CN116119851A - Method for improving reaction speed of zero-valent iron particles and iron sheets and heavy metal ions - Google Patents
Method for improving reaction speed of zero-valent iron particles and iron sheets and heavy metal ions Download PDFInfo
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- CN116119851A CN116119851A CN202211102649.5A CN202211102649A CN116119851A CN 116119851 A CN116119851 A CN 116119851A CN 202211102649 A CN202211102649 A CN 202211102649A CN 116119851 A CN116119851 A CN 116119851A
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 515
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 230
- 239000002245 particle Substances 0.000 title claims abstract description 146
- 229910001385 heavy metal Inorganic materials 0.000 title claims abstract description 128
- 238000000034 method Methods 0.000 title claims abstract description 58
- 150000002500 ions Chemical class 0.000 title claims abstract description 44
- 230000036632 reaction speed Effects 0.000 title claims abstract description 8
- 239000002351 wastewater Substances 0.000 claims abstract description 124
- 239000007788 liquid Substances 0.000 claims abstract description 85
- 239000002699 waste material Substances 0.000 claims abstract description 71
- 238000003756 stirring Methods 0.000 claims abstract description 58
- 239000002253 acid Substances 0.000 claims abstract description 27
- 159000000000 sodium salts Chemical class 0.000 claims abstract description 20
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000010814 metallic waste Substances 0.000 claims abstract description 14
- IXCSERBJSXMMFS-UHFFFAOYSA-N hcl hcl Chemical compound Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000005303 weighing Methods 0.000 claims abstract description 8
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 66
- 238000001914 filtration Methods 0.000 claims description 35
- 239000011780 sodium chloride Substances 0.000 claims description 33
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 26
- 238000004064 recycling Methods 0.000 claims description 21
- 238000002791 soaking Methods 0.000 claims description 19
- 239000011734 sodium Substances 0.000 claims description 15
- 235000013980 iron oxide Nutrition 0.000 claims description 14
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 239000002244 precipitate Substances 0.000 claims description 9
- 125000004122 cyclic group Chemical group 0.000 claims description 5
- 238000010306 acid treatment Methods 0.000 claims description 4
- 238000011221 initial treatment Methods 0.000 claims description 3
- 150000002736 metal compounds Chemical class 0.000 claims description 3
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 claims description 2
- 239000010842 industrial wastewater Substances 0.000 abstract description 8
- 239000000243 solution Substances 0.000 description 58
- 239000011651 chromium Substances 0.000 description 47
- 239000013049 sediment Substances 0.000 description 33
- 238000011282 treatment Methods 0.000 description 22
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- 230000008569 process Effects 0.000 description 8
- 238000011084 recovery Methods 0.000 description 8
- 238000006722 reduction reaction Methods 0.000 description 7
- 238000011276 addition treatment Methods 0.000 description 6
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- 238000009388 chemical precipitation Methods 0.000 description 5
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- 230000009467 reduction Effects 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 150000001450 anions Chemical class 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
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- 241000209094 Oryza Species 0.000 description 2
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- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 235000013339 cereals Nutrition 0.000 description 2
- 229910000423 chromium oxide Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910003439 heavy metal oxide Inorganic materials 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
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Classifications
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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
-
- 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
-
- 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
- C02F1/48—Treatment of water, waste water, or sewage with magnetic or electric fields
-
- 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
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/206—Manganese or manganese compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention relates to a method for improving the reaction speed of zero-valent iron particles and iron sheets and heavy metal ions, which comprises the following steps: 1) Adding 0.5-50mmol/L sodium salt into the heavy metal waste liquid to be treated; 2) Weighing iron particles or iron sheets according to the mass content of 5g-50g/L, and adding sulfuric acid (H) 2 SO 4 ) Or immersing in hydrochloric acid (HCl) solution, pouring out acid solution, immediately adding iron particles or iron sheets into the heavy metal waste obtained by adding sodium salt in step 1)In the liquid; 3) Stirring the waste liquid treated in the step 2) until the heavy metal content in the waste liquid is not changed. The method can remove heavy metals in industrial wastewater from the wastewater at one time.
Description
Technical Field
The invention relates to a method for removing heavy metals in waste liquid, in particular to a method for improving the reaction speed of zero-valent iron particles and iron sheets and heavy metal ions, belonging to an innovative technology of the method for improving the reaction speed of the zero-valent iron particles and the iron sheets and the heavy metal ions.
Background
Along with the development of social economy, more and more heavy metals are discharged into the environment and finally enter the human body through food and water, thereby seriously affecting the health of the human body.
At present, the traditional method for removing heavy metal elements from wastewater mainly comprises the following steps: chemical precipitation, ion exchange, co-flocculation, froth flotation, membrane filtration, electrochemical treatment, solution extraction, electrolysis, chemical oxidation, reverse osmosis, etc. The chemical precipitation method has the advantages of simple process, low investment cost, economical materials, basically removing all heavy metal elements from the wastewater and large wastewater treatment capacity, so that the chemical precipitation method is a main method for treating industrial wastewater containing high-concentration heavy metal elements; the above methods are not suitable for treating large amounts of industrial wastewater containing heavy metal elements at high concentrations, because of high cost, because of insufficient treatment scale, because of other disadvantages such as low treatment speed, etc.
The chemical precipitation method is to react a chemical precipitant with heavy metal ions to generate heavy metal oxides, heavy metal sulfides, heavy metal complexes and other precipitates, and then to separate most of the precipitates by filtration, floatation or other methods, wherein the fine precipitates still remain in the wastewater. Thus, the chemical precipitation method for treating heavy metal wastewater is not completely clean, chemical reagents and the like still need cost, the treatment efficiency is low due to long precipitation time of the precipitate, and the treatment process is complicated.
At present, zero-valent iron (Fe 0 ) The method for removing the heavy metals in the wastewater by the nano particles greatly simplifies the process of removing the heavy metals in the wastewater, reduces the cost and has higher removal rate. The principle is that Fe is utilized 0 Reacts with heavy metal ions to generate Fe 2+ /Fe 3+ And magnetic coprecipitates of heavy metal oxides or hydroxides. But due to nano Fe 0 Surface appearance of particlesIs easy to oxidize to form iron oxide to prevent electrons from migrating to nano Fe 0 The particle surface reacts with heavy metal, and nano Fe 0 The particles are easy to agglomerate and have poor recovery performance, so that zero-valent iron (Fe 0 ) The application of the nanoparticles is hindered. Later, millimeter-sized iron particles with good recovery performance are adopted to remove Cr in simulated wastewater 6+ Good results were obtained with stirring as follows: cr with 2mg/L in the waste liquid is added in 80 minutes at a stirring rate of 360rpm 6+ Dissolved Cr 6+ Reducing the emission standard. The method adopts millimeter-sized iron particles to ensure the recovery of the iron particles. Although due to its specific surface area, it is larger than nano Fe 0 The particles are several orders of magnitude smaller, fe 0 Reduction of Cr 6+ The active sites of (a) are greatly reduced, but Cr is removed in the above work 6+ Is still equal to nano Fe 0 Particle removal of Cr 6+ Is equivalent in efficiency. The reason is that Cr is stirred 6+ Greatly improves Fe in the wastewater of (2) 0 Particle removal of Cr 6+ Is not limited to the above-described embodiments. Fe of millimeter size can be improved under stirring 0 Particulate removal of heavy metals Cr 6+ The principle of the velocity is that, due to the disturbance of the electric double layer at the surface iron oxide/solution interface and the ions in the solution during stirring, the disturbed charge generates an induced electromagnetic field which impedes the reaction of Fe at the surface iron oxide 0 The electrons in the electron pair generate Lorentz magnetic force. This force increases the probability of the electrons passing over the surface iron oxide, making it more likely to migrate to Fe 0 Boundary surface of grain solution and Cr 6+ And (3) reacting. So that stirring increases the reduction of Cr by electrons 6+ The efficiency of forming trivalent chromium oxide is improved, i.e. Fe 0 Heavy metal Cr removal 6+ Is a rate of (a). But Fe obtained by such a method 0 Heavy metal Cr removal 6+ The rate is still not satisfactory for the application, and the surface iron oxide and deposited reaction product are treated once to give Fe 0 Heavy metal Cr removal 6+ The rate is greatly reduced. Therefore, the iron particles need to be fished out after each use, and the oxide and sediment on the surface of the iron particles are washed out by acid.
Disclosure of Invention
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for improving the reaction rate of zero-valent iron particles and iron pieces with heavy metal ions. The method can remove heavy metals in industrial wastewater from the wastewater at one time.
The technical scheme of the invention is as follows: the invention relates to a method for improving the reaction speed of zero-valent iron particles and iron sheets and heavy metal ions, which comprises the following steps:
1) Adding 0.5-50mmol/L sodium salt into the heavy metal waste liquid to be treated;
2) Weighing iron particles or iron sheets according to the mass content of 5g-50g/L, and adding sulfuric acid (H) 2 SO 4 ) Or pouring out the acid solution after soaking in hydrochloric acid (HCl) solution, and immediately adding iron particles or iron sheets into the heavy metal waste liquid obtained by adding sodium salt in the step 1); if the iron sheet is the iron sheet, the iron sheet is bent into an arc shape facing the stirrer, and the iron sheet is fixed at a place where the stirrer cannot contact, so that the relative speed between the waste liquid and the iron sheet caused by stirring is ensured.
3) Stirring the waste liquid treated in the step 2) until the heavy metal content in the waste liquid is not changed.
The invention can treat the heavy metal sewage with industrial emission level to the emission standard basically by one-time treatment. The method can greatly improve the performance of treating industrial wastewater by iron particles or iron sheets with the size of more than millimeter, and can remove heavy metals in the industrial wastewater from the wastewater at one time. The iron particles or the iron sheets can be continuously used for 20 times without pickling in the middle. Thus greatly reducing the cost of treating heavy metal wastewater. In addition, the invention can use the iron sheet with the size of rice grade, and the use of the rice grade iron sheet ensures the recovery and the operation simplicity of the iron sheet to the maximum extent, and avoids the secondary pollution of wastewater by iron. In summary, the invention ensures the realization of zero-valent iron from research to real application. Therefore, the method has remarkable innovation and application value.
Drawings
Fig. 1 is a schematic diagram of the present invention: (a) Cations, (b) influence of anions on movement of electrons in the iron particles upon stirring. In FIG. 1, iron particles are indicated by iron turning, e - Representing electronsRotation direction is the direction of movement of the solution after it has been stirred.
Is indicative of positive charge->
The negative charge, v, the movement velocity of electrons, F, the lorentz force received by electrons in the iron particles, "×" indicates the direction inward from the vertical paper, and "+" indicates the direction outward from the vertical paper.
FIG. 2 shows that Cr having a concentration of 2mg/L is removed by iron particles having an average size of 1 mm. Times.1 mm at a stirring speed of 350rpm 6+ Cr in waste water 6+ The removal rate of CNa added at 0.5mmol/L versus no CNa was compared to a time plot.
FIG. 3 shows that Ni at a concentration of 2mg/L was removed by 1 m.times.1mX 1mm iron pieces at a stirring speed of 500rpm 2+ Ni in wastewater 2+ The removal rate at the time of adding 50mmol/L NaCl was compared with the time of adding no NaCl.
FIG. 4 shows that Co having a concentration of 2mg/L is removed by iron particles of 0.15mX0.21mX5.0 mm at a stirring speed of 500rpm 2+ Co in wastewater 2+ 25mmol/L NaNO was added 3 And without adding NaNO 3 The removal rate at that time is compared with a time chart.
FIG. 5 shows that Zn was removed at a concentration of 2mg/L by using 1 mm. Times.0.5 m.times.0.6 m iron pieces at a stirring speed of 350rpm 2+ Zn in waste water 2+ When 10mmol/L Na is added 2 SO 4 And not adding Na 2 SO 4 The removal rate at that time is compared with a time chart.
FIG. 6 shows that Cd having a concentration of 2mg/L was removed by 1.8mm.times.3mm.times.7mm iron particles at a stirring speed of 50rpm 2+ Cd in wastewater 2+ The removal rate versus time was compared with CNa added at 1.5mmol/L and without CNa.
FIG. 7 shows that Pb having a concentration of 2mg/L was removed with iron particles of-3.1 mm to 4mm to 9.6mm at a stirring speed of 400rpm 2+ Pb in wastewater 2+ The removal rate at 40mmol/L NaCl was compared with the time plot without NaCl.
FIG. 8 is a diagram ofCu with a concentration of 2mg/L was removed with iron particles of 1.1 mm. Times.1.6 mm. Times.3.2 mm at a stirring speed of 390rpm 2+ Cu in wastewater 2+ When 20mmol/L NaNO is added 3 And without adding NaNO 3 The removal rate at that time is compared with a time chart.
