CN107324303B - Method for separating refined iron and chromium from multi-metal hazardous waste - Google Patents

Method for separating refined iron and chromium from multi-metal hazardous waste Download PDF

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CN107324303B
CN107324303B CN201710786889.4A CN201710786889A CN107324303B CN 107324303 B CN107324303 B CN 107324303B CN 201710786889 A CN201710786889 A CN 201710786889A CN 107324303 B CN107324303 B CN 107324303B
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iron
filtrate
chromium
crude
filter pressing
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CN107324303A (en
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王修海
贾智慧
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QINGCHUAN TENWIN METALS DEVELOPMENT Co Ltd
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QINGCHUAN TENWIN METALS DEVELOPMENT Co Ltd
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00Phosphorus; Compounds thereof
    • C01B25/16Oxyacids of phosphorus; Salts thereof
    • C01B25/26Phosphates
    • C01B25/37Phosphates of heavy metals
    • C01B25/375Phosphates of heavy metals of iron
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00Compounds of calcium, strontium, or barium
    • C01F11/46Sulfates
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01GCOMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G37/00Compounds of chromium
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01GCOMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00Compounds of iron
    • C01G49/02Oxides; Hydroxides

Abstract

The invention discloses a method for separating and refining iron and chromium from multi-metal hazardous waste, which selectively precipitates Fe by using phosphate radical carried by sludge3+Preparation of iron phosphate while reacting it with Cr3+Separating; cr is also precipitated due to phosphate radicals3+In the process, Fe is adopted3+Excessive methods prevent the formation of chromium phosphate precipitates; the remainder of Fe3+Reducing iron filings into Fe2+Then using alkali to regulate a certain pH value to selectively precipitate Cr3+Preparing chromium hydroxide to further separate iron and chromium. The method does not need heating in the whole process, comprehensively utilizes iron ions and phosphate radicals in hazardous waste, and has low cost; meanwhile, no waste water or waste residue is generated, and the method is environment-friendly; the iron phosphate products extracted respectively have high economic value, can be used as raw materials of battery materials, ceramics and the like, and the chromium hydroxide can be used as raw materials of industries such as pigments, chemical engineering and the like.

Description

Method for separating refined iron and chromium from multi-metal hazardous waste
Technical Field
The invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for separating and refining iron and chromium from multi-metal hazardous waste.
Background
At present, the hazardous waste containing multiple metals in China is sludge or wastewater generated in the industries of electroplating, surface treatment, smelting, chemical engineering and the like, wherein the hazardous waste contains multiple metals including iron, chromium, copper, zinc, nickel, cobalt, manganese and the like. Chromium is a heavy metal with strong toxicity, easily enters human cells, damages internal organs such as liver and kidney and DNA, has an accumulation effect in human bodies, and has carcinogenicity and the risk of possibly inducing gene mutation. The discharge of the chromium-containing sludge or wastewater into the environment not only easily causes environmental water pollution, but also directly threatens the human life health. Therefore, it is important to realize harmless treatment of chromium-containing waste. The technologies for harmless treatment of chromium-containing wastes can be generally classified into two types: the first is solidification and stabilization technology, and the second is recycling technology. The solidification and stabilization are realized by solidifying chromium-containing waste in a solidified body by using a curing agent so as to avoid the loss of heavy metal chromium to the environment, and the method is slightly insufficient in the aspect of recycling valuable metals. The regeneration and utilization is characterized in that a certain leaching agent is used for leaching out main target metal, and then methods such as extraction, precipitation, electrolysis and the like are adopted for extracting metal products for utilization, so that the cyclic regeneration of metal resources is realized.
