CN111547917A - Method for treating waste water recovered from spent catalyst noble metal - Google Patents
Method for treating waste water recovered from spent catalyst noble metal Download PDFInfo
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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
- C02F9/00—Multistage treatment of water, waste water or sewage
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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
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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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
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/08—Thin film evaporation
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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
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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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
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
Abstract
The invention relates to a method for treating waste water from the recovery of noble metals from spent catalysts, which comprises the following steps: treating wastewater with different pH values by adopting a membrane distillation process, forming hydroxide colloid by utilizing the transformation of coexisting metal ion forms in the wastewater, and removing soluble Silicon (SiO) in the wastewater through the interaction of the positively charged colloid and the negatively charged silicate in the wastewater2) Further reducing membrane pollution, obtaining high-quality hydrochloric acid HCl and high-quality wastewater with low conductivity, and greatly reducing the volume of the wastewater. The method can not only recover resources from the waste water recovered from the noble metal of the spent catalyst, but also greatly reduce the volume of the waste water, further realize the near zero discharge of the waste water, and economically and effectively treat the strong acid or strong alkali high-salinity waste water generated by the recovery of the noble metal of the spent catalyst.
Description
Technical Field
The invention belongs to the field of high-salinity wastewater treatment, and particularly relates to a method for treating waste water recovered from spent catalyst noble metals.
Background
Noble metals such as Platinum Group Metals (PGMs) including platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir), ruthenium (Ru), rhodium (Rh) are widely used in the industrial field as an active component of catalysts due to their superior catalytic properties, chemical inertness, corrosion resistance, thermoelectric stability, etc. PGMs are also known as "industrial vitamins". In different types of catalysts, the content of noble metals is between 0.2% and 100%. The noble metal is used in the fields of electrons and catalysts in the largest amount, and accounts for more than 90% of the total noble metal. 65% palladium, 45% platinum and 84% rhodium are reported for use in catalytic converters.
However, the reserves of PGMs known globally are only 66000 tons and the content of PGMs in the earth's crust is very low, typically 5 × 10 platinum-6Percent, the content of palladium, rhodium, iridium and osmium is 1 × 10-6% ruthenium content 0.1 × 10-6%, and the distribution is extremely unbalanced. 98.5% of PGMs are distributed in south africa, russia, zaya and the united states. Since 2009, China has been the largest platinum group metal consumer nations all the time, but the platinum group metal resources in China are seriously deficient, and a large amount of imports are needed to meet the demand. The platinum group metals in China are proved to have small reserves, small scale and low grade, and are only 350 tons, which accounts for 0.6 percent of the total reserves in the world. Mainly distributed in Jinchuan, Yunnan Jinbaoshan and Yangxuan willow plateau. The Jinchuan company in China can produce 3500 kg of platinum group metal (yield 1 in Asia), 30 tons of gold and 600 tons of silver every year, and the total demand of platinum and palladium in China exceeds 141 tons every year. It can be seen that the production quantity is far from the demand quantity. Therefore, it is necessary to recover precious metals from waste products such as spent catalysts to satisfy the sustainable development of precious metals. According to the data of the national mineral information center, about 30% of the platinum group metal elements, namely 34 tons of platinum, 61 tons of palladium and 7.2 tons of rhodium, are recovered from the spent catalyst by 2016.
Studies have shown that 93.42% of the platinum group metals fail from the hydrometallurgical processRecovering the catalyst. The noble metal in the spent catalyst is commonly hydrochloric acid (HCl) and hydrogen peroxide (H)2O2) The oxidant is used for obtaining soluble precious metal chloride leaching, and the precious metal can be obtained through replacement and refining processes. However, in addition to precious metals, the leachate often contains many heavy metals, such as nickel, copper, aluminum, magnesium, lead, chromium, iron, and non-metal soluble active Silicon (SiO)2) And the like. Therefore, the leachate after replacement and the waste liquid after refining contain a large amount of heavy metals and oxidants, and in order to reduce or eliminate the potential harm of the leachate after precious metal extraction to the environment, the precious metal recovery wastewater of the spent catalyst needs to be treated.
