CN114920275B - Recycling recovery method for forming specific minerals by directional induction of heavy metals - Google Patents
Recycling recovery method for forming specific minerals by directional induction of heavy metals Download PDFInfo
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- CN114920275B CN114920275B CN202210689918.6A CN202210689918A CN114920275B CN 114920275 B CN114920275 B CN 114920275B CN 202210689918 A CN202210689918 A CN 202210689918A CN 114920275 B CN114920275 B CN 114920275B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/78—Compounds containing aluminium and two or more other elements, with the exception of oxygen and hydrogen
- C01F7/784—Layered double hydroxide, e.g. comprising nitrate, sulfate or carbonate ions as intercalating anions
- C01F7/785—Hydrotalcite
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G11/00—Compounds of cadmium
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- C—CHEMISTRY; METALLURGY
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- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G3/00—Compounds of copper
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- C01G9/00—Compounds of zinc
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- 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
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Abstract
The invention belongs to the technical field of heavy metal pollutant treatment, and discloses a recycling recovery method for forming specific minerals by directional induction of heavy metals, which comprises the steps of adding high-valence metal cations into a water body containing heavy metal ions, and regulating pH to weak acidity; adding mineral seed crystal particles into a water body containing heavy metals, and adjusting pH to cause metal ions to precipitate to obtain a precipitate; washing the precipitate, and washing away the surface adsorption state or adhesion state heavy metal ions; finally, the obtained solid is dried to obtain the target mineral material or chemical reagent. The mineral seed crystal added in the invention can play a remarkable structural induction effect, and can selectively change the final product of heavy metal ions, namely, the mineral seed crystal with different structures can selectively induce the heavy metal ions to form a crystallization product similar to the seed crystal structure. The treatment method can simultaneously meet the requirements of high-efficiency removal of heavy metal ions and easy recovery and applicability of products.
Description
Technical Field
The invention belongs to the technical field of heavy metal pollutant treatment, and discloses a recycling recovery method for forming specific minerals by directional induction of heavy metals.
Background
The environmental and human health problems caused by heavy metal pollution are increasingly aggravated, and have received widespread global attention. The heavy metal pollutants comprise copper, cadmium, lead, zinc, chromium, nickel, mercury and the like, and have carcinogenic, teratogenic or other toxic effects and the like, and are harmful to the environment, animal and plant production and human health. At present, a plurality of heavy metal pollution treatment technologies aiming at soil, natural water, wastewater and other mediums, such as passivation, immobilization/stabilization, electrodynamic technology and the like aiming at soil heavy metal pollution, are developed; aiming at the techniques of water body adsorption, flocculation precipitation and the like. These techniques can well passivate or remove heavy metal ions from a body of water, but also have significant drawbacks. For example, the soil heavy metal passivation technology can only realize the reduction of heavy metal migration activity and bioavailability in a short period, and the heavy metal can be activated again in a long period. And technologies such as electrodynamics, adsorption and flocculation precipitation can remove heavy metal ions from a water body, but the solid waste generated in the treatment process still needs to be subjected to harmless treatment, and the subsequent treatment has certain difficulty and is complicated.
Heavy metals, although a type of hazardous substances, are also useful resources. Then, whether there is a simple treatment method that can solve the permanent remediation of heavy metal pollution of soil, and can also remove heavy metal ions in water without worrying about the safe disposal of subsequent solid products? The prior art can not realize the high-efficiency removal of heavy metal ions at the same time, and the product is easy to recycle and applicable.
Disclosure of Invention
The invention aims to provide a recycling recovery method for forming specific minerals by directional induction of heavy metals, which solves the problems that high-efficiency removal of heavy metal ions cannot be realized at the same time at present, and products are easy to recover and applicable.
The invention is realized by the following technical scheme:
a recycling recovery method for directional induction of heavy metals to form specific minerals comprises the following steps:
step one, adding positive trivalent and above valence metal cations into a solution containing heavy metal ions, and then adjusting the pH value to 4-5 to obtain a mixed solution;
step two, adding mineral seed crystal particles into the mixed solution, and simultaneously adjusting the acid-base property of the mixed solution to be more than or equal to 5 in the target reaction pH value, and coprecipitating heavy metal ions and metal cations in positive trivalent or above valence states to obtain a precipitate;
step three, washing the precipitate, and washing heavy metal ions on the surface of the precipitate to obtain a solid product;
step four: and drying the solid product to obtain the target mineral material or chemical reagent.
