Activated carbon is depleted by adsorbing organic compounds.
Activated carbon is a porous material that has the natural ability to adsorb organic compounds from gases and liquids. To increase this porosity, we subject these raw materials, such as wood charcoal or coconut shell charcoal, to steam at high temperature in a furnace (800-1200 °C). The resulting product is called granular activated carbon (GAC), which could also be called as industrially produced carbon with more pores. The most common applications of GAC granular activated carbon for industrial applications are: wastewater effluent treatment, drinking water purification and removal of organic compounds from liquid streams or gases. Spent granular activated carbons are virtually a waste product for industry and in some cases a problem to handle as a waste for disposal. GACs have been used for many years to remove volatile organic compounds such as chlorinated solvents, aromatic hydrocarbons, etc., but also bioactive molecules such as antibiotics or drugs with similar chemical structure. After a period of operation, when these carbons reach their saturation point they cease to perform their function and must be removed from service; however, they still have properties that could be useful if properly reactivated.
Thermal method for depleted coal reactivation.
The thermal reactivation method is one of the most widely used methods for coal generation in the industry and is the one we use. During the process of coal regeneration after treating water treatment for organics, it is generally divided into three stages: drying, high temperature carbonization and activation according to the change of organic matter when heated to different temperatures. In the drying stage, volatile components are removed from the activated carbon. In the high-temperaturecarbonization stage, some of the organic matter adsorbed on the activated carbon is carbonized, vaporized and desorbed, and some of the organic matter is decomposed to produce small-molecule hydrocarbons and desorbed, while the inorganic components (such as salts) remain in the pores of the activated carbon. At this stage, the temperature will reach 800-900 °C. To avoid oxidation of the activated carbon, the process is usually carried out under vacuum or in a controlled atmosphere. In the next activation stage, oxygen and water vapor are introduced into the rotary kiln to clean the micropores of the activated carbon and restore its adsorption performance, which is the key to the whole regeneration process. The thermal regeneration method has the characteristics of high regeneration efficiency.
Results:
This section should contain the results of the laboratory analysis.
Results and decision
The results of the study may show that spent or exhausted granular activated carbon could not be reactivated and reused for its intended purpose for the following reasons:
- Reactivation methods were ineffective in reactivating the coal.
- Its cost to reactivate due to the size of the lot, it would not be cost effective for industrial use.
- The use of activated carbon and the retained compounds are toxic or dangerous for a high temperature reactivation process.
- The hardness of the charcoal is less than the recommended hardness for reactivation and the charcoal can break easily.
Conclusions
This analysis can conclude that it is possible to reactivate and utilize used granular coals. It is recommended that future analyses be conducted to determine the feasibility of using granular coals with previous reactivations, and to determine if the coal will be feasible for reclamation. The results of this study indicate that reactivation using the five different methodologies is feasible. The results of the XRF analysis showed that reactivation can be successfully performed and produce activated carbon with a BET surface area greater than 200 m2/g, which meets the ASTM D6473 standard for activated carbon in granular form. It can also be found that the amount of activation energy required to achieve more than 200 m2/g is within 5% or less of what is required by industry standards. In addition, future studies should investigate methods to improve the quality of spent carbons produced by this process in order to obtain acceptable quality, or it can be used as an alternative fuel source.
Recycling and sustainability
The results of a coal reactivation allow the reuse of these materials and reduce impacts on landfills, which is an important aspect of sustainability.