A new acridine-based photosensitizer with ultra-low light requirement efficiently inactivates carbapenem-resistant Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus and degrades their antibiotic resistance genes.

The spread of antibiotic resistant pathogens and antibiotic resistance genes (ARGs) in the environment poses a serious threat to public health. However, existing methods are difficult to effectively remove antibiotic resistant pathogens and ARGs from the environment. In this study, we synthesized a new acridine-based photosensitizer, 2,7-dibromo-9-mesityl-10-methylacridinium perchlorate (YM-3), by the heavy atom effect, which could photodynamically inactivate antibiotic resistant pathogens and reduce ARGs by generating singlet oxygen (1O2) in an aqueous environment. The 1O2 yield of YM-3 was 4.9 times that of its modified precursor. YM-3 could reduce the culturable number and even the viable counts of methicillin-resistant Staphylococcus aureus and carbapenem-resistant Acinetobacter baumannii to 0 (inactivation rate > 99.99999%) after 2 and 8 h of low-intensity blue light (15 W/m2) irradiation, respectively. After 20 h of light exposure, the copy numbers of ARGs in both bacteria were reduced by 5.80 and 4.48 log, respectively, which might indicate that ARGs had been degraded. In addition, YM-3 still had an efficient bactericidal effect after five inactivation cycle. These characteristics of ultra-low light intensity requirement and efficient bactericidal ability make YM-3 have good application prospects for disinfection in indoor and sunlight environment.

MnOx@N-doped carbon nanosheets derived from Mn-MOFs and g-C3N4 for peroxymonosulfate activation: Electron-rich Mn center induced by N doping.

The fabrication of metal-carbon hybrids with heteroatom doping from manganese-metal organic frameworks (MOFs) has rarely been reported for peroxymonosulfate (PMS) activation. In this work, novel MnOx@N-doped carbon (MnOx@NC) nanosheets were prepared using 2D manganese-1,4 benzenedicarboxylic acid-based MOFs (Mn-MOFs) and different proportions of graphitic carbon nitride (g-C3N4, additional N source and carbon source) to activate PMS for sulfamethoxazole (SMX) removal. The polarization difference induced by Mn-N coordination during the carbonization process made C an electron-poor center and Mn an electron-rich center, thus providing more Mn(II) for PMS activation. Benefiting from the highest Mn(II) content, the most uniform and exposed MnOx active sites, abundant N active species and rich defective sites, MnOx@NC-20 showed excellent degradation (72.9% within 5 min) and mineralization performance (47.40% within 60 min) for SMX. Nonradical and radical processes worked together in MnOx@NC-20/PMS/SMX system, where singlet oxygen (1O2) dominated the degradation of SMX. N-doped carbon not only exhibited dragging and protection effects on MnOx, but also provided adsorption sites for PMS and pollutants, thus reducing their migration distance. Moreover, the electrons of organic substrates could be captured by the electron-poor carbon layer and then transported to the electron-rich Mn center, thus improving the utilization efficiency of PMS and the redox of Mn. This study provides a facile optimization method to prepare MOFs-derived carbon catalysts with improved stability and catalytic performance.

A ZIF-8-derived copper-nitrogen co-hybrid carbon catalyst for peroxymonosulfate activation to degrade BPA.

A series of copper-nitrogen co-hybrid porous carbon catalysts were prepared by pyrolysis of copper-doped ZIF-8 in argon atmosphere. Both the precursors and the corresponding pyrolysis products retained the polyhedral morphology of ZIF-8. The catalytic performance of the catalysts obtained at different Cu doping levels and pyrolysis temperatures for PMS activation was compared by bisphenol A (BPA) degradation experiment. Among them 5%Cu-NC(8) catalyst obtained by pyrolysis of 5%Cu-ZIF-8 at 950 °C showed the best catalytic performance. The catalytic mechanism of PMS activation catalyzed by 5%Cu-NC(8) was analyzed by quenching experiment, ESR and XPS. The degradation pathways of BPA in 5%Cu-NC(8)/PMS system were proposed on the basis of LC-MS analyses. Pyridine N (including Cu-N), graphite N, CO group and the valence change of Cu were recognized as the catalytic active sites for 5%Cu-NC(8). Both free radical and non-free radical processes were involved in BPA degradation, and singlet oxygen (1O2) was identified to be the main active substance. The stable performance and low Cu leaching rate in recycling experiment indicated that 5%Cu-NC(8) had good reusability and stability. This study provided a new insight for the design of heterogeneous copper-nitrogen co-hybrid carbon catalysts.

