Understanding of mechanisms of organohalogens removal onto mesoporous granular activated carbon with acid-base properties

• Published in: Microporous and mesoporous materials 2021-04, Vol.317, p.110974, Article 110974
• Main Authors: Yankovych, Halyna, Melnyk, Inna, Václavíková, Miroslava
• Format: Article
• Language: English
• Subjects: 4-Halogenphenols; Adsorption mechanism; Carbon; Esterification; H-bonding
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2021.110974

Adsorptive removal of 4-chlorophenol, 4-bromophenol and 4-iodophenol from aqueous solutions by commercial granular activated carbon (GAC) was studied. The main important characteristics of GAC were investigated: SBET 1010 m2/g, pHPZC 5.2, total acidity 0.3 mmol/g and total basicity 0.6 mmol/g. The favourable adsorption conditions were: pH 5–10, agitation time 240 min and adsorbent dosage 2 g/L. The maximum adsorption capacity of 4-halogenphenols was determined from adsorption isotherms: 168.5 mg/g for 4-chlorophenol, 151.7 mg/g for 4-bromophenol and 61.5 mg/g for 4-iodophenol. Experimental kinetic curves followed pseudo-second order for all compounds investigated. It was found that the Langmuir isotherm model is the most appropriate to describe adsorption of all organohalogens on the GAC surface. Desorption studies determined that the best desorbents were concentrated acetic acid, ethanol and 1 M potassium hydroxide. Elucidation of adsorption mechanism showed that the elimination of 4-halogenphenols was caused by film diffusion, H-bonding and esterification reactions. The contribution of each mechanism in total adsorption was also estimated. It was shown that halogen atom had significant influence on adsorption mechanism. The present work offers a novel insight of the adsorption mechanism between GAC and other phenolic compounds. [Display omitted] •Mesoporous amphoteric GAC shows high adsorption capacity towards to 4-HPhs.•Qmax was 168.5 mg g−1 for 4-CPh, 151.7 mg g−1 for 4-BPh and 61.5 mg g−1 for 4-IPh.•Experimental data were fitted with Langmuir as well as PSO kinetic models.•H-bonding and esterification reaction were the main chemisorption mechanisms.•The nature of halogen atom has significant influence on adsorption mechanisms.