CN116590524A - A method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore - Google Patents

Abstract

A method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore comprises the steps of adding water into the ground carbon-containing nickel-molybdenum ore for size mixing, adding sodium alkali, adjusting the initial alkalinity to 130-180 g/L, and adding into a pressure kettle for oxygen pressure leaching to enable molybdenum to enter a solution and inhibit nickel in slag; filtering to obtain leaching liquid and leaching slag, wherein the leaching liquid is sodium molybdate solution, and the leaching slag is nickel-containing slag; washing the leached slag with water to obtain washing slag, drying the washing slag, and then reducing and smelting to obtain a low nickel matte product; and removing impurities from the leaching solution, purifying to obtain a pure sodium molybdate solution, concentrating, crystallizing, filtering and drying to obtain a sodium molybdate product. The invention efficiently realizes the separation of molybdenum and nickel, realizes the separation of nickel and molybdenum in one step by applying an oxygen pressure alkaline leaching process, ensures that the nickel slag rate is more than 99 percent and the molybdenum leaching rate is more than 96 percent, and has the advantages of environmental friendliness, short reaction time and the like.

Description

A method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore

technical field

The invention belongs to the technical field of metallurgy and chemical industry. Specifically, it relates to a process for separating molybdenum and nickel by oxygen pressure alkaline leaching of carbon-containing nickel-molybdenum ore, a method for producing sodium molybdate by removing impurities and purifying the leaching solution, and a method for producing low-matte nickel by reducing and smelting the leaching slag.

Background technique

Nickel and molybdenum are important strategic resources in my country, and are widely used in iron and steel non-ferrous alloys, chemical industry, aerospace and other fields. With the rapid development of my country's economy, the demand for nickel and molybdenum resources continues to increase. Although nickel and molybdenum resources are abundant, most of them are co-associated molybdenum ores, and the ore dressing pressure is high. At the same time, with the continuous exploitation and utilization of traditional nickel and molybdenum resources, the ore grade is getting lower and lower, and the ore dilution is serious.

Carbon-bearing nickel-molybdenum ore, as a kind of polymetallic complex and refractory mineral resource, is mainly distributed in the sedimentary minerals in the black shale layer of the Lower Cambrian system in Northwest Hunan and Guizhou, with abundant reserves and high grade. Nickel-molybdenum ore contains a large amount of carbon and sulfur. Molybdenum and nickel mainly exist in the form of sulfides. The molybdenum minerals are mainly molybdenum molybdenum molybdenum (MoS ₂ ), and the nickel minerals are needle nickel ore, nickel disulfide, and arsenite. . This ore is symbiotically distributed in carbonaceous aggregates with ultra-fine particle size and pyrite. Traditional physical beneficiation and metallurgical techniques are difficult to effectively separate and extract molybdenum and nickel.

The published documents on similar carbon-containing nickel-molybdenum ore treatment processes are mainly as follows:

The Chinese invention patent with publication number CN101086034A discloses a process for extracting molybdenum by wet decomposition of nickel-molybdenum ore. Alkaline solution is used as the leaching solution to leach finely ground nickel-molybdenum ore, and air, oxygen-enriched air or oxygen is added to the pulp during the leaching process. During the leaching process, molybdenum disulfide gradually reacts with oxygen and transforms into sodium molybdate into the solution. Vanadium and tungsten contained in nickel-molybdenum ore also enter the solution at the same time, and sulfur is transformed into sulfur-containing anions such as sulfate and sulfite. Valuable metals such as nickel and copper and iron remain in the slag, which can be further used to extract nickel and copper.

The Chinese invention patent with publication number CN1267740A discloses a process for preparing molybdenum-nickel salt by directly leaching molybdenum-nickel symbiotic raw ore with a weak base and an oxidizing agent. The technological process is to crush the original ore of molybdenum-nickel symbiotic ore through crushing and ball milling, then leaching with weak base and oxidant, filter, distill ammonia, and extract the solution to produce ammonium molybdate, and the raffinate solution is evaporated and concentrated to obtain nickel sulfate. The grade of ore molybdenum is 4.0%-8.0%, the grade of nickel is 2.5%-4.0%, and the grade of sulfur is 23%. The total recoveries of molybdenum and nickel prepared by this method are 80% and 88% respectively.

