Sustainable Recovery of Valuable Nanoporous Materials from High-Chlorine MSWI Fly Ash by Ultrasound with Organic Acids.

The new technology development for municipal solid waste incineration fly ash treatment and reuse is urgent due to landfill shortage and environmental effect of leached hazardous substances. Chlorine (Cl) is worth considering due to its high levels in fly ash. In this study, a treatment process of ultrasound combined with organic acid was used to eliminate Cl from fly ash to enhance its properties for reuse. Taguchi methodology was implemented to design the experiments by controlling four impact factors and the contribution of each factor was evaluated by the ANOVA analysis of variance. Following two treatment steps within 5 min with a solid/liquid ratio of 1:10 at 165 kHz, 98.8% of Cl was eliminated. Solid/liquid ratio was the most prominent factor that contributed to the Cl removal with more than 90%, according to the ANOVA analysis of variance. Tert-butyl alcohol (tBuOH), an •OH radical scavenger, was utilized to examine different effects of ultrasonic cavitation on Cl removal efficiency. A 20 kHz ultrasound was used to explore the influence of multi-frequency ultrasound with different mechanical and sonochemical effects on the fly ash dechlorination. This ultrasonic-assisted organic acid treatment was found to be a time and cost-effective pathway for fly ash Cl removal.

Improving the indoor air quality of respiratory type of medical facility by zeolite filtering.

UNLABELLED: This study investigated the indoor air quality (IAQ) conditions of carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), formaldehyde (HCHO), total volatile organic compounds (TVOCs), and bio-aerosols (bacteria and fungi) in a respiratory type of medical facility in Chia-Yi County in southern Taiwan. Among those IAQ conditions, the concentrations of CO, O3, and HCHO exceeded the regulation values of the Taiwan Environmental Protection Administration (EPA) mostly in the morning. The concentrations of bacteria and fungi did not exceed the regulation values but still posed potential health and environment problems for workers, patients, and visitors. Therefore, self-made silver-coated zeolite (AgZ) was used as a filter material in air cleaners to remove bio-aerosols in the respiratory care ward (RCW), and the removals were still effective after 120 hr. The cumulative bio-aerosol removals for bacteria and fungi were 900 and 1,088 colony-forming units (CFU) g(-1) after 24 hr and were above 3,100 and 2,700 CFU g(-1) after 120 hr. From the research results, it is suggested that AgZ filtering could be used as a feasible engineering measure for hospitals to control their bacteria and fungi parameters in IAQ management. Hospitals should maintain their environmental management and monitoring programs and use different engineering measures to improve different IAQ parameters. IMPLICATIONS: This study investigated the IAQ conditions in the field at a hospital in Chia-Yi County in southern Taiwan. Although concentrations of most parameters were still within the regulation values, the concentrations of CO, O3, and HCHO were partially exceeded. We propose a method using an air cleaner with silver-coated zeolite (AgZ) as a possible engineering measure, and there were effective reductions of bacteria and fungi to lower levels with antibacterial effects after 120 hr. Furthermore, this study implies that hospitals should continuously maintain environmental monitoring programs and adopt optimal engineering measures for different needs.

Enhanced Visible-Light-Responsive Photocatalytic Degradation of Ciprofloxacin by the CuxO/Metal-Organic Framework Hybrid Nanocomposite.

