Catalytic Degradation of Ciprofloxacin in Aqueous Solution by Peroxymonosulfate Activated with a Magnetic CuFe2O4@Biochar Composite.

A magnetic copper ferrite and biochar composite (CuFe2O4@BC) catalyst was prepared by an improved sol-gel calcination method and initially used for the removal of antibiotics ciprofloxacin (CIP) by activated peroxymonosulfate (PMS). Using CuFe2O4@BC as the activator, 97.8% CIP removal efficiency could be achieved in 30 min. After a continuous degradation cycle, CuFe2O4@BC catalyst still exhibited great stability and repeatability and could also be quickly recovered by an external magnetic field. Meanwhile, the CuFe2O4@BC/PMS system presented good stability for metal ion leaching, which was far less than the leaching of metal ions in the CuFe2O4/PMS system. Moreover, the effects of various influencing factors, such as initial solution pH, activator loading, PMS dosage, reaction temperature, humic acid (HA), and the inorganic anions were explored. The quenching experiments and the electron paramagnetic resonance (EPR) analysis manifested that hydroxyl radical (•OH), sulfate radical (SO4•-), superoxide radical (O2•-), and singlet oxygen (1O2) were generated in the CuFe2O4@BC/PMS system, while 1O2 and O2•- are mainly involved in the degradation process. The synergistic effect between CuFe2O4 and BC enhanced the structural stability and electrical conductivity of the material, which promoted the bonding between the catalyst and PMS, resulting in the enhanced catalytic activity of CuFe2O4@BC. This indicates that CuFe2O4@BC activating PMS is a promising remediation technique for CIP-contaminated water.

Synthesis of an Environmentally Friendly Modified Mulberry Branch-Derived Biochar Composite: High Degradation Efficiency of BPA and Mitigation of Toxicity in Silkworm Larvae.

In the present study, mulberry branch-derived biochar CuO (MBC/CuO) composite was successfully synthesized and used as a catalyst to activate persulfate (PS) for the degradation of bisphenol A (BPA). The MBC/CuO/PS system exhibited a high degradation efficiency (93%) of BPA, under the conditions of 0.1 g/L MBC/CuO, 1.0 mM PS, 10 mg/L BPA. Free radical quenching and electron spin-resonance spectroscopy (ESR) experiments confirmed that both free radicals •OH, SO4•- and O2•- and non-radicals 1O2 were involved in the MBC/CuO reaction system. Cl- and NOM displayed negligible influence on the degradation of BPA, while HCO3- promoted the removal of BPA. In addition, the toxicity tests of BPA, MBC/CuO and the degraded BPA solution were conducted by the 5th instar silkworm larvae. The toxicity of BPA was reduced after the treatment in the MBC/CuO/PS system, and no obvious toxicity of the synthesized MBC/CuO composite was found in the toxicity evaluation experiments. This work provides a new value-added utilization of mulberry branches as a cost-effective and environmentally friendly PS activator.

Activation of peroxymonosulfate by pyrophosphate for the degradation of AO7 at neutral pH.

In the present study, pyrophosphate (PP) was used to activate peroxymonosulfate (PMS) for acid orange 7 (AO7) removal under neutral pH conditions. The removal rate of AO7 (20 mg/L) was 84% within the reaction time with a rate constant value of 0.0165 min-1 under optimum conditions. Additionally, the effects of the concentrations of PMS and PP in solutions with various pH values and the coexisting inorganic anions on AO7 removal were measured. In addition, the performance of phosphate (P(V)) on PMS activation was compared with that of phosphite (P(III)) species. In contrast to P(III), the concentration of P(V) showed a positive correlation with the efficiency of AO7 decolorization. PMS activation in different types of buffer solutions was also examined, and the results indicated that the decolorization efficiency of AO7 induced by PP addition, and the buffer solution also contributed to PMS self-decomposition. Singlet oxygen (1O2) might be the primary reactive oxygen species (ROS) in the PP/PMS system in which AO7 is decolorized at an initial pH of 7.06, as indicated by quenching experiments and electron spin resonance (ESR) tests. Therefore, PP/PMS systems may be promising technologies for removing organic contaminants, particularly for PP-rich electroplating wastewater.