In recent years, methods for treating wastewater containing precious metals mainly include membrane technology, electrochemical methods, and biological adsorption methods. For example, a non-pressure driving membrane technology, namely a forward osmosis technology, which is widely used for treating coal bed gas brine and oil gas produced water is used for enriching palladium in palladium-containing printed circuit board wastewater. After the forward osmosis treatment, the concentration of palladium in the wastewater can be theoretically improved to 17.2 times. In addition, microbial fuel cells are used as one of electrochemical technologies to recover silver from wastewater. According to the report, after the simulated wastewater is treated for 72 hours by adopting the microbial fuel cell technology, the recovery rate of silver is up to 67.8%, and the removal rate of COD is up to 82.7%. The biological adsorption is widely used for recovering valuable metals from waste liquid due to the advantages of low cost, high efficiency, environmental friendliness and the like. Examples of the reported biosorbents for the biological recovery of palladium, platinum and copper include Escherichia coli (Escherichia coli), Serratia japonica (Shewanella oneidensis), Enterococcus faecalis (Enterococcus faecalis), Phomopsis sp, and Enterobacter cloacae (Enterobacter cloacae). From the above analysis, most of the studies are focused on the recovery or enrichment of precious metals from simulated wastewater, and no research report on the actual treatment of precious metal recovery wastewater is found. In the applied patent, only the multistage precipitation process is adopted to simply adjust the pH of the platinum-palladium precious metal recovery process wastewater, and then the wastewater is added with the medicine for physical precipitation treatment (utility model patent, application number 201320309115. X).
In recent years, Membrane Distillation (MD) has been used as a membrane technologyOne of them has the characteristics of low operating pressure, medium temperature, 100% interception of non-volatile substances, etc., and is used for treating industrial waste water containing heavy metals and recovering valuable substances from waste water of high-salt system. For example, aiming at the treatment of heavy metal wastewater in smelteries and mines, heavy metal ions are removed by adopting a lime neutralization and vulcanization precipitation mode, then the pretreated wastewater is concentrated by adopting membrane distillation, membrane pollution is reduced by adopting physical methods such as acid washing, ultrasonic cleaning and the like, and the concentrated wastewater is treated by a triple-effect evaporator (invention patent, application number 201110185079.6); the membrane distillation process is adopted to treat the acidic heavy metal wastewater of the sulfuric acid system, and the recovery of water resources and the reduction of the wastewater are carried out. Due to the large amount of Fe in the waste water3+Formation of Fe (OH) by adjusting the pH of the wastewater3Precipitating with colloid, filtering with filter cloth to remove Fe in wastewater3+To reduce Fe in wastewater3+Possible membrane fouling (patent application No. 201611120424.7); the above invention solves Fe3+Possible film contamination, but fails to address film distillation processing of Silicon (SiO) containing films2) Silicon pollution in the waste water process. The invention relates to a treatment method for waste water recovered from a spent catalyst noble metal, which is mainly characterized in that the waste water contains a large amount of Al3+And other heavy metal ions, the composition of the wastewater is complex, and the types and the salt contents of the metal ions are higher than those in the patent. In addition, the wastewater is strongly acidic (pH < 1) or strongly basic (pH > 12), and also contains a large amount of soluble Silicon (SiO)2) Is the main cause of film contamination during MD. The invention utilizes metal ions (Al) coexisting in the wastewater3+) Formation of amorphous white flocculent Al (OH) by adjusting the pH of the wastewater3Colloid, using Al (OH)3The adsorption characteristic of the colloid adsorbs soluble silicon in the wastewater, and then the soluble silicon is removed through coprecipitation. The method is mainly different from the content of the invention patent, utilizes the transformation of the metal ion form in the wastewater to remove the soluble silicon through the metal ion form transformation so as to reduce the silicon pollution on the surface of the membrane, is a novel discovery and more innovative method, and is helpful to solve the problem of the existence of the membrane technology in the actual industrial wastewater treatment processThe problem of silicon contamination provides a new solution.
Disclosure of Invention
Silicon (SiO) is frequently existed in MD during the process of treating industrial wastewater2) Contamination, which can lead to a rapid degradation of the membrane system performance due to silicon sticking to the membrane surface. The invention aims to solve the technical problem that the waste water from the recovery of noble metals from spent catalysts has serious silicon pollution in the membrane distillation treatment process, and provides a treatment method for the waste water from the recovery of noble metals from spent catalysts, which aims at reducing the membrane pollution of the waste water in the MD treatment process by utilizing the form change of coexisting metal ions in the waste water to adsorb and coprecipitate silicon and removing soluble silicon in the waste water through secondary filtration.