Further, the mineral seeds include metal oxide/hydroxide minerals, basic anion salt minerals, and other minerals having similar or identical crystal or surface structure to the target product.
Further, the positive trivalent and above valence metal cations are one or more of aluminum, iron, chromium, manganese, titanium and rare earth ions.
Further, the drying mode adopts drying, freeze drying or natural drying; the temperature is not more than 150 ℃.
Further, the heavy metal ions are zinc ions, cadmium ions, copper ions, nickel ions or cobalt ions.
Further, the reaction time of the coprecipitation is 2 hours or more.
Further, the molar ratio of the heavy metal ion to the metal cation in the positive trivalent or higher valence state is (1-5): 1.
compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a recycling recovery method for forming specific minerals by directional induction of heavy metals, which fully utilizes the theory of crystal seed induction ore formation in mineralogy, realizes the directional induction ore formation of heavy metal ions by utilizing the structural specificity of the mineral crystal seeds, obtains the products which are minerals similar to the mineral crystal seed structure, and can be determined by the types of the mineral crystal seeds, thereby realizing the productization of the heavy metal ions in polluted media and the diversification of the products, thereby being hopeful to promote the production activity of recovering the heavy metal ions from the media such as soil, natural water, wastewater and the like as valuable functional minerals or chemical reagents and providing valuable adsorbents, catalysts, electrode materials, barrier materials, chemical raw materials and the like for markets. The method for recycling heavy metals can directly obtain valuable materials or chemical reagents which can be directly used after treatment, thereby realizing recycling and valuable recycling of heavy metal wastes. That is, the treatment method simultaneously satisfies the high-efficiency removal of heavy metal ions, and the product is easy to recycle and applicable. Low cost, simple and efficient treatment, low energy consumption, short preparation period, suitability for large-scale preparation and wide application prospect.
Drawings
FIG. 1 is a graph showing the kinetics of removal of zinc ions over time for each system at a molar ratio of Zn to Al of 5 in example 1;
FIG. 2 is a graph showing the kinetics of removal of zinc ions over time for each system at a molar ratio of Zn to Al of 3 in example 1;
FIG. 3 is a graph showing the kinetics of removal of zinc ions over time for each system at a molar ratio of Zn to Al of 1 in example 1;
FIG. 4 is a graph showing the instantaneous removal rate of Zn ions for different systems in experiments with a molar ratio of Zn to Al of 3 in example 1;
FIG. 5 is an X-ray diffraction pattern (XRD) of the products of the respective systems (hydrotalcite adsorbing system LDH-Zn, co-precipitating system Zn-Al, hydrotalcite inducing system LDH-Zn-Al) in example 1;
FIG. 6 is a graph showing the results of elemental surface scanning and EDX spectroscopy analysis of the products of hydrotalcite-induced system LDH-Zn-Al, co-precipitation system Zn-Al, hydrotalcite-induced system LDH-Zn-Al in experiment with Zn and Al molar ratio of 3 in example 1. Wherein, figure a represents the distribution and relative content of Mg, al and Zn elements in a hydrotalcite zinc ion adsorption system (LDH-Zn) product; panel b represents the distribution and relative content of Al, zn elements in the Zn and Al homogeneous coprecipitation system (Zn-Al) product; FIG. c represents the distribution and relative content of Mg, al, zn elements in hydrotalcite seed crystal induced zinc ion mineralization system (LDH-Zn-Al) products;
FIG. 7 is a graph showing the efficiency of cadmium ion removal by the hydrotalcite seed method of example 2 of the present invention;
FIG. 8 is an XRD pattern of the copper chloride precipitation system Cu-Cl, the co-precipitation system Cu-Al, and the hydrotalcite seed induction system LDH-Cu-Al products of example 3;
FIG. 9 is an XRD pattern of the copper chloride precipitation system Cu-Cl, the co-precipitation system Cu-Al, and the product of the parachlorocopper seed induction system in example 4;
fig. 10 is a simplified schematic diagram of the comparison of the results of embodiments 3 and 4, showing that in the Cu and Al ion mixed solution, the final product is layered double hydroxide mineral (CuAl-LDH) with the addition of hydrotalcite seed crystal, and the final product is basic anion salt mineral with the addition of parachlorocopper seed crystal.