The chemical properties of metallic iron and chromium are very similar, and the separation of the two has been a difficult problem in the research field. The existing iron-chromium separation method mainly comprises an electrolytic method, an extraction method and a precipitation method. Chromium sulfate and ferric sulfate in sludge acid leaching filtrate are converted into chromium ammonium alum and iron ammonium alum by an electrolytic method in a certain factory, and then the purpose of separating chromium and iron is achieved according to the difference of the solubility of the chromium sulfate and the ferric sulfate at 75 ℃. Wanpeng et al used an extraction method to separate iron and chromium by using P204 and P507 as the extractant. After the waste ferrochrome alloy is leached by sulfuric acid, such as Wu Jian Hui, etc., the iron in the solution is separated by Mohr's salt crystallization method, which needs to react for 6h under the condition of 70 ℃, and then quickly cooled and crystallized for 24 h. Mixing Fe with hydrogen peroxide2+Oxidation to Fe3+Then, alkali is used for precipitation and iron removal, so that iron and chromium separation is realized. There are also patents which use oxalic acid with Fe2+And (4) separating iron and chromium by complexing precipitation. The electrolysis method has high energy consumption and complex equipment, and increases the disposal cost of hazardous waste. The extraction method introduces recyclable organic solvent, but has limited service life and increases new pollutants. The precipitation method utilizes different solubility products of compounds formed by different types and valence metals and different precipitants to separate metals through selective precipitation, has low energy consumption and simple equipment, but needs to select an ideal precipitator and control proper conditions, on one hand, reduces the medicament cost in the treatment process and improves the iron-chromium separation rate, and on the other hand, improves the utilization value of iron and chromium secondary metal resources.
Based on the analysis, the method for separating and refining iron and chromium from the multi-metal hazardous waste, which does not need heating in the whole process, comprehensively utilizes iron ions and phosphate radicals in the hazardous waste, does not generate waste water and waste residues, is environment-friendly, and can carry out secondary utilization on the extracted iron phosphate and chromium hydroxide, is urgently needed in the industry at present.
Disclosure of Invention
In view of the defects, the method for separating and refining iron and chromium from the multi-metal hazardous waste provided by the invention does not need heating in the whole process, utilizes iron ions and phosphate radicals in the hazardous waste to the maximum extent, does not generate waste water and waste residues in the preparation process, and is environment-friendly.
In order to achieve the purpose, the invention adopts the following technical scheme that the refined iron and the refined chromium separated in the concentration and pH value ranges of all substances used by the invention can be used for secondary use in chemical industry.
A method for separating and refining iron and chromium from multi-metal hazardous waste comprises the following steps:
(1) acid leaching: preparing the comprehensive sludge containing metal elements, adding water into the sludge for pulping, and slowly adding 98 percent of H while stirring2SO4When the pH value is regulated to be stable at 0.5, stopping adding acid, and continuously dissolving to ensure that all metal elements in the sludge enter the solution;
(2) and (3) filter pressing: carrying out filter pressing on the solution after acid leaching, washing filter residues after filter pressing, returning washing water to be used as slurry mixing water, purifying the washed residues, and carrying out continuous treatment on filter pressing filtrate in the next procedure;
(3) crude iron chromite alum: the collected filtrate is put into a container to be stirred, and CaCO is slowly added under normal pressure3Adjusting the pH value of the slurry to 4.0, continuing the reaction, and slowly adding H2O2With simultaneous use of CaCO3The slurry was controlled to pH3.8 ~ 4.1.1 until H2O2Mixing Fe2+Is completely oxidized into Fe3+Then, performing filter pressing to obtain a filter cake which is crude ferrochromium alum, and separating the filtrate into copper, zinc, nickel, cobalt and manganese;
(4) dissolving the crude iron chromite: pulping the crude iron chromite filter cake with water, adding 98% H2SO4Adjusting the pH value to 0.5 to enable iron and chromium to enter the solution, then performing filter pressing, wherein a filter cake is crude gypsum (calcium sulfate dihydrate as a main component), purifying and washing to obtain a gypsum product, and enabling a filtrate to enter the next working procedure;
(5) reduction: adding iron filings and 98% H into the filtrate2SO4Maintaining the pH at 1.0 ~ 1.5.5, adding Fe3+Reduction to Fe2 +Filtering after the reduction is finished;
(6) and (3) chromium deposition: 10% CaCO was added to the filtrate3The slurry is adjusted to pH 5.5 to precipitate Cr3+The filter cake after filter pressing is Cr (OH)3
(7) And (3) iron precipitation: will contain Fe2+The filtrate is returned to the crude iron-chromium alum process, and the iron content is supplemented to the filtrate or directly added with alkali liquor for precipitation, and the filtrate is oxidized in the air to obtain Fe (OH)3
The method for separating and refining iron and chromium from polymetallic hazardous waste by artificially adding phosphate radicals is also provided, and specifically comprises the following steps:
