Construction of surface-rich MoS2 nanoflowers decorated on 2D layered MXene nanohybrid heterostructure for highly efficient and rapid degradation of oxytetracycline.

In this study, we successfully developed a hybrid architecture referred to as MoS2@MX, involving the integration of MoS2 layered onto MXene using a straightforward co-precipitation method. This innovative hybrid photocatalyst exhibited remarkable efficiency in removing oxytetracycline (OTC) molecules from aqueous solutions under visible-light irradiation. During the photocatalytic process, both MoS2 and MX played distinct yet complementary roles. MoS2 facilitated efficient electron transfer, while MX contributed to the generation of radicals. This unique collaboration resulted in a noteworthy 99 % oxidation efficiency for OTC degradation within a brief 60 min of visible light exposure in an aqueous environment. The radicals 1O2 and •OH were identified as the principal drivers behind OTC degradation, underscoring the vital role of the hybrid material. Mechanistically, the degradation of OTC involved several key steps, including C-H bond cleavage, de-carboxylation, C-N bond oxidation, and de-chlorination. Importantly, the MoS2@MX hybrid composite demonstrated remarkable stability, maintaining a noteworthy photocatalytic efficiency of 89 % for targeted OTC removal after undergoing five consecutive cycles. In conclusion, this study emphasizes the potential of the MoS2@MX hybrid material as an effective agent for degrading organic OTC compounds within aquatic environments. The hybrid's multifaceted roles and exceptional performance suggest promising applications in sustainable water treatment.

Tuning of interfacial HGO@CLS nanohybrid S-scheme heterojunction with improved carrier separation and photocatalytic activity towards RhB degradation.

Herein, we premeditated and invented the innovative hybrid photocatalyst 2D/2D CuLa2S4 on holey graphene oxide (HGO) (HGO@CLS) via the hydrothermal method. Electrochemical techniques demonstrate the action of HGO in the HGO@CLS photocatalyst as an effective medium for electron transfer. Combining bimetallic sulfides on porous HGO synergistically provides a higher negative conduction band edge (-0.141 V), greater photo response (10.8 mA/cm2), smaller charge transfer resistance (Rct = 1.79Ω), and lower photoluminescence (PL) spectral intensity. According to our research, the catalytic recitals are sped up when HGO is assimilated into CLS photocatalyst hetero-junction. Additionally, it lowers the reassimilation rate due to the combined mesh nanostructures and functionality of CLS and HGO. UV-Vis DRS, Mott-Schottky, PL, and Electrochemical impedance spectra (EIS) results manifested that the CuLa2S4/HGO makes the spatial separation competent and transference of charge carriers due to the photon irradiation and exhibits superior photocatalytic ability. Electron spin resonance (ESR) analysis confirmed that •OH and h+ were the predominant radical species responsible for Rhodamine B(RhB) degradation. Moreover, conceivable degradation ways of RhB were deduced according to the identified intermediates which are responsible for the degradation of recalcitrant products. To check the stability of the photocatalyst, revival tests were also carried out. Similarly, the oxidative byproducts created in the deprivation courses were looked at, and a thorough explanation for the mechanism of degradation was given.

A smart home dental care system: integration of deep learning, image sensors, and mobile controller.

In this study, a home dental care system consisting of an oral image acquisition device and deep learning models for maxillary and mandibular teeth images is proposed. The presented method not only classifies tooth diseases, but also determines whether a professional dental treatment (NPDT) is required. Additionally, a specially designed oral image acquisition device was developed to perform image acquisition of maxillary and mandibular teeth. Two evaluation metrics, namely, tooth disease and NPDT classifications, were examined using 610 compounded and 5251 tooth images annotated by an experienced dentist with a Doctor of Dental Surgery and another dentist with a Doctor of Dental Medicine. In the tooth disease and NPDT classifications, the proposed system showed accuracies greater than 96% and 89%, respectively. Based on these results, we believe that the proposed system will allow users to effectively manage their dental health by detecting tooth diseases by providing information on the need for dental treatment. Supplementary Information: The online version contains supplementary material available at 10.1007/s12652-021-03366-8.

