Coupling dechlorination and catalytic pyrolysis to produce carbon nanotubes from mixed polyvinyl chloride and polyethylene.

The presence of chlorine in polyvinyl chloride (PVC) presents a major challenge for realizing the high-value utilization of real waste plastics. The objective of this research was to develop a chlorine-resistant process for the preparation of carbon nanotubes (CNTs) from mixed plastics containing PVC. This study investigates the influence of PVC content and various dechlorinating agents (CaO, Na2CO3, red mud (RM), ZSM-5, Fe-Al2O3, Fe(OH)3) on CNTs formation. The results showed that PVC content exceeding 5 % significantly inhibits CNTs formation. Employing dechlorinating agents in the pyrolysis process results in a substantial yield of CNTs from mixed plastics containing 10 % PVC. Among the dechlorinating agents, RM proves to be the most effective, leading to the highest carbon yield (at 30 wt%) and superior CNTs quality. Other dechlorinating agents, except for ZSM-5, yield comparable results, although there were some obvious variations of volatiles. Further investigation of the role of dechlorinating agents from the perspective of volatiles evolution was conducted via Py-GC/MS, and found that the dechlorination agent efficiently absorbs the HCl from mixed plastics pyrolysis, while also exhibiting catalytic and regulatory influence on volatile components. These findings offer valuable insights for the development of a chlorine-resistant process in the preparation of CNTs from mixed plastics that contain PVC.

[Determination of Haloacetic Acids, Disinfection Byproducts, in Tap Water with Reversed-Phase Ultra-Performance Liquid Chromatography-High Resolution Mass Spectrometry].

Objective: To establish a method for quantitative analysis of haloacetic acids (HAAs), disinfection byproducts, in tap water with reversed-phase ultra-performance liquid chromatography-quadrupole-orbitrap high resolution mass spectrometry. Methods: Tap water samples were collected and 0.70 g/L ascorbic acid was added to eliminate residual chlorine. Then, the water samples were directly injected into the instrument for analysis after filtration. After separation on a pentafluorobenzene (PFP) column with an inner diameter of 1.0 mm at a higher linear velocity and a lower volume flow rate compared with those of a narrow-bore column, nine HAAs, namely, monochloroacetic acid (MCAA), monobromoacetic acid (MBAA), dichloroacetic acid (DCAA), bromochloroacetic acid (BCAA), dibromoacetic acid (DBAA), trichloroacetic acid (TCAA), bromodichloroacetic acid（BDCAA), chlorodibromoacetic acid (CDBAA) and tribromoacetic acid (TBAA), were examined by negative electrospray ionization and full MS/dd-MS 2 acquisition mode. In order to adjust for the matrix effect, matrix matching calibration curves were used to quantitate the nine HAAs. Results: Good linearity was obtained for each of the nine HAAs within their respective linear ranges. The detection limits and quantification limits of the method were 0.020-1.0 µg/L and 0.060-3.0 µg/L. The recoveries were 69.8%-119%. Conclusion: The proposed method showed strengths in separation speed and qualitative accuracy. It did not require for complicated pretreatment procedures and can meet the need of tap water sample analysis.