Activated carbon adsorption is a highly effective method for treating industrial wastewater.

There are four conventional methods for wastewater treatment: physical treatment, chemical treatment, physicochemical treatment, and biological treatment. Physical treatment methods can only treat insoluble and suspended substances in industrial wastewater. Common methods used in this process include stirring, centrifugation, and filtration. Chemical treatment methods involve adding specific chemicals to industrial wastewater to precipitate certain ions, followed by sedimentation or filtration to remove insoluble matter. Common methods in this process include chemical precipitation, neutralization, coagulation, and oxidation-reduction methods. Physicochemical methods mainly treat harmful substances in industrial wastewater through adsorption, membrane separation, and ion exchange; activated carbon adsorption is one such method. Biological treatment methods utilize the normal metabolic activities of microorganisms to consume organic matter in solution, colloid, and finely suspended states in industrial wastewater, converting them into stable and harmless substances. This method can be further divided into anaerobic biological treatment and aerobic biological treatment based on the treatment mechanism.

Activated Carbon Adsorption for Industrial Wastewater Treatment

1. Principle

Activated carbon is made by activating carbonaceous materials such as wood, coal, and fruit shells under high temperature and oxygen-deficient conditions. It has numerous micropores and a huge specific surface area; typically, 1 gram of activated carbon has a surface area of 500-1500 micrometers, thus possessing a strong physical adsorption capacity and effectively adsorbing organic pollutants in wastewater. Furthermore, during the activation process, oxygen-containing functional groups, such as carboxyl groups (-COOH), hydroxyl groups (-OH), and carbonyl groups, are formed on the non-crystalline sites of the activated carbon surface. These groups give activated carbon chemical adsorption and catalytic oxidation and reduction properties, effectively removing some metal ions from wastewater. Activated carbon has a strong adsorption capacity, adsorbing tiny particles in industrial wastewater, causing them to precipitate and be discharged, achieving the purpose of wastewater treatment. Due to its porous structure, activated carbon has a large number of micropores on its surface, with diameters generally on the nanometer scale. This results in a very large relative surface area of activated carbon, generating a powerful adsorption effect on fine particles from the outside world.

Besides allowing activated carbon to adsorb wastewater naturally, hot air can be used to continuously supply oxygen to the activated carbon during the adsorption process. This gradually enhances the adsorption capacity of the activated carbon under ventilation and heating conditions, resulting in a more significant wastewater treatment effect.

2. Advantages of Activated Carbon Adsorption for Industrial Wastewater Treatment

The advantages of activated carbon adsorption for industrial wastewater treatment are:

1. Good and relatively stable treatment effect;

2. Improved resistance of microorganisms to organic toxins and heavy metals;

3. Production of cohesive carbon particles and microorganisms, forming a solid and dense sludge, improving the operating conditions of the activated sludge process;

4. Activated carbon can adsorb surface-active substances, solving the foaming problem in aeration tanks;

5. Applicable to wastewater with complex composition and varying concentrations and volumes;

6. Low cost of powdered activated carbon.

Activated carbon adsorption is a physicochemical method among the aforementioned industrial wastewater treatment methods. Clearly, it can not only physically adsorb many insoluble harmful substances, but also effectively chemically adsorb harmful ions in an ionic state, combining the advantages of both physical and chemical treatment methods. Furthermore, activated carbon exhibits particularly high efficiency and quality in treating industrial wastewater. Due to its porous structure, activated carbon has a very large relative surface area, giving it a highly efficient adsorption capacity. Simultaneously, its carbon chain structure provides it with great rigidity, allowing it to maintain its shape and structure during use, effectively performing its adsorption function.

Activated carbon adsorption possesses the advantages of physical wastewater treatment methods, directly adsorbing free heavy metal ions such as mercury and chromium, as well as minute impurities in wastewater. The addition of additional chemical additives reduces the cost of industrial wastewater treatment to some extent and avoids the potential hazards associated with the use of chemical additives. Besides the advantages mentioned above, the low production cost of activated carbon is also a key reason why it is chosen for treating industrial wastewater. Activated carbon originates from organic waste in daily life. After simple carbonization and gas treatment, it becomes activated carbon for industrial use. During the wastewater treatment process, the structure and properties of activated carbon remain unchanged, making recycling and reuse possible. Through simple rinsing with water and drying with detergent, the activated carbon can be used again to treat wastewater. This low-cost and effective method of industrial wastewater treatment has been widely used by many factories.

Application of Activated Carbon Adsorption in Industrial Wastewater Treatment

1. Treatment of Oily Industrial Wastewater with Activated Carbon Adsorption

For oily polluted industrial wastewater, such as seawater pollution caused by oil tanker leaks or oily waste from factories, multi-stage treatment is required to meet standards. Since petroleum is an organic substance, only substances with good compatibility can adsorb and remove it. Activated carbon has good hydrophilicity but poor oleophilicity, resulting in a certain upper limit to its adsorption capacity for oil. This necessitates first subjecting oily industrial wastewater to organic matter adsorption and multi-stage treatment, followed by final treatment with activated carbon to completely adsorb the oil.

2. Activated Carbon Adsorption Method for Treating Industrial Wastewater Containing Heavy Metal Ions

Industrial wastewater is mostly waste liquid from chemical reactions, containing large amounts of unreacted toxic heavy metals such as mercury and chromium. If these metals are discharged into rivers without treatment, they pose a fatal danger to plant growth and the metabolism and respiratory system of animals. Activated carbon has a strong adsorption capacity for low concentrations of mercury, the most toxic substance in industrial wastewater, effectively removing mercury ions. However, when the mercury concentration is high, chemical methods must be used to precipitate the mercury before activated carbon can completely adsorb the remaining mercury ions. Although the mechanism of activated carbon treatment for chromium-containing industrial wastewater is complex, involving physical adsorption, chemical reduction, and physicochemical adsorption of chromium, the effect is excellent. Generally, activated carbon adsorption alone can remove chromium ions from chromium-containing wastewater.

3. Activated Carbon Adsorption for Treating Pigment-Containing Industrial Wastewater

The development of the textile industry, especially the garment and paper industries in recent years, and the incomplete treatment of wastewater generated during production processes, have led to a significant increase in the discharge of pigment industrial wastewater. Due to the complex composition, high concentration, and deep color of this type of industrial wastewater, it is difficult to treat it using activated carbon alone. Generally, the common treatment method for pigment industrial wastewater is to first oxidize and adsorb the wastewater, then perform membrane separation and multi-stage degradation, and finally use activated carbon for deep decolorization. The strong adsorption capacity of activated carbon for color makes it a promising candidate for treating pigment wastewater.