The Chinese invention patent with the publication number CN110643811A discloses a nickel-molybdenum ore all-wet clean smelting process, including the steps of controlled potential ammonia activation leaching, extraction of molybdenum and nickel from the leaching solution. Nickel-molybdenum ore is firstly leached by controlled potential ammonium activation to obtain leaching solution and leaching residue. The leaching solution uses ion exchange or induced crystallization to extract molybdenum, and then uses ion exchange or solvent extraction to extract nickel to obtain ammonium molybdate that meets the requirements of the national standard. And nickel sulfate products, after extraction, the liquid evaporates and crystallizes to obtain ammonium sulfate.

The Chinese invention patent with the publication number CN109055727A discloses a method for comprehensively recovering nickel and molybdenum in nickel-molybdenum ore, including the following steps: (1) mixing nickel-molybdenum ore and pyrolusite evenly and then oxidizing and roasting to obtain roasted clinker; ( 2) adding the roasted clinker into the ammonia solution for stirring reaction, and after solid-liquid separation, the leaching solution containing nickel ammonium complex ions and molybdate ions and the leaching residue containing manganese are obtained. It can solve the problem of SO ₂ flue gas pollution and the problem of high reduction cost of low-grade pyrolusite.

The traditional extraction process of carbon-containing nickel-molybdenum ore is oxidation roasting-water immersion method, which has problems such as poor equipment, metal recovery rate, and environmental pollution, and has been phased out. Oxygen pressure acid leaching process, sodium hypochlorite method, etc., have problems such as large reagent consumption, long reaction time, long process, and environmental pollution. In the processes disclosed in the above-mentioned patent documents, it is common for nickel and molybdenum to enter the leaching solution at the same time. The production process is long and the leaching solution contains high impurities such as iron, magnesium, and silicon. It is difficult to purify, and the slag output in the middle of the smelting process requires harmless treatment. In order to accumulate and other issues.

Contents of the invention

The object of the present invention is to solve the deficiencies of the above-mentioned prior art, to provide a kind of molybdenum and nickel in carbon-containing nickel-molybdenum ore can be effectively separated under oxygen pressure alkaline leaching, the recovery rate of molybdenum and nickel in the whole process is high, the reaction time is short and environmentally friendly A friendly method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore.

For realizing the purpose of the invention, the technical scheme that the present invention takes is as follows:

The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore comprises the following steps:

(1) Sizing: mixing water and finely ground carbon-containing nickel-molybdenum ore to obtain slurry, adding sodium alkali to the slurry, and adjusting the initial alkalinity to 130-180g/L to obtain a slurry;

(2) Oxygen pressure alkali leaching: add the liquid after pulping into the autoclave, and pass through oxygen to carry out oxygen pressure leaching, so that molybdenum enters the solution and nickel is suppressed in the slag; after filtering, the leaching solution and leaching residue are obtained, and the leaching solution is sodium molybdate solution, the leaching slag is nickel-containing slag;

(3) Washing of leaching slag: washing leaching slag with water and then filtering to obtain washing slag and filtrate;

(4) Reduction smelting: dry the washing slag and then carry out reduction smelting to obtain low nickel matte products;

(5) Impurity removal and purification of leachate: remove impurities and purify the leachate to obtain pure sodium molybdate solution;

(6) Concentrated crystallization: Concentrate the pure sodium molybdate solution, cool and crystallize, filter and dry to obtain sodium molybdate product and mother liquor.

Further, in the above step (1), the pulverized carbon-containing nickel-molybdenum ore is -100 mesh carbon-containing nickel-molybdenum ore; the sodium alkali is sodium hydroxide or a mixture of sodium hydroxide and sodium carbonate; sodium The liquid-solid mass ratio of the alkali solution to the carbon-containing nickel-molybdenum ore is 4 ml to 8 ml: 1 g.

