Oriented generation of specific reactive oxygen species (ROS) has been challenging in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). In this work, we constructed a multifunctional catalyst composed of Ni NPs embedded in N-doped carbon nanotubes (NCNTs) with exposed Ni single-atom sites (Ni-NCNTs). The Ni-N4 single sites adjacent to the Ni NPs are more efficient for PMS adsorption and activation, resulting in enhanced production of singlet oxygen (1O2). More interesting, we demonstrated that the superoxide anion radical (O2•-) was generated from 1O2 reduction via the electron transfer from the graphitic-N sites of Ni-NCNTs rather than from O2 reduction or PMS decomposition as reported in previous studies. Thus, Ni-NCNTs can act as both electron acceptor and donor to trigger the cascade production of 1O2 and O2•-, respectively, leading to fast and selective degradation of aqueous organic pollutants. The graphitic-N adjacent to the aromatic π-conjugation of NCNTs facilitated chemisorption of 1O2 onto NCNTs via the strong π*-π interactions, and more importantly, donated the lone pair electrons to trigger the reduction of 1O2 to O2•-. This study unravels the mechanisms for enhanced production of ROS in the nanoconfined Fenton-like systems and shed new light on the application of multifunctional nanocatalyst for rapid wastewater decontamination.

Continuous increasing discharge of industrial oily wastewater and frequent occurrence of oil spill accidents have taken heavy tolls on global environment and human health. Organic-inorganic modifications can fabricate superhydrophilic/submerged superoleophobic membranes for efficient oil-water separation/treatment though they still suffer from complex operation, non-environmental friendliness, expensive cost or uneven distribution. Herein, a new strategy regarding tannic acid (TA)-Ti(IV) coating and CaCO3-based biomineralization through simple inkjet printing processes was proposed to modify polyvinylidene fluoride (PVDF) membrane, endowing the membrane with high hydrophilicity (water contact angle (WCA) decreased from 86.01° to 14.94°) and underwater superoleophobicity (underwater contact angle (UOCA) > 155°). The optimized TA-Ti(IV)-CaCO3 modified membrane possessed perfect water permeation to various oil/water emulsions (e.g., 355.7 L·m−2·h−1 for gasoline emulsion) under gravity with superior separation efficiency (>98.8 %), leading the way in oil/water emulsion separation performance of PVDF membranes modified with polyphenolic surfaces to our knowledge. Moreover, the modified membrane displayed rather high flux recovery after eight cycles of filtration while maintaining the original excellent separation efficiency. The modification process proposed in this study is almost independent of the nature of the substrate, and meets the demand for simple, inexpensive, rapid preparation of highly hydrophilic antifouling membranes, showing abroad application prospect for oil-water emulsion separation/treatment.

Industrial solid waste management and recycling are important to environmental sustainability. In this study, cobalt (Co) nanoparticles encapsulated in paint sludge-derived activated carbon (AC) were fabricated. The Co-AC possessed high conductivity, magnetic properties and abundant metal oxide impurities (TiAlSiOx), which was applied as multifunctional catalyst for peroxymonosulfate (PMS) activation. Compared to pure AC, the Co-AC exhibited significant enhanced performance for degradation of tetracycline hydrochloride (TCH) via PMS activation. Mechanism studies by in situ Raman spectroscopy, Fourier infrared spectroscopy, electrochemical analysis and electron paramagnetic resonance suggested that surface-bonded PMS (PMS*) and singlet oxygen (1O2) are the dominant reactive species for TCH oxidation. The non-radical species can efficiently oxidize electron-rich pollutants with high efficiency, which minimized the consumption of PMS and the catalyst. The removal percentages of TCH reached 97 % within 5 min and ∼ 99 % within 15 min in the Co-AC/PMS system. The Co active sites facilitated PMS adsorption to form the PMS* and the TiAlSiOx impurities provided abundant oxygen vacancy for generation of the 1O2. In addition, the Co-AC/PMS system achieved high efficiency and stability for oxidation of the target pollutants over a long-term continuous operation. This work not only offers a cost-effective approach for recycling industrial waste but also provides new insights into the application of waste-derived catalyst for environmental remediation.

