CN101244859A - Method for treating heavy metal wastewater - Google Patents

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for removing heavy metal ions such as chromium in wastewater. The invention utilizes a composite bacterium consisting of vibrio Desulfovibrio CB1.268(Desulfovibrio Sp.), enterobacter desulfurate CB1.139 (desulfomomaculum Sp.) and bacillus desulfurate CB1.168(Desulfobacter Sp.) to produce nano FeS in a culture medium containing lactate, ferrite and sulfate as well as K, Mg, Ca, Cu, Mn, B, Si and Mo elements under the alkaline condition at the temperature of 30-39 ℃ for anaerobic or facultative culture for 36-72 hours_x(ii) a The nano FeS_xIn acid stripsUnder-part dissociation to S^2－And Fe²⁺Reduction of Cr⁶⁺Is Cr³⁺With Ni²⁺、Cu²⁺、Zn²⁺And generating insoluble metal sulfide precipitate, and separating the precipitate to remove metal ions in the wastewater. The invention has the advantages of high removal efficiency, low cost and the like.

Description

A method for treating heavy metal wastewater

technical field

The invention belongs to the technical field of waste water treatment, and in particular relates to a method for removing heavy metal ions such as chromium in waste water.

Background technique

At present, there are more than 20 kinds of methods for treating heavy metal wastewater at home and abroad, including physical methods, chemical methods and biological methods. These methods have their own advantages and disadvantages. Seeking a more effective treatment method is always the goal that people yearn for. Chinese patent ZL 93106616.6 "Methods for Microbial Treatment of Electroplating Wastewater" firstly proposed a composite bacteria composed of four strains of Fusobacterium nucleatum, Paracoccus denitrificans, Edwardsiella tarda and Peptococcus anaerobic, which is effective for low concentrations (≤80mg/L ) Cr, Zn, Cu, Ni electroplating wastewater treatment has a better effect. Chinese Patent ZL 96117479.X "Composite Functional Bacteria for Treating Electroplating Wastewater, Its Cultivation Method and Its Application Method" adopts five strains of Desulfobacillus, Desulfovibrio, Enterobacter cloacae, Desulfur Enterobacter and Bacillus to form a composite bacteria. Patent ZL 93106616.6 has greatly improved the theoretical basis and practicability of removing heavy metals in electroplating wastewater, but the reaction residence time is long, and the pH value is limited to the range of 5.0 to 7.5. Chinese patent ZL00112916.3 "Method for Treating Metal-Containing Wastewater by Biochemical Method" adopts Desulfobacillus, Enterobacter cloacae, and Enterobacter desulfurum to form composite bacteria and proposes: "Bacteria and wastewater are added to the reaction tank at a volume ratio of 1:10 for reaction. After the reaction Then add 0.05-5 kg of chemical reagents Na ₂ S or/and FeS per ton of waste water to remove heavy metal ions in waste water. This method basically relies on adding Na ₂ S or/and FeS to remove heavy metal ions in waste water. The treatment cost is high, and there is a secondary pollution problem of hydrogen sulfide.

Contents of the invention

In order to overcome the defects of long reaction time for removing heavy metal ions in waste water by microbial method, large volume of culture tank and reaction tank, and the need to use Na ₂ S and FeS to remove heavy metal ions, the present invention provides a method for in-situ production of nano A method for removing heavy metal ions such as chromium in wastewater by iron sulfide (FeS _x ) materials.

The present invention is realized in the following manner:

On the basis of patents ZL93106616.6 and ZL 96117479.X, a specific process has been developed, using Desulfovibrio CB1.268 (Desulfovibrio Sp.), Desulfotomaculum Sp. The composite bacteria composed of 168 (Desulfobacter Sp.) can produce nanometer polysulfide ferrous sulfide (FeS _x ) materials in situ. It is detected by x-electron diffraction energy spectrometer, FeS _x where x=1.1～1.2, the FeS _x Under acidic conditions, it can well remove heavy metal ions in wastewater. The strain composition ratio of the composite bacteria is: Desulfovibrio CB 1.268 (Desulfovibrio Sp.): Desulfovibriobacter CB 1.139 (Desulfotomaculum Sp.): Desulfobacillus CB 1.168 (Desulfobacter Sp.)=1:1:1. The conditions for the composite bacteria to produce nano-iron sulfide are: anaerobic or facultative culture, pH7.0～7.4, temperature 30～39°C, containing 0.5%～5% (weight/weight) of lactic acid protein salt, 1%～10 % (weight/weight) ferrous salt and 1% to 10% (weight/weight) sulfate and K, Mg, Ca, Cu, Mn, B, Si, Mo elements, cultivated for 36 to 72 hours to produce nano-FeS _x . The nano-FeS _x material is 45-80nm in length, with an aspect ratio of 15-20. When magnified 300,000 times, it is in the form of filaments, and when magnified 400,000 times, it is lattice stripes and lattice particles. It dissociates under acidic conditions of pH 3-4. For S ^2- and Fe ²⁺ . Both S ^2- and Fe ²⁺ ions can effectively reduce Cr ⁶⁺ to Cr ³⁺ , and S ^2- can also form insoluble metal sulfide precipitates with Ni ²⁺ , Cu ²⁺ , Zn ²⁺ , etc. Precipitation, these ions are removed.

