Online measurement of 1,2,4-trichlorobenzene as dioxin indicator on multi-walled carbon nanotubes

Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) emission is one of main concerns for the secondary pollution of municipal solid waste incinerators (MSWI). For timely response to emission, 1,2,4-trichlorobenzene (1,2,4-TrCIBz) as dioxin indicator can be monitored via online measurement techniques. In this study, multi-walled carbon nanotubes (MWCNTs) were investigated for their suitability as a 1,2,4-TrCIBz sorbent for MSWI stack gas analysis. The tests include, batch adsorption, continuous adsorption-desorption of 1,2,4-TrCIBz via thermal desorption coupled with gas chromatography (TD-GC-ECD), temperature and concentration stability of MWCNTs, and adsorption performance of the system. Thermogravimetric/derivative thermogravimetric (TGA/DTG) analysis reveals that MWCNTs has higher capacity in terms of weight loss (14.34%) to adsorb 1,2,4-TrCIBz compared to Tenax TA (9.46%) and also shows fast desorption of adsorbate at temperature of 87 degrees C compared to Tenax TA (130 degrees C). Interestingly, carbon nanotubes and Tenax TA gave almost similar adsorption-desorption response, and from TD-GC-ECD analysis it was found that with increasing mass flow of 1,2,4-TrCIBz (7.42 x 10(-6) - 44.52 x 10(-6) mg ml(-1)) through sorbent traps, average peak areas increased from 2.86 +/- 0.02 to 13.54 +/- 0.26 for MWCNTs and 2.89 +/- 0.02 to 13.38 +/- 0.12 for Tenax TA, respectively. The stability of MWCNTs for temperature was 400 degrees C and for concentration of 1,2,4-TrCIBz was 50 ppbv. However, regeneration of sorbent at 100 ppbv (1,2,4-TrCIBz) was not possible. TD-GC-ECD system showed high adsorption performance with 3.86% and 3.59% relative standard deviation at 250 degrees C and 300 degrees C, respectively. Further Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that adsorbate can be fully desorbed at 300 degrees C. 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study found that multi-walled carbon nanotubes (MWCNTs) have higher adsorption capacity to adsorb 1,2,4-TrCIBz compared to Tenax TA, and can desorb at a lower temperature. MWCNTs showed good stability for concentration and temperature of 1,2,4-TrCIBz, but regeneration was not possible at 100 ppbv.