Chemical wastewater is difficult to treat due to its complex water composition, high levels of by-products, high pollutant content, numerous toxic and harmful substances, dispersants or surfactants with bactericidal effects, and numerous biologically recalcitrant substances. According to the editor of Jianyi Chemical, commonly used methods include physical, chemical, biological, and physicochemical methods. Below, the editor will briefly introduce the most commonly used methods for treating chemical wastewater—— Chemical treatment method.
The main target of chemical coagulation method is small suspended solids and colloidal substances in water. Through the coagulation and flocculation caused by the addition of chemical agents (dispersants), the colloids are stabilized and precipitated to be removed. The coagulation method can not only remove fine suspended particles ranging from 10-3 to 10-6mm from wastewater, but also remove color, microorganisms, and organic matter. This method is greatly affected by changes in water temperature, pH value, water quality, water quantity, etc., and has a low removal rate for certain soluble organic and inorganic substances.
Chemical oxidation is usually a method of oxidizing and removing organic pollutants from chemical wastewater using oxidants (dispersants). Through chemical oxidation-reduction, wastewater can transform toxic organic and inorganic substances into non-toxic or less toxic substances, thereby achieving the goal of wastewater purification. Commonly used methods include air oxidation, chlorine oxidation, and ozone oxidation. Air oxidation is mainly used for the treatment of wastewater containing highly reducing substances due to its weak oxidation ability. Cl2 is a commonly used oxidant, mainly used for the treatment of organic wastewater containing phenol, cyanide, etc. Ozone is used for wastewater treatment, with strong oxidation ability and no secondary pollution. Ozone oxidation and chlorine oxidation methods have good water treatment effects, but they have high energy consumption and cost, and are not suitable for treating chemical wastewater with large water volume and relatively low concentration.
Electrochemical oxidation is a process in which organic pollutants in wastewater are removed from the electrode through redox reactions in an electrolytic cell. In addition to losing electrons and being oxidized at the anode of the electrolytic cell, pollutants such as Cl - and OH - in the water can also be discharged at the anode to generate Cl2 and oxygen, indirectly oxidizing and destroying the pollutants. In fact, in order to enhance the oxidation effect of the anode and reduce the internal resistance of the electrolytic cell, some sodium chloride is often added to the wastewater electrolytic cell for so-called electrochlorination. After adding NaCl, chlorine and hypochlorite ions can be generated at the anode, which also has a strong oxidizing effect on inorganic and organic substances in water. In recent years, some new electrode materials have been discovered in the fields of electro oxidation and electro reduction, achieving certain results. However, there are still problems such as high energy consumption, high cost, and the presence of side reactions.
Due to the complex composition and diverse types of chemical wastewater, it is necessary for everyone to choose the treatment method according to the actual situation in order to achieve efficient treatment. Of course, in addition to chemical methods mentioned above, dispersants or other surfactants are definitely needed to treat wastewater, and the effect will be more ideal. Of course, the cost of additives for wastewater treatment is not high, and it is also a reasonable choice!
