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Due to the high cost of presently utilized Pt/C catalysts, a quick and sustainable synthesis of electrocatalysts made of cost-effective and earth-abundant metals is urgently needed. In this work, we demonstrated a mechanochemically synthesized cobalt nanoparticles supported on N and S doped carbons derived from a solid-state-reaction between zinc acetate and 2-amino thiazole as metal, organic ligand in presence of cobalt (Co) metal ions ZnxCox(C3H4N2S). Pyrolysis of the ZnxCox(C3H4N2S) produced, Co/NSC catalyst in which Co nanoparticles are evenly distributed on the nitrogen and sulfur doped carbon support. The Co/NSC catalyst have been characterized with various physical and electrochemical characterization techniques. The Co content in the ZnxCox(C3H4N2S) is carefully adjusted by varying the Co content and the optimized Co/NSC-3 catalyst is subjected to the oxygen reduction reaction in 0.1 M HClO4 electrolyte. The optimized Co/NSC-3 catalyst reveals acceptable ORR activity with the half-wave potential of ~0.63 V vs. RHE in acidic electrolytes. In addition, the Co/NSC-3 catalyst showed excellent stability with no loss in the ORR activity after 10,000 potential cycles. When applied as cathode catalysts in dual chamber microbial fuel cells, the Co/NCS catalyst delivered satisfactory volumetric power density in comparison with Pt/C.

MXene is a growing class of two-dimensional layered material that has been showed promising application in various energy storage and conversion technologies, due to its unique electrical, mechanical, surface and electrocatalytic properties. One of the promising applications of MXene is, its definite role as durable catalyst support material, for fuel cell anodic/cathodic reactions. Very recently, MXene supported catalysts have been identified as potential and stable support for various Pt and non-Pt metals designed for cathodic oxygen reduction reaction and it has been proved as excellent material to enhance the oxygen reduction kinetics. This had motivated the researchers to explore MXene as catalyst support for anodic methanol/ethanol oxidation reactions. In this review, recent developments in experimental and theoretical research on MXene-based electrocatalysts for the methanol/ethanol oxidation reactions are examined and overviewed. After careful examination of the available literature, we presume that MXene supported electrocatalyst showed enhanced methanol/ethanol oxidation kinetics and therefore believed to have tremendous opportunities as durable catalyst support for alcohol fuel cells. However, researchers also consider several limitations and challenges that must be addressed for efficient application of MXenes as catalyst supports. Therefore, current research on MXenes with respect to the methanol/ethanol oxidation are discussed, with a focus on synthesis strategies, oxidation kinetics, and factors responsible for enhancing the electrocatalytic performance. Several strategies for the further development of efficient and durable MXene supported catalysts are also proposed.

In response to the finding of chironomid larvae in tap water, South Korea’s water treatment system has stepped up water quality monitoring. However, due to the challenging nature of larval behavior, effective elimination remains difficult despite the use of various purification techniques such as coagulation, sedimentation, filtration, and disinfection. Based on it, the aim of this study is to evaluate the effectiveness of coagulation and chlorination in inactivating chironomid larvae and investigate their behavior. The coagulation experiment tested how the behavior of the larvae changed in water with a high turbidity level of ±100 mg/L and 2 mg/L Al3+ as a coagulant, compared to water with a lower turbidity level of ±30 mg/L and 1 mg/L of Al3+ as a coagulant. The larvae were exposed to various doses of chlorine (0.5–20 mg/L as Cl) in 500 mL beaker glasses. The behavioral activity of the larvae was observed at different time points for 5 days. It was found that chironomid larvae exhibit different responses to exposure to coagulant and chlorine, with coagulation causing the formation of flocs that cover the larval body as a protective measure. Conversely, exposure to chlorine causes a decrease in activity and growth, leading to the death of the larvae and subsequent melting. The results showed that the first instar larvae dead after 48 h of exposure to coagulation treatment, while the first instar larvae exposed to chlorination experienced mortality after a mere 5 min of exposure to 10–20 mg/L as Cl. The larvae can still grow and transform into pupae and adults, especially during the third and fourth instars, even after exposure to coagulant and chlorine with low dosage. These findings suggest that the floc generated during coagulation must be thoroughly cleaned, as it may contain larvae that can persist and develop further. Furthermore, the presence of larvae during the chlorination process highlights the need for alternative, more effective oxidants to be utilized in place of the conventional chlorine treatment.

