Construction of 2D/3D g-C3N4/BiOI Photocatalysts with p-n Heterojunction and Their Performance in Photocatalytic Degradation of Amaranth Dye.

The g-C3N4 (graphitic carbon nitride)/BiOI (bismuth oxyiodide) photocatalysts, boasting a unique nanomicrosphere architecture, were synthesized through a tripartite process involving heat polycondensation, hydrothermal treatment, and hybrid methods, using melamine, bismuth nitrate, and potassium iodide as starting materials. The photocatalyst was comprehensively characterized and analyzed while its efficacy in photocatalytic degradation of amaranth (AR) under various lighting conditions was investigated, and the catalytic mechanism was determined by kinetic analysis and free radical scavenging experiments. The results showed that g-C3N4 formed a strong bond with BiOI. The resulting composite catalyst retains the inherent 2D lamellar structure of g-C3N4, as well as the 3D microsphere structure of BiOI, thereby creating heterojunctions via p-n interactions. Under visible light exposure, g-C3N4/BiOI-15% demonstrated optimal catalytic performance, achieving a degradation rate of 74.64% for AR and exhibiting the highest rate constant. Radical tests confirmed that -O2- (superoxide anion) plays a crucial role as active species in the photocatalytic reaction.

Preparation of Au-RGO/TiO2 nanotubes and study on the photocatalytic degradation of ciprofloxacin.

Au-RGO/TiO2 nanotubes were prepared by anodic oxidation and electrochemical deposition, and their performance in the photocatalytic degradation of ciprofloxacin was investigated. The results showed that, compared with TiO2 nanotubes and RGO/TiO2 nanotubes, the Au-RGO/TiO2 nanotubes had the highest ciprofloxacin degradation rate, reaching 96.93% in 180 min of photocatalysis. In addition, the possible degradation products of ciprofloxacin were analyzed by liquid chromatography-mass spectrometry, and the mechanism of degradation of ciprofloxacin by Au-RGO/TiO2 nanotubes was analyzed.

Impact of salinity on anaerobic microbial community structure in high organic loading purified terephthalic acid wastewater treatment system.

To investigate the effect of salinity (1% sodium chloride) on anaerobic microbial community structure in high strength telephthalic wastewater treatment system, the performances of anaerobic-aerobic process and the shifts of microbial community in anaerobic tank were studied and determined. Results showed that the chemical oxygen demand (COD) removal in the whole process remained above 90%. And the effluent concentrations of targeted pollutants were lower than 10 mg/L, other than para-toluic acid (PT, 38.09 mg/L). However, methane production significantly decreased compared to no salinity situation. This might be due to the inhibition of salinity on methanogens, which hindered the conversion of acetate to methane. Furthermore, the dominant genus in bacterial level changed from Tepidisphaera to Syntrophus, which facilitated the syntrophic association with hydrogenotrophic methanogens. The prevailed archaea remained acetoclastic Methanothrix above 90%. Therefore, the salinity on anaerobic microbial community structure mainly reflects in the methanogen process, remarkably decreasing methane production.

Effects of tourmaline on nitrogen removal performance and biofilm structures in the sequencing batch biofilm reactor.

The effects of tourmaline on nitrogen removal performance and biofilm structures were comparatively investigated in two identical laboratory-scale sequencing batch biofilm reactors (SBBRs) (denoted SBBR1 and SBBR2) at different nitrogen loading rates (NLRs) varying from (0.24±0.01) to (1.26±0.02) g N/(L·day). SBBR1 was operated in parallel with SBBR2, but SBBR1 was filled with polyurethane foam loaded tourmaline (TPU) carriers and another (SBBR2) filled with polyurethane foam (PU) carriers. Results obtained from this study showed that the excellent and stable performance of SBBR1 was obtained. Ammonia nitrogen removal and total nitrogen removal were higher in SBBR1 than that in SBBR2 with increase of NLR. At an NLR of (0.24±0.01) g N/(L·day), the majority of the spherical and elliptical bacteria were surrounded by the extracellular polymeric substance (EPS) and bacillus or filamentous bacteria in two SBBRs biofilms. When NLR increased to (1.26±0.02) g N/(L·day), the clusters were more obvious in the SBBR1 biofilm than that in the SBBR2 biofilm. Bacteria in SBBR1 were inclined to synthesis more EPS, and the formed EPS could protect the bacteria from free ammonia (FA) under extreme condition NLR (1.26±0.02) g N/(L·day). The results of polymerase chain reaction-denaturing gradient gel electrophoresis analysis showed that the microbial community similarity in SBBR2 decreased more obviously than that in SBBR1 with the increase of NLR, which the microbial community in SBBR1 was relatively stable.