The process steps of the present invention's method for processing heavy metal wastewater are as follows:

Add lactic acid protein salt, ferrous salt and sulfate, and K, Mg, Ca, Cu, Mn, B, Si, Mo elements into the incubator, adjust the pH to 7.0-7.4, add the compound bacterial agent, Control the temperature at 30-39°C, cultivate anaerobic or facultative oxygen for 36-72 hours, transfer the fermented liquid containing nano-FeS _x to the reactor, adjust the pH to 3-4, and after the nano-FeS _x reacts with heavy metal wastewater, add NaOH adjusts the pH to 6-8, and the heavy metal ions in the wastewater form insoluble precipitates, which can be separated and precipitated to achieve the purpose of removing metal ions in the wastewater.

The reactions of S ^2- and Fe ²⁺ with Cr ⁶⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ etc. are shown in the ionic reaction formulas (1) to (9).

The reaction of S ^2- and Cr ⁶⁺ is as follows:

FeS _x +H ⁺ →Fe ²⁺ +S ^2- (1)

HCrO ₄ ^- +S ^2- →S↓+H ₂ O+Cr ³⁺ (2)

Cr ₂ O ₇ ^2- +S ^2- →S↓+H ₂ O+Cr ³⁺ (3)

Reaction formulas (2) and (3) show that the S ^2- produced by the acidolysis of FeS _x reduces Cr ⁶⁺ to Cr ³⁺ . After the reaction is completed, the pH is adjusted to 6-7 with NaOH, and Cr ³⁺ and OH- form Cr(OH) ₃ Precipitation, after solid-liquid separation, Cr ⁶⁺ is removed.

The reaction formula of Fe ²⁺ and Cr ⁶⁺ is as follows:

Fe ²⁺ +Cr ₂ O ₇ ^2- →Cr ³⁺ +Fe ³⁺ (4)

Reaction (4) shows that the Fe ²⁺ produced by the acidolysis of FeS _x reduces Cr ⁶⁺ to Cr ³⁺ . After the reaction is completed, the pH is adjusted to 6-7 with NaOH to form Cr(OH) ₃ precipitates. After solid-liquid separation, Cr ⁶⁺ be removed.

FeS can also directly react with CrO ₄ ^2- and Cr ₂ O ₇ ^2- to reduce Cr ⁶⁺ to Cr ³⁺ :

CrO ₄ ^2- +FeS _x →Cr ³⁺ +Fe ³⁺ +S↓ (5)

Cr ₂ O ₇ ^2- +FeS _x →Cr ³⁺ +Fe ³⁺ +S↓ (6)

After the reaction is completed, adjust the pH to 6-7 with NaOH, and Cr ³⁺ and OH- form Cr(OH) ₃ to precipitate. After solid-liquid separation, Cr ⁶⁺ is removed.

Secondly, the S ^2- produced by the acidolysis of nano-FeS _x also forms insoluble sulfide precipitates with Ni ²⁺ , Cu ²⁺ , Zn ^{2+ ,} etc. After separation and precipitation, Ni ²⁺ , Cu ²⁺ , Zn ²⁺ is removed, the reaction is as follows:

Ni ²⁺ +S ^2- →NiS↓ (7)

Cu ²⁺ +S ^2- →CuS↓ (8)

Zn ²⁺ +S ^2- →ZnS↓ (9)

Solubility products from nickel sulfide: α1.6×10 ^-24 , β2.5×10 ^-22 , γ2×10 ^-26 and copper sulfide solubility products: Cu ₂ S 6×10 ^-48 , CuS 6×10 ^-36 And zinc sulfide solubility product: α1.6×10 ^-24 , β2.5×10 ^-22 , it can be seen that the solubility of these sulfide ions is very small, and the concentration of metal ions remaining in the solution after sulfide precipitation is formed All are below the national standard emission standards.

