Characteristics of ball-milled PET plastic char for adsorption of different types of aromatic organic pollutants

Abstract Ball-milled plastic char (BMPC) was manufactured by ball-milling of native plastic char (PC) that was synthesized via slow pyrolysis of PET water bottle waste, by which the adsorption characteristics of aqueous phenanthrene, phenol and 2,4,6-trichlorophenol, and its possible mechanisms were investigated. The special surface area of BMPCs increased obviously as the pyrolysis temperature increased, forming large functional groups compared to PCs. Boehm titration showed that total acidic groups of BMPCs decreased significantly with the increase of pyrolysis temperature. The sorption kinetics of three adsorbates was adequately simulated by Pseudo second-order model (R2＞0.99). Langmuir model fitted well the adsorption isotherms of phenanthrene and phenol, while Freundlich model simulated the adsorption isotherm of 2,4,6-trichlorophenol. The adsorption amount of phenanthrene, phenol and 2,4,6-trichlorophenol increased significantly as the pyrolysis temperature increased. The maximum BMPCs adsorption amount reached 21.9mg/g (for phenanthrene), 106mg/g (for phenol) and 303mg/g (for 2,4,6-trichlorophenol) at 25℃ in aqueous solution. FTIR analysis suggested that surface sorption based π-π interaction was dominant mechanism of phenanthrene adsorption, meanwhile, H-bonding between O-containing groups on BMPCs and hydroxyl groups of absorbates was responsible for phenol and 2,4,6-TCP removal. This paper shows that BMPCs can be used as adsorbent for treating aromatic compounds in aqueous environment, and has an economic worth of application.