FIG. 9 shows that Se having a concentration of 2mg/L was removed with iron particles of 1.1mm to 1.6mm to 3.2mm at a stirring speed of 420rpm 4+ Se in wastewater 4+ 45mmol/L NaNO was added 3 And without adding NaNO 3 The removal rate at that time is compared with a time chart.
FIG. 10 shows Te with a concentration of 2mg/L for iron particle removal of 0.9mm to 1.3mm to 2.7mm at a stirring speed of 250rpm 3+ Te in wastewater 3+ 25mmol/L Na was added 2 SO 4 And not adding Na 2 SO 4 The removal rate at that time is compared with a time chart.
FIG. 11 shows Mn at a stirring speed of 350rpm at a concentration of 2mg/L with iron particles removed by 0.9mm X1.3 mm X2.7 mm 2+ Mn in wastewater 2+ The removal rate versus time was compared with 15mmol/L CNa added versus no CNa added.
FIG. 12 shows that Sn having a concentration of 2mg/L is removed by iron particles having an average size of 0.9mm X1.3 mm X2.7 mm at a stirring speed of 250rpm 2+ Sn in wastewater 2+ The removal rate was compared with a time chart of the addition of 42mmol/L NaCl and the absence of NaCl.
FIG. 13 shows the removal of Cr from iron particles in wastewater containing CNa 6+ The "removal rate versus time" for 20 cycles, the bar graph for each maximum removal rate for 20 cycles of removal in fig. 13 (b) (a), and the "removal rate versus time" for 5 cycles of no salt in fig. 13 (c).
FIG. 14 heavy metal-removed mixed wastewater (Cr) with iron particles having an average size of 0.5 mm. Times.1.1 mm. Times.3.5 mm at a stirring speed of 350rpm 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 3+ 、Mn 2+ 、Sn 2+， 0.2mg/L each) of CNa with 38mmol/L added thereto and the removal rate of each heavy metal ion without adding CNa were compared with a time chart.
FIG. 15 shows removal of heavy metal-containing wastewater (Cr) by removing heavy metal-containing wastewater with iron particles having an average size of 0.61mm X1.0 mm X3.4 mm at a stirring speed of 430rpm 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 3+ 、Mn 2+ 、Sn 2+， 0.2mg/L each) of NaCl at 27mmol/L was compared with the time chart of the removal rate of each heavy metal ion without NaCl.
Detailed Description
The method for improving the reaction speed of the zero-valent iron particles and the iron sheets and the heavy metal ions comprises the following steps:
1) Adding 0.5-50mmol/L sodium salt into the heavy metal waste liquid to be treated;
2) Weighing iron particles or iron sheets according to the mass content of 5g-50g/L, and adding sulfuric acid (H) 2 SO 4 ) Or pouring out the acid solution after soaking in hydrochloric acid (HCl) solution, and immediately adding iron particles or iron sheets into the heavy metal waste liquid obtained by adding sodium salt in the step 1); 3) Stirring the waste liquid treated in the step 2) until the heavy metal content in the waste liquid is not changed.
In the step 1), the sodium salt is CH 3 COONa、NaCl、NaNO 3 、Na 2 SO 4 Any one of them.
In the step 1), the heavy metal waste liquid contains one or more of the following heavy metal ions: cr (Cr) 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 4+ 、Mn 2+ 、Sn 2+ 。
In the step 2), iron particles or iron pieces with the average size of each dimension ranging from 0.5mm to 1m are weighed.
In the step 3), if the iron sheet is formed, the direction of the iron sheet facing the stirrer is curved into an arc, and the iron sheet is fixed at a place where the stirrer is not contacted, so that the relative speed between the waste liquid and the iron sheet caused by stirring is ensured.
In the step 2), the iron particles or the iron flakes are added with sulfuric acid (H) with the concentration of 0.5 to 5 percent 2 SO 4 ) Or immersing in hydrochloric acid (HCl) solution, and pouring out the acid solution.
In the step 2), the iron particles or the iron pieces are put into sulfuric acid (H) with the concentration of 0.5 to 5 percent 2 SO 4 ) Or soaking in hydrochloric acid (HCl) solution for 1-10 min, and pouring out the acid solution.
In the step 3), the waste liquid treated in the step 2) is stirred according to the rotating speed in the range of 50-600rpm until the heavy metal content in the waste liquid is not changed.
After the step 3), the iron particles or the iron sheets are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 1-5 hours, the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
When the recovered iron particles or iron flakes are to be reused, the steps 1) to 4) are repeated, and the heavy metal compounds adsorbed on the surfaces of the iron particles and the iron oxides automatically fall off to become precipitates in the cyclic acid treatment process, so that the iron particles or iron flakes are recovered as before. If the heavy metal wastewater after the primary treatment does not reach the corresponding heavy metal wastewater discharge standard, treating the iron particle acid again to treat the heavy metal wastewater which does not reach the standard, and circulating until reaching the standard.
The invention adopts the iron particles with the size of more than millimeter and good recovery performance, especially the meter-grade iron sheet to remove heavy metals in the simulated wastewater, thereby solving the problems of nano Fe 0 The problems of heavy metal agglomeration and difficult recovery in the reduction wastewater are solved, and the method of adding salt and stirring is adopted to improve Fe 0 The rate of reduction of heavy metals in wastewater. Which is a kind ofPrinciple ofBy disturbing the electric double layer at the surface iron oxide/solution interface and the ions in the solution during stirring, the disturbed charge generates an induced electromagnetic field that impedes the formation of Fe at the surface iron oxide 0 The electrons in the electron pair generate Lorentz magnetic force. This force increases the probability of the electrons crossing the surface iron oxide barrier, making them more likely to migrate to Fe 0 Boundary surface of grain solution and Cr 6+ And (3) reacting. So that stirring increases the reduction of Cr by electrons 6+ The efficiency of forming trivalent chromium oxide is improved, i.e. Fe 0 Heavy metal Cr removal 6+ Is a rate of (a). The invention is realized by adding sodium salt (CH) 3 COONa、NaCl、NaNO 3 、Na 2 SO 4 The method comprises the steps of carrying out a first treatment on the surface of the Concentration range: 0.5-50 mmol/L) to increase the charged ions in the solution, thereby increasing the induced electromagnetic field generated when the solution is stirred. Thus increasing the Lorentz force of electrons blocked by iron oxide, etc., and increasing Fe 0 The surface of the iron particle or the iron sheet participates in the electron for reducing the heavy metal ions, so that the rate of removing the heavy metals in the wastewater is improved. The method of the invention is effective for the following aspects: (I) With Fe 0 Removing ions respectively containing one of the following heavy metal ions in the solution: cr (Cr) 6+ 、Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 4+ 、Mn 2+ 、Sn 2+ The method comprises the steps of carrying out a first treatment on the surface of the (II) removing all heavy metal ions in the mixed solution of a plurality of heavy metal ions in the heavy metal ions. Improvement of Fe by acid treatment after each treatment of heavy metals 0 Is a cyclic performance of (c).
