Approaches for Enhancing Wastewater Treatment of Photocatalytic Fuel Cells: A Review.

Environmental pollution and energy crises have garnered global attention. The substantial discharge of organic waste into water bodies has led to profound environmental contamination. Photocatalytic fuel cells (PFCs) enabling the simultaneous removal of refractory contaminants and recovery of the chemical energy contained in organic pollutants provides a potential strategy to solve environmental issues and the energy crisis. This review will discuss the fundamentals, working principle, and configuration development of PFCs and photocatalytic microbial fuel cells (PMFCs). We particularly focus on the strategies for improving the wastewater treatment performance of PFCs/PMFCs in terms of coupled advanced oxidation processes, the rational design of high-efficiency electrodes, and the strengthening of the mass transfer process. The significant potential of PFCs/PMFCs in various fields is further discussed in detail. This review is intended to provide some guidance for the better implementation and widespread adoption of PFC wastewater treatment technologies.

Construction and regulation of high active sites in montmorillonite composite catalyst for the removal of ofloxacin via persulfate activation.

In this study, ionic liquids (ILs) were used as organic modifiers by introducing montmorillonite nanolayers containing potential C and N active sites between the montmorillonite nanolayers. Organically modified montmorillonite (ILs-Mt-p) was further prepared by high-temperature pyrolysis under N2 and used for the removal of ofloxacin (OFL) by activated peroxymonosulfate (PMS). Combined with XPS and other characterization analyses, it was found that the catalyst materials prepared from different organic modifiers had similar surface functional groups and graphitized structures, but contained differences in the types and numbers of C and N active sites. The catalyst (3CPC-Mt-p) obtained after pyrolysis of montmorillonite modified with cetylpyridinium chloride (CPC) had optimal catalytic performance, in which graphitic C, graphitic N, and carbonyl group (C[bond, double bond]O) could synergistically promote the activation of PMS by electron transfer, and 77.3 % of OFL could be removed within 60 min. The effects of OFL concentration, initial pH, and anions on the effects of OFL removal by the 3CPC-Mt-p/PMS system were further investigated. Satisfactory degradation results were obtained over a wide pH range. Cl- promoted the system to degrade OFL, while the presence of SO42-, H2PO4- and HA showed some inhibition, but overall the 3CPC-Mt-p catalysts had a strong anti-interference ability, showing good application prospects. The quenching experiments and EPR tests showed that O2-- and 1O2 in the 3CPC-Mt-p/PMS system were the main reactive oxygen species for the degradation of OFL, and •OH was also involved in the reaction. This study provides ideas for the construction and modulation of active sites in mineral materials such as montmorillonite and broadens the application of montmorillonite composite catalysts in advanced oxidation processes for the treatment of antibiotic wastewater.

Integration of a pure moving bed biofilm reactor process into a large micro-polluted water treatment plant.

The pure-MBBR process was applied to remove ammonia in a full-scale micro-polluted-water treatment plant with a daily treatment capacity of 260 × 104 m3/d, Guangdong, China. The relationship between treatment efficiency, physical and chemical properties and microbial diversity in the process of biofilm growth was explored, and the oxygen transfer model of biofilm was established. The results show that the effluent of two-stage pure MBBR process is stable and up to standard after 10 days' incubation. The nitrification loads of two-stage biofilm was stable on the 14th day. The biomass and biofilm thickness lagged behind the nitrification load, and reached a relatively stable level on the 28th day. The species richness of biofilm basically reached a stable level on the 21st day, and the microbial diversity of primary biofilm was higher. In the primary and secondary stage at different periods, the relative abundance of dominant nitrifying bacteria Nitrospira reaches 8.48-13.60%, 6.48-9.27%, and Nitrosomonas reaches 2.89-5.64%, 0.00-3.48%. The pure MBBR system mainly adopts perforated aeration. Through the cutting and blocking of bubbles by suspended carriers, the oxygen transfer rate of the system was greatly improved.

Comparative study of pyrolytic carbons prepared from printed circuit boards by magnetic and electrostatic separation.

