Search

A new electrode was constructed via the anodic electropolymerization of poly-(L-serine) (PLS) on an rGO-Nafion-modified glassy carbon electrode (GCE) for the detection of the emerging organic contaminant naproxen (NPX). The morphology, crystal phase, and surface elements of the electrode were investigated with SEM, TEM, XRD, Raman, ATR-FTIR, zeta potential, C-H-O, and XPS analyses. Results of the surface analysis showed a porous structure resembling graphene sheets inside the Nafion/GCE architecture. Various electrochemical parameters, including scan rate, pH, and NPX concentration, were studied to evaluate the performance of the electrode. The synergistic effect of PLS and rGO-Nafion greatly facilitated the catalytic oxidation of NPX on PLS/rGO-Nafion/GCE. Electrochemical NPX oxidation was a one-electron transfer and adsorption limited process. The optimal working potential was 0.92 V vs. Ag/AgCl. The oxidation current of NPX increased with the increase in the concentration of analyte and scan rate but decreased with pH. The modified electrode exhibited excellent linearity with respect to NPX concentration in the range of 4.3 to 87 μM and limit of detection of 0.23 μM (S/N = 3). The PLS/rGO-Nafion/GCE is a fast, sensitive, reliable, and economical electrode for the detection of NPX in water.

Tap water contains some heavy metals and bio-organic substances with variety of concentration and these cannot be treated using regular physicochemical processes. So the present study, aims at evaluating the effectiveness of the sterilization using electrocatalytic technique with Escherichia coli (E. coli) as the observed index. The operational parameters such as anode material, voltage, inflow method, and electrode number are studied to understand the variation of pH, conductivity, E. coli, and residual chlorine of tap water. The outcome reveals that the maximum sterilization efficiency of E. coli is obtained using the titanium dioxide electrode, followed by ruthenium dioxide and graphite. A disinfection efficiency of 98% can be easily achieved. Also, the appropriate increase in the operating voltage can increase the sterilization efficiency and decrease the treatment time. The sterilization efficiency of the E. coli can reach 100% under the continuous inflow of tap water and the voltage of 60 V for 1 min, which meets the conventional standard of drinking water (6 CFU/100ml). The estimated operating cost of treatment of 1 ton of tap water is NTD 1.7.

Nanocomposite materials can enhance the capabilities of water treatment processes such as photocatalysis. In this work, novel light-driven nanocatalysts were synthesized by using nickel ferrite (NiFe2O4) to nanoenable graphene oxide (GO) substrates. GO is an emerging 2D nanomaterial with high conductivity and adsorption properties. Moreover, the electric properties of GO improve photocatalytic performance by promoting charge carrier separation. Results of the characterization of the nickel ferrite nanoenabled graphene oxide (NiFe2O4@GO) nanocomposites demonstrate that homogeneous and stable photocatalysts were produced. The as-synthesized nanocatalysts enabled complete decolorization of the colored water matrix in short irradiation times of 150 min using minimal catalyst loading at 0.5 g L−1. The selective hook and destroy mechanism reduced the competitive effect of co-existing ions in solution. Furthermore, the use of specific scavengers helped to elucidate the degradation mechanisms of organic dye methylene blue by NiFe2O4@GO nanocomposites.

Harbor sediments normally accumulate the pollutants from municipal and industrial activities in the estuarine zone. This work aimed to characterize the fractionation change of heavy metals in harbor sediments before and after chemical washing. Since the annual dredging around the Kaohsiung Harbor has increased over time, the influence of ex-situ acid washing on sediment quality needs to be evaluated. Experimental parameters of acid washing included the solid loading (4–20%) and types (HCl, HNO3, and citric acid) and concentrations (0.01–1 M) of acids. The fractionation of Cu, Zn, Ni, Cd, Cr, and Pb in the sediments at three estuaries, the Chienchen River, Canon River (Dock No.5), and Yanshui River, before and after washing processes were determined through sequential extraction. The washing efficiencies of HCl, HNO3, and citric acid were similar, being 80.1–83.7%, 27.6–30.9%, 20.7–23.9%, and 97.2–98.8% for Zn, Ni, Cr, and Cd, respectively. After 15 min of washing, HCl was found as a suitable washing agent, and particularly, more effective for Cu (65.3%) and Pb (79.4%) than other acids. The extraction process suggested that the acid washing of carbonate, the Fe-Mn oxide composite, and organic phases were highly correlated to their quantities in the sediments. However, the removal efficiency was inversely related to the metals in the residual phase. Knowing the mobility and bioavailability of heavy metals based on fractionation of metals benefits the assessment of the potential risk of dredged harbor sediment after the washing procedure. This study provided evidence that acid washing, as a remediation method, could be versatile in removing heavy metals from mobile phases without causing mineralogical changes to the contaminated sediments of the harbor area.