The detailed mechanism of the method of the invention is as follows: adding sodium salt (CH) in addition to iron particles (each dimension of which is 0.5mm-1 m) into heavy metal wastewater solution according to the amount of 5-50g/L 3 COONa、NaCl、NaNO 3 、Na 2 SO 4 The method comprises the steps of carrying out a first treatment on the surface of the Concentration range: 0.5-50 mmol/L) and the method of stirring (stirring speed range: 50-600 rpm). The addition of sodium salt increases the amount of charged ions in the solution, thereby increasing the electromagnetic induction and ultimately increasing the lorentz force experienced by the electrons. The method can increase the speed of removing heavy metals in wastewater by multiple times.
The specific mechanism is shown in FIG. 1 (a) (b). After the sodium salt is dissolved in the wastewater, cations and anions are present. Both ions will be specific to Fe 0 Heavy metal Cr removal 6+ The increase in rate is effective. Fig. 1 (a) shows the effect of cations, and fig. 1 (b) shows the effect of anions. As shown in fig. 1 (a), the stirring direction is assumed to be clockwise when viewed from the top of the vessel. The movement direction of the cations is the same as the rotation direction of the solution. The movement speed of the iron particles in the solution is also the same as that of the solution rotation. According to the rightThe hand screw rule creates an electromagnetic field (shown by "x") that is perpendicular to the paper surface and inward. The iron particles move, and electrons in the iron particles move similarly. The macroscopic motion speed of electrons in the iron particles is the same as the motion speed of the iron particles. Electrons in the iron particles generate Lorentz force F under the action of the electromagnetic field. According to the left hand rule, the direction of F is as shown in FIG. 1 (a), with the effect of pulling electrons out of the iron particles. Similarly, the anions shown in fig. 1 (b) were analyzed to have an effect of pulling out electrons near the surface of the iron particles from the iron particles under clockwise stirring. Only the electrons pulled out are in a different direction from those pulled out in the case of cationic stirring, and the electrons in the iron particles are pulled out of the other surface. But either side pulls electrons from the surface of the iron particles into contact with the solution. Similarly, the final effect of stirring in either direction is to pull electrons out of the surface of the iron particles. Can all improve Fe 0 Rate of heavy metal removal. Fe (Fe) 0 The heavy metal removal rate is improved, fe 0 Reduced time to oxidation, fe 0 The oxidation time in the process of reducing heavy metals is reduced, the iron oxide film layer is thinned, and Fe 0 Heavy metal Cr removal 6+ The rate is thus increased. For example, 2mg/L of Cr is originally added at a time 6+ The Cr content in the solution was reduced to the discharge standard for 80 minutes (stirring rate 360 rpm), now only 8 minutes (stirring rate 360 rpm). Fe (Fe) 0 The film thickness of the oxidized iron oxide was the same as that accumulated in 10 cycles in 80 minutes. Fe due to oxide formation in the original 1-cycle 0 Heavy metal Cr removal 6+ The rate decrease, under the method of the present invention, may take 10 times before the same amplitude is decreased. Therefore, fe can be improved 0 Heavy metal Cr removal 6+ Is a cyclic performance of (c). The innovation point of the invention is that a small amount of sodium salt is added into the wastewater solution, the sodium salt is not reduced by iron, but more charged ions in the solution can be provided, so that the induced electromagnetic field generated under the condition of stirring is larger, thereby leading the electrons in the iron particles (the surface of which is provided with oxide to form potential barrier and prevent the electron migration in the iron particles from undergoing reduction reaction with heavy metal) to be excited by larger electromagnetic waves, and the reduction reaction of the surface of the iron particles and the heavy metal is more easily achieved by crossing the potential barrier of the surface oxide, thereby the invention has the advantages of simple process, low cost, convenient operation, and the likeGreatly improves the rate of removing heavy metals by the iron particles or the iron sheets with the size of millimeter or more and improves the cycle performance.
The specific operation method of the invention is as follows: (1) 0.5-50mmol/L sodium salt (CH) 3 COONa、NaCl、NaNO 3 、Na 2 SO 4 ) Is added into the heavy metal waste liquid to be treated (comprising one or more of the following heavy metal ions: cr (Cr) 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 4+ 、Mn 2+ 、Sn 2+ ) Is a waste water of the sewage treatment system. (2) Weighing iron particles or iron flakes with average size of 0.5mm-1m in each dimension according to mass content of 5g-50g/L, adding sulfuric acid (H) with concentration of 0.5% -5% 2 SO 4 ) Or immersing in hydrochloric acid (HCl) solution for 1-10 min, pouring out the acid solution, and immediately adding iron particles or iron sheets into the heavy metal waste liquid treated in the step (1) (namely, after adding sodium salt).
In the case of an iron sheet, the direction of the iron sheet facing the stirrer is curved into an arc, and the iron sheet is fixed at a place where the stirrer does not contact, so that the relative speed between the waste liquid and the iron sheet due to stirring is ensured. (3) Stirring the waste liquid treated in the step (2) according to the rotating speed in the range of 50-600rpm until the heavy metal content in the waste liquid is not changed. (4) The iron particles or the iron sheets are adsorbed by a magnet for recycling, the treated wastewater is placed into a container with the magnet at the bottom for standing for 1-5 hours, the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled. If the recovered iron particles or iron pieces are to be reused, the steps (1) to (4) may be repeated. Heavy metal compounds adsorbed on the surface of the iron particles during the cyclic acid treatment can automatically fall off with the iron oxide to become precipitates, and the iron particles or the iron sheets recover as originally. And if the heavy metal wastewater after the primary treatment does not reach the corresponding heavy metal wastewater discharge standard, treating the iron particle acid again to treat the heavy metal wastewater which does not reach the standard. And circulating until reaching the standard.