a method for separating refined iron and chromium from multi-metal hazardous waste comprises the following steps:
(1) acid leaching: preparing the comprehensive sludge containing metal elements, adding water into the sludge for pulping, and slowly adding 98 percent of H while stirring2SO4When the pH value is regulated to be stable at 0.5, stopping adding acid, and continuously dissolving to ensure that all metal elements in the sludge enter the solution;
(2) and (3) filter pressing: carrying out filter pressing on the solution after acid leaching, washing filter residues after filter pressing, returning washing water to be used as slurry mixing water, purifying the washed residues, and carrying out continuous treatment on filter pressing filtrate in the next procedure;
(3) crude iron chromite alum: the collected filtrate is put into a container to be stirred, and CaCO is slowly added under normal pressure3Adjusting the pH value of the slurry to 4.0, continuing the reaction, and slowly adding H2O2With simultaneous use of CaCO3The slurry was controlled to pH3.8 ~ 4.1.1 until H2O2Mixing Fe2+Is completely oxidized into Fe3+Then, performing filter pressing to obtain a filter cake which is crude ferrochromium alum, and separating the filtrate into copper, zinc, nickel, cobalt and manganese;
(4) dissolving the crude iron chromite: pulping the crude iron-chromium alum filter cake with water, adding 98% H2SO4 to adjust the pH value to 0.5 to make iron and chromium enter the solution, then performing pressure filtration, wherein the filter cake is crude gypsum, purifying and washing to obtain a gypsum product, and feeding the filtrate to the next working procedure;
(5) adding phosphate radical to prepare iron phosphate: adding 85% phosphoric acid into the filtrate to make the filtrate Fe3+The concentration of the phosphate is 2 ~ 3g/L higher than that of the phosphate, and the filtrate is slowly mixed with stirring at room temperature and 300r/minThe pH was adjusted to 1.5 by slow addition of 10% sodium hydroxide solution, initially with light yellow FePO4Precipitate is generated, the pH value reaches 2.0 and is stirred for 1 hour after being stabilized, and light yellow FePO is obtained4Precipitating, carrying out filter pressing and washing, wherein a filter cake is finished iron phosphate, and the filtrate enters the next working procedure;
(6) reduction: adding iron filings and 98% H into the filtrate2SO4Maintaining the pH at 1.0 ~ 1.5.5, adding Fe3+Reduction to Fe2 +Filtering after the reduction is finished;
(7) and (3) chromium deposition: 10% CaCO was added to the filtrate3The pH of the slurry is adjusted to 5.5 to precipitate Cr3+The filter cake after filter pressing is Cr (OH)3
(8) And (3) iron precipitation: will contain Fe2+The filtrate is returned to the crude iron-chromium alum process, and the iron content is supplemented to the filtrate or directly added with alkali liquor for precipitation, and the filtrate is oxidized in the air to obtain Fe (OH)3
The invention also provides a method for separating and refining iron and chromium from multi-metal hazardous waste containing phosphate radicals, which comprises the following steps:
a method for separating and refining iron and chromium from multi-metal hazardous waste comprises the following steps:
(1) acid leaching: preparing comprehensive sludge containing phosphate radicals and metal elements, adding water into the sludge for pulping, and slowly adding 98% of H while stirring2SO4When the pH value is regulated to be stable at 0.5, stopping adding acid, and continuously dissolving to ensure that all metal elements in the sludge enter the solution;
(2) and (3) filter pressing: carrying out filter pressing on the solution after acid leaching, washing filter residues after filter pressing, returning washing water to be used as slurry mixing water, purifying the washed residues, and carrying out continuous treatment on filter pressing filtrate in the next procedure;
(3) crude iron chromite alum: the collected filtrate is put into a container to be stirred, and CaCO is slowly added under normal pressure3Adjusting the pH value of the slurry to 4.0, continuing the reaction, and slowly adding H2O2With simultaneous use of CaCO3The slurry was controlled to pH3.8 ~ 4.1.1 until H2O2Mixing Fe2+Is completely oxidized into Fe3+Then press-filteredThe obtained filter cake is rough iron-chromium alum, and the filtrate enters the working procedure of separating copper, zinc, nickel, cobalt and manganese;
(4) preparing iron phosphate: pulping the crude iron chromite filter cake with water, adding 98% H2SO4Adjusting pH to 0.5 to make iron and chromium enter the solution, press-filtering, and supplementing Fe into the filtrate3+To make the filtrate contain Fe3+The concentration of the phosphate radical is 2 ~ 3g/L higher than that of the phosphate radical, 10 percent sodium hydroxide solution is slowly added to adjust the pH value to 2.0, and light yellow FePO is obtained4Precipitating, carrying out filter pressing and washing, wherein a filter cake is finished iron phosphate, and the filtrate enters the next working procedure;
(5) reduction: adding iron filings and 98% H into the filtrate2SO4Maintaining the pH at 1.0 ~ 1.5.5, adding Fe3+Reduction to Fe2 +Filtering after the reduction is finished;
(6) and (3) chromium deposition: 10% CaCO was added to the filtrate3The pH of the slurry is adjusted to 5.5 to precipitate Cr3+The filter cake after filter pressing is Cr (OH)3
(7) And (3) iron precipitation: will contain Fe2+The filtrate is returned to the crude iron-chromium alum process, and the iron content is supplemented to the filtrate or directly added with alkali liquor for precipitation, and the filtrate is oxidized in the air to obtain Fe (OH)3
Further, the metal elements include, but are not limited to, iron, chromium, copper, zinc, nickel, cobalt, manganese.
