title: Separation of plastics: The importance of kinetics knowledge in the evaluation of froth flotation.
abstract: Froth flotation is a promising technique to separate polymers of similar density. The present paper shows the need for performing kinetic tests to evaluate and optimize the process. In the experimental study, batch flotation tests were performed on samples of ABS and PS. The floated product was collected at increasing flotation time. Two variables were selected for modification: the concentration of the depressor (tannic acid) and airflow rate. The former is associated with the chemistry of the process and the latter with the transport of particles. It was shown that, like mineral flotation, plastics flotation can be adequately assumed as a first order rate process. The results of the kinetic tests showed that the kinetic parameters change with the operating conditions. When the depressing action is weak and the airflow rate is low, the kinetic is fast. Otherwise, the kinetic is slow and a variable percentage of the plastics never floats. Concomitantly, the time at which the maximum difference in the recovery of the plastics in the floated product is attained changes with the operating conditions. The prediction of flotation results, process evaluation and comparisons should be done considering the process kinetics.
authors.affiliation: Department of Chemical Engineering Material & Environment, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Censori
authors.affiliation: Department of Chemical Engineering Material & Environment, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy.
authors.forename: Floriana
authors.initials: F
authors.lastname: La Marca
authors.affiliation: CERENA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Electronic address: teresa.carvalho@ist.utl.pt.
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Carvalho
mesh_terms: D007700:Kinetics; D010969:Plastics; D011108:Polymers; D059027:Recycling / Q000379:methods* / Q000706:statistics & numerical data; D012037:Refuse Disposal / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D010969:Plastics; D011108:Polymers
keywords: ABS; Flotation kinetics; Froth flotation; PS; Plastics separation; Waste plastics