While ethylenediamine tetramethylenephosphonic acid (EDTMPA) has been emerged as a stronger chelating agent than ethylene diamine tetraacetic acid (EDTA) for fouling mitigation, and transparent exopolymer particles (TEP) is a major foulant in membrane-based water treatment process, effects of EDTMPA on TEP fouling and the underlying mechanism have been not yet studied. In this study, Flory-Huggins lattice theory was combined with density functional theory (DFT) technology to explore this subject at molecular level. Filtration experiments showed a unimodal pattern of specific filtration resistance (SFR) of TEP sample with Ca2+ concentration in range of 0–3 mM. For the TEP sample with the peak SFR value at 1.5 mM Ca2+, continuous addition of EDTMPA (from 0 to 100 mg·L−1) resulted in a sustained decrease in SFR. Energy dispersive spectroscopy (EDS) mapping characterization showed the continuing decline of calcium content in the TEP layer with increase of EDTMPA addition, indicating that EDTMPA successfully captured Ca2+ from alginate‑calcium ligation (TEP), and then disintegrated the TEP structure. DFT simulation showed that Ca2+ preferentially coordinated with the terminal carboxyl groups of alginate chains to form a coordination configuration that is conducive to stretch the three-dimensional polymer network. Such a network corresponded to an extremely high SFR according to Flory-Huggins theory. EDTMPA addition caused disintegration of the coordination configuration of Ca2+ binding to terminal carboxyl groups, which further resulted in collapse and flocculation of TEP gel network structure, thus leading to a continuous SFR decrease. This work provided deep thermodynamic insights into effects of EDTMPA on TEP-associated fouling at molecular level, facilitating to better understanding and mitigation of membrane fouling.

Wettability of membrane is of vital importance for treatment of oily wastewater. In recent years, hydrophilic modifications based on plant polyphenol have been widely investigated to enhance the anti-fouling property of membranes due to their mild conditions, versatility and low cost. However, there are still some problems in improving raw material utilization and hydrophilicity. Herein, a facile method was proposed to optimize tannic acid (TA)-based membrane modification process by synergistically inducing TA deposition by Fe3+ and SP with the assistance of inkjet printing. The hydrophobicity of polyvinylidene fluoride (PVDF) membrane was converted to hydrophilicity (WCA = 34.6 degrees) and underwater oleophobicity (UOCA = 144.4 degrees) in very short time (10 min). The optimum PVDF/Fe-TA-SP422 membrane possessed high flux (4968.4-7340.4 L m(-2) h(-1).bar(-1)) for a number of oil/water emulsions with high separation efficiency (>98%), outperforming most state-of-the-art membranes for oil-water separation. Furthermore, the optimized membrane displayed not only high antifouling property and reusability with flux recovery ratio of 89.1%-98.0% after eight-cycle filtration, but also desired stability under near neutral pH conditions during long-term running. The combination of inkjet printing method with these materials proposed in this study is convenient, efficient and low cost, and the prepared membranes are versatility, providing novel insights into preparation of high efficiency membranes for oily wastewater treatment.

While transparent exopolymer particles (TEP) is a major foulant, and ethylene diamine tetraacetic acid (EDTA) is a strong chelating agent frequently used for fouling mitigation in membrane-based water treatment processes, little has been known about TEP-associated membrane fouling affected by EDTA. This work was performed to investigate roles of EDTA addition in TEP (Ca-alginate gel was used as a TEP model) associated fouling. It was interestingly found that, TEP had rather high specific filtration resistance (SFR) of 2.49 × 1015 m-1·kg-1, and SFR of TEP solution firstly decreased and then increased rapidly with EDTA concentration increase (0-1 mM). A series of characterizations suggested that EDTA took roles in SFR of TEP solution by means of changing TEP microstructure. The rather high SFR of TEP layer can be attributed to the big chemical potential gap during filtration described by the extended Flory-Huggins lattice theory. Initial EDTA addition disintegrated TEP structure by EDTA chelating calcium in TEP, inducing reduced SFR. Continuous EDTA addition decreased solution pH, resulting into no effective chelating and accumulation of EDTA on membrane surface, increasing SFR. It was suggested that factors increasing homogeneity of TEP gel will increase SFR, and vice versa. This study revealed the thermodynamic mechanism of TEP fouling behaviors affected by EDTA, and also demonstrated the importance of EDTA dosage and pH adjustment for TEP-associated fouling control.