Enhanced Adsorption of Tetracycline by Thermal Modification of Coconut Shell-Based Activated Carbon.

Tetracycline (TC) is one of the most frequently detected antibiotics in various water matrices, posing adverse effects on aquatic ecosystems. In this study, coconut shell-based powdered activated carbon (PAC) was thermally modified under various temperatures to enhance TC adsorption. The PAC subjected to 800 °C (PAC800) showed the best TC adsorption. PAC and PAC800 were characterized using N2 adsorption/desorption isotherm, X-ray photoelectron spectroscopy, Raman spectroscopy, XRD, Boehm titration, and zeta potential analyses. Increases in the specific surface area, C/O ratio, C=O, surface charge, basic groups, and the number of stacked graphene layers along with a decrease in structural defects were observed for PAC800 compared to PAC. The TC adsorption was significantly improved for PAC800 compared to that of PAC, which is attributable to the enhanced electrostatic attraction and π-π EDA interactions induced by the changes in the properties. The Freundlich isotherm was the best fit indicating the heterogeneous nature, and the Freundlich constant of PAC and PAC800 increased from 85.8 to 119.5 and 132.1 to 178.6 (mg/g)‧(L/mg)1/n, respectively, when the temperature was increased from 296.15 to 318.15 K. The kinetics were well described by the pseudo-second-order adsorption model and the rate constant of PAC and PAC800 increased from 0.80 to 1.59 and from 0.72 to 1.29 × 10-3 g/mg‧min, respectively, as the temperature was increased. The activation energy of PAC and PAC800 was 23.7 and 19.6 J/mol, respectively, while the adsorption enthalpy was 196.7 and 98.5 kJ/mol, respectively, indicating endothermic nature. However, it was suggested that TC adsorption onto PAC800 was more favorable and was more contributed to by physisorption than that onto PAC. These results strongly suggest that the properties, adsorption capacity, and adsorption mechanisms of carbonaceous adsorbents can be significantly changed by simple thermal treatment. More, the results provide valuable information about the design of carbonaceous adsorbents with better performance where the structures and functional groups, which positively affect the adsorption, must be improved.

Urchin-like structured magnetic hydroxyapatite for the selective separation of cerium ions from aqueous solutions.

In this study, bio-inspired urchin-like structured hydroxyapatite (UHdA) and its magnetic composite (UHdA@Fe3O4) were developed for efficient and easy separation of cerium ions (Ce3+) from aquatic waste streams. UHdA and UHdA@Fe3O4 exhibited superior Ce3+ adsorption capacities of 248.39 and 230.01 mg/g-UHdA respectively, compared to a commercial HdA (141.71 mg/g-HdA) due to their hierarchical mesoporous structure and large specific surface area. The adsorption of Ce3+ to UHdA and UHdA@Fe3O4 were heterogeneous, pseudo-second-order-kinetic, and the rate-limiting step was external mass transfer and intra-particle diffusion. Moreover, thermodynamic studies revealed that the adsorption process was spontaneous and endothermic nature. The high selectivity towards Ce3+ in multi-ionic systems is attributed to the strong affinity between strong Lewis acid (Ce3+) and base (PO43- and OH-) interactions. XRD, FTIR, and XPS analysis demonstrated that the adsorption was mainly attributable to the ion exchange of Ce3+ with Ca2+ and to surface complexation. The desorption of Ce3+ was efficiently accomplished using 0.1 M HNO3. The results suggest that UHdA and UHdA@Fe3O4 could be promising choices for the adsorption and recovery of rare earth elements.

Computational analysis of a collaboration network on human-computer interaction in Korea.

Since information and communication technology (ICT) has become one of the leading and essential fields for allowing developing countries to have the major growth engines, the majority of the countries have promoted collaboration in every ICT-related topics. In this study, we performed the trend and collaboration network analysis (CNA) in Korea for 2010-2019 among researchers who are related to human-computer interaction, one of the hottest research areas in ICT. Publication data were collected from SciVal, and the collaboration network was determined using degree, closeness, betweenness centralities, and PageRank. Hence, key researchers were identified based on their centrality metrics. The dataset contained 7,155 publications, thus reflecting the contributions of a total of 243 authors. The results of our data analysis demonstrated that key researchers can be identified via CNA; this aspect was not evident from the results of the most productive researchers. Additionally, on the basis of the results, the implications and limitations of this study were analyzed.