Physical technology is the main method to separate metal and non-metallic fractions from printed circuit boards (PCBs). The non-metallic fractions from magnetic and electrostatic separation have different ingredients, which enables them to be prepared into pyrolytic carbon with different properties. To discover the influence of separation technologies for PCBs on the preparation, characterization and application of pyrolytic carbon, two kinds of nonmetal fraction from magnetic and electrostatic separation were chosen as the precursors of pyrolytic carbon. The thermogravimetric analysis of non-magnetic fraction and non-conductive fraction at different heating rates was discussed in the paper. The optimal heating rate of 10 °C min-1 was applied in preparing pyrolytic carbons. Pyrolytic carbons prepared from the non-magnetic fraction and non-conductive fraction had visible differences in their morphological and pore structures. Pyrolytic carbons of the non-magnetic fraction exhibited higher BET surface area (313 m2 g-1) and higher adsorption capacities for ciprofloxacin (142.82 mg g-1) than those of pyrolytic carbon of the non-conductive fraction (S BET: 235 m2 g-1, q m: 78.17 mg g-1). Equilibrium data fit better to the Freundlich model than the Langmuir model. According to the calculated thermodynamic parameters, CIP adsorption processes by the two pyrolytic carbons were spontaneous and endothermic. Although the metal recovery from PCBs through electrostatic separation is higher, pyrolytic carbon prepared from the non-magnetic fraction shows better pore characteristics and adsorption properties. This paper might be the first report of the effect of separation technology for PCBs on the preparation of pyrolytic carbons. This paper contributed to the reutilization of non-metallic fractions of PCBs and the development of a cyclic economy.

[Microbial Diversity Analysis of WWTPs Based on Hybrid-MBBR Process in a Low Temperature Season in the Yangtze River Delta].

The aim of this study was to characterize the changes of the microbial community in WWTPs based on hybrid-MBBR process in the Yangtze River Delta in a low temperature season, and to obtain the regularity of the microbial distribution. High-throughput sequencing of Illumina miSeq was conducted to analyze the microbial community structure of activated sludge and suspended carrier biofilm in the aerobic area of five WWTPs. The results showed that the number of microbial species in the suspended carrier biofilm was lower than that of the activated sludge in the same plant, and the species distribution was more uneven. The addition of a suspended carrier can improve the microbial diversity of the system, while the influent and operation mode have a certain selectivity to the microbial community composition of the system. The bacteria with high relative abundance in each plant primarily included Nitrospira, Mycobacterium, Defluvicoccus, Hyphomacrobium, and Macrocharacters,etc. The addition of suspended carriers significantly enhanced the enrichment of Nitrospira. The amount of nitrifying bacteria in the suspended carrier accounted for 86.12%-95.36% of that of the whole system. A certain relative abundance of denitrifying bacteria was detected in the suspended carrier in the aerobic area of each plant. Combined with the results of the measurement of water quality along the process and the lab-scale experiment, it was confirmed that significant SND occurred on the suspended carrier biofilm in the aerobic area, which enhanced the TN removal of the system.

Research on adsorption of Cr(â ¥) by Poly-epichlorohydrin-dimethylamine (EPIDMA) modified weakly basic anion exchange resin D301.

A novel composite, EPIDMA/D301, with high adsorption capacity and particular affinity toward Cr(Ⅵ) was well prepared utilizing cationic polyelectrolyte poly-epichlorohydrin-dimethylamine (EPIDMA) impregnated in the networking pores of the styrene macroporous weak basic anion exchange resin D301. The physicochemical characteristics of EPIDMA/D301 were characterized by the Brunauer-Emmett-Teller (BET), zeta potential, FTIR, SEM-Mapping and XPS. The adsorption properties were researched via the influence of the concentration of EPIDMA, adsorbent dose, pH, the initial concentration of Cr(Ⅵ) solution, contact time and temperature. Results presented that the weakly basic anion exchange resin supported cationic polymer showed the excellent potential of removing Cr(VI) ions primarily due to the nonspecific Cr(VI) adsorption resulted from the polymeric host D301, the electrostatic attraction of amino groups fixed on the D301 matrix and the embedded EPIDMA with Cr(VI) ions and the ion exchange by the displacement of Cl- mainly derived from EPIDMA with Cr(VI) ions. The kinetic data were best fitted by the pseudo-second-order kinetic model. The batch equilibrium data followed Langmuir isotherm model well with the maximum adsorption capacity of 194 mg g-1 at 25 °C, which demonstrated that the styrene anion exchange resin modified with EPIDMA might be an efficient approach to eliminate potentially toxic metals.

Preparation of green alga-based activated carbon with lower impregnation ratio and less activation time by potassium tartrate for adsorption of chloramphenicol.

Potassium tartrate (C4H6K2O7) was utilized as a novel activating agent to prepare activated carbon with relatively high specific surface area by using less activating agent and activation time from marine waste-green alga (Enteromorpha prolifera) for the first time. The influences of activation temperature, impregnation ratio and activation time on the pore structure were investigated to obtain the optimum conditions (activation temperature: 700°C, impregnation ratio: 1:1, and activation time: 30min). Meanwhile, the activation temperature was evaluated to be the essential factor that dominated the form of pore structure in activated carbon. The green alga-based activated carbon that was prepared under optimum conditions has shown the high surface area of 1692m2/g and total pore volume of 1.22cm3/g, which could be used as an effective adsorbent to remove chloramphenicol. The thermodynamic data of chloramphenicol were well fitted by Langmuir isotherm model and the green alga-based activated carbon has showed high adsorption capacity of 709.2mg/g towards chloramphenicol.