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    Can water poisons become treasures?

    Date of Publication: 2021/11/9 15:52:58 Article Editor: View Count: 329
    As my country's water pollution situation intensifies, the country has continuously strengthened its efforts to control water pollution. Following the effective treatment of urban sewage, industrial sewage has become a hot spot in the field of water treatment.
      However, among the pollutants discharged from industrial wastewater, it is difficult to treat some highly toxic organic and inorganic components using traditional wastewater treatment methods. How to recycle them has become an important direction that the industry has explored in recent years. At the Tsinghua High-end Forum on Environment and Development held recently, Zhang Quanxing, an academician of the Chinese Academy of Engineering and professor of the School of Environment of Nanjing University, introduced the use of resin adsorption technology to treat toxic pollutants and achieve industrialization.
      Since the 1980s, the world's organic industrial production centers have moved from Europe and the United States to China and India, which has greatly accelerated the development of my country's chemical industry, but this has also caused serious organic poison pollution, and the pollution of organic poisons and heavy metals will Become the most prominent problem in water pollution.
      In particular, it should be pointed out that chemical industry, light industry, textiles, printing and dyeing are relatively developed in the eastern coastal and eastern regions of our country, and the discharge of industrial high-toxic waste water is directly related to the lives and health of the people. Therefore, our country attaches great importance to the pollution of organic poisons. In 2011, my country established a statistical reporting system for persistent organic pollutants. In 2012, the “Twelfth Five-Year Plan” for the prevention and control of persistent organic pollutants in major industries across the country was promulgated. Therefore, the development of new technologies for the reduction of toxic pollutants, resource utilization, deep purification and safety assurance is of great significance.
      Resin adsorption technology has obvious effects in the treatment of toxic organic wastewater, and has high recycling value
      my country’s chemical, light industry, textile, printing and dyeing industries emit tens of billions of tons of toxic organic substances every year. Usually through front-end treatment, clean production, or end-of-end treatment to reduce emissions, to solve the problem of achieving up-to-standard discharge of pollutants. Through nearly 20 years of work, we believe that resin adsorption technology is one of the important means to achieve industrial wastewater emission reduction and resource utilization.
      Focusing on the treatment of toxic organic wastewater by resin adsorption technology, researchers mainly carry out three aspects of research. Firstly, a series of ion exchange resins and adsorption resins were synthesized through the adjustment and surface modification of the porogen and resin skeleton, and the study of adsorption kinetics and thermodynamics was carried out. The second is to conduct research on adsorption and desorption technology and separation and recovery of organics on this basis. Finally, apply it in production.
      We pass the resin column containing the adsorbent through the solution containing toxic organics, and it can be effectively adsorbed. By eluting with an effective eluent, the organic matter can be recovered and used.
      Specifically, the real solution obtained after various pretreatments of wastewater is passed into a tower filled with resin to adsorb and separate toxic substances, and some of the adsorption effluent can be directly discharged up to the standard. Some need to undergo advanced biochemical and oxidation treatments before they can meet the emission standards. The toxic substances left in the tower can be effectively eluted and recovered by selecting a suitable eluent.
      For the recyclable toxic organic wastewater, it is mainly divided into 5 categories, namely chlorobenzene and its derivatives, aromatic phenols, aromatic amines, aromatic carboxylic acids, aromatic sulfonic acids and multifunctional organic compounds. . Some resin adsorption processes in our country can already achieve all the separation and recovery of pollutants, and the tail water can also be used, so that the purpose of cleaner production can be achieved. Some tail water can be discharged up to standard by recovering toxic organic matter and then undergoing advanced treatment.
      Resin adsorption technology treats more than 100 million tons of wastewater per year, and recovers about 100,000 tons of chemical raw materials per year, with direct economic benefits of more than 200 million yuan
      For chlorobenzene and its derivatives, my country's annual output is more than 300,000 tons. The production areas are concentrated in the lower reaches of the Yangtze River and the lower reaches of the Huai River, which puts tremendous pressure on the safety of the water environment. During the production process, it is necessary to discharge water washing wastewater containing 8%-10% HCl, 2000-8000 mg/L trivalent iron and 200-1000 mg/L benzene and chlorinated benzene, which wastes a lot of iron resources and transfers organic pollution. Things.
      It has been found in practice that 100-700 mg/L of benzene and chlorobenzene are contained in the by-product hydrochloric acid. In order to prevent the transfer of pollution, two resin adsorption technologies can be used to effectively recover all the benzene and chlorobenzene in the wastewater and generate FeCl3 solution. Used as a water treatment agent. At the same time, the by-product hydrochloric acid can be purified and sold as industrial hydrochloric acid, and the price is significantly increased. After applying ion exchange and adsorption technology, Jiangsu Yangnong Group alone has an annual direct economic benefit of more than 20 million yuan.