Pyridazine doped g-C3N4 with nitrogen defects and spongy structure for efficient tetracycline photodegradation and photocatalytic H2 evolution.

In this study, with thiourea and 3-aminopyridazine as precursors, the graphite-phase carbon nitride (ACN-x) with nitrogen defects and sponge structure is prepared via the introduction of the benzene-like ring structure of pyridazine replacing a "melem" group through hydrothermal procedure combined with calcination. It is made possible by the attraction of three hydrogen bond receptors for 3-aminopyrazine to lone pair electrons on the "melem" molecule. The remarkable extensively photocatalytic activity can be attributed to three effects of the introduction of 3-aminopyridazine: (i)formation of nitrogen defects between adjacent tri-s-triazine groups; (ii)formation of effective charge transfer channels within the tri-s-triazine group; (iii)the spongy structure exposed abundant amino groups(-NH3) at edge sites, combining with the internal amino group and as hole stabilizer to prolong the excited state life of photocatalyst. The photogenerated carrier migration and separation efficiency improved effectively through the tuning synergy. As a result, ACN-x exhibits excellent photocatalytic activity, with hydrogen production efficiency of up to 11331.74 µmol g-1 h-1, which is approximately 94.5 times that of the pristine g-C3N4 (119.88 µmol g-1 h-1). The degradation constants of TC and RhB are 0.0498min-1 and 0.129min-1, which are 3.32 and 6.35 times of the pristine g-C3N4, respectively. The TC degradation in different initial concentrations, pH, dissolved organic matter concentrations, and water sources is conducted to prove the environmental adaptability of the ACN-x system. The mechanism of the system indicates that ·O2- plays an important role, and the ·OH and h+ play a minor role in the TC photocatalytic degradation. Finally, the TC degradation possible pathway is proposed.

Synergistic role of inherent calcium and iron minerals in paper mill sludge biochar for phosphate adsorption.

Phosphate adsorption using metal-based biochar has awakened much attention and triggered extensive research. In this study, novel Ca/Fe-rich biochars were prepared via a one-step process of pyrolyzing paper mill sludge (PMS) at various temperatures (300, 500, 700, and 800 °C) under a CO2 atmosphere for phosphate removal. Batch adsorption experiments showed that the biochar obtained at 800 °C (PB-800), which could be easily separated magnetically, exhibited the best phosphate adsorption capacity in a wide range of solution pH (5-11). Based on the Langmuir model, the maximum phosphate adsorption capacity for PB-800 was 17.33 mg/g. Besides, the effects of ambient temperature as well as coexisting ions on phosphate removal were also investigated. Kinetic and thermodynamic analysis revealed that chemisorption dominated the adsorption process. The calcium carbonate and ferric salts in the sludge were converted into CaO and Fe3O4 through pyrolysis at 800 °C. The CaO inherent in PB-800 was proved to serve as active sites for the chemical precipitation, showing its synergistic effect with iron oxide compounds (i.e., Fe3O4, α-Fe2O3) on phosphate removal through chemical precipitation, ligand exchange, and complexation. This study not only provides a feasible waste-to-wealth strategy for converting PMS into a Ca/Fe-rich magnetic biochar that can be used as an effective phosphate adsorbent, but also offers new insights into the synergistic effect of calcium and iron species for the adsorption of phosphate using biochar.

Removal of Sb(V) from wastewater via siliceous ferrihydrite: Interactions among ferrihydrite, coprecipitated Si, and adsorbed Sb(V).

Although ferrihydrite (Fh) exhibits good Sb(V) adsorption behavior, the instability of its amorphous structure limits its engineering applications. In this study, siliceous ferrihydrite (SiFh) was prepared via coprecipitation to resolve these limitations. X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and SiFh aging tests revealed that the growth of Fh particles covered with Fe-O-Si links was inhibited while maintaining their amorphous structure. Meanwhile, the XRD patterns indicated that SiFh maintained excellent stability after five adsorption-desorption cycles. During the aging process, the added Si decreased the electrostatic interaction between SiFh and Sb(V), which weakened the affinity between Sb(V) and Fh; however, most of the Sb(V) still entered the Fe lattice after seven days of aging, which was favorable for Sb(V) recovery during reutilization. Furthermore, Sb(V) adsorbed from the simulated textile wastewater onto SiFh had the highest adsorption energy (Eads), which meant its unstable inner-sphere complexation on the surface of SiFh. Meanwhile, the presence of SO42-, NO3-, Ca2+, and Mg2+ contributed to Sb(V) outer-sphere adsorption. Both of these factors were conducive to Sb(V) desorption. Hence, SiFh is a promising adsorbent owing to its facile preparation process, stability, and optimal regeneration properties.

