Improvements of response surface modeling with self-adaptive machine learning method for PM2.5 and O3 predictions.

Quickly quantifying the PM2.5 or O3 response to their precursor emission changes is a key point for developing effective control policies. The polynomial function-based response surface model (pf-RSM) can rapidly predict the nonlinear response of PM2.5 and O3 to precursors, but has drawbacks of overload computation and marginal effects (relatively larger prediction errors under strict control scenarios). To improve the performance of pf-RSM, a novel self-adaptive RSM (SA-RSM) was proposed by integrating the machine learning-based stepwise regression for establishing robust models to increase the computational efficiency and the collinearity diagnosis for reducing marginal effects caused by overfitting. The pilot study case demonstrated that compared with pf-RSM, SA-RSM can effectively reduce the training number by 70% and 40% and the fitting time by 40% and 52%, and decrease the prediction error by 49% and 74% for PM2.5 and O3 predictions respectively; moreover, the isopleths of PM2.5 or O3 as a function of their precursors generated by SA-RSM were more similar to those derived by chemical transport model (CTM), after successfully addressing the marginal effect issue. With the improved computation efficiency and prediction performance, SA-RSM is expected as a better scientific tool for decision-makers to make sound PM2.5 and O3 control policies.

Fabrication and high photoelectrocatalytic activity of scaly BiOBr nanosheet arrays.

Bismuth oxybromide (BiOBr) nanosheet arrays (NSAs) were successfully prepared on the surface of indium tin oxide glass (hydrophilic pretreated) by solvothermal method using [C16mim]Br ionic liquid as bromine source and template. The effects of different reaction temperatures on array synthesis were investigated. BiOBr NSA-160 (NSAs prepared at 160 °C for 8 h) had the best photoelectrocatalytic (PEC) activity. The removal rate of ciprofloxacin hydrochloride by BiOBr NSA-160 was 91.4% by applying a bias voltage of 0.9 V and irradiating under visible light for 180 min. Results of the analyses of the morphology, photoelectric properties, energy band structure, and degradation active species show that BiOBr NSA-160 is a p-type photocatalyst with a thickness of approximately 500 nm, a light response range of less than 440 nm, and photocurrent density of 69 µA/cm2 at the optimal bias voltage is 0.9 V. The high PEC activity of BiOBr NSA-160 was deduced from two aspects: one is that the bias potential effectively improves the separation efficiency of photogenerated carrier, and the other is that the structure of the nanoarray increases light absorption and active sites. BiOBr NSAs are promising PEC material for application in pollutant removal.

Novel biochar@CoFe2O4/Ag3PO4 photocatalysts for highly efficient degradation of bisphenol a under visible-light irradiation.

In the study, a series of novel Z-scheme biochar@CoFe2O4/Ag3PO4 photocatalysts were synthesized and employed to degrade bisphenol A under visible light irradiation (λ ≥ 420 nm). The structural morphology, optical properties and physicochemical properties of composites were characterized by means of TEM, XRD, FT-IR, XPS, UV-Vis, BET, EIS and VSM analysis. The photocatalytic performances of the photocatalysts were evaluated systematically. The MBA-3 photocatalyst exhibited the highest photocatalytic and mineralization ability within 60 min among all photocatalysts, 91.12% and 80.23%, respectively. After four cycles, the degradation of BPA still kept the photocatalytic activity of 73.94%, and the removal rate of TOC remained 58.96%. Moreover, the active species in the photocatalytic process were evaluated, and we proposed the Z-scheme photocatalytic mechanism for highly efficient degradation of BPA. According to the GC-MS results, the photodegradation pathway of BPA is also suggested. The present study has provided a valuable way of using the magnetic biochar in the design of new and efficient system for the degradation of organic pollutions in waste water.

A near infrared fluorescent probe based on ICT for monitoring mitophagy in living cells.

Mitophagy, the process in which cells degrade dysfunctional organelles and recycle their nutrient substances by lysosomes, plays a vital role in cell metabolism and physiology. Herein, we present a highly targeting and near-infrared (NIR) mitochondrion fluorescent probe, which can monitor the process of autophagy. The response mechanism of the probe is based on intramolecular charge transfer (ICT) for the detection of autophagy and real-time imaging of living cells. We designed a primary amine as a pH sensitizing group, and due to the ICT process, the probe exhibits green fluorescence, and when it is protonated the ICT process is broken, and the NIR fluorescence will be restored. Simultaneously, the green fluorescence of the probe disappears. This probe exhibits excellent selectivity, high sensitivity and clean responsiveness, which indicate that it can be applied for high-targeting and high-sensitive imaging of the process of autophagy in living systems.