Effects of iron(III) ion level and ionic strength on membrane fouling in coagulation-ultrafiltration (UF) process were explored in this study. Two interesting filtration phenomena during the filtration process were observed: extremely reduced specific filtration resistance (SFR) of alginate solution complexed with iron (III) ions level from 0.1 to 2.0 mM (phenomenon I), and different change trends of alginate SFR with ionic strength between two iron(III) ion levels (remarkable increase trend of alginate SFR with ionic strength at 0.1 mM ions level while almost remaining unchanged trend at 2.0 mM ions level) (phenomenon II). Experimental characterizations indicated that the two phenomena were closely linked to changes of zeta potential, viscosity and morphology of the related foulants. It was proposed that iron(III) ions at low level (0.1 mM) preferentially coordinate the terminal carboxyl groups of alginate chains and form gel layer. The chemical potential gap described by Flory-Huggins lattice theory is responsible for the extremely high SFR of gel layer. Coordinating the non-terminal carboxyl groups at high iron(III) ion level (2.0 mM) causes transition from gel layer to cake layer formation during filtration, and lots of interstices in cake layer correspond to low SFR, well interpreting phenomenon I. Meanwhile, electrostatic double layer compression caused by the increased ionic strength makes the gel layer shrunk and denser for low iron(III) ion level, but less affects the number and size of interstices in the cake layer for high iron(III) ion level, reasonably explaining phenomenon II. This study revealed essential and comprehensive thermodynamic fouling mechanisms and facilitated to optimize coagulation-UF/MF process.

Effects of calcium ions and polyaluminum chloride (PACl) on membrane fouling in coagulation-ultrafiltration (UF) process were investigated in this study. Filtration tests demonstrated three interesting filtration behaviors: 1) high specific filtration resistance (SFR) of alginate solution with low CaCl2 or PACl addition (e. g. 3.51 x 10( 15) m.kg(-1) under the condition of 1.5 mM CaCl2 addition); 2) unimodal pattern of alginate SFR with PACl or CaCl2 addition alone; 3) synergistic effects between CaCl2 and PACl on alginate SFR. It was found that, the foulant morphological changes driven by the thermodynamic mechanisms based on Flory-Huggins lattice theory take the critical roles in these filtration behaviors. Density functional theory (DFT) calculations showed that initial coordination of Ca2+ and Al3+ ions with alginates tended to form tetrahedron geometry and geometry of coordinating three terminal carboxyl groups, respectively, which facilitated to elongate the alginate chains (without clustering the flocs) and form more stable gel, increasing SFR. Improving Ca2+ and Al3+ dosages triggered transition to other geometries for clustering polymeric network and flocculation, reducing SFR. Due to the higher binding affinity of Ca2+ over Al3+, Ca2+ and Al3+ sequentially take roles of enlarging polymeric network and clustering the coordination compounds, and then facilitate to form large size flocs and reduce SFR, causing the synergistic effects between CaCl2 and PACl additions. The proposed thermodynamic mechanisms satisfactorily explained these interesting fouling behaviors, allowing to further optimize coagulation-UF process. (C) 2020 Elsevier Ltd. All rights reserved.

A novel graphene based nanosorbents, Fe3O4-graphene@mesoporous SiO2nanocomposites(deno-ted as MG@m-SiO2)was synthesized.The obtained MG@m-SiO2were characterized by scanning electron mi-croscopic(SEM), transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),Fou-rier transformed infrared spectroscopy(FTIR)and X-ray diffraction(XRD).The adsorptive property was in-vestigated by using MG@m-SiO2as sorbents and methyl red(MR),a common dye,as model of the organic pollutants.Adsorption kinetics,isotherms,thermodynamics as well as effects of pH and adsorbent dose on the adsorption were studied.The adsorption isotherms and kinetics were described by Langmuir isotherm model and pseudo-second-order kinetic model,respectively.Thermodynamic studies suggested that the adsorption of MR onto the MG@m-SiO2was endothermic and spontaneous process.The results implied that the MG@m-SiO2could be served as a cost-effective adsorbent for the removal of organic pollutants from aqueous solutions.

