Natural Water Matrices Research Articles

Metronidazole Degradation by UV and UV/H2O2 Advanced Oxidation Processes: Kinetics, Mechanisms, and Effects of Natural Water Matrices.

Advanced oxidation technology represented by hydroxyl radicals has great potential to remove residual antibiotics. In this study, we systematically compared the metronidazole (MTZ) degradation behavior and mechanism in the UV and UV/H2O2 systems at pH 3.00 condition. The results show that the initial reaction rates were 0.147 and 1.47 µM min−1 in the UV and UV/H2O2 systems, respectively. The main reason for the slow direct photolysis of MTZ is the relatively low molar absorption coefficient (2645.44 M−1 cm−1) and quantum yield (5.9 × 10−3 mol Einstein−1). Then, we measured as 2.79 (±0.12) × 109 M−1 s−1 by competitive kinetics, and calculated and as 2.43 (±0.11) × 109 M−1 s−1 and 2.36 × 10−13 M by establishing a kinetic model based on the steady-state hypothesis in our UV/H2O2 system. The contribution of direct photolysis and •OH to the MTZ degradation was 9.9% and 90.1%. •OH plays a major role in the MTZ degradation, and •OH was the main active material in the UV/H2O2 system. This result was also confirmed by MTZ degradation and radicals’ identification experiments. MTZ degradation increases with H2O2 dosage, but excessive H2O2 had the opposite effect. A complex matrix has influence on MTZ degradation. Organic matter could inhibit the degradation of MTZ, and the quenching of the radical was the main reason. promoted the MTZ degradation, while and Cl− had no effect. These results are of fundamental and practical importance in understanding the MTZ degradation, and to help select preferred processes for the optimal removal of antibiotics in natural water bodies, such as rivers, lakes, and groundwater

Preferential interactions of surface-bound engineered single stranded DNA with highly aromatic natural organic matter: Mechanistic insights and implications for optimizing practical aquatic applications

Engineered short-chain single stranded DNA (ssDNA) are emerging materials with various environmental applications, such as aptasensor, selective adsorbent, and hydrological tracer. However, the lack of fundamental understanding on the interactions of such materials with natural organic matter (NOM) hinders the improvement of their application performance in terms of sensitivity, selectivity, and stability. In this study, we investigated the interactions of ssDNA (four strands with systematically varied length and sequence) with two humic acids (Suwannee River humic acid (SRHA) and Aldrich humic acid (AHA)) and two humic-like NOM present in local aquatic matrices (ROM in river water and WOM in wastewater). Detailed, molecular level interaction mechanisms were obtained by probing the colloidal stability of the ssDNA-coated gold nanoparticles, coupled with product characterization using a suite of microscopic and spectroscopic techniques. Our study revealed that π-π interactions and divalent cation bridging were the major mechanisms for ssDNA-NOM interactions. ssDNA preferentially interacted with NOM with high aromaticity (AHA > SRHA/WOM/ROM). With divalent cations present (especially Ca2+), even a small amount of AHA could completely shield ssDNA, whereas the extent of shielding by SRHA/WOM/ROM depended on the relative content of ssDNA and NOM and whether bridges formed. The extent of shielding of ssDNA by NOM provides a potential answer to the reported conflicting effects of natural water matrices on the performance of DNA-based sensors. Taken together, our findings provide insights into the transformations of engineered ssDNA under environmentally relevant conditions as well as implications for their performance optimization in practical aquatic applications (e.g., from DNA design to pretreatment strategy).

Formulation of NZVI-supported lactic acid/PAN membrane with glutathione for enhanced dynamic Cr(VI) removal

