Nano zero valence iron-multistage anti-filter formula system is removed method and the device thereof of heavy metals in industrial wastewater
Technical field
The invention belongs to environmental technology field, relate to the purification techniques of heavy metal-containing waste water, be specially a kind of nano zero valence iron-multistage anti-filter formula system and remove method and the device of heavy metals in industrial wastewater.
Background technology
Metallic wastewater refers to the waste water containing heavy metal of discharging in the Industrial processes such as mining and metallurgy, machinofacture, chemical industry, electronics, instrument.Heavy metal wastewater thereby is the most serious to an environmental pollution and the mankind is endangered to one of maximum trade effluent, its water quality and quantity is relevant with production technique, principal pollutant comprise cadmium, nickel, mercury, zinc, copper, chromium, lead etc., and its content also can be by several even to thousands of mg/litre.Fast development along with domestic industry, a large amount of industrial sewages containing heavy metal enter water body, according to ASSOCIATE STATISTICS, show, within 2009, domestic ferrous metal mining and metallurgy industry discharge heavy metal containing sewage is 14.1 hundred million tons, 6.6 hundred million tons, non-ferrous metal mining and metallurgy industry sewage, 10.7 hundred million tons of electric mechanical industry sewage effluents, 4,000,000,000 tons of Electroplating Operations discharge electroplating wastewaters.And, since 2009, a barrage of outburst heavy metal contamination event, beaten alarm bell invariably, the control that heavy metal wastewater thereby pollutes is our the current problem that must face.
Generally speaking, the heavy metal in trade effluent is that various common methods can not be decomposed destruction, and can only shift their location and change their physics and chemistry form.If not treated, heavy metal-containing waste water enters lake, ocean in a large number, or enters in edatope, can be bioaccumulation and finally enter human body by food chain, the serious harm HUMAN HEALTH.In addition, heavy metal element toxicity is very large, generally only needs denier just can cause biological causing a disease.Therefore, a large amount of discharges of heavy metal are contaminate environment, the harm people's life and health not only, especially to a kind of waste of valuable heavy metal resources.
Due to this specific character, current heavy metal wastewater thereby forms two kinds of products after treatment, and the one, basically removed the processing water of heavy metal, the one, the enriched product of heavy metal.Heavy metal in general enriched product mostly has use value, should recycle as far as possible; There is no recovery value, harmless treatment in addition.Common mainly contains biochemical process, chemical precipitation method, electrolytic process, ion exchange method and membrane separation process etc. containing the heavy metal industrial effluent treatment process.Biochemical process investment and running cost are low, and treatment effect is good, but sludge quantity is large, and treatment effect affects by temperature and Cyanide in Waste Water compound etc., stable not; Chemical precipitation method produces a large amount of mud, can cause secondary pollution to environment; The electrolytic process treatment effect is not ideal enough; The cost such as ion exchange method and membrane separation process and energy consumption are high, equipment is complicated, the operating time is long and selectivity is low.
Therefore, how to design that a kind of more economical and its enriched product is easier to reclaim or the heavy metal-containing wastewater treatment method of harmless treatment is at present under the pressure of the problem solved.The effective removal of heavy metal in heavy metal-containing waste water that develops rapidly of the new technology that the novel material of take is leading provides new measure.The reducing power of Zero-valent Iron uniqueness and surface chemistry can efficiently be removed the heavy metal in water body.As far back as 1999, the result of study of Moller etc. showed, with the cadmium ion in the draining of micron order Zero-valent Iron removal persilicic rock, cupric ion etc., good removal effect is all arranged.Nano zero valence iron is the nano material of the first-generation for the environment remediation field, and the reducing power that it is unique and surface chemistry can be applied to heavy metal and efficiently remove.Research shows, adopts nano zero valence iron removal heavy metal speed of reaction far above common Zero-valent Iron material.Mallouk etc. be take the nano zero-valence iron material that polymer resin is carrier loaded diameter 10~30 nm and are removed Cr (VI) and Pb (II) in water, found that Cr (VI) is reduced into Cr (III), and Pb (II) is reduced into Pb (0).Although in this material, iron level is only 22.6%, speed of reaction is 30 times of common iron material, and two months later removal abilities remain 21 times of common iron powder.2008, the researchs such as Xiao-qin Li showed: at pH=4~8 o'clock nano zero valence iron, to the removal ability of Cr, be 180~50mgCr/g nano zero valence iron, the removal ability of the Cr of the lower micron iron of the same terms (100 order) is less than 4mgCr/g Fe.The nano zero valence iron dosage of 5g/L is processed 1000 mg/L Ni solution, and clearance is 65%, and the removal ability is 0.13 g Ni/g Fe(4.43 mequiv Ni (II)/g), much larger than other inorganic adsorbing materials such as kaolinites.