Interface mechanisms of the catalytic ozonation of humic acids over siliceous ferrihydrite: Morphology, stability, and the catalytic process.

Ferrihydrite (Fh), a precursor of more crystalline Fe (hydr)oxides, exhibits decent catalytic behavior; however, the instability of its amorphous structure limits its engineering applications. Siliceous ferrihydrite (FhSi) was readily synthesized in this study by co-precipitation. The formation of Fe-O-Si linkages did not alter the amorphous state of pure Fh, but increased the surface area (SBET), reduced the point of zero charge (pHZPC), and prevented the leaching of more iron. X-ray diffraction, Mössbauer and pyridine-Fourier transform infrared (FTIR) spectroscopies, and potentiometric titration revealed the presence of silicon-occupied portions of growth sites on the Fh surface, which increased the coordination symmetry around the Fe atom and inhibited the transition of Fh to more stable crystalline Fe (hydr)oxides during repeated use. Meanwhile, the density of surface hydroxyl groups (Ds) and the total acid content of the catalytic system after five cycles of catalytic ozonation were 56.75 % and 63.58 % higher than those of freshly prepared system, thereby benefiting the catalysis of ozone for generating ·OH. In addition, the lower pHZPC of the FhSi/O3 system compared to that of the Fh/O3 system promoted the generation of neutral surface-hydroxyl species on the surface of FhSi, which enabled a decent catalytic performance in alkaline solutions, regardless of the catalytic cycle. Moreover, the removal of humic acids (HA) followed a hydroxy radical reaction, which involved self-decomposition (14.15 %), catalytic ozonation (21.58 %), and peroxone and Fenton-like reactions (64.27 %).

Oxygen-containing groups and P doped porous carbon nitride nanosheets towards enhanced photocatalytic activity.

Metal-free polymer graphite carbon nitride (CN) is a promising photocatalyst that has garnered significant research attention. However, unmodified CN possesses several shortcomings such as low specific surface area, poor dispersibility in water, and rapid photogenerated electron-hole recombination, which have severely impacted its mass adoption. Here, this study proposed a two-step heat treatment method to incorporate P dopant and the containing-oxygen groups successively into CN. The final product, denoted as PO-CN, possessed a porous ultrathin nanosheet-like morphology. The introduction of P dopant altered the intrinsic electronic structure of CN. Meanwhile, the presence of oxygen-containing groups improved the dispersibility of PO-CN in water. Also, it led to the formation of a porous ultrathin structure that could provide more active sites. Through the synergistic effects of these two methods, PO-CN demonstrated superior photocatalytic performance compared to the unmodified counterpart. Based on the collective results obtained experimentally and theoretically, PO-CN possessed a porous ultrathin structure, low resistance, and low carrier recombination. The results show an optimal hydrogen evolution rate of PO-CN (997.7 mol h-1 g-1), which was 11.2 times and 3.22 times that of the CN (88.89 mol h-1 g-1) and PCN (310.3 mol h-1 g-1). Moreover, PO-CN was then used in the degradation of Rhodamine B, and a degradation kinetic constant (k) of 0.15009 was calculated, which was 18.42 times and 8.22 times higher as compared to those of CN (0.00815) and PCN (0.01826). Hence, this work provides a new strategy for the alteration of the morphology and electronic structure of CN.

