Scientific Reports (Mar 2023)

Rapid oxidative fragmentation of polypropylene with pH control in seawater for preparation of realistic reference microplastics

  • Hisayuki Nakatani,
  • Yuina Ohshima,
  • Taishi Uchiyama,
  • Suguru Motokucho,
  • Anh Thi Ngoc Dao,
  • Hee-Jin Kim,
  • Mitsuharu Yagi,
  • Yusaku Kyozuka

DOI
https://doi.org/10.1038/s41598-023-31488-w
Journal volume & issue
Vol. 13, no. 1
pp. 1 – 8

Abstract

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Abstract Various tiny plastic particles were retrieved from the sea and studied using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analysis to prepare realistic reference microplastics (MP). Most of the MP exhibited a diameter of < 20 × 10−6 m and 0.1–0.2 molar ratios of oxygen to carbon atoms (O/C), indicating that they primarily comprised polyethylene (PE), polypropylene (PP), and polystyrene (PS). It took a long time to reproduce such O/C ratios in standard laboratory weathering methods. For example, degrading of 30 × 30 × 0.060 mm PP film required 75 days for the 0.1 ratio, even with an advanced oxidation process (AOP) using a sulfate radical anion (SO4·−) initiator in distilled water at 65 °C. However, seawater drastically improved the PP degradation performance of AOP under a weak acid condition to achieve the 0.1 ratio of PP film in only 15 days. The combination of seawater and the SO4·− initiator accelerated the degradation process and showed that the MP’s size could be controlled according to the degradation time.