The invention relates to a waste water treatment method for recovering spent catalyst noble metal, which comprises the following steps:
(1) adjusting the pH value of the wastewater to gradually form white flocculent amorphous colloid, and then carrying out coarse filtration and fine filtration to obtain pretreated wastewater;
or directly carrying out coarse filtration and fine filtration on the wastewater to obtain pretreated wastewater;
(2) and (3) enabling the pretreated wastewater to enter a hot-side feed liquid pool in a membrane distillation system, heating and conveying the pretreated wastewater to enter a membrane component of the system, wherein volatile acid or water vapor in the wastewater enters a cold side through a hydrophobic membrane and then overflows to an overflow liquid collecting pool.
The main component of the failure catalyst is noble metal, active aluminum oxide (gamma-Al)2O3) With cordierite (2 MgO.2Al)2O3·5SiO2or 2FeO·2Al2O3·5SiO2)。
The noble metals include mainly gold, silver and platinum group metals. The method for recovering the noble metal of the spent catalyst is hydrometallurgy.
The precious metals described in this patent are mainly recovered from spent catalyst, so the recovery process is mainly hydrometallurgical.
The water quality is characterized in that the wastewater contains multiple heavy metal ions such as sodium, magnesium, potassium, strontium, iron, manganese, aluminum, chromium, copper, nickel, zinc and the like, and one or more of sulfate radicals, nitrate radicals, chloride ions, soluble active silicon and the like, and the wastewater has high salt content and is strong acid or strong alkali.
The initial concentration of aluminum ions in the wastewater is 10-12000 mg/L; the initial concentration of silicon is 10-30 mg/L.
The wastewater in the step (1) is strong acid wastewater with pH less than or equal to 1 or strong alkaline wastewater with pH more than or equal to 12, the pH is subjected to gradient adjustment by adopting sodium hydroxide and hydrochloric acid, and the change of the form of metal aluminum ions coexisting in the wastewater is utilized, namely, Al is utilized3+To form amorphous white flocculent Al (OH)3Colloid, using Al (OH)3Reducing or removing active silicon in the wastewater by the adsorption performance of the colloid, removing visible particles, suspended matters and produced white flocculent amorphous precipitate by coarse filtration by using a macroporous filter membrane, and further removing fine particles and colloidal substances in the wastewater by using a microporous filter membrane; wherein the pH of the acidic wastewater with the pH value less than or equal to 1 is adjusted to be less than or equal to 7 and less than or equal to 5; adjusting the pH value of the strongly alkaline waste water to be neutral.
A large amount of metal aluminum ions (Al) exist in the wastewater in the step (1)3+) Formation of Al (OH) by adjusting the pH of the wastewater3Colloid, using Al (OH)3The colloid has positive charge to adsorb soluble silicon in the waste water and remove soluble active silicon by coprecipitation. The coarse filtration adopts a macroporous filter membrane, and the aperture is 40-50 mu m; fine filtration adopts a small-pore filter membrane, and the pore diameter is 0.2-1 mu m; the material of the filter membrane is one or more of polysulfone, polyethersulfone, polytetrafluoroethylene and the like.
Step (2) carrying out coarse filtration and fine filtration on the acidic wastewater with the pH value less than or equal to 1, and then carrying out membrane distillation treatment to obtain industrial-grade hydrochloric acid (HCl) and simultaneously obviously reduce the volume of the wastewater; adjusting the pH of the acidic wastewater with the pH value less than or equal to 1 to 5 and less than or equal to 7, and utilizing Al coexisting in the wastewater3+To form amorphous white flocculent Al (OH)3Colloid, using Al (OH)3Adsorption properties of colloids to reduce or remove wasteActive silicon in water is coarsely filtered by a macroporous filter membrane to remove visible particles, suspended matters and produced white flocculent amorphous precipitate, and fine particles and colloidal substances in wastewater are further removed by a microporous filter membrane. In addition, strongly alkaline wastewater with pH value more than or equal to 12 is gradually adjusted to be neutral, and membrane distillation is carried out after pretreatment, so that the volume of wastewater with different degrees can be reduced, and high-quality water resources with different degrees can be recovered.