Uracil-Doped Graphitic Carbon Nitride for Enhanced Photocatalytic Performance.

g-C3N4 is a visible-light photocatalyst with a suitable band gap and good stability. Moreover, g-C3N4 is considered to be earth-abundant, which makes it an appealing photocatalyst. However, due to its small specific surface area, low utilization of visible light, and high photogenerated electron-hole pair recombination rate, the photocatalytic activity of g-C3N4 remains unsatisfactory. In this work, a highly efficient nonmetallic photocatalyst, i.e., g-C3N4 doped with uracil (denoted U-C3N4) was successfully developed. Based on the various characterizations and calculations, it is shown that the triazine group in g-C3N4 is replaced with the diazine group in uracil. This occurrence leads to the formation of a new electron-transfer pathway between triazine groups, which can promote the separation of photogenerated electrons and holes. Concurrently, due to the ultrathin structure of the as-prepared U-C3N4, the material possessed a larger specific surface area than pristine g-C3N4, which can provide more active sites. Furthermore, the transfer pathway between the electron and hole was also shortened, and the recombination of the electron and hole was inhibited. According to the results, an optimal hydrogen evolution rate of 31.7 mol h-1 g-1 was achieved by U-C3N4, which is 5.1 times higher as compared to that achieved by pristine g-C3N4 (6.26 mol h-1 g-1). For the photocatalytic degradation of rhodamine B, the reaction rate constant of U-C3N4 (11.3 × 10-2 min-1) is about 5.5 times that of g-C3N4 (2.07 × 10-2 min-1). Furthermore, the uracil-doped catalyst was also able to demonstrate good stability after five successive runs.

Combination of catalytic ozonation by regenerated granular activated carbon (rGAC) and biological activated carbon in the advanced treatment of textile wastewater for reclamation.

Wastewater reclamation in the textile industry has attracted considerable attention. In this study, catalytic ozonation by regenerated granular activated carbon (rGAC) and its combination with biological activated carbon (BAC) was investigated for the reclamation of a real bio-treated dyeing and finishing wastewater (BDFW). Catalytic ozonation by rGAC (O3/rGAC) was 1.6-2.0 times more efficient than ozonation alone for pollutants degradation. Although iron oxide loaded rGAC (rGAC-Fe) improved the performance of catalytic ozonation by 14%-25%, but was labile (<2 days) compared to stable rGAC (>20 days). Catalytic ozonation improved the generation of •OH, contributing 1.1-1.7 times faster of chromophores decomposition and 0.24-0.55 times more increase of biodegradability than ozonation. However, catalytic ozonation increased the acute toxicity of BDFW by two times. The combination of O3/rGAC and BAC can synergistically reduce COD, chromophores, and color in BDFW during 45-day's continuous operation, the improvements than O3/rGAC being 21.0%, 18.8%, and 13.6%, respectively. Moreover, although O3/rGAC of BDFW increased the toxicity from 98.3 to 146.5 µg-HgCl2/L, post BAC significantly reduced the toxicity to 13.1 µg-HgCl2/L. Engineering practice of water reclamation by O3/rGAC-BAC was approved to be feasible based on both the water quality of treated water and the operation cost.

[Performance and Mechanism Study of Visible Light-driven C3N4/BiOBr Composite Photocatalyst].

Efficient visible light-driven C3N4/BiOBr composite photocatalysts were prepared via a facile hydrothermal method and characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, UV-Vis diffuse reflectance spectra and photoluminescence spectra for the phase composition and optical property. Taking rhodamine B (RhB) as the target pollutant, the photocatalytic activity and stability of photocatalysts were studied under visible light irradiation. Furthermore, the mechanism in the process of photocatalytic degradation was discussed by electron spin resonance spectroscopy analysis and the trapping experiment of generated radicals. The results indicated that C3N4/BiOBr composite photocatalysts had excellent crystallization performance. Composited by C3N4, BiOBr exhibited considerably higher photocatalytic activity by reducing the rate of electron-hole recombination. Among prepared composites with various C3N4 contents, 15% C3N4/BiOBr exhibited the best efficiency for the degradation of RhB. After irradiation for 18 minutes, the degradation rate of RhB was 100%, which was 1.5 times higher than that using pure BiOBr. The results also suggested that holes and ·O2- were the main reactive species in the photocatalytic process for the RhB degradation, and holes played the leading role.

[Removal of Antimony from Water by Nano Zero-Valent Iron/Activated Carbon Composites].

