The separation of one or a group of plastics from a plastics mix by flotation technique is an essential topic in plastic waste management. Basis of the technique refers to the selective adsorption of a depressant on the surface of the plastic. Consequently, the surface energy of plastic alters. Adsorption of the lignosulfonic acid sodium salt (SL) on the surface of the selected available plastics in the waste stream was studied at different SL concentrations and operative temperatures. Studied plastics were Polyvinylchloride (PVC), acrylonitrile-butadiene-styrene polymer (ABS), polystyrene (PS), polypropylene (PP), polyoxymethylene (POM), and polycarbonate PC. Based on the measured equilibrium adsorption capacities (Q_e\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'s), the SL adsorbed on the selected plastics surfaces with different amounts. Increasing the temperature had a positive effect on the above-mentioned parameter. Suitable conformity was observed between the experimental results with predicted values by the traditional adsorption isotherms, Freundlich and Langmuir. However, for the most studied plastics, the Freundlich model was more suitable than Langmuir. Measured thermodynamic parameters showed a spontaneous adsorption process along with endothermic (except of PC) reactions. The complete separation of PC from a plastics mix in all SL concentrations and temperatures was observed during the flotation process.

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