[Realization of short cut nitrification under the limited filamentous sludge bulking condition].

In order to realize the combination of "low oxygen limited filamentous sludge bulking" and short cut nitrification,the startup method of short cut nitrification and the maintenance strategies of sludge settleability were investigated under limited filamentous sludge bulking condition by using sequencing batch reactor (SBR). The effects of environmental factors like water quality, pH, DO,temperature and operation methods like mixture flow pattern, aeration mode, influent pattern on sludge settleability were analyzed. The results show that, when pH is between 7.2 and 8.0 and temperature is between 20 degrees C and 25 degrees C, short cut nitrification can be gradually realized through maintaining low DO and controlling the aeration time accurately. Nitrite accumulating ratio can increase from 28% to 80% after operating 160 cycles. Sludge settleability can be maintained effectively by changing the influent volume exchanging ratio (VER) assisted by aeration rate .The sludge volume index (SVI) can be maintained around 150 mL/g by adjusting the VER from 0.25 to 0.33 under limited sludge bulking. At the end of the aerobic phase, dissolved total nitrogen concentration increase slightly.

[Study on the technology of treating low temperature and low turbidity water by membrane bioreactor].

For the purpose of solving the problem of low temperature and low turbidity water treatment, a pilot study was made on the treatment of Songhuajiang River raw water with low temperature and low turbidity by using membrane bioreactor (MBR) process, and the removal effects of organic pollutants and turbidity and membrane filtration period were also investigated. The results showed that the effluent turbidity was lower than 1 NTU and its removal efficiency was over 90%. The removal efficiency of permanganate index and UV254 were about 40% - 50% and 30% - 45%, respectively. The operation time of the MBR was as long as 60 - 70 hours. Adding powder activated carbon (PAC) has increased the organic pollutant removal efficiency but it has no significant influence on the membrane permeability. Therefore, the MBR was capable of effectively treating waters typically used for drinking water supplies, particularly when the low temperature and low turbidity water are treated. The effluent water quality of MBR was better than that of conventional process. PAC-MBR combined process can be used to enhance organic pollutants removal efficiency when raw water was polluted severely.

Study of removal effect on Mesocyclops leukarti with oxidants.

Cyclops of zooplankton propagates prolifically in eutrophic waterbody and it cannot be exterminated by conventional disinfection process. The mutagenicity of Mesocyclops leukarti and its extermination with oxidants in a drinking waterworks in China were studied. Among five oxidants for use in bench-scale, chlorine dioxide is the most effective and the potassium permanganate is the weakest against Mesocyclops leukarti under the same conditions. Full-scale results showed that Mesocyclops leukarti could be effectively removed from water by 1.0 mg/L chlorine dioxide preoxidation combined with conventional removal physical process. After filtration, chlorite, a by-product of prechlorine dioxide, is stable at 0.45 mg/L, which is lower than the critical value of the USEPA. GC-MS examination and Ames test further showed that the quantity of organic substance and the mutagenicity in water treated by chlorine dioxide preoxidation are obviously less than those of prechlorination.

Removal effect on Mesocyclops leukarti and mutagenicity with chlorine dioxide.

Mesocyclops leukurti of zooplankton propagates excessively in eutrophic water body and it cannot be effectively inactivated by the conventional drinking water treatment process. In order to tackle this problem, a study of removal effect on Mesocyclops leukarti with chlorine dioxide in a waterworks was performed. The results showed that Mesocyclops leukarti could be effectively removed from water by 1.0 mg/L chlorine dioxide preoxidation combined with the conventional drinking water treatment process. Higher oxidizability and molecular state of chlorine dioxide in water is the key to the inactivation of Mesocyclops leukarti. The chlorite, disinfection by-products (DBPs) of chlorine dioxide, was stable at 0.45 mg/L, which is lower than that critical value of the USEPA. GC-MS examination showed that the quantity of organic substance in the water treated by chlorine dioxide obviously decreased. Ames test further revealed that the mutagenicity was reduced by chlorine dioxide with respect to prechlorine. The propagation of Mesocyclops leukarti can be inactivated effectively and safely by chlorine dioxide pre-oxidation.