In sum, nano zero valence iron not only has high treatment effect, also have fabulous accumulation ability, and product is all to exist with metal simple-substance or metal hydroxides, be beneficial to very much recycling, in addition, the nano zero valence iron low price, the green non-secondary pollution of material, and process heavy metal-containing waste water or a kind of new method with it.Therefore, the nano zero valence iron technical finesse has larger application prospect containing heavy metal industrial effluent.
Summary of the invention
Purpose of the present invention is exactly for the deficiency containing the existing treatment technology of heavy metal industrial effluent and means existence, provide a kind of nano zero valence iron-multistage anti-filter formula system to remove method and the device of heavy metals in industrial wastewater, not only can remove the heavy metal in sewage, the pollution of minimizing to receiving water body, also realized the enrichment to heavy metal element, the recovery after being convenient to or innoxious simultaneously.
The nano zero valence iron that the present invention proposes-multistage anti-filter formula system is removed the method for heavy metals in industrial wastewater, and concrete steps are as follows:
Heavy metal-containing waste water is carried out to pre-treatment, pretreated waste water is passed into to staged reactor by the flow velocity of 0.01 ~ 0.5L/s, successively by the water distributor of every stage reactor, closely knit reaction zone, hybrid reaction district and settling section, after waste water passes through water distributor, waste water is uniformly distributed on the dividing plate cross section, the excessive nano zero valence iron that is positioned at closely knit reaction zone adsorbs most of heavy metal ion, in the hybrid reaction district, abundant hybrid reaction mainly occurs, utilize the suspended nano Zero-valent Iron further effectively to remove the residual gravity metal ion, settling section is realized the solid-liquid separation of nano zero valence iron and waste water, according to containing the different waste water of concentration of heavy metal ion, the hydraulic detention time of every stage reactor is 10-30 min, each stage reactor is by absorption or reduction and complexing and the disposable removal heavy metals in industrial wastewater of co-precipitation, the heavy metal of removing mainly is gathered on the nano zero valence iron particle of reactor compact zone, after the interior nano zero valence iron reaction of question response device is saturated, open bottom gate, reclaim and reacted nano zero valence iron and injected fresh nano zero valence iron, realize removal and the enrichment of heavy metal ion, and can continue to process waste water.
In the present invention, described waste water is one to multiple kind in zinc-containing water, copper-containing wastewater, nickel-containing waste water, cadmium wastewater or lead waste water.
In the present invention, the pre-treatment of waste water refers to: filter, precipitate and remove suspended impurity in trade effluent, make the industrial wastewater clarification, reduce the impact of interfering substance on follow-up nano zero valence iron activity.
In the present invention, described nano zero valence iron solid content is 20~80 g/L, and when question response is saturated, the mean load amount of nano zero valence iron is 0.5~10 g/L.
In the present invention, described nano zero valence iron median size is 30~70 nm, and specific surface area reaches 20~40 m
2/ g, unique nucleocapsid structure has the dual-use function of absorption and reduction.
In the present invention, described heavy metal in waste water refers at least one in zinc, copper, nickel, mercury, cobalt, cadmium or lead.
In the present invention, the concentration of heavy metal ion of described waste water is below 500mg/L.
The device that the method for the nano zero valence iron proposed in the present invention-multistage anti-filter formula system removal heavy metals in industrial wastewater is used, described device comprises that two to three reactor, every stage reactor is the containment cylinder structure, comprise water distributor 3 from bottom to top, closely knit reaction zone 4, hybrid reaction district 6 and settling section 7, every stage reactor bottom is provided with water-in 2, top is provided with water outlet 9, be evenly distributed with water distribution mouth 14 and water distribution branch pipe 16 in water distributor, closely knit reaction zone 4 top one sides are provided with nano zero valence iron import 5, the bottom opposite side is provided with nano zero valence iron outlet 10, be provided with dividing plate 15 in closely knit reaction zone 4, to separate the nano zero valence iron of filling, bottom one side in hybrid reaction district is provided with wash-down water import 11, and settling section 7 top one sides are provided with wash-down water outlet 8, water-in and water-out when cleaning, the water outlet of first step reactor connects the water-in of second stage reactor by pipeline, the like to third stage reactor, the water-in of first step reactor is waterwater entrance, the outlet that the water outlet of last step reactor is processed waste water.