Evaluation of solids removal and optimisation of backwashing for an upflow stormwater filtration system utilising novel floating fibrous media.

Although filtration devices are already widely used for stormwater runoff treatment, there are much to be improved to ensure the required performance. Additionally, the performance of a device should be verified before on-site installation. In this context, an upflow filtration system using novel high porosity floating fibrous media formed into spherical shape was proposed and evaluated for solid capture and backwashing. At filtration velocities of 20-40 m/h, the maximum head loss was about 2 cm even under a solid load of 30 kg/m2, and suspended solid (SS) removal efficiency was >96% throughout 300 min. A considerable amount of SS was removed in the pretreatment chamber, so the load on the media was reduced. Several models were tried to describe the solid capture in the media. The coefficients of solid attachment/detachment showed good correlations with filtration velocity. Other parameters indicated a variation of solid capture and permeability, which is unique to the media in this study. The backwashing with air and water for 1-2 min each showed good head loss recovery under the SS load up to 550-600 kg/m2, and the SS discharge was more efficient when the stagnant water was drained before water backwashing. The results in this study suggest the high potential of the combination of fibrous media and upflow filtration system for the efficient control of the nonpoint source pollutants in stormwater runoff.

Road-deposited sediments mediating the transfer of anthropogenic organic matter to stormwater runoff.

It has been regarded that road-deposited sediment (RDS) is one of the important sinks of anthropogenic pollutants as well as the major source of pollutants in stormwater runoff. However, the role of RDS, as a mediator of pollutants to the stormwater runoff, has not yet been investigated so far. Therefore, in this study, the leaching of dissolved pollutants, especially dissolved organic matter (DOM) from RDS, in synthetic precipitation was investigated. A significant amount of metals, nutrients, dissolved compounds, and DOM was leached. The leaching of DOM during 10 sequential leachings was 1811.3 and 2301.7 mg C/kg for larger (63 µm-2 mm) and smaller (< 63 µm) RDS, respectively. The results of UV/Vis spectroscopy, fluorescence spectroscopy, and size exclusion chromatography showed that the leached DOM was of anthropogenic/abiotic origins with lower molecular weight and humification degree. It is ubiquitous in stormwater runoff and industrial discharges and differs from natural organic matter. The results strongly suggest that RDS is an important mediator transferring anthropogenic pollutants to stormwater runoff. In addition, the removal of RDS, such as sweeping, would significantly reduce the pollutants input to the runoff.

Efficient removal of 17α-ethinylestradiol from secondary wastewater treatment effluent by a biofilm process incorporating biogenic manganese oxide and Pseudomonas putida strain MnB1.

This study proposes a biofilm process to immobilize biogenic manganese oxide (BMO) and Pseudomonas putida MnB1 (BMO-MnB1), which shows excellent synergistic effects for 17α-ethinylestradiol (EE2) from secondary wastewater treatment effluent (WWTE). Modified granular activated carbon (M-GAC) was used as the packing carrier, inoculated with Pseudomonas putida MnB1 and Mn(II) to form the BMO-MnB1 biofilm. Feasibility tests were performed to compare the EE2 removal efficiency with that of the conventional biofilm process (BAC) for heterogeneous microbial communities. Results show that in the BAC, EE2 was removed mainly by adsorption, with biodegradation contributing only slightly to the overall performance. In contrast, the BMO-MnB1 biofilter outperformed the BAC. Furthermore, less than 4% of the total EE2 removed was extracted from the biofilter medium over 150 days of operation, confirming that EE2 was biodegraded by P. putida MnB1 or chemically oxidized by BMO. Our results suggest that BMO-MnB1 biofilm processes have high potential for practical applications in removal of endocrine disrupting compounds from wastewater effluent.

Advanced oxidative degradation of acetaminophen by carbon catalysts: Radical vs non-radical pathways.

