Selective dissolution of zinc and lead from duplex ß-phase brasses in low and high conductivity water.

This study provides insights regarding the selective metal leaching of brass in various tap water conditions, which benefits water utilities to predict the potential of metal released from brass water meters. The long-term time-dependent selective metal dissolution of brass with various ß phase fractions have not previously been investigated. In this study, a 201-d immersion experiment was carried out in low and high conductivity tap water (LCTW and HCTW, respectively). Three commercialized brass samples in different ß phase fractions (ß = 51%, ß = 43%, ß = 39%), named brass 51, brass 43, and brass 39, respectively, were used. The results showed that brass 51 had the most negative corrosion potential (-0.17 V) and the lowest polarization resistance (8.5 kΩ) compared to brass 43 and brass 39 (-0.04 V and 10.1-14.7 kΩ, respectively) in LCTW. This trend was verified by the 201-d immersion experiment in which brass 51 exhibited the highest zinc leaching rate (21-30 µg L-1 cm-2 d-1), followed by brass 43 and brass 39 (16-23 µg L-1 cm-2 d-1) in both waters. The leaching amounts of lead and copper were extremely low compared to zinc. In LCTW, the uniform corrosion (UC) mechanism dominated from day 1 to day 120. Afterwards, UC was replaced by the galvanic corrosion (GC) mechanism, with the selective leaching coefficient of Zn over Cu (SZn/Cu) increasing from 10 to 25 to 40-80. In HCTW, however, the SZn/Cu reached 300-1000, and the transition of UC to GC occurred earlier on day 30 due to the rapid formation of the ZnO layer on the brass surface that hindered the ion attack.

Destabilization of polystyrene nanoplastics with different surface charge and particle size by Fe electrocoagulation.

Nanoplastics (NPs) discharged from wastewater could pose a major threat to organisms in aquatic environments. Effective removal of NPs by the current conventional coagulation-sedimentation process is not yet satisfactory. This study aimed to investigate the destabilization mechanism of polystyrene NPs (PS-NPs) with different surface properties and sizes (i.e., 90 nm, 200 nm, and 500 nm) by Fe electrocoagulation (EC). Two types of PS-NPs were prepared by a nanoprecipitation method using sodium dodecyl sulfate and cetrimonium bromide solutions to produce negatively-charged SDS-NPs and positively-charged CTAB-NPs. For both NPs, obvious floc aggregation from 7 µm to 14 µm was observed only at pH 7 with particulate Fe accounted for >90 %. At pH 7, Fe EC removed 85.3 %, 82.8 %, and 74.7 % of the negatively-charged SDS-NPs at small-, mid-, and large-sizes from 90 nm, 200 nm, to 500 nm, respectively. Small-size SDS-NPs(90 nm) were destabilized through physical adsorption on the surface of Fe flocs, while the main removal mechanism of mid- and large-SDS-NPs(200 nm and 500 nm) involved the enmeshment of large Fe flocs. Compared to SDS-NPs(200 nm and 500 nm), Fe EC performed similar destabilization behavior to two CTAB-NPs(200 nm and 500 nm), but it resulted in much lower removal rates of 54.8 % - 77.9 %. The Fe EC also exhibited no removal (<1 %) ability toward the small-size and positively-charged CTAB-NPs(90 nm) due to insufficient formation of effective Fe flocs. Our results provide insight into the destabilization of PS in nano-scale with different sizes and surface properties, which clarifies the behavior of complex NPs in a Fe EC-system.

Transformation of copper oxide nanoparticles as affected by ionic strength and its effects on the toxicity and bioaccumulation of copper in zebrafish embryo.

This study aimed to investigate the transformation of copper oxide nanoparticles (CuO NPs) in aquatic environments under different ionic strength and further examine its effects on copper toxicity and bioaccumulation by monitoring the responses and uptake behaviours of zebrafish embryo. Ionic strength (IS) was simulated according to surface water (1.5 mM), groundwater (15 mM), and wastewater (54 mM), representing low-, mid-, and high-IS water, respectively. At the highest exposure of 10 mg CuO/L, zebrafish larvae mortality was increased from 21.3% to 33.3%, when IS decreased from 54 to 1.5 mM. Low-IS solution also caused the highest numbers of delayed hatching embryo (81.3%) and opaque yolk deformation (36.3%). Copper bioaccumulation markedly increased when larvae were exposed to low-IS water (35%) relative to high-IS water (15%). Exposing to low-IS particularly enhanced copper uptake (~15 ng Cu/g inside embryo), facilitating the copper accumulation in the heart of larvae, whereas aggregated CuO NPs (>500 nm) in mid- and high-IS water were blocked from the embryo and found abundantly in the body axis and tail. Results indicate that CuO NPs in low-IS solutions rapidly form the relatively small CuO NP aggregates with a high copper dissolution, which would pose great concern for aquatic organisms.