Thirdly, Fe ²⁺ in nano-FeS _x is oxidized to Fe ³⁺ , and when the pH is adjusted to 6-7 with NaOH, Fe ³⁺ forms Fe(OH) ₃ precipitates, and Fe(OH) ₃ precipitates have good adsorption and mixing ( Flocculation, so that a small amount of inorganic and organic matter is adsorbed and removed, so that the effluent water quality is stable and up to standard.

Demonstration projects show that the removal rate of heavy metal ions in wastewater by nano-FeS _x is twice that of chemical methods (such as using chemical reagents Na ₂ SO ₃ or FeSO ₄ ). The removal rate of Cr ⁶⁺ is 99.99%, and the removal rate of Ni ²⁺ , Cu ²⁺ , Zn ²⁺ is 99.9%. Cr ⁶⁺ <0.1mg/L, Ni ²⁺ , Cu ²⁺ <0.5mg/L, Zn ²⁺ <0.2mg/L in the treated water. Therefore, the method of the present invention has the characteristics of high removal efficiency and low cost.

The compound bacterium of the present invention produces nano- _FeSx after 36-72 hours of culture and growth, and the mixture of the produced nano- _FeSx and strains is concentrated, sealed and packaged for use.

Description of drawings

The accompanying drawing is a schematic diagram of the technological process of treating heavy metal wastewater with nano-FeS of the present invention.

In the figure: 1, 2 is the incubator; 3 is the waste liquid adjustment tank; 4, 5 is the reactor; 6 is the filter; 7 is the clear water tank; 8 is the culture medium tank; 9 is the sludge tank; 10 is the metal Recycler; 11 is harmless mud cake.

The nano-FeS _x materials produced in the incubators 1 and 2 and the wastewater from the wastewater regulating tank 3 enter the reactor 4, and then enter the reactor 5 for two-stage reaction, and then pass through the filter and discharge 7 after reaching the standard, or reuse 8, Add culture medium to return water into incubator 1 or 2, at pH 7.0-7.4, 30-39°C, cultivate for 36-72 hours to produce nano-FeS _x for use. The sludge of the filter 6 enters the sludge pool 9, and adds acid to the recoverer 10 to dissolve and reclaim metal chromium, copper, zinc, nickel, and the harmless mud cake 11 can be used as fertilizer.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings of the description.

Example 1: Treatment of high-concentration chromium-containing wastewater in a certain workshop of a cold-rolling factory

Add the medium containing 0.5% lactic acid protein salt, 1% ferrous salt and 1% sulfate and K, Mg, Ca, Cu, Mn, B, Si, Mo elements in the incubator to adjust pH7. 0 to 7.4, add compound bacterial agent, control the temperature at 30°C, anaerobic or facultative culture for 36 hours, and generate a composite containing nano-FeS _x for use.

Treat 0.4m ³ high-concentration chromium wastewater per hour, the ratio of wastewater (W) to bionano FeS _x (BN) is 2:1, after static mixing, the reactor reacts for 30 minutes. Add 1‰ of cationic polyacrylamide (PAM) to flocculate and precipitate and filter to measure chromium and sulfide in water. It can be seen from Table 1 that the total chromium (TCr≤0.17mg/L) and hexavalent chromium (Cr ⁶⁺ ≤0.05mg/L) in the effluent are both better than the first-level discharge standard of the national standard (TCr1.5mg/L, Cr ⁶⁺ 0.5mg/L), S ^2- was not detected in the effluent. The recovery rate of Cr in the sludge is greater than 97.0%.

Table 1 Treatment results of cold-rolled chromium-containing wastewater Unit: mg/L

Note: ND is not detected.

Example 2: Treatment of leachate from a chromium slag mountain

Add the culture medium that contains 5% lactic acid protein salt, 10% ferrous salt and 10% sulfate and K, Mg, Ca, Cu, Mn, B, Si, Mo elements in the incubator, adjust pH7. 0 to 7.4, add compound bacterial agent, control the temperature at 35°C, anaerobic or facultative culture for 48 hours, and generate a composite containing nano-FeS _x for use.