To evaluate the toxicity of sediments collected from the mouths of four rivers and entrances of Kaohsiung Harbor, Taiwan, a combination of in vitro cytotoxicity assays (Clone 9 cells) and chemical analysis that quantified 16 polycyclic aromatic hydrocarbons (PAHs), 10 phthalate esters (PAEs), and 2 alkylphenols (APs) was employed. Results showed that the total concentrations of PAHs, PAEs, and APs ranged between 77.9 and 24,363 ng/g dw, between 268 and 118,010 ng/g dw, and between 32.6 and 84,438 ng/g dw in sediments, respectively. The highest concentrations of PAHs, PAEs, and APs were found in the mouths of the Salt River (SR), Love River (LR), and Jen-Gen River (JR), respectively. Mean reference sediment quotient (m-RSQ) values were calculated using the chemical concentrations measured in the sediment of entrance I (EI) as the benchmark, and the order was SR > LR > JR > CR (Canon River mouth) > EII (entrance II) > EI. Results of the cytotoxicity assay showed that the 50% inhibitory concentration (IC50) of Clone 9 cells was in the order of LR < SR < JR < CR < EII < EI. Results on DNA content, apoptotic and autophagy protein biomarkers, and acridine orange staining indicated that the cause of death of Clone 9 cells after treatment with sediment extracts of the LR site was mainly through apoptosis. There was a significant correlation between m-RSQ values and IC50 of Clone 9 cells. The correlation analysis between cytotoxicity and chemical analytical data indicated that certain unknown chemicals may exist in LR sediment. Overall, this study demonstrated that the combination of chemical and biological analyses can provide a more comprehensive and realistic assessment of sediment toxicity to aquatic organisms compared to traditional chemistry-based-only analytical approaches.

Bi2WO6 (BW) and SnO2/Bi2WO6 composites (SnBWs) were synthesized by a single-step solvothermal process. Four SnO2/BW molar ratios, 0.1, 0.25, 0.5 and 1 were used to generate 0.1SnBW, 0.25SnBW, 0.5SnBW and 1SnBW. The surface characteristics of BW, SnO2 and SnBWs were elucidated by X-ray diffractometry (XRD), transmission electron microscopy, specific surface area analysis, UV–vis spectrophotometry, photoluminescence spectrophotometry and X-ray photoelectron spectroscopy. C.I. Reactive Red 2 (RR2) was used as a target pollutant to compare the photocatalytic activities of the prepared SnBWs. The effects of RR2 concentration and photocatalyst dosage on RR2 photodegradation were elucidated. The XRD results revealed that all of the peaks of SnBWs in XRD patterns could be assigned to SnO2 or BW, and no other peak was found, indicating that SnO2 and BW were successfully composited. The band gaps of SnO2, BW, 0.1SnBW, 0.25SnBW, 0.5SnBW and 1SnBW were estimated to be 3.75, 2.85, 2.95, 2.94, 2.93 and 2.97 eV, which correspond to RR2 photodegradation rates under simulated solar light irradiation of 0.0025, 0.0255, 0.0333, 0.0279, 0.0408 and 0.0174 min−1. 0.5SnBW had the highest photocatalytic activity in RR2 photodegradation. The RR2 photodegradation rate increased as the 0.5SnBW dose increased, but decreased as the RR2 concentration increased. The results of adding scavengers suggested that the photogenerated holes were the main oxidative species in RR2 photodegradation in the 0.5SnBW system. The findings of this study suggest that the effective suppression of the recombination of electron–hole pairs in 0.5SnBW may improve the photocatalytic activity of 0.5SnBW over those of pure BW and SnO2.

A sensitive voltammetric sensor has been developed for hazardous methyl parathion detection (MP) using graphene oxide@Ce-doped TiO2 nanoparticle (GO@Ce-doped TiO2 NP) electrocatalyst. The GO@Ce-doped TiO2 NPs were prepared through the sol-gel method and characterized by various physicochemical and electrochemical techniques. The GO@Ce-doped TiO2 NP–modified glassy carbon electrode (GCE) addresses excellent electrocatalytic activity towards MP detection for environmental safety and protection. The developed strategy of GO@Ce-doped TiO2 NPs at GCE surfaces for MP detection achieved excellent sensitivity (2.359 μA μM−1 cm−2) and a low detection limit (LOD) 0.0016 μM with a wide linear range (0.002 to 48.327 μM). Moreover, the fabricated sensor shows high selectivity and long-term stability towards MP detection; this significant electrode further paves the way for real-time monitoring of environmental quantitative samples with satisfying recoveries.

