CN108358375B - Industrial sewage treatment method - Google Patents

Abstract

The invention provides an industrial sewage treatment method, which comprises the following steps: mechanical treatment; (II) softening treatment; (III) strengthening coagulation; (IV) degrading organic matters by pulse discharge plasma-photocatalysis synergy; (V) processing the nano zero-valent iron by ultrasonic cooperation; sixthly, adsorbing the cellulose aerogel of the iron wire cage framework; and (seventhly) performing ultrafiltration/nanofiltration-reverse osmosis integrated membrane treatment. The industrial sewage treatment method provided by the invention has the advantages of simple process and short operation period, can thoroughly remove pollutants such as suspended matters, organic matters, salts and the like contained in the industrial sewage, has a good removal effect on various types of persistent organic pollutants and heavy metals, has universality for removing the pollutants, is high in heavy metal recovery rate, good in economic benefit, high in process flexibility, strong in impact load resistance and high in sewage recovery rate, and is suitable for sewage treatment in various fields such as electric power, photovoltaic, photoelectricity, semiconductors, electronics, pharmacy, metallurgy, petrifaction and the like.

Description

Industrial sewage treatment method

Technical Field

The invention relates to the technical field of sewage treatment, in particular to an industrial sewage treatment method.

Background

The industrial sewage is complex in components, and if the pollution components are not treated, the pollution components are directly discharged into the environment, so that the pollution to the land and water sources can cause great harm. Persistent Organic Pollutants (POPs) are natural or synthetic organic pollutants that can migrate long distances through various environmental media (atmosphere, water, organisms, etc.) and exist in the environment for a long time, have long-term residue, bioaccumulation, semi-volatility, and high toxicity, and have serious hazards to human health and the environment. Aiming at the characteristics of high toxicity, durability, accumulation and high fluidity of persistent organic pollutants, the research of thoroughly degrading the persistent organic pollutants without generating new pollutants in the sewage treatment becomes a hot point of research in recent years.

The industrial sewage has complex water quality components, and generally has the characteristics of high suspended matters and turbidity, high salt content, high chemical oxygen demand and various heavy metal types. At present, the industrial sewage treatment mainly and comprehensively uses technical methods such as a physical method, a chemical method, a biological method and the like; physical methods include multiple-effect evaporation, ionization, reverse osmosis, ultrafiltration, nanofiltration and the like, require a large amount of power resources, and are expensive in operation cost; the chemical method is usually to add a macromolecular oxidant and a chemical flocculant into water, and has the defects of large dosage, long standing time and secondary pollution; the biochemical method has the advantages of stability and low cost in domestic sewage treatment, but cannot treat industrial sewage with high heavy metal content, high organic matter concentration and high salt. Therefore, aiming at the characteristics of industrial sewage, the research on a treatment method which can comprehensively remove various pollutants in the sewage, thoroughly degrade persistent organic pollutants and efficiently recover heavy metals and water resources is of great significance.

Disclosure of Invention

The invention aims to provide the industrial sewage treatment method which is simple to operate, flexible in process, good in persistent organic pollutant degradation effect, high in heavy metal recovery rate, low in cost, free of secondary pollution and high in sewage recovery rate.

The purpose of the invention is realized by the following technical scheme:

an industrial sewage treatment method comprises the following steps:

mechanical treatment: filtering industrial sewage by a mechanical grating, and feeding filtered effluent into an oil-water separator to remove impurities, floating oil and suspended matters;

(II) softening treatment: introducing the effluent of the oil-water separator into a chemical reactor, adding soda ash, stirring and mixing to ensure that the pH value ranges from 8 to 11, removing hardness ions such as calcium, magnesium and the like to soften a water body, and reacting to generate suspended floc particles;

(III) reinforced coagulation: introducing the softened effluent into a coagulation air flotation machine, adding a cationic flocculant according to 0.1-0.3 kg per ton of water, removing grease, colloid, suspended solids and suspended floc particles generated in the step (II), and reducing the BOD and COD content in the sewage;