The invention can treat the heavy metal sewage with industrial emission level to the emission standard basically by one-time treatment. The method can greatly improve the rate of treating industrial heavy metal wastewater by iron particles or iron sheets with the size of more than millimeter, and can remove heavy metals with the heavy metal content in the industrial wastewater from the wastewater once. The iron particles or the iron sheets can be continuously used for 20 times without pickling in the middle. Thus greatly reducing the cost of treating heavy metal wastewater. The use of the meter-grade iron sheet ensures the recovery and operation simplicity of the iron sheet to the maximum extent, and avoids the secondary pollution of wastewater by iron. In summary, the invention ensures the realization of zero-valent iron from research to real application. Therefore, the method has remarkable innovation and application value.
The specific embodiment of the invention is as follows:
example 1:
(1) Adding 0.5mmol/L CNa to the Cr to be treated 6+ Waste liquid (Cr) 6+ Content of 2 mg/L);
(2) Iron particles having an average size of 1mm by 1mm were weighed according to the volume/mass content of the waste liquid of 5 g/L. Adding H with concentration of 0.5% 2 SO 4 Pouring out the acid solution after soaking in the solution for 1 minute, and immediately adding the iron particles into the Cr treated in the step (1) 6+ Waste liquid;
(3) Stirring the waste liquid treated in the step (2) at a rotating speed of 350rpm to obtain Cr in the waste liquid 6+ The content is not changed any more.
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 5 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 2 is a diagram of Cr in wastewater 6+ Is a graph of the removal rate versus time. As can be seen from FIG. 2, under the above technical parameters, cr in the waste liquid after 8 minutes of CNa addition treatment 6+ The content of the catalyst is 0.002mg/L, and reaches the discharge standard @<0.01 mg/L), the removal rate is 99.9%, t 100 8 minutes; the maximum removal rate of the CNa is 99.9% after 80 minutes, the content of the CNa is 0.002mg/L, the emission standard is reached, and t 100 80 minutes. T of addition of CNa 100 T without CNa 100 10% of (C). Illustrating that enlarging greatly improves the removal of Cr from iron particles 6+ Is a rate of (a).
Example 2:
(1) Adding 50mmol/L NaCl to the Ni to be treated 2+ Waste liquid;
(2) Weighing iron pieces with average size of 1m×1m×1mm according to the content of 50g/L, soaking in 5% HCl solution for 10 min, pouring out acid solution, and immediately adding the iron pieces into Ni processed in step (1) 2+ And (3) waste liquid. Bending the iron sheet into an arc in the direction facing the stirrer, and fixing the iron sheet at a place where the stirrer cannot contact, wherein the relative speed between the waste liquid and the iron sheet caused by stirring is ensured;
(3) Stirring at 500rpm until Ni in the waste liquid 2+ The content is not changed any more;
(4) Taking out the iron sheet for recycling, placing the treated wastewater into a container with a magnet at the bottom, standing for 1 hour, pouring out the wastewater, filtering, and recycling sediment at the bottom and sediment obtained by filtering.
FIG. 3 is Ni in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 3, under this technical parameter, ni after 16 minutes of NaCl addition treatment 2+ The content (measured by ICP) is 0.0235mg/L, reaching the discharge standard [ (]<0.5 mg/L), i.e., t 100 16 minutes, the removal rate is 98.32%; after 18 minutes without adding NaCl, the maximum removal rate reaches 80 percent, ni 2+ The content (measured by ICP) is 0.4mg/L, and the emission standard is reached. But t after salt addition 100 T is less than that of no added salt 100 2 minutes shorter and 18.32% higher removal rate. Therefore, adding NaCl under the conditions can improve the removal of Ni from iron particles 2+ And increases the removal rate.
Example 4:
(1) 25mmol/L NaNO 3 Added to Co to be treated 2+ Waste liquid;
(2) Iron pieces with average size of 0.15m×0.21m×5.0mm were weighed according to the amount of 20g/L, and H was added to a concentration of 5% based on the volume and mass of the waste liquid 2 SO 4 Pouring out acid solution after soaking in the solution for 7 minutes, and immediately adding iron particles into the Co treated in the step (1) 2+ And (3) waste liquid. Bending the iron sheet in the direction facing the stirrerThe arc is used for fixing the iron sheet at the place where the stirrer cannot contact, so that the relative speed between the waste liquid and the iron sheet caused by stirring is ensured;
(3) Stirring at 500rpm until Co in the waste liquid 2+ The content is not changed any more;
(4) Taking out the iron sheet for recycling, placing the treated wastewater into a container with a magnet at the bottom, standing for 3 hours, pouring out the wastewater, filtering, and recycling sediment at the bottom and sediment obtained by filtering.
FIG. 4 is Co in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 4, naNO is added at this technical parameter 3 Treatment of 20 min Co 2+ The content of the catalyst is 0.0246mg/L, and reaches the discharge standard [ (]<1mg/L)，t 100 20 minutes, the removal rate is 98.77%; without addition of NaNO 3 The maximum removal rate of 68% is reached in 28 minutes, co 2+ The content of (2) is 0.64mg/L, and reaches the emission standard, namely t 100 For 28 minutes. I.e. NaNO is added 3 T of (2) 100 8 minutes less and the removal rate is 30.77 percent higher. Under the above technical parameters, naNO is added 3 Can improve Co removal 2+ And the maximum removal efficiency is improved.
Example 4:
(1) 10mmol/L Na 2 SO 4 Added to Zn to be treated 2+ Waste liquid;
(2) Iron pieces having an average size of 1 mm. Times.0.5mX0.6 m were weighed out in an amount of 20g/L and put into a 5% HCl solution. Pouring out acid solution after soaking for 5 minutes, and immediately putting the iron sheet into Zn treated in the step (1) 2+ And (3) waste liquid. Bending the iron sheet into an arc in the direction facing the stirrer, and fixing the iron sheet at a place where the stirrer cannot contact, wherein the relative speed between the waste liquid and the iron sheet caused by stirring is ensured;
(3) Stirring at 350rpm until Zn in the waste liquid 2+ The content is not changed any more.
(4) Taking out the iron sheet for recycling, placing the treated wastewater into a container with a magnet at the bottom, standing for 2 hours, pouring out the wastewater, filtering, and recycling sediment at the bottom and sediment obtained by filtering.
FIG. 5 shows Zn in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 5, na is added at this technical parameter 2 SO 4 Zn in the waste liquid after 25 minutes treatment 2+ The content of the water-soluble polymer is 0.0368mg/L, and reaches the discharge standard%<0.05 mg/L), i.e., t 100 25 minutes, the removal rate is 98.16%; without addition of Na 2 SO 4 The maximum removal rate of 82% in 35 minutes is achieved, the content is 0.36mg/L, and the emission standard is not achieved. Description adding Na 2 SO 4 After that, the Zn removal of the iron sheet is improved 2+ Is not limited, and the removal rate of the catalyst is not limited.
