Characteristics of 21 Types of Tea Waste for Adsorbance of Ionic Dyes from Aqueous Solutions

Abstract

In this study, 21 tea types (six black, four green, three Oolong, two herb, and five medicinal) were used to remove ionic dye from wastewater, as they could be potential adsorbents for several ionic dyes without purification or activated treatment. The majority of the 21 teas could adsorb cationic (MB) and anionic (ORII) dyes, with greater suitability for cationic dyes, as well as BB54 and BR46. Black dye (KBla), a mixture of several dyes, was adsorbed to a high degree. The tea waste treatment resulted in chromaticity reduction of the dye solution and turbidity changes. Dye adsorption was greater at higher temperatures than lower ones, although the effect of temperature was not strong. The adsorptions fit the pseudo-second-order-model; therefore, they involved chemical adsorption. The tea waste had great potential for the adsorption of several types of dyes without purification or activated treatment, although the mechanisms are yet to be determined. Therefore, the physical properties and structural components of each tea type should be analyzed by comparing common or different features of tea types. Taken together, many types of tea that are consumed worldwide can be used for efficient adsorption of ionic dyes by application of the tea waste.