A novel, flexible porous nanofibrous hydrogel interfacial solar evaporator for highly efficient seawater and wastewater purification.

Solar desalination is recognized as one of the eco-friendly and sustainable ways to alleviate the global freshwater crisis but still requires further research, especially in developing high-performance evaporators. Herein, we prepared an efficient carbon nanotubes (CNTs)@polyvinyl alcohol (PVA) nanofibrous hydrogel evaporator by electrospinning and subsequently chemical cross-linking treatment. Due to CNTs with good light absorption capacity, the evaporator exhibited an excellent light absorption capacity (>90%) throughout the full spectrum range (250-2500 nm). Meanwhile, the interconnected pores from electrospinning, as well as the intermediate water in the hydrogel, ensured the prepared evaporator with a favorable evaporation rate of up to 2.16 kg m-2 h-1 and photothermal conversion efficiency of ∼88.13% under one solar light intensity. For long-term seawater desalination, the CNTs@PVA nanofibrous hydrogel evaporator also presented superior salt resistance, durability and good self-cleaning properties. Besides, various non-volatile pollutants can be completely removed by the prepared evaporator during the wastewater purification. As a result, this work is considered to provide a new direction for developing high-performance evaporators to provide freshwater through seawater desalination and wastewater purification.

Effects of CeO2, CuO, and ZnO nanoparticles on physiological features of Microcystis aeruginosa and the production and composition of extracellular polymeric substances.

Extracellular polymeric substances (EPS) are key components of the cyanobacterium Microcystis aeruginosa and play an important role in cyanobacteria blooms formation. Here, we analyzed the effects of 48-h exposure to nanosized CeO2 (n-CeO2), CuO (n-CuO), and ZnO (n-ZnO) on the production and composition of EPS of M. aeruginosa. Toxicity experiments revealed that soluble nanoparticles (NPs) (n-ZnO, n-CuO) demonstrated higher toxicity to cells and caused membrane damage. The production of LB-EPS increased by 34.48, 20.09, and 46.33 %, and TB-EPS increased by -5.78, 22.3, and -2.67 % in the presence of n-CeO2, n-CuO, and n-ZnO NPs, respectively, and polysaccharides are the main incremental portion compared with protein and humic acids. Three-dimensional excitation-emission fluorescence spectra revealed the enhancement of fulvic-humic-like and disappearance of tyrosine aromatic substances in TB-EPS compared with the slight changes observed in LB-EPS. Fourier-transform infrared spectroscopy illustrated the susceptibility of -NH2 and double-bonded carbon and oxygen in amides to three types of NPs. These results improve our understanding of the potential influence of NPs on the aggregation behaviors of cyanobacteria and formation process of cyanobacteria blooms. Graphical abstract ᅟ.

Effects of cerium oxide nanoparticles on the species and distribution of phosphorus in enhanced phosphorus removal sequencing batch biofilm reactor.

The short term (8h) influences of cerium oxide nanoparticles (CeO2NPs) on the process of phosphorus removal in biofilm were investigated. At concentration of 0.1mg/L, CeO2 NPs posed no impacts on total phosphorus (TP) removal. While at 20mg/L, TP removal efficiency reduced from 85.16% to 59.62%. Results of P distribution analysis and 31P nuclear magnetic resonance spectroscopy implied that the anaerobic degradation of polyphosphate (polyP) and the release of orthophosphate in extracellular polymeric substances (EPS) were inhibited. After aerobic exposure, the average chain length of polyP in microbial cells and EPS was shorter than control, and monoester and diester phosphates in cells were observed to release into EPS. Moreover, the EPS production and its contribution to P removal increased, while the capacity of EPS in P storage declined. X-ray diffraction analysis and saturation index calculation revealed that the formation of inorganic P precipitation in biofilm was inhibited.

Transport, retention, and long-term release behavior of polymer-coated silver nanoparticles in saturated quartz sand: The impact of natural organic matters and electrolyte.

