CN108191031B - Sulfur-free arsenical chalcanthite and application thereof in purifying trivalent arsenic wastewater - Google Patents

Sulfur-free arsenical chalcanthite and application thereof in purifying trivalent arsenic wastewater Download PDF

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CN108191031B
CN108191031B CN201810008659.XA CN201810008659A CN108191031B CN 108191031 B CN108191031 B CN 108191031B CN 201810008659 A CN201810008659 A CN 201810008659A CN 108191031 B CN108191031 B CN 108191031B
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trivalent arsenic
trivalent
purifying
wastewater
arsenic
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CN108191031A (en
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李青竹
柴立元
杨锦琴
颜宇琛
胡可人
王庆伟
杨志辉
闵小波
梁彦杰
刘恢
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds
    • C02F1/62—Heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/103—Arsenic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Inorganic Chemistry (AREA)
  • Removal Of Specific Substances (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

The invention relates to a sulfur-free arsenopyrite and application thereof in purifying trivalent arsenic wastewater, wherein the method for purifying the trivalent arsenic wastewater comprises the following steps: simultaneously feeding the trivalent arsenic wastewater and the trivalent iron solution, adjusting the pH value of the mixed solution to 1.41-2.45, stirring at normal temperature, and separating and precipitating to obtain the compound arsenic-free ferric iron phosphate, wherein the used medicines and reagents do not contain sulfate radicals. The precipitate obtained by the method is the vitriol with a chemical formula of Fe6(AsO3)4(HAsO3)(OH)4·4H2And O, the crystal structure is the same as the crystal structure characteristic of the arsenopyrite, belongs to a mineral crystal structure, and can be applied to sulfate radical-free trivalent arsenic wastewater to form a precipitate so as to achieve the purpose of removing trivalent arsenic.