Two representative carbon catalysts, granular activated carbon (GAC) and carbon nanotube (CNT) were selected for the degradation of acetaminophen (ACT) by persulfate (PS) activation. In this study, the materials characterization study indicated that the surface functional groups and surface area of the GAC were more abundant and larger, respectively, than the CNT. Whereas the contribution of sp2 and CO groups of the CNT was superior to the GAC; the structural defect levels and surface charging characteristics (pHPZC) were similar in both. The mass-based pseudo-first-order reaction rate constant of the CNT was 1.5 m-1 g-1, which was 50 times higher than that of the GAC (0.03 m-1 g-1). Radical and non-radical pathways were evaluated for catalytic reactions by the GAC/PS and CNT/PS systems, respectively. Experimental results using scavenger tests, linear voltammetry, and electron spin resonance (ESR) showed that the radical pathway was dominant in the GAC/PS system, whereas the non-radical pathway was dominant in the CNT/PS systems. To confirm this, the influence of affecting factors such as initial ACT concentration, the dosage of oxidant (PS), and initial pH were also investigated and compared for the two systems. The results showed that the catalytic activity of the GAC/PS system was highly dependent on initial concentrations of ACT and PS, while these were less influential in the CNT/PS system. The removal efficiency of ACT was not affected under a pH of 3-7 in both systems. Reusability experiments were conducted five times, and both the CNT/PS and GAC/PS systems demonstrated that the removal rate of ACT did not notably decrease with the number of experiment repetitions. This means that the application of a carbon catalyst to treat pharmaceutical contaminants in wastewater is effective.

Ecological impact of the antibiotic ciprofloxacin on microbial community of aerobic activated sludge.

This study investigated the effects and fate of the antibiotic ciprofloxacin (CIP) at environmentally relevant levels (50-500 µg/L) in activated sludge (AS) microbial communities under aerobic conditions. Exposure to 500 µg/L of CIP decreased species diversity by about 20% and significantly altered the phylogenetic structure of AS communities compared to those of control communities (no CIP exposure), while there were no significant changes upon exposure to 50 µg/L of CIP. Analysis of community composition revealed that exposure to 500 µg/L of CIP significantly reduced the relative abundance of Rhodobacteraceae and Nakamurellaceae by more than tenfold. These species frequently occur in AS communities across many full-scale wastewater treatment plants and are involved in key ecosystem functions (i.e., organic matter and nitrogen removal). Our analyses showed that 50-500 µg/L CIP was poorly removed in AS (about 20% removal), implying that the majority of CIP from AS processes may be released with either their effluents or waste sludge. We therefore strongly recommend further research on CIP residuals and/or post-treatment processes (e.g., anaerobic digestion) for waste streams that may cause ecological risks in receiving water bodies.

Controlled formation of magnetic yolk-shell structures with enhanced catalytic activity for removal of acetaminophen in a heterogeneous fenton-like system.

Encapsulating magnetic nanoparticles in a silica shell is a promising approach in many research fields. We recently demonstrated that the magnetic yolk-shell structure of Fe3O4@SiO2, which consists of an inner magnetite core and outer silica shell separated by a hollow void space, and its modified counterparts can be used as an effective catalyst for removal of acetaminophen in a heterogeneous Fenton-like reaction. The present study develops this approach further in an effort to design an effective procedure for preparing an optimum yolk-shell structure capable of greater catalytic performance. We investigated the use of a controlled synthesis strategy to fabricate an Fe3O4@SiO2 yolk-shell structure under varying conditions. Our focus was a single-step process that examines the effects of Stöber solution temperature, tetraethyl orthosilicate (TEOS) and hexadecyltrimethylammonium bromide (CTAB) concentrations, ethanol and water volume ratio, incubation time, and temperature on Fe3O4@SiO2 textural morphologies. The catalytic performance of the prepared materials was evaluated through oxidative degradation of acetaminophen in a heterogeneous Fenton-like reaction. Field emission transmission electron microscopy observation showed that magnetic yolk-shell structures with appropriate diameter, shell thickness, and hollow void space could be generated through tight control of synthesis conditions. Particle size and hollow void space increased when TEOS concentration increased from 22.10 to 88.50 mM. Hollow void space also increased as incubation time increased from 24 h to 72 h or incubation temperature increased from 50 to 90 °C. However, a yolk-shell structure did not form at a TEOS concentration of 11.10 mM, an incubation time of 3 h, or with an inappropriate ratio of ethyl alcohol and deionized water. Catalytic activity for degradation of acetaminophen increased with increasing hollow void space and thinning silica shell. In addition, the selected appropriate materials exhibited effective catalytic performance over five cycles of regeneration. This study demonstrates the significance of controlling the formation of yolk-shell structures, which enabled us to produce Fe3O4@SiO2 yolk-shell structures of desired and predictable size, hollow void space volume, and shell thickness for higher catalytic performance in degradation of pharmaceuticals in heterogeneous Fenton-like systems.