In the present invention, the ratio of the diameter of section of described every stage reactor and height is 1:6 ~ 1:10, and the ratio of closely knit reaction zone diameter of section and height is 1:2 ~ 1:4.
In the present invention, the closed reactor progression that system is used is determined on a case-by-case basis.
The present invention be take nano zero valence iron as core processing unit, by mixing with nano zero valence iron containing heavy metal industrial effluent after pretreated, by airtight anti-filter formula reactor, fully processes.
In the present invention, to standard potential far above the metal of iron as Cu (II ,+0.34 V), Ag (I ,+0.80 V), nano zero valence iron is mainly removed in the reduction mode; For standard potential and iron approach or far below the metal of iron as Cd (II ,-0.40V), Zn (II ,-0.76 V), nano zero valence iron is mainly to remove by the mode of absorption and surface complexation to these metal target; Metal for standard potential a little more than iron, as Ni (II ,-0.24V), Pb (II ,-0.13V), nano zero valence iron adopts absorption and reduction dual mechanism to be removed.
To E
0(M)≤E
0(Fe) (M means Zn to situation
2+, Cd
2+, Cr
2O
7 2-Deng), nano zero valence iron is assembled heavy metal by the mode of absorption; To E
0(M) approach or be a bit larger tham E
0(Fe) (M means Ni to situation
2+, Pb
2+Deng), nano zero valence iron is separated heavy metal by the mode of absorption or reduction; To E
0(Fe)≤E
0(M) (M means Ag to situation
+, Cu
2+, Hg
2+Deng), nano zero valence iron is removed heavy metal by reduction reaction.With Cr
2O
7 2-For example, the core texture Fe of nano zero valence iron
0By the Cr(VI) be reduced into the Cr(III) after, the Cr(III that the FeOOH shell absorption that outside coats generates) form alloy hydroxide (Cr
0.67Fe
0.33) (OH)
3Passivation layer, simultaneously with Pb
2-For example, reaction formula is described below:
3Fe
0+?Cr
2O
7 2-?+7H
2O?=?3Fe
2++2Cr(OH)
3+?8OH
-
≡FeOH+?Cr
2O
7 2-→≡Fe-?Cr
2O
7 -+OH
-
2Fe
0 (s)?+3Pb(C
2H
3O
2)2+4H
2O?→?3Pb
0 (s)+2FeOOH
(S)+4HC
2H
3O
2?+2H
+
Mode by the Reduce and adsorption heavy metal in mixed solution is the most at last removed.
Beneficial effect of the present invention:
The present invention utilizes the nano zero valence iron technology, adopts the characteristic of nano zero valence iron absorption and reduction, with nano zero valence iron, heavy metal enrichment from trade effluent is removed.Whole system is simple in structure, practical, and energy consumption is low, cost is low.
The accompanying drawing explanation
Fig. 1 is nano zero valence iron model structure schematic diagram.
Fig. 2 is system diagram of the present invention.
The cross-sectional view that Fig. 3 is water distributor of the present invention and closely knit reaction zone.Interim: the cross-sectional view that A-A is water distributor, the cross-sectional view that B-B is closely knit reaction zone.
The schematic diagram that Fig. 4 is water distributor of the present invention and closely knit reaction zone.
The schematic diagram that Fig. 5 is the closely knit reaction zone of the present invention.
Fig. 6 is embodiment 1 removal effect figure.
Number in the figure: 1 is nano zero valence iron, and 2 is water-in, and 3 is water distributor, 4 is closely knit reaction zone, and 5 is the nano zero valence iron entrance, and 6 is the hybrid reaction district, 7 is settling section, and 8 is the wash-down water outlet, and 9 is water outlet, 10 is the nano zero valence iron outlet, and 11 is the wash-down water entrance, and 12 is second stage reactor, 13 is third stage reactor, and 14 is water distribution mouth, and 15 is dividing plate, 16 is water distribution branch pipe, and 17 is first step reactor.
Embodiment
Further illustrate the specific embodiment of the present invention below in conjunction with accompanying drawing.
