Waste tea leaves make dye-adsorbing polymer
doi:10.1038/nindia.2015.165 Published online 15 December 2015
By adding spent tea leaf powder to cellulose solution, researchers have synthesized a composite film that adsorbs harmful synthetic dyes such as methylene blue, making it potentially useful for removing such pollutants from wastewater1.
Naturally occurring cellulose could replace widely used non-biodegradable synthetic polymers. But cellulose is difficult to dissolve in traditional solvents. To overcome this drawback, the researchers prepared a powder from spent tea leaves and used it as a filler in a cellulose matrix. They did this by adding the powder to cellulose solutions to produce composite films.
The films showed higher tensile strengths than cellulose. The tensile strength increased with increasing tea leaf content, which the scientists say is due to uniformly dispersed tea leaf powder in the cellulose matrix. The films were also more thermally stable than cellulose because of the presence of phenolic and oxidized phenolic compounds in tea leaf powder.
The researchers found that the efficiency of the wet composite films to adsorb methylene blue dye increased with time up to 10 hours, and was six times higher than that of cellulose.
Since spent tea leaves are an abundantly available waste, they could be used as an inexpensive filler for biopolymers such as cellulose for removing synthetic dyes from wastewater, the researchers say.
1. Duan, J. et al. Effects of spent tea leaf powder on the properties and functions of cellulose green composite films. J. Environ. Chem. Eng. 4, 440–448 (2016)