Reduction of non-point source contaminants associated with road-deposited sediments by sweeping.

Road-deposited sediments (RDS) on an expressway, residual RDS collected after sweeping, and RDS removed by means of sweeping were analyzed to evaluate the degree to which sweeping removed various non-point source contaminants. The total RDS load was 393.1 ± 80.3 kg/km and the RDS, residual RDS, and swept RDS were all highly polluted with organics, nutrients, and metals. Among the metals studied, Cu, Zn, Pb, Ni, Ca, and Fe were significantly enriched, and most of the contaminants were associated with particles within the size range from 63 µm to 2 mm. Sweeping reduced RDS and its associated contaminants by 33.3-49.1% on average. We also measured the biological oxygen demand (BOD) of RDS in the present work, representing to our knowledge the first time that this has been done; we found that RDS contains a significant amount of biodegradable organics and that the reduction of BOD by sweeping was higher than that of other contaminants. Significant correlations were found between the contaminants measured, indicating that the organics and the metals originated from both exhaust and non-exhaust particles. Meanwhile, the concentrations of Cu and Ni were higher in 63 µm-2 mm particles than in smaller particles, suggesting that some metals in RDS likely exist intrinsically in particles, rather than only as adsorbates on particle surfaces. Overall, the results in this study showed that sweeping to collect RDS can be a good alternative for reduction of contaminants in runoff.

Oxidative degradation of the antibiotic oxytetracycline by Cu@Fe3O4 core-shell nanoparticles.

A core-shell nanostructure composed of zero-valent Cu (core) and Fe3O4 (shell) (Cu@Fe3O4) was prepared by a simple reduction method and was evaluated for the degradation of oxytetracycline (OTC), an antibiotic. The Cu core and the Fe3O4 shell were verified by X-ray diffractometry (XRD) and transmission electron microscopy. The optimal molar ratio of [Cu]/[Fe] (1/1) in Cu@Fe3O4 created an outstanding synergic effect, leading to >99% OTC degradation as well as H2O2 decomposition within 10min at the reaction conditions of 1g/L Cu@Fe3O4, 20mg/L OTC, 20mM H2O2, and pH3.0 (and even at pH9.0). The OTC degradation rate by Cu@Fe3O4 was higher than obtained using single nanoparticle of Cu or Fe3O4. The results of the study using radical scavengers showed that OH is the major reactive oxygen species contributing to the OTC degradation. Finally, good stability, reusability, and magnetic separation were obtained with approximately 97% OTC degradation and no notable change in XRD patterns after the Cu@Fe3O4 catalyst was reused five times. These results demonstrate that Cu@Fe3O4 is a novel prospective candidate for the pharmaceutical and personal care products degradation in the aqueous phase.

Cu@Fe3O4 core-shell nanoparticle-catalyzed oxidative degradation of the antibiotic oxytetracycline in pre-treated landfill leachate.