Detailed Description
The invention discloses a heavy metal recycling recovery method for forming specific minerals by directional induction of heavy metals, which comprises the following steps:
1) Adjusting the pH value of the water body or soil solution containing heavy metal ions to be between 4 and 5 so that the seed crystal is not dissolved in a large amount;
2) Adding fine specific mineral seed crystal particles into a water body or soil solution containing heavy metals according to a proportion (such as adding seed crystals according to a proportion of 1g mineral seed crystal/L water body or other proportions), then adding high-valence metal cations into the water body, and adjusting pH to a target reaction pH value (more than or equal to 5) to enable heavy metal ions and the added high-valence metal cations to precipitate together; the high valence metal cations may also be added first, followed by mineral seed particles, and finally the pH adjusted to the target reaction pH. It should be noted that the setting of the reaction target pH needs to be determined according to the precipitation pH of the metal ions in the mixed solution, and only the metal ions in the solution need to be ensured to be capable of undergoing a precipitation reaction.
3) The above reaction may be carried out for 0 to 24 hours or even longer. The longer the reaction time, the better the crystallinity of the product obtained. After the reaction is finished, washing the mixture obtained in the second step by water to wash away the surface adsorption state or attachment state heavy metal ions;
4) Finally, the obtained solid is dried to obtain the specific mineral material or chemical reagent.
The heavy metal ions are zinc ions, cadmium ions, copper ions, nickel ions or cobalt ions. Of course not limited to these.
The mineral seed crystal comprises metal oxygen/hydroxide mineral, basic anion salt mineral and other minerals with similar or same crystal or surface structure with the target product.
The positive trivalent and above valence metal cations are one or more of aluminum, iron, chromium, manganese, titanium and rare earth ions.
The drying mode adopts drying, freeze drying or natural drying; the temperature is not more than 150 ℃.
The invention is further illustrated by the following examples:
example 1:
the method for forming hydrotalcite-like minerals by directional induction of zinc ions by layered double metal mineral hydrotalcite seed crystals specifically comprises the following steps:
1) Adding positive trivalent aluminum ions into a water body containing zinc ions, and then adjusting the pH value of the mixed solution to 5 to obtain 1L of mixed metal solution containing zinc ions and aluminum ions with the pH value of 5, wherein the molar ratio of Zn ions to Al ions is 3:1;
under magnetic or mechanical stirring, 1g of hydrotalcite seed (i.e., layered double hydroxide mineral composed of magnesium and aluminum elements, mgAl-LDH, hereinafter collectively abbreviated as LDH) mineral powder was added, followed by controlling the reaction pH to be constant at 7 (i.e., the target reaction pH value was 7) using a pH automatic control liquid feeder. It should be noted that the setting of the reaction target pH needs to be determined according to the precipitation pH of the metal ions in the mixed solution, and only the metal ions in the solution need to be ensured to be capable of undergoing a precipitation reaction. For example, zinc and aluminum ions in this case can also be reacted under alkaline conditions at a pH greater than 7.
2) The reaction was continued for 4 hours with stirring, followed by centrifugation to give a solid product.
3) And washing the solid product to wash away the surface adsorption state or attachment state heavy metal ions. Subsequently, the solid was dried at 80 ℃ to obtain the target mineral.
And carrying out relevant characterization on the solid obtained after drying, and carrying out identification analysis on the product. The hydrotalcite seed induction system is simply referred to as an LDH-Zn-Al system, and the system product is referred to as an "LDH-Zn-Al system product".
Meanwhile, a comparative example was performed, specifically as follows:
comparative example 1 was a homogeneous coprecipitation system of Zn and Al ions, abbreviated as Zn-Al system, formed without adding hydrotalcite mineral powder on the basis of example 1, the system product being referred to as "Zn-Al system product";
comparative example 2 is a hydrotalcite seed crystal zinc ion adsorption system (no aluminum ions in solution) formed without adding aluminum ions on the basis of example 1, and is abbreviated as an LDH-Zn system, and the system product is referred to as an "LDH-Zn system product".