The obtained hydrochloric acid is obtained by membrane distillation of wastewater under acidic condition, and can be used for generating Al (OH) by adjusting the pH of the wastewater3The colloid further removes silicon in the wastewater through adsorption and coprecipitation (namely, through pH adjustment-white flocculent colloid-coarse filtration-fine filtration), thereby reducing silicon pollution on the surface of the membrane, obtaining high-quality water, greatly reducing the volume of the wastewater and further realizing near zero emission of the wastewater.
And (3) in the step (2), the membrane in the membrane assembly is a hydrophobic membrane, the surface contact angle is larger than 110 degrees, the acid and alkali resistance is realized, the membrane aperture is 0.1-1 mu m, and the membrane is made of one or more of an electrostatic spinning membrane or a composite material of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene.
The membrane distillation process in the step (2): the circulation flow rate is 4-15 cm/s, the temperature of a cold side is 20-30 degrees, the temperature of a hot side is 40-90 degrees, and low-grade industrial waste heat sources such as printing and dyeing factories and power plants can be utilized.
The membrane distillation treatment mode adopted in the membrane distillation treatment system in the step (2) can be direct contact type, indirect membrane distillation and vacuum membrane distillation.
The invention relates to a waste water treatment device for recovering spent catalyst noble metal, which comprises: 1. a hot side feed liquid tank, 2, a cold side permeation tank, 3, a membrane module, 4, a delivery pump, 5, a cold side permeation liquid overflow liquid collection tank, 6 and a conductivity meter; wherein the hot side portion and the cold side portion are connected by a membrane assembly.
The invention adds NaOH or hydrochloric acid into the strong acid or strong base high salt waste water to adjust the pH value of the waste water and utilizes the special Al in the waste water3+To form amorphous white flocculent Al (OH) having adsorption and purification capabilities3The colloid is used for adsorbing soluble active silicon in the wastewater,and removing by coprecipitation, Al (OH) formed simultaneously3The colloid can also purify waste water; followed by secondary membrane filtration to remove Al (OH) produced3Colloidal precipitation and tiny particles in the wastewater; the membrane distillation process is adopted to treat the wastewater with different pH values, so that high-quality hydrochloric acid (HCl) and high-quality wastewater with low conductivity can be obtained, and the volume of the wastewater can be greatly reduced.
The invention utilizes aluminum ions (Al) coexisting in the wastewater3+) Form change to form Al (OH) with the functions of adsorbing and purifying water body3Colloid, and soluble active Silicon (SiO) which is easy to pollute membrane in wastewater is reduced and removed2)。
The method adopts a microfiltration membrane to carry out coarse filtration on the precious metal recovery wastewater of the actual spent catalyst so as to remove visible suspended impurities; and then, filtering the wastewater after coarse filtration by using an ultrafiltration membrane to remove other invisible impurities in the wastewater. Then, treating the strong acid wastewater by adopting an advanced membrane distillation process to obtain industrial-grade hydrochloric acid (HCl); high-quality clean water can be obtained by treating strongly alkaline wastewater, and the volume of the wastewater is effectively reduced.
Advantageous effects
The method can recover hydrochloric acid (HCl) in the wastewater, obtain high-quality water and greatly reduce the volume of the wastewater, thereby achieving near-zero emission of the wastewater (as shown by Recovery (%) data in figures 2, 3 and 4).
The invention adopts the membrane distillation process to treat the wastewater with different pH values, can obtain high-quality hydrochloric acid (HCl) and high-quality wastewater with low conductivity, and can greatly reduce the volume of the wastewater (for example, the recovered HCl can be obtained from the data in Table 2, and the volume of the wastewater can be reduced as can be seen from recovery (%) data in figures 2, 3 and 4). The method can not only recover resources from the waste water recovered from the noble metal of the spent catalyst, but also realize near zero discharge of the waste water, and can economically and effectively treat the strong acid or strong alkali high-salinity waste water generated by the recovery of the noble metal resources.
