Graphene oxide modified magnetic polyamidoamide dendrimers based magnetic solid phase extraction for sensitive measurement of polycyclic aromatic hydrocarbons.

In this study, graphene oxide modified magnetic polyamidoamine dendrimers (MNPs@PAMAM-G2.0@GO) nanoparticles were successfully prepared by amidation method. The obtained MNPs@PAMAM-G2.0@GO nanocomposites were examined by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM) and transmission electron microscopy (TEM), etc. MNPs@PAMAM-G2.0@GO exhibited excellent adsorption property and was investigated for magnetic solid phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) from water. The detection of extracted PAHs was accomplished by high performance liquid chromatography (HPLC) and gas chromatography tandem mass spectrometry (GC-MS/MS). The target PAHs included anthracene (ANT), pyrene (PYR), fluoranthene (FLT), carbazole (CB), 7-methylquinoline (7-MQL), 9-methylcarbazole (9-MCB), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DBT). Important operation parameters for MSPE that could affect the extraction efficiencies of PAHs were investigated in detail. Under optimal parameters, the constructed method demonstrated excellent linear range with 0.001-10 µg L-1 for analytes and low limits of detection within the range of 0.11-0.9 ng L-1. The spiked average recoveries of PAHs in natural water samples ranged from 92.5% to 105.2%. The promising results indicated that MNPs@PAMAM-G2.0@GO could be employed to efficiently extract PAHs from aqueous samples.

Preparation of Polyamidoamine Dendrimer Modified Magnetic Nanoparticles and Its Application for Reliable Measurement of Sudan Red Contaminants in Natural Waters at Parts-Per-Billion Levels.

The health threat from Sudan red dyes has been the subject of much attention in recent years and is crucial to design and establish reliable measurement technologies. In the present study, a new magnetic nanomaterial, polyamidoamine dendrimer-modified magnetic nanoparticles (Gn-MNPs), was synthesized and characterized. The nanomaterials had good adsorption capacity for Sudan dyes from natural waters. G1.5-MNPs possessed excellent adsorption capacity and a linear adsorption relationship over the range from 0.02 to 300 µg L-1 of Sudan dyes with relative coefficients all larger than 0.996. The sensitivity of the proposed method was excellent with detection limits over the range from 1.8 to 5.5 ng L-1 and the precision was less than 3.0%. G1.5-MNPs showed a remarkable application potential for the enrichment of trace environment pollutants in aqueous samples and the developed method based on this nanomaterial could be a robust and reliable alternative tool for routine monitoring of such pollutants.

Selective detection of Cu2+ using nitrogen-doped carbon dots derived from humic acid and urea based on specific inner filter effect.

A new kind of nitrogen-doped carbon dots (N-CDs) was synthesized via a simple hydrothermal strategy using humic acid as the carbon source and urea as the nitrogen source. The fluorescence intensity of as-prepared N-CDs was quenched significantly in presence of Cu2+ based on a specific inner filter effect, which could be utilized to construct a selective sensor for monitoring Cu2+ in aqueous samples. The sensor exhibited good linearity over the range of 0.1-2 µM, and high sensitivity with a detection limit of 25 nM. Under the optimal conditions, there was no significant interference by other metal ions such as Cd2+, Al3+, Cr3+, Fe3+, Pb2+, Na+, Ni+, Fe2+, Ba2+, Ca2+, Co2+, Mg2+, As3+, K+, Zn2+ for Cu2+ detecting except Hg2+.The interference of Hg2+ can be masked by addition of sodium chloride. The experimental results demonstrated that the prepared N-CDs owned strong fluorescence, high monodispersity, good stability and good water solubility, and the constructed sensor had many advances and great application prospect in environmental field.

Sensitive detection of 2,4,6-trinitrotoluene utilizing fluorescent sensor from carbon dots and reusable magnetic core-shell nanomaterial.