Embodiment 1:
The nano zero valence iron that the present invention adopts is FeCl
3Solution and NaBH
4Solution mixes the generation redox reaction and makes, particle size range 1~100 nm, and median size 30~70 nm, specific surface area is 20~40 m
2/ g, as the structural models figure of Fig. 1 nano zero valence iron, typical nucleocapsid dual structure, inside is closely knit Zero-valent Iron, plays reductive action; Outer ring coats the ferric oxide (or FeOOH) of thin layer, plays adsorption.Synthetic stand-by nano zero valence iron adds the organic reagents such as ethanol, Virahol to make into the closely knit reaction zone that flow-like enters closed reactor, and this wet nano zero valence iron solid content is between 20~80 g/L, and nano zero valence iron must be kept under oxygen-free environment.
Method and the device thereof of lower concentration heavy metal-containing waste water in a kind of nano zero valence iron-multistage anti-filter formula system removal, the application of the nanomaterial science that nano zero valence iron is the major function unit in Industrial Wastewater Treatment, the manageable wastewater flow rate of average every gram nano zero valence iron is 0.1~2 L, heavy metal concentration is below 500mg/L, be 10 ~ 30 min duration of contact, make closed reactor make its abundant contact reacts, absorption and the restoring function of performance nano zero valence iron, realize effective gathering of heavy metal, reach treatment effect.
As shown in Fig. 2 to Fig. 5, the invention provides columniform second stage reactor 12 and third stage reactor 13, water distributor 3 through pretreated trade effluent by first step reactor 17 from enter successively closely knit reaction zone 4, hybrid reaction district 6, settling section 7, then enter second stage reactor 12.After water distributor 3 by second stage reactor 12, waste water is uniformly distributed on cross section, and enter the closely knit reaction zone 4 separated by dividing plate 15, in closely knit reaction zone 4, nano zero valence iron is filled closely, most of heavy metal ion is adsorbed in rapid absorption reaction when main generation nano zero valence iron is greatly excessive, enters afterwards main abundant hybrid reaction, the last solid-liquid separation that realizes nano zero valence iron and waste water at settling section 7 of occurring in hybrid reaction district 6.According to containing the different waste water of concentration of heavy metal ion, the residence time of single-stage reactor, reactor progression can be the 2-3 level between 10-30min.After the processing through after a while, the nano zero valence iron adsorptive capacity has reached saturated, can open nano zero valence iron import 5 and nano zero valence iron outlet 10, changes fresh nano zero valence iron and realizes the continuation of processing.The nano zero valence iron reclaimed is the enriched heavy metal element, is convenient to next step resource utilization and harmless treatment.
Get certain Electroplate Factory's plating shop exit electroplating wastewater stoste, at first electroplating wastewater stoste is carried out to pre-treatment: add a certain amount of PAM flocculation agent, first rapid stirring 1~2 min mixes the flocculation agent added in solution, then reduce stirring velocity, slowly stir electroplating wastewater 30~60 min, make the suspended impurity in electroplating wastewater stoste condense into wadding, after having flocculated, stop stirring, electroplating wastewater is staticly settled to 1~3 h, use filter paper filtering after having precipitated, obtain the electroplating wastewater of clarification after filter.Pretreated electroplating wastewater is containing ZnSO
4400~500 mg/L, pH is between 2~5.The present embodiment nano zero valence iron used is by 0.045 mol/LFeCl
3Solution and 0.25 mol/LNaBH
4The preparation of equal-volume hybrid reaction, the nano zero valence iron ethanolic soln solid content made is 40-50 g/L, is kept at N
2Under atmosphere.
The present embodiment reaction unit main body is columniform closed reactor, the employing synthetic glass is made, and multistage anti-filter system comprises 2 grades of closed reactors, and wherein the ratio of every stage reactor diameter of section and height is 1:6, the ratio of closely knit reaction zone diameter of section and height is 1:4, and be 10 min every grade of duration of contact.First by nano zero valence iron entrance 5, inject highly concentrated nano Zero-valent Iron fluid 10 ~ 20 g(net contents that prepared before reaction starts), former electroplating wastewater is diluted to containing ZnSO
450~100 mg/L, regulate pH to 5~7.Electroplating wastewater, from reaction unit bottom waterwater entrance 2, enters every stage reactor, finally by second stage reactor water outlet, obtains clarification and effluent.Single reaction treatment waste water 10 ~ 100 L wherein.
After the processing that different time points obtains, the ICP test is directly carried out in the electroplating wastewater water outlet after routine is cleared up, and according to the concentration of adding nano zero valence iron front and back heavy metal out of electroplating wastewater, the average removal rate that calculates Zn approaches 100%.