Activation of peroxymonosulfate by calcined electroplating sludge for ofloxacin degradation.

Developing cost-effective metal/metal oxides for peroxymonosulfate (PMS) activation remains a key issue in the sulfate radical based advanced oxidation process. In this work, electroplating sludge (ES), a transition metal-rich byproduct, was anaerobic calcined and characterized. Then, calcined electroplating sludge (CES) was applied as PMS activator for degradation of ofloxacin (OFL) and CES/PMS system exhibited a nearly 90% of OFL removal in 60 min. In addition, effect of CES, PMS, the initial pH and water constituents (chloride, bicarbonate, natural organic matter (NOM) and water backgrounds) on OFL degradation were systematically studied. Moreover, radical quenching tests and electron spin-resonance spectroscopy studies manifested that both SO4- and HO were the ruling reactive oxygen species. X-ray photoelectron spectroscopy results of the fresh and used CES demonstrated that the PMS activation mainly occur in the transformation from Fe3+ (Cu2+) to Fe2+ (Cu+). Furthermore, liquid chromatography coupled with ion trap time-of-flight mass spectrometry was used to illustrate the possible degradation pathway of OFL. Moreover, CES showed excellent stability and reusability during reaction. This work points out a new way for value-added reuse for ES as a cost-efficient activator of PMS for organic contaminant removal.

Activation of peroxymonosulfate by phosphite: Kinetics and mechanism for the removal of organic pollutants.

In this study, phosphite (HPO32-) was used as a novel activator to activate peroxymonosulfate (PMS) for acid orange 7 (AO7) removal. Under the optimized conditions, the decolorization efficiency of AO7 was 82.1% within 60 min with rate constant values (kobs) of 0.0301 min-1. Besides, effects of the solution pH and the co-existing inorganic anions including Cl-, HCO3-, HPO42- and SO42- on AO7 removal were also investigated. Except for SO42-, other examined co-existing inorganic anions displayed favorable effects on the removal of AO7. Furthermore, the mechanism for PMS activation by the HPO32- was deeply elucidated by radical scavenger including ethanol (EtOH), tert-butanol (TBA), l-histidine and tiron, and electron spin resonance (ESR) studies. It was proposed that singlet oxygen (1O2) would be the dominant reactive oxygen species (ROS) in the HPO32-/PMS system for contamination degradation at neutral pH condition. The findings of this study provided useful information for the application of the substances in industrial wastewaters to activate PMS for organic contaminants degradation and in particular for HPO32--rich electroplating wastewater treatment.

Facile preparation of 3D GO with caffeic acid for efficient adsorption of norfloxacin and ketoprofen.

In this paper, a simple and green method was developed to fabricate a three-dimensional (3D) graphene-based material with the assistance of caffeic acid (CA). The prepared 3D graphene displayed fast and high sorption for norfloxacin (NOR) and ketoprofen (KP). Their adsorption equilibrium was achieved within 12 h for NOR and KP, which was attributed to their fast diffusion in the porous structure of the 3D graphene. The maximum adsorbed amount of this adsorbent was 220.99 mg/g for NOR and 125.37 mg/g for KP according to the Langmuir model at pH 6.6, 298 K. In the competitive adsorption of six pharmaceuticals, the organic compounds in the form of cations are preferentially adsorbed on the adsorbent. The co-existing organic compounds in the actual wastewater do not seriously inhibit the adsorption of NOR and KP. This study provides the theoretical basis for the facile and low-cost preparation of high-performance 3D graphene adsorbents. The results of this study demonstrate the potential utility of 3D graphene as a very effective adsorbent for pharmaceuticals removal from contaminated water.

Long-term effects of chlorothalonil on microbial denitrification and N2O emission in a tea field soil.