Synthesis of magnetic graphene mesoporous silica (G/SiO2/Fe3O4) composites and a new method using a column packed with G/SiO2/Fe3 O4 as sorbent was developed for the separation and preconcentration of Methylene Blue (MB).Some effective parameters on the extraction such as pH,sample volume,flow rates,amounts used of adsorbents,eluent type and its volume were selected and optimized.Under the optimum condition,the qualitative limit (S/N =3) for MB were found to be 10 μg/L,the recoveries for the analytes were in the range of 94.3％～95.4％.The proposed method was showed to be an effective approach for determination of MB in environment water samples.

Photocatalytic conversion of CO2 to value-added chemicals, a potential route to addressing the depletion of fossil fuels and anthropogenic climate change, is greatly limited by the low-efficient semiconductor photocatalyst. The integration of cocatalyst with light-harvesting semiconductor is a promising approach to enhancing the photocatalytic performance in CO2 reduction reaction. The enhancement is greatly determined by the catalytic active sites on the surface of cocatalyst. Herein, we demonstrate that the photocatalytic performance in the CO2 reduction reaction is greatly promoted by twin defects engineered Pd cocatalyst. In this work, Pd nanoicosahedrons with twin defects were in situ grown on C3N4 nanosheets, which effectively improve the photocatalytic performance in reduction of CO2 to CO and CH4 in comparison with Pd nanotetrahedrons without twin defects. It is proposed that the twin boundary (TB) terminations on the surface of Pd cocatalysts are highly catalytic active sites for CO2 reduction reaction. Based on the proposed mechanism, the photocatalytic activity and selectivity in CO2 reduction were further advanced through reducing the size of Pd icosahedral cocatalyst resulted from the increased surface density of TB terminations. The defect engineering on the surface of cocatalyst represents a novel route in realizing high-performance photocatalytic applications.

The integration of plasmonic metal with wide-bandgap semiconductor is a promising approach to utilize the visible light without compromise of the redox ability of photogenerated charge carriers. However, a larger work function of metal than that of semiconductor is indispensable to enable the injection of hot electrons from plasmonic metal to semiconductor. In this paper, we demonstrated that reduced graphene oxide (rGO) nanosheets as conductive "bridge" can breakthrough the restriction and transfer hot electrons from Ag of smaller work function to TiO2 of larger work function. In the design, both of the Ag nanocubes and TiO2 nanosheets are co-deposited on the surface of rGO nanosheets to form Ag-rGO-TiO2 structure, which was characterized by XRD, TEM, Raman and XPS spectra. On one hand, the Ag-rGO interface facilitates the transfer of hot electrons from Ag to rGO through conductor conductor contact. On the other hand, the new formed Schottky junction on the rGO-TiO2 interface further pumps the transferred electrons to the surface of TiO2 for photocatalytic reduction reaction resulted from the larger work function of rGO than that of TiO2. Enabled by this unique design, the hydrogen production activity achieved under visible light irradiation is dramatically enhanced in comparison with that of Ag-TiO2 counterpart with the direct contact between the same Ag nanocubes and TiO2 nanosheets. This work represents a step toward the rational interfacial design of plasmonic metal-semiconductor hybrid structures for broad-spectrum photocatalysis.

Influences of fractal dimension (Df) of membrane surface on interfacial interactions related to membrane fouling in a membrane bioreactor were investigated based on thermodynamic methods. It was found that membrane surface had significant fractal features, and its fractal dimension could be characterized by the power spectrum method. The modified Weierstrass-Mandelbrot (WM) function was found to be effective to model the fractal membrane surface, and higher Df corresponded to higher number of fine asperities in the modeled surface. Moreover, the modeled surface roughness exponentially decreased with Df. Interaction calculations according to a novel method showed that the interactions for fractal membrane surface were elongated and weakened as compared with smooth membrane surface. It was interestingly found that the absolute value of total interaction monotonically decreased with Df of membrane surface. As Df is a measure of substance stiffness, this result indicates that softer surface is more susceptible to adhesion by sludge foulant. The results offered new insights into membrane fouling mechanisms and alleviation.

