CN114873615A - Method for preparing magnesium sulfate by removing iron from asbestos tailings - Google Patents
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Abstract
The invention provides a method for preparing magnesium sulfate by removing iron from asbestos tailings, which comprises the following steps: roasting and activating the asbestos tailings to obtain a roasted and activated product; placing the roasted and activated product in an acid or salt solution containing sulfate radicals for leaching reaction, and filtering to obtain high-magnesium acidic filtrate; adding oxidant dropwise into the high-magnesium acidic filtrate while heating and stirring, and mixing Fe in the solution 2+ Conversion to Fe 3+ Then, obtaining a mixed solution; slowly dropwise adding an iron-removing precipitator into the mixed solution for precipitation reaction, dropwise adding the mixed solution until the pH value of the precipitation reaction is at the end, and continuously stirring to obtain a reaction product; and filtering the reaction product to obtain filter residue and a magnesium sulfate solution. The method for preparing the refined magnesium sulfate solution by removing iron from the asbestos tailing roasting product leaching solution has the advantages of short process, high efficiency and low cost, and has the advantages of high iron removal rate, low magnesium loss rate and good filtering performance of the produced precipitated iron slag.
Description
Technical Field
The invention belongs to the technical field of solid waste treatment, and particularly relates to a method for preparing magnesium sulfate by removing iron from asbestos tailings.
Background
China has rich asbestos mineral resources, but China has low grade of asbestos minerals, and a large amount of asbestos tailings are generated in the production process, so that a large amount of asbestos tailings are accumulated. The accumulation of the asbestos tailings not only causes the waste of mineral resources, but also occupies land resources, andand adversely affects the surrounding environment and the health of residents. The main mineral compositions of the asbestos tailings are serpentine, talc, magnetite and the like, and the chemical components are mainly SiO 2 MgO, containing a small amount of Fe 3 O 4 、Al 2 O 3 CaO, and the like.
At present, in the purification process of chemical solution, the method for removing iron mainly comprises two main types of chemical precipitation method and selective solvent extraction method. Of which chemical precipitation is most common in industrial applications. The goethite method has the advantages of good slag filtering performance, high iron removal rate and the like, and is one of important chemical solution iron removal methods. The Chinese patent with publication number "CN 114058844A" discloses a method for removing iron from intermediate products, wherein the method is used for removing iron from nickel or cobaltic acid immersion liquid by using goethite method, although the process realizes the removal of iron element, the reaction temperature is as high as 85-95 ℃, and the reaction time is long. The Chinese patent publication No. CN114058847A discloses a method for removing iron from a chlorine leachate of nickel concentrate, which is a method for removing iron from a chlorine leachate of nickel ore by utilizing goethite, and improves the reaction speed and reduces the reaction time by adding goethite crystal seeds, but the reaction temperature is still as high as 85-90 ℃ and the reaction time is 4 hours. The Chinese patent with the publication number of CN113897499A discloses a method for removing iron from a cobalt solution by a goethite method, which has the defects that although the reaction time is short, the content of favorable iron ions in a reaction kettle needs to be kept less than 1g/L in the reaction process, and the industrial practical operation difficulty is high.
In conclusion, the existing goethite method for removing iron has the defects of high reaction temperature, long reaction time consumption, great operation difficulty and the like caused by extra precision of the control requirement on the concentration of iron ions in the reaction. In the existing treatment method, other components are lost in the iron removal process, or precipitates are difficult to filter, or the operation is difficult and the like.
Disclosure of Invention
The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, one of the purposes of the invention is to provide a method for preparing magnesium sulfate by removing iron from asbestos tailings.
To make it practicalIn order to achieve the above object, one aspect of the present invention provides a method for preparing magnesium sulfate by removing iron from asbestos tailings, comprising the following steps: roasting and activating the asbestos tailings to obtain a roasted and activated product; placing the roasted and activated product in an acid or salt solution containing sulfate radicals for leaching reaction, and filtering to obtain high-magnesium acidic filtrate; adding oxidant dropwise into the high-magnesium acidic filtrate while heating and stirring, and mixing Fe in the solution 2+ Conversion to Fe 3+ Then, obtaining a mixed solution; slowly dropwise adding an iron-removing precipitator into the mixed solution for precipitation reaction, and continuously stirring after dropwise adding the iron-removing precipitator to the end-point pH value of the precipitation reaction to obtain a reaction product, wherein the end-point pH value is 4.0-5.0; and filtering the reaction product to obtain filter residue and a magnesium sulfate solution.
In an exemplary embodiment of the present invention, the temperature of the calcination activation may be 650 to 750 ℃, and the calcination time may be 30 to 90 min.
In an exemplary embodiment of the invention, the sulfate containing acid or salt solution may include one or more of a sulfuric acid solution, an ammonium bisulfate solution, an ammonium sulfate solution.
In an exemplary embodiment of the invention, the liquid-solid ratio of the leaching reaction may be 14 to 20ml/g, the temperature of the leaching reaction may be 15 to 60 ℃, the time of the leaching reaction may be 30 to 60min, and the pH of the leaching reaction may be 0.2 to 1.0.
In an exemplary embodiment of the present invention, the temperature of the precipitation reaction may be 40 to 100 ℃, and the time for continuing the stirring may be 10 to 30 min.
In an exemplary embodiment of the present invention, the method may further include: slowly dripping a neutralizing agent into the mixed solution until the pH value of the mixed solution is 2.0-2.5, and then dripping the iron removal precipitator until the pH value of the mixed solution is 4.0-5.0.
In an exemplary embodiment of the invention, the oxidant may include hydrogen peroxide, and a mixing ratio of the oxidant to the high-magnesium acidic filtrate may be 0.01 to 0.015 mol: 1L of the compound.
In an exemplary embodiment of the invention, the neutralizing agent may include one or more of magnesium carbonate, basic magnesium carbonate, and magnesium hydroxide, and the neutralizing agent may be added in an amount of 2.0 to 2.5 to the pH of the mixed solution.
In an exemplary embodiment of the present invention, the precipitant may include ammonia and/or sodium hydroxide, and may be added in an amount of 4.0 to 5.0 to a pH of the mixed solution.
In an exemplary embodiment of the present invention, the temperature of the neutralization reaction and the precipitation reaction may be 40 ℃ to 100 ℃, and the time for continuing the stirring may be 10min to 30 min.
In an exemplary embodiment of the invention, the mineral composition of the filter residue may include goethite and jarosite, or goethite and jarosite.
In an exemplary embodiment of the present invention, the magnesium sulfate solution has a loss rate of magnesium ions of 5% or less and an iron removal rate of 99% or more.
