Selective flotation technique for separation of PET and HDPE used in drinking water bottles

Plastics have become the widely used materials because of their advantages, such as cheapness, endurance, lightness, and hygiene. However, they occur as solid waste masses within a short time when used in package industry. This causes waste and soil pollution, because they do not decompose. Polyethylene terephthalate (PET) and high-density polyethylene (HDPE) are the most important varieties of plastics that are usually used in the manufacturing drinking water bottles. Depending on their surface characteristics, these plastics can be separated from each other by flotation method. But, all plastics are naturally hydrophobic. In order to employ flotation for the separation process, one of these plastics is made hydrophilic, while the other remains hydrophobic. Plasticizer reagents are used to change the plastics' surface character and make them hydrophilic. The aim of this investigation is to research selective flotation of used PET and HDPE by utilizing Triton XL-100N and Diethylene Glycol Dibenzoate-type plasticizers at optimum temperature, pH, and conditioning time. As a result of this investigation, PET-HDPE concentrates having about 100% purities were obtained with 100% recovery, when the mixture of PET-HDPE was conditioned for 30min with 40kglt NaOH at pH 10 and 1000glt Dietilen Glycol Dibenzoate at 50°C.