Further, the sodium hydroxide is industrial-grade sodium hydroxide, and the main content of sodium hydroxide is more than 99%; the sodium carbonate is industrial-grade sodium carbonate, and the main content of sodium carbonate is more than 99%.

Further, the composition of the carbon-containing nickel-molybdenum ore contains 2~6wt% nickel, 2~7wt% molybdenum, 19~21wt% sulfur, 20~21.5wt% silicon, 9.5~10.5wt% carbon, 9.5~ 10.5wt%, magnesium 3.2~3.5wt%.

Further, in the above step (2), the reaction temperature of the oxygen pressure alkaline leaching is 110-150° C., the reaction time is 3-6 hours, and the reaction pressure is 1.0-1.6 MPa.

Further, in the above step (3), the filtrate obtained by washing and filtering the leaching residue is returned to step (1) for pulping.

Further, in the above step (4), the smelting temperature of the reduction smelting washing slag is 1450-1650° C., and the smelting time is 2-6 hours.

Further, in the above step (5), the impurity removal and purification of the leaching solution is to first add sodium sulfide solution to the leaching solution to remove heavy metal cation impurities in the sodium molybdate solution; then add barium hydroxide to form barium sulfate precipitation, remove Sulfate in sodium molybdate solution; then add MgCl ₂ solution and ammonia water to generate double salt precipitation and remove phosphate.

Further, in the above step (6), the pure sodium molybdate solution concentrate is cooled to crystallize after the specific gravity is 1.4-1.6g/cm ³ , filtered and dried to obtain the sodium molybdate product and mother liquor, and the mother liquor is returned to the step (1) Blending.

The present invention has the following beneficial effects:

(1) Oxygen pressure alkaline leaching realizes the efficient separation of nickel and molybdenum in carbon-containing nickel-molybdenum ores, nickel into slag, molybdenum into liquid, the whole process is simple and easy, the process is short, and the leaching rate of molybdenum is >96%, and the slag contains Molybdenum<0.25%, nickel slag rate>99%;

(2) The amount of waste gas generated during the reaction process of the oxygen pressure alkaline leaching process is relatively small, and it only needs to be equipped with a conventional waste gas absorption device to achieve standard discharge and basically have no adverse effects on the environment;

(3) Using the oxygen pressure alkaline leaching process, the autoclave can use ordinary carbon steel with low production cost, which can reduce equipment investment by more than 60% compared with the titanium and zirconium pressure autoclave used in the oxygen pressure acid leaching process;

(4) During the oxygen pressure alkali leaching process, more than 98% of silicon and iron and about 60% of magnesium enter the slag, which reduces the difficulty of solution purification;

(5) During the process of adding barium hydroxide to the leaching solution to remove sulfate, barium sulfate precipitation is formed to remove sulfate, and NaOH is also generated, which can reduce the input of sodium hydroxide when the concentrated mother liquor is returned to the slurry;

(6) Low nickel matte is produced by reduction smelting in an electric furnace, which can produce low nickel matte products containing about 23% nickel and 55% iron, which meet the quality requirements of general low nickel matte products. The slag contains nickel ≤0.4%, and the direct nickel recovery rate is ≥88.04%. The production process is simple, and the smelting slag does not need to be harmlessly treated.

The invention selectively oxidizes molybdenum into soluble molybdate and enters the liquid phase by strictly controlling the process conditions, while nickel and the like stay in the slag phase, thereby efficiently realizing the separation of molybdenum and nickel. The invention uses an oxygen pressure alkali leaching process to realize the separation of nickel and molybdenum in one step, the nickel slag rate is >99%, and the molybdenum leaching rate is >96%, and has the advantages of environmental friendliness and short reaction time. It effectively solves the problem that the nickel and molybdenum in the existing process of extracting nickel and molybdenum from carbon-containing nickel and molybdenum ore enters the leaching solution at the same time, the production process is long and the leaching solution contains high impurities such as iron, magnesium and silicon, the purification is difficult, and the intermediate slag output in the smelting process is high. Only after harmless treatment can it be stockpiled and other issues.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

Below in conjunction with embodiment further elaborates content of the present invention.

