title: Heterogeneous nano-Fe/Ca/CaO catalytic ozonation for selective surface hydrophilization of plastics containing brominated and chlorinated flame retardants (B/CFRs): separation from automobile shredder residue by froth flotation.
abstract: One method of weakening the inherently hydrophobic surface of plastics relevant to flotation separation is heterogeneous nano-Fe/Ca/CaO catalytic ozonation. Nano-Fe/Ca/CaO-catalyzed ozonation for 15 min efficiently decreases the surface hydrophobicity of brominated and chlorinated flame retardant (B/CFR)-containing plastics (such as acrylonitrile-butadienestyrene (ABS), high-impact polystyrene (HIPS), and polyvinyl chloride (PVC)) in automobile shredder residue (ASR) to such an extent that their flotation ability is entirely depressed. Such a hydrophilization treatment also stimulates the ABS, HIPS, and PVC surface roughness, wetting of the surface, and the thermodynamic equilibrium conditions at the surface and ultimately changes surface polarity. SEM-EDS, AFM, and XPS analyses of the PVC and ABS surfaces demonstrated a marked decrease in [Cl/Br] and a significant increase in the number of hydrophilic groups, such as C-O, C=O, and (C=O)-O. Under froth flotation conditions at 50 rpm, about 99.5 % of ABS and 99.5 % of HIPS in ASR samples settled out, resulting in a purity of 98 and 98.5 % for ABS and HIPS in ASR samples, respectively. Furthermore, at 150 rpm, we also obtained 100 % PVC separation in the settled fraction, with 98 % purity in ASR. Total recovery of non-B/CFR-containing plastics reached nearly 100 % in the floating fraction. The amount of nano-Fe/Ca/CaO reagent employed during ozonation is very small, and additional removal of surface contaminants from the recycled ASR plastic surfaces by ozonation makes the developed process simpler, greener, and more effective.
authors.affiliation: Department of Civil and Environmental Engineering, University of Ulsan, Daehak-ro 93, Nam-gu, Ulsan, 680-749, Republic of Korea. srireddys@ulsan.ac.kr.
authors.forename: Srinivasa Reddy
authors.initials: SR
authors.lastname: Mallampati
authors.affiliation: Department of Civil and Environmental Engineering, University of Ulsan, Daehak-ro 93, Nam-gu, Ulsan, 680-749, Republic of Korea.
authors.forename: Byoung Ho
authors.initials: BH
authors.lastname: Lee
authors.affiliation: Department of Environmental Sciences, Prefectural University of Hiroshima, 562 Nanatsuka-Cho, Shobara City, Hiroshima, 727-0023, Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Mitoma
authors.affiliation: Department of Organic Chemistry, Politehnica University of Bucharest, 060042, Bucharest, Romania. c_simion@chim.upb.ro.
authors.forename: Cristian
authors.initials: C
authors.lastname: Simion
mesh_terms: D001336:Automobiles; D002118:Calcium / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D002384:Catalysis; D005411:Flame Retardants / Q000032:analysis*; D054879:Halogenation; D057927:Hydrophobic and Hydrophilic Interactions; D007501:Iron / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D010969:Plastics / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D017610:Calcium Compounds; D005411:Flame Retardants; D010087:Oxides; D010969:Plastics; D010126:Ozone; C016538:lime; D007501:Iron; D002118:Calcium
keywords: Automobile shredder residue; B/CFR-containing plastics; Contact angle; Hydrophilization; Ozonation