Pesticide chlorothalonil is widely applied in tea agroecosystem, potentially disturbing soil microbial-mediated nitrogen cycle. The underlying toxicity mechanism, however, is not well explored. Here, we investigated the long-term effects of chlorothalonil on soil microbial denitrification and N2O emission pattern in a tea field after 40 days of exposure. Results showed that chlorothalonil inhibited denitrification process but remarkably promoted N2O emission by 380-830%. Chlorothalonil significantly inhibited N2O reductase activity but did not affected nosZ abundance. Our results further revealed that chlorothalonil influenced soil denitrification by directly suppressing microbial electron transport system activity, and decreasing electron donor nicotinamide adenine dinucleotide (NADH) and energy source adenosine triphosphate (ATP) levels. Additionally, chlorothalonil also downregulated denitrifying functional genes (narG, nirS, and norB) and declined the relative abundances of potential denitrifiers (i.e., Pseudomonas and Streptomyces). Stepwise regression and path modeling suggested that nitrate reductase was the most significant factor in explaining denitrification rate under chlorothalonil applications. This study provides important information for revealing the chronic impacts of pesticide on tea soil denitrification and N2O emission on the basis of electron transport mechanism. Most significantly, N2O emission is underestimated in chlorothalonil-treated soils, which suggests that future estimations of N2O emission from agricultural lands should take account of pesticide dependency conditions.

How microplastics affect chiral illicit drug methamphetamine in aquatic food chain? From green alga (Chlorella pyrenoidosa) to freshwater snail (Cipangopaludian cathayensis).

The biological impacts of microplastics on many organisms have been well documented. However, the combined effects of microplastics and chiral chemicals on the aquatic food chain are less clear. In the present study, the enantioselective environmental behaviors of methamphetamine co-exposed with microplastics through an aquatic food chain (from Chlorella pyrenoidosa to Cipangopaludian cathayensis) have been investigated in a laboratory environment. It was found that the acute toxicity of methamphetamine against these two species was significantly increased in the presence of microplastics: Chlorella pyrenoidosa showed an EC50 shift from 0.77 to 0.32 mg L-1, while cipangopaludian cathayensis showed an LC50 shift from 4.15 to 1.48 mg L-1, upon the addition of microplastics as a co-contaminant with methamphetamine. Upon exposure to methamphetamine and microplastics, the oxidative damage of algae (19.9 to 36.8 nmol mgprot-1), apoptosis (increase about 2.17 times) and filtration rate (41.2 to 65.4 mL h-1) of snails were observably higher when compared to exposure to methamphetamine alone. After ingestion and accumulation of microplastics, the enantioselectivity, BCFs, BMFs, and distribution of methamphetamine were significantly altered. These results provide evidence that the co-occurrence of microplastics and the chiral drug methamphetamine may increase the burden on aquatic species, with potential further impacts throughout aquatic food chain.

Automated online solid-phase extraction liquid chromatography tandem mass spectrometry investigation for simultaneous quantification of per- and polyfluoroalkyl substances, pharmaceuticals and personal care products, and organophosphorus flame retardants in environmental waters.

This work describes development of a quick and accurate online solid-phase extraction (SPE) liquid chromatography tandem mass spectrometry method for simultaneous determination of 87 emerging organic compounds, including 22 per- and polyfluoroalkyl substances, 58 pharmaceuticals and personal care products, and 7 organophosphorus flame retardants, in diverse water matrices. Considering the wide range of physicochemical properties for the target contaminants, efficient analysis in one injection is challenging. Thus, key extraction and analytical parameters, including online SPE sorbent, mobile phase additives, sample pH, loading solvent pH and composition, injection volume, and valve-switching time, were systematically optimized. The final conditions, namely a polymeric reversed-phase column with alkaline samples and an acidic loading solvent, provided satisfactory results for all target analytes compared to conventional methods that employ acidic samples for multi-residue analysis. The method detection limits (MDLs) ranged from 0.16 to 5.13 ng L-1 with 85% of MDLs lower than 2 ng L-1 for sample volumes of just 1.8 mL. The method also demonstrated satisfactory accuracy with 82% of analytes exhibiting 70-130% recovery. Importantly, only 30 min was required per sample. The optimized method was successfully applied to investigate the removal efficiency of emerging contaminants in a drinking water treatment plant and to analyze the environmental occurrence of target analytes. The method is sensitive, reliable, labor-saving, and cost effective, and therefore has the potential to advance large-scale environmental monitoring programs.

