title: Equilibrium and dynamic study on hexavalent chromium adsorption onto activated carbon.
abstract: In this work, the results of equilibrium and dynamic adsorption tests of hexavalent chromium, Cr (VI), on activated carbon are presented. Adsorption isotherms were determined at different levels of pH and temperature. Dynamic tests were carried out in terms of breakthrough curves of lab-scale fixed bed column at different pH, inlet concentration and flow rate. Both the adsorption isotherms and the breakthrough curves showed non-linear and unconventional trends. The experimental results revealed that chromium speciation played a key role in the adsorption process, also for the occurrence of Cr(VI)-to-Cr(III) reduction reactions. Equilibrium tests were interpreted in light of a multi-component Langmuir model supported by ion speciation analysis. For the interpretation of the adsorption dynamic tests, a mass transfer model was proposed. Dynamic tests at pH 11 were well described considering the external mass transfer as the rate controlling step. Differently, for dynamic tests at pH 6 the same model provided a satisfying description of the experimental breakthrough curves only until a sorbent coverage around 1.6mgg(-1). Above this level, a marked reduction of the breakthrough curve slope was observed in response to a transition to an inter-particle adsorption mechanism.
authors.affiliation: Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli "Federico II", Piazzale Tecchio 80, 80125, Napoli, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Di Natale
authors.affiliation: Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli "Federico II", Piazzale Tecchio 80, 80125, Napoli, Italy. Electronic address: aleserto@unina.it.
authors.forename: A
authors.initials: A
authors.lastname: Erto
authors.affiliation: Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli "Federico II", Piazzale Tecchio 80, 80125, Napoli, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Lancia
authors.affiliation: Dipartimento di Ingegneria Civile, Design, Edilizia e Ambiente, Seconda Università di Napoli, Via Roma 29, 81031, Aversa (CE), Italy.
authors.forename: D
authors.initials: D
authors.lastname: Musmarra
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D002244:Carbon
keywords: Adsorption; Equilibrium; Hexavalent chromium; Kinetics; Langmuir model; Water