Further, in the comprehensive sludge batching in the step (1), the molar ratio of total iron to total chromium is 2.5 ~ 3.5.5: 1, and the sludge and the water are pulped in a mass ratio of 1:1 ~ 5.
Further, the pulping in the step (4) is to prepare the crude iron-chromium alum filter cake and water in a ratio of 1:1 ~ 3.
Compared with the prior art, the invention has the following advantages:
(1) the whole process of the invention does not need heating, thereby saving the processing time and reducing the processing cost;
(2) no waste water and waste residue are generated, and the method is environment-friendly;
(3) the extracted product iron phosphate has high economic value, can be used as a raw material of battery materials, ceramics and the like, and the chromium hydroxide can be used as a raw material in industries such as pigments, chemical engineering and the like;
(4) the invention provides three methods for separating and refining iron and chromium from multi-metal hazardous wastes aiming at different conditions (no phosphate radical exists, phosphate radical exists and phosphate radical is artificially added), thereby enlarging the application range;
(5) cr in aqueous solution3+The pH of the complete precipitate was 6.8 in the presence of Fe3+When present, Fe3+And Cr3+Forming double-salt precipitation iron-chromium alum under the condition of pH 3.8-4.1, so that the pH value of chromium precipitation is greatly reduced, and finally, the chromium element is well separated from elements such as copper, zinc, nickel, cobalt, manganese and the like;
(6) supplementing excessive iron element into iron-making chrome alum solution, utilizing solubility product principle and controlling a certain pH value to make limited phosphate radical only be mixed with Fe3+Form precipitate without reacting with Cr3+And other impurity elements such as zinc, nickel, copper and the like form precipitates so as to utilize excessive Fe in the process of preparing the iron phosphate3+Inhibiting phosphate radical and Cr3+Precipitate is formed to realize the primary separation of iron and chromium and prepare iron phosphate products with higher purity;
(7) reduction of Fe with metallic iron3+Without introducing other impurity elements, Fe3+Complete reduction to Fe2+Then, by controlling appropriate conditions, Fe is used2+And Cr3+The pH difference of the precipitate can better separate chromium and iron, the precipitant calcium carbonate has weak alkalinity, the pH value of the slurry is 5.4 ~ 6.0.0, the condition of overhigh local alkalinity of the solution can not be generated, and the chromium and iron can be separated;
(8) the excess calcium carbonate can also act as a filter aid to improve filtration performance, which is ultimately recovered as a calcium sulfate by-product.
Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.
Drawings
FIG. 1 is a process flow diagram of example 3.
FIG. 2 is a graph showing the relationship between the ratio of the contents of iron and chromium and the amount of phosphate in example 2.
FIG. 3 is the relationship between the precipitation rate of Fe and Cr and the pH value in example 2.
Detailed Description
The invention will be further elucidated with reference to specific embodiments.
Example 1
Method for separating and refining iron and chromium from polymetallic hazardous wastes (sludge without phosphate radical)
(1) Analysis of raw materials
Taking the comprehensive sludge without phosphate radical, supplementing Fe salt into the sludge, uniformly mixing until the Fe: Cr =2.5 ~ 3.5.5: 1, and analyzing the metal content by using a flame atomic absorption spectrophotometer, wherein the result is shown in table 1.