Carbon dots have been a promising nano-carbon material with many advantages, and attracted many more attentions. This study designed a new chemosensor integrating the strong fluorescent property of carbon dots and the magnetism of amino-functionalized magnetic core-shell nanomaterial, Fe@SiO2-NH2 for determination of 2,4,6-trinitrotoluene (TNT). In this system, fluorescent carbon dots interacted with amino groups on the surface of amino-functionalized magnetic core-shell nanomaterial leading to fluorescence quenching of carbon dots, appearance of TNT competitively replaced of carbon dots on the surface of the magnetic material through forming a Meisenheimer complex. This sensor exhibits excellent selectivity and sensitivity for TNT, and which provided a good dynamic linear range for TNT from 10 to 2000 ng mL-1. The experiments demonstrate a low detection limit of 2.15 ng mL-1. The intra-day precisions for 25, 100 and 500 ng mL-1 were 4.6, 2.3 and 0.5% (RSD, n = 6), inter-day precisions for 25, 100 and 500 ng mL-1 were 4.2, 2.5 and 0.9% (RSD, n = 6), respectively. The developed sensor was validated with river water, dust, and soil samples, and the achieved spiked recoveries were immensely satisfied from 98.1% to 102.0%. The Fe@SiO2-NH2 possessed excellent reusability. This sensor exhibits that it is simple, sensitive and selective, and will be a vital analytical tool for TNT in many fields.

Alkaline thermal pretreatment of waste activated sludge for enhanced hydrogen production in microbial electrolysis cells.

Resource utilization of waste activated sludge (WAS) has become a mainstream development direction. Alkaline thermal pretreatment (TPT) was found to greatly promote the bioaccessibility and biodegradability of the sludge. The organic matter including soluble chemical oxygen demand (SCOD), soluble carbohydrate, soluble protein and volatile fatty acids (VFAs) after low temperature (90 °C) pretreatment was 4.8%-65.9% higher than that after high temperature (180 °C) pretreatment. These increasements could be contributed by the alkaline treatment condition and the longer treatment time. The alkaline condition reduced the resistance of cell wall to the temperature. The pretreatment time at 90 °C was two times of that at 180 °C, allowing more organic matter to be released. But the total energy consumption of low temperature pretreatment (2580.7 kJ/L) was 30.5% lower than that of high temperature pretreatment (3711.8 kJ/L). The sludge fermentation liquid (SFL) was then employed as the substrate in microbial electrolysis cells (MECs), and the utilization efficiency of acetic acid was the highest (74.9%-83.2%). The hydrogen yield using low temperature pretreated sludge was 0.44 m3/(m3·d), which was higher than that of using high temperature pretreated sludge (0.31 m3/(m3·d)). These results suggested that alkaline TPT at 90 °C was an effective way to hydrolyze sludge and further enhance hydrogen production in MECs.

Characteristics of bacterial populations in an industrial scale petrochemical wastewater treatment plant: Composition, function and their association with environmental factors.

The efficiency of petrochemical wastewater biological treatment is dependent upon complex bacterial communities. A well understanding of the structure and function of bacterial community and their association with environmental variables is essential for the elucidation of contaminant removal mechanisms and optimization of wastewater treatment processes. In this study, the bacterial communities and metabolic functions in the primary hydrolysis acidification unit (PHAU), cyclic activated sludge system (CASS), secondary hydrolysis acidification unit (SHAU), and biological aerated filter (BAF) of a petrochemical wastewater treatment plant (WWTP) were studied via Illumina high-throughput sequencing. The correlations between bacterial community and environmental variables were also investigated. The phylum Proteobacteria, Planctomycetes, Chloroflexi, Acidobacteria and Bacteroidetes were dominant in the petroleum WWTP. The bacterial communities varied with wastewater characteristics and operational parameters, as a result of the differences in biosystems functions. Phylogenetic analysis showed that the genes involved in the degradation of benzoate, nitrotoluene and aminobenzoate degradation were abundant in PHAU, and the genes related to the degradation of benzoate, aminobenzoate, chloroalkane, chloroalkene, caprolactam, naphthalene and toluene were abundant in CASS, SHAU and BAF. The Redundancy analysis (RDA) suggested that biochemical oxygen demand (BOD5), NH4+-N and total nitrogen concentrations exhibited significant impacts in shaping the structure of bacterial community. Variance partitioning analysis (VPA) showed that 18.6% of the community variance was related to wastewater characteristics, higher than operational parameters of 4.5%. These results provide insight into microbial community structure and metabolic function during petrochemical wastewater treatment, and discern the relationships between bacterial community and environmental variables, which can provide basic data and a theoretical analysis of the design and operation optimization in petrochemical WWTP.