Enhancement of the degradation ability for organic pollutants via the synergistic effect of photoelectrocatalysis on a self-assembled perylene diimide (SA-PDI) thin film.

A self-assembled perylene diimide (SA-PDI) film was prepared on an indium-tin-oxide (ITO) substrate and acted as a photoanode for the photoelectrocatalytic (PEC) degradation of some emerging contaminants under visible light irradiation (λ > 420 nm) and applied voltage. Due to the synergistic effect, the photocatalytic degradation rate by the SA-PDI film under visible light irradiation and an applied voltage of 2.1 V was 2.72 times and 14.5 times those of the PC and EC processes, respectively. The visible light irradiation not only generated a promoting effect on electrocatalytic (EC) oxidation at potentials above 1.2 V but also generated many more h+ for promoting the electrocatalytic oxidation of phenol. Furthermore, an applied voltage above 1.2 V could effectively improve the separation rate of electrons from the SA-PDI electrodes to the Pt electrodes, and then, much more O2- and OH could be generated for improving the photocatalytic (PC) oxidation efficiency. Therefore, the h+, OH and O2- could improve the synergistic effect of phenol oxidation during the PEC process. Moreover, the SA-PDI film appeared to have satisfactory stability in the PEC process. The SA-PDI film was also proven to be effective for two other contaminants, namely, 2,4-dichlorophenol, and ciprofloxacin.

Organophosphate flame retardants in leachates from six municipal landfills across China.

With the phasing out of brominated flame retardants, organophosphate flame retardants (OPFRs) have been widely used and further detected in multiple environmental media. However, municipal landfill leachates, an important source of contamination of OPFRs to aquatic environment, have not been fully understood, especially in a developing country like China. Thus, the occurrence, aqueous removal efficiency, environmental emission, and risk assessment of 10 OPFRs were investigated in leachates from six municipal landfills across China. The results indicated that except triethyl phosphate (TEP), the remaining 9 OPFRs were detected in both raw and final leachates with different frequencies higher than 33.3%. The range of total concentrations of OPFRs (ΣOPFRs) across China was 29.0-437 and 0.652-32.4 µg L-1 in raw and final leachates, respectively. Tris(2-chloroethyl) phosphate (TCEP) was the dominant species and accounted for 78.5% and 85.8% of average ΣOPFR concentration in raw and final leachates, respectively. This may be because TCEP is the most prevalently used OPFR in China. The overall aqueous removal efficiency of ΣOPFRs across China ranged from 57.7% to 99.8%. Tris(2-butoxyethyl) phosphate was the most removed species (98.8%), whereas TCEP was the least removed species (91.5%). The annual emissions of ΣOPFRs discharged into the aquatic environment from municipal landfills across China were estimated to be between 170 and 7094 g. Further risk assessment based on risk quotient values in the final leachates showed that most OPFRs posed negligible risk except TCEP (medium and high risk) and tributyl phosphate (medium risk).

Highly efficient nitrate removal in a heterotrophic denitrification system amended with redox-active biochar: A molecular and electrochemical mechanism.