Example 5:
(1) 1.5mmol/L of CNa is added to the Cd to be treated 2+ Waste liquid;
(2) Weighing iron particles with average size of 1.8mm multiplied by 3mm multiplied by 7mm according to the content of 30g/L, putting the iron particles into HCl solution with concentration of 2.5% for soaking for 5 minutes, pouring out acid solution, and immediately putting the iron particles into Cd treated in the step (1) 2+ Waste liquid;
(3) Stirring at 50rpm until the Cd in the waste liquid 2+ The content is not changed any more.
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 2 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 6 is a diagram of Cd in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 6, under the technical parameters, cd in the wastewater after 30 minutes of CNa addition treatment 2+ The content (measured by ICP) of the catalyst is 0.00056mg/L, and reaches the discharge standard [ (]<0.001 mg/L), i.e., t 100 30 minutes; the maximum removal rate of 73% and Cd in 50 minutes without CNa 2+ The content of (C) is 0.54mg/L, and the discharge standard is not met. So the addition of CNa improves the removal of Cd from iron particles 2+ And also improves the removal rate.
Example 6:
(1) Adding 40mmol/L NaCl to Pb to be treated 2+ Waste liquid;
(2) In an amount of 40g/LIron particles having an average size of 3.1 mm. Times.4 mm. Times.9.6 mm were weighed and fed with H at a concentration of 2% 2 SO 4 Soaking in the solution for 8 min, pouring out the acid solution, and immediately adding iron particles into Pb treated in the step (1) 2+ Waste liquid;
(3) Stirring at 400rpm until Pb in the waste liquid 2+ The content is not changed any more.
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 3 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 7 is a diagram of Pb in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 7, under the technical parameters, pb in the wastewater after 14 minutes of NaCl addition treatment 2+ The content (measured by ICP) is 0.00382mg/L, reaching the discharge standard%<0.01 mg/L), i.e. t 100 14 minutes, the removal rate is 99.8%; and the maximum removal rate of 81% in 16 minutes without adding NaCl, and Pb in the filtered wastewater 2+ The content (measured by ICP) is 0.38mg/L, which does not reach the emission standard. Therefore, the addition of NaCl can improve the removal of Pb from iron particles 2+ And also improves the removal rate.
Example 7:
(1) 20mmol/L NaNO 3 Added to Cu to be treated 2+ Waste liquid;
(2) Iron particles having an average size of 1.1 mm. Times.1.6 mm. Times.3.2 mm were weighed out in an amount of 30g/L, and fed with H at a concentration of 1% 2 SO 4 Pouring out the acid solution after soaking in the solution for 10 minutes, and immediately adding the iron particles into Cu treated in the step (1) 2+ Waste liquid;
(3) Stirring at 390rpm until Cu in the waste liquid 2+ The content is not changed any more.
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 3.5 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 8 is a diagram of Cu in wastewater 2+ Is a graph of the removal rate versus time. From FIG. 8, it is possible toIt is seen that, under this technical parameter, naNO is added 3 After 18 minutes of treatment, cu in the wastewater 2+ The content (measured by ICP) is 0.00382mg/L, reaching the discharge standard%<0.01 mg/L), i.e. t 100 18 minutes, the maximum removal rate is 99.8%; without addition of NaNO 3 The maximum removal rate of 73.4% is reached in 18 minutes, and Cu in the wastewater is removed 2+ The content (measured by ICP) is 0.532mg/L, and the emission standard is not met. Description of NaNO 3 Is added to improve the removal of Cu by iron particles 2+ And also improves the removal rate.
Example 8:
(1) 45mmol/L NaNO 3 Added to Se to be treated 4+ Waste liquid;
(2) Iron particles with average size of 1.1mm multiplied by 1.6mm multiplied by 3.2mm are weighed according to the content of 50g/L, put into 5% HCl solution for soaking for 10 minutes, then the acid solution is poured out, and the iron particles are immediately put into Se treated in the step (1) 4+ Waste liquid;
(3) Stirring at 420rpm to Se in the waste liquid 4+ The content is not changed any more;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 2.5 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 9 shows Se in wastewater 4+ Is a graph of the removal rate versus time. As can be seen from FIG. 9, naNO is added under this technical parameter 3 Se in wastewater after 40 minutes of treatment 4+ The content (measured by ICP) is 0.00521mg/L, reaching the discharge standard%<0.01mg/L)，t 100 40 minutes, the maximum removal rate is 99.7%; without addition of NaNO 3 After 35 minutes of treatment, the maximum removal rate reaches 92 percent, and Se in the wastewater 4+ The content (measured by ICP) is 0.16mg/L, which does not reach the emission standard. Description of NaNO 3 Is added to improve the removal of Se from iron particles 4+ And also improves the removal rate.
Example 9:
(1) 25mmol/L Na 2 SO 4 Added to Te to be treated 4+ Waste liquid;
(2) Iron particles with average size of 0.9mm multiplied by 1.3mm multiplied by 2.7mm are weighed according to the content of 10g/L, put into HCl solution with concentration of 4.5% for soaking for 10 minutes, then the acid solution is poured out, and immediately the iron particles are put into Te after the treatment of step (1) 4+ Waste liquid;
(3) Stirring at 250rpm until Ni in the waste liquid 2+ The content is not changed any more;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 2 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 10 is Te in wastewater 4+ Is a graph of the removal rate versus time. As can be seen from FIG. 10, na is added under this technical parameter 2 SO 4 Te in wastewater after 21 minutes of treatment 4+ The content (measured by ICP) is 0.00312mg/L, reaching the discharge standard%<0.005mg/L)，t 100 21 minutes, the maximum removal rate is 99.84%; without addition of Na 2 SO 4 The maximum removal rate of 76% in 27 minutes, and Te in the wastewater 4+ The content (measured by ICP) is 0.48mg/L, which is far above the emission standard. Description of Na 2 SO 4 Is added to improve the removal of Te from iron particles 4+ And also improves the removal rate.