Comprehensive chemical analysis and characterization of heavy oil electric desalting wastewaters in petroleum refineries.

Large quantities of highly polluted point-source wastewaters (EDWs) are generated from electric desalting process of heavy oils (HOs), resulting in severe impacts on the efficiency of wastewater treatment plants in petroleum refineries. In the present study, a comprehensive chemical analysis and characterization of EDWs of two typical Chinese heavy oils, Liaohe heavy oil (LHO) and Karamy heavy oil (KHO), were investigated using Daqing light oil (DLO) as a control. The HO-EDWs (LHO-EDW and KHO-EDW) show high pollutants contents with complicated compositions, more polar dissolved organic pollutants (DOPs), strong emulsion stability and high acute biotoxicity towards Vibrio fischeri, compared to DLO-EDW. LHO-EDW and KHO-EDW have nearly equal pollutants contents but different compositions and distributions, where more types of DOPs exist in KHO-EDW. Large amounts of biologically recalcitrant aromatic compounds, as well as heteroatomic compounds such as CHO, CHOS and CHON species, extensively distribute in HO-EDWs. The organic nitrogen compounds (e.g., anilines and N2-3Ox, N1OxS1) in KHO-EDW most probably contribute to and thus leading to elevated levels of acute biotoxicity. Additionally, highly dispersed colloidal, micron-sized particles and polar compounds promote the emulsification and stabilization of HO-EDWs. These results can guide the development of pretreatment technologies for HO-EDWs, thus improving the treatment and management of heavy oil refineries' wastewater streams.

Catalytic Ozonation of Nitrobenzene by Manganese-Based Y Zeolites.

Catalytic ozonation process (COP) is considered as a cost-efficient technology for the treatment of refractory chemical wastewaters. The catalyst performance plays an important role for the treatment efficiency. The present study investigated efficiencies and mechanisms of manganese (Mn)-based Y zeolites in COPs for removing nitrobenzene from water. The catalysts of Mn/NaY and Mn/USY were prepared by incipient wetness impregnation, while Mn-USY was obtained by hydrothermal synthesis. Mn-USY contained a greater ratio of Mn2+ than Mn/NaY, and Mn/USY. Mn oxides loaded on Y zeolites promoted the COP efficiencies. Mn/NaY increased total organic carbon removal in COP by 7.3% compared to NaY, while Mn/USY and Mn-USY increased 11.5 and 15.8%, respectively, relative to USY in COP. Multivalent Mn oxides (Mn2+, Mn3+, and Mn4+) were highly dispersed on the surface of NaY or USY, and function as catalytic active sites, increasing mineralization. Mn-USY showed the highest total organic carbon removal (44.3%) in COP among the three catalysts, because Mn-USY had a higher ratio of Mn2+ to the total Mn oxides on the surface than Mn/NaY and Mn/USY and the catalytic effects from intercorrelations between Mn oxides and mesoporous surface structures. The hydroxyl radicals and superoxide radicals governed oxidations in COP using Mn-USY. Nitrobenzene was oxidized to polyhydroxy phenol, polyhydroxy nitrophenol, and p-benzoquinone. The intermediates were then oxidized to small organic acids and ultimately carbon dioxide and water. This study demonstrates the potential of Y zeolites used in COP for the treatment of refractory chemical wastewaters.

Enrichment and sensitive determination of phthalate esters in environmental water samples: A novel approach of MSPE-HPLC based on PAMAM dendrimers-functionalized magnetic-nanoparticles.

