POLYMER WASTES’ FLOTATION SEPARATION RESEARCH RESULTS

Abstract

For separation of plastic wastes (polyamide (PA), acrylonitrile butadiene styrene (ABS) and polystyrene (PS), a flotation method is proposed. Using this method, the effect of concentration of surface-active substances (surfactants), which were used as polidocanol, sulphanole and a mixture of surfactants containing sodium laureth sulfate and diethanolamide, was studied. The research results analysis of the flotation separation of a mixture of crushed plastic wastes was carried out according to the calculated values of the extraction of a floated component ε and the purity of a concentrate β. It was noted that the maximum extraction of the floated component depends on the polymer and surfactant type. A mixture of surfactants at lower concentrations allows to achieve greater extraction of the floated component with less foaming ability. The research results on the extraction of polystyrene from the air flow rate at various concentrations of surfactants’ mixture show that the extraction has a maximum at a certain air flow rate. At low air flow rates, the working volume of liquid is not saturated enough with gas bubbles. If the optimal value of air flow rates is exceeded, many gas bubbles are formed that are not involved in the flotation process. The research results on the extraction of polystyrene from the aerated liquid layer height at various concentrations of surfactants’ mixture show that, at a low height of the aerated liquid layer, the probability of collision of a plastic particle with an air bubble is low and some potentially floated particles seek the bottom of an apparatus without having time to collide with an air bubble. When assessing the influence of liquid temperature on the flotation process, it was found that increasing the liquid temperature above 20°C leads to a sharp decrease in ABS and PS extraction. This is explained by the fact that the dependence of the surfactants’ foaming ability on the temperature is characterized by solubility curves and for most surfactants they have an extremum.