CN1199868C - Treatment method of wastewater in the process of preparing p-aminophenol by electrolysis - Google Patents

Abstract

The present invention discloses a treating method for wastewater in a para-aminophenol technology by an electrolytic method. The method firstly adopts the activated carbon adsorption of a fruit shell to remove para-aminophenol, the wastewater is evaporated and concentrated to recover industrial grade ammonium sulfate, and the recovery rate of the ammonium sulfate is more than 98%. Evaporated water is used for preparing 18% of sulfuric acid water solution to be used as electrolytic solution to enter an electrolytic bath, and the closed cycle of the water is realized. The activated carbon of the fruit shell of the para-aminophenol is adsorbed, 18 wt% of sulfuric acid water solution can be used as a desorbing agent to regenerate the activated carbon (the unit consumption of the activated carbon is approximately 50 kg/ton PAP), and the desorbed solution can return into the electrolytic bath to participate in electrolytic reaction. Therefore, the wastewater treating method of the present invention has the advantages of zero release and environment protection.

Description

Treatment method of wastewater in the process of preparing p-aminophenol by electrolysis

technical field

The invention relates to a method for treating waste water, in particular to a method for treating waste water produced in the process of preparing p-aminophenol by electrolysis.

Background technique

The wastewater produced in the process of preparing p-aminophenol by electrolysis mainly contains (NH ₄ ) ₂ SO ₄ , about 13-18 (wt)%; p-aminophenol (PAP), about 1.3g/l; its pH=6.9-7.1 , the specific gravity is 1.12. About 13 tons of waste water is generated for every ton of PAP produced. If it is discharged directly, it will not only pollute the environment, but also cause the loss of (NH ₄ ) ₂ SO ₄ and PAP.

At present, only the method reported in the patent document CN1168865A can be seen regarding the treatment method of this type of wastewater. Although this treatment method takes into account the recovery and treatment of (NH ₄ ) ₂ SO ₄ and PAP, its entire treatment process is in terms of rationality and There are still deficiencies in economics. Therefore, how to treat the waste water produced in the process of preparing p-aminophenol by electrolysis more reasonably and more economically becomes the object of the present invention.

Contents of the invention

The invention provides a zero-discharge treatment method for wastewater in the process of preparing p-aminophenol by electrolysis.

Technical solutions:

Waste water zero discharge treatment method described in the present invention comprises the steps:

(1) The waste water containing (NH ₄ ) ₂ SO ₄ and PAP produced in the process of preparing p-aminophenol by electrolysis flows into the adsorption column equipped with fruit shell activated carbon for adsorption, wherein: the waste water in the adsorption column The linear velocity is 0.15-0.3m/s, the adsorption temperature is 55-60°C, the particle size of the shell activated carbon is 8-20 mesh, and the length of the working section of the adsorption column is 0.7m.

(2) carry out evaporative concentration to obtain concentrated solution through step (1) adsorption gained liquid, this concentrated solution obtains ammonium sulfate after filtering, drying, and filtrate returns to activated carbon adsorption column inlet and repeats step (1), and its reflux ratio is with 0.2 ~0.3 is advisable, (the said reflux ratio is the ratio of the volume flow rate of the concentrated liquid to the volume flow rate of the feed liquid entering the evaporator) the water and sulfuric acid obtained by evaporation and concentration are prepared into a 18 (wt)% sulfuric acid solution, or entered as an electrolyte Electrolyzer, or enter step (1) said activated carbon adsorption column as eluent to regenerate activated carbon, the desorption solution of activated carbon regeneration gained enters electrolyzer to participate in electrolytic reaction, and said activated carbon is preferably leached method for regeneration, each time The leaching time is at least 5 hours, preferably 5-5.5 hours, and the temperature is 80°C.

The wastewater treatment method of the present invention has the following advantages:

(1) When evaporating and concentrating, the technical grade ammonium sulfate has been recovered, and the water obtained by evaporation can be used as the water required for preparing electrolyte or desorbent (18 (wt)% sulfuric acid solution), so as to realize the recycling of water .

(2) In the treatment method of the present invention, except that (NH ₄ ) ₂ SO ₄ is removed from the system in time, other materials all realize closed circulation, realize zero discharge, and the recovery rate of (NH ₄ ) ₂ SO ₄ is greater than 98%, Therefore, the present invention is superior to the prior art in terms of rationality of flow design and system operation economy, and is an environmentally friendly wastewater treatment method.

Description of drawings

Fig. 1 is a schematic flow chart of the wastewater treatment method of the present invention.

Specific implementation method

Below in conjunction with embodiment, method of the present invention is described further, but it does not limit protection scope of the present invention:

Example 1

1. Take 65L of waste water, light yellow, pH = 7.0, specific gravity 1.12. This batch of waste water is made of 6.25 kg of nitrobenzene, 6.8 kg of sulfuric acid and an appropriate amount of water to participate in the electrolysis reaction, after treatment, purification and separation of PAP.

