Paper water treatment defoamer is mainly used in pulping and papermaking processes from the paper industry. The main components of this process are lignin, cellulose, volatile organic acids, etc., with high pollutant concentration, large emissions, difficult to degrade, poor biodegradability and other characteristics, is one of the more difficult to treat industrial wastewater.






The common treatment method of papermaking wastewater is coagulation, which has strong adaptability, simple equipment and convenient operation, but has some disadvantages such as high cost and large sludge production. Another method is the biological method, which has the characteristics of no secondary pollution and low treatment costs, but can not completely reduce the content of organic pollutants. In recent years, scholars at home and abroad have studied the application of talc as coagulant, coagulant and filter aid in the treatment of papermaking wastewater.






Oily wastewater treatment defoamer is mainly used in the oil industry, steel, gas work stations, machinery industry cooling lubrication fluid, etc. The oil surface covering in the wastewater makes the water lose self-purification ability, destroy the ecological balance in the water, not only harm human health, but also affect the production of crops. At present, gas floatation is the main method to treat oily wastewater, but this method has high energy consumption, large amount of flocculant and large area. Other methods such as electrochemical method and adsorption method also have disadvantages such as high operating cost and small application scope.






In recent years, the study of defoaming powder as oil absorbent has provided a new way to treat oily wastewater. Yu Yan Hwan et al examined the effect of talc dosage and particle size on the purification of oil-bearing wastewater by cyclone streamers. The results show that when the fineness of talc (150g/m3 water) is 0.074mm, the oil removal rate is 78.30%. The oil removal effect of talc on the cyclone runner is remarkable, and the oil removal rate is about 5% higher than that without talc. There are also researchers to examine the effectiveness of talc treatment of oily wastewater under different conditions.






The results show that under the conditions of 20℃, 20g/L talc dosage and 15min slow stirring, the COD removal rate of gasoline is 97.8% and that of diesel is 81.5%. Talc is a natural hydrophobic oleophilic mineral, which can promote the separation of hydrophobic oleophilic particles in oil and water, so talc powder can be used as an oil absorption agent to treat oil-bearing wastewater.




1 Treatment of dye wastewater


Dye wastewater has complex components and deep chroma, which causes serious pollution to the environment. Because cationic dye wastewater contains complex aromatic groups, it is difficult to biodegrade and decolorize, and its biodegradability is poor, so the dye wastewater is not easy to treat. Traditional treatment methods of dye wastewater (filtration, coagulation, etc.) only convert pollutants from liquid phase to solid phase or gas phase, but do not completely remove pollutants, and it is easy to cause secondary pollution. Therefore, the management technology of low cost, good effect and green environmental protection is being continuously developed.


2 Treatment of aromatic organic wastewater


With the development of petrochemical, plastics and other industries, more and more waste water containing aromatic compounds are discharged from factories. This kind of waste water pollutants have stable structure and are difficult to degrade. At present, the main methods for treating organic waste water of aromatic compounds are advanced oxidation and liquid membrane technology separation. The liquid film used in the latter is easy to age, and there are also problems such as membrane pollution and high cost.


The effect of defoaming powder on wastewater treatment is significant, mainly depending on the structure and nature of the wastewater:


(1) Unique pore structure and large specific surface area;


(2) Surface functional groups OH -, H-O-H, SI-O are active;


(3) Natural hydrophobic lipophilic;


(4) Chemical stability. The modification methods of defoamer for water treatment mainly include surface covering modification method, mechanical crushing modification method, ultrasonic treatment method and acidification modification method. After modification, the defoamer can increase the specific surface area, enhance the surface activity and improve the adsorption performance, so it can be used to treat wastewater.


The author suggests that future work should focus on the following aspects:


(1) There are few modification methods for defoaming powder as a water treatment agent. Based on its own characteristics, local active modification methods or outer film layer modification methods should be expanded to improve the selectivity of modified talc for adsorption of specific pollutants. In addition, the problem of acid discharge in acidified talc should also be emphasized.


(2) The waste water treated by defoamer is mostly laboratory simulated waste water or waste water with single pollutant. Whether the defoamer can be put into the actual production operation in large quantities remains to be investigated;


(3) Studies have shown that the hybrid mixture of SN (octadecyl dimethyl hydroxyethyl quaternary ammonium) and magnesium silicate can adsorb anions in dye wastewater, and the interlayer structure of magnesium silicate is similar to talc, so the hybrid of talc and SN can be considered for the removal of anions in dye wastewater.


(4) According to the characteristics of talc, such as lubricity and adsorption, the filtration effect of defoaming powder in membrane separation technology can be examined;


(5) Research on the recycling and reuse methods of defoamer should be strengthened to provide a theoretical basis for further development of the application of defoamer in water treatment.


With the in-depth study of decontamination of water pollution by defoaming powder and the continuous development of talc processing modification technology, it is expected that defoaming powder will have a major breakthrough in water treatment.