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With the frequent occurrence of oil spill accidents and the continuous discharge of oily water during oil production and transportation, effective oil removal from environmental water by adsorption still faces severe challenges. Here, a novel absorbent hydroxofluorographene-coated melamine foam, namely G(OH)F@MF, with high affinity to oils was fabricated via stepwise assembly. The G(OH)F@MF absorbent achieved effective removal of various oils within 1 min with relatively high adsorption capacities for petrol (89.34 g/g), lubricating oil (89.60 g/g), and peanut oil (104.79 g/g). Furthermore, it could be regenerated by simply squeezing and reused for more than 10 times with an adsorption capacity exceeding 37.12 g/g. In addition, the results indicated that the G(OH)F@MF absorbent was suitable for oil cleanup at a wide range of pH values (4-12) and temperatures (5-45 °C). The adsorption performance of the material was stable in the presence of natural organic matter and even in different water environments. This study can provide a novel sorbent and method for the green, rapid, recyclable, and stable removal of oils from environmental water.

Black carbon is considered as a promising material for thin-layer capping for sediment remediation. However, the effects of black carbon-based thin-layer capping on microbial communities have not been thoroughly studied. Here, the preparation conditions of capping material were optimized, and the interaction and assembly mechanisms of the microbial community in sediment under black carbon capping were studied. The results showed that concentration of NH4+-N in the overlying water was stably lower than 0.5 mg/L after capping. The abundance of key genes related to nitrogen transformation in the sediment was increased. Denitrification was the dominant nitrogen removal pathway under coarse granule capping, while aromatic compound degradation was dominant under fine granule capping and dissimilatory N reduction to ammonium was regarded as the dominant nitrogen removal pathway. Community assembly was mainly driven by deterministic processes (≥ 80%). Interactions between rare and common operational taxonomic units were most frequent. The functional zoning of nitrogen transformation in the vertical aerobic, hypoxic, and anaerobic zones of the sediment was strengthened because of black carbon capping. Overall, these results expand our current understanding of the ecological significance of black carbon capping for remediating contaminated sediment.

Understanding the ecological relationship of microbial community under external stimulation is crucial for environmental restoration. Black carbon (e.g., biochar) have been widely deemed as a strategy to enhance pollutants removal because of its structure and redox-active property. However, the underlying ecological mechanism of microbial community under black carbon addition is poorly understood. The major purposes of this study were to determine the microbial assemblage and functional patterns via null model test, network analysis, and function prediction. The results showed that the nitrate removal efficiency of modified black carbon system achieved 46.44%. Both deterministic and stochastic processes were significant for mediating the microbial assemblage and the deterministic process dominated (>95%) the assemblage of community. Keystone taxa in the black carbon systems, involving Sulfuricella, Allorhizobium, and Nitrospira, stimulated the shift of community composition regarding the nitrogen removal. The existence of black carbon and the biotic interactions increased biological nitrate utilization and promoted nitrogen removal. Overall, this study presents the mechanism of bacterial community assembly and provides insight into biological nitrogen removal from microbial ecological perspective.

Understanding the underlying mechanism that drives the microbial community mediated by graphene derivative is crucial for achieving the enhancement of biological nitrogen removal by external stimulation. The main objectives of this study were to identify the bacterial community assembly mechanism via null model test and molecular ecological network analysis in the sediment culture system. Results showed graphene derivative increased biological nitrogen removal efficiency by 125%. The high electron transfer efficiency and denitrifying enzyme activities were achieved. Deterministic assembly is dominate (>90%) in all the community assembly while the stochastic assembly process only existed in graphene derivative system (6.67%). The nitrogen removal was enhanced due to the intensification of the interaction on the microbial community between stochastic assembly and deterministic assembly. Keystone taxa in the graphene derivative systems, including Sulfuricella, Rhodobacter, and Comamonadaceae, drove the alteration of community structure relating to the nitrogen removal.

Static magnetic field (SMF) with the intensity of 15 mT was applied during partial nitrification (PN) process to evaluate the impacts on nitrogen transformation and microbial characteristics. Results showed that the startup period of PN process at ambient temperature was markedly shortened by SMF, and the nitrite accumulation increased by 18% due to SMF exposure. The ammonia oxidizing bacteria (AOB) amoA gene copy numbers in the reactor with SMF exposure were 40% higher than that without SMF exposure, indicating the AOB abundance was enriched by SMF exposure. The characteristics of extracellular polymeric substances (EPS) changed accordingly. The extracellular protein increased by 30% due to SMF exposure, and it favored the aggregation of sludge flocs. The activated sludge with SMF exposure had a more compact structure, which was in favor of partial nitrification.