Compared with the prior art, the beneficial effects of the invention can comprise at least one of the following:
1) the reaction activity of the product of the asbestos tailings after roasting and activation is increased, so that the effective leaching of the roasted and activated product by sulfuric acid, ammonium bisulfate and ammonium sulfate solution can be realized, and a crude magnesium sulfate solution is obtained;
2) one or more of sulfuric acid, ammonium bisulfate and ammonium sulfate solution are adopted for leaching, so that a technical foundation can be laid for recycling of waste liquid;
3) before the iron is removed by precipitation, the addition amount of an iron removal precipitator can be reduced by adding a neutralizing agent, the neutralizing agent used in the neutralization reaction is a magnesium-containing compound, a magnesium sulfate solution is formed after the neutralizing agent reacts with acid, and the precipitate of the magnesium-containing compound cannot be formed under the set neutralization pH value condition, so that the formation amount of an iron removal precipitate is reduced, and the solid-liquid separation of the subsequent steps is facilitated;
4) according to the invention, goethite is directly generated in the process of precipitation and iron removal without introducing external seed crystals, so that the operation steps of the traditional goethite method are simplified, and the formation of goethite precipitates is beneficial to improving the solid-liquid separation efficiency in the subsequent steps;
5) the iron removal efficiency of the crude magnesium sulfate solution is more than 99 percent, and the highest iron removal efficiency can reach 99.99 percent; the loss rate of magnesium ions is below 5 percent, and the minimum loss rate can reach 2.3 percent;
6) the method for preparing the refined magnesium sulfate solution by removing iron from the asbestos tailing roasting product leaching solution with short process, high efficiency and low cost has the advantages of high iron removal rate, low magnesium loss rate and good filtering performance of the produced precipitated iron slag;
7) according to the invention, the asbestos tailing roasted product mainly containing serpentine is leached to extract magnesium oxide components and is separated from silicon dioxide residues, refined magnesium sulfate solution is obtained by refining crude magnesium sulfate of leaching solution, and can be used for preparing series magnesium-containing compound products, and the silicon dioxide residues can be used for preparing silicon-containing series compound products, so that the resource utilization of solid waste is realized, and the method has important resource and environment protection and ecological and sustainable development significance.
Drawings
Fig. 1 shows XRD patterns before and after calcination of asbestos tailings of example 1 of the present invention;
figure 2 shows the XRD pattern of the leach residue of example 1 of the present invention;
FIG. 3 shows an X-ray diffraction pattern of an iron-precipitating filter residue according to example 1 of the present invention;
fig. 4 shows XRD patterns of samples of asbestos tailings before and after firing of example 6 of the present invention;
figure 5 shows XRD patterns of filter residue at different reaction end points pH for ammonia treated pickle liquor of example 6 of the present invention;
FIG. 6 shows an infrared spectrum of the filter residue at different reaction end points pH for example 6 of the present invention;
FIG. 7 shows the iron removal rate and magnesium loss rate at different reaction endpoint pH values for example 6 of the present invention;
FIG. 8 shows the filtration rate of suspensions of pickle liquor of example 6 of the invention at different reaction end points pH;
figure 9 shows XRD patterns of the filter residue of the pickle liquor of example 6 of the present invention at different reaction temperatures;
FIG. 10 shows an infrared spectrum of the filter residue at different reaction temperatures for example 6 of the present invention;
FIG. 11 shows the iron removal rate and the magnesium loss rate at different reaction temperatures for example 6 of the present invention;
FIG. 12 shows the filtration rates of the products at different reaction temperatures for example 6 of the present invention;
FIG. 13 shows the iron removal rate and the magnesium loss rate at different reaction times for example 6 of the present invention;
figure 14 shows the filtration rate of the product at different reaction times for example 6 of the present invention.
Detailed Description
Hereinafter, a method for preparing magnesium sulfate by removing iron from asbestos tailings according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.
It is noted that "first" and "second" are merely used for convenience of distinction and description, and do not indicate or imply importance or order.
The main mineral compositions of the asbestos tailings are serpentine, talc, magnetite and the like, and the chemical components are mainly SiO 2 MgO, containing a small amount of Fe 3 O 4 、Al 2 O 3 CaO, and the like. The acid leaching process is a classic process for resource utilization of asbestos tailings, and the acid leaching solution (namely crude magnesium sulfate solution) of the asbestos tailings mainly contains Mg 2+ In addition, it contains other impurity ions, such as more Fe 3+ 、Fe 2+ And a small amount of Al 3+ And purifying to obtain refined magnesium sulfate solution, and further preparing magnesium-containing compounds such as magnesium oxide and magnesium hydroxide. Since the iron ions have high reactivity, in order to obtain a high-purity magnesium-containing compound product, it is necessary to first remove the iron ions from the solution. Therefore, the removal of iron ions in the asbestos tailing acid leaching solution has important technical significance.
The iron removal method mainly comprises a chemical precipitation method and a selective solvent extraction method. Among them, the chemical precipitation method is most common in industrial applications, in which an excess of oxidant is first added to precipitate Fe 2+ Conversion to Fe 3+ Then addAdding alkaline reagents such as sodium hydroxide, calcium oxide, calcium hydroxide, ammonia water and the like, and adjusting the end point pH value of the solution. Under different reaction conditions (temperature, time, reaction end point pH, iron ion concentration, etc.), iron ions can form different precipitates, such as hydroxylated complex salts (MFe) 3 (SO 4 ) 2 (OH) 6 ) Hematite (Fe) 2 O 3 ) Goethite (FeOOH) and iron hydroxide (Fe (OH) 3 ) And the like. The chemical precipitation method can be classified into an ammonium-sodium jarosite method, a goethite method, a hematite method, and the like according to the difference of the precipitation products. However, the iron removal process has certain application limitations: the sodium (ammonium) jarosite method has high acid consumption, large slag yield and reaction temperature higher than 90 ℃; the reaction end point of the hematite method has higher pH value and maximum energy consumption; the hydroxide precipitation method is simple in reaction conditions, but tends to produce a colloid of iron hydroxide having poor filterability. The goethite process can be carried out at normal pressure and at relatively low temperatures, and according to thermodynamic data, Fe 3+ The hydrolysis product of (A) should be goethite rather than colloidal iron hydroxide, but Fe when the pH of the solution is high 3+ At higher concentrations, Fe 3+ Most or all of the hydrolysate was colloidal ferric hydroxide which was not easily filtered.
Aiming at the problem that the iron removal of the asbestos tailing roasting product leachate is the largest, iron hydroxide colloid which is difficult to filter is easily generated, and Fe is obtained according to thermodynamic data 3+ The hydrolysis product of (A) should be goethite rather than colloidal iron hydroxide, but Fe when the pH of the solution is high 3+ At higher concentrations, Fe 3+ Most or all of the hydrolysate was colloidal ferric hydroxide which was not easily filtered. Therefore, the kind of the product precipitate can be controlled by controlling the reaction conditions, the filtering performance is improved, the iron removal process flow can be simplified, and the industrial cost can be saved.
The embodiment of the invention aims at treating the leachate of the asbestos tailing roasting product, and the neutralizing agent is firstly adopted to control the reaction system to be close to the pH value of goethite and ammonium (sodium) jarosite precipitate, so that the addition amount of the subsequent precipitating agent can be reduced, and the added neutralizing agent is a magnesium-containing compound. Wherein, the final product of the invention is refined magnesium oxide solution for production.
First exemplary embodiment
In a first exemplary embodiment of the present invention, there is provided a method for preparing magnesium sulfate by removing iron from asbestos tailings, the method comprising the steps of:
and S1, roasting and activating the asbestos tailings to obtain a roasted and activated product.
Specifically, the asbestos tailing powder is roasted and activated in a high-temperature roasting furnace to obtain a roasted and activated product.
In this embodiment, the asbestos tailings may include 37.0% to 42.0% by mass of SiO 2 36.0 to 42.0 percent of MgO and 0.8 to 1.2 percent of Al 2 O 3 3.0% -8.0% of TFe 2 O 3 0.4 to 0.7 percent of CaO. The loss on ignition of the asbestos tailings can be 12.0-13.5%.