Drawings
FIG. 1 is a flow chart of an MD treatment process for spent catalyst precious metal recovery wastewater; wherein, the device comprises a raw material tank at the hot side 1, a permeation tank at the cold side 2, a membrane distillation assembly 3, a delivery pump 4, a permeation liquid overflow liquid collecting tank at the cold side 5 and a conductivity meter 6;
FIG. 2 shows the relationship between the effluent conductivity and the water recovery rate under different pH conditions for the noble metal recovery and refining wastewater from the spent catalyst treated by membrane distillation;
FIG. 3 shows the relationship between the effluent conductivity and the water recovery rate under different pH conditions of the spent catalyst silver recovery wastewater treated by membrane distillation;
FIG. 4 shows the relationship between the effluent conductivity and the water recovery rate under different pH conditions for treating waste water containing platinum recovered as a spent catalyst by membrane distillation;
FIG. 5 is a flow chart of a spent catalyst precious metal recovery wastewater treatment process.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The water flux is calculated by the change of the effluent quality after passing through the membrane in unit time; the conductivity was measured directly on-line using a conductivity meter.
Example 1
The precious metal refining is to treat and purify coarse materials containing impurities and having low purity to obtain high-purity substances. The refining is one of the steps of purifying and recovering the noble metal of the spent catalyst, and the example of the scheme is to treat the recovered refined wastewater of the platinum of the actual spent catalyst and clarify the characteristics and the advantages of the invention.
The water quality indexes of the platinum recovery refining wastewater, which is an actual spent catalyst produced by a precious metal resource recovery company, are shown in the following table 1. The data in the table show that the refining wastewater has low pH and high salt content, the conventional reverse osmosis or nanofiltration technology is adopted, the operating pressure requirement is high, and the technology is not feasible, so that the conventional treatment method for the actual spent catalyst precious metal refining wastewater generally adopts neutralization precipitation to reduce the content of high-valence metal ions in the wastewater, simultaneously carries out belt type filter pressing dehydration on the generated materialized sludge, and finally carries out evaporation treatment on the neutralized wastewater. Therefore, the traditional 'neutralization-precipitation-evaporation' method is adopted to treat the refining wastewater, so that a large amount of chemical agents are consumed, and more materialized sludge is generated at the same time, and potential secondary pollution to the environment is caused. In addition, generally, the evaporation technology is adopted to treat the neutralized wastewater, so that the energy consumption is high.
In the embodiment, the practical spent catalyst platinum recovery refining wastewater is used as a research object, the water quality index is shown in the following table 1, and the data in the table shows that the refining wastewater has low pH and high salt content. Spent catalyst precious metal recovery refinery wastewater was treated using the process shown in figure 1. Placing 1.5L of spent catalyst precious metal recovery refining wastewater and 1.5L of deionized water in hot side and cold side feed liquid pools respectively, and starting circulating pumps on two sides to keep the liquid flow rate on two sides at 7.8cm/s when the temperatures of the hot side and the cold side are 60 ℃ and 20 ℃ respectively. And (3) observing the process performance of the MD process on the treatment of the refining wastewater with initial pH values of 0.03, 3, 5 and 7, and detecting the change of the concentration of soluble silicon in the wastewater, the MD water flux and the conductivity of effluent along with the recovery ratio. When the pH of the wastewater is adjusted to 3, 5 and 7 from the initial 0.03, the concentration of the soluble silicon in the wastewater is respectively reduced to 9.18mg/L, 0.15mg/L and 0.11mg/L from the initial 12mg/L after the crude filtration by the polysulfone micro-filtration membrane with the average pore diameter of 40 microns and the fine filtration by the polytetrafluoroethylene micro-filtration membrane with the average pore diameter of 0.45 microns, which indicates that the wastewater is subjected to Al (OH) formation3Colloid adsorption and coprecipitation treatment, and the soluble silicon in the wastewater can be effectively reduced after coarse filtration and fine filtration pretreatment. The water quality results of the MD system effluent at different pH values are shown in figure 2. It was found that when the membrane distillation was carried out on the refining wastewater having a different initial pH, the water flux was 11 to 13kg/m2H, the quality of the effluent varies greatly with the conductivity. As shown in FIG. 2, when the initial pH of the refining wastewater was controlled at 3, 5 and 7, the water recovery rate was less than 60%, and high-quality effluent having a low conductivity (conductivity < 400. mu.S/cm) was obtained. The quality of the effluent of the refining wastewater with an initial pH of 0.03 was analyzed and found (Table 2), wherein Cl was contained in the effluent-Higher content of other metal ions and lower content of other metal ions indicate general knowledgeHigh-quality hydrochloric acid (HCl) can be recovered by treating the waste water from the noble metal refining of the spent catalyst through the MD process.