Ciprofloxacin (CIP) is a commonly used antibiotic, however, once in the environment, it is highly toxic with a poor biodegradability. Given these attributes, an effective strategy for the removal of CIP is urgently needed for the protection of water resources. Herein, a novel copper metal-organic framework (CuxO/MOF) multifunctional material has been produced, in this work, by the calcination of Cu-MOF urea at 300 °C, in the presence of a 5% H2 atmosphere. The morphological, structural, and thermal properties of the prepared CuxO/MOF were determined through various techniques, and its photocatalytic behavior was investigated for the degradation of CIP under visible-light irradiation. The prepared CuxO/MOF bifunctional material is presented as a graphitic carbon-layered structure with a particle size of 9.2 ± 2.1 nm. The existence of CuO-Cu2O-C, which was found on the CuxO/MOF surface, enhanced the adsorption efficiency and increased the photosensitivity of CuxO/MOF, towards the degradation of CIP in aqueous solutions. The tailored CuxO/MOF, not only shows an excellent CIP degradation efficiency of up to 92% with a constant kinetic rate (kobs) of 0.048 min−1 under visible light, but it can also retain the stable photodegradation efficiency of >85%, for at least six cycles. In addition, CuxO/MOF has an excellent adsorption capacity at pH 6.0 of the maximum Langmuir adsorption capacity of 34.5 mg g−1 for CIP. The results obtained in this study demonstrate that CuxO/MOF is a reliable integrated material and serves as an adsorbent and photocatalyst, which can open a new pathway for the preparation of visible-light-responsive photocatalysts, for the removal of antibiotics and other emerging pollutants.

Levofloxacin degradation under visible-LED photo-catalyzing by a novel ternary Fe-ZnO/WO3 nanocomposite.

As semiconductor photocatalysts showing their efficient redox ability upon illumination, new development of materials to enhance the pollution degradation is gaining popularity, especially on their oxidation ability. In this study, a highly stable ternary Fe-ZnO/WO3 nanocomposite photocatalyst has been synthesized in order to improve charge transfer of photocatalytic oxidation under 30W LED light (425-470 nm) to efficiency degrade the Levofloxacin (LVF) in the solution. This catalyst was characterized and analyzed by XRD, FE-SEM, HR-TEM, X-ray XPS, UPS, PL, TRPL, LSV, EIS, and Photocurrent. Various important factors for the photodegradation were investigated, including Fe content, initial LVF concentration, catalyst dosage, and solution pH. The optimal conditions were Fe 1.0 wt%, LVF 10 mg L-1, Fe-ZnO/WO3 dosage 0.5 g L-1, and pH 7 for LVF photodegradation up to 96% with a kinetic rate constant of 0.0342 min-1 and were stable in photodegradation efficiency (90%) after five test cycles. In the visible LED light, the activation bandgap was estimated to be 2.75 eV with high electron-hole pair separation and charge transfer from Fe-ZnO to WO3 that could enhance the generation of active species of •OH. Moreover, the more effective charge separation of Fe-ZnO/WO3 were confirmed by lower PL intensity and longer charge carrier lifetime. Fe-ZnO/WO3 also demonstrated the excellent electrochemical properties with high photocurrent and small resistance. For the LVF degradation, 3 possible pathways were proposed with 12 intermediate products. This study demonstrated that the synthesized Fe-ZnO/WO3 could serve as a reliable visible-light responsive photocatalysts with the potential for degrading antibiotics in solution.

Novel quantification of formation trend and reaction efficiency of hydroxyl radicals for investigating photocatalytic mechanism of Fe-doped TiO2 during UV and visible light-induced degradation of acid orange 7.

A detailed mechanistic investigation of the hydroxyl radical (•OH) formation and organic pollutant degradation over transition metal-doped and undoped TiO2 photocatalysts was performed by the quantitative measurement of •OH and the identification of intermediate products under various experimental conditions. The Fe-doped TiO2 as a typical subject was prepared, characterized and used to degrade an azo dye Acid Orange 7 (AO7). It is indicated that the enhanced photocatalytic activity of Fe-doped TiO2 for AO7 degradation was attributed to the increase in surface area, the facilitated charge transfer via Fe-dopant, and a red shift of absorbable wavelength, maintaining a great formation of •OH under visible irradiation. The oxidation of H2O by holes was estimated as the major pathway of •OH formation rather than the reduction of dissolved O2 by electrons, and their formation trends reached to approximately 75% and 25%, respectively. Meanwhile the synergistic effect of Fe-dopant produced nearly 10% of extra •OH by visible light photoactivation. The intermediate products and pathways of AO7 degradation varied greatly with different photocatalysts and conditions of the process, involving several reaction mechanisms such as the azo bond cleaving, naphthalene oxidation, desulfonation, and hydroxylated products generation. Through the quantification of •OH-reacted efficiency we proposed, a stoichiometry of •OH affecting overall reaction mechanisms in the TiO2-assisted photodegradation of AO7 was further established. This study can provide new insights on how to better clarify the variation regularity of organic pollutant degradation from different treatments of the •OH-based advanced oxidation processes.

