CN1576242A

CN1576242A - Paraquat waste water containing cyanogen treating method

Info

Publication number: CN1576242A
Application number: CN 03141928
Authority: CN
Inventors: 郑留清; 宋志庆
Original assignee: SHANGHAI CAC CHEMICAL CO Ltd
Current assignee: SHANGHAI CAC CHEMICAL CO Ltd
Priority date: 2003-07-29
Filing date: 2003-07-29
Publication date: 2005-02-09

Abstract

The present invention belongs to the field of waste water treating technology. The treating process of waste water containing paraquat and cyanide includes: adding the waste water and catalyst in the amount of 0.5-10 wt% of waste water into pressured reactor; stirring and heating to 100-200 dtg.c; introducing oxidant gas to control the reaction pressure in 0.5-1.8 MPa for certain time of reaction; cooling to normal temperature and filtering the reacted liquid. The catalyst of the present invention is active carbon catalyst, which may be used as carrier with certain amount of composite metal elements loaded. The cyanide containing waste water through the treatment of the present invention is further treated in a biochemical treating system. The present invention has simple treating process, less investment in apparatus and low treating cost.

Description

Method for treating paraquat cyanide-containing wastewater

Technical Field

The invention relates to a method for treating pesticide industrial wastewater, in particular to a method for treating cyanide-containing paraquat wastewater.

Background

In the process of paraquat production in a cyanohydrin route, cyanide-containing wastewater is generated, and the cyanide-containing wastewaterhas the characteristics of high cyanide ion concentration, high Chemical Oxygen Demand (COD), high salt content, dark color, opacity, difficult oxidation and the like, and is difficult to completely remove by using a conventional method.

In the prior art, the waste liquid is mostly incinerated by a thermal oxidation furnace abroad, but the equipment investment for using the method is large. At present, the chlor-alkali oxidation method is mostly adopted in China, the method has high treatment cost, increases the salt content in the wastewater after treatment, cannot enter a biochemical treatment system, and causes difficulty for further treatment.

At present, a pressurized hydrolysis method is adopted to treat wastewater, which is an effective method for removing cyanide, but the cyanide-containing paraquat wastewater requires that the COD removal rate is about 90 percent while the cyanide is broken, and the purple black opaque state (the purple black substance has toxicity to biological strains in a biochemical pool) is converted into transparent light yellow liquid, so that the conventional pressurized hydrolysis method cannot be used.

It can be seen from the above-mentioned state of the art that in the current wastewater treatment technology, there is an urgent need to provide a treatment method with low investment cost, simple process and high efficiency to effectively and rapidly treat cyanide-containing wastewater and beautify the environment.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for treating paraquat cyanide-containing wastewater, which comprises the following steps:

(1) adding paraquat cyanide-containing wastewater and a catalyst into a pressure kettle;

(2) stirring and heating to 100-200 ℃;

(3) introducing a gas oxidant, controlling the reaction pressure range between 0.5MPa and 1.8MPa, and performing aeration reaction for 12 to 24 hours;

(4) cooling to normal temperature, opening the kettle, and filtering the reaction liquid

In the present invention, the pressure hydrolysis reaction is carried out in an autoclave, and the reaction in the autoclave is as follows (chemical reaction formula):

directly adding the wastewater stock solution into a pressure kettle, or diluting the wastewater stock solution with water and then treating; the water adding amount has no certain requirement, and the treatment time can be shortened if the water amount is large.

Heating to a certain temperature in the presence of a catalyst, and introducing a gas oxidant, wherein the gas oxidant can be air, oxygen-enriched gas or pure oxygen gas directly.

The catalyst used in the invention is active carbon, or active carbon can be used as a carrier, and then metal composite elements are loaded, and the available metal elements can be selected from: one or more composite elements of platinum, cerium, silver, nickel, copper, chromium and cobalt; the compound of one or more of platinum, cerium and cobalt is preferred. The catalyst is prepared with granular active carbon through soaking the salt solution of the said metals on active carbon and roasting.

In the invention, the dosage of the catalyst is preferably within the range of 0.5-10% of the original liquid of the wastewater; more preferably, the dosage of the catalyst is 1-5% of the wastewater stock solution. The catalyst can be repeatedly used, and the mechanical loss can be added each time.

The reaction temperature of the invention can be between 100 ℃ and 200 ℃; more preferably, the reaction temperature is between 120 ℃ and 170 ℃.

The reaction pressure range of the invention is between 0.5MPa and 1.8 MPa; more preferably, the reaction pressure is in the range of 0.9MPa to 1.5 MPa.