(IV) degrading organic matters by the aid of pulsed discharge plasma and photocatalysis: directly introducing the effluent of the coagulation air flotation machine into a pulse discharge plasma-photocatalytic reactor for reaction for 20-40 min;

(V) ultrasonic synergetic nano zero-valent iron treatment: under the action of ultrasonic waves, nanometer zero-valent iron and heavy metals in the effluent of the pulse discharge plasma-photocatalytic reactor are subjected to synergistic effects of reduction, adsorption and coprecipitation, so that the removal effect is achieved, and solid-liquid separation is carried out in a precipitation zone;

(VI) adsorbing the cellulose aerogel of the iron wire cage framework: introducing the separated effluent into an adsorption tank, adding iron wire cage skeleton cellulose aerogel, treating for 20-40 s under the action of a magnetic field, separating from the water body, and desorbing and recovering heavy metal ions;

(VII) ultrafiltration/nanofiltration-reverse osmosis integrated membrane treatment: after the effluent of the adsorption tank is treated by an ultrafiltration/nanofiltration-reverse osmosis integrated membrane method, the COD (chemical oxygen demand) of the effluent is less than 15mg/L, and the conductivity is less than 20 mu S/cm, thereby reaching the national class I surface water environmental quality standard (GB-3838-.

Specifically, the cationic flocculant used in the step (III) is obtained by performing free radical polymerization reaction on acrylamide and dimethyl diallyl ammonium chloride through irradiation.

Specifically, in the step (IV), the pulse discharge plasma-photocatalytic reactor is columnar, the wall of the reactor is made of quartz glass, TiO is decorated between the discharge anode and the aluminum mesh cathode in different lengths₂-Bi₂WO₄A thin-film quartz glass plate acts as a barrier medium.

Specifically, the preparation method of the cellulose aerogel with the iron wire cage framework in the step (six) comprises the following steps:

(1) mixing PVA and DMSO, adding water to form a mixed solution, and mixing the mixed solution and the cellulose nano-microcrystalline suspension to form a final suspension;

(2) the final suspension was stirred at room temperature for 4h and transferred to a glass vessel;

(3) and injecting the suspension in the glass container into an iron cage framework mold, directionally freezing the suspension for 10min by using liquid nitrogen, immediately putting the suspension into a freeze dryer after freezing, and sublimating to remove ice crystals to obtain the iron cage framework cellulose aerogel with the average diameter of 10 mm.

Specifically, the ultrafiltration membrane used in the step (VII) is a cellulose triacetate ultrafiltration membrane, the nanofiltration membrane is a PVC-based hollow fiber composite nanofiltration membrane, and the reverse osmosis membrane is a biguanide-based polyvinylamine modified reverse osmosis membrane.

According to the invention, the softening treatment step is added after the mechanical treatment, so that calcium and magnesium hardness ions can be removed, suspended floc particles are generated through reaction, the settling rate during reinforced coagulation can be increased, the coagulation efficiency can be greatly improved, and the use amount of a cationic flocculant is reduced; in addition, the membrane pollution degree during the subsequent integrated membrane treatment can be reduced, the backwashing period is prolonged, and the operation stability of the process is improved;

the pulse discharge plasma-photocatalytic reactor integrates high-energy electron bombardment, hydroxyl radical oxidation, ultraviolet light degradation and ozone oxidation effects, and oxidizes and degrades persistent organic pollutant dye molecules, phenol, dioxin, bisphenol A, polychlorinated biphenyl, chloroform, acetic acid, acetaldehyde and the like into CO₂、H₂O and inorganic salt, and TiO is used as a catalyst for photocatalytic reaction₂-Bi₂WO₄Composite catalyst, TiO₂Can absorb ultraviolet light generated in the process of pulse discharge, and because the wall of the reactor is made of quartz and Bi₂WO₄As a visible light catalyst, natural light can be directly utilized, the power consumption can be reduced, and the composite catalyst can obviously improve the degradation rate of organic matters; the smaller the particle size of the photocatalyst, the higher the performance, but the more difficult it is to recover and reuse, and all the photocatalysts used in the prior art are TiO₂Powder of TiO₂The powder has the defects of easy aggregation, easy inactivation, difficult recycling, difficult reutilization and the like in the photocatalytic water treatment process, and the invention uses TiO₂-Bi₂WO₄The composite catalyst film is decorated on the surface of the quartz glass sheet to play a role of medium blocking, the catalyst is convenient to contact with water, the quantity and the area of the quartz glass sheet can be adjusted according to the concentration of organic matters in the sewage treatment process, the organic matters are completely degraded, the quartz glass sheet is convenient to take out, and the separation and the recovery of the catalyst are facilitated.

