Removal of PAHs from Road Drainage System by Ultrasonication

The articles reveal the removal effectiveness of 7 polycyclic aromatic hydrocarbons (PAHs), which were recognized in water from a highway drainage system by using the ultrasound treatment process. Results showed that after 45 min of sonication, the average removal of PAHs reached 59%. The reduction of analyzed substances was proportional to treated time and irradiation amplitude. Furthermore, as a consequence of ozone addition to the sonicated samples, the efficiency of the treatment was significantly higher.

Photocatalytic Removal of Toluene with CdIn2S4/CNFs as Catalyst: Effect of Ozone Addition

CdIn2S4 (CIS) has attracted much attention in the photocatalysis research field due to its structural stability and photoelectric properties. However, it's difficult to recycle when after usage, so application of CIS photocatalysis in removing volatile organic compounds (VOCs) is still limited and the literature on applying carbon nanofibers (CNFs) as electron acceptor is scarce. In this study, a novel CIS/CNFs composite was synthesized via a simple hydrothermal method. X-ray diffraction (XRD), Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to characterize the structure, microtopography and composition of CIS/CNFs photocatalyst prepared. The results showed that CNFs with the size of about 300 nm were favorable connected with CIS to form 3D conductive network and CIS particles with the average size of 100 nm grew onto the surface of CNFs uniformly. Results of photocatalytic degradation tests indicate that under visible light irradiation, degradation of toluene reached the optimal level of 86% as the CIS doped with 3% CNFs. It proved that the composite material prepared had an excellent photocatalytic recycle efficiency via repeated experiments. Furthermore, 95% removal efficiency was achieved as 200 ppm ozone was added into the system and mineralization rate are also improved. Derived from the intermediates detected, possible pathways of toluene degradation were proposed. Hence, this study presents a new method to synthesize photocatalyst with visible-light driven ozone-enhanced photocatalysis process toward indoor air pollutants removal VOCs.

Formation kinetics and mechanisms of ozone and secondary organic aerosols from photochemical oxidation of different aromatic hydrocarbons: dependence on NO_<i>x</i> and organic substituents

Aromatic hydrocarbons (AHs) contribute significantly to ozone and secondary organic aerosol (SOA) formation in the atmosphere, but their formation mechanisms are still unclear. Herein, the photochemical oxidation of nine AHs was investigated in a chamber. Only a small amount of ozone was produced from the direct photochemical oxidation of AHs, while a lower number of AH substituents resulted in higher concentrated ozone. Addition of NOx increased ozone and SOA production. The synergetic effect of accelerated NO2 conversion and NO reaction with AHs boosted ozone and volatile intermediate formation. Promoting AH concentration in the VOC / NOx ratio further increased formation rates and concentrations of both ozone and SOA. Additionally, ozone formation was enhanced with increasing AH substituent number but negligibly affected by their substituent position. Differently, SOA yield decreased with an increased substituent number of AHs but increased with ortho-methyl-group-substituted AHs. Model fitting and intermediates consistently confirmed that increasing the substituent number on the phenyl ring inhibited generation of dicarbonyl intermediates, which however were preferentially produced from oxidation of ortho-methyl-group-substituted AHs, resulting in different changing trends of the SOA yield. The restrained oligomerization by increased substituent number was another main cause for decreased SOA yield. These results are helpful to understand the photochemical transformation of AHs to secondary pollutants in the real atmosphere.

Magnetic cotton textile wastes pyrolyzed by ferric cerium oxide for degradation of p-nitrophenol by catalytic ozonation

In this paper, magnetic cotton textile wastes pyrolyzed by ferric cerium oxide (FexCey oxide/PC) were synthesized for degradation of p-nitrophenol by catalytic ozonation, and the optimal Fe-Ce ratio was 10:1. Compared to Fe10Ce1 oxide, the Fe10Ce1 oxide/PC not only greatly improved the degradation efficiency of PNP, but also reduced the dosage of catalyst. Through the BET test, the Fe10Ce1 oxide/PC has a high specific surface area to absorb part of the pollutants. VSM test shows that the material is magnetic and easy to recycle. Response surface methodology (RSM) was applied to optimize the experimental condition, and the optimal removal rate was 90% when the initial pH was 9, the catalyst dosage was 0.4 g/L, and the ozone addition was 1.77 L/min (5.9 mg/L). Finally, the mechanism of PNP degradation was explored utilizing inhibitor and ESR free radical detection. The adsorption capacity of the material and electron-absorbing property of PNP jointly determined the high catalytic efficiency with Fe10Ce1 oxide/PC in catalytic ozonation.

Formation kinetics and mechanism of ozone and secondary organic aerosols from photochemical oxidation of different aromatic hydrocarbons: dependence of NO_x and organic substituent

Aromatic hydrocarbons (AHs) contribute significantly to ozone and secondary organic aerosol (SOA) formation in atmosphere, but formation mechanisms are still unclear. Herein, photochemical oxidation of nine AHs was investigated in chamber. Only small amount of ozone was produced from direct photochemical oxidation of AHs, while fewer AH substituent number resulted in higher concentrated ozone. Addition of NOx increased ozone and SOA production. Synergetic effect of accelerated NO2 conversion and NO reaction with AHs boosted ozone and volatile intermediate formation. Promoting AH concentration in VOC / NOx ratio further increased formation rates and concentrations of both ozone and SOA. Additionally, ozone formation was enhanced with increasing AH's substituent number but negligibly affected by their substituent position. Differently, SOA yield decreased with increased substituent number of AHs, but increased with ortho methyl group substituted AHs. Model fitting and intermediate consistently confirmed that increasing substituent number on phenyl ring inhibited generating dicarbonyl intermediates, which however were preferentially produced from oxidation of ortho methyl group substituted AHs, resulting in different changing trend of SOA yield. The restrained oligomerization by increased substituent number was another main cause for decreased SOA yield. These results are helpful to understand photochemical transformation of AHs to secondary pollutants in real atmosphere.

Optimization of gasoline compression ignition combustion with ozone addition and two-stage direct-injection at middle loads

Ozone (O3) was introduced into the intake air to control the ignition in a gasoline compression ignition (GCI) engine. An early fuel injection at −68 °CA ATDC was adopted to mix the fuel with the reactive O-radicals decomposed from the O3, before the reduction of the O-radicals due to their recombination would take place. The second injection was implemented near top dead center to optimize the profile of the heat release rate. The engine experiments were performed around the indicated mean effective pressure (IMEP) of 0.67 MPa with a primary reference fuel, octane number 90 (PRF90), maintaining the 15% intake oxygen concentration with the EGR. The quantity of the first injection, the second injection timing as well as the ozone concentration were changed as experimental parameters. The results showed that the GCI operation with the ozone addition makes it possible to reduce the maximum pressure rise rate while attaining high thermal efficiency, compared to that without the ozone. Appropriate combinations of the ozone concentration and the first injection quantity achieve low smoke and NOx emissions. Further, the ozone-assisted GCI operation was compared with conventional diesel operation. The results showed that the indicated thermal efficiency of the ozone-assisted GCI combustion is slightly lower than that of the conventional diesel combustion, but that GCI assisted with ozone is highly advantageous to the smoke and NOx emissions.