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

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RESEARCH ARTICLE-CHEMICAL ENGINEERING

Tea Residue-Based Activated Carbon: Preparation, Characterization and Adsorption Performance of o-Cresol Jun Tao1 · Xuexiang Fu1 · Chengchun Du1 · Dengfeng Zhang1 Received: 7 June 2020 / Accepted: 17 September 2020 © King Fahd University of Petroleum & Minerals 2020

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. Keywords Tea residue · Activated carbon · o-cresol · Adsorption · π-π dispersion

1 Introduction Phenol-containing wastewater is mainly discharged from a wide variety of industry sectors like coke making, pharmacy and synthetic fibers [1, 2]. As a typical phenolic compound, cresols are often used as pharmaceutical/chemical intermediate, solvent, disinfectant and reagent for producing resin, paint and textile [3]. Thus, the discharge of cresol-containing wastewater is huge. According to the classification raised by United States Environmental Protection Agency (USEPA), the cresols are persistent, priority, toxic chemicals and the study of the quantitative structure–activity relationship (QSAR) indicates that cresols can cause chronic

B 1

Dengfeng Zhang [email protected] Faculty of Chemical Engineering, Kunming University of Science and Technology, Kunming 650500, People’s Republic of China

effects at 12 μg L−1 . The toxicity test shows that the LC50 of cresols to Salmonid fish, the most sensitive environmen

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