TABLE 1 comprehensive sludge Metal component content
(2) Acid leaching experiment
And (2) putting 500g of the uniformly mixed comprehensive sludge into a 2000mL beaker, adding 1200mL of water, mechanically stirring and putting the uniformly mixed comprehensive sludge into the beaker, adjusting the rotating speed to be 300r/min to enable the sludge to be slurried, then slowly adding 98% sulfuric acid into the slurry, gradually dissolving the sludge in the process, adding the sulfuric acid until the sludge does not react, continuously stirring for 30min, and stabilizing the pH value to be about 0.5 to enable the metals in the sludge to be completely leached. After the leaching reaction was qualified, the filtrate was filtered to obtain 1360mL of the filtrate, and the metal concentration was analyzed by a flame atomic absorption spectrophotometer, and the results are shown in Table 2.
TABLE 2 table of concentrations of metal elements in acid leach filtrates
In the process, 116.45 g of 98 percent sulfuric acid is consumed totally, and the acid consumption is 23.29 percent.
(3) Crude iron chromium alum
And (3) adjusting the pH value of the filtrate after acid leaching to be 4.0 by using 10% calcium carbonate slurry, slowly adding 30% hydrogen peroxide while controlling the pH value to be 3.8 ~ 4.1.1 by using the calcium carbonate slurry until the ferrous ions are completely oxidized into ferric ions by the hydrogen peroxide, then carrying out pressure filtration and washing the filter cake to be neutral, wherein the obtained filter cake is crude ferrochromanite and accounts for 401.02 g.
(4) Dissolving crude iron chrome alum
Placing the prepared crude iron chromite into a 2000mL beaker, adding 600mL of water, placing the beaker with mechanical stirring, adjusting the rotating speed to 300r/min to enable sludge to be slurried, then slowly adding 98% sulfuric acid into the slurry until the iron chromite is completely dissolved, continuing stirring for 30min, and stabilizing the pH value to about 0.5 to enable the iron and the chromium to be completely leached. The filtrate was then filtered to give 823mL, and the metal concentration in the filtrate was measured by flame atomic absorption spectrophotometer, the results of which are shown in Table 3.
TABLE 3 composition Table of iron and chromium-containing filtrates
(5) Reduction-chromium deposition
Adding iron filings into the filtrate, adding 98% sulfuric acid to keep the pH value at 1.0 ~ 1.5.5, reducing ferric ions into ferrous ions, filtering after reduction, measuring the concentrations of iron and chromium in the filtrate to be 16.87g/L and 4.49g/L respectively by atomic absorption, adding 10% calcium carbonate slurry into the filtrate to adjust the pH value to be 5.5, stirring for 30min after stabilization, filtering to obtain 825mL filtrate, measuring the concentrations of the residual iron and chromium in the filtrate to be 15.94g/L and 0.03g/L respectively, obtaining 51.53g of filter cake, drying the filter cake to constant weight at 105 ℃ to obtain chromium products, and measuring the mass percentages of the chromium and the iron in the chromium products to be 12.74% and 2.85% respectively.
(6) Heavy iron
Adding 10% sodium carbonate solution into the filtrate of the previous step, adjusting pH to 10.0, stabilizing for 30min, filtering, and drying the filter cake at 105 deg.C to constant weight to obtain iron product, wherein the measured mass percentages of iron and chromium in the iron product are 29.85% and 0.05%, respectively.
Example 2
Method for separating and refining iron and chromium from polymetallic hazardous waste (adding phosphate to sludge without phosphate to separate iron and chromium)
(1) Preparation of iron and chromium containing filtrate
500g of the sludge prepared in example 1 was taken, 1000mL of the sludge was added to prepare a slurry, the operations of acid leaching, crude ferrochromium and crude ferrochromium dissolution were performed by the method in example 1 to obtain 816mL of the filtrate finally, and the concentration of the metal in the filtrate was measured by flame atomic absorption spectrophotometry, and the results are shown in Table 4.
