Adsorption with Activated Carbon

Adsorption is the procedure of collecting soluble substances inside a solution on an appropriate interface. In wastewater treatment, adsorption along with activated carbon - a solid interface - usually follows normal biological treatment, and is aimed at erasing a portion of the remaining dissolved organic matter. Particulate matter present within the water might also be removed. Activated carbon is produced through heating char to a high temperature and then activating it through exposure to an oxidizing gas at high temperature. The gas develops a porous structure within the char and therefore creates a huge internal surface area. The activated char could then be separated within several sizes along with various adsorption capacities. The two most general types of activated carbon are granular activated carbon (GAC), that has a diameter greater than 0.1 mm, and powdered activated carbon (PAC), that has a diameter of less than 200 mesh. A fixed-bed column is frequent used to bring the waste-water into contact along with GAC. The water is applied to the top of the column and withdrawn from the bottom, although the carbon is held in place.

Backwashing and surface washing are applied to limit headloss build-up. Expanded-bed and moving-bed carbon contactors have been established to overcome the problem of headloss build-up. Within the expanded-bed system, the influent is introduced at the bottom of the column and is permitted to expand. In the moving-bed system, spent carbon is continuously replaced with fresh carbon. Spent granular carbon could be regenerated through removal of the adsorbed organic matter from its surface by oxidation in a furnace. The capacity of the reproduced carbon is slightly less than that of the virgin carbon. Wastewater treatment using PAC involves the addition of the powder directly to the biological treatment effluent or the physiochemical treatment process, as the case may be. PAC is usually added to wastewater in a contacting basin for a certain length of time. It is then allowed to settle to the bottom of the tank and removed. Removal of the powdered carbon might be facilitated through the addition of polyelectrolyte coagulants or filtration through granular-medium filters. A major problem with the use of powdered activated carbon is that the methodology for its regeneration is not well defined.