Microbial fuel cells, an emerging technology has been paid a great attention in recent years, due to its unique advantages in treating wastewater to portable water, together with the generation of useful electricity, with the help of bio-active anodes and electrochemical cathodes, simultaneously. When applying this technology in a practical scale, the indigenous bacteria present in the wastewater catalyze the breakdown of organic matter in the anode compartment, with generation of electrons and in the cathode compartment an oxidant, usually the oxygen present in the air, take the electron and reduce to water (oxygen reduction reaction, ORR). An ideal ORR catalyst should be highly active, durable, scalable, and most importantly it should be cost effective. Generally, platinum-based catalyst is utilized, however, due to the high cost of Pt based catalysts, many cheap, cost effective catalyst have been identified as efficient ORR catalyst. Carbon based catalysts known to possess good electronic conductivity, desirable surface area, high stability, together when doped with heteroatoms and cheap metals is found to remarkably enhance the ORR activity. Although a lot of research has been done in view of developing carbon based cheap, cost-effective catalysts, still their collective information has not been reviewed. In this article we anticipate reviewing various non-precious metal and metal-free catalysts that are synthesized and investigated for MFCs, factors that affect the ORR activity, catalyst designing strategies, membranes utilized for MFCs, together with the cost comparison of non-precious and metal-free catalysts with respect to Pt based catalysts have been summarized. We anticipate that this review could offer researchers an overview of the catalyst developed so far in the literatures and provides a direction to the young researchers.

Electrocatalysts for oxygen reduction reaction have been the study of interest because of their importance in various energy storage and conversion reactions. Though platinum-based catalysts are found to be the most active catalysts for oxygen reduction reactions, their high cost and scarcity have led researchers to discover alternative active and cost-effective catalysts. In this regard, heteroatom- and metalloid-doped catalysts were explored as possible alternatives to traditional platinum-based catalysts. Consequently, a large number of heteroatom- and metalloid-doped catalysts have been synthesized and evaluated for oxygen reduction activity. Synergistic catalysts, with dual-doped, tri-doped, and multi-heteroatom-doped catalysts, were also synthesized by doping more than one heteroatom. In this review, we discuss the fundamental principles and reasons behind the origin of ORR catalysis of heteroatom- and metalloid-doped catalysts discussed with the support of literatures.

We conducted an experiment to confirm the passability of chironomid larvae (Glyptotendipes tokunagai) in granular activated carbon (GAC) used in water treatment plants. After injecting larvae at different growth stages (first through fourth instars) into circular columns filled with GAC, the number of individuals and their locations within the GAC columns were recorded after 168 h. We found that more than 80% of the injected larvae in the first instar and 3.3% in the second instar passed, whereas none from the third and fourth instars had passed through the column. The second instar larvae were evenly distributed within the column, whereas the third and fourth instar larvae were mostly distributed within 10 cm of the upper layer of the GAC. Our results demonstrate the passability of chironomid larvae in GAC and can be used as basic information for water quality management in water treatment plants.

Water pollution can be a severe problem for life and environmental health. Anthropogenic activity is one of the factors that can produce pollution in the water. Wastewater treatment plant (WWTP) is a solution to control pollutants from various anthropogenic activities. This study aims to investigate water quality parameters in several public WWTPs in Daegu City through a temporal and spatial variation approach. Wastewater from industrial sources has resulted in difficulties in the COD removal process (removal efficiencies: 85.3% - 92.7%) due to the presence of non-biodegradable organic content. Whereas Total Nitrogen (TN) became the most challenging pollutant to be removed at each WWTP with removal efficiencies ranging from 70.1% - 81.4%. Further effort is needed to increase the T-N removal efficiency in each WWTP and COD removal efficiency for industrial wastewater.