Biochar is widely used in water treatment because of its porous structure, however, the effects of biochars on denitrification remain unclear. Here, we combined molecular biological and electrochemical techniques to investigate effects of biochars (formed at 300 °C, 500 °C and 800 °C) on denitrification. Results showed that biochar at 300 °C increased total nitrogen removal by 415% and decreased N2O accumulation by 78%. Mechanistic research demonstrated that it achieved the highest electron transfer efficiency and denitrifying enzyme activities. Further study evidenced that biochar at 300 °C increased the abundance of denitrifiers such as Pseudomonas. Correlation analysis indicated that nitrate reductase and nitrite reductase activities were the key factors influenced by biochar during denitrification. Overall, this study suggested that biochar at 300 °C could act as the bio-engineer of electron shuttle and the stimulator of denitrification, achieving high rate nitrogen removal and significant reduction of N2O accumulation from high-strength wastewater.

Highly sensitive and selective determination of Hg(II) based on microfluidic chip with on-line fluorescent derivatization.

In this study, a convenient, sensitive, rapid and simple method was developed on microfluidic chip which was integrated with on-line complexing and laser-induced fluorescence detection. A rhodamine derivative (RD) was developed as a fluorescent chemosensor for Hg(II). It exhibited high selective recognition toward Hg(II) over other examined metal ions in water samples. Under the optimized conditions, the response was linearly proportional to the concentration of Hg(II) in the range of 0-70 µM with a detection limit of 0.031 µM. Satisfactory repeatability and reproducibility were achieved, with a relative standard deviation (RSD) of 6.62%. The established method was successfully applied for the determination of Hg(II) in environmental water samples (surface water, tap water, and waste water). Recoveries obtained for the determination of Hg(II) in spiking samples ranged from 85% to 103%.

Magnetic solid-phase extraction for the analysis of bisphenol A, naproxen and triclosan in wastewater samples.

Magnetic Fe3O4 graphene oxide nanocomposite was synthesized by chemical coprecipitation method and characterized by scanning electron microscopy, Fourier transform infrared spectra and X-ray diffraction. A simple, rapid, convenient and environmentally friendly method was developed for separation and pre-concentration of trace amounts of bisphenol A, naproxen and triclosan in wastewater samples by high performance liquid chromatography with magnetic Fe3O4 graphene oxide nanocomposite as the adsorbent for magnetic solid-phase extraction. Various parameters possibly influencing the extraction performance such as amount of the adsorbent, extraction time, sample pH and elution conditions were optimized. Under the optimal working conditions, the developed method showed good linearity (R > 0.9997) in the range of 1-200 µg/L, and the limits of detection are between 0.5 and 0.8 µg/L. The enrichment factors are in the range of 81-89. The repeatability of the method, expressed as relative standard deviation, is 3.36-4.26%.

Ultra-fast vapor generation by a graphene nano-ratchet: a theoretical and simulation study.

Vapor generation is of prime importance for a broad range of applications: domestic water heating, desalination and wastewater treatment, etc. However, slow and inefficient evaporation limits its development. In this study, a nano-ratchet, a multilayer graphene with cone-shaped nanopores (MGCN), to accelerate vapor generation has been proposed. By performing molecular dynamics simulation, we found that air molecules were spontaneously transported across MGCN and resulted in a remarkable pressure difference, 21 kPa, between the two sides of MGCN. We studied the dependence of the pressure difference on the ambient temperature and geometry of MGCN in detail. Through further analysis of the diffusive transport, we found that pressure difference depended on the competition between ratchet transport and Knudsen diffusion and it was further found that ratchet transport is dominant. The significant pressure difference could lead to a 15-fold or greater enhancement of vapor generation, which shows the wide applications of this nano-ratchet.

Flow injection microfluidic device with on-line fluorescent derivatization for the determination of Cr(III) and Cr(VI) in water samples after solid phase extraction.

In this paper, a rapid and simple method using magnetic multi-walled carbon nanotubes (MWCNTS), as a solid-phase extraction (SPE) sorbent, was successfully developed for extraction and preconcentration trace amounts of Cr(III) in water samples. The synthesized magnetic-MWCNTs nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). A rhodamine derivative (R1) was synthesized and characterized as a highly selective and sensitive fluorescent derivatizing agent for Cr(III). After SPE procedure, Cr(III) analysis was performed by flow injection microfluidic chip with on-line fluorescent derivatization and laser-induced fluorescence (LIF) spectroscopy detection. The parameters, which affected the efficiency of the developed method were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0-10.0 nM, with a detection limit of 0.094 nM and an enrichment factor of 38. Furthermore, real water samples were analyzed and good recoveries were obtained from 91.0 to 101.6%.