Imaging the Microprocesses in Biofilm Matrices.

Biofilms, which are aggregates of microorganisms and extracellular matrices, widely colonize natural water bodies, wastewater treatment systems, and body tissues, and have vital roles in water purification, biofouling, and infectious diseases. Recently, multiple imaging modalities have been developed to visualize the morphological structure and material distribution within biofilms and to probe the microprocesses in biofilm matrices, including biofilm formation, transfer and metabolism of substrates, and cell-cell communication. These technologies have improved our understanding of biofilm control and the fates of substrates in biofilms. In this review, we describe the principles of various imaging techniques and discuss the advantages and limitations of each approach to characterizing microprocesses in biofilm matrices.

Identification and function of extracellular protein in wastewater treatment using proteomic approaches: A minireview.

Microbial extracellular proteins serve as important functions in wastewater treatment process. Analysis of their compositions and properties is crucial to probe their specific functions. However, conventional analytical techniques cannot obtain interest protein information from complex proteins. Recently, the extracellular proteomics method has been applied to resolve the composition of extracellular proteins. In order to better understand the roles of extracellular protein in wastewater treatment process, this review provides the information on the proteomics methods and their application in investigating extracellular proteins involved in microbial attachment/aggregation, biodegradation of pollutants, and response to environmental stresses. Future work needs to exploit the full capability of the proteome.

Insight on the plasmonic Z-scheme mechanism underlying the highly efficient photocatalytic activity of silver molybdate/silver vanadate composite in rhodamine B degradation.

A facile deposition-precipitation method was applied to synthesize novel plasmonic Z-scheme Ag2MoO4/Ag3VO4 photocatalysts with different molar ratios of Ag2MoO4. The morphological, structural, and spectroscopic properties of the as-obtained samples were characterized through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectral analysis. The photocatalytic performance of the synthesized photocatalysts in rhodamine B (RhB) degradation under visible light irradiation was evaluated. The 5% Ag2MoO4/Ag3VO4 composite displayed the highest photocatalytic activity among all samples and the RhB removal rate of 93% within 6 min. The RhB removal rate of 5% Ag2MoO4/Ag3VO4 composite was higher than that of precursor Ag2MoO4 and Ag3VO4 compounds. The formation of Ag nanoparticles (Ag NPs) on the surface of Ag2MoO4/Ag3VO4 during photocatalysis resulted in the transformation of the Ag2MoO4/Ag3VO4 heterojunction to the Ag2MoO4/Ag/Ag3VO4 Z-scheme system, thus enhancing photocatalytic activity. Z-scheme Ag2MoO4/Ag/Ag3VO4 composites could efficiently facilitate charge transfer, promote redox ability, and restrain Ag3VO4 photocorrosion. The produced active species O2-, h+, and OH are vital for RhB degradation. The present work could benefit the development of advanced visible-light photocatalytic materials with future applications in environmental remediation.

Dynamic Dispersal of Surface Layer Biofilm Induced by Nanosized TiO2 Based on Surface Plasmon Resonance and Waveguide.

Pollutant degradation is present mainly in the surface layer of biofilms, and the surface layer is the most vulnerable to impairment by toxic pollutants. In this work, the effects of nanosized TiO2 (n-TiO2) on the average thicknesses of Bacillus subtilis biofilm and on bacterial attachment on different surfaces were investigated. The binding mechanism of n-TiO2 to the cell surface was also probed. The results revealed that n-TiO2 caused biofilm dispersal and the thicknesses decreased by 2.0 to 2.6 µm after several hours of exposure. The attachment abilities of bacteria with extracellular polymeric substances (EPS) on hydrophilic surfaces were significantly reduced by 31% and 81% under 10 and 100 mg/liter of n-TiO2, respectively, whereas those of bacteria without EPS were significantly reduced by 43% and 87%, respectively. The attachment abilities of bacteria with and without EPS on hydrophobic surfaces were significantly reduced by 50% and 56%, respectively, under 100 mg/liter of n-TiO2 The results demonstrated that biofilm dispersal can be attributed to the changes in the cell surface structure and the reduction of microbial attachment ability.IMPORTANCE Nanoparticles can penetrate into the outer layer of biofilm in a relatively short period and can bind onto EPS and bacterial surfaces. The current work probed the effects of nanosized TiO2 (n-TiO2) on biofilm thickness, bacterial migration, and surface properties of the cell in the early stage using the surface plasmon resonance waveguide mode. The results demonstrated that n-TiO2 decreased the adhesive ability of both cell and EPS and induced bacterial migration and biofilm detachment in several hours. The decreased adhesive ability of microbes and EPS worked against microbial aggregation, reducing the effluent quality in the biological wastewater treatment process.