In order to investigate the influence of the addition amount of Al ions in the mixed solution on the removal of heavy metal Zn ions, the content of Zn ions was fixed on the basis of example 1, the molar ratio of Zn to Al was adjusted to 5:1 and 1:1 by changing the addition amount of aluminum ions, and two experiments were conducted to investigate the influence of the addition amounts of different Al ions.
For example 1 of the present invention and comparative examples 1-2, the course of the change in the Zn ion removal efficiency with the reaction time was followed to obtain Zn ion removal kinetics curves for different systems (i.e., LDH-Zn-Al, zn-Al and LDH-Zn systems) at different Zn and Al molar ratios, as shown in FIGS. 1-3. In the figure, LDH-Zn-Al represents a hydrotalcite seed crystal induced zinc ion ore formation system; zn-Al represents a homogeneous coprecipitation system of Zn and Al ions; LDH-Zn represents a hydrotalcite seed crystal zinc ion adsorption system (no aluminum ions in solution); zn-Al+LDH-Zn represents a simple addition of two systems, homogeneous coprecipitation and hydrotalcite adsorption.
The molar ratio of Zn to Al in FIG. 1 was 5:1, the molar ratio of Zn to Al in FIG. 2 was 3:1, and the molar ratio of Zn to Al in FIG. 3 was 1:1.
The zinc ion removal experimental results (figures 1-3) show that the hydrotalcite seed induction can significantly improve the zinc ion removal rate, and in all experiments with different Zn and Al ratios, the hydrotalcite induction (namely LDH-Zn-Al system) has the best Zn ion removal efficiency. In addition, under the experimental system with the zinc-aluminum molar ratio of 3:1 and 1:1, the zinc ion removal effect of the induction system (LDH-Zn-Al) is best and is higher than the sum of the zinc ion removal rates of the adsorption system (LDH-Zn) and the homogeneous coprecipitation system (Zn-Al), so that the effect of 1+1 is more than 2. Overall, the addition of aluminum ions significantly improves the zinc ion removal effect, regardless of the zinc to aluminum molar ratio, which is more pronounced under induction by hydrotalcite seeds.
Furthermore, taking the experiment of 3:1 mole ratio of Zn to Al as an example, from the transient Zn ion removal rate curve (FIG. 4) of different systems, the zinc ion removal rate of the induced system (LDH-Zn-Al) is far higher than that of the adsorption system (LDH-Zn) and the homogeneous coprecipitation system (Zn-Al), and even higher than the sum of the removal rates of the two systems (namely Zn-Al+LDH-Zn in the figure). The numerical value (table 1) shows that the zinc ion removal rate of the induction system LDH-Zn-Al is 2.5-5.9 times that of the adsorption system LDH-Zn, 1.9-2.7 times that of the homogeneous coprecipitation system Zn-Al, and 1.3-1.6 times that of the sum of the Zn-Al and LDH-Zn, and the effect that the hydrotalcite seed crystal induction system can achieve the effect that the Zn ion removal rate and the removal rate are both 1+1 and more than 2 is achieved.
Fig. 4 is a graph of instantaneous removal rates of Zn ions of different systems in a 3:1 experiment of molar ratio of Zn to Al, namely, graphs of removal rates of zinc ions of LDH-Zn, zn-Al, LDH-Zn-Al and Zn-al+ldh-Zn systems over time, and the results show that the removal rate of hydrotalcite seed crystal induced zinc ion mineralization system is the fastest.
TABLE 1 ratio of heavy metal Zn ion removal Rate from hydrotalcite seed Induction System to other systems
Note that: in Table 1, (LDH-Zn-Al/LDH-Zn represents the ratio of hydrotalcite seed induction system (LDH-Zn-Al) to hydrotalcite adsorption Zn ion system (LDH-Zn) Zn ion removal rate, LDH-Zn-Al/Zn-Al represents the ratio of hydrotalcite seed induction system to Zn ion and aluminum ion homogeneous coprecipitation system (Zn-Al), LDH-Zn-Al/(LDH-Zn+Zn-Al) represents the ratio of hydrotalcite seed induction system to Zn-Al homogeneous coprecipitation system and LDH-Zn hydrotalcite adsorption system addition.
