CN102963943B - Method for treating nitrobenzene wastewater by natural pyrrhotite - Google Patents

Abstract

The invention discloses a method for treating nitrobenzene waste water by using natural pyrrhotite, belonging to the field of sewage treatment. The steps are: (1) Crushing the natural pyrrhotite to a particle size of 50-200 mesh, and washing or pickling to expose the fresh surface of the pyrrhotite for use; (2) Adjusting the pH value of the nitrobenzene wastewater is 3-10; (3) mix the natural pyrrhotite treated in step (1) with the nitrobenzene waste water obtained in step (2) in a reactor; the mass concentration of pyrrhotite after mixing Not less than 50g/L; (4) Seal the reaction vessel in step (3) and place it on a vertical rotating turntable to mix and react for not less than 48 hours, and discharge the treated wastewater. The present invention adopts cheap natural pyrrhotite to pretreat nitrobenzene wastewater, has strong adaptability to influent pH, the removal rate of nitrobenzene compounds can reach more than 90%, is simple to operate, has low requirements on equipment, and can greatly reduce Processing Fees.

Description

A kind of method utilizing natural pyrrhotite to treat nitrobenzene wastewater

technical field

The invention belongs to the technical field of sewage treatment, and in particular relates to a method for treating nitrobenzene wastewater by utilizing natural pyrrhotite.

Background technique

Nitrobenzene compounds are harmful substances that seriously pollute the environment and endanger human health. Their BOD ₅ /COD _cr ratio is low, their biodegradability is poor, and wastewater treatment is difficult. If nitrobenzene is transformed into aniline with low toxicity and suitable for biodegradation by physical and chemical methods, and then completely mineralized by biological methods, the wastewater can be discharged up to the standard. The physical method is easy to cause secondary pollution and the treatment cost is high, and its wide application is limited. In practical applications, chemical methods are often used to pretreat high-concentration nitrobenzene-containing wastewater to reduce the impact load on biochemical pools.

Since Agrawal et al. proposed the technology of reducing aromatic nitro compounds with zero-valent iron in 1996, scholars at home and abroad have done a lot of research. But they mostly focus on the remediation of groundwater pollution by electrolyte iron with higher purity. Due to the relatively high cost of electrolyte iron, it is of great practical significance to find an inexpensive and effective alternative material. The internal electrolysis method of iron chips has the advantages of low raw material price, wide range of sources, and obvious effects, and has been paid attention to by people. However, the implementation of this technology is still challenged by the following aspects: This method is a large amount of aeration and does not make full use of the elemental iron. The reduction ability; the consumption of iron is large, and the iron filings are easy to harden after a period of reaction, thereby reducing the treatment effect; it is only suitable for wastewater with low pH, and a large amount of acid and alkali is required to neutralize wastewater.

Chinese patent application number: 2012100953696, publication date: July 25, 2012, discloses a method for pretreatment of nitrobenzene-containing wastewater by using ferrous sulfide, which the applicant applied for on April 1, 2012 The patent application document of , which discloses the method of using ferrous sulfide to carry out the pretreatment of nitrobenzene wastewater. The steps are: (1) Crushing the ferrous sulfide to a particle size of 50-60 mesh, and washing or pickling to expose the fresh surface of the ferrous sulfide for use; (2) adding the treated ferrous sulfide into the reaction vessel (3) Add nitrobenzene wastewater to the above reaction vessel, wherein the ratio of the mass concentration of ferrous sulfide to nitrobenzene in the reaction vessel is not less than 30:1, and the mass concentration of ferrous sulfide is not less than 3.6 g /L; (4) Place the reaction vessel in an anaerobic or anoxic environment, mix ferrous sulfide with nitrobenzene wastewater, and complete the pretreatment of nitrobenzene wastewater after mixing for 60-180 minutes. This patent provides a new method for treating nitrobenzene with artificially synthesized ferrous sulfide. But used ferrous sulfide is chemical product, and cost is higher. The method of use is intermittent batch use, the use is limited, and the pH requirement is high during use. However, the pH value of general nitrobenzene wastewater fluctuates greatly, so this method is not suitable for large-scale use. Therefore, it is necessary to find a method for nitrobenzene wastewater that has low cost and can handle relatively large pH fluctuations.