TABLE 4 composition Table of iron and chromium-containing filtrates
(2) Preparation of iron phosphate by adding phosphate radical
Taking 5 parts of 150mL of the iron and chromium-containing filtrate (Fe)3+:11.05g/L,Cr3+4.48g/L, the concentration ratio of iron to chromium is 2.47), respectively placing the mixture into a 500mL beaker, respectively adding 1.24, 1.41, 1.59, 1.76, 1.94 and 2.12g of 85% phosphoric acid into the beaker, respectively, stirring the mixture at room temperature and 300r/min, slowly adding 10% sodium hydroxide solution into the filtrate to adjust the pH value, wherein about 1.5 of the pH value, light yellow ferric phosphate precipitation begins to generate, after the pH value reaches 2.0 and is continuously stirred for 1h, respectively, performing filter pressing and washing to be neutral, respectively, drying the obtained ferric phosphate to constant weight at 60 ℃, measuring the metal components in the ferric phosphate by flame atomic absorption spectrophotometry, wherein the relationship between the iron content ratio and chromium content ratio of the ferric phosphate in the product and the ferric phosphate content ratio and the chromium content in the product is 352, when the concentration ratio of the phosphate in the product is less than 9g/L, the concentration ratio of the ferric phosphate in the product is increased gradually, and the concentration ratio of the ferric phosphate in the product is 352, and the product is increased, when the concentration ratio of the concentration of the ferric phosphate in the product is considered, the process, the product is increased gradually, the concentration ratio of the product is 352.
(3) Reduction-chromium deposition
Combining the filtrates of the previous step to obtain a total of 800mL, measuring the concentrations of iron and chromium therein as 1.05g/L and 3.98g/L, respectively, adding iron filings to the filtrates, adding 98% sulfuric acid to maintain the pH value at 1.0 ~.5, reducing ferric ions to ferrous ions, filtering after reduction, measuring the concentrations of iron and chromium in the filtrates as 1.58g/L and 3.98g/L by atomic absorption, dividing the filtrates into 5 parts, each 150mL, adding 10% calcium carbonate slurry to the filtrates to adjust the pH values to 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, respectively, continuing stirring for 30min after stabilization, then filtering, measuring the concentrations of the remaining chromium and iron in the filtrates, measuring the precipitation rates of chromium and iron under different pH values, see FIG. 3. it can be seen from FIG. 3 that at pH value of 5.5 ~.0, substantially complete precipitation of chromium can be achieved, at this time, the precipitation rate of iron is at 10% below pH value, thus the iron ions are easily separated by oxidation, and the iron precipitation rate is high as ~.5.
Example 3
A method for separating refined iron and chromium from polymetallic hazardous waste (sludge process flow containing phosphate radical is shown in figure 1)
(1) Analysis of raw materials
Taking comprehensive sludge containing phosphate radicals and supplementing Fe into the sludge3+Mixing the salt to ensure that the ratio of Fe: cr (chromium) component-=2.5 ~ 3.5.5: 1, the metal content was analyzed by flame atomic absorption spectrophotometer, and the phosphate content was analyzed by visible spectrophotometer, the results are shown in table 5.
TABLE 5 comprehensive metal component table of phosphate radical-containing sludge
(2) Experiment of
500g of the above-mentioned mixed integrated sludge was taken out and put into a 2000mL beaker, 1000mL of water was added, and the acid leaching, crude ferrochromium alum, and crude ferrochromium alum dissolution steps were carried out by the method in example 1. Finally, 1045mL of filtrate mainly containing iron, chromium and phosphate radicals is obtained, and the concentrations are respectively as follows: 12.23g/L, 4.59g/L and 12.78 g/L.
And supplementing a ferric iron solution into the filtrate to enable the concentration of ferric iron in the solution to be 2.5g/L more than that of phosphate radical, then adding a 10% sodium hydroxide solution into the solution to adjust the pH value to be 2.0, and under the condition, precipitating iron and phosphate radical in the form of ferric phosphate, wherein the concentration of ferric iron in the system is more than that of phosphate radical, so that chromium can be effectively prevented from being entrained by the phosphate radical and precipitated. After the pH value is stabilized for 1h, filtering, and enabling the filtrate to enter the next working procedure; the filter cake is an iron phosphate product and is dried to constant weight at 60 ℃, and the component analysis is shown in table 6.
TABLE 6 iron phosphate composition analysis Table
Adding iron filings into the filtrate obtained in the previous process, adding 98% sulfuric acid to keep the pH value at 1.0 ~ 1.5.5, completely reducing ferric ions into ferrous ions, filtering, measuring the concentrations of iron and chromium in the filtrate to be 3.087 g/L and 5.850 g/L respectively (the chromium-iron ratio is 1.90), adding 10% calcium carbonate slurry into the filtrate to adjust the pH value to be 5.5, continuing stirring for 30min after stabilization, filtering and washing a filter cake to be neutral, wherein the filter cake is a chromium hydroxide product obtained by primary purification, and measuring the chromium-iron ratio in the filter cake to be 33.05.