Microplastics (MPs) in the aquatic environment has recently been documented as an environmental threat due to their negative impact on the ecosystem. Wastewater treatment plants (WWTPs) are expected to be main recipients of microplastics entering into freshwater. Everyday, continuously, treated water containing microplastics from WWTP is discharged in large quantities. The aim of this article is providing a comprehensive knowledge to better understand characteristics of MPs in wastewater, the fate and transport of MPs during treatment process in WWTP, abundance of MPs discharged from WWTP and removal efficiency of MPs in lab scale and existing technologies at WWTPs. The concentration of microplastics varying from 0-91 MP/L (final effluent) and approximately > 32 MP/㎥ in fresh water. Microplastics can be removed in the primary, secondary and tertiary treatment with the removal efficiency were 41%-65%, 0.2%-14% ,and 0.2-14%, respectively. Treated water and sewage sludge act as direct and indirect pollutants into freshwater. The presence of microplastics in the environment has potential as a threat to the aquatic organism (ecotoxicological and ecological risk). Some studies have tried to remove microplastics in wastewater using artificial microplastic with performance with a range of 60-99%. On the other hand, it is necessary to introduce new technology and improve existing technologies in the WWTP that can be correctly used to remove microplastic from wastewater.

This study investigated the removal of microplastics from different treatment stages in three WWTPs and examined the performance of tertiary treatment that was done by coagulation and different technologies such as ozone (WWTP-A), membrane disc-filter (WWTP-B), and rapid sand filtration (WWTP-C). The results showed that the primary and secondary treatment processes effectively remove microplastics from wastewater with efficiencies ranging between 75% and 91.9%. The removal efficiency increased further to >98% after tertiary treatment. Microbeads and fragments were the major types of microplastics found in all wastewater sampling points. Microbeads found in the wastewater samples were classified as primary microplastics, that mainly came from personal care products, whereas secondary microplastics consisted of fragments, fibers, and sheets that were generated mainly due to fragmentation of larger plastics. Microplastics were still found in a high concentration in the final effluent, especially from WWTP-B, which is discharged into the Geumho river.

Microplastic pollution has been widely studied as a global issue due to increased plastic usage and its effect on human and aquatic life. Microplastics originate from domestic and industrial activities. Wastewater treatment plants (WWTPs) play an important role in removing a significant amount of microplastics; otherwise, they end up in bioaccumulation. This study provides knowledge about the characteristics of microplastics, removal efficiency, and the correlation between wastewater quality and microplastic concentrations from three different WWTPs that differ in the type of biological and advanced wastewater treatment techniques that are believed to play an important role in microplastic removal. Microplastics of different types, such as fragments, fibers, and beads, are identified by using an optical microscope before and after the treatment process at each stage to assess the effect of different treatment techniques. In the screening unit and primary clarifier unit, WWTP-B shows the highest removal efficiency with 74.76% due to a distribution flow system installed before the primary clarifier to ensure a constant flow of wastewater. WWTP-B uses a bioreactor consisting of a filter plate coated with activated carbon (BSTS II) that can enhance the adaptability and adhesion of microorganisms and showed that 91.04% of the microplastic was removed. Furthermore, only WWTP-A and WWTP-B were applied coagulation, followed by the disc filter; they showed significant results in microplastic removal, compared to WWTP-C, which only used a disc filter. In conclusion, from all WWTP, WWTP-B shows good treatment series for removing microplastic in wastewater; however, WWTP-B showed a high rate of microplastic removal; unfortunately, large amounts of microplastics are still released into rivers.

Pt based catalysts represent the state-of-the-art electrocatalyst for electrochemical cathodic oxygen reduction reaction of proton exchange membrane fuel cells. Among Pt based electrocatalysts, Pt-transition metal catalysts have been the most successful in terms of activity. However, the poor structural and chemical stability of Pt-alloy catalysts are challenges. Alternatively, alloying Pt with rare earth metals is considered as one of the effective ways to discover active and durable electrocatalysts for the ORR. The advantages of alloying with rare earth metals bring a substantial change in the electronic properties and their negative alloying energy or enthalpy of formation of alloys provides special driving force to resist against dissolution. Synthesis of Pt-rare earth alloys by a solution phase route is challenging. To date there have been only physical metallurgical methods which help to synthesize them successfully in the form of an alloy, where as traditional wet chemical synthesis methods results rare earth turns into metal oxide/hydroxide. This article reviews several studies put forward to synthesize Pt-rare earth alloy/oxide catalysts by various physical metallurgical methods and solution-based synthesis protocols and their effect on the improvement of ORR activity.

