water Treatment

Activated carbon is a special type of carbon that can adsorb various molecules, which are adsorbed in the large surface area by van der Waals forces. A gram of activated carbon has a surface area that can be as large as a football field, this means a surface area of 500 to 2000 m2/g and sometimes even more. The surface area of activated carbon is divided into micro, meso and macro pores which have a significant impact on the efficacy of their applications in water treatment. Activated carbon therefore works on the basis of adsorption (ie not absorption). “Adsorption is the adhesion of atoms, ions or molecules from gas, liquid or dissolved solids to a surface. This proses differs from absorption, in which a fluid is dissolved by or permeates a liquid or a solid.” When using activated carbon in, for example, water or gas or air, the molecules that one wants to remove eventually end up via diffusion in the pore structure of the activated carbon where the adsorption takes place.

Activated carbon can be manufactured through various processes and from various carbon-containing raw materials or feedstocks. Often raw materials such as, coal, brown coal, charcoal, coconut shells and other feedstocks are used. After the raw material has been processed through pyrolysis, the carbon is further activated.  One such process is the steam activation process which involves a carbon source which is first carbonized and then activated at around 1000 degrees with steam. Another process is chemical activation involving chemicals, for example phosphoric acid, a raw material is impregnated and then activated at around 500 degrees.

Some of the benefits in the use of Activated Carbon amongst others is a very high removal capacity for organic components, a cost-effective product with good price performance and potential for re-use through regeneration.

Activated carbons are used extensively as an adsorbent for the removal of a wide range of contaminants from liquids and gases. The industry applications are wide and extensive inclusive of the following:

• • Potable water or wastewater purification
  • Removal of PFAS; Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a large group of man-made chemicals that have been used in industry and consumer products worldwide since the 1950s. Most exposures occur through drinking contaminated wateror eating food that contains PFAS
  • Removal of BTEX; benzene, toluene, ethylbenzene, and xylene compounds are common water resource and potable water pollutants that are often left undetected and untreated by municipal treatment systems in spite of the negative repercussions associated with their ingestion
  • Removal of colours and odours
  • Removal of contaminants of emerging concern (CEC’s) This is a term used by water quality professionals to describe pollutantsthat have been detected in water bodies, that may cause ecological or human health impacts, and typically are not regulated under current environmental law Sources of these pollutants include agriculture, urban runoff and ordinary household products (such as soaps and disinfectants) and pharmaceuticals that are disposed to sewage treatment plants and subsequently discharged to surface waters