阅读说明：本技术 一种赤泥资源化-土壤化处置的方法 (Red mud recycling-soil treatment method ) 是由 胡振光 周康根 彭长宏 张雪凯 陈伟 雷清源 黄颖 于 2019-03-12 设计创作，主要内容包括：本发明公开了一种赤泥资源化-土壤化处置的方法,该方法是将赤泥采用浓酸浸出,得到浸出液和富硅渣；富硅渣和碱性盐类混合焙烧,得到硅肥产品；浸出液通过萃取铁和反萃铁,得到含铁溶液；同时得到萃铁余液；所述萃铁余液采用碱性物质调高pH沉淀钪和钛,得到富钪钛渣和沉淀后液I；富钪钛渣采用稀酸浸出,得到粗钛白和含钪溶液；沉淀后液I采用碱性物质进一步调高pH沉淀铝,得到富铝渣和沉淀后液II；含铁溶液和沉淀后液II用于赤泥脱碱,得到含钠溶液和脱碱赤泥。在综合回收赤泥中的钛、钪、铝、硅等元素基础上,利用所得含铁/钙废液用于赤泥脱碱,形成赤泥资源化-土壤化综合处置技术,可以有效改善赤泥污染的问题。(The invention discloses a red mud resource-soil treatment method, which comprises the steps of leaching red mud by concentrated acid to obtain leachate and silicon-rich slag; mixing and roasting the silicon-rich slag and alkaline salts to obtain a silicon fertilizer product; extracting iron and back extracting iron from the leachate to obtain an iron-containing solution; obtaining the raffinate at the same time; adjusting the pH of the iron extraction raffinate to precipitate scandium and titanium by using an alkaline substance to obtain scandium-rich titanium slag and a precipitated liquid I; leaching the scandium-rich titanium slag by dilute acid to obtain coarse titanium white and a scandium-containing solution; the pH of the precipitated liquid I is further increased by adopting an alkaline substance to precipitate aluminum, so that aluminum-rich slag and a precipitated liquid II are obtained; the iron-containing solution and the precipitated solution II are used for dealkalizing the red mud to obtain a sodium-containing solution and dealkalized red mud. On the basis of comprehensively recovering titanium, scandium, aluminum, silicon and other elements in the red mud, the obtained iron/calcium-containing waste liquid is used for dealkalizing the red mud to form a red mud resource-soil comprehensive treatment technology, so that the problem of red mud pollution can be effectively solved.)

1. A method for red mud resource-soil treatment is characterized by comprising the following steps: the method comprises the following steps:

1) leaching the red mud by concentrated acid to obtain leachate containing aluminum, iron, calcium, sodium, titanium and scandium and silicon-rich slag;

2) mixing and roasting the silicon-rich slag and alkaline salts to obtain a silicon fertilizer product;

3) extracting iron and back extracting iron from the leachate to obtain an iron-containing solution; obtaining the iron extraction raffinate containing aluminum, calcium, sodium, titanium and scandium;

4) adjusting the pH of the iron extraction raffinate to precipitate scandium and titanium by using an alkaline substance to obtain scandium-rich titanium slag and a precipitated liquid I; leaching the scandium-rich titanium slag by using dilute acid to obtain coarse titanium white and a scandium-containing solution;

5) the pH of the precipitated liquid I is further increased by adopting an alkaline substance to precipitate aluminum, so that aluminum-rich slag and a precipitated liquid II are obtained;

6) and the iron-containing solution and the precipitated solution II are used for dealkalizing the red mud to obtain a sodium-containing solution and dealkalized red mud.

2. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: in the concentrated acid leaching process, concentrated hydrochloric acid is used as a leaching agent, the dosage of the concentrated hydrochloric acid is 0.8-1.6 times of the theoretical molar quantity of aluminum, iron, calcium, sodium, titanium and scandium contained in the dissolved red mud, the solid-to-solid ratio of a leaching solution is 2-10 mL/1g, the leaching temperature is 50-100 ℃, and the leaching time is 2-6 hours.

3. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: the alkaline salt comprises at least one of calcium oxide, calcium carbonate, calcium hydroxide, sodium hydroxide and sodium carbonate.

4. The method for resource-soil treatment of red mud according to claim 1 or 3, wherein the method comprises the following steps: the conditions in the roasting process are as follows: the mass ratio of the alkaline salts to the red mud is 0.2-2: 1, the roasting temperature is 300-1000 ℃, and the roasting time is 2-6 h.

5. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: a quaternary ammonium type extracting agent is adopted in the process of extracting iron; the quaternary ammonium type extracting agent comprises at least one of hexadecyl trimethyl ammonium chloride, trioctyl methyl ammonium chloride, octaalkyl trimethyl ammonium chloride, dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride; the extraction conditions were: compared with the volume ratio of O/W of 0.5-10: 1, the extraction temperature is 15-60 ℃, and the extraction time is 10-60 min.

6. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: in the process of back extraction of iron, water or dilute acid solution is used as a back extractant, and the back extraction conditions are as follows: compared with the volume ratio of O/A of 0.5-2: 1, the back extraction temperature is room temperature-40 ℃, and the back extraction time is 2-20 min.

7. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: in the process of precipitating scandium and titanium, adjusting the pH of the iron extraction raffinate to 0.5-2 by using alkali, and reacting for 0.5-6 h at the temperature of room temperature-50 ℃.

8. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: in the dilute acid leaching process, at least one of sulfuric acid, hydrochloric acid and nitric acid is used as a leaching agent, the concentration of hydrogen ions in a leaching system is 0.5-2 mol/L, the liquid-solid ratio is 2-10 mL:1g, the leaching temperature is 60-100 ℃, and the leaching time is 1-6 hours.

9. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: in the aluminum precipitation process, alkali is adopted to adjust the pH value of the precipitated liquid I to be increased to 4-7, and the reaction is carried out for 0.5-2 h at the temperature of room temperature-60 ℃.

10. The method for resource-soil treatment of red mud according to claim 1, wherein the method comprises the following steps: in the red mud dealkalization process, the iron-containing solution and the precipitated solution II are mixed with red mud according to the liquid-solid ratio of 2-10 mL:1g, and the mixture is reacted for 2-8 h at the temperature of 60-100 ℃.

Technical Field

The invention relates to a method for recycling and treating soil in red mud, in particular to a method for using waste liquid of red mud for treating soil in red mud by a metallurgy and environmental method on the basis of comprehensively recovering valuable elements such as aluminum, iron, titanium, scandium, silicon and the like in red mud, and mainly belongs to the field of red mud retreatment.

Background

Aluminum is a non-ferrous metal element with the largest yield and consumption, the yield of electrolytic aluminum in China in 2017 reaches 3630 ten thousand tons, which accounts for more than half of the total yield all over the world, and the yield of aluminum oxide exceeds 6000 ten thousand tons. The alumina production process in China mainly adopts a Bayer process, and in the process of dissolving alumina by the Bayer process, part of aluminum can be mixed with indissolvable iron, silicon, titanium and the like in bauxite and excessive alkali to be slagged together, namely the red mud. 0.5-2 t of red mud is produced per 1t of alumina produced, and the current global red mud accumulation amount exceeds 40 hundred million t, and continuously increases at a rate of 1.2 hundred million t per year. Due to high alkalinity, complex components and low nutrient content of the red mud, plants cannot grow, and long-term stacking not only occupies a large amount of land, but also easily causes pollution to the surrounding environment. In recent years, the national requirement on environmental protection is higher and higher, and the disposal of the red mud is more and more a key problem restricting the development of alumina enterprises. On the other hand, the red mud contains a large amount of iron, aluminum, silicon, calcium and a small amount of titanium, rare earth and the like, and if the red mud can be recycled, the economic benefit of alumina enterprises can be effectively improved.

The comprehensive disposal of the red mud generally has two forms of resource utilization and soil formation. The resource recycling method mainly comprises the steps of producing building materials, a desulfurizer, a water body adsorbent and the like by taking the red mud as a raw material, or directly extracting valuable metals in the red mud. Because the red mud yield is high, the accumulated stockpiling quantity is huge, and the single resource utilization consumption is low, the dealkalization treatment of the red mud to reduce the stockpiling risk of the red mud and even recover the soil structure for farming is the most effective way for the large-scale disposal of the red mud.

Chinese patent (publication No. CN102295396A) discloses a method for reprocessing and comprehensively utilizing red mud, wherein the red mud is used as a raw material, and a reduction roasting-strong magnetic separation method is adopted to obtain quartz sand and magnetite, the quartz sand and the magnetite with lower added values are produced by the method, and the reduction roasting and the strong magnetic separation are both processes with higher energy consumption and are poorer in economical efficiency. Chinese patent publication No. CN103898330A discloses a method for comprehensively recovering valuable metals such as iron, aluminum, scandium, titanium, vanadium, etc. from red mud, which recovers various valuable metals from red mud by a method of reduction roasting-ammonia leaching-acid leaching-extraction, and although this method can achieve a good comprehensive recovery effect, the flow is long, and the leaching of silicon during the ammonia leaching of aluminum affects the recovery of aluminum. Chinese patent (CN 107083485A) discloses a comprehensive utilization method of alumina red mud, which recovers iron, titanium and sodium in the red mud by using a vacuum reduction method, has higher production cost and lower added value of the obtained product, and is difficult to realize large-scale application.