Keratin particles generated from rapid hydrolysis of waste feathers with green DES/KOH: Efficient adsorption of fluoroquinolone antibiotic and its reuse.

Fluoroquinolone antibiotics are widely used in human and veterinary medicine. However, untreated fluoroquinolone seriously threatens the ecosystem and human health. In this study, deep eutectic solvents (DESs) were applied for the hydrolysis of waste feathers, and the keratin particles (KPs) in a low-cost teabag were utilized to adsorb fluoroquinolone norfloxacin. Results showed that choline chloride/ethylene glycol DES rapidly hydrolyzed feathers within 10 min, and the undissolved particles effectively adsorbed norfloxacin. Adding KOH markedly shortened the hydrolysis time (6 min) and increased the adsorption ability of KPs. The optimum hydrolysis conditions were DES ratio of 1 g: 4.67 g, KOH of 35.68 g L-1, and temperature of 90 °C. When KPDES+KOH of 2 g L-1, norfloxacin of 25 mg L-1, and pH0 7 were used, 94% of norfloxacin was removed in 60 min. A low-cost teabag effectively separated the KPs from the solution after adsorption and did not decrease the adsorption ability of the KPs. The Langmuir isotherm model well described the adsorption behavior of KPsDES+KOH (qmax = 79.36 mg g-1, R2 = 0.9972). In addition, acetone efficiently regenerated the exhausted KPsDES+KOH. The KPs maintained >80% of its adsorption ability after seven cycles of regeneration.

Characteristics of low and high SUVA precursors: Relationships among molecular weight, fluorescence, and chemical composition with DBP formation.

Disinfection by-products (DBPs) formed upon water treatment is an emerging issue worldwide. While monitoring of DBP precursors can easily be achieved for high specific UV absorbance (SUVA) organic (>6 L/mg·m), low and extremely low SUVA precursors (<2 L/mg·m) are difficult to monitor or even to predict their DBP formation behaviour. This study investigated the relationships among NOM characteristics, such as molecular weight (MW), fluorescence, and chemical composition, with DBP formation resulting from the chlorination of relatively high and low SUVA precursors. High SUVA precursors were formed by C-rich substances (82-85% of total mass) corresponding with high C/N and C/O (>100 and >5, respectively). Such precursors exhibited the fluorescence of long-wavelength humic-like signal and occurred at a high MW range (>30 kDa). By contrast, low SUVA precursors were either N-rich and/or O-rich substances, associated with much lower carbon content (40-70%). Low SUVA, N-rich precursors particularly also occurred at a high MW region (>100 kDa) and produced a strong protein-like fluorescence signal. When SUVA values of O-rich precursors were extremely low (<1 L/mg·m) they were accompanyied by short-wavelength humic-like fluorescence. During DBP tests, high SUVA produced only high yields of carbonaceous DBPs (e.g trichloromethane, haloacetic acids, haloketones), whereas low SUVA N-rich precursors yielded high levels of both C and NDBPs (e.g. haloacetonenitrile, chloropicrin). By contrast, extremely low SUVA precursors produced significantly low levels of both C and NDBPs (total < 30 µg/mgC). Furthermore, 19 of 20 regression models of DBP formation using log-transformed MW gave R2 = 0.50-0.97. The strong regressions and correlations of NOM characteristics with DBPs in this study provide a better understanding of the influence of precursors characteristics on DBP monitoring, especially for low SUVA NOM.

Fluorescent and molecular weight dependence of THM and HAA formation from intracellular algogenic organic matter (IOM).

This study (i) examined the formation of two major carbonaceous disinfection by-products (C-DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), during the chlorination of intracellular algogenic organic matter (IOM) extracted from two commonly blooming algae M. aeruginosa (MA) and Chlorella sp. (CH), and (ii) investigated the roles and relationships of fluorescent and molecular weight (MW) properties on/with IOM-derived THMs and HAAs. The extracted IOM samples were separated into different MW fractions by centrifugal devices with membrane support with MW cut-offs of 100, 30, 10, 3, and 1 kDa. We observed an overall reduction of C-DBPs with a decrease of IOM-MW from >100 kDa to <1 kDa. Of six fractionated IOM, a large fraction (>100 kDa) contributed the largest amount to the MW distribution of IOM, accounting for 33 and 42% of the total dissolved organic carbon (DOC) of MA and CH, respectively. It also had the highest-yielding potential to produce significant levels of THMs and HAAs, and total C-DBPs over other small MW fractions. Although small MW fractions (>10 kDa) contributed around 50% of the total DOC, they made an insignificant contribution (>20%) to the THMs, HAAs, and overall C-DBPs. Furthermore, the decrease of IOM MW caused a shift from the domination of HAA formation to THM formation, especially when MW was <10 kDa. By canonical correspondent analysis, the relationship of IOM-derived THMs and HAAs with IOM properties was examined. In particular, large fractions of IOM, exhibiting aromatic protein- (AP) and soluble microbial product- (SMP) like fluorescence, are favorable for the formation of HAAs, whereas small MW fractions of IOM with HA- and FA-like fluorescence preferentially tends to form THMs. Our findings evidently show the strong dependence of IOM-derived THMs and HAAs on the fluorescent and MW properties. Therefore, the characterization of MW and fluorescent properties can provide the advantages in the control of algae-derived DBPs upon the chlorination of eutrophic water.

