There is a research on electrochemical degradation of phenol-containing coking wastewater for reference:
Abstract: Ti/Ir2O3/RuO2 was chosen as the anode, and C-PTFE gas diffusion electrode was used as the cathode to degrade simulated phenol-containing coking wastewater. Orthogonal experiments were utilized to find out the optimal operating conditions. The effects of phenol concentration, current density, electrolyte concentration and pH on phenol removal efficiency were investigated. The kinetic analysis of electrochemical degradation of phenol was carried out, and the results proved that the reaction was a first-order kinetic reaction. Keywords: orthogonal experiment; coking wastewater; degradation treatment; electrochemical method; phenol
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Wastewater containing phenolics comes from a wide range of sources, which is harmful. Coking plants, gas plants, gas generating stations produce large amounts of phenol-containing wastewater with phenol concentrations of 1000-3000 mg/l, and also contain oil, suspended solids, sulfides, ammonia nitrogen, cyanide and other pollutants. Petroleum refineries, shale refineries, wood preservation plants, wood distillation plants, as well as phenol as raw materials or synthetic phenol in various industries, such as resins, synthetic fibers, dyes, pharmaceuticals, spices, pesticides, explosives, glass fibers, paints, disinfectants, floatation agents, chemical reagents, and other industrial production processes can be produced in different quantities and the nature of phenol-containing wastewater.
Phenol-containing wastewater is discharged into the water body without treatment, which will jeopardize the reproduction and survival of aquatic organisms. Water containing phenol 0.1 ~ 0.2 mg / liter, the fish have phenol flavor; containing phenol 1 mg / liter, will affect the fish spawning and back to the swim, containing phenol 5 ~ 10 mg / liter, the fish will be a large number of deaths. Drinking water containing phenol can affect human health. Even if the concentration of phenol is only 0.002 mg/l, chlorine disinfection will produce chlorophenol odor. Crops irrigated with high concentrations of phenol-containing wastewater will wither and die.
There are many bodies of water in the world that are polluted by phenolic wastewater, such as the Mississippi River, the Rhine River, the Volga River, the Songhua River, and so on. Preventing the pollution of phenol wastewater on the environment has attracted widespread attention. On the research of phenol wastewater treatment technology, the United Kingdom, the Soviet Union as early as in the 1930s began to carry out, China began in the 1950s. Some countries have built structures to treat phenol wastewater and carried out a wide range of research work. There are two basic ways to solve the problem of phenol wastewater. One is to reform the process to reduce the concentration of phenol in wastewater, or recycling of wastewater to reduce the amount of discharge. For example, some of China's gas stations using a closed loop system to eliminate the phenol pollution of rivers; the Soviet Union coking plant phenol wastewater mixed into other industrial cooling water recycling system; the United States Dow Chemical Company to the production of phenol and chlor-alkali into a "closed loop production circle", not discharged wastewater. The second is the recycling of wastewater. Phenol is an important chemical raw material. Phenol extraction from wastewater is an important source of phenol. German Federal **** and the country from the coking plant, gas plant phenol-containing wastewater recycled phenol up to 10,000 tons per year.
The high concentration of phenol-containing (phenol greater than 1,000 mg / l) wastewater is usually recovered first, and then harmless treatment.
Recovery of phenol from wastewater methods in the past are:
Extraction method This method of phenol removal is highly efficient, a wide range of sources of extractant, is widely used. China has dozens of extractive phenol removal devices in operation. About one-third of the coking plants in the United States and one-quarter of the coking plants in Poland use solvent extraction to remove phenol. Commonly used extractants are benzene, heavy benzene, butyl acetate, light oil and so on. Pulse sieve plate extraction tower equipment is not very complex, phenol removal efficiency is generally 93 ~ 97%, commonly used in China. Figure 2 shows the flow chart of extraction and biological treatment of phenol-containing wastewater from a gas plant in China. This plant produces a high concentration of phenol-containing vaporized ammonia wastewater (containing phenol 2500 ~ 3000 mg / liter) by oil removal, precipitation, cooling, sent to the pulse extraction tower, phenol effluent (containing phenol 100 ~ 150 mg / liter) into the intermediate tank, mixed with low concentrations of phenol-containing final cooling wastewater, pumped into the aeration tank, the pool inlet wastewater phenol concentration of such as 50 mg / liter, the pool of phenol concentration of the effluent can be reduced to 0.5 mg / liter, and generally used for the treatment of phenol. The phenol concentration in the inlet wastewater of the pool is 50 mg/l, and the phenol concentration in the effluent of the pool can generally be reduced to 0.5 mg/l. Phenol in the extractant is combined with lye in the alkali washing tower as phenol sodium salt, and then enter the phenol sodium tank for sodium removal and phenol recovery. The extractant is alkaline washed, regenerated and recycled.
Centrifugal extractor is a device with high extraction efficiency, small volume, small solvent dosage, and de-phenolization rate up to 99%. The United States, Japan, the German Federal **** and the country has been used for production.
Steam de-phenolization method The earlier method of de-phenolization, simple operation, suitable for the treatment of wastewater containing volatile phenol-based. The essence of this method lies in the formation of phenol and water vapor *** boiling mixture, the phenol in the water into the steam and the wastewater is purified, and then wash the phenol-containing steam with lye to recover phenol. The phenol removal rate is about 80%. Some factories in the U.S.A. use this method to treat wastewater from tar extraction, p-isopropylbenzene-phenol production, etc., and have obtained 97% de-phenolization efficiency. This method does not use organic solvents, the quality of recovered phenol is good, the amount of treated water is large, the operation is relatively simple; but only the recovery of volatile phenol, the amount of steam is large, the phenol removal tower is huge, and the residual concentration of phenol in the wastewater is high.