XRD characterization was performed on the target products produced in example 1 and the corresponding control examples, resulting in XRD characterization results as shown in fig. 5. In the figures, PDF#52-1082 and PDF#22-0700 correspond to characteristic XRD lines of basic zinc carbonate hydrate and hydrotalcite, respectively, and are used for comparison to reveal the phases of the products. LDH represents hydrotalcite mineral seeds used in the experiments, which are consistent with XRD diffraction peaks of PDF #22-0700, indicating that the seeds are pure hydrotalcite minerals. LDH-Zn is the XRD spectrum of the adsorption system product, and is consistent with the LDH spectrum, and the spectrum is derived from the added hydrotalcite seed crystal. LDH-Zn-Al and Zn-Al represent the products of the seed induction system and the homogeneous coprecipitation system, respectively, from which it is clear that the products of the two systems are different. The homogeneous coprecipitation (Zn-Al) system product is a mixture of layered double metal hydroxide and basic zinc carbonate hydrate, whereas only the layered double metal mineral phase is present in the LDH-Zn-Al system product. The above results indicate that hydrotalcite seeds can induce zinc ions and aluminum ions to form layered double hydroxide minerals (ZnAl-LDH).
The results of the determination of the final removal rates of aluminum ions and zinc ions in the experiments described in FIGS. 1-3 show that in hydrotalcite seed crystal induction systems (LDH-Zn-Al) with a molar ratio of zinc to aluminum of > 3, the molar ratio of zinc and aluminum ions removed from the solution is about 3, indicating that hydrotalcite seeds may be able to induce the removal of zinc and aluminum ions in proportion. And this ratio (i.e., number 3) is close to the ratio of the structural constituent elements magnesium and aluminum elements of the hydrotalcite seed crystal (the hydrotalcite seed crystal is a layered double hydroxide mineral MgAl-LDH composed of magnesium and aluminum elements, in which the molar ratio of magnesium and aluminum is about 3). Thus, hydrotalcite seeds are likely to induce the zinc and aluminium in solution to form layered double hydroxide minerals (i.e. ZnAl-LDH) in proportions which are related to the structural composition of the added hydrotalcite seeds.
To further confirm this hypothesis, elemental surface scanning and elemental content EDX analysis were performed using a transmission electron microscope to determine the relative amounts and relative distribution of zinc and aluminum, taking the respective system products with a Zn to Al molar ratio of 3:1 as an example. The transmission electron microscope element surface scan and EDX element relative content analysis of each system product as shown in FIG. 6, the left graph represents the transmission electron microscope element surface scan selected area, and the right graph represents element distribution and relative content.
FIG. 6a is a graph of the scanning of the elemental surface and the relative content of EDX elements of a comparative example 2, i.e., a hydrotalcite seed crystal adsorbed zinc ion (LDH-Zn) system product. The selected area is scanned by the elements of the transmission electron microscope, the distribution condition of the elements of the selected area and the relative content of the elements of the selected area are respectively arranged from left to right. As shown in fig. 6a, the product contains three elements of Mg, al, and Zn, wherein Mg and Al are structural constituent elements of the hydrotalcite seed crystal, and the content of Zn is derived from the content adsorbed by the hydrotalcite seed crystal. From the figure, zn elements are uniformly distributed along with Mg and Al elements, namely adsorbed Zn elements are relatively uniformly covered on the surface of hydrotalcite seed crystals. Further, it was found that the molar ratio of structural Mg to Al in the hydrotalcite seed crystal added was 3.27.
FIG. 6b is a graph of the scanning of the elemental surface and the analysis of the relative content of EDX elements by a transmission electron microscope for a comparative example 1, i.e., a Zn and Al ion homogeneous co-precipitation system (Zn-Al) product. The selected area is scanned by the elements of the transmission electron microscope, the distribution condition of the elements of the selected area and the relative content of the elements of the selected area are respectively arranged from left to right. As shown in FIG. 6a, the product contains Zn and Al elements, both of which are derived from homogeneous coprecipitation, and Zn and Al elements are relatively uniformly distributed. The relative removal ratio of Zn and Al in the homogeneous system solution can be obtained from the molar ratio of the two elements in the product. As can be seen in FIG. 6b, the molar ratio of Zn to Al in the product was 1.67, i.e. Zn and Al in the solution were removed approximately in a ratio of 1.67. The molar ratio of Zn to Al added in the experiment is 3 and is far higher than 1.67 in the product, which indicates that aluminum ions with lower or more Zn ions are removed by precipitation in a homogeneous coprecipitation system. In contrast, the Zn removal efficiency in the homogeneous coprecipitation system is not high from the Zn removal kinetics graphs 1 to 3.
