Tea Residue-Based Activated Carbon: Preparation, Characterization and Adsorption Performance of o-Cresol

Abstract

In this study, the method regarding preparation of a tea residue-based activated carbon (AC) was provided. The physicochemical property and adsorption performance of the obtained AC were also investigated. The preparation of AC mainly includes the carbonization at 350 °C and activation by potassium hydroxide (KOH). The activation parameters including temperature, time and dosage of KOH are crucial to the physicochemical property of AC samples. According to the ANOVA analysis, the optimum activation conditions are determined as activation temperature of 900 °C, activation time of 60 min and mixture ratio of char and KOH of 3:2. The N2 adsorption/desorption and scanning electron microscopy (SEM) characterizations confirm that AC obtained at the above-mentioned optimum activation conditions, designated as AC7, possesses well-developed porosity. The Langmuir model well describes the adsorption equilibrium of o-cresol on sample AC7. The maximum o-cresol adsorption capacity obtained from the Langmuir model increases with the elevated temperature. The maximum adsorption capacity of o-cresol on sample AC7 could reach up to 476 mg g−1, which is higher than that of other reported AC samples. The adsorption kinetics of o-cresol on sample AC7 follows the pseudo-second-order model. The generated pseudo-second-order rate constant of o-cresol adsorption on sample AC7 rises with the operating temperature. The adsorption thermodynamics study shows that o-cresol adsorption on sample AC7 is spontaneous and endothermic. Apart from the physisorption, the chemisorption does exist between o-cresol and sample AC7. Particularly, the π–π dispersion interaction plays a dominant role during o-cresol adsorption on sample AC7.