Adsorption method The more widely used is activated carbon adsorption. The United States and the United Kingdom use this method to recover phenol from the water quality of the more simple chemical plants, pesticide plant wastewater. British Felson-Best Agricultural Chemical Company's wastewater by activated carbon adsorption treatment, phenol content from 800 mg / lift to 8 mg / liter, phenol removal efficiency of 99%. Activated carbon filter as a refinery wastewater highly purified equipment, has been used in China's Hunan Changling Oil Refinery, Beijing Dongfanghong Oil Refinery. Czechoslovakia is quite common with cheap adsorbent slag treatment of coking plant wastewater containing phenol, phenol removal efficiency of up to 75%. The United States with large pore adsorption resin from phenol wastewater recovery phenol success.
Ion exchange method Ion exchanger to remove phenol, weakly alkaline anion exchange resin adsorption and regeneration recovery of phenol for the best results. German Federal **** and the country as early as the 1950s with weakly alkaline anion exchange resin from gas plants, coking plants and other wastewater recovery of large amounts of phenol. China in the pharmaceutical industry has been widely used sulfonated coal filter phenol, Shanghai Sixth Pharmaceutical Factory sulfonated coal adsorption phenol efficiency of up to 98% or more.
Chemical precipitation method of adding chemicals to make the phenol in the wastewater to generate precipitates and separation and recycling, such as resin plant in the high concentration of phenol and formaldehyde in the wastewater by further evaporation and concentration of phenol and formaldehyde condensed phenolic resins; calcium oxide to make the peat gas station wastewater phenol, fatty acids into calcium salts and then further recycling.
Biological method of lower concentration of phenol wastewater without recycling value, or after recycling treatment containing tens to hundreds of milligrams of phenol per liter of wastewater need to be purified, and then discharged or reused. Commonly used purification methods are: ① activated sludge method: the treatment effect is good, low cost. With the progress of activated sludge biology research, activated sludge cultivation technology, especially the domestication and application of efficient phenol-breaking strains of bacteria, as well as the emergence of new high-performance devices, so that this method has become the main method of treatment of various types of phenol-containing wastewater. Phenol removal efficiency can reach 95-99%. Biofilter method: strong adaptability to load changes, simple operation and management. In recent years, plastic filter media filter, tower biofilter, bio-turntable, etc., to overcome the large footprint of the ordinary filter, the shortcomings of low processing efficiency, has been applied to coking plants, gas plants, chemical fiber plants containing phenol wastewater treatment. (iii) Oxidation pond method: the use of natural biological action for purification. The United States use more for the treatment of refineries, coking plants and other phenol-containing wastewater. This method of low treatment costs, but covers a large area, such as land conditions, can be considered.
In recent years. With the development of the power industry, especially in recent times, the development of hydroelectric power and nuclear power, the cost of electricity is reduced for the application of electrochemistry in the treatment of wastewater to open up a very good prospect.
The electrochemical methods used for wastewater treatment are electrolysis (oxidation or reduction), electrical capture method, electric coagulation method and electrodialysis method. Electrochemical methods have been used in electroplating wastewater, chemical wastewater, dye wastewater, paper wastewater, leather wastewater, biochemical wastewater and pharmaceutical wastewater wastewater and other wastewater treatment. As well as for the electrochemical synthesis of water treatment agents.
Electrolytic flocculation method for organic wastewater treatment Electrolytic flocculation method experiments with graphite as the cathode, the anode were used in stainless steel, aluminum and iron experiments, found that the effect of aluminum electrode is good, the tank voltage of 10V, the current density of 12.5/Am2, electrolysis for 12 h. Raw water COD2458mg/L , BOD5355.80mg/ L, TP 7078mg/ L, TN 37.59mg/L, suspended solids 670 mg/ L, chromaticity 160, after electro-coagulation, suspended solids removal rate of 100%, COD removal rate of 94.62%, BOD5 removal rate of 90.83%, tp removal rate of 100%, TN removal rate of 77.76%, chromaticity removal rate of 100%, indicating that there is a significant treatment effect, with simple equipment, easy operation, treatment of the advantages of low cost. It has the advantages of simple equipment, easy operation and low cost.
Indirect oxidation of sewage treatment Indirect oxidation is in the anodic reaction process, Mr. Cheng has a strong oxidation of chemically active substances, and then use these substances on the decomposition of difficult to degrade substances, chlorine, hypochlorite with the oxidation of organic intermediaries can be used as, the weaker the reduction potential, the better the oxidation of intermediary effect. Indirect oxidation has been verified in the oxidation of benzene, phenol, oil and chloride. Production of p-nitrophenol wastewater from nitrochlorobenzene, into the precipitation, extraction and separation, the phenol mass concentration is still several hundred milligrams per liter, and contains a large number of sodium chloride, the production of electrolysis can be used to produce chlorine and hypochlorite oxidation of wastewater organics, oxidation of the tailings still contain hypochlorite, and then mixed with the original water for further oxidation, the rate of de-phenolization up to 99%.