Specifically, TFe 2 O 3 Represents total iron, including Fe 2 O 3 +FeO。
Alternatively, the mineral species contained in the asbestos tailings fines may include primarily serpentine and may also include a minor amount of at least one of talc, magnetite, brucite, and chlorite.
Wherein, serpentine roasting decomposition formula:
(Mg,Fe) 3 Si 2 O 5 (OH) 4 ＝nMgO·mFe 2 O 3 ·xSiO 2 +2H 2 O↑
wherein, the serpentine roasting decomposition principle is as follows: after the asbestos tailings are roasted, the main phase serpentine in the tailings is subjected to dehydroxylation reaction to remove structural water, and the structure of the serpentine is decomposed and destroyed to form an amorphous compound, so that the extraction rate of MgO is improved.
Alternatively, the temperature of roasting activation can be 650-750 ℃, and the roasting time can be 30-90 min. For example, the temperature may be 660, 680, 700 ℃ and the time may be 40, 60, 80 min.
Wherein, the main purpose of roasting is to destroy the serpentine structure and promote the subsequent leaching of magnesium ions. When the roasting temperature is too low or the roasting time is too short, the damage degree of the serpentine structure is low, and the leaching rate of magnesium ions is reduced; when the calcination temperature is too high or the calcination time is too long, the formed forsterite increases and the leaching rate of magnesium ions also decreases.
Specifically, the purpose of firing is to destroy the serpentine structure, forsterite is a product of the decomposition by firing of serpentine, but generally not all of the serpentine is decomposed into forsterite after firing, and a part of the serpentine remains in the original serpentine state, and is referred to as undecomposed serpentine.
That is, the mineral species contained in the roasted activated product may mainly include forsterite and hematite, and may further include undecomposed serpentine.
S2, placing the roasted and activated product into an acid or salt solution containing sulfate radicals for leaching reaction, and filtering to obtain high-magnesium acidic filtrate.
Specifically, the roasted and activated product is put into a reaction kettle which contains sulfate radical-containing acid or salt solution and is provided with a stirring and heating device for leaching reaction, and after the leaching reaction is finished, filtration is carried out to obtain high-magnesium acidic filtrate.
Alternatively, the filtration may be by pressure filtration to obtain a filtrate.
The filtration performance can be measured by
A common funnel,
Filtering the reaction product with medium-speed qualitative filter paper, and recording the volume V of the filtrate filtered for 5min f The filtration rate V of the reaction product is calculated from the formula (1):
in the formula, V f Represents the volume of filtrate filtered in ml, t represents time in min. Specifically, the sulfate-containing acid or salt solution may include one or more of a sulfuric acid solution, an ammonium bisulfate solution, and an ammonium sulfate solution.
Wherein the content of the first and second substances,
the molar concentration may be 1.2 to 1.8mol/L, for example 1.2, 1.4, 1.6 mol/L.
Alternatively, the pH of the leaching reaction may be adjusted to 0.2 to 1.0, for example 0.2, 0.4, 0.8, using an acidic reaction solution. Alternatively, the liquid-solid ratio of the leaching reaction may be 14-20 ml/g, such as 15, 16, 18 ml/g. Too low a liquid-solid ratio results in low magnesium ion leaching rate, and too high a liquid-solid ratio results in low reaction rate and increased reaction time.
Alternatively, the temperature of the leaching reaction may be between 15 ℃ and 60 ℃, e.g. 30, 40, 60 ℃. Too low a temperature results in insufficient reaction and low leaching rate of magnesium ions. Alternatively, the leaching reaction may be carried out for a period of 30min to 60min, e.g., 30min, 40min, 60min, etc., with too short a reaction time (e.g., < 30min) resulting in incomplete reaction and too long a reaction time (e.g., > 60min) increasing time costs.
The filtrate obtained after acid leaching of the asbestos tailing roasted product is high-magnesium acidic filtrate, which can be called as crude magnesium sulfate solution, and the concentration of iron ion impurities is low, for example, the concentration of iron ions in the solution can be 0.80-1.20 g/L, and the concentration of magnesium ions can be 12.06-19.00 g/L.
Wherein, the leaching principle is as follows:
nMgO·mFe 2 O 3 ·xSiO 2 +(m+n)(NH 4 ) 2 SO 4 ＝xSiO 2 ↓+nMgSO 4 +mFe 2 (SO 4 ) 3 +(m+n)NH 3 ↑
nMgO·mFe 2 O 3 ·xSiO 2 +NH 4 HSO 4 ＝xSiO 2 ↓+nMgSO 4 +mFe 2 (SO 4 ) 3 +(m+n)NH 3 ↑
nMgO·mFe 2 O 3 ·xSiO 2 +H 2 SO 4 ＝xSiO 2 ↓+nMgSO 4 +mFe 2 (SO 4 ) 3 +(m+n)NH 3 ↑
s3, dropwise adding an oxidant into the high-magnesium acidic filtrate while heating and stirring, and mixing Fe in the solution 2+ Conversion to Fe 3+ After that, a mixed solution was obtained.
Specifically, the high-magnesium acidic filtrate is placed in a reaction kettle with a stirring and heating device, and oxidant is dripped into the solution of the reaction kettle while heating and stirring to make Fe in the solution 2+ Conversion to Fe 3+ 。
The oxidant can comprise hydrogen peroxide, and the mixing ratio of the oxidant to the high-magnesium acidic filtrate is 0.01-0.015 mol: 1L of the compound. For example, 0.010 mol: 1L, 0.012 mol: 1L, 0.015 mol: 1L of the compound. That is, the oxidizing agent is used in an amount of 0.010 to 0.015mol, for example, 0.010, 0.012, 0.015mol, per liter of the high-magnesium acidic filtrate. The hydrogen peroxide has the function of oxidizing ferrous ions in the solution, and the excessive addition of the hydrogen peroxide can cause the oxidation of part of the ferrous ions and the waste of reagents.
S4, slowly adding an iron removal precipitator into the mixed solution dropwise to perform precipitation reaction, and continuously stirring after dropwise adding the iron removal precipitator to the final pH value of the precipitation reaction to obtain a reaction product, wherein the final pH value is 4.0-5.0.
Optionally, the precipitating agent comprises ammonia and/or sodium hydroxide configured as OH - The concentration of the solution is 3-7 mol/L, such as 3, 4 and 6 mol/L. Too low a precipitant concentration will reduce the reaction rate, and too high a precipitant concentration will impose more stringent requirements on the equipment.
Optionally, the final pH value of the mixed solution added into the reaction system by the precipitant is 4.0-5.0, such as 4.0, 4.5, 5.0. The pH value of the end point of the solution is too small, so that the iron ions are incompletely precipitated, and the iron removal rate is low; too high an end point pH of the solution can lead to the formation of colloidal iron hydroxide and thus to filtration difficulties.
Optionally, the stirring time is 10min to 30min, for example 10min, 20min, 30min after the reaction pH value is 4.0 to 5.0. Too short a reaction time may result in incomplete reaction, and too long a reaction time may increase time costs.
S5, filtering the reaction product to obtain filter residue and a magnesium sulfate solution.
Among them, the magnesium sulfate solution may be referred to as a purified magnesium sulfate solution.
Alternatively, the mineral composition of the filter residue may comprise goethite, jarosite and/or ammonioiarosite. In particular, the mineral composition may include goethite and jarosite, or goethite and jarosite.
Wherein, the iron removing principle of the precipitator comprises goethite precipitation principle, ammoniojarosite precipitation principle and natrojarosite precipitation principle.
Goethite precipitation principle:
Fe 3+ +2H 2 O＝FeOOH↓+3H +
precipitation principle of ammonioiarosite:
3Fe 2 (SO 4 ) 3 +6H 2 O＝6Fe(OH)SO 4 +3H 2 SO 4
4Fe(OH)SO 4 +4H 2 O＝2Fe(OH) 4 SO 4 +2H 2 SO 4
2NH 3 ·H 2 O+Fe(OH)SO 4 +Fe(OH) 4 SO 4 ＝(NH 4 ) 2 Fe 6 (SO 4 ) 4 (OH) 12 ↓
the precipitation principle of the sodium jarosite is as follows:
3Fe 2 (SO 4 ) 3 +6H 2 O＝6Fe(OH)SO 4 +3H 2 SO 4
4Fe(OH)SO 4 +4H 2 O＝2Fe(OH) 4 SO 4 +2H 2 SO 4
2NaOH+Fe(OH)SO 4 +Fe(OH) 4 SO 4 ＝Na 2 Fe 6 (SO 4 ) 4 (OH) 12 ↓
alternatively, Mg in magnesium sulfate solution 2+ The concentration of the Mg can be 11.34-18.62 g/L, and Mg is generated in the iron removal process 2+ The loss rate of (2) is only 0.5% to 8%, and further, the loss rate of magnesium ions can be controlled to 5% or less, for example, 2.3%, Fe in the solution 3+ The concentration of the iron-removing agent can be 0.0008-0.012 g/L, and the iron-removing rate in the iron-removing process is 99.0% -99.99%, such as 99.98%.
Alternatively, the iron removal rate and the magnesium loss rate can be measured by the following methods:
and (3) measuring the concentration of iron ions in the filtrate by adopting a spectrophotometry, wherein the removal efficiency alpha of the iron ions is calculated by a formula (2):
in the formula: c Fe The concentration of iron ions in the solution before iron removal is mg/L; v is the total volume of the solution before iron removal, L; c Fe' The concentration of iron ions in the solution after iron removal is mg/L; v' is the total volume of the solution after iron removal, L.
The concentration of magnesium ions in the filtrate was determined by modified EDTA standard titration: taking 1mL of filtrate, putting the filtrate into a 200mL conical flask, sequentially adding 20mL of ultrapure water, 1mL of 0.1mol/L potassium sodium tartrate solution, 2mL of 1+3 triethanolamine solution and 2mL of 6mol/L sodium hydroxide solution, uniformly mixing, and adding 0.1g of calcium indicator, wherein the solution is light red; titrating with EDTA standard solution until the solution becomes pure blue, and recording the consumption V of EDTA 1 (ii) a Taking 1mL of filtrate into a 200mL conical flask, and sequentially adding 20mLH 2 O, 1mL of 0.1mol/L potassium sodium tartrate solution, and the volume ratio of 1: 3, and 2mL of water, 5mL of ammonium chloride-ammonia water buffer solution with the pH value of 10, uniformly mixing, and adding 0.1gKB indicator, wherein the solution is light red; titrating with EDTA standard solution until the solution becomes pure blue, and recording the consumption V of EDTA 2 . Repeating the steps for three times, and taking an average value. Magnesium ion C in solution Mg The concentration can be calculated from equation (3):
the loss rate β of ions is calculated by the formula (4):
in the formula: c Mg The concentration of magnesium ions in the solution before iron removal is mg/L; v is the total volume of the solution before iron removal, L; c Mg' For removing iron from the solutionThe concentration of medium magnesium ions is mg/L; v' is the total volume of the solution after iron removal, L.
Second exemplary embodiment
In the second exemplary embodiment of the present invention, a method for preparing magnesium sulfate by removing iron from asbestos tailings is provided, and the steps of the method except for step S4 may be the same as the method for removing iron from asbestos tailings in the first exemplary embodiment.
In the present embodiment, step S4' is included: slowly dropwise adding a neutralizing agent and an iron removal precipitator into the mixed solution, carrying out neutralization reaction and precipitation reaction, dropwise adding the solution until the reaction pH value is 4.0-5.0, and stirring to obtain a reaction product.
Specifically, slowly dropwise adding a neutralizing agent and an iron removal precipitator into the mixed solution to perform neutralization reaction and precipitation reaction, continuously stirring after dropwise adding until the pH value of the precipitation reaction end point is 4.0-5.0, and obtaining a reaction product after stirring.
Specifically, the step of slowly dropping the neutralizer and the iron removing precipitant into the mixed solution may include: firstly, slowly dripping a neutralizing agent into the mixed solution until the pH value of the mixed solution is 2.0-2.5, and then dripping a precipitator into the mixed solution until the pH value of the mixed solution is 4.0-5.0.
Wherein the neutralizing agent is added to adjust the pH value of the mixed solution to be close to but not more than the pH value of iron ion precipitation, so as to reduce the adding amount of the subsequent precipitating agent. Before adding the precipitator for deironing, the addition amount of the precipitator can be reduced by adding the neutralizer, the neutralizer used in the neutralization reaction is a magnesium-containing compound, a magnesium sulfate solution is formed after the neutralizer reacts with acid, and the precipitate of the magnesium-containing compound cannot be formed under the set neutralization pH value condition, so that the formation amount of an deironing precipitate is reduced, and the solid-liquid separation of the subsequent steps is facilitated.
Alternatively, the neutralizing agent may include one or more of magnesium carbonate, basic magnesium carbonate, magnesium hydroxide.
Optionally, the neutralizing agent is added in an amount to make the pH value of the mixed solution 2.0-2.5, such as 2.0, 2.3, 2.5. After the neutralization reaction, the use amount of the precipitator is increased due to the excessively low pH value of the mixed solution in the system, and the iron ions are precipitated due to the excessively high pH value, so that the filtering difficulty is increased.
Alternatively, the temperature of the neutralization and precipitation reactions may be from 40 ℃ to 90 ℃, e.g., 40, 60, 80 ℃. Too low a reaction temperature leads to low crystallization of the precipitate, and too high a reaction temperature leads to safety problems and increased energy consumption.
According to the embodiment of the invention, the method for preparing the refined magnesium sulfate solution by removing iron from the asbestos tailing roasting product leachate can not only realize resource utilization of asbestos tailings, save land resources and protect the environment, but also has simple and convenient operation, stable iron removal efficiency of more than 99 percent and stable magnesium ion loss rate of less than 5 percent.
In order to better understand the above exemplary embodiments of the present invention, a method for preparing magnesium sulfate by removing iron from asbestos tailings is described below with reference to specific examples.