According to the invention, the iron wire cage framework cellulose aerogel used in the invention is added with a small amount of DMSO (dimethyl sulfoxide) in water as a mixed solvent, the aerogel presents a uniform structure, has a porous structure and high porosity, and the iron wire cage is used as the framework of the cellulose aerogel, so that on one hand, the shape and size of the aerogel can be controlled in the preparation process; on the other hand, the ferromagnetism of the iron wire cage is utilized to ensure that the cellulose aerogel directionally moves under the action of a magnetic field, the cellulose aerogel fully acts with a water body to adsorb trace heavy metal ions in the water body, the larger the structural size of the aerogel is, the better the compression performance is, and compared with a common nano adsorbent, the used iron wire cage skeleton cellulose aerogel has the advantages of better adsorption performance, larger size, difficulty in loss, convenience in recovery and desorption and high recycling rate.

Compared with the prior art, the invention has the following beneficial effects:

1. the industrial sewage treated by the method has no suspended matters detected in the effluent, COD is less than 15mg/L, the heavy metal removal rate is more than 99 percent, the total hardness is less than 20mg/L, the conductivity is less than 20 mu S/cm, and the water resource recovery rate is more than 90 percent;

2. in the step of the reinforced coagulation, the adopted cationic flocculant is a copolymer of acrylamide and dimethyl diallyl ammonium chloride, has the advantages of high positive charge density, stable cationic unit structure and good water solubility, is synthesized by one step by adopting an irradiation method, has no secondary pollution, has a unique multilayer compact space three-dimensional network structure, and has a flocculation effect superior to that of a common flocculant;

3. the invention adopts the ultrasonic to cooperate with the nano zero-valent iron to treat the industrial sewage, the shock wave generated by the ultrasonic enables the nano zero-valent iron particles to be dispersed and suspended in the reaction system, the reaction active sites are increased, the molecules are rapidly oscillated, the reaction conditions in the homogenization system can enhance the mass transfer effect of the two-phase interface, the shedding of the surface oxide layer of the nano zero-valent iron is accelerated, the reaction rate is accelerated, and the invention is an integrated device, has small occupied area, simple process, convenient operation and management, high treatment efficiency, less sludge amount, and can recover valuable metals such as gold, silver and the like in the sludge, and has good economic benefit;

4. the ultrafiltration/nanofiltration-reverse osmosis integrated membrane method adopted by the invention can completely remove bacteria, organic matter macromolecules and heavy metal ions in the water body, the method has the advantages of simple operation, low energy consumption, no secondary pollution, high desalination rate and stable water quality of produced water, and the effluent can be directly reused for production.

Drawings

FIG. 1 is a schematic view of a pulsed discharge plasma-photocatalytic reactor,wherein 1-air compression system, 2-gas flowmeter, 3-pulse power supply, 4-tail gas purification and discharge, 5-discharge anode, 6-modified TiO₂-Bi₂WO₄A thin film of quartz glass, a 7-aluminum mesh cathode.

Detailed Description

To further illustrate the technical means adopted by the present invention and the effects thereof, the following detailed description is given with reference to the accompanying drawings and preferred embodiments of the present invention.

The sewage generated in the production process of a certain chemical workshop has the characteristics of complex source, large fluctuation of the amount of the wastewater and the quality of the wastewater, the content of main pollutants is shown in a table 1, the content of persistent organic pollutants is shown in a table 2, and the content of heavy metals is shown in a table 3.

