Nitrophenols are toxic substances that present humans and animals with the risk of deformities, mutations, or cancer when ingested or inhaled. Traditional water treatment technologies have high costs and low p-nitrophenol (PNP) removal efficiency. Therefore, an ultraviolet (UV)-activated granular activated carbon supported nano-zero-valent-iron-cobalt (Co-nZVI/GAC) activated persulfate (PS) system was constructed to efficiently degrade PNP with Co-nZVI/GAC dosage, PS concentration, UV power, and pH as dependent variables and PNP removal rate as response values. A mathematical model between the factors and response values was developed using a central composite design (CCD) model. The model-fitting results showed that the PNP degradation rate was 96.7%, close to the predicted value of 98.05 when validation tests were performed under Co-nZVI/GAC injection conditions of 0.827 g/L, PS concentration of 3.811 mmol/L, UV power of 39.496 W, and pH of 2.838. This study demonstrates the feasibility of the response surface methodology for optimizing the UV-activated Co-nZVI/GAC-activated PS degradation of PNP.

A highly efficient, denitrifying and phosphorus-accumulating bacterial strain was isolated from the Xuzhou Water Operation Co., Ltd, sewage treatment plant. The strain contains ploy-P and PHB granules. It was identified as a Klebsiella sp. using 16S rDNA sequencing and physiological and biochemical analyses, and named as Klebsiella sp. N14. The growth of the strain and its capability of nutrient removal were affected by pH, temperature, and the carbon source. The optimal pH for growth and nutrient removal was 8, and the optimal temperature was 30°C. Sodium acetate was identified as the best carbon source. The phosphorus ( -P) concentration in the culture supernatant resulting from aerobic training of N14 in synthetic wastewater for 24 h decreased from 81 to 12.4 mg/L. The phosphorus removal rate was 84.69%. The nitrate ( -N) concentration decreased from 180 to 15 mg/L. The nitrite ( -N) concentration decreased from 44 to 6.7 mg/L. The denitrification rate was 87.94%. This study describes a novel denitrifying, phosphorus-accumulating bacterial strain, and the optimal conditions for nitrogen and phosphorus removal by this strain.

Hydrogen production through water splitting is a promising path to develop renewable green energy. Effective, stable, and low-cost catalysts are the key to water splitting. In the present work, a series of self-supporting nanoporous alloys are prepared by using a dealloying process followed by electrooxidation. Among them, the np-AlFeNiO-4s sample exhibits remarkable activity (10 mA cm⁻² at 32 mV for the HER and 278 mV for the OER) and good long-term stability (100 h) in alkaline conditions for both the HER and the OER. It only requires 1.56 V to reach 10 mA cm⁻² current density for total water splitting performance. The very short time of electrooxidation can significantly improve the HER performance. Electrooxidation makes the metal and metal oxide sites on the electrode surface effectively coupled, which greatly enhances the kinetic rate of the Volmer and Heyrovsky steps. Appropriate electrooxidation is a rapid and easy way to improve the activity of the electrocatalyst, which has a broad application prospect in electrochemical water splitting.

Pure TiO₂ and N-doped nano-TiO₂ photo catalysts were individually prepared following the sol-gel method under ultrasonic conditions. The photo catalytic decomposition of methyl orange (MO) solution under ultraviolet and visible light irradiation was used as a probe reaction to estimate their photo catalytic activities. The particle size, crystal structure, and optical properties of the prepared TiO₂ were performed by X-ray diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results suggest that ultrasound significantly reduced the size of the TiO₂ particles, improved particle dispersion, which in turn improve the photo catalytic activity of TiO₂ under ultraviolet light. Ultrasound also promoted the doping of non-metal nitrogen and markedly enhanced the visible light absorption capacity of the N-doped nano-TiO₂. Compared with pure TiO₂, the degradation rate for MO under visible light of U-N-TiO₂ was increased by 70%.

Nitrogen-doped titania (TiO₂) photocatalysts were prepared by sol-gel process coupled with ultrasonic irradiation at room temperature. The photocatalytic decomposition of methyl orange (MO) solution under ultraviolet and visible light irradiation was used as a probe reaction to estimate their photocatalytic activities. The physico-chemical properties of the samples were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). A more uniform nanoparticle dispersion, marginally higher surface area, smaller grain size, and higher phase purity are some advantages of preparing TiO₂ by the ultrasonic technique. The nitrogen-doped titania prepared by ultrasonic technique were more effective than the samples prepared by conventional stirring method. Its UV–Vis diffuse reflectance spectra was red shifted compared to the un-doped sample and it showed high decomposition of MO under ultraviolet as well as visible light irradiation.