Search Results (2)

Green tea waste (GTW) is a naturally abundant material, and it has not been widely reused into more valuable materials. The composition of GTW was identified using NMR for carbohydrate composition, an element analyzer for protein content, acetone and hot water extraction for evaluating extractives, and Klason lignin for lignin content. GTW can be converted into nanoparticles by carboxymethylation as pretreatment of the degree of substitutions (DS) and high-pressure homogenizer for nanoparticle making. GTW was prepared using various DS 0 until DS 0.4. The results showed that GTW DS has a more than −30 mV zeta potential, suitable for stable nanoemulsion formulations. The particle size of GTW DS decreases with increasing carboxyl content in the hydrogel, which has a width and length from GTW DS 0.3 to DS 0.4. As a humectant, the water retention value (WRV) of GTW with various DS was increased; DS 0.3 is the best. DS 0.4 has the highest viscosity, storage, and loss modulus as rheology modifiers. Full article

Adsorptive removal of methylene blue (MB) from contaminated water samples was achieved using green tea waste (GTW). Adsorption of MB onto raw (RGTW) and thermally treated waste (TTGTW250–TTGTW500) was explored. The performance of the tested adsorbents was assessed in terms of percentage removal of MB (%R) and adsorption capacity (qe, mg/g). A full factorial design (FFD) was employed to optimize the adsorption of MB onto both RGTW and TTGTW500. Four factors were studied: pH, adsorbent dose (AD), dye concentration (DC), and contact time (CT). Value for %R of 96.58% and 98.07% were obtained using RGTW and TTGTW500, respectively. FT-IR and Raman analyses were used to study the surfaces of the prepared adsorbents, and the IR spectrum showed the existence of a variety of functionalities on the surfaces of both the RGTW and thermally treated samples. BET analysis showed the presence of mesopores and macropores in the case of RGTW and micropores in the case of thermally processed adsorbents. Equilibrium studies indicated that the Freundlich isotherm best described the adsorption of MB onto both adsorbents. The maximum adsorption capacity (q_max) was found to be 68.28 and 69.01 mg/g for RGTW and TTGTW500, respectively, implying the superior capacity of TTGTW500 in removing MB. Adsorption of MB was found to proceed via chemisorption (RGTW) and physisorption (TTGTW500), as indicated by the Dubinin–Radushkevich (D-R) isotherm. A pseudo-second order (PSO) model best demonstrated the kinetics of the MB adsorption onto both adsorbents. Full article