A method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore, as shown in Figure 1, may further comprise the steps:

(1) Mix -100 mesh carbon-containing nickel-molybdenum ore and water according to the liquid-solid mass ratio of 4-8ml:1g to obtain pulp, and add sodium alkali to the pulp to adjust the initial alkalinity to 130-180g/L to obtain adjusted Serum fluid.

The carbon-containing nickel-molybdenum ore contains 2-6wt% nickel, 2-7wt% molybdenum, 20.76wt% sulfur, 21.18wt% silicon, 9.51wt% carbon, 9.62wt% iron, and 3.28wt% magnesium.

The sodium base is sodium hydroxide or a mixture of sodium hydroxide and sodium carbonate. The sodium hydroxide used is industrial grade sodium hydroxide, and the main content of sodium hydroxide is more than 99%. The sodium carbonate used is industrial grade sodium carbonate, and the main content of sodium carbonate is more than 99%.

(2) Put the liquid after pulping into the autoclave, pass through industrial oxygen to carry out oxygen pressure alkaline leaching, control the reaction temperature at 110-150°C, the reaction time is 3-6 hours, and the reaction pressure is 1.0-1.6MPa, so that molybdenum enters the solution, Nickel is suppressed in the slag, and leachate and leaching slag are obtained after filtration. The leachate is mainly sodium molybdate solution, and the leaching slag is nickel-containing slag.

(3) Wash the leached slag with water and then filter to obtain the washing slag and washing water, and return the washing water to step (1) for pulping.

(4) After the washing residue is dried, the ingredients are sent to reduction smelting. During reduction smelting, the characteristics of silicon, iron, magnesium and calcium in the leaching slag can be used for reduction smelting production, which can save a lot of flux. Using the residual carbon in the leaching slag as part of the reducing agent, silicon and magnesium as the smelting flux, and iron and sulfur as the nickel collector, the smelting temperature is 1450-1650°C and the smelting time is 2-6 hours to obtain low-matte nickel products. The smelting slag contains ≤0.4% nickel and can be stockpiled without harmless treatment.

(5) The leachate is cleaned of impurities. First add sodium sulfide solution to remove heavy metal cation impurities in sodium molybdate solution; then add barium hydroxide to generate barium sulfate precipitation to remove sulfate radicals in sodium molybdate solution; then add MgCl ₂ solution and ammonia water to form double salt precipitation, Phosphate was removed to obtain a pure sodium molybdate solution.

(6) Concentrate the pure sodium molybdate solution until the specific gravity of the concentrated solution is 1.4-1.6g/cm ³ , cool and crystallize, filter and dry to obtain the sodium molybdate product and mother liquor, and the mother liquor can be returned to step (1) for pulping .

Example 1

The carbon-containing nickel-molybdenum ore used in this example was sampled from a certain place in Guizhou Province, and it was a massive material. The material is ground and screened, and the whole amount passes through a 100-mesh sieve. The reagent lime contains 80% calcium oxide, coke particles contain 80% carbon, pyrite contains 42% iron, and the rest reagents are analytically pure.

The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore is as follows:

(1) Add 400g of -100 mesh nickel-molybdenum ore containing 5.2wt% nickel, 4.52wt% molybdenum, 20.76wt% sulfur, 21.18wt% silicon, 9.51wt% carbon, 9.62wt% iron, and 3.28wt% magnesium to liquid. The solid volume to mass ratio is 4:1 (ml/g) for pulping, and sodium hydroxide is added to adjust the initial alkali concentration to 150g/L;

(2) Pour the slurry into a 3L autoclave, pass through oxygen leaching, leaching conditions: reaction pressure 1.2Mpa, reaction temperature 120°C, leaching time 4h, leaching slurry is filtered to obtain leaching slag and filtrate, leaching slag is washed to obtain nickel-containing 5.98 %, molybdenum 0.15% nickel raw material 345g, the nickel slag rate is 99.18%, the molybdenum leaching rate is 97.13%, and the filtrate is sodium molybdate solution;