Phthalate esters (PAEs) are an important kind of environmental endocrine disrupting chemicals, and have attracted great attention in environmental field. Present study described a new method for rapid and sensitive determination of PAEs including dibenzyl phthalate (DPhP), dibutyl phthalate (DnPP), and dicyclohexyl phthalate (DCHP) from aqueous matrices based on magnetic solid-phase extraction. Polyamidoamine (PAMAM) dendrimers-grafted magnetic-nanoparticles were synthesized and characterized, and the expected integration of more multifunctional sites of PAMAM dendrimers and rapid separation property was utilized for method development. To achieve the best extraction efficiency, several important parameters were optimized including the dosage of the adsorbent, sample pH, kind and volume of eluent, extraction time, desorption time, ionic strength. Under the optimal conditions, three phthalate esters were well enriched and simultaneously determined by high performance liquid chromatography with variable wavelength detector (VWD). Excellent linearities were observed in the range of 0.1-600 µg L-1 for DPhP and DnPP and 0.5-600 µg L-1 for DCHP, and all correlation coefficients (R2) were larger than 0.997. The limits of detection (LODs, S/N = 3) were ranged from 0.025 to 0.16 µg L-1. The spiked recoveries of PAEs in real water samples were in the range of 93.5-101.8% with satisfied relative standard deviations (RSDs) ranging from 0.9 to 4.1%. The prepared magnetic materials have shown good adsorption capability for PAEs and the developed method earned merits such as high sensitivity, simplicity, rapidness and environmental friendliness, which can be used as a robust alternative tool for monitoring PAEs in water samples.

Preparation of magnetic core-shell Fe3O4@polyaniline composite material and its application in adsorption and removal of tetrabromobisphenol A and decabromodiphenyl ether.

Present study described a magnetic adsorption and removal method with prepared magnetic core-shell Fe3O4@polyaniline microspheres for the removal of two typical BFRs, tetrabromobisphenol-A (TBBPA) and decabromodiphenyl ether (BDE-209) from water samples. Magnetic core-shell Fe3O4@polyaniline microspheres were prepared by a hydrothermal and two step polymerization method with cheap iron salts and aniline, which were characterized with transmission electron microscopic (TEM) and scanning electron microscopy (SEM). The results showed that the Fe3O4@polyaniline microspheres earned a clear thickness shell of polyaniline (about 50 nm) and a saturation magnetization of 40.4 emu g-1. The Magnetic core-shell Fe3O4@polyaniline exhibited excellent adsorption capability and removal rate to TBBPA and BDE 209. The adsorption of TBBPA and BDE 209 all followed pseudo-second order kinetics and agreed well to the Freundlich adsorption isotherms model. The negative Gibbs free energy change (ΔG0) and positive standard enthalpy change (ΔH0) for TBBPA and BDE-209 suggested that the adsorption was spontaneous and endothermic in nature. These results demonstrated that Fe3O4@PANI was a good adsorbent and would have a good application prospect in the removal of pollutants from environmental water.

Efficiencies and mechanisms of ZSM5 zeolites loaded with cerium, iron, or manganese oxides for catalytic ozonation of nitrobenzene in water.

Discharge of industrial wastewater causes water pollution. It is therefore necessary to treat wastewater prior to discharge. Catalytic ozonation processes (COP) using ZSM5 zeolites loaded with metallic (Ce, Fe, or Mn) oxides to remove nitrobenzene from water were investigated. The total organic carbon (TOC) removal by the COP treatment with NaZSM5-38, HZSM5-38, and NaZSM5-100 were increased by 6.7%, 23.1%, and 19.8%, respectively, in comparison with single ozonation efficiency (39.2%). The loadings of Ce, Fe, or Mn oxides increased the catalytic activity relative to ZSM5 zeolites alone. The Ce loaded material (Ce/NaZSM5-38) had the highest TOC removal (86.3%). The different-metallic-oxides loaded zeolites exhibited different chemical processes during the removal of nitrobenzene from water. During COP treatment, NaZSM5-38 zeolites removed nitrobenzene mainly via OH mediated oxidation. HZSM5-38 and NaZSM5-100 zeolites showed powerful adsorption toward nitrobenzene. Both adsorption and direct ozonation contribute the TOC removal in their early uses. The OH mediated oxidation dominates the TOC removal process as the adsorption became saturated after multiple uses. Surface SiO bonds and/or SiO(H)Al structures are the active sites for ZSM5 zeolites. Efficient surface dispersion of the metallic oxides enhances the catalytic activity. This study shows the high potentials of ZSM5 zeolites as catalysts in COP to efficiently treat refractory wastewaters.