In fact, FeS exists on the earth in the form of pyrrhotite (Fe _(1-x) S, x is between 0 and 0.1), which is a widely distributed, cheap and easy-to-obtain natural mineral on the earth. The main component of natural pyrrhotite is ferrous sulfide, but the ratio of iron and sulfur is usually lower than 1:1, and its composition ranges from Fe ₇ S ₈ to Fe ₁₁ S ₁₂ . Its structure is from the standard NiA ₅ lattice It is derived from a variety of crystal forms, among which Fe ₇ S ₈ , which is the most deficient in iron atoms, has monoclinic symmetry, and some other intermediate state products and FeS have hexagonal and tetragonal crystal structures, respectively. Pyrrhotite in nature is often a mixture of monoclinic and hexagonal crystals, and its chemical properties are complicated by the existence of an iron deficiency in the crystal structure, which leads to lower crystal symmetry, thereby enhancing the It's reactive. In addition, there are some non-ferrous sulfide components such as ferric iron in natural pyrrhotite, which can promote the formation of iron-containing active compounds during the reaction between natural pyrrhotite and nitrobenzene. It is precisely because of the unique crystal structure and composition of natural pyrrhotite that it has a stronger reaction ability in a wider pH range than ferrous sulfide, and can react with nitrobenzene. Abandoned pyrrhotite will spontaneously oxidize when it is wet and in contact with air, producing acidic mine wastewater, which will cause serious harm to the water environment of the mine. Using the characteristics of pyrrhotite to reduce nitrobenzene compounds can not only reduce its harm to the mine environment, but also provide a cheap method for pretreatment of nitrobenzene wastewater. At present, there are no literature reports and patent publications on the research and application of reducing nitrobenzene pollutants by using natural pyrrhotite.

Contents of the invention

problem to be solved

Aiming at the problems of high treatment cost and narrow pH application range in the prior art for treating nitrobenzene wastewater, the present invention provides a method for treating nitrobenzene wastewater by using natural pyrrhotite, which is simple, effective and low-cost A method for pretreatment of nitrobenzene-containing wastewater.

Technical solutions

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A method utilizing natural pyrrhotite to process nitrobenzene waste water, the steps are:

(1) Crushing the natural pyrrhotite to a particle size of 50-200 mesh, and washing or pickling to expose the fresh surface of the pyrrhotite for use;

(2) Adjust the pH value of nitrobenzene wastewater to 3-10. If the pH value of nitrobenzene wastewater is between 3-10, no adjustment is required; if the pH value of nitrobenzene wastewater is too low, it will Accelerate the dissolution of natural pyrrhotite. If the pH value is too high, iron-containing oxides similar to patina will be formed on the surface of pyrrhotite. It is difficult to form a surface-bound iron system with reducing properties to realize p-nitrobenzene compounds. restoration;

(3) Mix the natural pyrrhotite treated in step (1) with the nitrobenzene waste water obtained in step (2) in a reactor; the mass concentration of pyrrhotite after mixing is not less than 50 g /L;

(4) Seal the reaction vessel in step (3) and place it on a vertical rotating turntable for a mixing reaction of not less than 48 hours, and discharge the treated wastewater.

Preferably, the natural pyrrhotite in the step (1) has a particle size of 60-80 mesh. The smaller the particle size, the better the reaction is, but too small will cause the natural pyrrhotite to dissolve too quickly, and the reaction process is not easy to control. Therefore, considering comprehensively, the particle size of natural pyrrhotite should be controlled to 50-200 mesh, and the effect is better when the particle size is 60-80 mesh, and the reaction process is easy to control.

Preferably, the pH value of the nitrobenzene wastewater is adjusted to 7 in the step (2).

Preferably, the temperature during the mixing reaction in the step (4) is 15-60°C. The conversion rate of nitrobenzene compounds increases with the increase of reaction temperature, the removal rate of nitrobenzene compounds is too low if the temperature is too low, it is difficult to popularize and apply, although higher temperature may obtain faster processing speed, but The processing cost also increases.

Preferably, the speed of the vertical rotating turntable in the step (4) is 10-60 r/min.

Preferably, the reaction temperature of the mixing reaction in the step (4) is 27°C. From the perspective of treatment effect and cost, the most reasonable reaction temperature is 27°C.

Beneficial effect

Adopting the technical scheme provided by the invention, compared with the existing known technology, has the following remarkable features: a kind of method of utilizing natural pyrrhotite of the present invention to process nitrobenzene waste water, adopts cheap natural pyrrhotite Pretreatment of nitrobenzene wastewater has strong adaptability to influent pH, the removal rate of nitrobenzene compounds can reach more than 90%, simple operation, low equipment requirements, using natural pyrrhotite, which has a wide source , low price, can greatly reduce processing costs. the

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

For the treatment of nitrobenzene wastewater, the nitrobenzene wastewater was prepared from nitrobenzene and distilled water, the pH of the water sample was 6.56, and the initial nitrobenzene concentration was 20 mg/L. Its processing steps are:

(1) Crushing the natural pyrrhotite to a particle size of 50-60 mesh, and washing or pickling to expose the fresh surface of the pyrrhotite for use;

(2) Weigh 10 g of the natural pyrrhotite treated in step (1) and mix it with nitrobenzene waste water in a reactor; the mass concentration of the pyrrhotite after mixing is 50 g/L;

(3) Seal the reaction vessel in step (2) and place it on a vertical rotary turntable for 3 days to mix and react. The rotation speed of the vertical turntable is 40 r/min. waste water discharge.

The concentration of nitrobenzene in the discharged wastewater after the reaction was reduced to 2 mg/L, and the removal rate of nitrobenzene was 90%.

