Recycling of plastics is becoming more important nowadays due to the increasing amount of waste that is generated worldwide. Post-consumer plastics have a large volume and their harmful effects must be considered. From this perspective, the option of recycling post-consumer plastics has become more and more necessary. The main objective of this research is the selective separation of polypropylene (PP) and high density polyethylene (HDPE). On this basis, various flotation parameters were tested on virgin plastics and optimized conditions were applied to post-consumer plastics. PP particles with a purity of 96.30% were obtained with a recovery rate of 97.4% in virgin polymer separation, while HDPE particles were obtained as the sunken product with 97.38% purity and a recovery rate of 96.3%. Besides, almost all PP and HDPE particles were selectively separated with the highest recovery rates when using 500 g/t calcium lignosulfonate (CLs) as a plasticizer in post-consumer polymer separation. Moreover, water reuse was investigated to determine the recovery and economy of plasticizer without adding extra water during the experiment. Therefore, it can be concluded that this process is environmentally friendly in terms of PP and HDPE recycling and reuse of process water.