Preparation and characterisation of activated carbon from waste tea by physical activation using steam

Abstract

In this study, the feasibility of preparing activated carbon from waste tea by physical activation using steam was investigated. The effects of activation temperature on yield and pore properties of the prepared activated carbon were studied. The yield decreased with increased activation temperature owing to the decomposition of cellulose and hemicellulose. The specific surface area and pore volume of the activated carbon were estimated using the Brunauer-Emmett-Teller method, Langmuir equation, and t-plot method. The specific surface area and micropore volume increased with increases in activation temperature, as additional volatile materials were released. The specific surface area significantly decreased at first but slightly increased with increasing activation time. The maximum specific surface area reached 995 m/g at an activation temperature of 800 °C with a water flow rate of 0.075 g/min and a constant hold time of 0.5 hr. According to the nitrogen adsorption isotherms, micropores mainly developed when the activation temperature was below 800 °C, and both micropores and mesopores developed when it was above 800 °C. The results showed that activation temperature significantly affected micropore and mesopore volumes, as well as the specific surface area of the activated carbon. Overall, waste tea was found to be an attractive raw material for producing low-cost activated carbon. Implications: Every year, a large amount of waste tea is generated after extraction. The high carbon content of waste tea showed that it can be used as raw material to produce activated carbon. This study investigated the feasibility of preparing activated carbon from waste tea by physical activation using steam. Temperature and time were found to have clear effects on pore properties. Our proposed method and raw material are more environmentally friendly and involve low cost. Furthermore, this offers a potential solution to the problems of waste tea disposal and low-cost activated carbon production.

Potentials of activated carbon produced from biomass materials for sequestration of dyes, heavy metals, and crude oil components from aqueous environment

“…The carbon-rich raw materials for producing activated carbon are cleaned, washed, and dried before physical or chemical activation is applied. Physical activation also called thermal activation occurs in two steps (Jiazhen et al 2018). It involves carbonization at the temperature range of 500-600 °C of a carbon-rich product with the activation of the charcoal between 800 and 1100 °C in the presence of oxidizing agents such as CO 2 , steam, air, or their mixtures.…”

Comparative Study of Toluene and Hexane Adsorption on Activated Carbons From Gas and Liquid Phase. Enthalpy and Isotherms

“…Later, the surface area was determined by means of the Brunauer-Emmett-Teller (BET) model, the total pore volume was determined at P/P • 0.99, the micropore volume by the Dubinin-Radushkevich equation (DR), as well as the mesopore volume that was obtained by the difference between the total volume and the micropore, whose values for CS were, respectively: 851 m 2 g −1 , 0.39 cm 3 g −1 , 0.34 cm 3 g −1 , y 0.05 cm 3 g −1 , while for CST they had a slight increase: 934 m 2 g −1 , 0.41 cm 3 g −1 , 0.38 cm 3 g −1 , y 0.03 cm 3 g −1 . This could be generated because selective removal of functional groups could give rise to access to pores that were blocked and widening of porous structures (Nguyen and Bhatia, 2012;Zhou et al, 2018). This removal was related to the thermal stability of the surface groups, since at temperatures higher than 673 K the carboxylic groups are removed, at 923 K the lactonic groups and 973 K the phenolics (Figueiredo et al, 1999), which are the groups that can be evaluated by Boehm titrations and whose results are shown in Figure 5 where a decrease in the content of these functional groups was indeed evidenced, which was corroborated by the pore size distribution (PSD) presented in Figure 3, since the PSD showed higher pore volumes for CST than for CS.…”

Sustainable Battery Materials from Biomass

“…This process however does not lead to sufficiently small pores, so further porogens are needed in addition. Finally, physical activation using water vapor and CO 2 may be used to introduce porous structures in biomass‐derived carbon materials …”