Example 10:
(1) 15mmol/L CNa was added to the Mn to be treated 2+ Waste liquid;
(2) Iron particles having an average size of 0.9 mm. Times.1.3 mm. Times.2.7 mm were weighed out in an amount of 10g/L, and fed with H at a concentration of 3.5% 2 SO 4 Pouring out acid solution after soaking in the solution for 8 minutes, and immediately adding iron particles into Mn treated in the step (1) 2+ Waste liquid;
(3) Stirring at 350rpm until Ni in the waste liquid 2+ The content is not changed any more;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 2.5 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 11 is Mn in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 11, under this technical parameter, mn in wastewater after 28 minutes of CNa addition treatment 2+ The content (measured by ICP) is 0.0453mg/L, reaching the discharge standard%<0.1mg/L)，t 100 28 minutes, the removal rate is 97.74%; and the maximum removal rate of 86% in 33 minutes without CNa is achieved, mn in the wastewater 2+ The content (measured by ICP) is 0.28mg/L, and the emission standard is not met. Indicating that the addition of CNa improves iron particle removal Mn 2+ And also improves the removal rate.
Example 11:
(1) Adding 42mmol/L NaCl to the Sn to be treated 2+ Waste liquid;
(2) Iron particles having an average size of 0.9 mm. Times.1.3 mm. Times.2.7 mm were weighed out in an amount of 10g/L, and fed with H at a concentration of 3.5% 2 SO 4 Pouring out acid solution after soaking in the solution for 8 minutes, and immediately adding iron particles into Sn treated in the step (1) 2+ Waste liquid;
(3) Stirring at 250rpm until Ni in the waste liquid 2+ The content is not changed any more;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 2.5 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 12 shows Sn in wastewater 2+ Is a graph of the removal rate versus time. As can be seen from FIG. 12, under the technical parameters, sn in the wastewater after 33 minutes of NaCl addition treatment 2+ The content (measured by ICP) is 0.0546mg/L, reaching the discharge standard%<0.2mg/L)，t 100 33 minutes, the maximum removal rate is 97.37%; and the maximum removal rate of the wastewater reaches 74% in 24 minutes without adding NaCl, and Sn in the wastewater 2+ The content (measured by ICP) is 0.52mg/L, which is far above the emission standard. Indicating that adding NaCl improves the removal of Sn from iron particles 2+ And also improves the removal rate.
Example 12:
(1) Adding 18mmol/L CNa to the heavy metal Cr to be treated 6+ Waste liquid;
(2) Iron particles having an average size of 0.98 mm. Times.2.92 mm. Times.10 mm were weighed in an amount of 20g/L by mass and fed with H at a concentration of 3.5% 2 SO 4 Pouring out the acid solution after soaking in the solution for 9 minutes, and immediately adding iron particles into the waste liquid treated in the step (1); (3) Stirring at 360rpm until Cr in the waste liquid 6+ The content is not changed any more;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 4 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled. Repeating the steps (1) - (4), but skipping the pickling process, and recycling for 20 times. The circulating performance of the iron particles under the technical parameters of the iron particle quantity, the salt concentration and the stirring speed are examined.
Under the above parameter conditions, both CNa and CNa-free can reach the emission standard, so only the circulation performance is compared here. FIG. 13 (a) is a view of Cr in wastewater 6+ The "removal rate versus time" curve "of 20 times of the removal cycle. Since it is too dense, 13 (b) gives each time t corresponding to FIG. 13 (a) 100 Bar graph (all reaching emission standards). 2mg/L of new Cr is changed from waste liquid once per cycle 6+ After the waste liquid is treated once, the iron sheet is not pickled, and new Cr is immediately treated 6+ The other technical parameters of the waste liquid are as described above. In contrast, the process was carried out 5 times without CNa (due to the long treatment time, sufficient for comparison), and Cr was contained in the wastewater 6+ The "removal rate vs. time curve" of 5 times of the removal cycle of (c) is shown in FIG. 13 (c). As can be seen from a comparison of FIGS. 13 (a) or (b) and (c), under this technical parameter, the first Cr removal with CNa is performed 6+ Only 8 minutes is needed until the removal rate reaches approximately 100%, the removal rate can still reach approximately 100% after the cycle is completed for 20 times, and t 100 For 19 minutes. While Cr can be added without CNa 6+ Down to approximately 100%, but 80 minutes for the first time and 100 minutes for the second to fifth cycles. Therefore, the cycle performance after CNa addition is greatly increased.
Example 13:
(1) 38mmol/L of CNa was added to the mixed wastewater of the heavy metal waste liquid to be treated (containing the following heavy metal ions (0.2 mg/L each)：Cr 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Se 4+ 、Te 4+ 、Mn 2+ ) In (a) and (b);
(2) Iron particles having an average size of 0.5 mm. Times.1.1 mm. Times.3.5 mm were weighed out in an amount of 48g/L, and fed with H at a concentration of 5% 2 SO 4 Pouring out the acid solution after soaking in the solution for 10 minutes, and immediately adding iron particles into the waste liquid treated in the step (1);
(3) Stirring at 350rpm until Ni in the waste liquid 2+ The content is not changed any more;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 3 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 14 is a view of Cr in wastewater 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Se 4+ 、Te 4+ 、Mn 2+ 、Sn 2+ Is a graph of the removal rate versus time. As a comparison we measured the removal rate versus time for no CNa, all other things being the same as described above, except that no CNa was present. Table 1 shows the comparison of the contents, removal rates, time to maximum removal rate, compliance with emission standards, and the like of the CNa-and CNa-free mixed wastewater. As can be seen from Table 1, the maximum removal rate of all the above heavy metal ions after CNa addition is increased, except Ni 2+ 、Co 2+ The other heavy metal ions can reach the emission standard only after CNa is added.
Table 1. Information comparison of the content of each heavy metal in the mixed wastewater with CNa and without CNa when the maximum removal rate is reached, the removal rate, the time for reaching the maximum removal rate, whether the emission standard is compounded, and the like.
Example 14:
(1) 27mmol/L NaCl was added to the mixed wastewater of the heavy metal waste liquid to be treated (containing the following heavy metal ions (0.2 mg/L each: cr) 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Se 4+ 、Te 4+ 、Mn 2+ ) In (a) and (b);
(2) Weighing iron particles with average size of 0.61mm multiplied by 1.0mm multiplied by 3.4mm according to the amount of 36g/L, putting the iron particles into HCl solution with concentration of 4% for soaking for 9 minutes, pouring out acid solution, and immediately putting the iron particles into the waste liquid treated in the step (1);
(3) Stirring at 430rpm until the content of all heavy metal ions in the waste liquid is unchanged;
(4) The iron particles are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with the magnet at the bottom for standing for 2 hours, and then the wastewater is poured out for filtration, and the sediment at the bottom and the sediment obtained by filtration are recycled.