Example 1
The method for preparing the magnesium sulfate by removing iron from the asbestos tailings comprises the following steps:
the mineral types of the akkerite rock tailings selected in the test are mainly serpentine, and the akkerite rock tailings contain a small amount of talc, magnetite, chlorite and the like, and the main chemical components are shown in table 1:
TABLE 1 main chemical composition of asbestos tailings
| Element(s) | SiO 2 | Al 2 O 3 | TFe 2 O 3 | MgO | CaO | Loss on ignition | Others are |
| Content w B /％ | 40.33 | 1.20 | 3.09 | 41.59 | 0.47 | 12.74 | 0.58 |
A method for preparing refined magnesium sulfate solution by removing iron from asbestos tailing roasting product leachate comprises the following steps:
(1) placing the asbestos tailing powder in a high-temperature furnace, and roasting for 90min at the temperature of 650 ℃ to obtain a roasted and activated product, wherein the mineral types contained in the roasted and activated product mainly comprise forsterite, hematite and quartz, and also contain undecomposed serpentine;
(2) then placing the asbestos tailings after roasting activation into a reaction kettle with stirring and heating functions, and adding H with the concentration of 1.2mol/L 2 SO 4 Controlling the pH value of the solution in the reaction kettle to be 0.2, reacting for 30min at the temperature of 40 ℃ and the liquid-solid ratio of 14ml/g, and performing pressure filtration on a product after the reaction to obtain a crude magnesium sulfate solution, wherein the concentration of iron ions in the filtrate is 0.80g/L, and the concentration of magnesium ions is 12.06 g/L;
(3) placing the crude magnesium sulfate solution in a reaction kettle with stirring and heating functions, dropwise adding 0.015mol of hydrogen peroxide per liter of the crude magnesium sulfate solution, adding magnesium hydroxide into the solution until the pH of a reaction system is 2.0, slowly dropwise adding 3mol/L of sodium hydroxide solution until the pH of a reaction end point is 4.0, reacting for 30min at 40 ℃, and allowing a product after the reaction to pass through the reaction kettle by gravityFiltering with a filter to obtain refined magnesium sulfate solution, and adding Mg into the refined magnesium sulfate solution 2+ Has a concentration of 11.59g/L and Fe in the solution 3+ The concentration of the filter residue is 0.00136g/L, and the mineral composition of the filter residue is goethite and jarosite.
Table 2 shows the analysis of the iron removal effect of the leachate of the asbestos tailing roasting product in example 1
| Iron removal rate/%) | Loss rate of magnesium/%) | Filtration rate/ml min -1 |
| 99.83 | 3.9 | 2.8 |
As can be seen from Table 2, the iron removal rate after the iron removal step reaches 99.83%, the iron removal effect is good, the magnesium loss rate is 3.9%, the magnesium loss rate is low, and the filtering speed is 2.8ml/min -1 It can be seen that the filtration performance is good.
Fig. 1 shows XRD patterns before and after roasting of the asbestos tailings of example 1 of the present invention, and it can be seen that the main phase of the tailings sample before roasting is chrysotile, and the tailings sample also contains a small amount of talc, magnetite and chlorite. After the tailing sample is roasted for 90min at 650 ℃, the back of the diffraction peak is increased, part of the diffraction peak is amorphized, the intensity of the diffraction peak of the chrysotile is weakened, and a series of new peaks appear. Mainly forms forsterite, hematite and quartz. This is because magnetite in the asbestos tailing sample is oxidized to hematite, a part of the structure of chrysotile is destroyed, and the decomposition products are crystallized to form forsterite and quartz.
Fig. 2 shows the XRD pattern of the leached residue of example 1 of the present invention, and it can be seen that the intensity of the characteristic diffraction peak of serpentine is reduced during the acid leaching process of the asbestos tailings sample, indicating that the structure is significantly damaged. Fig. 3 shows an X-ray diffraction pattern of the iron-precipitating slag of example 1 of the present invention, and it can be seen that the iron-precipitating slag mainly contains goethite and jarosite.
Example 2
The method for preparing the magnesium sulfate by removing iron from the asbestos tailings comprises the following steps:
the mineral types of the akkerite tailings selected in the test are mainly serpentine, and the akkerite tailings contain a small amount of talc, magnetite, chlorite and the like, and the main chemical components are shown in a table 3:
table 3 shows the main chemical components of asbestos tailings
| Element(s) | SiO 2 | Al 2 O 3 | TFe 2 O 3 | MgO | CaO | Loss on ignition | Others |
| Content w B /％ | 40.33 | 1.20 | 3.09 | 41.59 | 0.47 | 12.74 | 0.58 |
A method for preparing refined magnesium sulfate solution by removing iron from asbestos tailing roasting product leachate comprises the following steps:
(1) placing the asbestos tailing powder in a high-temperature furnace, and roasting for 30min at the temperature of 750 ℃ to obtain a roasted and activated product, wherein the mineral types contained in the roasted and activated product mainly comprise forsterite, hematite and quartz, and also contain undecomposed serpentine;
(2) then placing the calcined and activated asbestos tailings into a reaction kettle with stirring and heating functions, adding 1.6mol/L ammonium bisulfate solution, controlling the pH of the solution in the reaction kettle to be 0.8 by utilizing the sulfuric acid solution, reacting for 60min under the conditions that the temperature is 60 ℃ and the liquid-solid ratio is 16ml/g, and carrying out filter pressing on a product after reaction to obtain a crude magnesium sulfate solution, wherein the concentration of iron ions in a filtrate is 1.2g/L, and the concentration of magnesium ions is 18.46 g/L;
(3) placing the crude magnesium sulfate solution in a reaction kettle with stirring and heating functions, dropwise adding 0.015mol of hydrogen peroxide per liter of the crude magnesium sulfate solution, adding magnesium carbonate into the solution until the pH of a reaction system is 2.5, slowly dropwise adding 6mol/L ammonia water solution until the pH of a reaction end point is 5.0, reacting for 20min at 100 ℃, filtering a product after reaction by using a gravity filter to obtain a refined magnesium sulfate solution, and refining Mg in the magnesium sulfate solution 2+ Has a concentration of 18.04g/L and Fe in the solution 3+ The concentration of the filter residue is 0.008g/L, and the mineral composition of the filter residue is goethite and ammonium jarosite.
Table 4 shows the analysis of the iron removal effect of the leachate of the asbestos tailing roasting product in example 2
| Iron removal rate/%) | Loss rate of magnesium/%) | Filtration rate/ml min -1 |
| 99.33 | 2.3 | 3.6 |
As can be seen from Table 4, the iron content after the iron removal step reached 99.33%, the iron removal effect was very good, the loss of magnesium was 2.3%, it was found that the loss of magnesium was low, and the filtration rate was 3.6ml/min -1 It can be seen that the filtration performance is good.
