Separation of mixed post-consumer PET–POM–PVC plastic waste using selective flotation

Abstract The main objective of this research is to separate a mixed post-consumer engineering plastic waste (PET, POM, and PVC) based on type of plastic using selective flotation separation. Depressing effect of wetting agent and aluminium sulfate on plastic is attributed mainly to the separation. POM is separated from the mixture waste when using 500 mg/l calcium lignosulfonate as a wetting agent at pH 7 and air flow rate of 220 ml/min. It renders POM more hydrophilic and causes higher wettability. This corresponds to its smaller contact angle. It is found from the results that POM has smaller contact angle than PET and PVC, respectively. Therefore, POM remains in the flotation solution while air bubbles are attaching to PET and PVC. To succeed in separation of PET from PVC by selective flotation, 500 mg/l calcium lignosulfonate and 0.01% (w/v) Al 2 (SO 4 ) 3 is added to a flotation solution at pH 5.8 and air flow rate of 180 ml/min. Negative charge ions on plastic surface are neutralized by aluminium ions. Additional, pH of solution is changed from 7 to 5.8 when 0.01% (w/v) adding Al 2 (SO 4 ) 3 . Magnitude of zeta-potential of PET and PVC changes from negative to positive value when changing basic condition to acidic one. In this current work, point of zero charge of PET and PVC are investigated. At point of zero charge, surface of plastic has a complete hydrophobic property. pH of solution plays an important role in flotation separation.

[1]  R. D. Pascoe,et al.  Flame treatment for the selective wetting and separation of PVC and PET. , 2003, Waste management.

[2]  Eric Forssberg,et al.  A review of plastics waste recycling and the flotation of plastics , 1999 .

[3]  B. Yarar,et al.  Recovering plastics for recycling by mineral processing techniques , 1995 .

[4]  Jorge Alberto Soares Tenório,et al.  Use of froth flotation to separate PVC/PET mixtures , 2000 .

[5]  N. Fraunholcz,et al.  Separation of waste plastics by froth flotation––a review, part I , 2004 .

[6]  R. D. Pascoe.  The use of selective depressants for the separation of ABS and HIPS by froth flotation , 2005 .

[7]  Claus Mølgaard,et al.  Environmental impacts by disposal of plastic from municipal solid waste , 1995 .

[8]  E. Forssberg,et al.  Floatability, selectivity and flotation separation of plastics by using a surfactant , 2002 .

[9]  Jaroslaw Drelich,et al.  The effect of drop (bubble) size on advancing and receding contact angles for heterogeneous and rough solid surfaces as observed with sessile-drop and captive-bubble techniques , 1996 .

[10]  P. Basařová,et al.  The influence of flotation agent concentration on the wettability and flotability of polystyrene. , 2005, Journal of colloid and interface science.

[11]  K. Askvik.  Properties of the lignosulfonate–surfactant complex phase , 2001 .

[12]  T. Meloy,et al.  Low dense media process : a new process for low-density solid separation , 1999 .

[13]  C. Le Guern,et al.  Role of calcium ions in the mechanism of action of a lignosulphonate used to modify the wettability of plastics for their separation by flotation , 2000 .

[14]  Bimal P. Singh.  Wetting mechanism in the flotation separation of plastics , 1998 .

[15]  Junji Shibata,et al.  Flotation separation of plastics using selective depressants , 1996 .

[16]  J. H. Kim,et al.  Purification of polyethylene terephthalate from polyvinyl chloride by froth flotation for the plastics (soft-drink bottle) recycling industry , 1999 .

[17]  R. D. Pascoe,et al.  Investigation of the importance of particle shape and surface wettability on the separation of plastics in a LARCODEMS separator , 1999 .