FIG. 15 is a view of Cr in wastewater 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Se 4+ 、Te 4+ 、Mn 2+ 、Sn 2+ Is a graph of the removal rate versus time. As a comparison we measured the removal rate versus time for the absence of NaCl, all other things being the same as described above, except that no NaCl was present. Table 2 shows the comparison of the content, the removal rate, the time for reaching the maximum removal rate, the compound emission standard and the like of each heavy metal in the mixed wastewater with and without NaCl. As can be seen from Table 2, under the above technical parameters, the maximum removal rate of all heavy metal ions is increased after adding NaCl, cr 6+ 、Zn 2 + 、Cd 2+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 4+ Several heavy metal ions can reach the emission standard after being treated by adding NaCl, while Ni 2+ 、Co 2 + 、Mn 2+ 、Sn 2+ Can reach the standard with or without adding NaCl.
And 2. Comparing the content of each heavy metal in the mixed wastewater with and without NaCl when the maximum removal rate is reached, the removal rate, the time for reaching the maximum removal rate, whether the emission standard is compounded and the like.
To further make Fe 0 The method is easy to recycle, so that the operation is simpler, the zero-valent iron sheet with the size close to 1 meter can be adopted to react with heavy metals, and the use of the iron sheet enables the technology to meet one of requirements of large-scale treatment of heavy metal wastewater, namely the operation is simple. The iron flakes are also beneficial in that the volume percent of oxidized meter-scale iron flakes is much smaller than nano-and millimeter-scale iron particles. However, the reaction rate is necessarily low due to the small specific surface area of the iron sheet. The method of the invention can still improve the heavy metal removal rate of the iron sheet to the rate required by the application.
The invention can treat the heavy metal sewage with industrial emission level to the emission standard basically by one-time treatment. The method can greatly improve the rate of treating industrial heavy metal wastewater by iron particles or iron sheets with the size of more than millimeter, and can remove heavy metals with the heavy metal content in the industrial wastewater from the wastewater at one time. The iron particles or the iron sheets can be continuously used for 20 times without pickling in the middle. Thus greatly reducing the cost of treating heavy metal wastewater. The invention ensures the recovery and operation simplicity of the iron sheet to the maximum extent by using the rice-grade iron sheet, and avoids the secondary pollution of the wastewater by iron. In summary, the invention ensures the realization of zero-valent iron from research to real application. Therefore, the method has remarkable innovation and application value.
Claims (10)
1. A method for improving the reaction speed of zero-valent iron particles and iron sheets and heavy metal ions is characterized by comprising the following steps:
1) Adding 0.5-50mmol/L sodium salt into the heavy metal waste liquid to be treated;
2) Weighing iron particles or iron sheets according to the mass content of 5-50g/L, and adding sulfuric acid (H) 2 SO 4 ) Or pouring out the acid solution after soaking in hydrochloric acid (HCl) solution, and immediately adding iron particles or iron sheets into the heavy metal waste liquid obtained by adding sodium salt in the step 1);
3) Stirring the waste liquid treated in the step 2) until the heavy metal content in the waste liquid is not changed.
2. The method for increasing the reaction rate of iron particles and iron flakes with heavy metal ions according to claim 1, wherein in said step 1), the sodium salt is CH 3 COONa、NaCl、NaNO 3 、Na 2 SO 4 Any one of them.
3. The method for increasing the reaction rate of zero-valent iron particles and iron pieces with heavy metal ions according to claim 1, wherein in the step 1), the heavy metal waste liquid contains one or more of the following heavy metal ions: cr (Cr) 6+ ,Ni 2+ 、Co 2+ 、Zn 2+ 、Cd 3+ 、Pb 2+ 、Cu 2+ 、Se 4+ 、Te 4+ 、Mn 2+ 、Sn 2+ 。
4. The method for increasing the reaction rate of the zero-valent iron particles and the iron pieces with the heavy metal ions according to claim 1, wherein in the step 2), the iron particles or the iron pieces with the average size of each dimension ranging from 0.5mm to 1m are weighed.
5. The method for increasing the reaction rate of the zero-valent iron particles and the iron pieces with the heavy metal ions according to claim 1, wherein in the step 3), the iron pieces are bent to be circular arc facing the stirrer, and the iron pieces are fixed at a place where the stirrer is not contacted, so that the relative rate between the waste liquid and the iron pieces caused by the stirring is ensured.
6. The method for increasing the reaction rate of iron particles and iron flakes with heavy metal ions according to claim 1, wherein in said step 2), sulfuric acid (H) having a concentration of 0.5 to 5% is added to the iron particles or iron flakes 2 SO 4 ) Or immersing in hydrochloric acid (HCl) solution, and pouring out the acid solution.
7. The method for increasing the reaction rate of iron particles and iron flakes with heavy metal ions, according to claim 6, characterized by adding sulfuric acid (H 2 SO 4 ) Or soaking in hydrochloric acid (HCl) solution for 1-10 min, and pouring out the acid solution.
8. The method for increasing the reaction rate of the zero-valent iron particles and the iron pieces with the heavy metal ions according to claim 1, wherein in the step 3), the waste liquid treated in the step 2) is stirred at a rotation speed ranging from 50rpm to 600rpm until the heavy metal content in the waste liquid is not changed.
9. The method for increasing the reaction rate of zero-valent iron particles and iron pieces with heavy metal ions according to any one of claims 1 to 8, characterized in that after the above step 3), the iron particles or iron pieces are adsorbed by a magnet for recycling, the treated wastewater is placed in a container with a magnet at the bottom for standing for 1 to 5 hours, and the wastewater is poured out for filtration, and the precipitate at the bottom and the precipitate obtained by filtration are recovered.
10. The method for increasing the reaction rate of the zero-valent iron particles and the iron pieces with the heavy metal ions according to claim 9, wherein the steps 1) to 4) are repeated if the recovered iron particles or iron pieces are to be reused, and the heavy metal compounds adsorbed on the surfaces of the iron particles and the iron oxides automatically fall off to become precipitates during the cyclic acid treatment, and the iron particles or the iron pieces are recovered as before. If the heavy metal wastewater after the primary treatment does not reach the corresponding heavy metal wastewater discharge standard, treating the iron particle acid again to treat the heavy metal wastewater which does not reach the standard, and circulating until reaching the standard.
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