This study investigated the transport and long-term release of stabilized silver nanoparticles (AgNPs), including polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs) and bare AgNPs (Bare-AgNPs), in the presence of natural organic matters (NOMs; both humic acids (HA) and alginate (Alg)) and an electrolyte (Ca2+) in a sand-packed column. Very low breakthrough rate (C/C0) of AgNPs (below 0.04) occurred in the absence of NOM and the electrolyte. Increasing the concentration of NOM and decreasing the influent NOM solution's ionic strength (IS) reduced the retention of AgNPs. The reduced NP retention at high NOM and low IS was mainly attributed to the increased energy barrier between the AgNPs and the sand grain surface. Notably, the retention of PVP-AgNPs was enhanced at high Alg concentration and low IS, which mainly resulted from the improved hydrophobicity that could increase the interaction between the PVP-AgNPs and the collector. The total release amount of PVP-AgNPs (10.03%, 9.50%, 28.42%, 6.37%) and Bare-AgNPs (3.28%, 2.58%, 10.36%, 1.54%) were gained when exposed to four kinds of NOM solutions, including deionized water, an electrolyte solution (1 mM Ca2+), HA with an electrolyte (1 mM Ca2+), and a Alg (40 mg/L) solution with an electrolyte (1 mM Ca2+). The long-term release of retained silver nanoparticles in the quartz sand was mostly through the form of released Ag NPs. The factors that increased the mobility of AgNPs in quartz sand could improve the release of the AgNPs. The release of AgNPs had no significant change in the presence Ca2+ but were increased in the presence of HA. The Alg slightly decreased the release of AgNPs by increasing the hydrophobicity of AgNPs. The results of the study indicated that all the tested NOM and Ca2+ have prominent influence on the transport and long-term release behavior of silver nanoparticles in saturated quartz sand.

Transport and long-term release behavior of polymer-coated silver nanoparticles in saturated quartz sand: The impacts of input concentration, grain size and flow rate.

This study investigated the transport and long-term release of stabilized poly vinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) in a quartz sand column with various sand grain sizes (0.3-0.5 µm, 0.5-1.0 µm, 1.0-2.0 µm), input concentrations of PVP-AgNP solution (1, 5, 15, 25 mg/L), and flow rates corresponding to a filter velocities (1.0, 1.5, 2.0, 2.5 mL/min-0.14, 0.21, 0.28, 0.35 cm/min) by determining breakthrough curves, retention profiles, and long-term release curves. Breakthrough curves and retention profiles were simulated by a mathematical model based on the advection dispersion equation coupled with second-order kinetics. The increased transport of PVP-AgNPs in quartz sand occurred with increased grain sizes and reduced input concentrations, and the transport can be predicted by the colloid filtration theory and DLVO theory. The long-term (one week) release amounts of retained PVP-AgNPs were 42.78%, 31.45%, and 10.95% in the fine, medium, and coarse sand columns, respectively, and were 34.70%, 40.79%, 47.24%, and 57.32% at flow rates of 0.0363, 0.0436, 0.0545, and 0.0726 mL/min, respectively. The released quantity of retained PVP-AgNPs decreased as the sand grain size increased. This phenomenon is opposite with the trend of increased transport of PVP-AgNPs with increased grain size in the transport test, which most likely because colloidal filtration regulates the transport process and adsorption (and desorption) dominates the release process. Increasing the flow rate increased the shear force on the particles, which improved the release of PVP-AgNPs. The results of the release tests further verified our previous published studies showing that the long-term release of retained PVP-AgNPs in the quartz sand was mostly in the form of released nanoparticles rather than ions. The results of this study indicated that sand grain size, input concentration, and flow rate have a prominent influence on the transport and long-term release behavior of PVP-AgNPs in saturated quartz sand.

Effects of CeO2 nanoparticles on production and physicochemical characteristics of extracellular polymeric substances in biofilms in sequencing batch biofilm reactor.

Extracellular polymeric substances (EPS) are a major component of biofilms that act as a gel-like matrix, binding the cells together to form their three-dimensional structure. The effects of ceria nanoparticles (CeO2 NPs) on the production and physicochemical characteristics of EPS in biofilms in a sequencing batch biofilm reactor were investigated. Total EPS production, including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), increased by 35.41% compared to in control tests without CeO2 NPs. Protein production increased by 47.02% (LB-EPS) and 58.83% (TB-EPS) after 50 mg/L CeO2 NP exposure. Three-dimensional excitation-emission fluorescence spectra revealed that tyrosine (LB-EPS) and aromatic (TB-EPS) protein-like substances formed after CeO2 NP exposure. Fourier transform infrared spectroscopy results indicated the susceptibility of -OH and -NH2 in EPS hydroxyl and amine groups to CeO2 NPs. Exposure to 50 mg/L CeO2 NPs reduced the flocculating capacity of LB-EPS (51.78%) and TB-EPS (17.14%), consistent with the decreased zeta potential.