Determination of organophosphorus pesticides and their major degradation product residues in food samples by HPLC-UV.

A simple method based on dispersive solid-phase extraction (DSPE) and dispersive liquid-liquid microextraction method based on solidification of floating organic droplets (DLLME-SFO) was developed for the extraction of chlorpyrifos (CP), chlorpyrifos-methyl (CPM), and their main degradation product 3,5,6-trichloro-2-pyridinol (TCP) in tomato and cucumber samples. The determination was carried out by high performance liquid chromatography with ultraviolet detection (HPLC-UV). In the DSPE-DLLME-SFO, the analytes were first extracted with acetone. The clean-up of the extract by DSPE was carried out by directly adding activated carbon sorbent into the extract solution, followed by shaking and filtration. Under the optimum conditions, the proposed method was sensitive and showed a good linearity within a range of 2-500 ng/g, with the correlation coefficients (r) varying from 0.9991 to 0.9996. The enrichment factors ranged from 127 to 138. The limit of detections (LODs) were in the range of 0.12-0.68 ng/g, and the relative standard deviations (RSDs) for 50 ng/g of each analytes in tomato samples were in the range of 3.25-6.26 % (n = 5). The proposed method was successfully applied for the extraction and determination of the mentioned analytes residues in tomato and cucumber samples, and satisfactory results were obtained.

Vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet combined with flame atomic absorption spectrometry for the fast determination of cadmium in water samples.

A novel vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet (VSLLME-SFO) was developed for the fast, simple and efficient determination of cadmium (Cd) in water samples followed by flame atomic absorption spectrometry (FAAS). In the VSLLME-SFO process, the addition of surfactant (as an emulsifier), could enhance the mass transfer from the aqueous solution into the extraction solvent. The extraction solvent could be dispersed into the aqueous phase under vigorous shaking with the vortex. In this paper, we investigated the influences of analytical parameters, including pH, extraction solvent type and its volume, surfactant type and its volume, concentration of chelating agent, salt effect and vortex time, on the extraction efficiency of Cd. Under the optimized conditions, the limit of detection was 0.16 µg/L. The analyte enrichment factor was 37.68. The relative standard deviation was 3.2% (10 µg/L, n = 10) and the calibration graph was linear, ranging from 0.5 to 30 µg/L. The proposed method was successfully applied for the analysis of ultra-trace Cd in river water and wastewater samples.

Determination of boron in water samples by dispersive liquid-liquid microextraction based on the solidification of a floating organic drop coupled with a fluorimetric method.

In this work, a new, rapid and reliable method for the determination of boron in water samples by dispersive liquid-liquid microextraction based on the solidification of a floating organic drop (DLLME-SFO) prior to fluorescence spectra analysis was developed. As a result of its complexation with boric acid, the method relies on the enhancement of the fluorescence (λex = 350 nm, λem = 373 nm) of chromotropic acid. The influences of DLLME-SFO parameters, including the extraction solvent type and its volume, pH, the disperser solvent type and its volume, and salt effects were investigated. Under the optimized conditions, the limit of detection was 0.11 ng L(-1), with a preconcentration factor of 86 times. The calibration curve was linear in the range of 0-40 nM. The proposed method has also been successfully applied to analyze real water samples and the relative recoveries of water samples ranged from 86.9 to 93.2%.

Dispersive solid-phase extraction followed by vortex-assisted dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge.

A novel dispersive solid-phase extraction combined with vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high-performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean-up of the extract was conducted by dispersive solid-phase extraction using activated carbon as the sorbent. The vortex-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1-undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2-500 ng/g with correlation coefficients (r) of 0.9993-0.9999. The limits of detection were in the range of 0.08-0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.