A The adsorbent should have the following properties: good adsorption selectivity, strong adsorption capacity, low adsorption equilibrium concentration, easy regeneration and reuse, good mechanical strength, stable chemical properties, wide source and low price. Before practical application, the adsorbent should also be made into porous fine particles so that the adsorbent has a larger surface area. The adsorbents currently used in wastewater treatment include: activated carbon, activated coal, clay, diatomaceous earth, activated alumina, coke, resin adsorbents, slag, wood chips, coal ash, humic acid, etc. Here we focus on activated carbon, which is widely used in wastewater treatment.
Activated carbon is made from carbon-based substances (such as wood, charcoal, coconut shells, coal, waste paper pulp, etc.) as raw materials. After being crushed and formed with a binder, it is heated, dehydrated, carbonized, and activated. Activated carbon is a non-polar adsorbent. Activated carbon has good adsorption performance and stable chemical properties, can withstand strong acids and alkalis, and can withstand flooding and high temperatures.
There are two types of activated carbon used in wastewater treatment: powder and granular. Powdered activated carbon has strong adsorption capacity, is easy to prepare, and has low cost, but it is difficult to regenerate and is not easy to reuse. The adsorption capacity of granular activated carbon is lower than that of powdered activated carbon, and the production cost is higher. However, it can be reused after regeneration, and the working conditions are good during use, and the operation and management are convenient. Therefore, granular activated carbon is mostly used in wastewater treatment.