Novel Cu@Fe3O4 core-shell nanoparticles prepared via a simple reduction method were evaluated for degradation of oxytetracycline (OTC) in pre-treated leachate (Lp-TREA) (leachate treated by conventional methods). Changes in the characteristics of dissolved organic matter (DOM) in the leachate were also investigated to gain a better understanding of the effects of DOM on the performance of Cu@Fe3O4. An excellent OTC degradation of >99% was achieved within 30 min under conditions of 1 g/L Cu@Fe3O4, 20 mg/L OTC, 20 mM H2O2, and initial pH 3.0, which was similar to the efficiency obtained in deionized water (90% even at pH 9.05). Humic acid (HA) and fulvic acid (FA) were completely degraded at initial pH 3, while aromatic protein (AP) with 32.7% of 1-3 kDa constituents were totally transformed to 0.5-1 kDa compounds, and 17% < 0.5 kDa material was degraded. The OTC removal rate decreased gradually as Cu@Fe3O4 was repeatedly used, but it was significantly enhanced when Cu@Fe3O4 was washed after five uses to remove the organic matter on its surface. The results suggest that Cu@Fe3O4 is a promising and effective catalyst for pharmaceutical and personal care product degradation in landfill leachates.

Synergistic effects of biogenic manganese oxide and Mn(II)-oxidizing bacterium Pseudomonas putida strain MnB1 on the degradation of 17 α-ethinylestradiol.

While biogenic manganese oxide (BMO) generated via the oxidation of Mn(II) by the Mn-oxidizing bacteria (MOB) have received attention, the relative roles of biological activity by MOB themselves were not clearly investigated. In this study, the synergistic effects of BMO and MOB Pseudomonas putida strain MnB1 on the degradation of 17α-ethinylestradiol (EE2) was investigated. Experiments with BMO in the presence of P. putida MnB1 showed 15-fold higher removal than that with BMO alone, suggesting that EE2 degradation was mediated by the biological activity of MOB as well as abiotic reaction by BMO. Trapping experiments with pyrophosphate (PP) proved that Mn(III) intermediate formed during the biological process from Mn (II) to Mn (IV) contribute much to the EE2 removal. Also, sharp decreases in EE2 removal were observed when microbial activity was inactivated by heat treatment or sodium azide. From this study, the EE2 removal mechanisms by BMO in the presence P. putida MnB1 are described as follows: (1) abiotic oxidation of EE2 by BMO occurs. (2) P. putida MnB1 indirectly oxidizes EE2 by transferring electrons from the Mn (III) intermediate. (3) P. putida MnB1 continuously re-oxidizes the Mn(II) released from the oxidative degradation of EE2 by BMO, generating new Mn(III)-intermediates or BMO.

Nonsacrificial Template Synthesis of Magnetic-Based Yolk-Shell Nanostructures for the Removal of Acetaminophen in Fenton-like Systems.

Recently, yolk-shell structured materials with active metal cores have received considerable attention in heterogeneous Fenton-like systems, which have excellent catalytic performance. In this study, we initially attempted the nonsacrificial template synthesis of yolk-shell structured nanoparticles with magnetite cores encapsulated in a mesoporous silica shell (Fe3O4@SiO2) via a modified sol-gel process and then evaluated their catalytic activity for acetaminophen degradation in Fenton-like systems. Second, copper nanoparticles were decorated on the surface of the Fe3O4@SiO2 microspheres (Fe3O4@SiO2@Cu) to enhance the catalytic activity. The morphological, structural, and physicochemical properties of the prepared materials were characterized via X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, field emission transmission electron microscopy, nitrogen adsorption-desorption isotherms, specific surface area, ζ-potential, magnetic properties, and Fourier transform infrared spectroscopy. The results demonstrated a successful fabrication of the targeted materials. The yolk-shell structured materials possess a spherical morphology with an active core, protective shell, and hollow void. The Fe3O4@SiO2 and Fe3O4@SiO2@Cu variants showed acetaminophen removal rates significantly higher compared to those of their counterparts, i.e., the Fe3O4 and Fe3O4@Cu core-shell structures. Fe3O4@SiO2@Cu showed that the copper nanoparticles were firmly immobilized on the mesoporous silica shell, dramatically improving the catalytic performance. Both the yolk-shell structured Fe3O4@SiO2 and Fe3O4@SiO2@Cu exhibited good separation and satisfactory regeneration properties, which could be recycled six times without any obvious decline in catalytic activity. Overall, the results of this study suggested that Fe3O4@SiO2 and Fe3O4@SiO2@Cu yolk-shell nanostructures could be promising catalysts for a heterogeneous Fenton-like system by which the removal of emerging contaminants can be greatly improved.

