Study on the adsorption mechanism of the sodium lignosulphonate on the surface of the selected plastics as a potential solution for plastics waste management

Separating different components of a plastic mixture is crucial in its recycling. Among the different separation techniques, flotation was selected as a cheap, non-toxic, and efficient process. Basis of the technique refers to the selective adsorption of a depressant on the plastics surface which cause the alteration in the surface energy of the plastic. Adsorption of the lignosulfonic acid sodium salt (SL) on the surface of the selected available plastics in the waste stream was studied. Plastics used in this study were Polyvinylchloride (PVC), acrylonitrile-butadiene-styrene polymer (ABS), polystyrene (PS), polypropylene (PP), polyoxymethylene (POM), and polycarbonate PC. It results showed that SL adsorbed on the surface of the selected plastics considerably. It was evidenced by the measured equilibrium adsorption capacities ( [Formula: see text] ) of the SL and also, the SEM and AFM images. SL adsorbed on the plastic surface in the sequence of [Formula: see text]. Also, the parameters of the Freundlich and Langmuir adsorption models were derived. Experimental data fit with the mentioned models appropriately. However, for the most studied plastics, the Freundlich model was more suitable. As important conclusion, PP separated from plastics mix using the flotation separation technique with the aid of SL as a depressant.