And (3) continuously dissolving the filter cake by using sulfuric acid, adding iron scraps, reducing, precipitating again, carrying out secondary purification, drying the chromium hydroxide product obtained by the secondary purification at 105 ℃ to constant weight, and measuring that the grade of chromium is 25.67%, the iron content is 0.165%, and the chromium-iron ratio is 155.30.

Claims (6)

1. A method for separating refined iron and chromium from multi-metal hazardous waste, which is characterized by comprising the following steps:
(1) acid leaching: preparing the comprehensive sludge containing metal elements, adding water into the sludge for pulping, and slowly adding 98 percent of H while stirring2SO4When the pH value is regulated to be stable at 0.5, stopping adding acid, and continuously dissolving to ensure that all metal elements in the sludge enter the solution;
(2) and (3) filter pressing: carrying out filter pressing on the solution after acid leaching, washing filter residues after filter pressing, returning washing water to be used as slurry mixing water, purifying the washed residues, and carrying out continuous treatment on filter pressing filtrate in the next procedure;
(3) crude iron chromite alum: putting the collected filtrate into a containerStirring in a container, slowly adding CaCO at normal pressure3Adjusting the pH value of the slurry to 4.0, continuing the reaction, and slowly adding H2O2With simultaneous use of CaCO3The slurry was controlled to pH3.8 ~ 4.1.1 until H2O2Mixing Fe2+Is completely oxidized into Fe3+Then, performing filter pressing to obtain a filter cake which is crude ferrochromium alum, and separating the filtrate into copper, zinc, nickel, cobalt and manganese;
(4) dissolving the crude iron chromite: pulping the crude iron chromite filter cake with water, adding 98% H2SO4Adjusting the pH value to 0.5 to enable iron and chromium to enter the solution, then performing filter pressing, wherein a filter cake is crude gypsum, purifying and washing to obtain a gypsum product, and enabling a filtrate to enter the next working procedure;
(5) reduction: adding iron filings and 98% H into the filtrate2SO4Maintaining the pH at 1.0 ~ 1.5.5, adding Fe3+Reduction to Fe2+Filtering after the reduction is finished;
(6) and (3) chromium deposition: 10% CaCO was added to the filtrate3The pH of the slurry is adjusted to 5.5 to precipitate Cr3+The filter cake after filter pressing is Cr (OH)3
(7) And (3) iron precipitation: will contain Fe2+The filtrate is returned to the crude iron-chromium alum process, and the iron content is supplemented to the filtrate or directly added with alkali liquor for precipitation, and the filtrate is oxidized in the air to obtain Fe (OH)3
2. A method for separating refined iron and chromium from multi-metal hazardous waste, which is characterized by comprising the following steps:
(1) acid leaching: preparing the comprehensive sludge containing metal elements, adding water into the sludge for pulping, and slowly adding 98 percent of H while stirring2SO4When the pH value is regulated to be stable at 0.5, stopping adding acid, and continuously dissolving to ensure that all metal elements in the sludge enter the solution;
(2) and (3) filter pressing: carrying out filter pressing on the solution after acid leaching, washing filter residues after filter pressing, returning washing water to be used as slurry mixing water, purifying the washed residues, and carrying out continuous treatment on filter pressing filtrate in the next procedure;
(3) crude preparationIron chromium alum: the collected filtrate is put into a container to be stirred, and CaCO is slowly added under normal pressure3Adjusting the pH value of the slurry to 4.0, continuing the reaction, and slowly adding H2O2With simultaneous use of CaCO3The slurry was controlled to pH3.8 ~ 4.1.1 until H2O2Mixing Fe2+Is completely oxidized into Fe3+Then, performing filter pressing to obtain a filter cake which is crude ferrochromium alum, and separating the filtrate into copper, zinc, nickel, cobalt and manganese;
(4) dissolving the crude iron chromite: pulping the crude iron chromite filter cake with water, adding 98% H2SO4Adjusting the pH value to 0.5 to enable iron and chromium to enter the solution, then performing filter pressing, wherein a filter cake is crude gypsum, purifying and washing to obtain a gypsum product, and enabling a filtrate to enter the next working procedure;