Environmental impact of pesticides is one of the great concerns being addressed by water-food nexus research. Imidacloprid is one of the most used insecticides as an alternative for carcinogenic organochloride insecticides. Even though Imidacloprid has lower toxicity for mammals, its fate and incomplete degradation by conventional wastewater treatment technologies are worrisome when considering continuous environmental exposure. Application of fluidized-bed Fenton process is proposed as an alternative treatment to mitigate the impact of imidacloprid in water. The consequence of different experimental parameter variations such as Fe2+ catalyst concentration, H2O2 concentration and propylene glycol (a common excipient in commercial pesticides) was evaluated. Experimental results under optimized conditions demonstrate almost complete removal of imidacloprid and abatement of chemical oxygen demand and total organic carbon. The intermediates of oxidized imidacloprid yield during fluidized-bed Fenton treatment were identified using GC–MS and a reaction sequence for imidacloprid degradation was proposed. Keywords: Fluidized-bed Fenton, Wastewater treatment technologies, Contaminants of emerging concern, Advanced oxidation processes, Pesticides

The objectives of this study were to (1) conduct laboratory bench and column experiments to determine the oxidation kinetics and optimal operational parameters for trichloroethene (TCE)-contaminated groundwater remediation using potassium permanganate (KMnO4) as oxidant and (2) to conduct a pilot-scale study to assess the efficiency of TCE remediation by KMnO4 oxidation. The controlling factors in laboratory studies included soil oxidant demand (SOD), molar ratios of KMnO4 to TCE, KMnO4 decay rate, and molar ratios of Na2HPO4 to KMnO4 for manganese dioxide (MnO2) production control. Results show that a significant amount of KMnO4 was depleted when it was added in a soil/water system due to the existence of natural soil organic matters. The presence of natural organic material in soils can exert a significant oxidant demand thereby reducing the amount of KMnO4 available for the destruction of TCE as well as the overall oxidation rate of TCE. Supplement of higher concentrations of KMnO4 is required in the soil systems with high SOD values. Higher KMnO4 application resulted in more significant H+ and subsequent pH drop. The addition of Na2HPO4 could minimize the amount of produced MnO2 particles and prevent the clogging of soil pores, and TCE oxidation efficiency would not be affected by Na2HPO4. To obtain a complete TCE removal, the amount of KMnO4 used to oxidize TCE needs to be higher than the theoretical molar ratio of KMnO4 to TCE based on the stoichiometry equation. Relatively lower oxidation rates are obtained with lower initial TCE concentrations. The half-life of TCE decreased with increased KMnO4 concentrations. Results from the pilot-scale study indicate that a significant KMnO4 decay occurs after the injection due to the reaction of KMnO4 with soil organic matters, and thus, the amount of KMnO4, which could be transported from the injection point to the downgradient area, would be low. The effective influence zone of the KMnO4 oxidation was limited to the KMnO4 injection area (within a 3-m radius zone). Migration of KMnO4 to farther downgradient area was limited due to the reaction of KMnO4 to natural organic matters. To retain a higher TCE removal efficiency, continuous supplement of high concentrations of KMnO4 is required. The findings would be useful in designing an in situ field-scale ISCO system for TCE-contaminated groundwater remediation using KMnO4 as the oxidant.

Three transects were established along the southwestern coast of Taiwan; transects from north to south were respectively extended from the Kaohsiung Harbor, Kaoping River estuary, and Fangshan River estuary. Six metals including Pb, Cd, Cr, Cu, Zn, and Ni were analyzed in the zooplankton and seawater samples. A total of 24 groups of zooplankton were identified. Calanoid was the frequently collected group and accounted for greater than 40% of the relative abundance of zooplankton. Results showed that metal concentrations in seawater close to coast were higher than those in the outside of transect. The mean of metal concentrations in zooplankton followed the hierarchy: Zn > Cu > Pb > Ni > Cr > Cd. On the whole, metal concentrations in zooplankton from sampling sites in the coastal region were observed to be higher than those in the offshore region. The bioconcentration factor of zooplankton ranged within 103-105 for all studied metals and indicated that zooplankton in the seawater of southwestern Taiwan can accumulate metal even at background concentrations of metals. The value of diversity indices exhibited an increase in the distance to the coast, whereas the abundance showed no significant correlation with that. Consequently, the lowest mean abundance of zooplankton and the highest average metal bioaccumulation were found in transect outside Kaohsiung Harbor, representing that Kaohsiung Harbor has the contamination of anthropogenic metals that results in the impact on zooplankton.