Protein corona between nanoparticles and bacterial proteins in activated sludge: Characterization and effect on nanoparticle aggregation.

In this work, the protein coronas of activated sludge proteins on TiO2 nanoparticles (TNPs) and ZnO nanoparticles (ZNPs) were characterized. The proteins with high affinity to TNPs and ZNPs were identified by shotgun proteomics, and their effects of on the distributions of TNPs and ZNPs in activated sludge were concluded. In addition, the effects of protein coronas on the aggregations of TNPs and ZNPs were evaluated. Thirty and nine proteins with high affinities to TNPs and ZNPs were identified, respectively. The proteomics and adsorption isotherms demonstrated that activated sludge had a higher affinity to TNPs than to ZNPs. The aggregation percentages of ZNPs at 35, 53, and 106 mg/L of proteins were 13%, 14%, and 18%, respectively, whereas those of TNPs were 21%, 30%, 41%, respectively. The proteins contributed to ZNPs aggregation by dissolved Zn ion-bridging, whereas the increasing protein concentrations enhanced the TNPs aggregation through macromolecule bridging flocculation.

Occurrence and risk assessment of heavy metals in sediments of the Xiangjiang River, China.

Sediment samples were collected from 22 typical metal-polluted sections along the Xiangjiang River (XJR). Spatial distribution and speciation characteristics of heavy metals in sediments of XJR were determined. Furthermore, ecological risk and enrichment degree of metals were assessed by different indices. The results showed that combined metal pollution occurred in sediments of XJR, with content range of Cd, Pb, Zn, Cu, As, Mn, Cr, and Hg reaching 2.95-29.15, 30.93-235.83, 61.50-3771.11, 9.56-81.81, 3.93-46.28, 774.83-8700.72, 10.64-65.16, and 0.13-5.09 mg kg-1, respectively. Pollution levels increased in period of industrialization but decreased after thousands of pollution enterprises were banned. Sections with serious pollution and higher risk were mainly located at Hengyang and Chang-Zhu-Tan regions (Changsha, Zhuzhou, and Xiangtan) for contaminations of Cd, As, Pb, and Hg. Values of both enrichment factor and geo-accumulation index followed the order Cd > Hg > Zn > Mn > Pb > Cu > As > Cr. Bioavailable fractions followed the order Cd (66.93 %), Zn (33.80 %), Pb (30.81 %), Mn (18.38 %), Hg (17.58 %), Cu (10.20 %), As (9.81 %), and Cr (7.65 %). Considering their bioavailability, biotoxicity, or abundance, contamination of Cd was the most dominant, and pollution of other metals should not be ignored.

Combination of biological pretreatment with NaOH/Urea pretreatment at cold temperature to enhance enzymatic hydrolysis of rice straw.

A stepwise pretreatment of combination of bacterial treatment with NaOH/Urea (NU) treatment was conducted to enhance enzymatic hydrolysis of rice straw (RS). The results showed that the composition of RS changed significantly, the lignin and hemicellulose decreased while cellulose increased. The biological treatment with a bacterium Sphingobacterium sp. LD-1 achieved mild conditions for the sequential NU treatment, reducing the concentration of the NU solution from 7%/12% to 4%/6% and increasing the temperature from -20°C to -10°C. The saccharification of rice straw co-treated with bacterium Sphingobacterium sp. LD-1 and 4%/6% NU at -10°C resulted in 1.396-fold and 1.372-fold increase of reducing sugar and glucose yield respectively than that of sole NU treatment.

Fenton degradation of Cartap hydrochloride: identification of the main intermediates and the degradation pathway.

The advanced oxidation of Cartap hydrochloride (Cartap) promoted by the Fenton system in an aqueous medium was investigated. Based on total organic carbon, chemical oxygen demand and high-performance liquid chromatography, the oxidation of Cartap is quite efficient by the Fenton system. Its long chain is easily destroyed, but the reaction does not proceed to complete mineralization. Ion chromatography detection indicated the formation of acetic acid, propionic acid, formic acid, nitrous acid and sulfuric acid in the reaction mixtures. Further evidence of nitrogen monoxide and sulfur dioxide formation was obtained by using a flue gas analyzer. Monitoring by gas chromatograph-mass spectrometer demonstrated the formation of oxalic acid, ethanol, carbon dioxide, and L-alanine ethylamide. Based on these experimental results, plausible degradation pathways for Cartap mineralization in an aqueous medium by the Fenton system are proposed.