Probing algogenic organic matter (AOM) by size-exclusion chromatography to predict AOM-derived disinfection by-product formation.

High-performance size exclusion chromatography (HPSEC) coupled with peak-fitting technique was used to probe molecular weight (MW) properties of algogenic organic matter (AOM). The qualitative and quantitative MW information derived was used to predict AOM-derived disinfection by-product (DBP) formation. We resolved overlapping HPSEC chromatograms of all AOM samples into six major peaks with R2 > 0.996. This study gave significant insight into the HPSEC profiles of AOM, in which resolved peaks A and B (biopolymers) and peak C (humic substances) showed a strong correlation with the formation of carbonaceous-DBPs (C-DBPs). This likely resulted from the abundance of aromatic structures and conjugated CC double bonds in their chemical nature. Our results also indicated the importance of algal cells, including intra-cellular and cell-bound organic matter, over extra-cellular organic matter as precursors to C-DBP formation. The application of the information extracted from HPSEC profiles associated with the fluorescent components of AOM showed great improvements in the predictability of THMs, HAAs, and C-DBPs with R2 > 0.7 and p < 0.05. The outcome of this study will significantly benefit effective control of AOM-derived DBP formation by the chlorination of eutrophic waters.

Effects of C/N ratio on nitrate removal and floc morphology of autohydrogenotrophic bacteria in a nitrate-containing wastewater treatment process.

The effects of C/N ratio of a nitrate-containing wastewater on nitrate removal performed by autohydrogenotrophic bacteria as well as on the morphological parameters of floc such as floc morphology, floc number distribution, mean particle size (MPS), aspect ratio and transparency were examined in this study. The results showed that the nitrate reduction rate increased with increasing C/N ratio from 0.5 to 10 and that the nitrogen removal of up to 95% was found at the C/N ratios of higher than 5 (between 0.5-10). Besides, high C/N ratio values reflected a corresponding high nitrite accumulation after 12-hr operation, and a fast decreasing rate of nitrite in the rest of operational time. The final pH values increased with the C/N ratio increasing from 0.5 to 2.5, but decreased with the C/N ratio increasing from 2.5 to 10. There were no significant changes in floc morphology with the MPSs ranging from 35 to 40µm. Small and medium-sized flocs were dominant in the sludge suspension, and the number of flocs increased with the increasing C/N ratios. Furthermore, the highest apparent frequency of 10% was observed at aspect ratios of 0.5 and 0.6, while the transparency of flocs changed from 0.1 to 0.7.

Uptake of BDE-209 on zebrafish embryos as affected by SiO2 nanoparticles.

It was hypothesized that interactions between emerging contaminants such as decabromodiphenyl ether (BDE-209) and nanoparticles (NPs) such as nano-SiO2 (nSiO2), can affect contaminant transport in the aquatic environment and its ecotoxicity. This study assessed the influence of nSiO2 on the uptake of BDE-209 by zebrafish embryo. The distribution of BDE-209 and nSiO2 on the external chorion and the internal embryo mass (i.e., dechorionated embryo) was measured. For single exposure of nSiO2 to zebrafish embryo, separately, results showed that nSiO2 accumulation on the chorion surface was higher than that in the dechorionated embryo. The nSiO2 accumulation on the chorion surface was 129-200 mg-nSiO2/g-chorion at 48 h post fertilization, hpf, of exposure time, whereas the equilibrium adsorption of nSiO2 on the dechorionated embryo was ca. 0.42-0.54 mg-nSiO2/g-embryo at 6 hpf. Results showed that the formation of nSiO2-BDE-209 associates promoted both extracellular and intracellular uptake of BDE-209 by zebrafish embryo, thereby increasing the bioconcentration of BDE-209 on the chorion surface and in embryo. The results also revealed that the accumulation of BDE-209 on the chorion was remarkably greater than that on the dechorionated embryo at 48 hpf. The uptake of BDE-209 was 17.2 ±â€¯0.45 mg/g-chorion (or 86 ng-BDE-209/chorionated embryo) and 0.37 ±â€¯0.01 mg/g-embryo (or 18.6 ng-BDE-209/dechorionated embryo), respectively, when co-exposure of zebrafish embryos to BDE-209 and nSiO2. Results from the SEM and EDS analysis revealed that nSiO2 already passed through the chorion and adhered to the embryo surface/mass.

