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Developing an Economical Identification Method for Plastics of Unknown Origin

AJAS · 2019

Matthew Adner · New Hampshire Science Academy

Overview

Plastics have become a critical pollutant in the world’s oceans and landfills. For example, it is estimated that more than 8 million tons of plastic enter the ocean every year. Given the prevalence of plastic, there is a need and pressure to do research on the effect of its presenc­e in the environment. A challenge that accompanies research on plastic pollution is that there are many different types of plastics that are hard to distinguish from one another. Current methods of detection use Fourier Transform Infrared Spectroscopy. This, however, is very costly and presents a significant barrier to entry for any group seeking to study plastics. Using a basic Beckman Coulter DU®520 General Purpose UV/Vis spectrophotometer, I have developed a promising approach for plastic identification. In this research I report preliminary findings for distinguishing between Polyvinylchloride (PVC), which is commonly used in water piping, and Polyethylene Terephthalate (PETE), which is commonly used in disposable water bottles. To test the viability of this procedure, I started with known plastic materials that I then ground into a powder, so that the material could be suspended in cuvettes for spectrophotometric analysis. The plastic powder was filtered through a series of sieves to get a uniform size between 300 and 150 microns. Two different amounts – 0.08g and 0.12g – of each plastic were suspended in a solution of 32.5% sucrose to 67.5% distilled water. One milliliter of this solution was added to quartz cuvettes and scanned in the spectrophotometer, registering absorption and percent transmittance (%T) at wavelengths between 200 and 1100nm, in 100nm increments. Each sample was scanned six times, and results for each scan were recorded. The reference sample cuvette contained only the sugar solution. Although there was variance in readings across the scans of each sample, the PVC and PETE profiles were highly distinguishable, with the highest readings of the one plastic lower than the lowest reading of the other in almost every wavelength. Thus, using a standard spectrophotometer, I was able to successfully distinguish Polyvinylchloride (PVC) from Polyethylene Terephthalate (PETE) according to their differing absorption and %T profiles. These initial results are promising as they show that it may be possible to develop a cost-effective system for identifying a broad variety of plastics.

Competition history

  • AJAS 2019 Category not listed

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Source: AAAS Annual Meeting (Confex) / American Junior Academy of Science

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