(3) After the nickel raw material is dried, take 200g and add 12g of lime, 20g of coke particles, and 26g of pyrite, and mix them evenly, then place them in a crucible and perform reduction smelting in a muffle furnace at a melting temperature of 1550°C and a smelting time of 4h. After smelting, 45.6g of low nickel matte product containing 23.08% nickel and 55.95% iron, 0.40% nickel in slag, 88.04% direct nickel recovery rate;

(4) Heat 1.575L sodium molybdate solution to 80°C, add saturated sodium sulfide solution, heat and boil for 10 minutes, let it fully react and let it stand for 3 hours, filter and get the impurity-removed liquid to enter the purification;

(5) Add barium hydroxide to the liquid after impurity removal, the amount of Ba ²⁺ added is controlled according to 0.98 times of the sulfate content in the raw material; then add MgCl ₂ solution and ammonia water, the added amount is 1.1 times of the theoretical amount, the solution The pH value is about 9.5, and the standing time is 5 hours. After filtration, 1.26L of pure sodium molybdate solution containing 13.52g/L of molybdenum is obtained;

(6) Concentrate 1.26L pure sodium molybdate solution until the specific gravity of the concentrated solution is 1.48g/cm ³ , cool and crystallize, filter and dry to obtain 75.8g of Na ₂ MoO ₄ .2H ₂ O product containing 39.25% molybdenum and mother liquor. The recovery rate of molybdenum is 99%. The mother liquor returns to step (1) for pulping.

The total recovery rate of molybdenum in this example reaches 94.22%, and the product quality of sodium molybdate reaches the non-ferrous metal industry standard YS/T1311-2019 secondary product standard, see Table 1.

Table 1 Comparison of non-ferrous metal industry standards and the product of Example 1 (unit: mass fraction/%)

Example 2

The carbon-containing nickel-molybdenum ore used in this example was sampled from a certain place in Guizhou Province, and it was a massive material. The material is ground and screened, and the whole amount passes through a 100-mesh sieve. The reagent lime contains 80% calcium oxide, coke particles contain 80% carbon, pyrite contains 42% iron, and the rest of the reagents are analytically pure.

The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore is as follows:

(1) Add 400g of -100 mesh nickel-molybdenum ore containing 5.98wt% nickel, 6.95wt% molybdenum, 19.36wt% sulfur, 20.45wt% silicon, 10.35wt% carbon, 9.62wt% iron, and 3.46wt% magnesium to liquid. The solid volume mass ratio is 8:1 (ml/g), and the mixed alkali of sodium hydroxide and sodium carbonate is added (sodium hydroxide: sodium carbonate = 7:3), and the initial alkalinity is adjusted to 180g/L to obtain the slurry after liquid;

(2) Put the liquid after pulping into a 3L autoclave, and pass it into industrial oxygen for leaching. The leaching conditions: reaction pressure 1.5Mpa, reaction temperature 150°C, leaching time 6h, leaching slurry is filtered to obtain leaching residue and filtrate, and leaching residue is washed Obtain 351g of nickel raw materials containing 6.76% of nickel and 0.18% of molybdenum, the nickel slag rate is 99.20%, the molybdenum leaching rate is 97.73%, and the filtrate is sodium molybdate solution;

(3) After the nickel raw material is dried, take 200g and add lime 10g, coke grains 22g, pyrite 30g and mix them evenly, then place them in a crucible and perform reduction smelting in a muffle furnace at a melting temperature of 1650°C and a smelting time of 2h. Obtained 42.1g of low nickel matte product containing 28.47% nickel and 53.67% iron, 0.38% nickel in slag, and 88.44% direct nickel recovery;

(4) Take 3.16L of sodium molybdate solution, add it and heat it to 80°C, add saturated sodium sulfide solution, heat and boil for 10 minutes, let it fully react, then let it stand for 5 hours, and filter to get the impurity-removed liquid to enter the purification;

