As an efficient enrichment and separation technology, the extraction method is based on the principle that different substances have different distribution coefficients in different solvents. The organic solvent is water-immiscible, used to oscillate together with the test solution, o that the target substance can be enriched in the organic phase. It is widely used in analytical chemistry, inorganic chemistry, radiochemistry, hydrometallurgy and chemical preparation due to its high selectivity, high recovery rate, simple equipment, easy operation, quick and easy automatic control，etc.
Polyvinyl alcohol can be water-insoluble hydrocarbons (by 100% ~ 120% polyvinyl alcohol quality) extraction and removal. Containing polyvinyl alcohol 0.3g / L of waste water at room temperature with 35% (mass) of hexane to 1000r / min stirring 10min, standing for 1h after stratification, the aqueous phase COD value of 86.5mg / L, COD The removal rate of 59.8%, such as repeated extraction three times, the COD reduction of 41.6mg / L is equivalent to 80.65% removal rate.
Adsorption method as a low-energy solid extraction technology, has an incomparable advantage in the treatment of dissolved organic matter. Adsorption method depends on the adsorbent on the dense channel, a large surface area or through the surface of various functional groups and adsorbed material molecules between multiple forces, to achieve the purpose of selective enrichment of organic matter. Adsorption has the advantage of refractory organic matter has a better removal effect.
Adsorption kinetics of PVA on activated carbon was studied. The results showed that when the initial concentration of PVA was 50mg / L, the active carbon concentration was 5g / L, the temperature was 20 ℃, the pH was 6.5, the stirring speed was 150r / min and the reaction time was 30min. The removal rate of PVA reached 92%.
1.3,Foam separation method
Foam separation method is to use the physical adsorption of foam and water interface to form a form of decontamination water purification method. It achieves the purpose of concentrating the surface-active substances or purifying the liquid phase by bubbling the solution and forming a foam layer, separating the foam layer from the liquid phase body. Foam separation technology with simple equipment, low energy consumption, less investment and other characteristics, widely used in chemical, pharmaceutical, sewage treatment and other fields.
Polyvinyl alcohol-containing waste water can pass into the air, so that the bubble overflow to remove PVA. 1m3 of polyvinyl alcohol wastewater containing COD843mg / L, at a speed of 1.8L / min into the air to remove the foam, after 78min, the volume of waste water reduced to 70% of the original, and COD value reduced to 193mg / L.
Other methods will be showed in the following articles.