Volatile organic compounds (VOCs) emission characteristics and control strategies for a petrochemical industrial area in middle Taiwan.

This study investigated VOC emissions from the largest petrochemical industrial district in Taiwan and recommended some control measures to reduce VOC emissions. In addition to the petrochemical industry, the district encompasses a chemical and fiber industry, a plastics industry and a harbor, which together produce more than 95% of the VOC emissions in the area. The sequence of VOC emission was as follows: components (e.g., valves, flanges, and pumps) (47%) > tanks (29%) > stacks (15%) > wastewater treatment facility (6%) > loading (2%) > flares (1%). Other plants producing high-density polyethylene (HDPE), styrene, ethylene glycol (EG), gas oil, and iso-nonyl-alchol (INA) were measured to determine the VOC leaching in the district. The VOC emissions of these 35 plants (90% of all plants) were less than 100 tons/year. About 74% of the tanks were fixed-roof tanks that leached more VOCs than the other types of tanks. To reduce leaching, the components should be checked periodically, and companies should be required to follow the Taiwan EPA regulations. A VOC emission management system was developed in state implementation plans (SIPs) to inspect and reduce emissions in the industrial district.

The use of reactive index of hydroxyl radicals to investigate the degradation of acid orange 7 by Fenton process.

This study suggested the amount of hydroxyl radicals (OH) reacting with organics as a new index to evaluate the reaction efficiency (RE) of Fenton process, and used it to investigate the degradation mechanism of target pollution, Acid Orange 7 (AO7). The effects of initial concentrations of Fe(II), H2O2, and AO7 on RE were quantified by using response surface methodology (RSM). The main factors affecting RE were Fe(II), H2O2, and their interaction, and their percentage effects were 65.75, 11.99 and 22.23%, respectively. Moreover, based on the analysis result of RSM, a condition for good RE was proposed that it should ensure a higher amount of OH reacted with organics, and reduce the amount of OH scavenged by Fe(II). Liquid chromatography-mass spectrometry (LC/MS) analysis was used to identify the products of AO7 degradation in Fenton process, and there were three possible mechanisms to be observed, such as azo bond cleavage, hydroxylation, and oxidation of naphthalene ring. The trend of mechanisms might vary with the amount of OH attacks, and therefore the use of estimated RE could provide more particular information to better understand the relationship between organic degradation and OH attacks.

Chromate enhanced visible light driven TiO2 photocatalytic mechanism on Acid Orange 7 photodegradation.

When hexavalent chromium (Cr(VI)) is added to a TiO2 photocatalytic reaction, the decolorization and mineralization efficiencies of azo dyes Acid Orange 7 (AO7) are enhanced even though the mechanism is unclear. This study used 5,5-dimethyl-l-pyrroline-N-oxide (DMPO) as the scavenger and the analysis of Electron Spin Resonance (ESR) to investigate this enhancement effect by observing the hydroxyl radical (OH) generation of the Cr(VI)/TiO2 system under UV and visible light (Vis) irradiation. With Cr(VI), the decolorization efficiencies were approximately 95% and 62% under UV and Vis, and those efficiencies were 25% less in the absence of Cr(VI). The phenomena of the DMPO-OH signals during the ESR analysis under Vis 405 and 550 nm irradiation were obviously the enhancement effects of Cr(VI) in aerobic conditions. In anoxic conditions, the catalytic effects of Cr(VI) could not be achieved due to the lack of a redox reaction between Cr(VI) and the adsorbed oxygen at the oxygen vacancy sites on the TiO2 surfaces. The results suggest that by introducing the agents of redox reactions such as chromate ions, we could lower the photoenergy of TiO2 needed and allow Vis irradiation to activate photocatalysis.