(5) adding phosphate radical to prepare iron phosphate: adding 85% phosphoric acid into the filtrate to make the filtrate Fe3+The concentration of the sodium hydroxide is 2 ~ 3g/L higher than that of the phosphate, 10 percent sodium hydroxide solution is slowly added into the filtrate to adjust the pH value to 1.5 under the stirring of 300r/min at room temperature, and light yellow FePO begins to exist4Precipitate is generated, the pH value reaches 2.0 and is stirred for 1 hour after being stabilized, and light yellow FePO is obtained4Precipitating, carrying out filter pressing and washing, wherein a filter cake is finished iron phosphate, and the filtrate enters the next working procedure;
(6) reduction: adding iron filings and 98% H into the filtrate2SO4Maintaining the pH at 1.0 ~ 1.5.5, adding Fe3+Reduction to Fe2+Filtering after the reduction is finished;
(7) and (3) chromium deposition: 10% CaCO was added to the filtrate3The pH of the slurry is adjusted to 5.5 to precipitate Cr3+The filter cake after filter pressing is Cr (OH)3
(8) And (3) iron precipitation: will contain Fe2+The filtrate is returned to the crude iron-chromium alum process, and the iron content is supplemented to the filtrate or directly added with alkali liquor for precipitation, and the filtrate is oxidized in the air to obtain Fe (OH)3
3. A method for separating refined iron and chromium from multi-metal hazardous waste, which is characterized by comprising the following steps:
(1) acid leaching: will containPreparing comprehensive sludge of phosphate radicals and metal elements, adding water into the sludge for pulping, and slowly adding 98% of H while stirring2SO4When the pH value is regulated to be stable at 0.5, stopping adding acid, and continuously dissolving to ensure that all metal elements in the sludge enter the solution;
(2) and (3) filter pressing: carrying out filter pressing on the solution after acid leaching, washing filter residues after filter pressing, returning washing water to be used as slurry mixing water, purifying the washed residues, and carrying out continuous treatment on filter pressing filtrate in the next procedure;
(3) crude iron chromite alum: the collected filtrate is put into a container to be stirred, and CaCO is slowly added under normal pressure3Adjusting the pH value of the slurry to 4.0, continuing the reaction, and slowly adding H2O2With simultaneous use of CaCO3The slurry was controlled to pH3.8 ~ 4.1.1 until H2O2Mixing Fe2+Is completely oxidized into Fe3+Then, performing filter pressing to obtain a filter cake which is crude ferrochromium alum, and separating the filtrate into copper, zinc, nickel, cobalt and manganese;
(4) preparing iron phosphate: pulping the crude iron chromite filter cake with water, adding 98% H2SO4Adjusting pH to 0.5 to make iron and chromium enter the solution, press-filtering, and supplementing Fe into the filtrate3+To make the filtrate contain Fe3+The concentration of the phosphate radical is 2 ~ 3g/L higher than that of the phosphate radical, 10 percent sodium hydroxide solution is slowly added to adjust the pH value to 2.0, and light yellow FePO is obtained4Precipitating, carrying out filter pressing and washing, wherein a filter cake is finished iron phosphate, and the filtrate enters the next working procedure;
(5) reduction: adding iron filings and 98% H into the filtrate2SO4Maintaining the pH at 1.0 ~ 1.5.5, adding Fe3+Reduction to Fe2+Filtering after the reduction is finished;
(6) and (3) chromium deposition: 10% CaCO was added to the filtrate3The pH of the slurry is adjusted to 5.5 to precipitate Cr3+The filter cake after filter pressing is Cr (OH)3
(7) And (3) iron precipitation: will contain Fe2+The filtrate is returned to the crude iron-chromium alum process, and the iron content is supplemented to the filtrate or directly added with alkali liquor for precipitation, and the filtrate is oxidized in the air to obtain Fe (OH)3
4. A method according to any one of claims 1-3, characterized in that: the metal elements comprise iron, chromium, copper, zinc, nickel, cobalt and manganese.
5. The method as claimed in any one of claims 1 to 3, wherein the molar ratio of total iron to total chromium in the integrated sludge mixture of step (1) is 2.5 ~ 3.5.5: 1, and the sludge and water are slurried in a mass ratio of 1:1 ~ 5.
6. The method according to any one of claims 1-3, wherein the pulping in step (4) is performed by formulating the crude jarosite filter cake with water at a ratio of 1:1 ~ 3.
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