River water quality of Daegu city has been fluctuating for the last several years. This condition requires attention to avoid the possibility of severe water quality degradation. This study aims to identify temporal and spatial distribution, sources of pollutants, and the dominance of specific pollutants on the Nakdong River. River water quality data with a duration of 5 years has been collected and analyzed statistically and combined with Geographic Information System (GIS). The data included BOD, COD, SS, TN, TP, Chl-a, and TOC. The results showed a repetition of a period of decline in river water quality due to the algal bloom phenomenon. This phenomenon closely related to the BOD concentration in the river. Also, the emergence of TOC in high concentrations requires special attention so that it does not become an ongoing problem. COD has the most positive correlation with TOC. This problem becomes serious because it was located at the inlet of water treatment plant in this river. Controlling BOD and COD concentration, especially from effluent of wastewater treatment plant, might become one of the relevant solutions to restrain river water quality degradation. The results of further identification indicate the possibility of nonpoint sources influence, which resulting the river water quality decrease.

Rational, low cost, stable and more realistic synthesis of electrocatalysts comprising of earth abundant metals alterative to platinum-based catalysts is highly required for fuel cells. In this work, we demonstrate 2D nanosheet catalyst from metal organic frame works with zinc and 2-amino thiazole as organic ligand in presence of cobalt metal ions. The special bonding configurations of zinc with 2-amino thiazole ligand resulted in formation of 2D ZnxCo1-x(C3H4N2S) and the pyrolysis of 2D ZnxCo1-x(C3H4N2S) resulted in Co@NSC electrocatalyst. The electrochemical oxygen reduction reaction analysis of the Co@NSC catalyst reveals excellent activity with the half-wave potential of 0.88 V, similar to the commercial Pt/C catalyst. Moreover, Co@NSC catalyst also show the ultra-low HO2− formation bellow

Quercetin-3-O-α-l-rhamnopyranosyl(1→2)-O-α-l-rhamnopyranoside (QDR) was isolated from the remaining underground parts of Curcuma longa after harvesting the medicinal parts, and the antioxidant activities in vitro and lifespan-extending effect of QDR were elucidated using the Caenorhabditis elegans model system. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect of QDR showed similar potent activities in comparison with vitamin C. QDR also showed strong superoxide quenching activities as measured by the riboflavin- and xanthine-originated superoxide quenching activities. QDR demonstrated potent lifespan extension of worms under normal culture condition. Subsequently, the protective effect of QDR on the stress conditions such as thermal and oxidative stresses was determined. In the case of heat stress, QDR-treated worms exhibited enhanced survival rate, as compared to control worms. In addition, QDR-fed worms lived longer than control worms under oxidative stress induced by paraquat. To verify the possible mechanism of QDR-mediated increased lifespan and stress resistance of worms, we investigated whether QDR might alter superoxide dismutase (SOD) activity and intracellular reactive oxygen species (ROS) levels. Our results showed that QDR was able to elevate SOD activity of worms and reduce intracellular ROS accumulation in a dose-dependent manner.

In this study, coagulation efficiencies for each growth phase of Microcystis aeruginosa, one of the main species involved in eutrophication in South Korea, were examined at the laboratory scale to obtain data on removal characteristics of this organism during the coagulation process. This study also defines the optimum growth conditions to culture M. aeruginosa in a laboratory environment. The optimum growth conditions of M. aeruginosa were at a concentration of 0.8 mg/L of phosphorus, a concentration of 10 mg/L of nitrogen, 2,000 lx of illumination, and an alkali condition. Coagulation efficiency varies with growth phases, which is due to the different rates of metabolism at each phase. Results provide the optimal growth conditions to obtain M. aeruginosa in a laboratory, and characterize coagulation efficiencies at each growth stage for water treatment facilities to establish procedures to manage eutrophicated water.