(5) Barium hydroxide is added to the liquid after impurity removal, and the amount of Ba ²⁺ added is controlled according to 0.98 times the sulfate content in the raw material; MgCl ₂ solution and ammonia water are added, and the added amount is 1.1 times the theoretical amount, and the pH value of the solution is at 9.5 or so, stand for 6 hours, get 2.45L of pure sodium molybdate solution containing molybdenum 11.10g/L after filtration;

(6) Concentrate the above 2.45L pure sodium molybdate solution until the specific gravity of the concentrated solution is 1.58g/cm ³ , cool and crystallize, filter and dry to obtain 120g of Na ₂ MoO ₄ .2H ₂ O product containing 39.46% molybdenum and mother liquor, mother liquor Return to step (1) for slurry mixing. The recovery rate of molybdenum is 98.76%.

The total recovery rate of molybdenum in this example is 94.17%, and the product quality of sodium molybdate reaches the non-ferrous metal industry standard YS/T1311-2019 secondary product standard, see Table 2.

Table 2 Comparison of products in Example 2 of the nonferrous metal industry standard (unit: mass fraction/%)

Example 3

The carbon-containing nickel-molybdenum ore used in this example was sampled from a certain place in Guizhou Province, and it was a massive material. The material is ground and screened, and the whole amount passes through a 100-mesh sieve. The reagent lime contains 80% calcium oxide, coke particles contain 80% carbon, pyrite contains 42% iron, and the rest reagents are analytically pure.

The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore, the processing method is as follows:

(1) Add 400g of -100 mesh nickel-molybdenum ore containing 2.52wt% nickel, 2.45wt% molybdenum, 19.87wt% sulfur, 20.36wt% silicon, 9.78wt% carbon, 10.24wt% iron, and 3.45wt% magnesium to liquid. Slurry with a solid volume to mass ratio of 4:1 (ml/g), add sodium hydroxide to adjust the initial alkalinity to 130g/L, and obtain a slurry after slurry;

(2) Put the liquid after pulping into a 3L autoclave, pass through oxygen leaching, leaching conditions: reaction pressure 1.0Mpa, reaction temperature 110°C, leaching time 3h, leaching slurry is filtered to obtain leaching slag and filtrate, leaching slag is obtained by washing 348g of nickel raw material containing 2.88% nickel and 0.11% molybdenum, the nickel slag rate is 99.43%, the molybdenum leaching rate is 97%, and the filtrate is sodium molybdate solution;

(3) After the nickel raw material is dried, take 200g and add 12g of lime, 15g of coke particles, and 12g of pyrite and mix them evenly, then place them in a crucible and perform reduction smelting in a muffle furnace at a melting temperature of 1450°C and a smelting time of 6 hours. Obtained 24.80g of low nickel matte product containing 20.53% nickel and 52.35% iron, 0.15% nickel in slag, and 88.39% direct nickel recovery;

(4) Take 1.56L of sodium molybdate solution, add it and heat it to 80°C, add saturated sodium sulfide solution, heat and boil for 10 minutes, let it fully react, then let it stand for 4 hours, and filter to get the impurity-removed liquid to enter the purification;

(5) Barium hydroxide is added to the liquid after impurity removal, and the amount of Ba ²⁺ added is controlled according to 0.98 times the sulfate content in the raw material; MgCl ₂ solution and ammonia water are added, and the added amount is 1.1 times the theoretical amount, and the pH value of the solution is at 9.5 or so, let it stand for 4 hours, and get 1.21L of pure sodium molybdate solution containing molybdenum 7.8g/L after filtration;

(6) Concentrate 1.21L pure sodium molybdate solution until the specific gravity of the concentrated solution is 1.6g/cm ³ , cool and crystallize, filter and dry to obtain 44.17g of Na ₂ MoO ₄ .2H ₂ O product containing 39.05% molybdenum and mother liquor, mother liquor Return to step (1) for slurry mixing. The recovery rate of molybdenum is 98.68%.

The total recovery rate of molybdenum in this example is 93.85%, and the product quality of sodium molybdate reaches the non-ferrous metal industry standard YS/T1311-2019 secondary product standard, see Table 3.

