Application of activated carbon in water treatment

According to statistics, the industrial wastewater discharged every year in my country is about 8×108m3, which not only contains cyanide and other highly toxic components, but also contains metal ions such as chromium, zinc and nickel. There are many wastewater treatment methods, mainly chemical precipitation method, electrolysis method and membrane treatment method, etc. This article introduces the activated carbon adsorption method. Activated carbon has a huge surface area and has high physical adsorption and chemical adsorption functions. Therefore, the activated carbon adsorption method is widely used in wastewater treatment. And it has the characteristics of high efficiency and good effect

Classification of activated carbon

There are many types of activated carbon used in production. Generally made into powder or granular.

Powdered activated carbon has strong adsorption capacity, is easy to prepare and low in price, but it is difficult to regenerate and generally cannot be reused.

The granular activated carbon is more expensive, but it can be reused after regeneration, and the working conditions during use are better, and the operation and management are convenient. Therefore, granular activated carbon is often used in water treatment [1].

Activated carbon adsorption

"Activated carbon adsorption" refers to the use of the solid surface of activated carbon to adsorb one or more substances in water to achieve the purpose of purifying water.

Factors affecting the adsorption of activated carbon

Adsorption capacity and adsorption speed are the main indicators to measure the adsorption process. The size of the adsorption capacity is measured by the amount of adsorption. The adsorption rate refers to the amount of material adsorbed by the unit weight of the adsorbent in a unit time. In water treatment, the adsorption speed determines the contact time of the sewage with the adsorbent.

The adsorption capacity of activated carbon is related to the pore size and structure of activated carbon. Generally speaking, the smaller the particles, the faster the pore diffusion rate, and the stronger the adsorption capacity of activated carbon.

The pH value and temperature of sewage also affect the adsorption of activated carbon. Activated carbon generally has a higher adsorption capacity under acidic conditions than under alkaline conditions. The adsorption reaction is usually exothermic, so low temperature is beneficial to the adsorption reaction.

Of course, the adsorption capacity of activated carbon is related to the concentration of sewage. At a certain temperature, the adsorption capacity of activated carbon increases with the increase in the equilibrium concentration of adsorbed substances.

Application of activated carbon in sewage treatment

Because activated carbon has high requirements for water pretreatment and the price of activated carbon is expensive, in wastewater treatment, activated carbon is mainly used to remove trace pollutants in wastewater to achieve the purpose of deep purification.

Activated carbon treatment of chromium-containing wastewater

Chromium is a metal raw material used in electroplating. Hexavalent chromium exists in different forms with different pH values in wastewater.

Activated carbon has a very developed microporous structure and a high specific surface area. It has a strong physical adsorption capacity and can effectively adsorb Cr (VI) in wastewater. There are a large number of oxygen-containing groups on the surface of activated carbon, such as hydroxyl (-OH), carboxyl (-COOH), etc., all of which have the function of electrostatic adsorption and chemical adsorption of Cr (VI). It can be used to treat Cr(Ⅵ) in electroplating wastewater, and the adsorbed wastewater can meet the national discharge standard.

The test shows that when the mass concentration of Cr(Ⅵ) in the solution is 50mg/L, pH=3, and the adsorption time is 1.5h, the adsorption performance of activated carbon and the removal rate of Cr(Ⅵ) reach the best effect.

Therefore, the process of using activated carbon to treat chromium-containing wastewater is the result of the comprehensive effects of activated carbon on the Cr(Ⅵ) in the solution, such as physical adsorption, chemical adsorption, and chemical reduction. Activated carbon treats chromium-containing wastewater with stable adsorption performance, high treatment efficiency, low operating costs, and certain social and economic benefits.