FIG. 6c is a graph of the transmission electron microscopy elemental surface scan and EDX elemental relative content analysis of the product formed by the hydrotalcite seed induced zinc ion mineralization system (LDH-Zn-Al) of example 1 of the present invention. The selected area is scanned by the elements of the transmission electron microscope, the distribution condition of the elements of the selected area and the relative content of the elements of the selected area are respectively arranged from left to right. As shown in FIG. 6c, the product contains three elements of Mg, zn and Al and is relatively uniformly distributed, and the three elements are derived from hydrotalcite seed crystals and newly generated products of the system. And determining the molar ratio of Mg and Al and the molar ratio of Zn and Al in the product to obtain the relative removal ratio of Zn and Al in the homogeneous system solution. As can be seen in fig. 6c, the atomic percent of Mg in the product was 66.00% while Mg originated from hydrotalcite seeds. As is clear from comparative example 2 (fig. 6 a), the molar ratio of Mg to Al in the hydrotalcite seed crystal was 3.27, and thus the percentage of Al in the hydrotalcite seed crystal was calculated to be 66.00%/3.27=20.18%. Further, the percentage content of Al element in the new product (ZnAl-LDH) formed by Zn and Al ions in solution in the LDH-Zn-Al system can be calculated to be 23.35% -20.18% =3.17%. Thus, it was obtained that the molar ratio of Zn and Al in the new product (ZnAl-LDH) was 10.05%/3.17% = 3.17, i.e. Zn and Al in the solution were removed approximately in a ratio of 3.17, which is close to the molar ratio of Mg and Al in the added hydrotalcite seeds (3.27).
In conclusion, the results of the element scanning of the transmission electron microscope and the EDX energy spectrum analysis show that the hydrotalcite seed crystal can directionally induce bivalent (Zn) 2+ ) And trivalent metal ions (Al 3+ ) Hydrotalcite-like compounds are formed in a proportion which is equal to the proportion of divalent (Mg 2 + ) And trivalent metal ions (Al 3+ ) Is close to the molar ratio. The results prove that the structural element composition ratio of the hydrotalcite seed crystal has obvious induction effect on the element composition ratio of the target product, and the hydrotalcite seed crystal can indeed induce the selective formation of the hydrotalcite-like mineral with specific composition of heavy metal ions.
Example 2
The method for directionally inducing the cadmium ions to be removed from the solution by the hydrotalcite seed crystal specifically comprises the following steps:
1) Adding aluminum ions into a water body containing cadmium ions to obtain 1L of mixed metal solution containing the cadmium ions and the aluminum ions, wherein the pH value of the mixed metal solution is 5, and the adding amount molar ratio of Cd to Al is 3:1;
under magnetic or mechanical stirring, 1g of hydrotalcite mineral powder was added, followed by controlling the reaction pH to be constant at 7 using a pH automatic control liquid feeder. This system is simply referred to as LDH-Cd-Al system.
2) The reaction was continued for 4 hours with stirring, followed by centrifugation to give a solid product. And washing the solid product to wash away the surface adsorption state or attachment state heavy metal ions. Subsequently, the solid was dried at 80 ℃ to obtain the target product.
Meanwhile, a comparative example was performed, specifically as follows:
comparative example 3 was a homogeneous coprecipitation system of Cd and Al ions (Cd-Al) formed without adding hydrotalcite mineral powder on the basis of example 2;
comparative example 4 was a hydrotalcite seed crystal Cd ion adsorption system (LDH-Cd, no aluminum ion in solution) formed without adding aluminum ion on the basis of example 2.
