Waste Plastics Dissolved Air Flotation Separation

In order to separate mixed waste plastics PET_lv/PVC,PET_tou/PVC, ABS_h/PS_t and ABS_t/PS_tou,seven kinds of plastics PVC,PET_lv,PET_tou, ABS_h,ABS_t,PS_tou and PS_t were studied in this paper.Wetting agents calcium lignosulfonate,tannic acid 1#,tannic acid 2# and forth agent terpineol were chose as flotation agents in this study.Effects of parameters such as wetting agent,froth agent,flotation time,conditioning time and grain size etc.on flotation behaviors of every kind of plastics were investigated in a laboratory especially designed dissolved-air flotation column and then the optimized conditions for flotation separation of the mixed plastics were gained.Results of research on flotation behaviors of single plastic showed that:no matter for what kind of wetting agent,effects trend of flotation time,conditioning time and concentration of forth agent on the flotation behaviors of the seven kinds of plastics were similar;flotation time and conditioning time of 20min were adopted;frother dosage of 5mg/L could meet the requirement of flotation.Results of research on grain size distribution of raw materials and the floated materials showed that if the size of bubbles was unchanged,the floatability of small plastics particles was significantly better than that of the big ones.Results of research on flotation separation of the mixed plastics showed that:mixed plastics PET_tou/PVC was separated in the natural state; after single-stage separation the purity and recovery rate of PET_tou in the floated were 77.64%and 51.32%;the purity and recovery rate of PVC in the sank were 63.64%and 85.22%.Mixed plastics PET_lv/PVC was separated under the condition of LS concentration of 7000mg/L;after single-stage separation the purity and recovery rate of PET_lv in the floated were 74.06%and 78.33%;the purity and recovery rate of PVC in the sank were 77.00%and 72.56%.Mixed plastics ABS_h/PS_t was separated under the condition of TA1# concentration of 1500mg/L;after single-stage separation the purity and recovery rate of PS_t in the floated were 75.31%and 83.91%;the purity and recovery rate of ABS_h in the sank were 81.84%and 72.49%.Mixed plastics ABS_t/PS_tou was separated under the condition of TA2# concentration of 25mg/L;after two-stage separation,the purity and recovery rate of PS_tou in the floated were 90.12%and 97.45%;the purity and recovery rate of ABS_t in the sank were 97.24%and 89.38%.Compared with the flotation behaviors of single plastic,the whole flotation behaviors of mixed plastics changed a lot.In order to overcome the adverse effects of mixed plastics in flotation process,further systematic research on interaction between plastics particles was important in this field.