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Designed for Molecular Recycling: A Lignin-Derived Semi-aromatic Biobased Polymer
Published on: November 30, 2020
Mechanochemical decomposition of PVC by using La2O3 as additive
William Tongamp1, Qiwu Zhang, Fumio Saito
1Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-8577, Japan. bune@andy.tagen.tohoku.ac.jp
Journal of Hazardous Materials
|May 23, 2006
Summary
Lanthanum oxide (La2O3) effectively decomposes polyvinyl chloride (PVC) through mechanochemistry, forming insoluble lanthanum oxy-chloride (LaOCl). Calcium oxide (CaO) also decomposes PVC but yields water-soluble products, with slower reaction rates.
Area of Science:
- Materials Science
- Polymer Chemistry
- Green Chemistry
Background:
- Polyvinyl chloride (PVC) is a widely used plastic with environmental concerns regarding its disposal.
- Mechanochemical (MC) decomposition offers a solvent-free method for chemical transformations.
- Investigating additives for efficient PVC degradation is crucial for sustainable waste management.
Purpose of the Study:
- To investigate the mechanochemical decomposition of PVC using lanthanum oxide (La2O3) and calcium oxide (CaO).
- To compare the efficiency of La2O3 and CaO as additives in the MC decomposition of PVC.
- To characterize the decomposition products and understand the reaction mechanisms.
Main Methods:
- Mechanochemical grinding of PVC with La2O3 and CaO.
- X-ray diffraction (XRD) analysis to identify crystalline products.
- Thermogravimetric (TG) analysis to assess thermal stability and decomposition.
- Fourier-transform infrared (FT-IR) spectroscopy to analyze chemical bond changes.
- Water leaching to quantify extracted chloride.
Main Results:
- Grinding PVC with La2O3 produced insoluble lanthanum oxy-chloride (LaOCl) within 20 minutes.
- Grinding PVC with CaO produced water-soluble calcium hydroxychloride (CaOHCl) after 2 hours.
- La2O3 demonstrated higher efficiency in MC decomposition of PVC compared to CaO, indicated by minimal weight loss in TG analysis.
- FT-IR showed a reduction in C-Cl bonds in PVC upon grinding, with C-O bond formation during the reaction with La2O3.
- Water leaching extracted <50% of chloride from PVC-La2O3 mixtures, versus ~100% from PVC-CaO mixtures.
Conclusions:
- Lanthanum oxide is a more effective additive than calcium oxide for the mechanochemical decomposition of PVC, forming a water-insoluble product (LaOCl).
- The insolubility of LaOCl limits chloride extraction by water leaching, suggesting potential for controlled chlorine sequestration.
- Mechanochemical treatment with CaO leads to efficient chloride removal due to the formation of water-soluble CaOHCl.
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