ENVIRONMENTALLY SOUND MANAGEMENT OF WASTE PET BOTTLES. A RESEARCH PROJECT MATERIAL ON ENVIRONMENTAL SCIENCE
This study has been carried out to assess the waste management of PET bottles and effectively manage the PET plastic bottles by identifying practical means and introducing recycling as cleaner production tool to achieve sustainable development goals. The science of post-consumer PET recycling is based on the fact that this polymer is non-degradable by nature. There has been a growing need for chemical recycling processes as a successful method for post-consumer PET transformation into monomers that can be used in the production of new bottles, textile materials, drug production etc. This research focused on the depolymerisation of waste PET bottles in alkaline medium with the aim of response surface methodology.
PET flakes from waste bottles were depolymerized at atmospheric pressure in alkaline solution of potassium hydroxide in selected aliphatic alcohols and glycol to produce terephthalic acid. Response Surface Methodology (RSM) based on Central Composite Design model was used, with design variables being temperature, reaction time and alkali concentration. The solid product was analyzed using FTIR and its acid value was determined.
From the results obtained, it was found that reaction models obtained are significant (p < 0.05 for alcohols), accounting to 98% of the variations observed. For ethanol media, the optimum condition for PET decomposition was 0.35g/L, 66.82mins and 2000C, which gave the decomposition of 79.4%. For propylene glycol, an optimum decomposition of 74.6% was obtained at a reaction temperature, time and alkali concentration of 2200C, 60mins and 0.5g/L respectively. For propylene glycol, the reaction time had more effect on the percentage decomposition, while temperature was the dominant factor for the ethanol media. Comparing the IR spectra of the final product obtained from the alcohol with that of pure terephthalic acid, it can be concluded that the solid product obtained was terephthalic acid which can be use in pharmaceutical industries as a raw material in producing certain drugs.