TABLE 1 content of contaminants in wastewater generated during the production process in a chemical plant

TABLE 2 persistent organic contaminant content in the effluent generated during the production process in a chemical plant

TABLE 3 heavy metal content in the wastewater generated during the production process in a certain chemical plant

Example 1

An industrial sewage treatment method comprises the following steps:

mechanical treatment: filtering industrial sewage by a mechanical grating, and feeding filtered effluent into an oil-water separator to remove impurities, floating oil and suspended matters;

(II) softening treatment: introducing the effluent of the oil-water separator into a chemical reactor, adding soda ash, stirring and mixing to enable the pH value to be 8, removing hardness ions such as calcium, magnesium and the like to soften a water body, and simultaneously reacting to generate suspended floc particles;

(III) reinforced coagulation: introducing the softened effluent into a coagulation air flotation machine, adding a cationic flocculant according to 0.1kg per ton of water, removing grease, colloid, suspended solid and suspended floc particles generated in the step (II), and reducing the BOD and COD content in the sewage;

(IV) degrading organic matters by the aid of pulsed discharge plasma and photocatalysis: directly introducing the effluent of the coagulation air flotation machine into a pulse discharge plasma-photocatalytic reactor (shown in figure 1) for reaction for 20 min;

(V) ultrasonic synergetic nano zero-valent iron treatment: under the action of ultrasonic waves, nanometer zero-valent iron and heavy metals in the effluent of the pulse discharge plasma-photocatalytic reactor are subjected to synergistic effects of reduction, adsorption and coprecipitation, so that the removal effect is achieved, and solid-liquid separation is carried out in a precipitation zone;

(VI) adsorbing the cellulose aerogel of the iron wire cage framework: introducing the separated effluent into an adsorption tank, adding iron wire cage skeleton cellulose aerogel, treating for 20s under the action of a magnetic field, separating from the water body, and desorbing to recover heavy metal ions;

(VII) ultrafiltration/nanofiltration-reverse osmosis integrated membrane treatment: after the effluent of the adsorption tank is treated by an ultrafiltration/nanofiltration-reverse osmosis integrated membrane method, the COD of the effluent is 14mg/L, and the conductivity is 17 mu S/cm, thereby reaching the national class I surface water environmental quality standard (GB-3838-.

Specifically, the cationic flocculant used in the step (III) is obtained by performing free radical polymerization reaction on acrylamide and dimethyl diallyl ammonium chloride through irradiation.

Specifically, in the step (IV), the pulsed discharge plasma-photocatalytic reactor (shown in figure 1) is columnar, the wall of the reactor is made of quartz glass, TiO modified materials with different lengths are placed between a discharge anode (shown in figure 1 by 3) and an aluminum mesh cathode (shown in figure 1 by 7)₂-Bi₂WO₄A thin film of quartz glass (shown at 6 in fig. 1) acts as the barrier medium.

Specifically, the preparation method of the cellulose aerogel with the iron wire cage framework in the step (six) comprises the following steps:

(1) mixing PVA and DMSO, adding water to form a mixed solution, and mixing the mixed solution and the cellulose nano-microcrystalline suspension to form a final suspension;

(2) the final suspension was stirred at room temperature for 4h and transferred to a glass vessel;

(3) and injecting the suspension in the glass container into an iron cage framework mold, directionally freezing the suspension for 10min by using liquid nitrogen, immediately putting the suspension into a freeze dryer after freezing, and sublimating to remove ice crystals to obtain the iron cage framework cellulose aerogel with the average diameter of 10 mm.

Specifically, the ultrafiltration membrane used in the step (VII) is a cellulose triacetate ultrafiltration membrane, the nanofiltration membrane is a PVC-based hollow fiber composite nanofiltration membrane, and the reverse osmosis membrane is a biguanide-based polyvinylamine modified reverse osmosis membrane.