Description

Sulfur-free arsenical chalcanthite and application thereof in purifying trivalent arsenic wastewater
Technical Field
The invention relates to the technical field of environmental engineering, in particular to a sulfur-free arsenopyrite and application thereof in purifying trivalent arsenic wastewater.
Background
With the continuous development of the nonferrous metal smelting industry in China, the discharge amount of wastewater containing trivalent arsenic is larger and larger, but arsenic and arsenic compounds are well-known strong carcinogens, so that the wastewater containing trivalent arsenic needs to be strictly treated before being discharged.
In the prior art, trivalent arsenic is generally removed by a precipitation method. Publication No. CN107010704A discloses a method for treating wastewater containing trivalent arsenic, which comprises reacting wastewater containing trivalent arsenic, ferric iron solution and sulfate solution to generate arsenopyrite crystal, thereby achieving the effect of removing trivalent arsenic, but the method needs two reagents, and has large dosage and more byproducts. Publication No. CN106006754A discloses a method for synthesizing high-purity arsenopyrite by a hydrothermal method, which utilizes ferric sulfate and trivalent arsenic to react at the temperature of 100-.
Therefore, it is meaningful to develop a sulfur-free arsenopyrite for use in the removal of trivalent arsenic, which can be removed under mild reaction conditions without adding sulfate.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a sulfur-free arsenical chalcanthite and application thereof in purifying trivalent arsenic wastewater. The wastewater containing trivalent arsenic is reacted with a ferric iron solution without adding sulfate to prepare the crystal precipitate of the non-sulfur map hydrargillite, thereby removing the trivalent arsenic.
The technical scheme adopted by the invention is as follows:
a method of purifying trivalent arsenic wastewater, comprising: simultaneously feeding the trivalent arsenic wastewater and the trivalent iron solution, adjusting the pH value of the mixed solution to 1.41-2.45, stirring at normal temperature, and separating and precipitating to obtain the compound arsenic-free ferric iron phosphate, wherein the used medicines and reagents do not contain sulfate radicals.
In the technical scheme, all the used medicines and reagents do not contain sulfate radicals, the wastewater containing the trivalent arsenic and the trivalent iron solution are simultaneously fed, fully contacted and mixed, the pH value of the mixed solution is adjusted to be 1.41-2.45, and the mixed solution is stirred and reacted at normal temperature to obtain a precipitate (non-sulfur map hydroarsenical ferroalum), so that the removal of the trivalent arsenic is realized. When the pH value is more than 2.45, amorphous ferric hydroxide is obtained, and no sulfurless figure ferrous arsenicum precipitate is formed; when the pH is less than 1.41, an amorphous solid phase is obtained. The technical scheme has mild reaction conditions, does not need to additionally add sulfate radicals, can also obtain crystal precipitates, thereby removing trivalent arsenic, and is suitable for industrial application and low in cost.
In the technical scheme, the pH value is preferably 1.56-2.08. Under the condition, the yield and the purity of the vitriol can be improved.
In the technical scheme, the molar concentration of the trivalent arsenic in the mixed solution is 0.015 mol/L-0.15 mol/L, preferably 0.15 mol/L, and the higher the concentration is, the more favorable the formation of the crystal of the sulfur-free arsenopyrite is.
In the technical scheme, the molar concentration ratio of trivalent arsenic to trivalent iron in the mixed solution is 0.3-1.5: 1, and preferably 1: 1. The molar ratio of trivalent arsenic to trivalent iron is controlled to prevent excess iron from forming iron hydroxide which carries away arsenic in adsorbed form.
In the technical scheme, the normal temperature is 15-30 ℃, and preferably 25 ℃.
In the technical scheme, the stirring reaction time is 3-10 days, preferably 5 days.
The trivalent arsenic wastewater and the trivalent iron solution react to generate the precipitate of the non-sulfur arsenopyrite hydrate, the reaction temperature and the reaction time have influence on the speed and the purity of the formed crystal, the temperature is preferably 25 ℃ after comprehensive consideration, and the reaction time is preferably 5 days.
In the above technical solution, preferably, the trivalent iron is ferric nitrate, and the trivalent arsenic is sodium arsenite. Because nitrates including ferric nitrate are readily soluble in water, they promote the reaction and have little effect on the formation of the wurtzite crystal. In addition, the vitriol obtained by the invention is a substance obtained by replacing sulfate radicals in vitriol with arsenous acid ions, so that the reaction is more facilitated by using sodium arsenite.
The second purpose of the invention is to provide the sulfur-free arsenopyrite which is the precipitate prepared in the method for purifying the trivalent arsenic wastewater.
The vitriol has a chemical formula of Fe6(AsO3)4(HAsO3)(OH)4·4H2O, its crystal structure and Fe arsenopyrite6(AsO3)4(SO4)(OH)4·4H2The crystal structure characteristics of O are the same.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a sulfur-free map FeAs Fe6(AsO3)4(HAsO3)(OH)4·4H2O is a substance obtained by replacing sulfate radicals in the crystal structure of the arsenopyrite with arsenious acid ions, can be prepared by stirring and reacting ferric iron and a ferric arsenic solution at normal temperature without adding sulfate radicals, has mild reaction conditions, can be applied to sulfate radical-free ferric arsenic wastewater to form sulfur-free arsenopyrite, thereby realizing removal of the ferric arsenic and having very important significance for expanding the environmental application of the arsenopyrite.
Drawings
FIG. 1 is a graph showing the comparison of XRD of the sulfur-free and sulfur-containing hydroxyarsenifedites in example 1 of the present invention;
FIG. 2 is a graph showing the comparison of IR spectra of arsenopyrite without a sulfur map and arsenopyrite with a sulfur map in example 1 of the present invention;
FIG. 3 is a graph showing the comparison of Raman spectra of arsenopyrite without a sulfur map, arsenopyrite with a sulfur map, and scorodite in example 1 of the present invention;
FIG. 4 is an XRD result diagram of the obtained sulfur-free arsenopyrite with pH value of the reaction solution in the range of 1.27-2.45;
FIG. 5 is a microscopic morphology picture of the non-sulfur arsenical hydrate obtained by the reaction solution under different pH values;
FIG. 6 shows the results of the removal rates of arsenic and iron when the pH of the reaction solution is in the range of 1.27 to 2.45 to form the sulfurless arsenopyrite;
FIG. 7 is an XRD result chart of a solid obtained in the reaction solution in which the molar concentration ratio of trivalent arsenic to trivalent iron is in the range of 0.3 to 15.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.
Example 1
The embodiment provides a method for purifying trivalent arsenic wastewater, which comprises the steps of simultaneously feeding and mixing wastewater containing sodium arsenite and ferric nitrate solution, wherein the molar concentrations of Fe (III) and As (III) in the mixed solution are 0.15 mol/L and 0.15 mol/L respectively, adjusting the pH value of the mixed solution to 1.56, reacting for 5 days at 25 ℃ by adopting magnetic stirring, and then carrying out suction filtration and separation on solid and liquid, wherein the used medicines and reagents do not contain sulfate radicals.
The concentrations of As (III) and Fe (III) in the filtrate were measured to calculate the removal rate.
Washing the obtained filter residue with deionized water for 3 times, and drying at 80 ℃. The XRD results of the obtained solid sample are shown in FIG. 1, the infrared spectrum is shown in FIG. 2, and the Raman spectrum is shown in FIG. 3.
The infrared spectrum (fig. 2) shows that the solid contains no sulfate ions, the raman spectrum (fig. 3) shows that the solid contains no pentavalent arsenic but trivalent arsenic, and it can be confirmed from fig. 1 to fig. 3 that this example produces arsenite-substituted sulfate-free hydrargillite having the same crystal structure as the sulfur-containing hydrargillite.
The pH value of the reaction solution is adjusted by nitric acid and sodium hydroxide, when the pH value is adjusted to be within the range of 1.27-2.45, XRD results of the obtained solid are shown in figure 4, the amorphous solid phase is obtained in the solution with the pH value of 1.27, the anhydrous arsenopyrite with a small amount of sulfur-free map is obtained in the solution with the pH value of 2.45, the anhydrous arsenopyrite with the sulfur-free map is obtained in the solution with the pH value of 1.41-2.08, and the micro-morphology of the obtained solid is shown in figure 5.
Further, the removal rates of arsenic and iron in the pH range of 1.27 to 2.45 are shown in FIG. 6. Wherein the removal rate of ferric iron increases with increasing pH, e.g. from 1.27 to 2.45, from 5.1% to 98.26%. The removal rate of the trivalent arsenic is lower when the pH value is less than 1.56, for example, when the pH value is 1.27-1.56, the removal rate of the trivalent arsenic is about 40%; at pH values above 1.56, the removal rate of trivalent arsenic increases with increasing pH, for example, when the pH value increases from 1.62 to 2.08 to 2.45, the removal rate of trivalent arsenic correspondingly increases from 50.2% to 82% to 92%. Although the removal rates of trivalent arsenic and trivalent iron are highest at pH 2.45, the arsenopyrite formed under these conditions contains a large amount of amorphous iron hydroxide and is therefore not suitable as an optimum condition for arsenic removal applications for sulfur-free arsenopyrite.
Adjusting the ratio of the trivalent arsenic to the trivalent iron in the initial reaction solution to be changed from 0.3 to 15, controlling the pH value to be 1.60, confirming that the obtained solid can obtain the arsenopyrite without a sulfur diagram when the ratio of the trivalent arsenic to the trivalent iron is 0.3-1.5 through XRD detection (figure 7), and obtaining the solid which is an amorphous phase when the ratio of the trivalent arsenic to the trivalent iron is more than 1.5.
Controlling the ratio of the trivalent arsenic to the trivalent iron to be 1.0 and the pH value to be 1.60, and adjusting the concentration of the trivalent arsenic in the initial reaction solution to be 1.5 × 10-3mol/L increased to 1.5 × 10-1mol/L, at a trivalent arsenic concentration of less than 1.5 × 10-2No solid is generated at mol/L, which is higher than 1.5 × 10-2At mol/L, no sulfur figure hydroxyarseniflumite is obtained.
Finally, the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (11)