2. After adsorbing PAP through the adsorption column of fruit shell activated carbon [1kg, divided into 3 levels, each level is 1m (the working section is 0.7m), the particle size of the fruit shell activated carbon is 8-20 mesh (the linear velocity of wastewater in the adsorption column is 0.15- 0.3m/s, the adsorption temperature is 55～60℃), the solution is colorless and transparent, the specific gravity is 1.12, pH=7.0, based on the adsorption raw material liquid PAP inlet concentration of 1.3g/L, the actual adsorption liquid PAP outlet concentration is less than 10 ^-4 g/L, the PAP adsorption rate is greater than 99%.

3. Send the above-mentioned liquid obtained after adsorption into a double-effect evaporator for evaporation treatment. 53L of steam condensate obtained during evaporation and concentration (collected by a condenser with a distillation device), analyzed by high-pressure liquid chromatography, the content of aniline < 1-2ppm, and the content of nitrobenzene < 1ppm. Sulfuric acid aqueous solution, participate in the electrolysis reaction, does not affect the electrolysis effect.

4. Evaporate and concentrate the colorless adsorption solution to 12L, cool to crystallize, and centrifugally filter. The filtrate was refluxed to the inlet of the adsorption column to repeat step 2 (the reflux ratio was 0.2-0.3), and the filter cake was dried to obtain 4.47kg of pure white (NH ₄ ) ₂ SO ₄ . Further processing from the mother liquor yielded 4.6kg of pure white (NH ₄ ) ₂ SO ₄ . A total of (NH ₄ ) ₂ SO ₄ 9.07kg was recovered.

5. Recovery and quality of (NH ₄ ) ₂ SO ₄

(1)

(2) The quality inspection results of recovered (NH ₄ ) ₂ SO ₄ reached the national standard of the second-grade product. Indicator name Recovery of (NH ₄ ) ₂ SO ₄ GB535-83, secondary product N content (dry basis), % 20.87 ≥20.8 _H2O content, % 0.098 ≤1.0 Free acid (H ₂ SO ₄ ) content, % 0.0203 ≤0.20 Organic matter (PAP) content, % 0.05 ≤0.1

6. Take the second-stage 1m fruit shell activated carbon adsorption column and desorb it with 18% H ₂ SO ₄ 250ml aqueous solution, the desorption temperature is 80°C, use the leaching method, the leaching time is 5hr, leaching 3 times, the leaching solution is 700ml in total , the analyzed PAP concentration was 39.4 g/l. The adsorption column is washed with evaporated water until neutral, and the washing liquid and leaching liquid are sent to the electrolytic cell to participate in the reaction. The regenerated activated carbon column re-adsorbs wastewater, and the regeneration rate of activated carbon is about 83%. Activated carbon is recycled 3 times and then incinerated.

Example 2

Repeat the first item of Example 1, 1 kg of fruit shell activated carbon is equally divided into 5 parts, and cross-flow adsorption is performed in a stirred tank. After 5 stages of cross-flow adsorption, the PAP concentration is 0.24g/l. In this case, the adsorption solution is as described in Example 1. The quality of recovered (NH ₄ ) ₂ SO ₄ does not meet the requirements of industrial purity, and its organic matter content is > 0.1%. The color of (NH ₄ ) ₂ SO ₄ is white at first, and turns to white after 1 day. Slightly brownish red, getting darker after a few days.

Example 3

Repeat items 1 to 5 of Example 1, but in the sixth step of activated carbon regeneration, use 18% H ₂ SO ₄ aqueous solution to continuously flow through the activated carbon adsorption column for desorption at a slow speed, and adopt leaching method for desorption and leaching time < 5hr , other conditions are not in the 6th step operating condition range in example 1. Facts have proved that the regeneration rate of activated carbon at this time is <70%, and it cannot be recycled.

Claims (3)

1, electrolytic process prepares wastewater treatment method in the p-aminophenol technology, it is characterized in that, described treatment process comprises the steps:

(1) electrolytic process prepared produces in the p-aminophenol technology, contain (NH ₄) ₂SO ₄The adsorption column that active fruit shell carbon is housed with the waste water inflow of amino-phenol adsorbs, wherein: the linear velocity of said waste water in adsorption column is 0.15-0.3m/s, adsorption temp is 55～60 ℃, and said active fruit shell carbon particle is 8～20 orders, and the working zone length of adsorption column is 0.7m;

(2) will carry out evaporation concentration through step (1) absorption gained liquid and get concentrated solution, this concentrated solution after filtration, after the drying ammonium sulfate, and filtrate is back to active carbon adsorption column import repeating step

(1), water that evaporation concentration obtains and sulfuric acid are mixed with 18 (wt) % sulphuric acid soln, or enter electrolyzer as electrolytic solution, or enter the said active carbon adsorption column of step (1) as eluent gac is regenerated, the desorption liquid of regeneration of activated carbon gained enters electrolyzer and participates in electrolytic reaction.

2, treatment process as claimed in claim 1 is characterized in that, the reflux ratio of filtrate is 0.2～0.3 in the step (2).

3, treatment process as claimed in claim 1 is characterized in that, said gac is regenerated and adopted the leaching method in the step (2), each leaching time at least 5 hours, and temperature is 80 ℃.