Activated carbon is a porous carbon-containing substance. It has a highly developed pore structure and is an excellent adsorbent. The adsorption area per gram of activated carbon is equivalent to eight tennis courts. And its adsorption is achieved by physical Sexual adsorption and chemical adsorption are achieved. In addition to carbon elements, its constituent materials still contain a small amount of hydrogen, nitrogen, oxygen and ash, and its structure is formed by the accumulation of six rings formed by carbon. Due to the irregular arrangement of the six-ring carbon, the activated carbon has the characteristics of multi-microporous volume and high surface area.
Activated carbon can be made from a wide variety of carbonaceous materials including wood, sawdust, coal, coke, peat, lignin, fruit stones, hard nut shells, sugar pulp, bone, lignite , petroleum residue, etc. Among them, coal and coconut shell have become the most commonly used raw materials for making activated carbon. The manufacture of activated carbon is basically divided into two processes. The first process includes dehydration and carbonization. The raw material is heated and dried at a temperature of 170 to 600°C, and about 80% of the original organic matter is carbonized. The second process is to activate the charcoal, which is accomplished by reacting with an activator such as water vapor and charcoal. In the endothermic reaction, a mixed gas composed of CO and H2 is mainly produced, which is used to burn and heat the charcoal to an appropriate temperature (800 to 1000°C) to burn off all decomposable substances in it, resulting in a developed microporous structure and a huge specific surface area, so it has a strong adsorption capacity.
The pores of activated carbon can be divided into three categories according to the size of the pores. Large holes: Radius 1000 - 1000000 A. Transition hole: Radius 20 - 1000 A. Microwell: Radius - 20 A.
Activated carbons made from different raw materials have different pore sizes. Activated carbon made from coconut shell has the smallest pore radius. Wood-based activated carbons generally have the largest pore radii, they are used to adsorb larger molecules, and are almost exclusively used in the liquid phase. The first type of granular activated carbon used in municipal water treatment was made from wood and was called charcoal. Coal-based activated carbon has a pore size somewhere in between.