The reaction time of the present invention varies depending on the reaction temperature, pressure, kind of the oxidant used as a gas and flow rate thereof, and is generally 12 to 24 hours.

After the method is used for treating the cyanide-containing wastewater, the concentration of cyanide in the wastewater is reduced to be less than or equal to 0.5mg/l from 6000mg/l, the Chemical Oxygen Demand (COD) is reduced to be less than or equal to 3500mg/l from 3 ten thousand mg/l, the color of the liquid is changed from opaque purple black to transparent light yellow, and the liquid can enter a biochemical treatment system for further treatment. The invention has simple process, low equipment investment and low treatment cost.

Detailed Description

Example 1:

in a 500 ml autoclave provided with a thermometer, a stirrer, a gas mass flow meter and a tail gas absorption system, 300 g (CN) of paraquat cyanide-containing wastewater stock solution is firstly added^-6000mg/l, COD 3 ten thousand mg/l),and then 10 g of catalyst is put in, the catalyst takes active carbon as a carrier, and metal composite elements are loaded on the catalyst, the metal composite elements are one or a plurality of combinations of three elements of platinum, cerium and cobalt, concretely, the catalyst uses granular active carbon, salt solution of the metals is coated on the active carbon by using an impregnation method and is roasted to obtain the catalyst, then a kettle cover is covered, the mixture is stirred and heated to 130 ℃, an air inlet valve is opened to lead air to the pressure to reach 1.3Mpa, an exhaust valve is opened immediately to lead a small amount of gas to be discharged, and the air inlet valve is adjusted to lead the pressure in the kettle to be kept at 1.3 Mpa. Thus, the temperature was kept constant at 130 ℃ and the pressure was kept constant at 1.3MPa, and the reaction was carried out for 20 hours by aeration. Cooling to 30 deg.C, opening the kettle, and filtering the reaction solution to obtain 265 g filtrate and 9.1 g catalyst, wherein the solution is transparent yellow, and CN^-0.5mg/l、COD3000mg/l。

Examples 2 to 6:

the procedure is as in example 1, the previous example is used as a batch of catalyst and fresh catalyst is added until the weight of catalyst is 10 g. The results are the same as in example 1, see table 1 below:

TABLE 1

Batch number	The catalyst is derived from Batch number	Addition of new catalyst Dosage (gram)	Results after treatment
			Results after treatment		CN^-(mg/l)	COD(mg/l)
			Example 2	Example 1	CN^-(mg/l)	COD(mg/l)	0.9	0.47	2980
Example 3	Example 2	1.2	Example 2	Example 1	0.49	3010	0.9	0.47	2980
Example 3	Example 2	1.2	Example 4	Example 3	0.49	3010	1.0	0.50	3300
Example 5	Example 4	1.3	Example 4	Example 3	0.45	2950	1.0	0.50	3300
Example 5	Example 4	1.3	Example 6	Example 5	0.45	2950	1.1	0.50	3100

Example 7:

the operation method is the same as that of example 1, but 150 g of wastewater stock solution is added, and 150 g of water is added; the reaction time was 18 hours. The results were the same as in example 1.

Example 8:

the procedure was as in example 1, except that the gaseous oxidizing agent was oxygen and the reaction time was 16 hours, and the results were the same as in example 1.

Claims

1. A method for treating paraquat cyanide-containing wastewater is characterized by comprising the following steps:

(2) stirring and heating to 100-200 ℃;

(4) cooling to normal temperature, opening the kettle and filtering the reaction liquid.

2. The method of claim 1 wherein the catalyst is activated carbon.

3. The method of claim 1, wherein the catalyst comprises activated carbon as a carrier, and a single metal or a metal composite element is supported on the activated carbon.

4. The method according to claim 3, wherein the metal element is one or more elements selected from the group consisting of platinum, cerium, silver, nickel, copper, chromium, and cobalt.

5. The method according to claim 4, wherein the metal element is selected from the group consisting of platinum, cerium, and cobalt.

6. The method of claim 1, wherein the amount of the catalyst is 0.5-10% of the wastewater stock solution.

7. The method of claim 5, wherein the amount of the catalyst is 1-5% of the wastewater stock solution.

8. The method of claim 1 wherein said gaseous oxidant is selected from the group consisting of air, oxygen-enriched gas and pure oxygen.

9. The method as claimed in claim 1, wherein the reaction temperature is 120-170 ℃.

10. The method of claim 1, wherein the reaction pressure is in the range of 0.9Mpa to 1.5 Mpa.