Flotation characterization of PET and PVC in the presence of different plasticizers Ali Güney, Cihan Özdilek, M. Olgaç Kangal, Fırat Burat ⇑ Istanbul Technical University, Faculty of Mines, Mineral Processing Engineering Department, 34469, Maslak, Istanbul, Turkey article info Article history: Received 1 April 2015 Received in revised form 30 June 2015 Accepted 15 July 2015 Available online 15 July 2015 Keywords: Plastics Lignin alkali Diethylene glycol dibenzoate Selective froth flotation abstract Plastic is one of the most widely used materials in our daily life and industry. Recycling is an important activity in the minimization of waste that results from human activities. Depending on plastics surface characteristics, they can be separated from each other by flotation method which is useful mineral processing technique with its low cost and simplicity. To succeed in a separation of mixed polymers based on polymer type using selective flotation, it is necessary to render one surface more hydrophilic while the others are still in a hydrophobic state. The separation could be achieved with the help of appro- priate plasticizer. In this paper, the characteristics of plastics particles and flotation behaviors of polyethylene terephtha- late (PET) and polyvinyl chloride (PVC) were studied. The contact angle, liquid surface tension, zeta potential measurements and FITR analysis were performed in order to investigate the effect of plasticizer reagents and the success of froth flotation at plastic recycling. It was observed that contact angle values of PVC were smaller than PET in the presence of lignin alkali (LA) and diethylene glycol dibenzoate (DIB). Both plasticizer render PVC more hydrophilic and cause higher wettability. Therefore, PVC remains in the floatation cell while air bubbles are attaching to PET. At the end of the selective flotation experiments, PET was separated from the mixture of PET and PVC with 97% content and more than 99% recovery when using 25 g/t LA as a plasticizer at pH 8. To succeed in a separation of PET from PVC by selective flotation, 250 g/t DIB was added into the solution at pH 5 and PET particles were separated from the mixture at 90% content and 95% recovery. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Plastics are used in a wide variety of products and have dis- placed other materials, such as wood, metal, and glass. It can be formed into polyesters for use in fabrics and textiles, polyvinyli- dene chloride for food packaging, and polycarbonates for eye- glasses and compact disks, among thousands of other uses. The production of plastic requires four basic steps: the acquirement of raw material, synthesizing a basic polymer, compounding the polymer into a usable fraction, and lastly, molding or shaping the plastic. In 2013, global production of plastics reached nearly 300 million metric tons, with 57 million metric tons in Europe alone (Fig. 1). China is one of the largest producers of plastics in the world, accommodating almost 25 percent of the global share [1]. In recycling of plastics material, it is often necessary to separate mixtures of plastics into individual plastics in order to get a useful recycling plastic product because some plastics are not compatible during re-melting [2]. The recycling procedure for plastic bottles normally involves three basic steps: the collection and sorting of plastic bottles, re-processing into reusable flakes or pellets, and development of market for recycled plastics [3,4]. A number of promising technologies for the separation of mixed thermoplastics are under investigation and include air classifica- tion, hydrocycloning, flotation/sedimentation, depolymeriza tion/purification/repolymerization, selective dissolution, sorting based on infrared analysis or laser scanning of polymers, and incor- poration of chemical markers into different polymers [5]. The idea to apply flotation to separate plastics was a logical step as ore flotation research has demonstrated that the surface proper- ties of different materials can be altered selectively by surfactant adsorption [6]. The use of froth flotation for plastic separation is particularly challenging because of the similarity in the surface properties of the materials. All plastics have naturally hydrophobic surfaces and will readily float with the aid of air bubbles. The selected treatment system must render at least one plastic hydrophilic, resulting in no air attachment. The wettability of http://dx.doi.org/10.1016/j.seppur.2015.07.027 1383-5866/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: buratf@itu.edu.tr (F. Burat). Separation and Purification Technology 151 (2015) 47–56 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur