Accelerating FeIII-Aqua Complex Reduction in an Efficient Solid-Liquid-Interfacial Fenton Reaction over the Mn-CNH Co-catalyst at Near-Neutral pH.

The sluggish regeneration rate of FeII and low operating pH still restrict the wider application of classical Fenton process (FeII/H2O2) for practical water treatment. To overcome these challenges, we exploit the Mn-CNH co-catalyst to construct a solid-liquid interfacial Fenton reaction and accelerate the FeIII/FeII redox cycle at the interface for sustainably generating •OH from H2O2 activation. The Mn-CNH co-catalyst exhibits an excellent regeneration rate of FeII (∼65%) and a high tetracycline removal rate (Kobs) of 0.0541 min-1, which is 19.0 times higher than that of the FeII/H2O2 system (0.0027 min-1) at a near-neutral pH (pH ≈ 5.8), and it also attains 100% degradation of sulfamethoxazole, rhodamine B, and methyl orange. The cyclic mechanism of FeIII/FeII is further elucidated in an atomic scale by combining characterizations and density functional theory calculations, including FeaqIII specific adsorption and the electron-transfer process. Mn active sites can accumulate electrons from the matrix and adsorb FeaqIII to form Mn-Fe bonds at the solid-liquid interface, which accelerate electron transfer from Mn-CNH to FeaqIII and promote the regeneration of FeII at a wide pH range with a lower energy barrier. The regeneration rate of FeII in the Mn-CNH/FeII/H2O2 system outperforms the benchmark Fenton system and other typical metal nanomaterials, which has great potential to be widely applied in actual environment remediation.

Sustainable conversion of antibiotic wastewater using microbial fuel cells: Energy harvesting and resistance mechanism analysis.

In this study, tetracycline (TC) can be degraded in microbial fuel cells (MFCs) rapidly and efficiently for the synergistic effect of microbial metabolism and electrical stimulation. Different TC concentrations had different effects on the bioelectric performance of MFCs. Among them, 10 mg/L TC promoted the bioelectric properties of MFCs, the maximum power density reached 1744.4 ± 74.9 mW/cm2. In addition, we demonstrated that Geobacter and Chryseobacterium were the dominant species in the anode biofilm, while Azoarcus and Pseudomonas were the prominent species in the effluent, and the initial TC concentration affected the microbial community composition. Furthermore, the addition of TC increased the relative abundance of aadA3, sul1, adeF, cmlA, and tetC in reactors, indicating that a single antibiotic could promote the expression of self-related resistance as well as the expression of other ARGs. Moreover, the presence of TC can increase the relative content of mobile genetic elements (MGEs) and greatly increase the risk of antibiotic resistance genes (ARGs) spreading. Meanwhile, network analysis revealed that some microorganisms (such as Acidovorax caeni, Geobacter soil, and Pseudomonas thermotolerans) and MGEs may be potential hosts for multiple ARGs.

Effect of HHCB and Cd on phytotoxicity, accumulation, subcellular distribution and stereoselectivity of chiral HHCB in soil-plant systems.

The toxicity of HHCB in the growth and development of plants is well known, but its uptake, subcellular distribution, and stereoselectivity, especially in a co-contamination environment, is not fully understood. Therefore, a pot experiment was performed to research the physiochemical response, and the fate of HHCB in pakchoi when the Cd co-existed in soil. The Chl contents were significantly lower, and the oxidative stress was aggravated under the co-exposure of HHCB and Cd. The accumulations of HHCB in roots were inhibited, and those in leaves were elevated. The transfer factors of HHCB in HHCB-Cd treatment increased. The subcellular distributions were analyzed in the cell walls, cell organelles, and cell soluble constituents of roots and leaves. In roots, the distribution proportion of HHCB followed cell organelle > cell wall > cell soluble constituent. In leaves, the distribution proportion of HHCB was different from that in roots. And the co-existing Cd made the distribution proportion of HHCB change. In the absence of Cd, the (4R,7S)-HHCB and (4R,7R)-HHCB were preferentially enriched in roots and leaves, and the stereoselectivity of chiral HHCB was more significant in roots than leaves. The co-existing Cd reduced the stereoselectivity of HHCB in plants. Our findings suggested that the fate of HHCB was affected by the co-existing Cd, so the risk of HHCB in the complicated environment should be paid more attention.

Magnetized manganese-doped watermelon rind biochar as a novel low-cost catalyst for improving oxygen reduction reaction in microbial fuel cells.

Microbial fuel cells (MFCs) are promising equipment for water treatment and power generation. The catalyst used in the oxygen reduction reaction (ORR) at the cathode is a critical factor for efficacy of MFCs. Therefore, it is important to develop cost-effective cathode catalysts to enhance application of MFCs. In the current study, a novel cathode catalyst was developed, which was annealed with watermelon rind as raw material and transition metals including iron, and manganese were introduced. The 700Mn/Fe@WRC catalyst, which was annealed at 700 °C, exhibited excellent electrochemical performance. The high relative content of pyridine nitrogen caused by the inherent nitrogen element of the watermelon rind and the high content of iron and manganese elements introduced resulted in increase in electrochemical surface area to 657.6 m2/g. The number of electrons transferred ORR was 3.96, indicating that ORR occurs through a four-electron pathway. The maximum power density of MFCs was 399.3 ± 7.4 mW/m2 with a fitting total internal resistance of 15.242 Ω, and the removal efficiency of COD was 97.1 ± 1.2%. The cost of the 700Mn/Fe@WRC catalyst was approximately 0.15 $/g, which is significantly lower compared with Pt/C (33.0 $/g). Experimental verification showed that the 700Mn/Fe@WRC prepared using the economical watermelon rind biochar (WRC) is an excellent substitute for non-precious metal catalysts used in MFCs.

The influence of external resistance on the performance of microbial fuel cell and the removal of sulfamethoxazole wastewater.

Microbial fuel cells (MFCs) are promising equipment for simultaneous treatment of sewage and power generation. External resistance (Rext) plays a crucial impact in the performance of MFCs in antibiotic wastewater treatment and antibiotic resistance genes (ARGs) reduction. In this study, Rext and whether to add 20 mg/L sulfamethoxazole (SMX) as variables, it was observed that the performance of several chemical properties of MFCs was optimal when Rext was 1000 Ω. The power density before and after addition of SMX was 1220.5 ± 24.5 mW/m2 and 1186.2 ± 9.2 mW/m2, respectively; Furthermore, the degradation rate of SMX was as high as 87.52 ± 1.97% within 48 h. High-throughput sequencing results showed that both Rext and SMX affected the microbial community and relative abundance of the phylum and genera. Meanwhile, the MFCs with 1000 Ω Rext generated less the targeted ARGs. Experimental results showed that 1000 Ω was the most suitable Rext for MFCs in the treatment of antibiotic wastewater.

[Research progress in water eco-functional regionalization].

Water eco-functional regionalization is a new zoning approach based on the study of regional differences in water ecosystem, aimed to reveal the spatial differentiation characteristics and distribution patterns of water environment at different regional and zonal scales. This paper discussed the methodologies, objectives, and limitations of water function zoning, water environmental function zoning, geoecology zoning, ecoregion classification, and water eco-functional regionalization, summarized the research progress in the water eco-functional regionalization, and compared the regionalization system at home and abroad. The disadvantages of our water eco-functional regionalization system were pointed out, and its development trend was prospected.

[Decontamination of heavy metals in wastewater by transgenic Synechococcus sp. PCC 7002 with mouse metallothionein-I gene].

The growth characteristics and the decontamination of heavy metals in analogous heavy metals wastewater by transgenic Synechococcus sp. PCC 7002 with mouse metallothionein-I gene were studied. The results show that transgenic Synechococcus sp. PCC 7002 not only has a higher tolerance to heavy metals, but also has a higher growth rate than wild strain. The concentration of Cd2+, Pb2+ and Hg2+ decreases with the progress of cultivation, and its maximum decreasing extent occurs at 1 - 3 day. After three days of cultivation, the absorption of Cd2+, Pb2+ and Hg2+ by transgenic Synechococcus sp. PCC 7002 is 10.75, 58.89 and 112.61 mg g(-1) of dried cells respectively, which is 3.16, 2.18 and 100.45 times higher than wild cells. The mono-factor and overall model developed fit the experiment data well.