A mixture of traditional virgin (unused) plastics ordinarily available in municipal wastes, polyvinylchloride (PVC), polystyrene (PS) and polyethylene terephthalate (PET) was treated with several chemical agents, i.e., polyvinyl alcohol (PVA), polyethylene glycol (PEG), methyl cellulose (MC), tannic acid (TA) and methyl isobutyl carbinol (MIBC), individually or combine with each other. The effects of various parameters on floatability of used plastics, namely, chemical agent type and concentration, conditioning temperature and time and liquid media pH, were studied and the results were discussed. It revealed that in most experiments, the PET sustained the least flotation change for studied chemical agents and was sunk at the bottom of the flotation tank. The TA was useful on PVC flotation through surface adsorption and changing the PVC surface hydrophobic behavior in different ways depending on the TA concentration. As a general rule and with the PET exception, increasing temperature improved floatability of all studied plastics for used chemical agents. The raising the pH of the liquid media changed the floatability of studied plastics in different ways depending on the pH value and the used chemical agent. In most cases, the increasing conditioning time was beneficial to plastic flotation up to 15 minutes. As an essential conclusion, the PVC and PS could be separated from PET in their mixture by using TA-PEG with 0.2-0.8 ratio and TA-PEG with equal ratio plus 2ml/L MIBC in two stages completely. The comparison of the results with other studies showed the shape and size of used plastics are critical factors on separation of studied plastics by flotation technique.

Keywords