Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece A novel sulfonated waste polystyrene / iron oxide nanoparticles composite: Green synthesis, characterization and applications Cristina A. De León-Condés a , Gabriela Roa-Morales b , Gonzalo Martínez-Barrera c, ⁎ , Patricia Balderas-Hernández b , Carmina Menchaca-Campos d , Fernando Ureña-Núñez e a Posgrado en Materiales, Facultad de Química, Universidad Autónoma del Estado de México, Paseo Colon esquina Paseo Tollocan S/N, 50180 Toluca, Mexico b Centro Conjunto de Investigación en Química Sustentable, Universidad Autónoma del Estado de México, Universidad Nacional Autónoma de México (UAEM-UNAM), Carretera Toluca-Atlacomulco, km 14.5, Unidad El Rosedal, C.P. 50200, Mexico c Laboratorio de Investigación y Desarrollo de Materiales Avanzados (LIDMA), Facultad de Química, Universidad Autónoma del Estado de México, Km.12 de la carretera Toluca-Atlacomulco, San Cayetano 50200, Mexico d Centro de Investigación en Ingeniería y Ciencias Aplicadas (CIICAp), Universidad Autónoma del Estado de Morelos (UAEM), Av. Universidad 1001, Col. Chamilpa, C.P. 62209 Cuernavaca Morelos, Mexico e Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, 52750, La Marquesa Ocoyoacac, Mexico ARTICLE INFO Keywords: Polystyrene waste Iron oxides nanoparticles Composites Sulfonation Green synthesis Polyphenols ABSTRACT A composite of sulfonated waste expanded polystyrene (SWPS) and iron(II) oxide nanoparticles (FeO-NPs) was created through sulfonation of the polymer followed by synthesis of the nanoparticles by extracts of green tea leaves (Camellia sinensis). The SWPS was characterized by Fourier Transform Infrared spectroscopy (FT-IR), while the degree of sulfonation (DS) was determined through elemental analysis. The bioreduction of the na- noparticles was monitored in the solutions by UV–vis spectroscopy. The FeO-NPs + SWPS composite was characterized using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), trans- mission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Moreover, FeO-NPs + SWPS composites were used to degrade the organic pollutant indigo carmine dye. The results show the degree of sulfonation of the composite is 23.5% and its ion exchange capacity is 1.2 meq g -1 . TEM analysis revealed that the FeO-NPs are predominantly quasi-spherical with average diameters of 25 nm. The FeO-NPs + SWPS com- posite achieved 86.7% destruction of indigo carmine dye in a 100 mg/L solution with 60 min of contact time at an initial pH of 3.2 and a 6 g/L catalyst dose. 1. Introduction Expanded polystyrene (EPS) is a common material for cups and packaging. It is lightweight with a content of 5% of polystyrene and 95% of air [1], which can be chemically modified through various processses like sulfonation [1–4]. Sulfonation of polymers generally increases hydrophilicity, proton conductivity and water-solubility [4–6]. Sulfonated waste polystyrene has a wide variety of applications in chromatography, fuel cells, wastewater treatment, remediation of contaminated soils [1,3–5], industrial water treatment [6], as well as in modified mortars [7]. Porous materials (tuffite, pumice, silica and pillared clay), poly- mers, organic compounds and nanostructured carbon, have been widely used as mechanical supports to enhance dispersibility of iron nano- particles. Nanoparticles synthesized on a support substrate exhibit a narrower size distribution as well as higher activity compared to non- supported ones [8–10]. Materials such as zeolites have been used to remove contaminants in water, but they show some disadvantages, for example limited diffusion. Ion exchange resins have been made from sulfonated polystyrene and have been proved to be good catalysts [11]. The use of iron to remove organic and inorganic pollutants has gained increasing interest [12]. Moreover, iron(II) oxide nanoparticles (FeO-NPs) have drawn significant attention for wastewater treatments, especially for the removal of pesticides, dyes and halogenated com- pounds present in wastewater [13]. One of the most common methods to obtain the zero valent iron nanoparticles is based on the reduction of Fe 2+ or Fe 3+ by using so- dium borohydride or ethylene glycol. The disadvantages of the che- mical methods used in the reduction of nanoparticles are the compli- cated management of reducing agents or precursors, as well as nanoparticle agglomeration due to van der Waals interactions [14]. Green tea leaves are rich in polyphenols such as flavonoids and their https://doi.org/10.1016/j.jece.2018.102841 Received 15 July 2018; Received in revised form 5 December 2018; Accepted 15 December 2018 ⁎ Corresponding author. E-mail address: gonzomartinez02@yahoo.com.mx (G. Martínez-Barrera). Journal of Environmental Chemical Engineering 7 (2019) 102841 Available online 21 December 2018 2213-3437/ © 2018 Elsevier Ltd. All rights reserved. T