Nano zero-valent iron/activated carbon (nZVI/AC) composites were prepared via liquid phase chemical precipitation and then characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and Brunauer-Emmett-Teller theoretical methods for an analysis of the structure, morphology, physical and chemical characteristics of the composites. The effects of the reaction system, nZVI loading, initial pH, and dosage on antimony removal were investigated and the removal mechanisms were discussed. These results indicate that nZVI/AC can be successfully prepared via liquid phase chemical precipitation. In an N2 atmosphere, a dosage of 0.2 g·L-1, 15% nZVI/AC with an initial pH of 7.5 (the pH of raw water) was prepared. After a reaction duration of 2 h, the removal rate of Sb(Ⅴ) had reached 76.2% and the effluent concentration had decreased to only 23.8 µg·L-1. These results show that Fe2+ plays a major mechanistic role in the removal of Sb(Ⅴ) from the system and is the major active substance in the reaction process. In combination with an analysis of elemental Sb on the surface of the nZVI/AC before and after reaction, the removal process relies on the reduction of Fe(0) and Fe2+, Sb(Ⅴ) reducted into Sb(Ⅲ) and through adsorption removal.

Adsorption characteristics of Bisphenol-A on tailored activated carbon in aqueous solutions.

The adsorption behavior of pharmaceuticals and personal care product, Bisphenol-A (BPA), according to four coal-based and four wood-based granular activated carbons modified using outgassing treatment, acidic treatment or alkaline treatment was studied. The adsorption isotherm results indicated that carbon surface acidity played a very important role in the adsorption of BPA. It was found that increasing surface acidity would increase the hydrogen bonding effects and increase adsorption of BPA on activated carbon. The acidic modified sample (F600-A and OLC-A) represented the best adsorption capacity, and the equilibrium adsorption amounts reached 346.42 and 338.55 mg/g, respectively. Further, effects of surface charge and surface basicity were examined. It was found that the adsorbed amount of BPA decreased with the increase of surface charge. Finally, there appeared to be a significant oligomerization phenomenon with BPA molecules onto the surface of activated carbon. OLC and OLC-OG, which have higher micropore percentages, are very effective in hampering the oligomerization of BPA under oxic conditions.

Photodegradation of Orange II using waste paper sludge-derived heterogeneous catalyst in the presence of oxalate under ultraviolet light emitting diode irradiation.

A waste paper sludge-derived heterogeneous catalyst (WPS-Fe-350) was synthesized via a facile method and successfully applied for the degradation of Orange II in the presence of oxalic acid under the illumination of ultraviolet light emitting diode (UV-LED) Powder X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electronic microscopy and N2 sorption isotherm analysis indicated the formation of α-Fe2O3 in the mesoporous nanocomposite. The degradation test showed that WPS-Fe-350 exhibited rapid Orange II (OII) degradation and mineralization in the presence of oxalic acid under the illumination of UV-LED. The effects of pH, oxalic acid concentration and dosage of the catalyst on the degradation of OII were evaluated, respectively. Under the optimal conditions (1g/L catalyst dosage, 2mmol/L oxalic acid and pH3.0), the degradation percentage for a solution containing 30mg/L OII reached 83.4% under illumination by UV-LED for 80min. Moreover, five cyclic tests for OII degradation suggested that WPS-Fe-350 exhibited excellent stability of catalytic activity. Hence, this study provides an alternative environmentally friendly way to reuse waste paper sludge and an effective and economically viable method for degradation of azo dyes and other refractory organic pollutants in water.

Fenton-like degradation of Methylene Blue using paper mill sludge-derived magnetically separable heterogeneous catalyst: Characterization and mechanism.

For the paper industry, the disposal and management of the yielded sludge are a considerable challenge. In our work, the paper mill sludge-derived magnetically separable heterogeneous catalyst (PMS-Fe-380) was prepared easily through a facile synthesis method. The morphology and structure of PMS-Fe-380 were fully characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer-Emmet-Teller analysis. The catalytic activity of PMS-Fe-380 was evaluated by degradation of Methylene Blue (MB). The reusability and stability of PMS-Fe-380 were evaluated in five repeated runs, which suggested that PMS-Fe-380 manifested excellent stability of catalytic activity. Moreover, leaching tests indicated that the leached iron is negligible (<0.5mg/L). This study provides an alternative environmentally friendly reuse method for paper mill sludge and a novel catalyst PMS-Fe-380 that can be considered as a promising heterogeneous Fenton-like catalyst.

Assessment of a novel overflow-type electrochemical membrane bioreactor (EMBR) for wastewater treatment, energy recovery and membrane fouling mitigation.