Table 3 Comparison of non-ferrous metal industry standards and products in Example 3 (unit: mass fraction/%)

Unless otherwise specified, the numerical values of the percentages of each component appearing in the present invention are all percentages by mass.

Claims (9)

1. the method for separating and extracting molybdenum-nickel from carbon-containing nickel-molybdenum ore, is characterized in that, comprises the following steps: (1) Sizing: mixing water and finely ground carbon-containing nickel-molybdenum ore to obtain slurry, adding sodium alkali to the slurry, and adjusting the initial alkalinity to 130-180g/L to obtain a slurry; (2) Oxygen pressure alkali leaching: add the liquid after pulping into the autoclave, and pass through oxygen to carry out oxygen pressure leaching, so that molybdenum enters the solution and nickel is suppressed in the slag; after filtering, the leaching solution and leaching residue are obtained, and the leaching solution is sodium molybdate solution, the leaching slag is nickel-containing slag; (3) Washing of leaching slag: washing leaching slag with water and then filtering to obtain washing slag and filtrate; (4) Reduction smelting: dry the washing slag and then carry out reduction smelting to obtain low nickel matte products; (5) Impurity removal and purification of leachate: remove impurities and purify the leachate to obtain pure sodium molybdate solution; (6) Concentrated crystallization: Concentrate the pure sodium molybdate solution, cool and crystallize, filter and dry to obtain sodium molybdate product and mother liquor. 2. The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore according to claim 1, characterized in that, in the above step (1), the finely ground carbon-containing nickel-molybdenum ore is -100 mesh containing Carbon-nickel-molybdenum ore; the sodium alkali is sodium hydroxide or a mixture of sodium hydroxide and sodium carbonate; the liquid-solid mass ratio of sodium alkali solution to carbon-containing nickel-molybdenum ore is 4 ml to 8 ml: 1 g. 3. the method for separating and extracting molybdenum-nickel from carbon-containing nickel-molybdenum ore according to claim 2, is characterized in that, described sodium hydroxide is technical grade sodium hydroxide, and sodium hydroxide main content is more than 99%; Described sodium carbonate is technical grade sodium carbonate, and the main content of sodium carbonate is more than 99%. 4. the method for separating and extracting molybdenum-nickel from carbon-containing nickel-molybdenum ore according to claim 1 or 2 or 3, is characterized in that, in the composition of described carbon-containing nickel-molybdenum ore, contains nickel 2 ~ 6wt%, molybdenum 2~7wt%, sulfur 19~21wt%, silicon 20~21.5wt%, carbon 9.5~10.5wt%, iron 9.5~10.5wt%, magnesium 3.2~3.5wt%. 5. The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore according to claim 1, characterized in that, in the above step (2), the reaction temperature of the oxygen pressure alkaline leaching is 110-150°C, and the reaction The time is 3 to 6 hours, and the reaction pressure is 1.0 to 1.6MP. 6. The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore according to claim 1, characterized in that, in the above-mentioned step (3), the filtrate obtained by washing and filtering the leached slag is returned to step (1) for pulping . 7. The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore according to claim 1, characterized in that in the above step (4), the smelting temperature of the reduction smelting washing slag is 1450-1650 °C, and the smelting time is 2-2 6h. 8. The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore according to claim 1, characterized in that, in the above step (5), the impurity removal and purification of the leachate is to first add sodium sulfide solution to the leachate , to remove the heavy metal cation impurities in the sodium molybdate solution; then add barium hydroxide to generate barium sulfate precipitation, remove the sulfate radical in the sodium molybdate solution; then add MgCl ₂ solution and ammonia water, generate double salt precipitation, and remove the phosphate radical. 9. The method for separating and extracting molybdenum and nickel from carbon-containing nickel-molybdenum ore according to claim 1, characterized in that, in the above step (6), the concentrated solution of the pure sodium molybdate solution has a specific gravity of 1.4 to 1.6 g/cm ³ , cooling and crystallization, filtering and drying to obtain sodium molybdate product and mother liquor, and returning the mother liquor to step (1) for pulping.