The leachate contains Cr ⁶⁺ 5500mg/L, TCr 5800mg/L, pH 14, treats 9m ³ leachate per hour, W/BN=1:1. After static mixing, reactor reaction, precipitation and filtration, the results are listed in Table 2. It can be seen that TCr ≤ 0.21mg/L and Cr ⁶⁺ ≤ 0.05mg/L in the effluent are better than the first-level discharge standard of the national standard, and no S ^2- was detected in the effluent. The recovery rate of Cr in the sludge is greater than 97.5%.

Table 2 Treatment results of leachate from a chromium slag mountain Unit: mg/L

Note: ND is not detected.

Embodiment 3: A certain mining waste liquid treatment

Add the medium containing 3% lactic acid protein salt, 6% ferrous salt and 6% sulfate and K, Mg, Ca, Cu, Mn, B, Si, Mo elements in the incubator to adjust pH7. From 0 to 7.4, add compound bacterial agent, control the temperature at 39°C, and cultivate for 72 hours in anaerobic or facultative oxygen to generate a composite containing nano-FeS _x for use.

The waste liquid contains Cr ⁶⁺ 1280mg/L, V3800mg/L, pH2～3, 1m ³ waste liquid is treated per hour, W/BN=1:3. After static mixing, reactor reaction, precipitation and filtration, the results are listed in Table 3. It can be seen that Cr ⁶⁺ ≤0.05mg/L, TCr≤0.15mg/L, and V≤0.01mg/L in the effluent are all better than the national standard and the primary discharge standard of Sichuan Province, and no S ^2- was detected in the effluent. The recovery rate of Cr in the sludge is greater than 96%, and the recovery rate of vanadium is greater than 93%.

Table 2 Treatment results of leachate from a chromium slag mountain Unit: mg/L

Note: ND means not detected; *Standard of Sichuan Province.

Claims (3)

1. method of handling heavy metal wastewater thereby, it is characterized in that: the composite bacteria of utilizing desulfovibrio CB1.268 (Desulfovibrio Sp.), desulfurization intestines shape bacterium CB1.139 (Desulfotomaculum Sp.) and desulfurization bacterium CB1.168 (Desulfobacter Sp.) to form, in the substratum that contains lactic protein salt, ferrous salt and vitriol and K, Mg, Ca, Cu, Mn, B, Si, Mo element, under the alkaline condition, 30～39 ℃ of temperature, anaerobism or double oxygen were cultivated 36～72 hours, produced nanometer Fe S _xThis nanometer Fe S _xUnder acidic conditions, dissociate into S ^2-And Fe ²⁺, reduction Cr ⁶⁺Be Cr ³⁺, with Ni ²⁺, Cu ²⁺, Zn ²⁺Deng the metallic sulfide precipitation that generates indissoluble,, reach the purpose of removing metal ion in the waste water through precipitation separation.

2. a kind of method of handling heavy metal wastewater thereby according to claim 1 is characterized in that: the bacterial strain proportion of composing of described composite fungus agent is: desulfovibrio CB 1.268 (DesulfovibrioSp.): desulfurization intestines shape bacterium CB 1.139 (Desulfotomaculum Sp.): desulfurization bacterium CB 1.168 (Desulfobacter Sp.)=1: 1: 1; The weight percent of nutritive salt is in the substratum: lactic protein salt 0.5%～5%, ferrous salt 1%～10%, vitriol 1%～10%; Alkaline condition pH7.0～7.4, acidic conditions pH3～4, the nanometer Fe S of generation _xMiddle x=1.1～1.2.

3. a kind of method of handling heavy metal wastewater thereby according to claim 1, its processing step is as follows:

In the cultivation device, add the substratum contain lactic protein salt, ferrous salt and vitriol and K, Mg, Ca, Cu, Mn, B, Si, Mo element, regulate pH7.0～7.4, add composite fungus agent, 30～39 ℃ of controlled temperature, anaerobism or double oxygen were cultivated 36～72 hours, contained nanometer Fe S with what generate _xFermented liquid transfer in the reactor, transfer pH3～4, treat nanometer Fe S _xAfter the heavy metal wastewater thereby reaction, add NaOH and transfer pH6～8, the heavy metal ion in the waste water generates the precipitation of indissoluble, through precipitation separation, reaches the purpose of removing metal ion in the waste water.

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