Embodiment 2:
Get certain copper mine factory wastewater effluent stoste, at first copper mine waste water stoste is carried out to pre-treatment: add a certain amount of PAM flocculation agent, first rapid stirring 1~2 min mixes the flocculation agent added in solution, then reduce stirring velocity, slowly stir mining industry waste water 30~60 min, make the suspended impurity in copper mine waste water stoste condense into wadding, after having flocculated, stop stirring, electroplating wastewater is staticly settled to 1~3 h, use filter paper filtering after having precipitated, obtain the electroplating wastewater of clarification after filter.Pretreated mining industry waste water is containing Cu
2+200~800 mg/L, Ni
2+50 ~ 100 mg/L, Zn
2+10 ~ 30 mg/L, pH is between 7~8.5.The present embodiment nano zero valence iron used is by 0.050 mol/LFeCl
3Solution and 0.25 mol/LNaBH
4The preparation of equal-volume hybrid reaction, the nano zero valence iron aqueous isopropanol solid content made is 20-30 g/L, is kept at N
2Under atmosphere.
The present embodiment reaction unit main body is columniform closed reactor, the employing synthetic glass is made, multistage anti-filter system comprises 3 grades of closed reactors, wherein the ratio of every stage reactor diameter of section and height is 1:6, the ratio of closely knit reaction zone diameter of section and height is 1:4, and every stage reactor duration of contact is 10 min.First by nano zero valence iron entrance 5, inject highly concentrated nano Zero-valent Iron fluid 10 ~ 20 g(net contents that prepared before reacting beginning), former copper mine wastewater dilution is extremely contained to Cu
2+50~200 mg/L, Ni
2+10 ~ 25 mg/L, Zn
2+2 ~ 5 mg/L, regulate pH to 5~7.Copper mine waste water, from reaction unit bottom waterwater entrance 2, enters every stage reactor, finally by third stage reactor, obtains clarification and effluent.Single reaction treatment waste water 10 ~ 100 L wherein.
After the processing that different time points obtains, the ICP test is directly carried out in the electroplating wastewater water outlet after routine is cleared up, according to the concentration of adding nano zero valence iron front and back heavy metal out of electroplating wastewater, calculate the Cu average removal rate and keep more than 95%, the average removal rate of Ni, Zn approaches 100%.
Embodiment 3:
Get certain Electroplate Factory's plating shop exit electroplating wastewater stoste, at first electroplating wastewater stoste is carried out to pre-treatment: add a certain amount of PAM flocculation agent, first rapid stirring 1~2min mixes the flocculation agent added in solution, then reduce stirring velocity, slowly stir electroplating wastewater 30~60min, make the suspended impurity in electroplating wastewater stoste condense into wadding, after having flocculated, stop stirring, electroplating wastewater is staticly settled to 1~3h, use filter paper filtering after having precipitated, obtain the electroplating wastewater of clarification after filter.Pretreated electroplating wastewater is containing Pb, Ni 300~800mg/L, and pH is between 6~8.The present embodiment nano zero valence iron used is by 0.050mol/L FeCl
3Solution and 0.25 mol/L NaBH
4The preparation of equal-volume hybrid reaction, the nano zero valence iron aqueous isopropanol solid content made is 50-80 g/L, is kept at N
2Under atmosphere.
The present embodiment reaction unit main body is columniform closed reactor, the employing synthetic glass is made, and multistage anti-filter system comprises 3 grades of closed reactors, and wherein the ratio of every stage reactor diameter of section and height is 1:6, the ratio of closely knit reaction zone diameter of section and height is 1:4, and be 30 min every grade of duration of contact.First by nano zero valence iron entrance 5, inject highly concentrated nano Zero-valent Iron fluid 20 ~ 40 g(net contents that prepared before reaction starts), former electroplating wastewater is diluted to containing Pb, Ni 100 mg/L, pH remains unchanged.Electroplating wastewater, from reaction unit bottom waterwater entrance 2, enters every stage reactor, finally by third stage reactor water outlet, obtains clarification and effluent.Single reaction treatment waste water 10 ~ 100 L wherein.
Electroplating wastewater water outlet after processing is cleared up after adding the nitric acid acidifying and is carried out the ICP test through routine, measures two heavy metal species content.According to the concentration of adding nZVI front and back heavy metal out of electroplating wastewater, the clearance that the clearance of calculating Pb reaches 80%~90%, Ni reaches 90%~95%.