In the field of red mud soil formation, a great deal of related work is also done by many researchers. Chinese patent (publication No. CN108977203A) discloses a red mud soil remediation agent and an application method thereof, the main components of the remediation agent comprise gypsum, fly ash, municipal dried sludge, waste biomass powder and the like, the remediation agent is used for ploughing and mixing the red mud, and the soil remediation of the red mud can be realized after watering and curing. Chinese patent (publication No. CN108273829A) discloses a method for reducing the alkalinity of Bayer process red mud, which comprises the steps of mixing straws with cow dung, adding water for fermentation to obtain a stacking material, and mixing the stacking material with the red mud to promote the soil formation of the red mud. Although the methods have simple material taking and low cost, the method has strong limitation on regions and has the problem of high transportation cost in long-distance operation.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a red mud recycling-soil chemical treatment method, which is used for dealkalizing red mud by utilizing the obtained iron/calcium-containing waste liquid on the basis of comprehensively recovering titanium, scandium, aluminum, silicon and other elements in the red mud to form a red mud recycling-soil chemical comprehensive treatment technology and can effectively solve the problem of red mud pollution.

In order to achieve the technical purpose, the invention provides a red mud resource-soil treatment method, which comprises the following steps:

1) leaching the red mud by concentrated acid to obtain leachate containing aluminum, iron, calcium, sodium, titanium and scandium and silicon-rich slag;

2) mixing and roasting the silicon-rich slag and alkaline salts to obtain a silicon fertilizer product;

3) extracting iron and back extracting iron from the leachate to obtain an iron-containing solution; obtaining the iron extraction raffinate containing aluminum, calcium, sodium, titanium and scandium;

4) adjusting the pH of the iron extraction raffinate to precipitate scandium and titanium by using an alkaline substance to obtain scandium-rich titanium slag and a precipitated liquid I; leaching the scandium-rich titanium slag by using dilute acid to obtain coarse titanium white and a scandium-containing solution;

5) the pH of the precipitated liquid I is further increased by adopting an alkaline substance to precipitate aluminum, so that aluminum-rich slag and a precipitated liquid II are obtained;

6) and the iron-containing solution and the precipitated solution II are used for dealkalizing the red mud to obtain a sodium-containing solution and dealkalized red mud.

According to the preferable scheme, concentrated hydrochloric acid is used as a leaching agent in the concentrated acid leaching process, the dosage of the concentrated hydrochloric acid is 0.8-1.6 times of the theoretical molar quantity of aluminum, iron, calcium, sodium, titanium and scandium contained in the dissolved red mud, the solid-to-solid ratio of a leaching solution is 2-10 mL/1g, the leaching temperature is 50-100 ℃, and the leaching time is 2-6 hours. The concentrated acid leaching process is preferably carried out by stirring the slurry.

In a preferred embodiment, the alkaline salt includes at least one of calcium oxide, calcium carbonate, calcium hydroxide, sodium hydroxide, and sodium carbonate.

In a more preferable scheme, the conditions in the roasting process are as follows: the mass ratio of the alkaline salts to the red mud is 0.2-2: 1, the roasting temperature is 300-1000 ℃, and the roasting time is 2-6 h. And mixing the silicon-rich slag and alkaline salts, roasting at high temperature, and washing the roasted product with excessive alkali to obtain a silicon fertilizer product.

In a preferable scheme, a quaternary ammonium type extracting agent is adopted in the process of extracting iron, the quaternary ammonium type extracting agent is a quaternary ammonium salt extracting agent containing long-chain alkyl, and common quaternary ammonium type extracting agents comprise at least one of hexadecyl trimethyl ammonium chloride, trioctyl methyl ammonium chloride, octaalkyl trimethyl ammonium chloride, dodecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride.

In a preferred embodiment, the extraction conditions are: compared with the volume ratio of O/W of 0.5-10: 1, the extraction temperature is 15-60 ℃, and the extraction time is 10-60 min. The preferred phase ratio O/W volume is 1-4: 1. The extraction temperature is preferably 20-40 ℃. In the extraction process, because the solubility of the quaternary ammonium type extracting agent in the diluent kerosene is low, a proper amount of polarity improving agent can be added during extraction, and the polarity improving agent is mainly liquid water-insoluble alcohols or phenols, such as amyl alcohol, isodecyl alcohol, diethyl hexanol, sec-octyl alcohol, n-octyl alcohol, isooctyl alcohol, nonyl phenol, cyclohexanol and the like.

In a more preferable scheme, the organic phase containing the quaternary ammonium type extracting agent in the extraction process comprises the following components in percentage by volume: 5-50% of quaternary ammonium type extracting agent; 1-40% of liquid water-insoluble alcohol and/or phenol polarity improver; 10 to 94 percent of kerosene. The volume ratio of the quaternary ammonium type extracting agent in the organic phase is preferably 10-30%. The volume ratio of the liquid water-insoluble alcohol and/or phenol polarity improver in the organic phase is preferably 5-20%.