Teratogenic responses of zebrafish embryos to decabromodiphenyl ether (BDE-209) in the presence of nano-SiO2 particles.

This study investigated the influence of nano-SiO2 particles (nSiO2) on the teratogenic responses of zebrafish embryos to decabromodiphenyl ether (BDE-209). Zebrafish embryos were exposed to BDE-209 in the absence and presence of nSiO2 for 96 h post fertilization (hpf). Results showed that formation of nSiO2-BDE-209 associates promoted both extracellular and intracellular uptake of BDE-209 by zebrafish embryos, thereby increasing the bioconcentration of BDE-209 on the chorion surface and the embryos. Results also showed embryos delay hatching temporarily when co-exposure to BDE-209 and nSiO2 at 60 hpf. Furthermore, there was heartbeat decline (28.3 beats/10s) and increase in irregular heartbeat (45.8%) in zebrafish larvae at 96 hpf, compared to the sole exposure to BDE-209 (32.7 beats/10s and 0%). Malformation in terms of spinal curvature (SC), pericardial edema (PE) and yolk sac edema (YSE) were observed on zebrafish larvae at 33.9, 23.4, and 18%, respectively. Overall, abnormal development of zebrafish was apparent when co-exposure to BDE-209 and nSiO2. All relevant evidence considered, nSiO2 could facilitate the transport of BDE-209 towards zebrafish embryos and negatively impact the development of zebrafish.

Treatment and toxicity evaluation of methylene blue using electrochemical oxidation, fly ash adsorption and combined electrochemical oxidation-fly ash adsorption.

Treatment of a basic dye, methylene blue, by electrochemical oxidation, fly ash adsorption, and combined electrochemical oxidation-fly ash adsorption was compared. Methylene blue at 100 mgL(-1) was used in this study. The toxicity was also monitored by the Vibrio fischeri light inhibition test. When electrochemical oxidation was used, 99% color and 84% COD were removed from the methylene blue solution in 20 min at a current density of 428 Am(-2), NaCl of 1000 mgL(-1), and pH(0) of 7. However, the decolorized solution showed high toxicity (100% light inhibition). For fly ash adsorption, a high dose of fly ash (>20,000 mgL(-1)) was needed to remove methylene blue, and the Freundlich isotherm described the adsorption behavior well. In the combined electrochemical oxidation-fly ash adsorption treatment, the addition of 4000 mgL(-1) fly ash effectively reduced intermediate toxicity and decreased the COD of the electrochemical oxidation-treated methylene blue solution. The results indicated that the combined process effectively removed color, COD, and intermediate toxicity of the methylene blue solution.

Degradation of azo and anthraquinone dyes by a low-cost Fe 0/air process.

Degradation of two different kinds of dyes, anthraquinone Reactive Blue 4 (RB4) and azo Reactive Black 5 (RB5), by low-cost zero valent iron (Fe(0)) in a N(2) bubbling system (Fe(0)/N(2) process) and air bubbling system (Fe(0)/air process) was investigated. The operating parameters, including initial solution pH, dye concentration and Fe(0) dose, were also evaluated. The Fe(0)/air process shows a higher decolorization rate compared to the Fe(0)/N(2) process. Both RB4 and RB5 solutions at 100 mg L(-1) were rapidly decolorized by Fe(0)/air process within 9 and 3 min, respectively, at initial solution pH 3, Fe dose of 50 g L(-1) and air flow rate of 5 L min(-1). The optimal initial solution pH was 3. The Fe(0)/N(2) process removed only <17% of COD. However, significant COD removals were achieved for RB 4 (87%) and RB5 (43%) by the Fe(0)/air process after 9 min of treatment. Spectra analysis results indicated that the Fe(0)/N(2) process destroyed only the anthraquinone group (A(594)) for the RB4 solution and decreased the azo (A(596)) and naphthalene group (A(310)) for the RB5 solution. However, the Fe(0)/air process rapidly removed A(594), A(370), A(296) (anthraquinone group) and A(256) (aromatic and dichlorotriazine group) for RB4, and A(597) and A(310) (naphthalene group) for RB5. The results indicated that the low-cost Fe(0)/air process is a potential technique for rapid degradation of RB4 and RB5 solutions.