Characterization and purification of anthocyanins from black peanut (Arachis hypogaea L.) skin by combined column chromatography.

Black peanut skins as a byproduct from peanut industry contain abundant anthocyanins, evaluated as 8.61±0.27mg/g dry black peanut skins, are currently poorly exploited. In this work, four anthocyanins and three major flavonols were detected and identified by HPLC-PDA-ESI-MS/MS from the acidified water extract of black peanut skins of Arachis hypogaea L. After preliminary removal of flavonols by ethyl acetate (EtOAc), further purification of the anthocyanins was conducted using a combination of Amberlite XAD-7HP and ODS-AQ-HG column chromatography methods. Two most abundant monomeric anthocyanins cyanidin-3-O-sophoroside (5.77±0.42mg) and cyanidin-3-O-sambubioside (4.10±0.17mg) were eventually obtained from 2g dry black peanut skins, and their purities were determined by HPLC-PDA as 97.29% and 98.28% at the yields of 87.47% and 64.27% on the basis of their total amount in the crude extracts, respectively. These sequential treatments can be easily adapted to large-scale fractionation of pure anthocyanin monomers.

Evaluation of an up-flow anaerobic sludge bed (UASB) reactor containing diatomite and maifanite for the improved treatment of petroleum wastewater.

Novel diatomite (R1) and maifanite (R2) were utilized as support materials in an up-flow anaerobic sludge bed (UASB) reactor for the treatment of recalcitrant petroleum wastewater. At high organic loadings (11kg-COD/m3·d), these materials were efficient at reducing COD (92.7% and 93.0%) in comparison with controls (R0) (88.4%). Higher percentages of large granular sludge (0.6mm or larger) were observed for R1 (30.3%) and R2 (24.6%) compared with controls (22.6%). The larger portion of granular sludge provided a favorable habitat that resulted in greater microorganism diversity. Increased filamentous bacterial communities are believed to have promoted granular sludge formation promoting a conductive environment for stimulation methanogenic Archaea. These communities had enhanced pH tolerance and produced more methane. This study illustrates a new potential use of diatomite and maifanite as support materials in UASB reactors for increased efficiency when treating refractory wastewaters.

Potential of wheat bran to promote indigenous microbial enhanced oil recovery.

Microbial enhanced oil recovery (MEOR) is an emerging oil extraction technology that utilizes microorganisms to facilitate recovery of crude oil in depleted petroleum reservoirs. In the present study, effects of wheat bran utilization were investigated on stimulation of indigenous MEOR. Biostimulation conditions were optimized with the response surface methodology. The co-application of wheat bran with KNO3 and NH4H2PO4 significantly promoted indigenous MEOR (IMEOR) and exhibited sequential aerobic (O-), facultative (An-) and anaerobic (A0-) metabolic stages. The surface tension of fermented broth decreased by approximately 35%, and the crude oil was highly emulsified. Microbial community structure varied largely among and in different IMEOR metabolic stages. Pseudomonas sp., Citrobacter sp., and uncultured Burkholderia sp. dominated the O-, An- and early A0-stages. Bacillus sp., Achromobacter sp., Rhizobiales sp., Alcaligenes sp. and Clostridium sp. dominated the later A0-stage. This study illustrated occurrences of microbial community succession driven by wheat bran stimulation and its industrial potential.