Example 2

For the treatment of dinitrobenzene wastewater, dinitrobenzene wastewater is prepared from 1,3-dinitrobenzene and distilled water, the pH of the water sample is 6.75, and the initial 1,3-dinitrobenzene concentration is 102 mg/L. Its processing method is the same as embodiment 1, and difference is: the particle size of natural pyrrhotite is 60-80 order, and natural pyrrhotite mass concentration is 55 g after natural pyrrhotite and dinitrobenzene waste water mix /L, the rotation speed of the vertical rotating turntable is 60 r/min, the reaction temperature of the mixed reaction is 15°C, and the reaction time is 2 d.

The concentration of 1,3-dinitrobenzene in the treated wastewater was reduced to 10.5 mg/L, and the removal rate of 1,3-dinitrobenzene was 90%.

Example 3

For the treatment of nitrochlorobenzene wastewater, the nitrochlorobenzene wastewater was prepared from nitrochlorobenzene and distilled water, the pH of the water sample was 7.0, and the initial nitrochlorobenzene concentration was 96 mg/L. Processing step is the same as embodiment 1, and difference is that the particle size of natural pyrrhotite is 150-200 order, and natural pyrrhotite mass concentration after natural pyrrhotite is mixed with dinitrobenzene waste water is 60 g/ L, the rotation speed of the vertical rotating turntable is 10 r/min, the reaction temperature of the mixed reaction is 60°C, and the reaction time is 2 d.

The concentration of nitrochlorobenzene in the treated wastewater was reduced to 1.9 mg/L, and the removal rate of nitrochlorobenzene was 98%.

Example 4

For the treatment of nitrotoluene wastewater, the nitrotoluene wastewater was from a factory in Nanjing, the pH of the water sample was 2.0, and the initial nitrotoluene concentration was 25 mg/L. Its processing steps are:

(1) Crushing the natural pyrrhotite to a particle size of 70-90 mesh, and washing or pickling to expose the fresh surface of the pyrrhotite for use;

(2) Adjust the pH value of nitrotoluene wastewater to 3;

(3) Mix the natural pyrrhotite treated in step (1) with the nitrotoluene waste water obtained in step (2) in a reactor; the mass concentration of pyrrhotite after mixing is 51 g/L ;

(4) Seal the reaction vessel in step (3) and place it on a vertical rotating turntable with a rotation speed of 40 r/min for 8 days of mixing and reaction. The reaction temperature is controlled between 20-30°C, and the treated wastewater is discharged . The concentration of nitrobenzene in the discharged wastewater was reduced to 2.1 mg/L, and the removal rate of nitrotoluene was 92%.

Example 5

For the treatment of nitrochlorobenzene wastewater, the nitrochlorobenzene wastewater comes from a factory in Suzhou, the pH of the water sample is 11, and the initial nitrochlorobenzene is 35 mg/L. Its treatment steps are the same as in Example 4, the difference is: step (2) adjusts the pH value of nitrochlorobenzene wastewater to 10; in step (4), after sealing the reaction vessel in step (3), place it at a speed of The mixing reaction was carried out on a vertical rotating turntable at 50 r/min for 4 days, the reaction temperature was controlled between 30-35 °C, and the treated wastewater was discharged. The concentration of nitrochlorobenzene in the discharged wastewater was reduced to 2.5 mg/L, and the removal rate of nitrotoluene was 93%.

Claims (5)

1. a method utilizing natural pyrrhotite to process nitrobenzene wastewater, the steps are: (1) crushing the natural pyrrhotite to a particle size of 50-200 mesh, and exposing the fresh surface of the pyrrhotite by washing or pickling; (2) adjust the pH value of nitrobenzene waste water to be 3-10, if the pH value of nitrobenzene waste water is between 3-10, then need not adjust; (3) the natural pyrrhotite after step (1) is processed and the nitrobenzene wastewater obtained in step (2) are mixed in a reaction vessel; the mass concentration of pyrrhotite after mixing is not less than 50g/ L; (4) Seal the reaction vessel in step (3) and place it on a vertical rotating turntable for a mixed reaction for no less than 48 hours. The temperature during the mixed reaction is 15-60° C., and the treated waste water is discharged. 2. a kind of method utilizing natural pyrrhotite to process nitrobenzene waste water according to claim 1, is characterized in that, the natural pyrrhotite in described step (1), particle size is 60-80 head. 3. a kind of method utilizing natural pyrrhotite to process nitrobenzene waste water according to claim 1, is characterized in that, in described step (2), the pH value of nitrobenzene waste water is adjusted to 7 . 4. a kind of method utilizing natural pyrrhotite to process nitrobenzene waste water according to claim 1, is characterized in that, the rotating speed of the vertical rotating turntable in described step (4) is 10-60r/min . 5. a kind of method utilizing natural pyrrhotite to process nitrobenzene wastewater according to claim 4, is characterized in that, the reaction temperature of mixed reaction in the described step (4) is 27 ℃.