The current technologies for production of nanoparticle-membrane are apt to involve complicated multi-step process and/or toxic chemicals and other defects. This study provides a green and clean cryogel manufacture method for fabrication of hydrophilicity Polyacrylonitrile (PAN) membrane with highly porous structure for supporting nano zero-valent iron (NZVI) via a surface modification by employing biodegradable lactic acid. Non-toxic natural compound, glutathione (GSH) was adopted not only as modifiers but also as chelators to promote the capture capacity of hexavalent chromium (Cr(VI)). The specific surface area of the prepared composite (GLPN, 193.16 m2/g) was larger than the previously studied NZVI-membrane (PPN, 131.61 m2/g), and NZVI was distributed uniformly and not agglomerated on the membrane. Compared with NZVI, the efficiency of GLPN removed Cr(VI) has increased by 39.80%. At low pH and Cr(VI) initial concentration, GLPN can completely remove Cr(VI) when the GSH concentration is increased to 50 mM, and the removal efficiency can still reach 86.96% after 6 regenerations. Visual MINTEQ model and experimental results show that the mechanism of GLPN removing Cr(VI) includes the synergy of electrostatic adsorption, chelation, reduction and co-precipitation. The process conforms to two-parameter nonlinear dynamics and Redlich-Peterson isotherm model. This novel strategy shows that GLPN has excellent stability, reducibility and green reproducibility, and can efficiently remove and recycle heavy metal in the natural water matrices or wastewater.

Adsorption mechanisms of metal ions (Pb, Cd, Cu) onto polyamide 6 microplastics: New insight into environmental risks in comparison with natural media in different water matrices

Microplastics (MPs) are ubiquitous in the environment and have a great potential to coexist with metal ions. This work investigated the adsorption–desorption behaviors of three divalent metal ions (Cu, Cd, Pb) on polyamide 6 (PA6) MPs and natural media (riverside soil and marine sediment) and compare their environmental risks. The result showed that the adsorption amounts of metal ions onto PA6 MPs followed the order of Cd(II) (1.210 μmol/g) < Cu(II) (2.299 μmol/g) < Pb(II) (3.756 μmol/g). The adsorption of metal ions on PA6 was significantly affected by water chemistry, including solution pH, salinity, and the concentration of citric acid (CA) and humic acid (HA). Natural water matrices (Yangtze River water and Seawater) enhanced the uptake of three metal ions by PA6 MPs. The analysis of Fourier transform-infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) highlighted the importance of amide groups in controlling the adsorption of metal ions onto PA6 MPs. Site energy distribution indicated that the adsorption of metal ions mainly involved chemisorption. The retention factor (Rf) calculated by the adsorption–desorption behavior of three heavy metal ions indicated that the risk of metal ions posed by PA6 MPs was higher than that of natural media. Among all water matrices, the metal ion/PA6 MPs combinations posed the highest environmental risk in the simulated gastric fluid. This work highlights the behavior of PA6 MPs as metal ions vectors and provides strong evidence the assessment of environmental risk posed by MPs/metal ions combinations, opening new insight into understanding the environmental impacts of MPs.

Mechanistic understanding of the aggregation kinetics of nanoplastics in marine environments: Comparing synthetic and natural water matrices

In this study, the aggregation kinetics of two sizes of polystyrene nanoplastics: 28 nm (NP28) and 220 nm (NP220), were investigated using time-resolved dynamic light scattering. The stability of the plastics was evaluated in: (i) the presence and absence of three natural organic matters (NOM) – the Suwannee River humic acid (HA) and fulvic acid (FA), and alginate (AL), (ii) varying concentrations of divalent salt and in artificial seawater (ASW) and (iii) natural surface waters (NW) with varying salinities. In the absence of NOM, the critical coagulation concentration (CCC) in CaCl2 was independent of particle size. The addition of HA enhanced aggregation via bridging, regardless of the size of the plastics. In contrast, the interaction of the plastics with alginate was size-dependent where alginate appeared to enhance aggregation by encapsulation for NP28 and by gel bridging for NP220, while the FA had little or no effect. In ASW, alginate stabilized the particle suspensions. Generally, the effects of the three NOM were more pronounced for the NP220 compared to the NP28. While the bare NP220 was more stable in natural seawater than in ASW and CaCl2 (at the CCC), there were few significant differences in the attachment efficiencies of the bare NP28 in these water matrices. Finally, in CaCl2, the interaction of nanoplastic aggregates with a model silicon-based surface was less repulsive in the presence of AL or HA than FA. This study highlights the importance of considering the interplay of different particle sizes and complex water chemistries when assessing the fate of nanoplastics in the environment.