In the preferable scheme, water or dilute acid solution is adopted as a stripping agent in the iron stripping process, and the stripping conditions are as follows: compared with the volume ratio of O/A of 0.5-2: 1, the back extraction temperature is room temperature-40 ℃, and the back extraction time is 2-20 min. The organic phase after the back extraction of iron is returned to the iron extraction stage. The stripping agent may be water, and in order to avoid hydrolysis of fe (iii), a small amount of acid may be added to the water to adjust the pH to below 2, and therefore, a more preferred stripping agent is a dilute acid solution, and a more preferred acid is dilute hydrochloric acid.

In the preferable scheme, in the process of precipitating scandium and titanium, the pH value of the iron extraction raffinate is adjusted to 0.5-2 by adopting alkali, and the reaction is carried out for 0.5-6 h at the temperature of room temperature-50 ℃. The alkali is cheap and easily available alkali such as calcium oxide, calcium hydroxide or calcium carbonate. During the reaction, the solution is preferably stirred to improve the precipitation efficiency.

In the preferable scheme, at least one of sulfuric acid, hydrochloric acid and nitric acid is used as a leaching agent in the dilute acid leaching process, the concentration of hydrogen ions in a leaching system is 0.5-2 mol/L, the liquid-solid ratio is 2-10 mL:1g, the leaching temperature is 60-100 ℃, and the leaching time is 1-6 h. The preferable liquid-solid ratio is 2-6 mL:1 g. The solution is preferably stirred during the acid leaching process to improve the leaching efficiency.

In the preferred scheme, in the aluminum precipitation process, alkali is adopted to adjust the pH value of the precipitated liquid I to be increased to 4-7, and the reaction is carried out for 0.5-2 h at the temperature of room temperature-60 ℃. The alkali is cheap and easily available alkali such as calcium oxide, calcium hydroxide or calcium carbonate. During the reaction, the solution is preferably stirred to improve the precipitation efficiency.

In the preferable scheme, in the red mud dealkalization process, the iron-containing solution and the precipitated solution II are mixed with red mud according to the liquid-solid ratio of 2-10 mL:1g, and react for 2-8 h at the temperature of 60-100 ℃. The iron-containing solution and the precipitated liquid II can be mixed according to any volume ratio, and the volume ratio of the iron-containing solution to the precipitated liquid II is preferably less than or equal to 10: 1. in the dealkalization process, a reaction system needs to be stirred or the red mud is fixed on a fixed reaction bed and leached by dealkalized solution.

In the preferred scheme, scandium oxide can be prepared from the scandium-containing solution by a conventional extraction, enrichment and back-extraction process in the prior art.

In the preferable scheme, the aluminum-rich slag is returned to the Bayer process for aluminum oxide production.

In a preferred scheme, the red mud is high-alkali waste residue obtained in the production process of bauxite, and comprises Bayer process red mud, sintering process red mud and combination process red mud.

The key point of the technical scheme is that red mud recycling and soil chemical treatment are combined, valuable metals such as scandium, titanium, aluminum and the like in the red mud are recycled in a segmented mode by an acid leaching-extraction-neutralization method, meanwhile, leaching residues are treated to obtain silicon fertilizer, waste liquid is used for red mud dealkalization, the red mud recycling-soil chemical treatment technology is realized, and the environmental problem caused by the red mud is effectively solved.

Compared with the prior art, the technical scheme of the invention has the following advantages:

1. through hydrochloric acid leaching treatment of red mud, and through extraction, precipitation and other related technologies, valuable metal elements such as aluminum, titanium, scandium and the like in the red mud can be effectively recovered, the comprehensive recovery rate of aluminum can reach more than 85%, and the comprehensive recovery rate of scandium and titanium can reach more than 70%;

2. the silicon-rich slag obtained by leaching is subjected to alkali roasting treatment, so that the content of active silicon in the silicon slag can be effectively improved, the concentration of heavy metal is reduced, a silicon fertilizer product reaching the standard can be directly obtained after roasting, and no solid waste is generated in the process;

3. the intermediate material generated in the process is used for dealkalizing the red mud to obtain dealkalized red mud and sodium chloride solution, so that the high-salt solution generated in the resource process can be effectively treated, and the problem of high cost of the red mud dealkalizing agent can be solved.

4. The method has the advantages of simple process, low equipment investment, environmental protection and capability of meeting the industrial production requirement.

Drawings

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

Detailed Description

The following examples are intended to further illustrate the present invention and are not intended to limit the scope of the claims.