1. A method for purifying trivalent arsenic wastewater, which is characterized by comprising the following steps: simultaneously feeding the trivalent arsenic wastewater and the ferric iron solution, adjusting the pH value of the mixed solution to 1.41-2.45, stirring at normal temperature of 15-30 ℃ for 3-10 days, and separating and precipitating to obtain the sulfur-free arsenopyrite with a chemical formula of Fe6(AsO3)4(HAsO3)(OH)4·4H2O, wherein the drugs and reagents used do not contain sulfate radicals.
2. The method for purifying trivalent arsenic wastewater as claimed in claim 1, wherein the pH value is 1.56-2.08.
3. The method for purifying wastewater containing trivalent arsenic as claimed in claim 1, wherein the molar concentration of trivalent arsenic in the mixed solution is 0.015 mol/L-0.15 mol/L.
4. A method for purifying wastewater containing trivalent arsenic as claimed in claim 3, wherein the molar concentration of trivalent arsenic in the mixed solution is 0.15 mol/L.
5. The method for purifying trivalent arsenic wastewater as claimed in claim 1, wherein the molar concentration ratio of trivalent arsenic to trivalent iron in the mixed solution is 0.3-1.5: 1.
6. The method for purifying trivalent arsenic wastewater as claimed in claim 5, wherein the molar concentration ratio of trivalent arsenic to trivalent iron in the mixed solution is 1: 1.
7. A method for purifying wastewater containing trivalent arsenic as claimed in any one of claims 1 to 6, wherein the normal temperature is 25 ℃.
8. A method for purifying wastewater containing trivalent arsenic as claimed in any one of claims 1 to 6, wherein the stirring time is 5 days.
9. A method for purifying wastewater containing trivalent arsenic as claimed in any one of claims 1 to 6, wherein the trivalent iron is ferric nitrate and the trivalent arsenic is sodium arsenite.
10. The arsenopyrite without sulfur map is the precipitate prepared in the method for purifying trivalent arsenic wastewater according to any one of claims 1 to 9.
11. The charcot-free arsenopyrite, as claimed in claim 10, wherein the formula is Fe6(AsO3)4(HAsO3)(OH)4·4H2O, its crystal structure and Fe arsenopyrite6(AsO3)4(SO4)(OH)4·4H2The crystal structure characteristics of O are the same.
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