Study On The Adhesion Behavior Of Bubble-particle In Flotation Recycling Of Waste Plastics

To study the adhesion behavior of bubble on sphere surface, three kinds of plastic ballsPolypropylene (PP), Polyethylene (PE),Polytetrafluoroethylene (PTFE) were employed as theresearch object. Surfactants, sodium dodecyl benzene sulfonate (SDBS), cetyl trimethylammonium bromide (CTMAB) and Tea saponin (Tea Saponin) were chosen as flotationagents in this study. The effects of surfactant concentration, plastic material and surfactanttype on the adhesion behavior of a single bubble onto the plastic ball, as well as the adhesionrate of bubbles were investigated in a laboratory scale flotation column by using a high-speedcamera and image processing software. Results of this study are relevant for the description ofattachment mechanism and to determine the proper conditions for selective flotation ofplastics.The single bubble adhesion results showed that:①Different plastic materials had acertain influence on the bubble adhesion behavior. The visual processes of single bubbleimpacting different materials were consistent, and the change trends of speed were the same.For the same time, the rate of maximum bounce distance and bubble diameter (Smax/Ddep)values were the same too. The bubble rebound velocity, kinetic energy dissipation, as well asthree-phase contact time varied with the changing of sphere materials;②It was observedthat the concentration of surfactants affected the adhesion behavior. The bubblecollision-rebound velocity and frequency, as well as maximum bounce distance decreased,while the bubble kinetic energy dissipation increased with the increasing of SDBSconcentration. No three-phase contact onto the PP surface was observed when concentrationreached a certain value;③The surfactant type affected bubble adhesion behavior onto spheresurface, as it caused the differences of bubble velocity and maximum bounce distance. TheSmax/Ddepvalue was1.25,1,1in SDBS, CTMAB and Tea Saponin solution, respectively. Inaddition, bubble momentum dissipation was different in three kinds of surfactants solutions, itwas observed that the biggest was SDBS solution, CTMAB second, and tea saponin solutionminimal. Therefore, the three-phase contact times onto differences were also different. The bubbles adhesion rate results showed that:①The adhesion rate of PP surface wasimproved in surfactant solution compared with pure water. With the increasing of solutionconcentration, adhesion rates of three kinds of sphere surface increased first and thendecreased. Bubbles adhesion rate achieved maximum when the solution concentration reacheda certain value, then we continued to increase the concentration, bubbles started withoutadhesion onto PP surface, which indicated that the concentration was an important factoraffecting adhesion rate of bubbles. Through the single factor analysis of variance, we provedthat the concentration of surfactant has a highly significant effect on bubble adhesion behavioronce again, so during the plastic flotation process, the concentration of surfactant is a keyparameter that influences efficiency of plastic flotation.②Adhesion rate of bubbles onto PP,PTFE, PE surface in pure water was about13.37%,14.73%,5.15%, respectively; For the samePE surface, adhesion rate of bubbles reached maximum in SDBS solution was about24.32%,while in CTMAB solution15.38%, and in Tea Saponin solution minimum12.52%. Then weused the single factor analysis of variance for validation, it suggested that the type ofsurfactant and plastic material have a significant influence on adhesion rate of bubbles.