In-situ synthesis of N-doped biochar encapsulated Cu(0) nanoparticles with excellent Fenton-like catalytic performance and good environmental stability

Low-valent transition metal catalysts show promising application in the catalytic degradation of organic pollutants in wastewater. However, the catalysts themselves are susceptible to be oxidized and easy to agglomerate, thus reducing the catalytic ability. Herein, a facile in-situ carbonization method is utilized to synthesize N-doped biochar encapsulated zero valent copper (Cu(0)) nanoparticles (Cu@N: C). The formed Cu(0) nanoparticles are uniformly dispersed in biochar. The carbon layers wrapped outside of Cu(0) nanoparticles can present the oxidation of Cu(0) to a certain extent. Therefore, the 12% Cu@N: C catalyst exhibits good environmental stability. The catalytic ability remains basically unchanged after directly exposing it to air for four months. In addition, the 12% Cu@N: C catalyst exhibits excellent catalytic performances for the degradation of various organic pollutants at near neutral pH range (pH = 4.0 ∼ 8.0). Low valent copper (Cu(0)/Cu(Ⅰ)) and pyridinic N both contribute to the excellent catalytic ability. Furthermore, the catalytic performances are less interfered in natural water matrices, and even obviously enhanced in sea water. Based on the experimental and characterization results, a possible catalytic mechanism is also proposed.

High-efficiency and fast removal of As(III) from water by cerium oxide needles decorated macroporous carbon sponge

The deep removal of highly toxic and mobile As(III) from water is challenging but urgently needed. Herein, a cerium oxide (CeO2) needles decorated macroporous carbon sponge (Ce-Ns/MCS) with a strong affinity for As(III) was fabricated for highly efficient removal of As(III). The open structure of Ce-Ns/MCS allows the decorated CeO2 highly accessible for As(III). Ce-Ns/MCS (1 g/L) could remove the As(III) levels (826 μg/L) to less than 10 μg/L within 20 min. Moreover, similar removal efficiency could achieve in a wide pH range (3–11), and the water environmental interference such as coexisting anions and natural organic matter exhibited negligible influence on As(III) removal. The As(III) (68 μg/L) in natural water matrices can be removed to below 10 μg/L within 5 min. Ce-Ns/MCS also possesses structural stability and excellent reusability. In addition, Ce-Ns/MCS could be effectively applied to the fixed-bed operation, and the Ce-Ns/MCS column could purify 4035 bed volume (BV) and 1605 BV effluent from the As(III)-spiked groundwater containing 100 μg/L and 600 μg/L of As(III), respectively. Ce-Ns/MCS could be a prospective practical adsorbent for As(III) remediation because of its excellent performance, without pre-oxidation requirement, and excellent anti-interference.

Activation of peracetic acid via Co3O4 with double-layered hollow structures for the highly efficient removal of sulfonamides: Kinetics insights and assessment of practical applications

Sulfonamides (SAs) have been of ecotoxicological concern for ambient ecosystems due to their widespread application in the veterinary industry. Herein, we developed a powerful advanced oxidation peracetic acid (PAA) activation process for the remediation of SAs by Co3O4 with double-layered hollow structures (Co3O4 DLHSs). Systematic characterization results revealed that the polyporous hollow hierarchical structure endows Co3O4 DLHSs with abundant active reaction sites and enhanced mass transfer rate, which were conducive for improving the PAA activation efficiency. Laser flash photolysis experiment and mechanism studies indicated that organic radical species were dominant reactive species for SAs removal. The present system is also highly effective under natural water matrices and trace SAs concentration (20 μg/L) condition. More importantly, the chlorella acute toxicity of the SAs solution was eliminated during mineralization process, supporting this catalytic system may be efficaciously applied for the remediation of SAs contamination in ambient waterways.

Solar photocatalytic degradation of parabens using UiO-66-NH2

The photocatalytic degradation of methylparaben was investigated under simulated solar light using a synthesised metal–organic framework (UiO-66-NH2). For that purpose, the pollutant was spiked in different water matrices: distilled water, water from Lima River (Northwestern Portugal), and urban wastewater. Complete removal of the methylparaben in distilled water was achieved in 1 h reaction. In natural water matrices, the photocatalytic performance decreased to 70% removal after 3 h reaction, owing to the physical–chemical properties of the water samples. The UiO-66-NH2 photocatalyst revealed high stability under the continuous mode, reaching a steady state in 5 h, from which the removal percentage was kept constant for 25 h. The photocatalytic degradation of methylparaben gave five main reaction byproducts and four short-chain carboxylic acids, identified by LC/ESI-MS and UHPLC analyses, respectively. The mechanism of degradation was investigated by using selective scavengers. Photogenerated holes and superoxide radicals were found as the main species responsible for the degradation of methylparaben. The abatement of other parabens (as ethyl- and propylparaben) was also evaluated, being the conversion influenced by the length of the alkyl side chain. The results of this study give a comprehensive sight into the effective photocatalytic remediation of parabens using UiO-66-NH2.