Synthesis and characterization of Ag3PO4 immobilized with graphene oxide (GO) for enhanced photocatalytic activity and stability over 2,4-dichlorophenol under visible light irradiation.

A series of visible-light responsive photocatalysts prepared using Ag3PO4 immobilized with graphene oxide (GO) with varying GO content were obtained by an electrostatically driven method, and 2,4-dichlorophenol (2,4-DCP) was used to evaluate the performance of the photocatalysts. The composites exhibited superior photocatalytic activity and stability compared with pure Ag3PO4. When the content of GO was 5%, the degradation efficiency of 2,4-DCP could reach 98.95%, and 55.91% of the total organic (TOC) content was removed within 60 min irradiation. Meanwhile, the efficiency of 91.77% was achieved for 2,4-DCP degradation even after four times of recycling in the photocatalysis/Ag3PO4-GO (5%) system. Reactive species of O2(˙-), OH˙ and h(+) were considered as the main participants for oxidizing 2,4-DCP, as confirmed by the free radical capture experiments. And some organic intermediates including 4-chlorophenol (4-CP), hydroquinone (HQ), benzoquinone (BZQ), 2-chlorohydroquinone and hydroxyhydroquinone (HHQ) were detected by comparison with the standard retention times from the high performance liquid chromatography (HPLC). In short, the enhanced photocatalytic property of Ag3PO4-GO was closely related to the strong absorption ability of GO relative to 2,4-DCP, the effective separation of photogenerated electron-hole pairs, and the excellent electron capture capability of GO.

[Characteristics and mechanism of 2,4,6-TCP degradation by the "Fe0/enriched-bacteria" system].

The synergistic mechanism of 2, 4, 6-trichlorophenol (TCP) degradation using a combination of Fe0 and anaerobic dechlorinating bacteria with batch processing was investigated. Experimental results showed that under the conditions of pH 7.0, Fe0 5 g x L(-1) and 2,4,6-TCP 30 mg x L(-1), the growth and interface enrichment of enriched-bacteria could be promoted by Fe0, the cell mass (expressed by D600) of Fe0/enriched-bacteria was about 1.7 times as high as that of the individual predominant groups of dechlorinating bacteria. After 96 h reaction, large amount of bacteria attached to the iron surface, with short rod or coccus-like morphology. The pH value of the system was maintained at 7.8, which could be beneficial to the reductive dechlorination reaction and the growth of the enriched-bacteria. The major pathway of 2,4,6-TCP degradation in the Fe0/enriched-bacteria system was 2,4,6-TCP to 2,4-DCP and then to 4-CP.

3D antibody immobilization on a planar matrix surface.

The amount of active capture antibodies immobilized per unit square is crucial to developing effective antibody chips, biosensors, immunoassays and other molecular recognition technologies. In this study, we present a novel yet simple method for oriented antibody immobilization at high density based on the formation of an orderly, organized aggregation of immunoglobulin G (IgG) and staphylococcal protein A (SPA). Following the chelation of His-tag with Ni(2+), antibodies were immobilized on a solid surface in a three-dimensional (3D) manner and exposed the analyte receptor sites well, which resulted in a substantial enhancement of the analytical signal with more than 64-fold increase in detection sensitivity. Pull-down assays confirmed that IgG antibody can only bind to Ni(2+) matrix indirectly via a SPA linkage, where the His-tag is responsible for binding Ni(2+) and homologous domains are responsible for binding IgG Fc. The immobilization approach proposed here may be an attractive strategy for the construction of high performance antibody arrays and biosensors as long as the antibody probe is of mammalian IgG.

How an improved immunoassay sensitivity can be achieved by gamma irradiation: modification, application and characterization of polystyrene surface for anti HIV-1 ELISA.