Example 2

An industrial sewage treatment method comprises the following steps:

mechanical treatment: filtering industrial sewage by a mechanical grating, and feeding filtered effluent into an oil-water separator to remove impurities, floating oil and suspended matters;

(II) softening treatment: introducing the effluent of the oil-water separator into a chemical reactor, adding soda ash, stirring and mixing to ensure that the pH value is 9, removing hardness ions such as calcium, magnesium and the like to soften a water body, and simultaneously reacting to generate suspended floc particles;

(III) reinforced coagulation: introducing the softened effluent into a coagulation air flotation machine, adding a cationic flocculant according to 0.2kg per ton of water, removing grease, colloid, suspended solid and suspended floc particles generated in the step (II), and reducing the BOD and COD content in the sewage;

(IV) degrading organic matters by the aid of pulsed discharge plasma and photocatalysis: directly introducing the effluent of the coagulation air flotation machine into a pulse discharge plasma-photocatalytic reactor (shown in figure 1) for reaction for 30 min;

(V) ultrasonic synergetic nano zero-valent iron treatment: under the action of ultrasonic waves, nanometer zero-valent iron and heavy metals in the effluent of the pulse discharge plasma-photocatalytic reactor are subjected to synergistic effects of reduction, adsorption and coprecipitation, so that the removal effect is achieved, and solid-liquid separation is carried out in a precipitation zone;

(VI) adsorbing the cellulose aerogel of the iron wire cage framework: introducing the separated effluent into an adsorption tank, adding iron wire cage skeleton cellulose aerogel, treating for 30s under the action of a magnetic field, separating from the water body, and desorbing to recover heavy metal ions;

(VII) ultrafiltration/nanofiltration-reverse osmosis integrated membrane treatment: after the effluent of the adsorption tank is treated by an ultrafiltration/nanofiltration-reverse osmosis integrated membrane method, the COD of the effluent is 13mg/L, and the conductivity is 16 MuS/cm, thereby reaching the national class I surface water environmental quality standard (GB-3838-.

Specifically, the cationic flocculant used in the step (III) is obtained by performing free radical polymerization reaction on acrylamide and dimethyl diallyl ammonium chloride through irradiation.

Specifically, in the step (IV), the pulsed discharge plasma-photocatalytic reactor (shown in figure 1) is columnar, the wall of the reactor is made of quartz glass, TiO modified materials with different lengths are placed between a discharge anode (shown in figure 1 by 3) and an aluminum mesh cathode (shown in figure 1 by 7)₂-Bi₂WO₄A thin film of quartz glass (shown at 6 in fig. 1) acts as the barrier medium.

Specifically, the preparation method of the cellulose aerogel with the iron wire cage framework in the step (six) comprises the following steps:

(1) mixing PVA and DMSO, adding water to form a mixed solution, and mixing the mixed solution and the cellulose nano-microcrystalline suspension to form a final suspension;

(2) the final suspension was stirred at room temperature for 4h and transferred to a glass vessel;

(3) and injecting the suspension in the glass container into an iron cage framework mold, directionally freezing the suspension for 10min by using liquid nitrogen, immediately putting the suspension into a freeze dryer after freezing, and sublimating to remove ice crystals to obtain the iron cage framework cellulose aerogel with the average diameter of 10 mm.

Specifically, the ultrafiltration membrane used in the step (VII) is a cellulose triacetate ultrafiltration membrane, the nanofiltration membrane is a PVC-based hollow fiber composite nanofiltration membrane, and the reverse osmosis membrane is a biguanide-based polyvinylamine modified reverse osmosis membrane.

Example 3

An industrial sewage treatment method comprises the following steps:

mechanical treatment: filtering industrial sewage by a mechanical grating, and feeding filtered effluent into an oil-water separator to remove impurities, floating oil and suspended matters;

(II) softening treatment: introducing the effluent of the oil-water separator into a chemical reactor, adding soda ash, stirring and mixing to ensure that the pH value range is 11, removing hardness ions such as calcium, magnesium and the like to soften a water body, and simultaneously reacting to generate suspended floc particles;

(III) reinforced coagulation: introducing the softened effluent into a coagulation air flotation machine, adding a cationic flocculant according to 0.3kg per ton of water, removing grease, colloid, suspended solid and suspended floc particles generated in the step (II), and reducing the BOD and COD content in the sewage;

