Photocatalytic conversion of gaseous nitrogen trichloride into available chlorine--experimental and modeling study

Experimental Proof of a Transformation Product Trap Effect with a Membrane Photocatalytic Process for VOC Removal

The decomposition of volatile organic compounds by photocatalytic oxidation (PCO) has been widely studied. However, the technological development of this oxidative technique has to address how to handle the formation of transformation products. The work presented here investigates the original combination of a dense membrane separation process and PCO to intensify the trapping and reduction of PCO transformation products. Specific monitoring of toluene PCO transformation products, such as benzene and formaldehyde, in the outflow of both permeate and retentate compartments was proposed. The influence of operating parameters on the process, i.e., light intensity, pressure, membrane type, and catalyst mass, was also studied. The results reveal that membrane separation-PCO hybridization is particularly effective for reducing the presence of benzene and formaldehyde in the effluent treated. The benzene concentration in the outflow of the hybrid module can be reduced by a factor of 120 compared to that observed during the PCO of toluene alone.

Membrane-Based Portable Colorimetric Gaseous Chlorine Sensing Probe

Highly toxic chlorine gas imposes serious health risks in the workplace. The ability to on-site, real-time monitoring of instantaneous and time-weighted average (TWA) chlorine gas concentrations in a simple, sensitive, accurate, and reliable manner would be highly beneficial to improve workplace health and safety. Here, we propose and experimentally validate a gaseous chlorine detection principle based on a N,N-diethyl-p-phenylenediamine sulfate salt/Cl₂ colorimetric reaction-controlled membrane process to regulate the gaseous chlorine transport across a gas-permeable membrane that enables the establishment of a time-resolved analytical relationship to quantify chlorine concentration by multidata points with dramatically enhanced accuracy and reliability. A gas-permeable membrane-based portable colorimetric gaseous chlorine sensing probe (MCSP) was designed and fabricated. The MCSP embedded the proposed analytical principle that is capable of real-time continuous monitoring of the instantaneous and TWA chlorine gas concentrations within an analytical range of 0.009-2.058 mg L^-1 without the need for on-going calibration, which could be a useful analytical tool for managing the toxic chlorine gas-imposed health risks in workplaces.

The C2N surface as a highly selective sensor for the detection of nitrogen iodide from a mixture of NX3 (X = Cl, Br, I) explosives

Explosives are quite toxic and destructive; therefore, it is necessary to not only detect them but also remove them. The adsorption behavior of NX₃ analytes (NCl₃, NBr₃ and NI₃) over the microporous C₂N surface was evaluated by DFT calculations. The nature of interactions between NX₃ and C₂N was characterized by adsorption energy, NCI, QTAIM, SAPT0, NBO, EDD and FMO analysis. The interaction energies of NX₃ with C₂N are in the range of −10.85 to −16.31 kcal mol⁻¹ and follow the order of NCl₃@C₂N > NBr₃@C₂N > NI₃@C₂N, respectively. The 3D isosurfaces and 2D-RGD graph of NCI analysis qualitatively confirmed the existence of halogen bonding interactions among the studied systems. Halogen bonding was quantified by SAPT0 component energy analysis. The SAPT0 results revealed that ΔE_disp (56.75%) is the dominant contributor towards interaction energy, whereas contributions from ΔE_elst and ΔE_ind are 29.41% and 14.34%, respectively. The QTAIM analysis also confirmed the presence of halogen bonding between atoms of NX₃ and C₂N surface. EDD analysis also validated NCI, QTAIM and NBO analysis. FMO analysis revealed that the adsorption of NI₃ on the C₂N surface caused the highest change in the E_HOMO–LUMO gap (from 5.71 to 4.15 eV), and resulted in high sensitivity and selectivity of the C₂N surface towards NI₃, as compared to other analytes. It is worth mentioning that in all complexes, a significant difference in the E_HOMO–LUMO gap was seen when electronic transitions occurred from the analyte to the C₂N surface.

Explosives are quite toxic and destructive; therefore, it is necessary to not only detect them but also remove them.