Recent advances in the removal of persistent organic pollutants (POPs) using multifunctional materials:a review

Persistent organic pollutants (POPs) have gained heightened attentions in recent years owing to their persistent property and hazard influence on wild life and human beings. Removal of POPs using varieties of multifunctional materials have shown a promising prospect compared with conventional treatments. Herein, three main categories, including thermal degradation, electrochemical remediation, as well as photocatalytic degradation with the use of diverse catalytic materials, especially the recently developed prominent ones were comprehensively reviewed. Kinetic analysis and underlying mechanism for various POPs degradation processes were addressed in detail. The review also systematically documented how catalytic performance was dramatically affected by the nature of the material itself, the structure of target pollutants, reaction conditions and treatment techniques. Moreover, the future challenges and prospects of POPs degradation by means of multiple multifunctional materials were outlined accordingly. Knowing this is of immense significance to enhance our understanding of POPs remediation procedures and promote the development of novel multifunctional materials.

Photochemical conversion of toluene in simulated atmospheric matrix and characterization of large molecular weight products by +APPI FT-ICR MS

The lack of kinetic parameters of VOC photochemical conversion especially in the presence of NO and O₃, and product information, will result in the incomplete understanding for the occurrence of haze. In the present study, the photochemical conversion of toluene, one of most significant hydrocarbons of VOCs, in toluene, toluene/NO, toluene/O₃ and reaction systems was assessed for up to 4 days in a smog chamber at 278 K and 308 K. The results indicated that the addition of NO and O₃ promoted the conversion of toluene. The first-order kinetic rate constants of toluene assessed in the toluene reaction system at 278 K and 308 K were 0.12 and 0.19 day^-1, respectively. The second-order kinetic rate constants of toluene assessed in the toluene/NO were 0.1 × 10^-13 cm³ molecule^-1 day^-1 (at 278 K) and 0.9 × 10^-13 cm³ molecule^-1 day^-1 (at 308 K), and those in the toluene/O₃ reaction systems were 0.06 × 10^-12 cm³ molecule^-1 day^-1 (at 278 K) and 0.11 × 10^-12 cm³ molecule^-1 day^-1 (at 308 K). The small difference of second-order kinetic rate constants between 278 K and 308 K obtained for the toluene/O₃ system when compared with the toluene/NO system indicated the reduced reaction sensitivity of O₃ to the temperature. Several dozens of large molecule products containing up to O₆ heteroatoms were identified by positive ion atmospheric pressure photoionization (+APPI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), with double bond equivalents up to 18, and carbon numbers ranging within 12-38, respectively. The findings presented herein may provide a new train of thought for the photochemical reaction process of toluene and its conversion in ambient air.