Plasticizers are additives used to improve the plastic properties of plastics. The plasticizers currently used are mainly phthalate compounds. It is estimated that the annual production of phthalate esters in the early 1980s has exceeded 1.3 million tons. About 95% of them are used as plasticizers, and the remaining 5% are used as pesticide carriers, insect repellents, fuel additives, formulations for cosmetics and fragrances, and coatings and lubricants. The most widely used phthalate plasticizers are diisooctyl phthalate, followed by dibutyl phthalate. In the industrial production and life, the widespread use of plastic products causes environmental pollution, mainly phthalates.
1 Source of plasticizer contamination
1.1 The solubility of phthalate phthalates in water is higher than that of organic chlorinated hydrocarbons. The content of phthalic acid esters in rainwater, river water and seawater in industrial areas is 10 to 1000 times higher than that of polychlorinated biphenyls. They are adsorbed on suspended particulate matter in water or in a dissolved state. At present, the content of phthalic acid in ground water in the world is generally 10-9. In the waters close to the industrial area, the content is higher. For example, the concentration of diisooctyl phthalate in the mouth of the Mississippi River in the United States reaches 0.6×10-6. The concentration of diisooctyl phthalate in the water sample of Lake Superior Lake in the lake is 0.3×10-6, dibutyl phthalate was also detected in tap water with water from the Ohio River. The phthalic acid esters in the surface water are very stable and difficult to decompose, mainly from industrial and agricultural wastewater, surface runoff and sedimentation of particulate matter in the air.
1.2 Phthalate esters in soils The phthalates in soils are usually from the sedimentation of industrial soot. Sewage irrigation, plastic waste accumulation, agricultural plastic film, etc. have been exposed to rain for a long time, which can cause serious pollution of local soil. For example, the content of phthalate in the surface soil of Ehime Prefecture, Japan is 22×10-9～78×10-9, and the diisooctyl phthalate 0.23×10-6 and tannic acid are measured in the surface soil of the suburb of Beijing, China. Butyl ester 1.1 × 10-6, diisobutyl phthalate 0.21 × 10-6. Due to the precipitation of phthalic acid ester in water and the adsorption and exchange of sediment, the content of phthalate in river bottom can be accumulated to a relatively high level. For example, phthalate is detected in the bottom of the Ohio River in the United States, which is 0.8%. These phthalates are released when water quality changes, are in a dynamic equilibrium with water content, and contaminate benthic organisms.
2 the harm of phthalate
2.1 Effects of phthalate on the ecosystem phthalate is easily soluble in fats and organic solvents and is not readily soluble in water, so it can be enriched in living organisms. For example, after 2 weeks of living in water containing 0.1×10-9 of diisooctyl phthalate, the content of phthalate in the body can reach 1.34×10-6 and concentrate 13400 times. The result of bio-enrichment has a detrimental effect on the ecosystem. In waters containing diisodecanoate doses of 3×10-9, 10×10-9, 30×10-9, the reproduction of large cockroaches within 2 weeks was reduced by 60% and 70%, respectively, compared with normal conditions. 80%, and the highest of these doses is 30 x 10-9, still far below the median lethal dose of the acute toxicity test. It has been confirmed by large-dose feeding trials in mammals that terephthalate has teratogenic and amphogenic effects. Plasticizers such as dibutoxyethyl phthalate and dimethoxyethyl ester can cause embryo developmental malformations in chickens. The content of phthalate in fish and wild animals harvested in different areas is consistent with the pollution level in each region. In addition, in poultry, livestock, in plant essential oils, green tea essential oils, corn flour, flour, salt and other foods and spices, different levels of phthalate esters were also measured.