The study developed a new and cost-effective method for the remediation of marine sediments contaminated with polycyclic aromatic hydrocarbons (PAHs). Iron oxide (Fe3O4) nanoparticles were synthesized as the active component, supported on carbon black (CB), to form a composite catalyst (Fe3O4–CB) by using a wet chemical method. The oxidation of 16 PAH contaminants present in marine sediments significantly activated sodium persulfate (Na2S2O8) to form sulfate free radicals (SO4 −·); this was investigated in a slurry system. In addition, in vitro cytotoxic activity and oxidative stress studies were performed. The synthesized composite catalysts (Fe3O4–CB) were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, a superconducting quantum interference device magnetometry, and environmental scanning electron microscopy. The efficiency of PAH removal was 39–63% for unactivated persulfate (PS) from an initial dose of 1.7 × 10−7–1.7 × 10−2 M. The removal of PAHs was evaluated using Fe3O4/PS, CB/PS, and Fe3O4/PS and found to be 75, 64, and 86%, respectively, at a temperature of 303 K, PS concentration of 1.7 × 10−5 M, and pH of 6.0. An MTT assay was used to assess the cytotoxicity of the composite catalyst at five concentrations (25, 50, 100, 200, and 400 μg/mL) on human hepatoma carcinoma (HepG2) cells for 24 h. This revealed a dose-dependent decrease in cell viability. A dichlorofluorescein diacetate assay was performed to evaluate the generation of reactive oxygen species, which principally originated from the ferrous ions of the composite catalyst.

The extraction efficiency of heavy metals from soils using three forms of gamma poly-glutamic acid (γ-PGA) as the washing agents was investigated. Controlling factors including agent concentrations, extraction time, pH, and liquid to soil ratio were evaluated to determine the optimum operational conditions. The distribution of heavy metal species in soils before and after extraction processes was analyzed. Up to 46 and 74% of heavy metal removal efficiencies were achieved with one round and a sequential extraction process using H-bonding form of γ-PGA (200 mM) with washing time of 40 min, liquid to solid ratio of 10 to 1, and pH of 6. Major heavy metal removal mechanisms were (1) γ-PGA-promoted dissolution and (2) complexation of heavy metal with free carboxyl groups in γ-PGA, which resulted in heavy metal desorption from soils. Metal species on soils were redistributed after washing, and soils were remediated without destruction of soil structures and productivity.

A two-stage system for octachlorinated dibenzo-p-dioxin (OCDD)-contaminated soil remediation was developed. Soil washing using emulsified oil (EO) was applied in the first stage for OCDD extraction followed by the second stage of bioremediation using P. mendocina NSYSU for remaining OCDD biodegradation. The major tasks included (1) determination of optimal soil washing conditions for OCDD extraction by EO, (2) evaluation of feasibility of OCDD biodegradation by P. mendocina NSYSU under aerobic cometabolic conditions using EO as the primary substrate, and (3) assessment of the effectiveness of OCDD removal using the two-stage system. During the soil washing stage, EO with two different oil-to-water ratios (1:50 and 1:200) and pore volumes were tested with initial soil OCDD concentration of 21,000 µg/kg. Results indicate that EO could effectively improve the solubility and desorption of OCDD in soils. Up to 74% of OCDD removal could be obtained after washing with 60 PVs of EO and dilution factor of 50. After the soil washing process, enriched P. mendocina NSYSU solution was added into the reactor to enhance the aerobic biodegradation of remaining OCDD in soils. P. mendocina NSYSU could use adsorbed EO globules as substrates and caused significant OCDD degradation via the aerobic cometabolic mechanism. Approximately 82% of the remaining OCDD could be removed after 50 days of operation, and P. mendocina NSYSU played important roles in OCDD biodegradation. Up to 87% of OCDD was removed through the EO washing and biodegradation process. The two-stage system is a potential technology to remediate dioxin-contaminated soils.

The appearance of assimilable organic carbon (AOC), microbial regrowth, disinfection by-products (DBPs), and pipe corrosion in drinking water distribution systems are among those major safe drinking water issues in many countries. The water distribution system of Cheng-Ching Lake Water Treatment Plant (CCLWTP) was selected in this study to evaluate the: (1) fate and transport of AOC, DBPs [e.g., trihalomethanes (THMs), haloacetic acids (HAAs)], and other organic carbon indicators in the selected distribution system, (2) correlations between AOC (or DBPs) and major water quality parameters [e.g. dissolved oxygen (DO), free residual chlorine, and bacteria, and (3) causes and significance of corrosion problems of the water pipes in this system. In this study, seasonal water samples were collected from 13 representative locations in the distribution system for analyses of AOC, DBPs, and other water quality indicators. Results indicate that residual free chlorine concentrations in the distribution system met the drinking water standards (0.2 to 1 mg l(-1)) established by Taiwan Environmental Protection Administration (TEPA). Results show that AOC measurements correlated positively with total organic carbon (TOC) and UV-254 (an organic indicator) values in this system. Moreover, AOC concentrations at some locations were higher than the 50 microg acetate-C l(-1) standard established by Taiwan Water Company. This indicates that the microbial regrowth might be a potential water quality problem in this system. Higher DO measurements (>5.7 mg l(-1)) might cause the aerobic biodegradation of THMs and HAAs in the system, and thus, low THMs (