(IV) degrading organic matters by the aid of pulsed discharge plasma and photocatalysis: directly introducing the effluent of the coagulation air flotation machine into a pulse discharge plasma-photocatalytic reactor (shown in figure 1) for reaction for 40 min;

(V) ultrasonic synergetic nano zero-valent iron treatment: under the action of ultrasonic waves, nanometer zero-valent iron and heavy metals in the effluent of the pulse discharge plasma-photocatalytic reactor are subjected to synergistic effects of reduction, adsorption and coprecipitation, so that the removal effect is achieved, and solid-liquid separation is carried out in a precipitation zone;

(VI) adsorbing the cellulose aerogel of the iron wire cage framework: introducing the separated effluent into an adsorption tank, adding iron wire cage skeleton cellulose aerogel, treating for 40s under the action of a magnetic field, separating from the water body, and desorbing to recover heavy metal ions;

(VII) ultrafiltration/nanofiltration-reverse osmosis integrated membrane treatment: after the effluent of the adsorption tank is treated by an ultrafiltration/nanofiltration-reverse osmosis integrated membrane method, the COD of the effluent is 11mg/L, and the conductivity is 10 MuS/cm, thereby reaching the national class I surface water environmental quality standard (GB-3838-.

Specifically, the cationic flocculant used in the step (III) is obtained by performing free radical polymerization reaction on acrylamide and dimethyl diallyl ammonium chloride through irradiation.

Specifically, in the step (IV), the pulsed discharge plasma-photocatalytic reactor (shown in figure 1) is columnar, the wall of the reactor is made of quartz glass, TiO modified materials with different lengths are placed between a discharge anode (shown in figure 1 by 3) and an aluminum mesh cathode (shown in figure 1 by 7)₂-Bi₂WO₄A thin film of quartz glass (shown at 6 in fig. 1) acts as the barrier medium.

Specifically, the preparation method of the cellulose aerogel with the iron wire cage framework in the step (six) comprises the following steps:

(1) mixing PVA and DMSO, adding water to form a mixed solution, and mixing the mixed solution and the cellulose nano-microcrystalline suspension to form a final suspension;

(2) the final suspension was stirred at room temperature for 4h and transferred to a glass vessel;

(3) and injecting the suspension in the glass container into an iron cage framework mold, directionally freezing the suspension for 10min by using liquid nitrogen, immediately putting the suspension into a freeze dryer after freezing, and sublimating to remove ice crystals to obtain the iron cage framework cellulose aerogel with the average diameter of 10 mm.

Specifically, the ultrafiltration membrane used in the step (VII) is a cellulose triacetate ultrafiltration membrane, the nanofiltration membrane is a PVC-based hollow fiber composite nanofiltration membrane, and the reverse osmosis membrane is a biguanide-based polyvinylamine modified reverse osmosis membrane.

Water quality analysis method

The chroma of the water body is measured by a dilution multiple method; measuring suspended matters by adopting a gravimetric method; COD is determined by a potassium dichromate method; BOD is measured by a dilution and inoculation method; the total hardness is measured by an ethylene diamine tetraacetic acid titration method; conductivity and pH were determined according to standard test methods; extracting persistent organic pollutants in the sewage by adopting a solid phase extraction column, and measuring by adopting a mass spectrum or a gas chromatography; the concentrations of heavy metals Cu, Cd, Pb, Ni and Zn in the sewage are determined by adopting a flame atomic absorption spectrometry, and the concentrations of Hg and As are determined by adopting an atomic fluorescence spectrometry.

Effect of treatment

The effluent quality of the sewage generated in the production process of the chemical workshop after being treated by the industrial sewage treatment method is shown in the table 4.