An analysis of fouling material and the effects of chemical cleaning were examined for a reverse osmosis (RO) membrane, which was used for the treatment of wastewater from a rolling mill process in the steel industry. The bulk foulant accumulated in the membrane module consisted mainly of CaSO 4 ·2H 2 O, and the organic contaminants were contained at a very low level. The test pieces obtained from the exhausted RO membrane module (spiral-wound type) were used to examine chemical cleaning with the following solutions: acid and alkaline solutions with EDTA added, 50% methanol, and 10% ethyleneglycol monobutyrate (EGMB). Although a major component of the fouling material was calcium salt, the acid or alkaline solution containing EDTA did not promote the effective recovery of the water flux. On the other hand, cleaning with 50% methanol or 10% EGME solution increased the water flux significantly. The atomic force microscopy images of the membrane surface indicated that relatively large particles accumulated at the surface of the fouled membranes, and the large particles remained even after acid or alkaline cleaning. In the case of EGMB cleaning after alkaline cleaning, large particles did not remain, and uniform and fine particles were observed. The results that calcium salt, a major fouling material, was not removed effectively with the acid and alkaline solution may be due to trace organic materials in the fouling layer that act as a binder for inorganic fouling materials.

Phosphate removal is important to control eutrophication and an ion exchange process is one of several treatment processes for this purpose. Hydrotalcite compounds (HTALs) are useful as adsorbents for phosphate removal because of their ion exchange properties. In this study, the adsorption properties of a granular synthetic HTAL for phosphate and the method of regeneration of the granular HTAL were examined. The adsorption isotherm of the granular HTAL was approximated by a modified Langmuir type, and the maximum adsorption capacity was 47.3 mg P g(-1), which corresponded to the content of HTAL in the granular one. Phosphate adsorbed on the HTAL was effectively desorbed with alkaline NaCl solutions and the HTAL was regenerated with 25 w/v% MgCl(2) solution. The regenerated HTAL could be reused repeatedly for the phosphate removal. Phosphate in the exhausted desorption solution was recovered as a precipitate of calcium phosphate by addition of CaCl(2), and the residual exhausted desorption solution could be also reused after supplying NaOH. The results suggest the possibility of an effective system for phosphate removal and recovery, which includes the following processes: adsorption, desorption, recovery of phosphate, and regeneration of the HTAL and the desorption solution.

Varying amounts of exfoliated graphene oxide (GO) are systematically incorporated into nanoscale polyacrylonitrile (PAN) fibers via an electrospinning method. Subsequent treatment of the PAN–GO composite nanofibers under a moderate temperature and high pressure leads to the formation of membrane sheets with enhanced mechanical properties. scanning electron microscope, Fourier transform infrared spectroscopy, and contact angle measurements confirm the successful incorporation of the GO into the PAN nanofiber membranes whose diameter, porosity, and pore size are notably influenced by the amount of the GO content. These composite membranes also exhibit a gradual reduction in the water contact angle as a function of the hydrophilic GO content, resulting in a beneficial property for water purification. In addition, the proper integration of GO into the PAN nanofibers improves the protein rejection rate and water flux during the filtration process, which indicates the possibility of utilizing these types of composite membranes in water treatment systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45858.

The Zn (II) adsorption capacity of lignite and coconut shell-based activated carbon fiber (ACF) was evaluated as a function of initial Zn (II) concentration, temperature and contact time in batch adsorption process in this study. Adsorption uptake increased with initial Zn (II) concentration and temperature. Optimal contact time for the adsorption of Zn (II) ions onto lignite and coconut shell-based ACF was found to be 50 min. Removal percentage decreased from 88.0% to 78.54% with the increment in initial Zn (II) concentration from 5 to 50 mg L−1. Equilibrium data fit well with Langmuir-I isotherm indicating homogeneous monolayer coverage of Zn (II) ions on the adsorbent surface. Maximum monolayer adsorption capacity of Zn (II) ions on ACF was found to be 9.43 mg g−1. Surface morphology and functionality of ACF prior to and after adsorption were characterized by electron microscopy and infrared spectroscopy. Various thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated.