility of aminosilane coupling agent modified calcium oxide in tail water; the carboxyl group of carboxymethyl-β-cyclodextrin and the amino group of aminosilane coupling agent are used to form a salt, so that the aminosilane coupling agent modified calcium oxide is compounded with carboxymethyl-β-cyclodextrin, and then the magnesium hydroxide seed particles are combined with the hydroxyl group of carboxymethyl-β-cyclodextrin through hydrogen bonds, so that the magnesium hydroxide seed particles and calcium oxide are organically compounded, and the magnesium hydroxide seed particles provide crystal nuclei for the magnesium hydroxide generated by the reaction. The calcium hydroxide generated by the slow reaction of calcium oxide with water is dissolved in water and reacts with magnesium ions in the tail water to form a magnesium hydroxide precipitate that can quickly adhere to the surface of the magnesium hydroxide seed particles, so that the newly generated magnesium hydroxide with finer particles is converted into magnesium hydroxide with larger particle size; the problems of small magnesium hydroxide particle size, easy agglomeration of crystals, and difficulty in settling, filtering and washing in the magnesium hydroxide production process by the calcium hydroxide method are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention is a process flow diagram of a method for preparing MHP from laterite nickel ore by using active magnesium oxide and recycling tail water. DETAILED DESCRIPTION

[0047] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0048] Example 1

[0049] Refer to Figure 1 As shown in Table 1, the chemical composition of the leaching solution of laterite nickel ore after high-pressure, sulfuric acid solution leaching and removal of iron and aluminum is shown in Table 1.

[0050] Table 1. Chemical composition of laterite nickel ore acid leaching solution Unit: g / L

[0051]

[0052] Take 5L of the leachate in a beaker, put it into a constant temperature water bath with stirring, add 13.09g (0.6 times the total mass of Ni and Co) of active magnesium oxide with a MgO content of 93.5wt.% and a citric acid activity value of 22s and stir well. After the reaction is completed, pour it into the test thickener, observe the solid-liquid separation, record the sedimentation time, and obtain clear liquid A and solid slurry. After the solid slurry is vacuum filtered, the filter cake is washed with water and filtered again, and the two mixed filtrate B and clear liquid A are treated as tail water, and the obtained filter cake is MHP. The comparison of the effects of active magnesium oxide and sodium hydroxide as precipitants under the same conditions is shown in Table 2.

[0053] Table 2. Comparison of the effects of activated magnesium oxide and sodium hydroxide as precipitants

[0054]

[0055] As can be seen from Table 2, the method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water of the present invention has a slightly higher Ni content in MHP than that of the traditional sodium hydroxide as a precipitant, a lower filter cake moisture content, and a much higher sedimentation rate than sodium hydroxide. It has a good sedimentation rate and filtration rate, and the unit consumption of the precipitant is 766 kg, which is less than half of that of sodium hydroxide (1588 kg).

[0056] Take 350 ml of tap water, add 125.3 g (calculated as Ca mass, 1.50 times the total mass of Mg in the tail water to be treated) of quicklime with a purity of 80 wt.% to prepare the slurry to obtain lime milk. The slurry is prepared by mechanical stirring at a stirring rate of 250 r / min and a stirring time of 10 min.

[0057] Take 5L of tail water consisting of filtrate B and clear liquid A in a beaker, place in a water bath at 30°C, slowly pour in the slurry-adjusted lime milk, and fully stir for 40 minutes. After stirring, vacuum filter for 15 minutes to obtain calcium- and magnesium-containing solid slag and filtrate C. The water content of the calcium- and magnesium-containing solid slag after drying is calculated to be 28.66%. The calcium- and magnesium-containing solid slag after drying is reselected to separate byproducts of calcium sulfate and magnesium hydroxide. The magnesium hydroxide is calcined to prepare active magnesium oxide, which is recycled as a precipitant.

[0058] The changes of indicators before and after tail water treatment are shown in Table 3.

[0059] Table 3. Chemical composition of tail water before and after treatment Unit: g / L

[0060]

[0061] As can be seen from Table 3, the main metal ions in the tail water are Mg 2+ Ion solution, after adding slaked lime, generates precipitate containing magnesium and calcium. Mg in filtrate C 2+ The ion concentration is less than 1g / L and can be recycled as acid leaching water or washing water, thus achieving zero discharge of tail water.

[0062] Example 2

[0063] The chemical composition of the leaching solution of laterite nickel ore after high-pressure, sulfuric acid solution leaching and removal of iron and aluminum is shown in Table 4.

[0064] Table 4. Chemical composition of laterite nickel ore acid leaching solution Unit: g / L

[0065]

[0066] Take 5L of the leachate in a beaker, put it into a constant temperature water bath with stirring, add 15.07g (0.7 times the total mass of Ni and Co) of active magnesium oxide with a MgO content of 95wt.% and a citric acid activity value of 33s, stir it thoroughly, pour the slurry into a thickener, observe the solid-liquid separation and record the sedimentation time to obtain a clear liquid A and a solid slurry. After the solid slurry is vacuum filtered, the filter cake is washed with water and filtered again, and the two mixed filtrate B and the clear liquid A are treated as tail water, and the obtained filter cake is MHP. The comparison of the effects of active magnesium oxide and sodium hydroxide as precipitants under the same conditions is shown in Table 5.

[0067] Table 5. Comparison of the effects of activated magnesium oxide and sodium hydroxide as precipitants

[0068]

[0069] As can be seen from Table 5, the method of the present invention for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water has a Ni content in MHP that is equivalent to that of traditional sodium hydroxide as a precipitant, a low filter cake moisture content, a much higher sedimentation rate than sodium hydroxide, a good sedimentation rate and a filtration rate, and a unit consumption of the precipitant is also much lower than that of sodium hydroxide.

[0070] Take 350 ml of tap water, add 137.7 g (calculated as Ca mass, 1.75 times the total mass of Mg in the tail water to be treated) of quicklime with a purity of 90 wt.% to prepare the slurry to obtain lime milk. The slurry is prepared by mechanical stirring at a stirring rate of 150 r / min and a stirring time of 20 min.

[0071] Take 5L of tail water consisting of filtrate B and clear liquid A in a beaker, put it in a water bath at 40°C, slowly pour in the slurry-adjusted lime milk, and stir it thoroughly for 60 minutes. After stirring, vacuum filter it for 15 minutes to obtain calcium- and magnesium-containing solid slag and filtrate C. The water content of the calcium- and magnesium-containing solid slag after drying is calculated to be 27.95%. The calcium- and magnesium-containing solid slag after drying is reselected to separate by-products of calcium sulfate and magnesium hydroxide. The magnesium hydroxide is calcined to prepare active magnesium oxide, which is recycled as a precipitant.

[0072] The changes of indicators before and after tail water treatment are shown in Table 6.

[0073] Table 6. Chemical composition of tail water before and after treatment Unit: g / L

[0074]

[0075] It can be seen from Table 6 that the main metal ions in the tail water are Mg 2+ Ion solution, after adding slaked lime, generates precipitate containing magnesium and calcium. Mg in filtrate C 2+ The ion concentration is less than 1g / L and can be recycled as acid leaching water or washing water, thus achieving zero discharge of tail water.

[0076] Example 3

[0077] The modified calcium oxide powder prepared by the following method is used to treat the tail water in this embodiment:

[0078] (a) adding N-aminoethyl-3-aminopropylmethyldimethoxysilane and quicklime with a purity of 90 wt.% to ethanol and stirring for 2 h; the volume ratio of N-aminoethyl-3-aminopropylmethyldimethoxysilane to ethanol is 0.05:1, and the mass volume ratio of quicklime to N-aminoethyl-3-aminopropylmethyldimethoxysilane is 150:1 g / mL;

[0079] (b) adding carboxymethyl-β-cyclodextrin to water, stirring and mixing, and then adding to the mixture obtained in step (a), stirring and reacting for 1.5 hours; the mass volume ratio of carboxymethyl-β-cyclodextrin to water is 350:1 g / L, and the amount of carboxymethyl-β-cyclodextrin is 1.2 times the amount of N-aminoethyl-3-aminopropylmethyldimethoxysilane;

[0080] (c) adding magnesium hydroxide seed particles to the mixture obtained in step (b), wherein the amount of magnesium hydroxide seed particles added is 6% of the mass of carboxymethyl-β-cyclodextrin, heating to 70° C. with stirring and maintaining the stirring reaction for 5 h, filtering after the reaction is completed, and drying and crushing the obtained filter residue to obtain modified calcium oxide.

[0081] Take 350 ml of tap water, add 137.7 g of modified quicklime to prepare the slurry to obtain lime milk. The slurry is prepared by mechanical stirring at a stirring rate of 150 r / min and a stirring time of 20 min.

[0082] Take 5L of tail water in Example 2, put it in a water bath at 40°C, slowly pour in the slurry-adjusted lime milk, and stir it thoroughly for 60 minutes. After stirring, vacuum filter it for 9 minutes to obtain calcium- and magnesium-containing solid slag and filtrate C. The water content of the calcium- and magnesium-containing solid slag after drying is calculated to be 28.23%. The calcium- and magnesium-containing solid slag after drying is reselected to separate byproducts of calcium sulfate and magnesium hydroxide. The magnesium hydroxide is calcined to prepare active magnesium oxide, which is recycled as a precipitant. The changes in indicators before and after tail water treatment are shown in Table 7.

[0083] Table 7. Chemical composition of tail water before and after treatment Unit: g / L

[0084]

[0085] It can be seen from Table 7 that the main metal ions in the tail water are Mg 2+ Ion solution, after adding modified calcium oxide powder, generates precipitate containing magnesium and calcium. Mg in filtrate C 2+The ion concentration is less than 1g / L and can be recycled as acid leaching water or washing water, thus achieving zero discharge of tail water.

[0086] Comparing Table 7 with Table 6, the modified lime or quicklime is used to treat the tail water. The composition of the filtrate after treatment is not much different, and both have good effects. The water content of the calcium and magnesium solid slag obtained by using modified lime to treat the tail water is not much different (28.23% and 27.95% respectively), but the vacuum filtration time is significantly reduced compared with lime as a tail water treatment reagent. It can be seen that the calcium and magnesium solid slag is easier to filter when the tail water is treated with modified lime.

[0087] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water, characterized in that: The following steps are involved: (1) high pressure acid leaching of laterite nickel ore to obtain a solution to be refined; (2) adding active magnesium oxide to the solution to be extracted in step (1) to allow it to react fully; (3) the mixed solution after the reaction is concentrated to obtain a clear liquid and a solid slurry; (4) filtering and washing the solid slurry to obtain MHP; (5) using a tail water treatment reagent to treat the tail water consisting of the clear liquid in step (3), the filtrate in step (4) and the washing liquid, wherein the tail water treatment reagent is quicklime, modified quicklime or slaked lime, which reacts with the tail water to obtain a solid slag containing calcium and magnesium, and the solid slag containing calcium and magnesium is separated by gravity separation to obtain calcium sulfate and magnesium hydroxide, and the magnesium hydroxide is calcined to prepare active magnesium oxide for use in step (2), thereby realizing the circulation of magnesium resources.

2. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 1, characterized in that: In step (1), the acid used for high-pressure acid leaching of laterite nickel ore is a sulfuric acid solution.

3. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 1, characterized in that: In step (2), the magnesium oxide content in the active magnesium oxide is 88-99.8 wt.%, preferably 92.5-95.5 wt.%; the citric acid activity value of the active magnesium oxide is 10-100 s, preferably 10-40 s.

4. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 1, characterized in that: In step (2): the amount of active magnesium oxide added is the amount of Ni in the solution to be extracted in step (1). 2+ and CO 2 + 0.5 to 1.0 times, preferably 0.6 to 0.75 times the total mass.

5. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 1, characterized in that: In step (3): the mixed solution after the reaction is concentrated by natural sedimentation using a thickener, and the clear liquid and the solid slurry are obtained by layering.

6. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 1, characterized in that: In step (4) and step (5): filtration is performed by plate and frame filtration, vacuum filtration or centrifugal filtration.

7. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 1, characterized in that: In step (5), the tail water treatment reagent is added by dry powder or slurry, preferably slurry; the tail water treatment reagent slurry concentration is greater than or equal to 0wt.% and less than or equal to 70wt.%, preferably 30wt.% to 55wt.%; mechanical stirring is used for slurry adjustment, and the stirring rate is 100 to 500r / min, preferably 200 to 300r / min; the slurry adjustment time is 3 to 300min, preferably 5 to 10min; the amount of tail water treatment reagent added is 0.85 to 2.50 times the total mass of Mg in the tail water to be treated, calculated on a Ca mass basis, preferably 1.50 to 1.84 times; the tail water treatment temperature is 10 to 60°C, preferably 20 to 40°C, and the reaction time between the tail water and the tail water treatment reagent is 10 to 180min, preferably 30 to 60min.

8. A method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to any one of claims 1 to 7, characterized in that: The modified quicklime preparation method in step (5) is as follows: (a) adding aminosilane coupling agent and quicklime to ethanol and stirring to react for 0.5 to 2 hours; (b) adding carboxymethyl-β-cyclodextrin to water, stirring and mixing, and then adding to the mixture obtained in step (a), stirring and reacting for 1 to 3 hours; (c) adding magnesium hydroxide seed particles to the mixture obtained in step (b), stirring and heating to 60-80° C. and maintaining stirring for 2-5 hours, filtering after the reaction is completed, and drying the filter residue to obtain modified calcium oxide.

9. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 8, characterized in that: In step (a), the volume ratio of the aminosilane coupling agent to ethanol is 0.01-0.1:1, and the mass volume ratio of quicklime to the aminosilane coupling agent is (100-200):1 g / mL; in step (b), the mass volume ratio of carboxymethyl-β-cyclodextrin to water is (300-400):1 g / L, and the amount of carboxymethyl-β-cyclodextrin is 1.1-1.5 times the amount of the aminosilane coupling agent; in step (c), the amount of magnesium hydroxide seed particles added is 5-10% of the mass of carboxymethyl-β-cyclodextrin.

10. The method for preparing MHP from laterite nickel ore using activated magnesium oxide and recycling tail water according to claim 8, characterized in that: In step (a), the volume ratio of aminosilane coupling agent to ethanol is 0.05:1, and the mass volume ratio of quicklime to aminosilane coupling agent is 150:1 g / mL; in step (b), the mass volume ratio of carboxymethyl-β-cyclodextrin to water is 350:1 g / L, and the amount of carboxymethyl-β-cyclodextrin is 1.2 times the amount of aminosilane coupling agent; in step (c), the amount of magnesium hydroxide seed particles added is 6% of the mass of carboxymethyl-β-cyclodextrin.

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