For many years, activated carbon has been a popular water treatment. It is frequently used when water used in the manufacturing process comes into contact with recalcitrant organic compounds, which must be removed or drastically reduced in order to comply with a discharge permit.
Activated carbon filtration is typically used in conjunction with, and often downstream of, other treatment systems in chemical plants, with the science being that each process removes specific groups of pollutants, resulting in a wastewater discharge that is 'within spec.'
Organic waste materials such as coconut shell, orange peels, and banana peels can be used to produce activated carbon. Phosphoric acid can be used for chemical activation (H3PO4).
How to Recycle Activated Carbon?
The massive surface area is GAC's simplicity – but also its disadvantage, because there won't be enough 'clean' carbon left over time for the unwanted compounds to be absorbed, and the carbon media will need to be replaced.
It can be returned to a reprocessing facility and regenerated in some cases. In a reactivation furnace, the used carbon is heated to over 800°C. It vaporizes the undesirable organics, and special precautions are taken to ensure that emissions are safely controlled, typically by using an afterburner. However, doing so requires a significant portion of the energy that was used to create it in the first place.
An environmentally friendly alternative
However, depending on the composition of the water to be treated, the research indicates that in many cases, a granular activated carbon (GAC) treatment system may not be the best solution for the removal of many volatile organic compounds, especially when the overall environmental impact of a GAC system is considered.
Overall, GAC systems are reasonably predictable and may be cost-effective in some smaller systems with low influent organic loading and media that only needs to be changed two or three times per year. However, if you performed an environmental audit on a GAC-based water treatment system, it would not score very well in the long run due to the initial energy and resource use, replenishment/disposal, and transportation elements involved.
A GAC-based system is essentially an example of linear consumption with little or no recycling options and a lot of energy use – the primary factor in its large carbon footprint.
Low Budget, Money Saving Activated Carbon
From agricultural waste materials such as coconut shell, coconut shell fibers, and rice husk, a variety of low-cost activated carbons can be created. The low-cost activated carbons are fully characterized and used to remediate various pollutants from industrial wastewater, such as chemical oxygen demand (COD), heavy metals, anions, and so on.