Context: Indian researchers have devised a method to produce activated carbon from coconut husks which are a major agricultural residue in Kerala, suitable for supercapacitor fabrication.
Activated Carbon Explained:
- Activated carbon or activated charcoal is a form of carbon processed to have small, low-volume pores that increase its surface area for adsorption or chemical reactions.
- It is produced from carbonaceous materials such as wood, coal, or coconut shells, primarily through a two-step process involving carbonisation and activation.
- Carbonisation is the process of converting raw carbonaceous materials into a charred material by heating them (temperatures between 400-700°C) in the absence of air in an inert atmosphere (often nitrogen) to prevent combustion. This process removes volatile components (such as tar, methane, and other gases) and leaves behind a solid char (carbon-rich material).
- Activation enhances the porous structure of the char, increasing its surface area and making it highly effective for adsorption. Here, the char is exposed to oxidising gases such as steam or carbon dioxide at high temperatures (600-1200°C), which creates a network of pores.
Properties:
- High Surface Area allows for a high capacity of adsorption.
- Porosity: Numerous micro and macropores enhance its ability to trap and hold molecules from gases and liquids. Hence, it can adsorb a wide variety of substances, including organic compounds, chlorine, and some heavy metals, due to its high porosity and surface area.
Note:
- Adsorption is a surface phenomenon where molecules, atoms, or ions from a gas, liquid, or dissolved solid adhere to the surface of a solid or liquid material. This process is different from absorption.
- In absorption, the absorbate (the substance being absorbed) penetrates into the interior of the absorbent material.
Potential Uses:
- Water Purification: Activated carbon is widely used in water treatment plants to remove organic compounds, chlorine, and other contaminants from drinking water.
- Air Purification: It is used in air filters to capture volatile organic compounds (VOCs), odours, and pollutants in both industrial and residential settings.
- Chemical Purification: Activated carbon is used to purify chemicals and solvents in the pharmaceutical and chemical industries.
- Food and Beverage Industry: It is used for decolourisation and purification in the production of food and beverages, such as sugar refining and wine purification.
- Medical Uses: Activated carbon is used in medical applications for treating poisonings and overdoses by adsorbing toxins in the gastrointestinal tract.
- Gold Recovery: In the mining industry, activated carbon is used to extract gold from cyanide leach solutions.
- Energy storage: Can be used to manufacture sustainable and efficient green solutions for energy storage like supercapacitors.
Capacitors:
- A capacitor is an electronic device that stores electrical energy by accumulating electric charges on two closely placed conductive plates (electrodes) that are insulated from each other.
- Supercapacitors with significantly higher capacitance and energy storage capacity than conventional capacitors are vital in the quest for sustainable energy storage solutions. But, the search for an ideal supercapacitor electrode material has been a challenge.
- Ideal supercapacitor should have:
- High Surface Area: To maximise the amount of charge stored.
- Good Electrical Conductivity: To ensure efficient charge transfer.
- Chemical Stability: To maintain performance over many charge and discharge cycles.
- Mechanical Stability: To withstand physical stress during operation.
- Cost-Effectiveness: To be commercially viable for large-scale production.
- Environmental Friendliness: To minimise environmental impact.
- Ideal supercapacitor should have:
Latest development:
- The prototype supercapacitors made of the coconut husk-derived activated carbon have been found to be four-times more efficient than the existing supercapacitors.
- Further, the supercapacitors are sustainable and efficient green solutions for energy storage owing to the availability, low cost, and eco-friendly nature of coconut biowaste or biomass.