Polystyrene microtitre plates modified by (60)Co gamma-ray irradiation were used in an indirect enzyme-linked immunosorbent assay (ELISA) for detection of anti-human immunodeficiency virus type 1 (anti HIV-1). The plates with 9 kGy (optimum dose) irradiation showed 2-5-fold higher detection sensitivity in serodiagnosis tests compared to untreated ones, and a 3-fold lower enzyme concentration than the control used was still detectable. Adsorption/desorption experiment results, atomic force microscopy (AFM) images, and X-ray photoelectron spectroscopy (XPS) analysis provide the reason for this improvement. The oxidized surface formed during irradiation presented much more binding affinity for coating antigens and could adsorb a larger amount (1.5-3-fold) of protein uniformly.

A novel affinity ligand for polystyrene surface from a phage display random library and its application in anti-HIV-1 ELISA system.

In order to develop an affinity ligand for site-directed immobilization of target proteins on polystyrene (PS) surface, a linear 12-mer peptide phage display random library was screened. Phage clones that specifically bound to PS plate were sequenced after three rounds of biopanning. The obtained DNA sequences revealed that there were several aromatic and basic amino acid residues, which may be critical to binding. One of the selected dodecapeptides, named Lig1 (FKFWLYEHVIRG), was genetically fused to the N/C-terminus of recombinant antigen ENV which could be recognized by specific antibodies against human immunodeficiency virus type 1 (HIV-1), to investigate its performance as an affinity ligand. The ligand-fused ENVs overexpressed in Escherichia coli were compared to the original one in terms of the immobilization characteristics on PS plate in enzyme-linked immunosorbent assay (ELISA). The results indicated that the ligand-fused proteins showed a considerably improved affinity to PS surface, and were preferentially adsorbed on PS plate suffering only scarcely from interference by coexisting protein molecules. Anti-HIV-1 ELISA system, which employed Lig1-ENV (Lig1 fused to ENV N-terminus) as immobilization antigen also exhibited sufficiently high sensitivity and specificity in serodiagnosis tests.

Removal of bromide by aluminium chloride coagulant in the presence of humic acid.

Bromide can form disinfection by-products (DBPs) in drinking water disinfection process, which have adverse effects on human health. Using aluminium chloride as a model coagulant, removal of bromide by coagulation was investigated in the absence or presence of humic acid (HA) in synthetic water and then was conducted in raw water. Results demonstrated that in synthetic water, 93.3-99.2% removal efficiency of bromide was achieved in the absence of HA with 3-15 mg/L coagulant, while 78.4-98.4% removal efficiency of bromide was obtained in the presence of HA with the same coagulant dosage and 86.8-98.8% HA was removed simultaneously. Bromide in raw water was removed 87.0% with 15 mg/L coagulant. HA apparently reduced the removal of bromide with low coagulant dosage or at high pH, while minor influence on removal of bromide was observed with high coagulant dosage or at low pH. Thus, bromide could be reduced effectively by enhanced coagulation in drinking water treatment.

Mechanism of the enhanced degradation of pentachlorophenol by ultrasound in the presence of elemental iron.

Ultrasound combined with elemental iron (US/Fe(0)) is effective in oxidizing organic contaminants in water. The sonolysis degradation of pentachlorophenol (PCP) was significantly enhanced by a factor of 4.2 with the addition of elemental iron, mainly via reaction with hydroxyl radicals (OH radicals), and the synergistic mechanism of the enhancement in the combined system was investigated. Experiments were performed with (1) sole ultrasonic treatment; (2) ultrasound in presence of iron; (3) ultrasound combined with copper powder as the same particle size as iron powder; (4) ultrasound in presence of Fe(II). It was observed that PCP degradation and OH radicals production were both enhanced in these combined methods, and the pitting on the sonicated iron surface was apparent. These results indicated that the rate enhancements in US/Fe(0) system were attributed to (1) the iron solid effect and the catalysis of Fe(II) produced from corroded-iron with promoting the production of OH radicals; (2) the increased surface area of iron particles by acoustic cavitation with promoting the adsorption process.

The QSPR (quantitative structure-property relationship) study about the anaerobic biodegradation of chlorophenols.

In this study, based on quantum chemical and physicochemical descriptors, by the use of partial least squares analysis, a good prediction quantitative structure-property relationship for the disappearance rate constant (logK) of chlorophenols (CPs) in the anaerobic culture was obtained. It was found that the resonance energy of the two-center term (J), which described the character of the weakest carbon-chlorine bond, played an important role in the reductive chlorine processes, the greater the sizes of CPs molecules, the higher the logK values. Increasing energy of the lowest unoccupied molecular orbital (E(lumo)) values of the CPs lead to decreasing logK values, and CPs with large absolute hardness values tended to have big logK values.