Background[1][2
Triazophos is a broad-spectrum sulfur monothiophosphate insecticide and acaricide. It was first developed by Hoechst AG in Federal Germany in 1971. The pure product is a light yellow liquid with a melting point of 2 to 5°C. It is relatively stable to light and is easily decomposed in acidic or alkaline media. Insoluble in water, solubility in water is 39 mg/L at 23°C, soluble in most organic solvents. It is highly toxic to higher animals. The acute oral LD5082 mg/kg in rats; the acute transdermal LD501100 mg/kg.
Toxic to fish and bees. Triazophos has contact killing and gastric poisoning effects on pests, as well as certain intraosmotic effects. It is mainly sprayed with water and used for fruit trees, vegetables, cotton, and cereal crops to control aphids, leafhoppers, thrips, lepidopteran larvae, and spider mites. It can also control soil pests and nematodes infecting leaves. .
In 2007, JMPR reassessed triazophos residues in agricultural products. Due to dietary risks or insufficient assessment data, the assessment report recommended the withdrawal of strawberries, pome fruits, onions, cabbage, and cabbage from the International Codex Alimentarius. Maximum residue limit (MRL) standards for triazophos in Brussels sprouts, cauliflower, peas, broad beans, kidney beans, carrots, potatoes, soybeans, cereals, sugar beets, coffee beans, milk and beef. In addition to temporarily retaining its MRL in cereals at the request of the Chinese delegation, recommendations to withdraw the MRL of triazophos in other 16 products (categories) were all adopted by the Codex Alimentarius Commission (CAC) in 2008. In 2010, JMPR reassessed the dietary risk of triazophos residues in rice and concluded that it presents an acute risk.
Since the 1990s, the scope of application of triazophos has rapidly expanded in my country, becoming a popular variety for pest control on crops such as grain, cotton, fruits and vegetables. However, the risks that the widespread use of triazophos in China may pose to human and animal health and the environment have not been systematically and scientifically assessed. The lack of risk assessment makes it difficult to implement risk management, and incidents of triazophos harming human and animal health and the ecological environment occur from time to time.
Apply[3]
This product is a broad-spectrum insecticide and acaricide, and can kill nematodes. It has a control effect on rice planthoppers, borers, aphids, spider mites, cotton bollworms, cabbage caterpillars, nematodes and other grain, cotton, fruit and vegetable pests. Especially effective in killing insect eggs.
Notes[4]
(1) This product cannot be mixed with alkaline substances to avoid decomposition and failure.
(2) Stop using pesticides one week before crop harvest.
(3) Bees, silkworms, and fish are sensitive to this drug.
Degradation research[5]
1. Microbial degradation of triazophos
When studying the degradation of triazophos in tidal flat sediments, it was found that unsterilized sediments have a much greater ability to degrade triazophos than sterilized sediments, which shows that microorganisms in the environment have the ability to degrade triazophos. Degradation of triazophos. The use of microbial degradation method to eliminate pesticide pollution is an ideal and reliable method to remove environmental pollution. Compared with traditional physical and chemical methods, it has the advantages of mild treatment conditions, low cost and less likely to cause secondary pollution. However, its research is currently at a In the preliminary stage, industrialization has not yet been implemented.
2. Hydrolysis of triazophos
Hydrolysis of triazophos is an important aspect of its abiotic degradation. Current research on the hydrolysis of triazophos mainly focuses on reaction kinetics, degradation products, pathways and influencing factors. Different methods were used to analyze the hydrolysis rate, hydrolysis half-life and factors affecting hydrolysis of triazophos in water.
These studies have shown that the hydrolysis of triazophos conforms to the characteristics of first-order reaction kinetics, that is, the degradation rate of triazophos is proportional to the first power of the triazophos content in the system. The differential rate equation can be expressed as dc /dt reactive diluent = kC. After shifting and integrating, we can get ln( c0 /ct) = kt, that is, the degradation of triazophos in water can be expressed by formula (1). Hydrolysis of triazophos The half-life is t1 /2=ln( 2 /k)
In the formula: k—hydrolysis rate waterproofing agent constant; t—reaction time; c0—initial concentration of triazophos; ct—triazophos concentration at time t. The hydrolysis rate of triazophos is affected by temperature and pH value.� is larger, the hydrolysis rate under alkaline conditions is significantly greater than the hydrolysis rate under neutral and acidic conditions, and the hydrolysis rate under high temperature conditions is much greater than the hydrolysis rate at room temperature. There are not many studies on the hydrolysis mechanism of triazophos. The GC-MS method was used to determine the degradation products of triazophos, and different hydrolysis pathways under acidic and alkaline conditions were proposed.