2.2 The effect of phthalate on the human body phthalate can enter the human body through drinking water, eating, skin contact and breathing. In the local ambient air of vehicles and ships with PVC equipment and houses decorated with PVC building materials, the content of dibutyl phthalate can reach 1.2 mg/m3 (within 3 years of activation). In the air of the production plant and the batching workplace, the phthalate ester enters the human body mainly through breathing. The artificial kidney dialysis device used by kidney patients can enter 150 mg of diisooctyl phthalate in the body during 5 hours of operation. The extracorporeal circulation device used by heart patients can enter 33 mg of diisooctyl phthalate in one body during one operation. Dibutyl phthalate can cause toxic nephritis. Long-term exposure to phthalate esters has a damaging effect on the peripheral nervous system, which can cause multiple neuritis and sensation of dullness and numbness. Phthalate esters also have an inhibitory and anesthetic effect on the central nervous system. The plasticizer phthalate contained in the medical blood storage bag used in medical treatment is easily dissolved into the blood, thereby entering a large amount in the blood transfusion patient. After the plasma is stored in the blood bag for 21 days (4 ° C), the content of diisooctyl phthalate can reach 50×10-6 to 70×10-6. Patients who enter this plasma can develop symptoms such as dyspnea, pulmonary shock, and even death.
3 Precautions against phthalate contamination Plasticizers that are toxic or difficult to biodegrade should be discontinued. For workshops and factories that produce plasticizers, the phthalate content in the air and in the waste liquid should be strictly controlled. In factories using plasticizers, plasticizers that are easily degradable and less toxic should be used as much as possible, and the dosage should be strictly controlled. Food packaging industries such as food containers try to avoid the use of packaging materials filled with a large amount of phthalate. For the phthalate pollution that has been caused in the environment, it can be treated by means of biodegradation and adsorption.
3.1 Microbial degradation When phthalates are metabolized by isolated and mixed microorganisms, preliminary and final biodegradation can occur through enzymatic hydrolysis. Mathur and Rouatt isolated the bacteria Serratia Marcescens Bizio, which uses 2-ethylhexyl phthalate and n-dioctylphosphonate as the sole carbon source and energy source to degrade these compounds. The main degradation product of these phthalates is phthalic acid. Later, Fairbanks et al. observed degradation of phthalates in soil containing sludge to CO2 with a half-life of 8 days to 72 days. And after 146 days, 76% to 93% of the phthalates are degraded to CO2. The Enterobacteraerogenes strain isolated from the plastic tube of the deionized water drain can degrade dimethyl phthalate by using dimethyl phthalate as the sole carbon source. Within 41 days, the bacteria degraded 1000 x 10-6 dimethyl phthalate to less than 400 x 10-6. Wallnofer et al. found a series of microorganisms that can degrade dioctyl phthalate and 2-ethylhexyl phthalate, and proposed a degradation pathway for disulfide phthalate degradation by different microorganisms.
3.2 Adsorption and distribution method Phthalates are not easily soluble in water, soluble in organic solvents, and thus have a strong tendency to be distributed into sediment organic matter. Matsudo and Schnitzer provided data indicating the partitioning of dialkyl phthalate on dissolved fulvic acid, which greatly enhanced its apparent solubility. According to the study of batch adsorption by Fairbanks et al., 0.87% of 2-ethylhexyl phthalate added to the centrifuge tube was adsorbed by the glass, and the remaining 96% to 99% was adsorbed by the soil (water and soil). The ratio is in the range of 5 to 300). This shows that deposits in the natural environment can significantly adsorb phthalate compounds.
3.3 Hydrolysis Phthalate esters, as a special ester, have the commonality of esters and can be hydrolyzed by acid or base catalysis. It is estimated that the hydrolysis half-life of phthalates can vary from 3.2 years for diethyl phthalate to 2000 years for phthalate-2-ethylhexyl ester. Thus the hydrolysis of this compound is not an important reaction process. In addition, phthalates may also undergo volatilization, but their volatilization is small due to their lower vapor pressure. At present, no reports on photolysis of phthalates have been found. However, according to its phenomenon of no absorption in the ultraviolet and visible light range, it can be inferred that they are difficult to carry out photochemical reactions.
Impact screwdriver bit,25mm screwdriver bit,screwdriver bit supplier,torsion screwdriver bit,professional screwdriver bit
henan horn tools co.,ltd. , https://www.nbhorntoolsltd.com