Waste Tea as a Potential Source of Caffeine Recovery and Green Adsorbent for Dye Removal: A Review

Tea stands second, after water, as one of the most common and widely consumed beverages worldwide such as soft drinks, alcohol, and chocolate. Nevertheless, a lot of tea residue is discarded as waste after processing resulting in waste of resources and degradation of the environment. Substantial scientific work has been undertaken focusing on separating and identifying the active ingredients in tea waste. Tea waste contains protein, cellulose, polyphenol, and lignin. Globally generation of tea waste per year is approximately 5 million tons. Usually, this waste is burnt off or disposed of in landfills. Caffeine (C8H10N4O2) has been identified as one of the most significant active ingredients in tea waste. Caffeine content in tea waste is 2-3%. Caffeine enhances sports performance by promoting relaxation, lowering physical exhaustion and smooth muscle. Dye effluents present a significant threat to the environment when disposed of untreated due to their complicated molecular structures. The most explored techniques for eliminating dyes from wastewater are chemical precipitation, adsorption, flocculation, and biological oxidation. Finding affordable, environmentally acceptable adsorbents has been one of the major areas for research in the present era. Tea residue can serve as a highly effective adsorbent because of its large surface area and porous framework. It can serve as a potential bio-adsorbent for wastewater treatment applications specifically to remove various types of dyes, including methylene blue, acid blue as well as heavy metals. One important component of the adsorption system is the adsorbent. The yield of the adsorbents when removing different contaminants from wastewater is dependent on a number of factors, such as the medium's pH and temperature, the dose of the adsorbent utilized, and the permitted contact duration.