TABLE 1 recovery of noble metals from spent catalysts and refining wastewater quality
TABLE 2 effluent quality analysis
| Analysis item | Unit of | Index (I) |
| Cl- | mg/L | 545 |
| K+ | mg/L | 0.38 |
| Na+ | mg/L | 0.36 |
| Ca2+ | mg/L | 4.78 |
| Mg2+ | mg/L | 0.56 |
Example 2
Silver is an important catalytic material and can be used as an active component of a variety of oxidation catalysts. Silver is an active component of a catalyst for producing ethylene oxide by an industrial ethylene oxidation method, and the mass content of the silver accounts for 15-40% of the catalyst. Therefore, people pay more and more attention to the reasonable utilization of limited resources and comprehensive recovery of secondary data. The embodiment of the invention takes the waste water generated by recovering silver from the spent catalyst as a research object, the quality of the silver recovered from the spent catalyst is shown in a table 3, and the characteristics and the advantages of the invention are clarified by treating the waste water generated by recovering silver by MD.
In the embodiment, waste water generated by recovering silver from a spent catalyst by a certain precious metal resource recovery company is taken as a research object, and the recovered silver quality of the spent catalyst is shown in table 3; the spent catalyst silver recovery wastewater was treated using the process shown in figure 1. Placing 1.5L of waste water of silver recovery of spent catalyst and 1.5L of deionized water in a hot side feed liquid pool and a cold side feed liquid pool respectively, and starting circulating pumps on two sides to control the flow rates of liquid on the hot side and the cold side to keep the flow rates of the liquid on the hot side and the cold side at 10.8cm/s when the temperatures of the hot side and the cold side are 60 ℃ and 20 ℃ respectively. When the pH value of the silver recovery wastewater is adjusted to 11, 9 and 7, after white flocculent colloid is removed after the silver recovery wastewater is subjected to rough filtration by a polysulfone microfiltration membrane with the average pore size of 40 micrometers and fine filtration by a polytetrafluoroethylene microfiltration membrane with the average pore size of 0.45 micrometers, the concentration of soluble silicon in the wastewater is detected to be respectively reduced from the initial 21mg/L to 1.5mg/L, 4.1mg/L and 6.8mg/L, which indicates that the concentration of the soluble silicon in the wastewater is obviously reduced after the pH adjustment, the rough filtration and the fine filtration. The process performance of the MD process on the treatment of the silver recovery wastewater with the pH values of 13.2, 11, 9 and 7 is considered, the change of the conductivity of the MD effluent along with the recovery ratio is detected, and the result is shown in the attached figure 3. When the membrane distillation is used for treating silver wastewater with different initial pH values, the water flux is found to be 8-16kg/m2H. As shown in fig. 3, MD run-out quality is related to the initial pH of the silver wastewater. Although high quality (conductivity) can be obtained under different initial pH conditions<25 mus/cm), but the initial pH of the silver recovery wastewater should be controlled to be about neutral, considering that the MD effluent quality co-workers maintain a relatively high water recovery rate. Meanwhile, as can be seen from fig. 3, the MD process can reduce the volume of the wastewater by 80%, effectively reducing the volume of the wastewater.
The conductivity of the effluent at neutral pH was less than 10. mu.S/cm, indicating that the water quality was very close to that of deionized water and that there was almost no impurity in the water.
TABLE 3 quality of silver recovery wastewater from spent catalyst
| Analysis item | Unit of | Index (I) |
| Electrical conductivity of | mS/cm | 28 |
| pH | -- | 13.2 |
| COD | mg/L | 222 |
| Cl- | mg/L | 2250 |
| SO4 2- | mg/L | 2758 |
| NO3 - | mg/L | 5081 |
| SiO2 | mg/L | 21 |
| Na+ | mg/L | 4088 |
| K+ | mg/L | 23 |
| Zn2+ | mg/L | 0.11 |
| Al3+ | mg/L | 22.37 |
| Ca2+ | mg/L | 10.18 |
| Fe3+ | mg/L | 0.15 |
| Mg2+ | mg/L | 0.15 |
Example 3
Platinum has good catalytic activity, and is widely applied to active components of catalytic materials in the fields of petrochemical industry, fine chemical industry, organic chemical industry, fuel cells, waste gas purification and the like. The platinum content in the spent catalyst is far higher than that of the raw ore, and the energy consumption, the environmental pollution degree and the process complexity of the recovery process are all lower than those of the raw ore exploitation. Because platinum resources are seriously deficient, the comprehensive recycling of secondary resources of platinum metal becomes an important source. The present example is an example of treating waste water from platinum recovery as an actual spent catalyst, and illustrates the characteristics and advantages of the present invention.