In example 2 and comparative examples 3 to 4 of the present invention, the course of the change in the Cd ion removal efficiency with the reaction time was followed and measured to obtain the kinetics of Cd ion removal at different times, as shown in FIG. 7. In the figure, LDH-Cd-Al represents a hydrotalcite seed crystal induced Cd ion system; cd-Al represents a homogeneous coprecipitation system of Cd and Al ions; LDH-Cd stands for hydrotalcite seed crystal Cd ion adsorption system (no aluminum ions in solution); cd-al+ldh-Cd represents a simple addition of both homogeneous co-precipitation and hydrotalcite adsorption systems.
The experimental result of removing the Cd ions also shows that the removing efficiency of the heavy metal Cd ions is obviously improved under the induction of the hydrotalcite seed crystal (figure 7), which shows that the hydrotalcite seed crystal induction method is also applicable to other heavy metal ions.
Example 3
The method for forming hydrotalcite-like minerals by directionally inducing copper ions through hydrotalcite seed crystals specifically comprises the following steps:
adding aluminum ions into a water body containing copper ions to obtain 1L of mixed solution of copper ions (copper chloride is adopted) (1.0 mmol/L) and aluminum ions (aluminum chloride is adopted) with the pH value of 4.5, wherein the molar ratio of copper to aluminum ions is 2:1.
1g of hydrotalcite seed crystal was added under magnetic stirring, and the pH of the solution was controlled to be constant at 5 or 7, that is, the reaction pH was 5 or 7, using a pH automatic liquid feeder. This system is simply referred to as LDH-Cu-Al system.
The reaction was continued for 2 hours with stirring, followed by centrifugation to give a solid product.
And washing the solid product to wash away the surface adsorption state or attachment state heavy metal ions. Subsequently, the solid was dried at 80 ℃ to obtain the target product.
And carrying out relevant characterization on the target product, and carrying out identification analysis on the product.
Meanwhile, a comparative example was performed, specifically as follows:
comparative example 5 was a system in which a homogeneous coprecipitation of Cu and Al ions (cu—al) was formed without adding hydrotalcite mineral powder based on example 3;
comparative example 6 was a composition obtained by adding no aluminum ion to the composition of example 3And hydrotalcite seeds to form Cu and Cl ion systems (cu—cl). As the chemical reagent used in example 3 was CuCl 2 Thus, a Cu-Cl control was set to eliminate the influence of the reagent itself.
The XRD characterization results of the products of the systems are shown in figure 8, and PDF#22-0700 and PDF#86-1391 respectively correspond to the characteristic XRD spectral lines of the parachlorocopper in hydrotalcite and basic anion salt minerals and are used for comparing and revealing the phases of the products. Cu-Cl-pH 5 represents a solid product obtained by adding aluminum ions to a copper chloride solution, cu-Al-pH 5 represents a product of a homogeneous coprecipitation system after adding aluminum ions to the copper chloride solution, and LDH-Cu-Al-pH 5 and LDH-Cu-Al-pH 7 represent products obtained by reacting hydrotalcite seed crystal induction systems at pH 5 and 7, respectively. The results show that the Cu-Cl system product is the parachlorocopper ore, the Cu-Al system product is the mixture of layered double metal hydroxide and parachlorocopper ore, and the LDH-Cu-Al system product is the layered double metal hydroxide mineral. The above results also indicate that hydrotalcite seeds can induce copper ions and aluminum ions to form layered double hydroxide minerals (CuAl-LDH), i.e. hydrotalcite seed induction systems are equally applicable to other heavy metal ions.
Example 4
The method for directionally inducing copper ions to form basic anion salt mineral by using the parachlorocopper seed crystal specifically comprises the following steps:
adding aluminum ions into a water body containing copper ions to obtain 1L of mixed solution of copper ions (copper chloride is adopted) (1.0 mmol/L) and aluminum ions (aluminum chloride is adopted) with the pH value of 4.5, wherein the molar ratio of copper to aluminum ions is 2:1.
Under magnetic stirring, 1g of parachlorocopper seed crystal was added, and the pH of the solution was controlled to be constant at 5 using a pH automatic liquid feeder. This system is simply referred to as the parachlorocopper induction system.
The reaction was continued for 2 hours with stirring, followed by centrifugation to give a solid product.
And washing the solid product to wash away the surface adsorption state or attachment state heavy metal ions. Subsequently, the solid was dried at 80 ℃ to obtain the target product.
