DSA, MOC and BDD, which ones can you understand?

Today We will briefly talk to you about the research related to electrochemical water treatment technology. What can you understand about DSA, MOC and BDD in the title? In fact, they are three capital English abbreviations, which represent three different types of electrodes, and also represent the three most popular research directions of electrochemical water treatment technology today.

First of all, DSA electrode is called Shape Stable Anode, the full English name is Dimensionally Stable Anodes. This electrode is an anode based on titanium and covered with a metal oxide active coating. The production method is also very simple. First, find an inert metal plate as the base material. The most commonly used one is titanium metal. Clean the surface with acid and then apply a catalyst layer on it (the effective component of the catalyst is usually a variety of precious metal oxides in different proportions. (complete), after brushing one layer, go to high-temperature sintering, and then brush and burn again. By repeating this process, a noble metal oxide film several microns thick can eventually be deposited on the surface of the substrate. It is this film that plays a catalytic role. This film has good electrocatalytic activity, conductivity, and oxidation resistance. Small pole distance change, strong corrosion resistance, good mechanical strength and processing performance, long life, low cost, and good electrocatalytic performance for electrode reactions, which is beneficial to reducing the overpotential of oxygen evolution and chlorine evolution reactions and saving electric energy .

Next, let's talk about the MOC electrode. The MOC electrode is also a type of DSA electrode. Compared with the traditional ruthenium-iridium electrode, the MOC electrode is doped with a portion of graphene material. From the appearance point of view, there is not much difference between MOC electrodes and ruthenium-iridium electrodes. The base materials are the same, either titanium plates or titanium mesh, and the coating is also a black layer, and the difference is almost invisible. What is the role of adding graphene?

According to reports, there are the following three benefits:

1. Since graphene has a large specific surface area, its addition can increase the contact surface between the catalytic coating and water, thereby improving current utilization efficiency.

2. Since graphene also has certain adsorption properties, it can enrich the target pollutants in the water to the surface of the anode, and then use direct oxidation and indirect oxidation of electrolysis to remove the pollutants.

3. Since graphene has good electrical conductivity, its addition can appropriately reduce the overall resistance of the anode, thereby reducing ineffective power consumption caused by heat and saving energy.

In short, its ultimate purpose is to extend the service life, improve the treatment effect, thereby reducing the annual operation and maintenance costs caused by plate depreciation, and increase the competitiveness of electrocatalytic technology in the market and other advanced oxidation processes. But the price is almost 2-3 times that of DSA. The price of MOC electrodes is about 2.3w/m², which is almost twice that of ruthenium and iridium electrodes. You need to consider the cost when purchasing.

The full name of BDD electrode is called boron-doped diamond film electrode. Because of the good catalytic properties of diamond (actually C), it becomes a potential electrode material. However, pure diamond is an insulator and does not conduct electricity. In order to overcome this shortcoming, people found ways to incorporate boron atoms into it and obtained boron-doped diamond, which can effectively improve the conductive properties of diamond, so the later BDD electrode technology was born.

Compared with DSA electrode, BDD electrode has better chemical stability and higher oxygen evolution potential, and its electrochemical window is wider and can effectively decompose more types of organic pollutants. Therefore, in terms of treatment effect, BDD Electrodes do have great potential in wastewater treatment, but BDD electrodes are still very expensive so far.

Someone has done experiments. For the same kind of wastewater, with the same current density and the same effluent quality results, the current efficiency of the ruthenium-iridium electrode is equivalent to removing 20 mg/L of COD per ton of water per kilowatt hour, while the BDD electrode removes 20mg/L of COD per ton of water per kilowatt hour. Electricity can remove 60mg/L COD, which is 3 times the former. This means that to remove the same mass of COD, the BDD electrode required is 1/3 of the ruthenium-iridium electrode. However, given that the cost of the BDD electrode is about 8 times the cost of the ruthenium-iridium electrode, in terms of current efficiency alone, It cannot cover the high cost disadvantage of BDD electrodes.

Summarizing these three electrodes, whether in terms of theoretical service life, cost, current efficiency, or technological novelty, they are all DSA ≤ MOC ≤ BDD. From the perspective of final engineering application, DSA electrodes still occupy the majority of the market. MOC and BDD still have a long way to go if they want to surpass traditional DSA electrodes in terms of market share.