A novel overflow-type electrochemical membrane bioreactor (EMBR) without ion exchange membrane, was developed for wastewater treatment and utilized electricity recovered by microbial fuel cell (MFC) for membrane fouling mitigation in membrane bioreactor (MBR). The maximum power density of 629mW/m(3) or 7.18mW/m(2) was obtained. The removal efficiencies of chemical oxygen demand, ammonia nitrogen and total nitrogen under appropriate ranges of hydraulic retention times (16.9-8.5h) were 92.6±5.4%, 96.5±2.8% and 73.9±9.7%, respectively. Sequencing showed electrochemically active bacteria Lactococcus, Bacillus and Saprospiraceae_uncultured were abundant in the biofilm. Compared with a conventional MBR, five significant effects of the MFC integration on the sludge properties, including particle zeta potential decrease, particle size distribution macroaggregation, soluble microbial products and extracellular polymeric substances reduction and SMPP/SMPC ratio increase, were achieved in this system, leading to membrane fouling mitigation. This system shows great promise for practical wastewater treatment application.

Paddy field--a natural sequential anaerobic-aerobic bioreactor for polychlorinated biphenyls transformation.

The environmental pollution and health risks caused by the improper disposal of electric and electronic waste (e-waste) have become urgent issues for the developing countries. One of the typical pollutants, polychlorinated biphenyls (PCBs), is commonly found in farmland in Taizhou, a major hotspot of e-waste recycling in China. This study investigated the amount of PCB residue in local farmlands. Biotransformation of PCBs was further studied under different water management conditions in paddy field with or without rice cultivation, with a special focus on the alternating flooded and drying processes. It was found that paddy field improved the attenuation of PCBs, especially for highly chlorinated congeners. In the microcosm experiment, 40% or more of the initial total PCBs was removed after sequential flood-drying treatments, compared to less than 10% in the sterilized control and 20% in the constant-drying system. Variation in the quantity of PCBs degrading and dechlorinating bacterial groups were closely related to the alteration of anaerobic-aerobic conditions. These results suggested that alternating anoxic-oxic environment in paddy field led to the sequential aerobic-anaerobic transformation of PCBs, which provided a favorable environment for natural PCB attenuation.

Study on US/O3 mechanism in p-chlorophenol decomposition.

Study on the effects of sonolysis, ozonolysis and US/O3 system on the decomposition of p-chlorophenol in aqueous solutions indicated that in the cases of US/O3 system, individual ozonolysis and sonolysis, the decomposition rate of p-chlorophenol reached 78.78%, 56.20%, 2.79% after a 16-min reaction while its CODcr (chemical oxygen demand) removal rate was 97.02%, 62.17%, 3.67% after a 120-min reaction. The decomposition reaction of p-chlorophenol follows pseudo-first-order kinetics. The enhancement factors of p-chlorophenol and its COD(cr) under US/O3 system reached 63% and 237% respectively. The main intermediates during the decomposition include catechol, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid. The decomposition mechanism of p-chlorophenol was also discussed.

Ozonation with ultrasonic enhancement of p-nitrophenol wastewater.

Synergetic effects for p-nitrophenol degradation were observed in the ozonation with ultrasonic enhancement. The enhancements of removal rate for p-nitrophenol and TOC were around 116% and 294% respectively in comparison with the individual ultrasound and ozonation systems. The synergetic phenomenon is attributed to two physicochemical mechanisms: (1) Ultrasound decomposes ozone causing augmentation of the activity of free radicals; (2) Ultrasonic wave increased the concentration of O(3) in solution because of ultrasonic dispersion.

Mechanistic study of ozonation of p-nitrophenol in aqueous solution.

Ozonlysis in the treatment of p-nitrophenol solution was studied in this paper. The results indicated that the decomposition of p-nitrophenol was accelerated as the gas flow rate or pH value increased. When gaseous ozone concentration was 20.11 mg/L and pH was 3, after 24 min reaction, the removal rate of p-nitrophenol reached 73.04%, 86.11%, 91.71% and 95% at the gas flow rate of 32, 40, 48 and 56 ml/min respectively. And when pH was 3, 4, 5, 6, the decomposition rate was 66.38%, 82.09%, 90.46%, 97.50% after a 20 min reaction respectively. It was mainly O3 molecule that took part in the decomposition when pH was 3. The main intermediates during the decomposition include catechol, o-benzoquinone, hydroquinone, p-benzoquinone, phenol, fumaric acid, maleic acid, oxalic acid and formic acid. The decomposition mechanism of p-nitrophenol was also discussed.