From a professional perspective, the so-called electrochemical water treatment technology uses an external electric field to achieve the expected removal of pollutants in wastewater through a series of designed chemical reactions, electrochemical processes or physical processes in a specific electrochemical reactor. or the purpose of recycling useful materials.
As early as the 1930s and 1940s, foreign scholars proposed the use of electrolysis to treat wastewater. At that time, it was mainly used to treat heavy metal ions in wastewater. However, due to high energy consumption, lack of electricity and limitations of electrochemical theory, the development of this method was slow. In the 1960s and 1970s, the electric power industry developed rapidly. The research on coated titanium anodes was successful and industrialized. The continuous deepening of electrochemical theoretical research confirmed that the redox reactions, addition reactions or decomposition reactions of many organic compounds can be Conducted on electrodes, this provides a theoretical basis for the degradation of organic pollutants through electrocatalytic oxidation, thus promoting the application of electrolysis technology in water treatment.
1.Electron transfer is only carried out between the electrode and wastewater components, without the need to add additional redox agents, avoiding secondary pollution problems caused by additional additives.
2.The reaction conditions can be adjusted at any time by changing the applied current and voltage, and the controllability is strong.
3.The free radicals that may be generated during the process directly react with the organic pollutants in the wastewater indiscriminately, degrading them into carbon dioxide, water and simple organic matter, with no or little secondary pollution.
4.The reaction conditions are mild, and the electrochemical process can generally be carried out at room temperature and pressure.
5.Reactor equipment and its operation are generally relatively simple and, if properly designed, not expensive.
6.If the scale of sewage discharge is small, on-site treatment can be achieved.
7.When wastewater contains metal ions, the cathode and anode can work at the same time (the cathode reduces metal ions and the anode oxidizes organic matter) to maximize the treatment efficiency while recovering and reusing valuable chemicals or metals.
8.It can be used as a separate treatment or combined with other treatments. For example, as a pre-treatment, it can improve the biodegradability of wastewater.
9.It has the functions of air flotation, flocculation and disinfection.
10.As a cleaning process, its equipment occupies a small area and is particularly suitable for sewage treatment in crowded cities.
Theoretically, all organic matter in aqueous solution can be electrically oxidized before the oxygen evolution reaction, but due to kinetic reasons, the speed is very slow, and direct oxidation to CO2 is even more difficult.
The ease of electrochemical oxidation of organic substances can be evaluated by the so-called electrochemical oxidizability index (EOI). The larger the value, the easier it is to oxidize. The EOI also reflects the average current efficiency that can be achieved during electrolysis. Another evaluation index is electrochemical oxygen consumption (EOD), which refers to the amount of electricity required to electrochemically oxidize each gram of organic matter equivalent to the number of grams of oxygen produced during electrolysis. EOD can be calculated by the following formula
EOD=Wo2/W=(It/4F) (EOI) (32/Worg)(10-1)
In the formula, I,t - electrolysis current and electrolysis time (at this moment, the instantaneous current efficiency drops to zero);
Worg - the weight of organic matter converted;
F--Faraday's constant.