Example 3
The method for preparing the magnesium sulfate by removing iron from the asbestos tailings comprises the following steps:
the mineral types of the rock rockwool tailings selected in the test are mainly serpentine, small amounts of talc, magnetite and brucite, and the main chemical components are shown in the following table 5:
TABLE 5 major chemical composition of asbestos tailings
A method for preparing refined magnesium sulfate solution by removing iron from asbestos tailing roasting product leachate comprises the following steps:
(1) placing the asbestos tailing powder in a high-temperature furnace, and roasting for 40min at 700 ℃ to obtain a roasted and activated product, wherein the mineral types contained in the roasted and activated product mainly comprise forsterite and hematite and also contain undecomposed serpentine;
(2) then placing the calcined and activated asbestos tailings into a reaction kettle with stirring and heating functions, adding an ammonium sulfate solution with the concentration of 1.8mol/L, controlling the pH of the solution in the reaction kettle to be 1.0 by adopting a sulfuric acid solution, reacting for 60min under the conditions that the temperature is 15 ℃ and the liquid-solid ratio is 20ml/g, and carrying out filter pressing on a product after the reaction to obtain a rough magnesium sulfate solution, wherein the concentration of iron ions in a filtrate is 1.2g/L, and the concentration of magnesium ions is 19.00 g/L;
(3) placing the rough magnesium sulfate solution in a reaction kettle with stirring and heating functions, dropwise adding 0.015mol of hydrogen peroxide per liter of the rough magnesium sulfate solution, adding basic magnesium carbonate into the solution until the pH of a reaction system is 2.5, slowly dropwise adding 4mol/L of sodium hydroxide solution until the pH of a reaction end point is 4.5, reacting for 10min at 80 ℃, filtering a product after reaction by using a gravity filter to obtain a refined magnesium sulfate solution, and refining Mg in the magnesium sulfate solution 2+ Has a concentration of 18.34g/L and Fe in the solution 3+ The concentration of the filter residue is 0.0008g/L, and the mineral composition of the filter residue is goethite and jarosite.
Table 6 shows the analysis of the iron removal effect of the leachate of the calcination product of asbestos tailings in example 3
| Iron removal rate/%) | Rate of magnesium loss/%) | Filtration rate/ml min -1 |
| 99.93 | 3.5 | 3.2 |
As can be seen from Table 6, the iron removal rate after the iron removal step reached 99.93%, the iron removal effect was good, the loss rate of magnesium was 3.5%, it was found that the loss rate of magnesium was low, and the filtration rate was 3.2ml/min -1 It can be seen that the filtration performance is good.
Example 4
The method for preparing the magnesium sulfate by removing iron from the asbestos tailings comprises the following steps:
the mineral types of the rock rockwool tailings selected in the test are mainly serpentine, small amounts of talc, magnetite and brucite, and the main chemical components are shown in the following table 7:
table 7 shows the main chemical components of asbestos tailings
| Element(s) | SiO 2 | Al 2 O 3 | TFe 2 O 3 | MgO | CaO | Loss on ignition | Others |
| Content w B /％ | 37.89 | 0.81 | 6.91 | 40.25 | 0.54 | 13.03 | 0.57 |
A method for preparing refined magnesium sulfate solution by removing iron from asbestos tailing roasting product leachate comprises the following steps:
(1) placing the asbestos tailing powder in a high-temperature furnace, and roasting at 680 ℃ for 40min to obtain a roasted and activated product, wherein the mineral types contained in the roasted and activated product mainly comprise forsterite and hematite and also contain undecomposed serpentine;
(2) then placing the asbestos tailings after roasting activation into a reaction kettle with stirring and heating functions, and adding H with the concentration of 1.8mol/L 2 SO 4 Controlling the pH value of the solution in the reaction kettle to be 0.4 by adopting a sulfuric acid solution, reacting for 40min under the conditions that the temperature is 30 ℃ and the liquid-solid ratio is 14ml/g, and performing pressure filtration on a product after the reaction to obtain a crude magnesium sulfate solution, wherein the concentration of iron ions in the filtrate is 0.90g/L, and the concentration of magnesium ions is 13.05 g/L;
(3) placing the crude magnesium sulfate solution in a reaction kettle with stirring and heating functions, dropwise adding 0.015mol of hydrogen peroxide per liter of the crude magnesium sulfate solution, adding magnesium hydroxide into the solution until the pH of a reaction system is 2.5, slowly dropwise adding 5mol/L of ammonia water solution until the pH of a reaction end point is 4.5, reacting at 80 ℃ for 20min, filtering a product after reaction by using a gravity filter to obtain a refined magnesium sulfate solution, and refining Mg in the magnesium sulfate solution 2+ Has a concentration of 12.60g/L and Fe in the solution 3+ The concentration of the filter residue is 0.001g/L, and the mineral composition of the filter residue is goethite and ammonium jarosite.
Table 8 shows the analysis of the iron removal effect of the leachate of the calcination product of asbestos tailings in example 4
| Iron removal rate/%) | Loss rate of magnesium/%) | Filtration rate/ml min -1 |
| 99.82 | 3.5 | 1.9 |
As can be seen from Table 8, the iron content after the iron removal step reached 99.82%, the iron removal effect was good, the loss of magnesium was 3.5%, it was found that the loss of magnesium was low, and the filtration rate was 1.9ml/min -1 It can be seen that the filtration performance is good.
Example 5
The method for preparing the magnesium sulfate by removing iron from the asbestos tailings comprises the following steps:
the mineral types of the selected Shaanxi Daan asbestos tailings are mainly serpentine, and the selected Shaanxi Daan asbestos tailings contain a small amount of brucite, magnetite and chlorite, and the main chemical components are shown in Table 9:
TABLE 9 main chemical composition of asbestos tailings
| Element(s) | SiO 2 | Al 2 O 3 | TFe 2 O 3 | MgO | CaO | Loss on ignition | Others |
| Content w B /％ | 37.69 | 1.20 | 7.75 | 40.13 | 0.42 | 12.5 | 0.31 |
A method for preparing a refined magnesium sulfate solution by deironing an asbestos tailing roasting product leaching solution comprises the following steps:
(1) placing the asbestos tailing powder in a high-temperature furnace, and roasting at 680 ℃ for 60min to obtain a roasted and activated product, wherein the mineral types contained in the roasted and activated product mainly comprise forsterite and hematite and also contain undecomposed serpentine;
(2) then placing the calcined and activated asbestos tailings into a reaction kettle with stirring and heating functions, adding 1.6mol/L ammonium bisulfate solution, controlling the pH of the solution in the reaction kettle to be 0.4 by adopting sulfuric acid solution, reacting for 40min under the conditions of 30 ℃ and 18ml/g of liquid-solid ratio, and carrying out filter pressing on a product after reaction to obtain a crude magnesium sulfate solution, wherein the concentration of iron ions in a filtrate is 1.00g/L, and the concentration of magnesium ions is 17.65 g/L;
(3) putting the rough magnesium sulfate solution into a reaction kettle with stirring and heating functions, dropwise adding 0.015mol of hydrogen peroxide per liter of the rough magnesium sulfate solution, adding magnesium carbonate into the solution until the pH value of a reaction system is 2.0, and slowly dropwise adding 7mol/L ammonia water solution until the pH value of a reaction end point is4.5, reacting for 20min at 60 ℃, filtering the product after the reaction by adopting a gravity filter to obtain a refined magnesium sulfate solution, and adding Mg in the refined magnesium sulfate solution 2+ Has a concentration of 16.96g/L and Fe in the solution 3+ The concentration of the filter residue is 0.0015g/L, and the mineral composition of the filter residue is goethite and ammonium jarosite.
Table 10 shows the analysis of the iron removal effect of the leachate of the asbestos tailing roasting product in example 5
| Iron removal rate/%) | Loss rate of magnesium/%) | Filtration rate/ml min -1 |
| 99.85 | 3.9 | 3.5 |
As can be seen from Table 10, the iron content after the iron removal step reached 99.85%, the iron removal effect was good, the loss of magnesium was 3.9%, it was found that the loss of magnesium was low, and the filtration rate was 3.5ml/min -1 It can be seen that the filtration performance is good.
