Activation of Peracetic Acid with CuFe2O4 for Rhodamine B Degradation: Activation by Cu and the Contribution of Acetylperoxyl Radicals.

Advanced oxidation processes (AOPs) demonstrate great micropollutant degradation efficiency. In this study, CuFe2O4 was successfully used to activate peracetic acid (PAA) to remove Rhodamine B. Acetyl(per)oxyl radicals were the dominant species in this novel system. The addition of 2,4-hexadiene (2,4-HD) and Methanol (MeOH) significantly inhibited the degradation efficiency of Rhodamine B. The ≡Cu2+/≡Cu+ redox cycle dominated PAA activation, thereby producing organic radicals (R-O˙) including CH3C(O)O˙ and CH3C(O)OO˙, which accounted for the degradation of Rhodamine B. Increasing either the concentration of CuFe2O4 (0-100 mg/L) or PAA (10-100 mg/L) promoted the removal efficiency of this potent system. In addition, weakly acid to weakly alkali pH conditions (6-8) were suitable for pollutant removal. The addition of Humid acid (HA), HCO3-, and a small amount of Cl- (10-100 mmol·L-1) slightly inhibited the degradation of Rhodamine B. However, degradation was accelerated by the inclusion of high concentrations (200 mmol·L-1) of Cl-. After four iterations of catalyst recycling, the degradation efficiency remained stable and no additional functional group characteristic peaks were observed. Taking into consideration the reaction conditions, interfering substances, system stability, and pollutant-removal efficiency, the CuFe2O4/PAA system demonstrated great potential for the degradation of Rhodamine B.

Enhanced nitrogen removal in the treatment of rural domestic sewage using vertical-flow multi-soil-layering systems: Experimental and modeling insights.

Domestic sewage in rural areas is often poorly treated and discharged into waters, resulting in negative impacts on regional environment, natural resources and human health. A cost-efficient decentralized sewage treatment technology is sustainably necessary for rural areas. In this study, a modified multi-soil-layering (MSL) system was developed to specifically treat low C/N ratio domestic sewage in rural areas. The results proved the good performance of MSLs in sewage treatment under complex conditions. The highest degradation rates of COD, TP, NH4+-N, NO3--N, TN among all the devices could reach 98.29%, 100%, 76.60%, 96.15% and 69.86%, respectively. During the operation, MSL5 and MSL6 showed the best overall performance of contaminant removal. The effects of single factors and their interactions on the performance of MSL systems were further revealed through factorial analyses. In order to simulate and predict nitrogen removal of MSL system, a statistical relationship between TN removal rate and operation parameters was also successfully developed based on stepwise cluster analysis. Such modeling of nitrogen removal model can help develop an optimal strategy for the operation of MSL in treating low C/N ratio sewage from rural areas.

Effects of light quality on microalgae cultivation: bibliometric analysis, mini-review, and regulation approaches.

The ever-increasing concern for energy shortages and greenhouse effect has triggered the development of sustainable green technologies. Microalgae have received more attention due to the characteristics of biofuel production and CO2 fixation. From the perspective of autotrophic growth, the optimization of light quality has the potential to promote biomass production and bio-component accumulation in microalgae at low cost. In this study, bibliometric analysis was used to describe the basic features, identify the hotspots, and predict future trends of the research related to the light quality on microalgae cultivation. In addition, a mini-review referring to regulation methods of light quality was provided to optimize the framework of research. Results demonstrated that China has the greatest interest in this area. The destination of most research was to obtain biofuels and high-value-added products. Both blue and red lights were identified as the crucial spectrums for microalgae cultivation. However, sunlight is the most affordable light resource, which could not be fully utilized by microalgae through the photosynthetic process. Hence, some regulation approaches (e.g., dyes, plasmonic scattering, and carbon-based quantum dots) are proposed to increase the proportion of beneficial spectrum for enhancement of photosynthetic efficiency. In summary, this review introduces state-of-the-art research and provides theoretical guidance for light quality optimization in microalgae cultivation to obtain more benefits.

A biophysiological perspective on enhanced nitrate removal from decentralized domestic sewage using gravitational-flow multi-soil-layering systems.

Multi-soil-layering (MSL) system with brick-wall pattern structure and gravitational flow can be used for decentralized rural domestic sewage treatment. The capability of soil for contaminant removal is maximized within soil mixture blocks (SMBs). However, the performance of removing nitrate was still not ideal during operation. To improve its performance in MSL system, the relationship between biophysiological characteristics of denitrifying species and operating conditions was studied. Microbial species diversity of activated sludge and soil samples were analyzed. The significant effects of independent factors and their interactions on microbial species diversity and denitrifying species abundance were revealed on the basis of factorial analysis. The results indicated activated sludge in SMBs played a key role in increasing the richness of denitrifying species in MSL system. Slow-release poly (butylene succinate) (PBS) had the most dominant positive effect on increasing denitrifying species abundance. Submersion had significantly positive effect on species richness in SMBs. These three factors, including activated sludge, PBS in SMBs, and submersion condition had different significant effects on microbial responses. They were favorable for denitrification and ensuring a better removal efficiency of nitrate and total nitrogen. The porous zeolites were served as the habitats for most of aerobic bacteria to form biofilms, which could promote the oxygen consumption in both sewage and system to improve denitrification in SMBs. The results could help on the enhancement of denitrification in MSL system from biophysiological insights. It can provide a sound strategy for using MSL system with great performance on contaminant removal.