TABLE 4 effluent quality of industrial wastewater treated in examples 1-3

Examples	Example 1	Example 2	Example 3
				Color intensity	1	1	0
SS(mg/L)	0	0	0
				COD(mg/L)	14	13	11
BOD(mg/L)	5.6	5.3	4.1
				Total hardness (mg/L)	19	12	17
Conductivity (us/cm)	17	16	10
				Dioxin (DIOXIN)	0.05	0.06	0.01
Bisphenol A	0.02	0.01	0.02
				Phenol and its preparation	0	0	0
Polychlorinated biphenyls	0.03	0.09	0.04
				Toluene	0	0.01	0
Dibutyl phthalate	0	0	0
				pH	7.1	6.9	7.4
Copper (mg/L)	0.16	0.10	0.08
				Cadmium (mg/L)	0.008	0.007	0.006
Lead (mg/L)	0.006	0.006	0.005
				Nickel (mg/L)	0.01	0.01	0.01
Zinc (mg/L)	0.02	0.03	0.01
				Manganese (mg/L)	0.04	0.05	0.03
Mercury (mg/L)	0.001	0.001	0.001
				Arsenic (mg/L)	0.009	0.007	0.006

As can be seen from Table 4, the industrial sewage treated by the method disclosed by the embodiments 1-3 can obviously reduce the chromaticity of the sewage, completely remove suspended matters in the sewage, completely remove organic matters, ensure that the COD is less than 20mg/L, the BOD is less than 10mg/L, the desalination rate is high, the total hardness is less than 20mg/L, the conductivity is less than 20us/cm, and the method has a good removal effect on various persistent organic pollutants and heavy metals, ensures that the quality of the effluent reaches the national class I surface water environmental quality standard (GB-3838 + 2002), can be directly reused for production, and ensures that the sewage recovery rate is more than 90%.

Recovery and utilization of valuable metals

The wet sludge yield of the method is 0.4-1.1 kg/t sewage, and the water content of the wet sludge is 40% -50%. The platinum content in the sludge is 3-40 g/t; the palladium content is 5-80 g/t; the content of gold is 20-155 g/t, the content of silver is 35-450 g/t, the content of copper is 275-3600 g/t, the recovery value of platinum, palladium, gold, silver and copper is high, and great economic benefit is generated.

Economic analysis

The sewage treatment cost comprises electric charge, medicament charge, labor charge and the like. Wherein the electricity charge is 1.2 yuan/t, the medicament charge is 12.0 yuan/t, and the labor charge is 0.25 yuan/t.

The industrial sewage treatment method provided by the invention firstly removes large impurities, floating oil and suspended matters through mechanical treatment; then adding soda ash to soften the water body and reacting to generate flocculent particles; then removing most suspended matters, colloids and macromolecular organic matters through reinforced coagulation; then degrading the organic matters through the four-pulse discharge plasma-photocatalysis synergy, thoroughly oxidizing persistent organic pollutants which are difficult to biodegrade into water, carbon dioxide and inorganic salt, ensuring that the COD of the effluent is less than 15mg/L, and the degradation of the organic matters is also beneficial to the release of complex heavy metal ions so as to be convenient for the subsequent removal of the heavy metal ions; removing heavy metals in the polluted water body by using the ultrasonic and nano zero-valent iron, wherein the nano zero-valent iron has small particle size, large specific surface area, high reaction activity and strong reducibility, the nano zero-valent iron particles are dispersed and suspended in the reaction system by shock waves generated by the ultrasonic, reaction active sites are increased, molecules are rapidly oscillated, the reaction conditions in the system are homogenized, the mass transfer effect of a two-phase interface can be enhanced, the shedding of an oxide layer on the surface of the nano zero-valent iron is accelerated, the sludge settling performance is good, and valuable metals in the sludge can be recycled; the trace heavy metal ions which are not removed by the nano zero-valent iron can be adsorbed by the cellulose aerogel of the iron wire cage framework moving under the action of the magnetic field, so that the heavy metal ions are separated from the water body, and the content of various heavy metals in the treated sewage can meet the drinking water standard; and finally, the ultrafiltration/nanofiltration-reverse osmosis integrated membrane method can remove most inorganic salts, the total hardness of the treated effluent is less than 20mg/L, and the conductivity is below 20 us/cm.