Pollutant characteristics of road deposited sediments collected by road sweeping.

Road deposited sediments (RDS) swept from highways in South Korea were characterized to quantitatively evaluate the reduction in non-point source pollutants by sweeping. The swept RDS consisted primarily of sand (63 µm to 2 mm) particles (80.34 ± 8.33% of total weight) highly contaminated by organics, nutrients and heavy metals. The average concentrations of total organic carbon (TOC), biochemical oxygen demand (BOD), volatile solids (VS), total nitrogen (T-N), and total phosphorus (T-P) were 20.17 ± 9.13, 1.04 ± 0.62, 39.92 ± 16.55, 1.99 ± 0.96, and 0.54 ± 0.19 g kg(-1) (±one standard deviation), respectively, for 63 µm to 2 mm RDS. The concentrations of the pollutants were high for RDS smaller than 63 µm, but most of the mass was associated with the 63 µm to 2 mm RDS. The results suggest that the pollutants associated with RDS swept from highways originated mainly from engine wear, exhaust emissions, and tire wear. These results were different from the RDS on roads in residential and commercial areas, where natural particles and brake wear contribute significantly to RDS. In addition, the reductions in TOC, BOD, VS, T-N, T-P, Cu, Pb, Zn, Fe, and As based on the swept RDS measurements were calculated to be 3,355.3, 175.1, 6,621.4, 323.0, 88.3, 30.3, 13.7, 1.0, 303.4, 11,198.7, and 0.4 g km(-1), respectively.

Inhibition of nitrate reduction by NaCl adsorption on a nano-zero-valent iron surface during a concentrate treatment for water reuse.

Nanoscale zero-valent iron (NZVI) has been considered as a possible material to treat water and wastewater. However, it is necessary to verify the effect of the matrix components in different types of target water. In this study, different effects depending on the sodium chloride (NaCl) concentration on reductions of nitrates and on the characteristics of NZVI were investigated. Although NaCl is known as a promoter of iron corrosion, a high concentration of NaCl (>3 g/L) has a significant inhibition effect on the degree of NZVI reactivity towards nitrate. The experimental results were interpreted by a Langmuir-Hinshelwood-Hougen-Watson reaction in terms of inhibition, and the decreased NZVI reactivity could be explained by the increase in the inhibition constant. As a result of a chloride concentration analysis, it was verified that 7.7-26.5% of chloride was adsorbed onto the surface of NZVI. Moreover, the change of the iron corrosion product under different NaCl concentrations was investigated by a surface analysis of spent NZVI. Magnetite was the main product, with a low NaCl concentration (0.5 g/L), whereas amorphous iron hydroxide was observed at a high concentration (12 g/L). Though the surface was changed to permeable iron hydroxide, the Fe(0) in the core was not completely oxidized. Therefore, the inhibition effect of NaCl could be explained as the competitive adsorption of chloride and nitrate.

Effects of ozonation and coagulation on effluent organic matter characteristics and ultrafiltration membrane fouling.

Effluent organic matter (EfOM) is the major cause of fouling in the low pressure membranes process for wastewater reuse. Coagulation and oxidation of biological wastewater treatment effluent have been applied for the fouling control of microfiltration membranes. However, the change in EfOM structure by pre-treatments has not been clearly identified. The changes of EfOM characteristics induced by coagulation and ozonation were investigated through size exclusion chromatography, UV/Vis spectrophotometry, fluorescence spectrophotometry and titrimetric analysis to identify the mechanisms in the reduction of ultrafiltration (UF) membrane fouling. The results indicated that reduction of flux decline by coagulation was due to modified characteristics of dissolved organic carbon (DOC) content. Total concentration of DOC was not reduced by ozonation. However, the mass fraction of the molecules with molecular weight larger than 5 kDa, fluorescence intensity, aromaticity, highly condensed chromophores, average molecular weight and soluble microbial byproducts decreased greatly after ozonation. These results indicated that EfOM was partially oxidized by ozonation to low molecular weight, highly charged compounds with abundant electron-withdrawing functional groups, which are favourable for alleviating UF membrane flux decline.