The source of the waste water of platinum recovery of spent catalyst is a noble metal resource recovery company, the water quality table is shown in figure 4, and the waste water of platinum recovery of spent catalyst is treated by the process shown in figure 1. Placing 1.5L of waste water of silver recovery of spent catalyst and 1.5L of deionized water in a hot side feed liquid pool and a cold side feed liquid pool respectively, starting circulating pumps on two sides when the temperatures of the hot side and the cold side are maintained at 60 ℃ and 20 ℃ respectively, and controlling the flow rates of the cold side and the hot side at 8.5 cm/s. The pH of the platinum recovery wastewater is respectively adjusted to 3, 5 and 7, white flocculent colloid is generated, the concentration of soluble silicon in the wastewater is reduced from the initial 16mg/L to 11.1mg/L, 0.2mg/L and 0.4mg/L after the coarse filtration and the fine filtration, and the concentration of the soluble silicon in the wastewater is obviously reduced after the pH adjustment, the coarse filtration and the fine filtration are carried out; the process performance of the MD process on the treatment of platinum recovery wastewater with initial pH values of 1, 3, 5 and 7 is considered, and the change of MD water flux and effluent conductivity along with the recovery ratio is detected, and the result is shown in figure 4. When the membrane distillation is used for treating platinum wastewater with different initial pH values, the water flux is between 9 and 12kg/m2H, and a higher water recovery was obtained at pH 5. As shown in fig. 4, MD water quality correlates with the initial pH of the platinum wastewater. At initial pH 1 and 3, the effluent conductivity increases exponentially; at pH 5, the conductivity of the MD effluent and the water recovery rate are in a linear relationship and are always kept at 2.45 mu S/cm; at pH 7, the MD effluent conductivity remained unchanged at 2.45. mu.S/cm until water recovery was 46%, and the curve coincided with the effluent conductivity curve at pH 5,after the water recovery rate exceeds 46%, the MD effluent conductivity rises rapidly, and the effluent quality is reduced. Further, it can be seen from fig. 4 that the volume of wastewater can be reduced by 70% at a neutral pH, and high-quality water can be obtained.
The conductivity of the effluent at neutral pH was less than 10uS/cm, indicating that the water quality was very close to that of deionized water and there were almost no impurities in the water.
TABLE 4 quality of waste water from platinum recovery with spent catalyst
| Analysis item | Unit of | Index (I) |
| Electrical conductivity of | mS/cm | 93 |
| pH | -- | 1 |
| COD | mg/L | 2324 |
| Cl- | mg/L | 55637 |
| SiO2 | mg/ |
16 |
| Na+ | mg/L | 96 |
| K+ | mg/L | 620 |
| Zn2+ | mg/L | 0.8 |
| Al3+ | mg/L | 11938 |
| Ca2+ | mg/L | 63 |
| Fe3+ | mg/L | 73.9 |
| Mg2+ | mg/L | 13.7 |
| Cu2+ | mg/L | 1.3 |
| Cr3+ | mg/L | 37 |
| Ni2+ | mg/L | 14.6 |
| Mn2+ | mg/L | 2.6 |
| Sr2+ | mg/L | 0.6 |
| Pt | mg/L | 1.88 |
In conclusion, the membrane distillation technology adopted by the invention can treat waste water generated by recovering the spent catalyst noble metal with different water quality characteristics, so that the waste water is reduced, and simultaneously, high-quality effluent can be obtained. Particularly, when the MD technology is adopted to treat the waste water recovered from the noble metal of the strongly acidic spent catalyst, the high-quality effluent can be obtained and the high-quality hydrochloric acid can be recovered by adjusting the initial pH of the waste water.