Interfacial interactions between foulants and membrane directly determine foulant adhesion and membrane fouling. In this study, surface of sludge foulant particles (flocs) was found to be rough, and could be modeled by a sinusoidal sphere function. A novel method, which combined surface element integration (SEI) method, differential geometry and composite Simpson's rule, was developed to quantify the interfacial interactions between the modeled rough floc surface and membrane surface. Application of the novel method in a membrane bioreactor (MBR) provides broad profiles of quantitative interactions with rough floc surface with separation distance. It is also found that increase in the scaled amplitude of floc surface significantly reduced the interaction strength. Derjaguin's approximation (DA) can be regarded as a special case of the novel method, indicating the extensive application prospect of the novel method. The novel method for interaction calculation was verified to be correct and feasible. Finally, roles of the novel method in membrane fouling research were discussed.

While the adsorptive fouling in membrane bioreactors (MBRs) is highly dependent of the surface morphology, little progress has been made on modeling biocake layer surface morphology. In this study, a novel method, which combined static light scattering method for fractal dimension (Df) measurement with fractal method represented by the modified two-variable Weierstrass-Mandelbrot function, was proposed to model biocake layer surface in a MBR. Characterization by atomic force microscopy showed that the biocake surface was stochastic, disorder, self-similarity, and with non-integer dimension, illustrating obvious fractal features. Fractal dimension (Df) of sludge suspension experienced a significant change with operation of the MBR. The constructed biocake layer surface by the proposed method was quite close to the real surface, showing the feasibility of the proposed method. It was found that Df was the critical factor affecting surface morphology, while other factors exerted moderate or minor effects on the roughness of biocake layer.

Developing strategies that allow tuning anti-adhesion ability of membranes in membrane bioreactors (MBRs) is of primary interest in membrane fouling research. In this study, interaction energies between foulants and membrane in three different interaction scenarios were systematically assessed based on thermodynamic methods. It was found that, membrane surface electron donor tension (gamma(-)) rather than surface hydrophilicity was a more reliable indicator to predict adsorptive fouling. The interaction energy would be continuously repulsive in the initial range of separation distance when membrane gamma(-) is higher than a critical value, suggesting that designing membrane with gamma(-) higher than a critical value would confer membrane with high anti-adhesion ability. It was also found that, zeta potential on the membrane surface exerted certain effects on adsorptive fouling. This study proposed a novel strategy regarding adjusting membrane gamma(-) to tune anti-adhesion ability of membrane, and also offered a thermodynamic theoretical background to this strategy. (C) 2016 Elsevier Ltd. All rights reserved.

Carbon dots are novel fluorescent nano-materials which have easy to preparation. They have good stability, low toxicity, environment-friendly and are widely used in biological imaging, biomedical, and biochemical analysis, metal reduction, fluorescence probe and optoelectronic devices. This paper summarized several new methods for the detection of metal ions with carbon dots.

More and more heavy metal ions pollution events happen nowadays, so how to detect and remove heavy metal ions is a very important problem. Electrochemical method is relatively simple device, convenient automatic operation. Because of its high sensitivity and good selectivity, it becomes a good method to detect heavy metal ions. This paper summarized the detection of heavy metal ions by stripping voltammetry.

A new method of cloud point extraction-UV spectrophotometry based on using Triton X-114 as an extractant was developed for simultaneous determination of magnolol and honokiol in traditional Chinese medic -inal material.The effects of the pH of solution , concentrations of surfactant Triton X-114, equilibrium temper-ature and time on the efficiency of cloud point extraction were systematically examined .Under the optimized conditions, the linear equations were Y1 =5.89 ×10 -4x-1.14 ×10 -3(R2 =0.992 1), Y2 =5.52 ×10 -4x+7.71 ×10 -5(R2 =0.999 2), the detection limits were 2.5 μg/L, 1.0 μg/L for magnolol and honokiol, re-spectively .This method was applied to the determination of honokiol and magnolol in traditional Chinese me -dicinal material with recoveries of 98.4%~104.3%.