      In addition, the production of p-aminophenol by the hydrogenation reduction of p-nitrophenol by Jiangsu Yangnong Group can also create great environmental benefits and economic value. Every year, about 150,000 tons of wastewater contains 18,000 to 20,000 mg/L of COD, 3,000 mg/L of p-aminophenol, and 20% of sodium chloride. If a large amount of dilution biochemical is carried out on these wastewater, the cost is too high and resources are wasted. For this reason, the use of composite functional resins can almost quantitatively recover the p-aminophenol in wastewater.
      The salty wastewater is oxidized and enters the diaphragm electrolysis to produce caustic soda and chlorine, realizing zero discharge of wastewater. Relying on this technology, Yangnong Group can realize economic benefits of 20 million yuan every year. The general manager of Yangnong Group said: "Environmental governance has become a new economic growth point for Yangnong. Not only does it not need to throw money into the water, but it can also make money from the water."
      At the same time, my country has also achieved good results in the treatment and resource utilization of naphthalene wastewater, that is, (2,3-acid) production wastewater. The 2,3-acid production wastewater contains 1000 mg/L of difficult-to-degrade naphthalene molecules, which are difficult to deal with by general methods. The use of resin adsorption technology can effectively recover the 2,3-acid and 2-naphthol inside, and the treated wastewater can be directly discharged up to the standard. This technology is expected to generate economic benefits of 20 to 30 million yuan every year after being promoted nationwide.
      It is worth mentioning that the treatment and resource utilization of salicylic acid production wastewater have also made significant progress. For every ton of salicylic acid produced, about 15 tons of high-concentration organic wastewater are discharged, and the COD is about 18,000 to 20,000 mg/L, of which the phenol concentration is about 4000 to 5500 mg/L, and the salicylic acid concentration is about 1000 to 1800 mg/L. It has the characteristics of high concentration, strong acidity, high salinity, and high chroma. It is difficult to use conventional technology to achieve standard treatment. Using resin adsorption method to treat salicylic acid production wastewater can realize the recycling of more than 99% of the main organic pollutants, and the effluent can reach the standard discharge after simple neutralization.
      Resin adsorption technology has been applied to the treatment of industrial wastewater in the middle and lower reaches of the Yangtze River, the east route of the South-to-North Water Diversion Project, the Taihu Lake Basin and coastal industrial development zones. Treatment of various types of wastewater exceeds 100 million tons/year, of which 8 million tons/year of high-concentration, refractory and toxic organic wastewater are processed, and approximately 100,000 tons/year of chemical raw materials are recovered from wastewater, and the direct economic benefit (recycling value) reaches 200 million yuan above.
      Tighter standards promote progress in research and development, strengthen the advanced treatment of tail water, and the development and application of new resins are worth looking forward to
      In the tail water discharged from the COD and other conventional pollutant indicators, there are still trace toxic pollutants such as heavy metals. In addition, a variety of organic substances (persistent organics, endocrine disruptors, etc.) are also found in the biochemical tail water, which poses ecological risks. With the improvement of people's living standards, the safety of drinking water must also be raised, which puts forward higher requirements on water treatment technology. The resin method is particularly suitable for the removal and resource utilization of trace toxic organics and trace inorganic pollutants (heavy metals, etc.) in water, so it will further play its role in deep purification.
      Some teams have recently developed a series of magnetic styrene and magnetic acrylic resins, as well as magnetic ultra-highly cross-linked adsorption resins, and some have achieved industrial production. Good results have been achieved in the advanced treatment of tail water.
      Compared with the internationally well-known (the only industrialized) magnetic resin product (MIEX), NDMP resin has large exchange capacity, high mechanical strength, low cost and high regeneration rate. The adsorption performance and regeneration efficiency are significantly higher than those of Australia and the United States. The treatment effect of printing and dyeing wastewater is also very good. This technology has been applied and promoted in water projects. It has also been industrially used in Nantong, Changzhou, Zhengzhou, Henan and other places.
      In the aspect of nanocomposite resin removal of inorganics: as we all know, metal oxides and metal phosphate nanoparticles have high surface activity, strong adsorption selectivity for pollutants, easy regeneration, cheap and easy to obtain, but there are also weaknesses in application performance, that is, thermodynamics Unstable, easy to agglomerate; small particle size, large pressure drop or difficult separation; unstable chemical properties of the particles.
      How to apply nanotechnology? A team has designed the preparation of supported nanocomposite adsorbents. Such nanoparticles have good dispersibility, controllable performance, easy separation, and long-term stable use. It has a good selective removal ability for heavy metals, arsenic, phosphorus and other trace pollutants in polluted water bodies. The key indicators such as processing capacity are much higher than the existing commercial environmental materials, and they can be regenerated and reused.
      This technology has been produced in medium-sized batches. It has achieved good practical application effects in the removal of nickel and phosphorus in the largest domestic Chuanyi electroplating plant (Three Gorges area) and AAC Electronics Plant in Hong Kong (Taihu Lake area). In the advanced treatment of Guangxi Huatin (drinking water source) mining and metallurgical wastewater, it also has a good removal effect on chromium, lead and arsenic. The technology has been applied to a number of special water projects, and has achieved good treatment effects in the advanced treatment of leather wastewater, significantly improving the utilization rate of water and chromium resources, and reducing the amount of chromium sludge produced.