Pilot-scale and large-scale Fenton-like applications with nano-metal catalysts: From catalytic modules to scale-up applications.

Recently, great efforts have been made to advance the pilot-scale and engineering-scale applications of Fenton-like processes using various nano-metal catalysts (including nanosized metal-based catalysts, smaller nanocluster catalysts, and single-atom catalysts, etc.). This step is essential to facilitate the practical applications of advanced oxidation processes (AOPs) for these highly active nano-metal catalysts. Before large-scale implementation, these nano-metal catalysts must be converted into the effective catalyst modules (such as catalytic membranes, fluidized beds, or polypropylene sphere suspension systems), as it is not feasible to use suspended powder catalysts for large-scale treatment. Therefore, the pilot-scale and engineering applications of nano-metal catalysts in Fenton-like systems in recent years is exciting. In addition, the combination of life cycle assessment (LCA) and techno-economic analysis (TEA) can provide a useful support tool for engineering scale Fenton-like applications. This paper summarizes the designs and fabrications of various advanced modules based on nano-metal catalysts, analyzes the advantages and disadvantages of these catalytic modules, and further discusses their Fenton-like pilot scale or engineering applications. Concepts of future Fenton-like engineering applications of nano-metal catalysts were also discussed. In addition, current challenges and future expectations in pilot-scale or engineering applications are assessed in conjunction with LCA and TEA. These challenges require further technological advances to enable larger scale engineering applications in the future. The aim of these efforts is to increase the potential of nanoscale AOPs for practical wastewater treatment.

Acclimation of electroactive biofilms under different operating conditions: comprehensive analysis from architecture, composition, and metabolic activity.

Electroactive biofilms (EABs) have aroused wide concern in waste treatment due to their unique capability of extracellular electron transfer with solid materials. The combined effect of different operating conditions on the formation, microbial architecture, composition, and metabolic activity of EABs is still unknown. In this study, the impact of three different factors (anode electrode, substrate concentration, and resistance) on the acclimation and performance of EABs was investigated. The results showed that the shortest start-up time of 127.3 h and highest power density of 0.84 W m-2 were obtained with carbon brush as electrode, low concentration of substrate (1.0 g L-1), and 1000 Ω external resistance (denoted as N1). The EABs under N1 condition also represented strongest redox capacity, lowest internal resistance, and close arrangement of bacteria. Moreover, the EABs cultured under different conditions both showed similar results, with direct electron transfer (DET) dominated from EABs to anode. Microbial community compositions indicated that EABs under N1 condition have lowest diversity and highest abundance of electroactive bacteria (46.68%). Higher substrate concentration (3.0 g L-1) promoted the proliferation of some other bacteria without electroactivity, which was adverse to EABs. The metabolic analysis showed the difference of genes related to electron transfer (cytochrome C and pili) and biofilm formation (xap) of EABs under different conditions, which further demonstrated the higher electroactivity of EABs under N1. These results provided a comprehensive understanding of the effect of different operating conditions on EABs including biofilm formation and electrochemical activity.

[Chemical Species of PM2.5 in the Urban Area of Beijing].

From August 2012 to July 2013, 220 groups of PM2.5 samples were continuously collected at four locations in the urban area of Beijing (Shijingshan, Chegongzhuang, Dongsi, and Tongzhou), and the primary chemical species of PM2.5 were analysed by the chemical mass balance method. It was found that the mass of PM2.5 obtained from chemical mass balance method agreed well with the value from gravimetric measurement, with a good correlation of 0. 95 in spring, autumn, and winter. However, the correlation seasonally changed in summer, with a relatively lower correlation coefficient of 0. 77. The concentrations of OM, EC, SO(4)2-, NO3-, NH4+, Cl-, crustal matter, and trace species were 31. 4, 3. 8, 19. 9, 21. 6, 14. 4, 4. 0, 15. 4, and 2. 9 µg.m-3, which accounted for 25. 1%, 3. 0% , 15. 9%, 17. 2%, 11. 5%, 3. 2%, 12. 3%, and 2. 3% of PM2, , respectively. Besides crustal matter, concentrations of the primary chemical species in PM2.5 from the west to the east gradually increased. The most serious PM pollution occurred between 11 and 14 February 2013, during which concentrations of OM, SO2-, NO3-, NH4+ were 1. 9, 5. 0, 3.2 and 4. 2 times as high as the annual average. SO(4)2- was recognized as the most important species for the pollution in the process. OM was the largest component of urban PM2.5 during both heating and non-heating periods. Comparing to non-heating period, the concentrations of OM, NH4+, NO3-, and SO(4)2- all increased during the heating period, except for the component of crust and EC. The biggest difference between the two periods was the component of Cl- (4. 4 fold), which can be attributed to the burning of coal. For unknown components, the main component was moisture, which accounted for about 6.0% in urban PM2.5. The highest moisture appeared in summer (6. 5%), followed by spring and winter, and the least appeared in fall (3. 7% ).