In conclusion, the industrial sewage treatment method provided by the invention has the advantages of simple process and short operation period, can thoroughly remove pollutants such as suspended matters, organic matters, salts and the like contained in the industrial sewage, has a good removal effect on various types of persistent organic pollutants and heavy metals, has universality for removing the pollutants, is high in heavy metal recovery rate, good in economic benefit, high in process flexibility, strong in impact load resistance and high in sewage recovery rate, and is suitable for sewage treatment in various fields such as electric power, photovoltaic, photoelectricity, semiconductors, electronics, pharmacy, metallurgy, petrifaction and the like.

The above description is only for the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and other modifications or equivalent substitutions made by the technical solution of the present invention by the ordinary skilled in the art should be covered within the scope of the claims of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims (2)

1. The industrial sewage treatment method is characterized by comprising the following steps:

mechanical treatment: filtering industrial sewage by a mechanical grating, and feeding filtered effluent into an oil-water separator to remove impurities, floating oil and suspended matters;

(II) softening treatment: introducing the effluent of the oil-water separator into a chemical reactor, adding soda ash, stirring and mixing to ensure that the pH value ranges from 8 to 11, removing hardness ions such as calcium, magnesium and the like to soften a water body, and reacting to generate suspended floc particles;

(III) reinforced coagulation: introducing the softened effluent into a coagulation air flotation machine, adding a cationic flocculant according to 0.1-0.3 kg per ton of water, removing grease, colloid, suspended solids and suspended floc particles generated in the step (II), and reducing the BOD and COD content in the sewage; the cationic flocculant is obtained by performing free radical polymerization reaction on acrylamide and dimethyl diallyl ammonium chloride through irradiation;

(IV) degrading organic matters by the aid of pulsed discharge plasma and photocatalysis: directly introducing the effluent of the coagulation air flotation machine into a pulse discharge plasma-photocatalytic reactor for reaction for 20-40 min; the pulse discharge plasma-photocatalytic reactor is columnar, the wall of the reactor is made of quartz glass, TiO is arranged between the discharge anode and the aluminum mesh cathode in different lengths₂-Bi₂WO₄The quartz glass sheet of the film is used as a barrier medium;

(V) ultrasonic synergetic nano zero-valent iron treatment: under the action of ultrasonic waves, nanometer zero-valent iron and heavy metals in the effluent of the pulse discharge plasma-photocatalytic reactor are subjected to synergistic effects of reduction, adsorption and coprecipitation, so that the removal effect is achieved, and solid-liquid separation is carried out in a precipitation zone;

(VI) adsorbing the cellulose aerogel of the iron wire cage framework: introducing the separated effluent into an adsorption tank, adding iron wire cage skeleton cellulose aerogel, treating for 20-40 s under the action of a magnetic field, separating from the water body, and desorbing and recovering heavy metal ions; the preparation method of the iron wire cage skeleton cellulose aerogel comprises the following steps: (1) mixing PVA and DMSO, adding water to form a mixed solution, and mixing the mixed solution and the cellulose nano-microcrystalline suspension to form a final suspension; (2) the final suspension was stirred at room temperature for 4h and transferred to a glass vessel; (3) injecting the suspension in the glass container into an iron cage framework mold, directionally freezing for 10min by using liquid nitrogen, immediately putting the frozen suspension into a freeze dryer, and sublimating to remove ice crystals to obtain the iron cage framework cellulose aerogel with the average diameter of 10 mm;

(VII) ultrafiltration/nanofiltration-reverse osmosis integrated membrane treatment: after the effluent of the adsorption tank is treated by an ultrafiltration/nanofiltration-reverse osmosis integrated membrane method, the COD (chemical oxygen demand) of the effluent is less than 15mg/L, and the conductivity is less than 20 mu S/cm, thereby reaching the national class I surface water environmental quality standard (GB-3838-.

2. The industrial sewage treatment method according to claim 1, wherein the ultrafiltration membrane used in the step (VII) is a cellulose triacetate ultrafiltration membrane, the nanofiltration membrane used is a PVC-based hollow fiber composite nanofiltration membrane, and the reverse osmosis membrane used is a biguanide-based polyvinylamine modified reverse osmosis membrane.

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