Example 6
The method for removing iron and preparing the magnesium sulfate solution in the asbestos tailings comprises the following steps of:
the mineral types of the akkerite tailings selected in the test are mainly serpentine, and the akkerite tailings contain a small amount of talc, magnetite, chlorite and the like, and the main chemical components are shown in a table 11:
TABLE 11 main chemical composition of asbestos tailings
A method for preparing refined magnesium sulfate solution by removing iron from asbestos tailing roasting product leachate comprises the following steps:
(1) placing the asbestos tailing powder in a high-temperature furnace, and roasting at 680 ℃ for 60min to obtain a roasted and activated product, wherein the mineral types contained in the roasted and activated product mainly comprise forsterite and hematite, and also comprise undecomposed serpentine and quartz;
(2) then placing the calcined and activated asbestos tailings into a reaction kettle with stirring and heating functions, adding a sulfuric acid solution with the concentration of 1.4mol/L, controlling the pH of the solution in the reaction kettle to be 0.2 by using the sulfuric acid solution, reacting for 40min under the conditions that the temperature is 30 ℃ and the liquid-solid ratio is 14ml/g, and carrying out pressure filtration on a product after the reaction to obtain a crude magnesium sulfate solution, wherein the concentration of iron ions in a filtrate is 1.00g/L, and the concentration of magnesium ions is 17.65 g/L;
(3) placing the crude magnesium sulfate solution in a reaction kettle with stirring and heating functions, dropwise adding 0.015mol of hydrogen peroxide per liter of the crude magnesium sulfate solution, slowly dropwise adding 5mol/L of ammonia water solution into the solution until the pH value reaches the specified reaction end point, reacting for a certain time at a set temperature, and filtering the product after the reaction by using a gravity filter to obtain the refined magnesium sulfate solution. Drying the obtained filter residue sample in a 105 ℃ oven for 24h, and packaging in a plastic package bag for later use, wherein the serial number is RE-pH-T, the pH value represents the reaction end point pH value, and the T represents the reaction temperature; the filtrate sample obtained was sealed for use and was numbered FL-pH-T.
Fig. 4 shows XRD patterns of samples of asbestos tailings before and after calcination of example 6 of the present invention. As shown in FIG. 4, the main phase in the tailings sample before roasting is chrysotile
Also contains a small amount of talc (
2490, 1530, 2530, d-133, d49, magnetite (2530,
) Chlorite, and their use
After the tailing sample is roasted for 1h at 680 ℃, the back of a diffraction peak is increased, part of the diffraction peak is amorphized, the intensity of the diffraction peak of the original chrysotile is weakened, and a series of new peaks appear. Mainly forming forsterite
Hematite (hematite)
d 116-1.690) quartz (d 100-4250,
). This is because, after the magnetite in example 6 was oxidized to hematite by calcination, a part of the structure of chrysotile was destroyed, and the decomposition product was crystallized to form forsterite and quartz.
Figure 5 shows XRD patterns of filter residue of ammonia treated pickle liquor of example 6 of the present invention at different reaction end points pH. As can be seen from FIG. 5, when the end point of the reaction was adjusted to pH 4.0, the filter residue was mainly composed of goethite
And Ammonitum
Forming; when the pH value of the reaction end point is 4.5, the main diffraction peak intensities of the goethite and the ammonium jarosite in the filter residue are increased and the full widths at half maximum of the peaks are reduced, which indicates that the pH value of the acid leaching solution is increasedThe crystallization degree of goethite and ammoniojarosite is increased; upon further raising the pH to 5.0, the back-scattering by the amorphous product is enhanced.
FIG. 6 shows an infrared spectrum of the filter residue at different reaction end points pH for example 6 of the present invention. As shown in FIG. 6, 901cm -1 And 794cm -1 Is at-OH characteristic absorption peak, 421cm -1 The position is an Fe-O stretching vibration peak which is caused by alpha-FeOOH; 1107cm -1 The tensile vibration at the position corresponding to the S-O bond is due to NH 4 Fe 3 (SO 4 ) 2 (0H) 6 Caused by SO 2-4; RE-pH5.0-15 deg.C new 1632cm -1 Absorption peak, the peak is H-O-H bending vibration, is Fe (OH) in the filter residue 3 And (4) causing. In combination with the XRD data, it was concluded that the severity of amorphization at RE-pH5.0-15 deg.C was due to the formation of colloidal iron hydroxide which was poorly crystalline.
Figure 7 shows the iron removal rate and magnesium loss rate at different reaction end point pH values for example 6 of the present invention. As shown in fig. 7, the removal rate of iron rapidly increased from 26.42% to 99.37% in the process of increasing the pH value from 3.0 to 4.0 at the end of the reaction, which indicates that the increase in the pH value at the end of the reaction has a promoting effect on the increase in the iron removal efficiency; in the process of raising the pH value from 4.0 to 5.0 at the end of the reaction, the iron removal rate is slowly raised from 99.37% to 99.94%, because a large amount of iron ions in the solution are removed, so that the concentration of the iron ions in the solution is small, and the raising amplitude of the iron ion removal rate is not large when the pH value is raised. The loss rate of magnesium was slowly increased throughout the course of the increase of the pH from 3.0 to 5.0 at the end of the reaction, slowly increasing from 2.09% to 3.81%. The pH value at the end of the reaction is between 3.0 and 5.0, and the increase of the pH value at the end of the reaction can cause the increase of the loss rate of magnesium ions.
The loss rate of magnesium ions is related to the content of magnesium ions in the solution and the adsorption and coprecipitation of magnesium ions by iron precipitates. The pH at which magnesium hydroxide begins to precipitate is 9.28, so hydroxide precipitation is not the primary cause of magnesium ion loss. The amount of co-precipitation loss of magnesium ions is related to the nature of the iron precipitate: less magnesium ions are adsorbed when goethite and jarosite precipitates are formed: colloidal ferric hydroxide is easy to generate along with the increase of the pH value of the reaction end point, and the loss of magnesium ions is increased due to small colloidal ferric hydroxide particles, poor quality and large specific surface area and strong adsorption capacity to the magnesium ions. Therefore, in order to reduce the loss of magnesium ions, the reaction end point pH should be as low as possible without significantly reducing the iron precipitation efficiency.
Figure 8 shows the filtration rate of the suspension of the pickle liquor of example 6 of the invention at different reaction end points pH. As shown in FIG. 8, when the reaction end point pH is in the range of 3.0 to 4.0, the filtration rate of the reaction product gradually decreases from 1.10 ml/min with the increase of the reaction end point pH -1 Reduce to 018 ml/min -1 This is because the filtration rate becomes slower as the precipitation product becomes more and more with the increase of the pH value at the end of the reaction; when the pH value at the end of the reaction was 4.5, the filtration rate of the product rapidly increased to 1.16 ml/min -1 Most of the precipitates generated in the process are goethite and ammoniojarosite with good filtering performance; at a reaction end pH of 5.0, the product filtration rate decreased slightly, which was associated with an increase in the reaction end pH leading to the formation of colloidal ferric hydroxide which was difficult to filter. Fe as the pH at the end of the reaction increases 3+ The tendency to hydrolyze to form ferric hydroxide increases the proportion of colloidal ferric hydroxide in the precipitate, resulting in a slight decrease in the filterability of the product.