Claims (9)
1. A spent catalyst precious metal recovery wastewater treatment method comprises the following steps:
(1) adjusting the pH value of the wastewater, and performing coarse filtration and fine filtration to obtain pretreated wastewater;
(2) and (3) feeding the pretreated wastewater into a hot-side feed liquid pool in a membrane distillation system, heating and conveying the wastewater into a membrane component of the system, wherein volatile acid or water vapor in the wastewater enters a cold side through a hydrophobic membrane and then overflows into an overflow liquid collecting pool.
2. The treatment method according to claim 1, wherein the wastewater in the step (1) is wastewater generated after the displacement of spent catalyst precious metal leachate and/or precious metal purification refining waste; the waste water contains one or more heavy metal ions of sodium, magnesium, potassium, strontium, iron, manganese, aluminum, chromium, copper, nickel and zinc, and contains sulfate radical, nitrate radical, chloride ion and soluble active silicon, and the waste water is strong acid or strong alkali.
3. The treatment method according to claim 1, wherein the wastewater in the step (1) is strongly acidic wastewater having a pH of not more than 1 or strongly basic wastewater having a pH of not less than 12, the pH is adjusted by a gradient using sodium hydroxide and hydrochloric acid, and Al coexisting in the wastewater is used3+To form amorphous flocculent Al (OH)3Colloid, using Al (OH)3The adsorption performance of the colloid is used for reducing or removing the active silicon dissolved in the wastewater, thereby reducing the silicon SiO in the subsequent membrane treatment process2Pollution; wherein the pH of the acidic wastewater with the pH value less than or equal to 1 is adjusted to be less than or equal to 7 and less than or equal to 5; adjusting the pH value of the strongly alkaline waste water to be neutral.
4. The treatment method as claimed in claim 1, wherein the coarse filtration in step (1) is performed by using a macroporous filter membrane with a pore size of 40-50 μm; fine filtration adopts a small-pore filter membrane, and the pore diameter is 0.2-1 mu m; the material of the filter membrane is one or more of polysulfone, polyethersulfone and polytetrafluoroethylene.
5. The process of claim 1, wherein in step (2): directly carrying out coarse filtration and fine filtration on the wastewater with the pH value of less than or equal to 1 in the step (1) to obtain pretreated wastewater, and carrying out membrane distillation treatment on the pretreated wastewater to obtain industrial-grade hydrochloric acid (HCl); and (3) performing coarse filtration and fine filtration on the pH value of the wastewater adjusted in the step (1), and performing membrane distillation treatment on the pretreated wastewater to realize near zero emission of the wastewater.
6. The treatment method according to claim 1, wherein the membrane in the membrane assembly in the step (2) is a hydrophobic membrane, the surface contact angle is larger than 110 degrees, the acid and alkali resistance is realized, the membrane aperture is 0.1-1 μm, and the membrane is made of one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene, and is an electrospun membrane or a composite material.
7. The treatment method according to claim 1, wherein the membrane distillation process in the step (2): the circulating flow rate is 4-15 cm/s, the temperature of a cold side is 20-30 degrees, and the temperature of a hot side is 40-90 degrees.
8. The treatment method according to claim 1, wherein the membrane distillation treatment method adopted in the membrane distillation treatment system in the step (2) can be direct contact type, indirect membrane distillation and vacuum membrane distillation.
9. A spent catalyst precious metal recovery wastewater treatment device comprises: the device comprises a hot side raw material pool (1), a cold side permeation pool (2), a membrane component (3), a delivery pump (4), a cold side permeation liquid overflow liquid collecting pool (5) and a conductivity meter (6).
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| CN108373246A (en) * | 2018-05-04 | 2018-08-07 | 王峰 | Domestic sewage treatment device |
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| CN102295378A (en) * | 2010-06-28 | 2011-12-28 | 中国石油化工股份有限公司 | Treatment and recycling method of ammonia nitrogen containing high-salt catalyst wastewater |
| CN103803752A (en) * | 2012-11-06 | 2014-05-21 | 中国石油化工股份有限公司 | Treatment method of wastewater with high salinity and high organic matters |
| CN108439669A (en) * | 2018-03-09 | 2018-08-24 | 成都飞创科技有限公司 | Silica minimizing technology in a kind of water |
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