And carrying out relevant characterization on the target product, and carrying out identification analysis on the product.
Meanwhile, a comparative example was performed, specifically as follows:
comparative example 7 was a copper-mineral powder without adding any secondary chalcopyrite to the base of example 4, to form a Cu and Al ion homogeneous coprecipitation system (Cu-Al);
comparative example 8 was a Cu and Cl ion system (Cu-Cl) formed without adding aluminum ions and hydrotalcite seeds on the basis of example 4. As the chemical reagent used in example 3 was CuCl 2 Thus, a Cu-Cl control was set to eliminate the influence of the reagent itself.
The XRD characterization results of the products of the systems are shown in figure 9, and PDF#22-0700 and PDF#86-1391 respectively correspond to the characteristic XRD spectral lines of the parachlorocopper in hydrotalcite and basic anion salt minerals and are used for comparing and revealing the phases of the products. Cu-Cl-pH 5 represents a solid product obtained by copper chloride at pH 5, cu-Al-pH 5 represents a product of a homogeneous coprecipitation system after aluminum ions are added to a copper chloride solution, and parachlorocopper ore induction-pH 5 represents a product obtained by reacting a parachlorocopper ore seed crystal induction system at pH 5. The result shows that the Cu-Cl system product is the secondary chalcopyrite, the Cu-Al system product is the mixture of layered double hydroxide and the secondary chalcopyrite, and the secondary chalcopyrite induction system product is the secondary chalcopyrite. The above results demonstrate that even in a mixed solution of zinc and aluminum ions, the parachlorocopper seed can induce copper ions to form basic anion salt minerals without generating layered double hydroxide minerals.
The results of comparative examples 3 and 4 show that the final formation of crystalline product of heavy metal ions in solution is affected by the structure of the added mineral seed. In the Cu and Al ion mixed solution, the final product is layered double metal hydroxide mineral (CuAl-LDH) when hydrotalcite seed crystal is added, and the final product is basic anion salt mineral (shown in figure 10) when parachlorocopper seed crystal is added, which shows that the mineral seed crystal has structure induction effect on the crystallization of heavy metal ions.
By using the technical scheme of the invention or under the inspired by the technical scheme of the invention, a similar technical scheme is designed by a person skilled in the art, so that the technical effects are achieved, and the technical effects fall into the protection scope of the invention.
Claims (4)
1. The recycling recovery method for forming specific minerals by directional induction of heavy metals is characterized by comprising the following steps of:
step one, adding positive trivalent and above valence metal cations into a solution containing heavy metal ions, and then adjusting the pH value to 4-5 to obtain a mixed solution;
step two, adding mineral seed crystal particles into the mixed solution, and simultaneously adjusting the acid-base property of the mixed solution to be more than or equal to 5 in the target reaction pH value, and coprecipitating heavy metal ions and metal cations in positive trivalent or above valence states to obtain a precipitate;
step three, washing the precipitate, and washing heavy metal ions on the surface of the precipitate to obtain a solid product;
step four, drying the solid product to obtain a target mineral material or chemical reagent;
the mineral seed crystal comprises metal oxygen/hydroxide mineral and basic anion salt mineral;
the positive trivalent and above valence metal cations are one or more of aluminum, iron, chromium, manganese, titanium and rare earth ions;
the molar ratio of heavy metal ions to metal cations in positive trivalent or higher valence is (1-5): 1.
2. the recycling method for forming specific minerals by directional induction of heavy metals according to claim 1, wherein the drying mode is drying, freeze drying or natural drying; the temperature is not more than 150 ℃.
3. The recycling method for forming specific minerals by directional induction of heavy metals according to claim 1, wherein the heavy metal ions are zinc ions, cadmium ions, copper ions, nickel ions or cobalt ions.
4. The recycling method for forming specific minerals by directional induction of heavy metals according to claim 1, wherein the reaction time of coprecipitation is more than 2 hours.
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| CN107849640A (en) * | 2015-04-15 | 2018-03-27 | 联邦科学和工业研究组织 | It is optionally sequestered element or article of interest in aqueous streams |
| CN111498921A (en) * | 2020-04-15 | 2020-08-07 | 北京化工大学 | Composite material and method for removing pollutants in polluted water |
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