Figure 9 shows XRD patterns of the filter residue of the pickle liquor of example 6 of the present invention at different reaction temperatures. As can be seen from fig. 9, as the reaction temperature increased from room temperature to 80 ℃, the intensity of the goethite and jarosite diffraction peaks increased with increasing reaction temperature, and the full width at half maximum of the peaks decreased, and the back scattering caused by the amorphous product gradually decreased. The results show that when ammonia water is used for removing iron, the reaction temperature is increased, the crystallization degree of the generated ammonium jarosite and goethite is gradually increased, and the content of amorphous products is gradually reduced.
FIG. 10 shows the IR spectra of the filter residue of example 6 of the present invention at different reaction temperatures. As shown in FIG. 10, the ammonium jarosite concentration increased with increasing temperature by 107cm -1 The tensile vibration absorption peak at the S-O bond gradually weakens, and the goethite is 901cm -1 And 794cm -1 Characteristic absorption peak of-OH at 440cm -1 Fe-O elongation ofThe shrinkage vibration peak is enhanced along with the temperature rise, which shows that the rising temperature is favorable for dry increase of the content of goethite in filter residue.
Figure 11 shows the iron removal rate and magnesium loss rate at different reaction temperatures for example 6 of the present invention. As can be seen from fig. 11, the iron removal rate was always increased in the course of increasing the reaction temperature from 15 ℃ to 80 ℃, but was increased from 99.37% to 99.97%. This is because the removal rate of iron ions at room temperature is already greater than 99% at a pH of 4.5, resulting in a small concentration of iron ions in the solution, and therefore the increase in removal rate of iron ions at an elevated reaction temperature is small. The loss rate of magnesium also increases all the time in the process of increasing the reaction temperature from 15 ℃ to 80 ℃, and slowly increases from 2.45% to 5.68%. Analysis shows that when ammonia water is used for removing iron from asbestos tailing pickle liquor, the reaction temperature is increased to facilitate the precipitation of iron ions, but the loss of magnesium ions is increased. The reason is that the generation of goethite and ammonium jarosite needs to absorb a large amount of heat, and the increase of the reaction temperature is beneficial to the generation of goethite and ammonium jarosite, so that the iron removal rate is improved.
FIG. 12 shows the filtration rate of the product at different reaction temperatures for example 6 of the present invention. It can be seen that the filtration rate of the reaction product was always slowly increased from room temperature to 1.16 ml/min with the temperature increase in the range of 15 ℃ to 80 ℃ -1 3.70 ml/min when the temperature is raised to 80 DEG C -1 . This is because the crystallization of goethite and jarosite is promoted by increasing the temperature, and the higher the degree of crystallization of the product, the faster the filtration rate.
FIG. 13 shows the iron removal rate and the magnesium loss rate at different reaction times for example 6 of the present invention, from which it can be seen that the iron removal rate slowly increased from 99.47% to 99.97% in the range of 1min to 30 min; after the reaction time is more than 20min, the removal rate of the iron is almost unchanged. And in the process of prolonging the reaction time from 1min to 30min, the loss rate of magnesium is slowly reduced all the time. The reason is that goethite and ammonium jarosite are not completely generated in the early stage of reaction, amorphous precipitate is formed, precipitate particles are small, the specific surface area is large, the adsorption capacity on magnesium ions is strong, and the loss rate of the magnesium ions is high.
FIG. 14 shows the present inventionAs is clear from the fact that the filtration rate of the reaction product was 2.96 ml/min in the reaction time range of 1min to 10min in the different reaction times of example 6, the filtration rate of the reaction product was found to be higher than that of the reaction product in the different reaction times -1 Rising to 3.46 ml.min -1 (ii) a The reaction time is within the range of 10 min-30 min, the filtration speed of the reaction product is 3.46 ml.min -1 Slowly rising to 3.70 ml.min -1 。
It was found by analysis that the crystallinity of goethite and ihleite increased with longer reaction times, so that longer reaction times contributed to increased product filtration rates.
In conclusion, the method for preparing the refined magnesium sulfate solution by removing iron from the asbestos tailing roasting product leachate can not only realize resource utilization of the asbestos tailings, save land resources and protect the environment, but also has simple and convenient operation, stable iron removal efficiency of more than 99 percent and stable magnesium ion loss rate of less than 5 percent.
Although the present invention has been described above in connection with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. The method for preparing magnesium sulfate by removing iron from asbestos tailings is characterized by comprising the following steps:
roasting and activating the asbestos tailings to obtain a roasted and activated product;
placing the roasted and activated product in an acid or salt solution containing sulfate radicals for leaching reaction, and filtering to obtain high-magnesium acidic filtrate;
adding oxidant dropwise into the high-magnesium acidic filtrate while heating and stirring, and mixing Fe in the solution 2+ Conversion to Fe 3+ Then, obtaining a mixed solution;
slowly dropwise adding an iron-removing precipitator into the mixed solution for precipitation reaction, and continuously stirring after dropwise adding the iron-removing precipitator to the end-point pH value of the precipitation reaction to obtain a reaction product, wherein the end-point pH value is 4.0-5.0; and
and filtering the reaction product to obtain filter residue and a magnesium sulfate solution.
2. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the roasting activation temperature is 650-750 ℃, and the roasting time is 30-90 min.
3. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the sulfate-containing acid or salt solution comprises: one or more of a sulfuric acid solution, an ammonium bisulfate solution, and an ammonium sulfate solution.
4. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the liquid-solid ratio of the leaching reaction is 14-20 ml/g, the temperature of the leaching reaction is 15-60 ℃, the time of the leaching reaction is 30-60 min, and the pH value of the leaching reaction is 0.2-1.0.
5. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the temperature of the precipitation reaction is 40-100 ℃, and the time for continuing stirring is 10-30 min.
6. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the method further comprises the following steps:
slowly dripping a neutralizing agent into the mixed solution until the pH value of the mixed solution is 2.0-2.5, and then dripping the iron removal precipitator until the pH value of the mixed solution is 4.0-5.0.
7. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 6, wherein the oxidant comprises hydrogen peroxide, and the mixing ratio of the oxidant to the high-magnesium acidic filtrate is 0.01-0.015 mol: 1L;
the neutralizing agent comprises one or more of magnesium carbonate, basic magnesium carbonate and magnesium hydroxide, and the adding amount of the neutralizing agent is that the pH value of the mixed solution is 2.0-2.5;
the precipitant comprises ammonia water and/or sodium hydroxide, and the addition amount of the precipitant is that the pH value of the mixed solution is 4.0-5.0.
8. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 6, wherein the temperature of the neutralization reaction and the precipitation reaction is 40-100 ℃, and the time for continuing stirring is 10-30 min.
9. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the mineral composition of the filter residue comprises goethite and jarosite or goethite and jarosite.
10. The method for preparing magnesium sulfate by removing iron from asbestos tailings according to claim 1, wherein the loss rate of magnesium ions in the magnesium sulfate solution is below 5%, and the iron removal rate is above 99%.
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| CN115259186B (en) * | 2022-08-24 | 2023-12-26 | 西南科技大学 | Magnesium sulfate solution refined from asbestos tailings and preparation method thereof |
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| CN114873615B (en) | 2023-10-03 |
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