3. Photodegradation of triazophos
In the treatment of high-concentration toxic organic compound wastewater that is difficult to degrade through biochemical reactions, the introduction of ultraviolet light (UV) can greatly increase the reaction rate. Photodegradation usually means that the chemical bonds in the molecules of organic matter are broken under the action of light energy, forming extremely active intermediate products – free radicals. The free radicals then react with solvents or other reactants to obtain photolysis products, which are then gradually oxidized to generate carbon dioxide. , water and other ions, such as nitrate ions, phosphate ions, halogens, etc.
In the study of triazole phosphorescent degradation, it is mainly divided into photooxidative degradation and photocatalytic degradation. In the process of photodegrading organophosphorus pesticides, adding corresponding oxidants or catalysts can also greatly improve the degradation effect.
Preparation[6]
Most domestic advanced triazophos production adopts a two-step production process. Phenylhydrazine hydrochloride is used as the starting material and urea is condensed under the action of a catalyst to prepare 1 phenyl semicarbazide and 1 phenyl semicarbazide, and then excess formic acid is added for cyclization to obtain crude oxazolidol, which is then filtered and washed with water. Obtain benzoconazole.
The intermediate product of triazophos, benzoconazol, generates soluble sodium benzoconate in alkali solution, and then synthesized with ethyl chloride under the action of phase transfer catalyst to produce triazophos. The crude triazophos is obtained after desolubilization. High purity triazophos crude oil. The yield of the two-step synthesis of triazophos is not high. The yield is 80% based on phenylhydrazine hydrochloride, and the purity of triazophos is only 85%. The solvent consumption is large, and the solvent methylene chloride consumption is 100 to 150kg/t. Triazophos; the unreacted formic acid content in the triazophos wastewater is high, and the formic acid content is 325kg/t oxazolol; the unreacted oxazolol content in the triazophos wastewater is 57kg/t triazophos.
The discharge of these substances with wastewater not only increases the difficulty of wastewater treatment, but also causes a waste of resources. The wastewater discharged during the production process of triazophos contains toxic and harmful substances such as triazophos, benzazole, urea, ammonium chloride, phenylhydrazine hydrochloride, formic acid, etc. The CODcr value is high, about 32634mg/L, and the pH value is <1. Production seriously pollutes surrounding surface water bodies and causes certain harm to people, livestock and crops.
Some research has provided a clean production process for triazophos. The steps are: oxazol and ethyl chloride are synthesized under the action of a catalyst. After layering and washing, the water-soluble substances are separated, and then vacuum is used. The rising membrane separator removes solvent and recovers the solvent.
The 2# wastewater produced by triazophos after standing for stratification and washing is alkaline and contains water-soluble sodium benzoconate. Mix the 2# wastewater with the 1# acidic wastewater produced by benzoconate, and then add The acid adjusts the pH value to generate water-insoluble oxenazole solid, which is recovered by centrifugal separation and produces 3# wastewater.
4 The wastewater is sent to the terminal wastewater treatment device, and is discharged after reaching the national wastewater discharge standards.
Main reference materials
[1] Encyclopedia of Chinese Agriculture·Pesticides Volume
[2] Zhang Zhiheng, Yuan Yuwei, Zheng Weiran, et al. Dietary intake and risk assessment of triazophos residues[J]. Chinese Journal of Pesticides, 2011, 13(5): 485-495.
[3] Practical Fine Chemical Dictionary
[4] Pesticide Operation and Use Knowledge Manual
[5] Ni Na, Jiang Linghuo. Research progress on triazophos degradation[J]. Journal of Environment and Health, 2008 (1): 90-93. [6] CN201210532736.4 A clean production process of triazophos