Identifying water quality and environmental factors that influence indicator and pathogen decay in natural surface waters

Biphasic decay has been observed for indicators and pathogens in bench-scale and in-situ water experiments for decades, however, first-order decay kinetics continue to be applied to persistence data because of their simplicity and ease of application. Model uncertainty introduced by broadly applying first-order decay kinetics to persistence data may lead to erroneous decision making in the fields of water management and protection. As surface waters are exposed to highly variable environmental and water quality factors that influence microbial and viral persistence, it is expected that first-order decay kinetics are not representative of most of the persistence literature for indicators and pathogens in surface water matrices. This review compiled the methods and results of 61 studies that conducted experiments evaluating the persistence of fecal indicator bacteria (FIB), bacteriophages, pathogenic bacteria, viruses, and protozoa in natural surface water matrices. The goals of this review were trifold: (1) collate studies in the literature with data available for future persistence modeling, (2) present the current state of knowledge with regards to the environmental and water quality factors affecting persistence in natural surface waters, and (3) identify recurrent evidence for interactions between the frequently studied factors to inform future factor analyses. Comparing the methods and results across the 61 studies suggest potential interactions between sunlight and water type; sunlight and method of detection; predation and water type; predation and temperature; and water type and method of detection. The majority of the identified literature evaluated FIB or bacteria persistence; future experiments are needed that focus on protozoa, brackish or marine water types, and molecular-based methods of detection.

Hydroxylamine enhanced Fe(II)-activated peracetic acid process for diclofenac degradation: Efficiency, mechanism and effects of various parameters

In this study, a commonly used reducing agent, hydroxylamine (HA), was introduced into Fe(II)/PAA process to improve its oxidation capacity. The HA/Fe(II)/PAA process possessed high oxidation performance for diclofenac degradation even with trace Fe(II) dosage (i.e., 1 μM) at pH of 3.0 to 6.0. Based on electron paramagnetic resonance technology, methyl phenyl sulfoxide (PMSO)-based probe experiments and alcohol quenching experiments, FeIVO2+ and carbon-centered radicals (R-O•) were considered as the primary reactive species responsible for diclofenac elimination. HA accelerated the redox cycle of Fe(III)/Fe(II) and itself was gradually decomposed to N2, N2O, NO2− and NO3−, and the environmentally friendly gas of N2 was considered as the major decomposition product of HA. Four possible degradation pathways of diclofenac were proposed based on seven detected intermediate products. Both elevated dosages of Fe(II) and PAA promoted diclofenac removal. Cl−, HCO3− and SO42− had negligible impacts on diclofenac degradation, while humic acid exhibited an inhibitory effect. The oxidation capacity of HA/Fe(II)/PAA process in natural water matrices and its application to degrade various micropollutants were also investigated. This study proposed a promising strategy for improving the Fe(II)/PAA process and highlighted its potential application in water treatment.

Application of Nanomaterials in Water Treatment: Arsenic and Natural Organic Matter Removal.

Globally, around 150 million people are still supplied with arsenic contaminated drinking water. The groundwaters effected often contain problematic concentrations of natural organic matter (NOM), which plays an important role in releasing As into the aquifer. Thus, this review explores the recent literature relating to the application of various nanomaterials to solve these drinking water supply problems and highlights the work that still needs to be done. After an extensive initial search patent papers were selected based on their quality and relevance to the topic of this review: the use of magnetic nanomaterials based on pure magnetic materials, magnetic composites of carbon/graphene/biochars, polymeric matrices, metal-organic frameworks and mixed-oxide magnetic nanocomposites, as As adsorbents and as photocatalysts for NOM removal. 160 papers relating to the application of nanomaterials for As removal were reviewed and 38 papers covering photocatalysts for NOM removal. These papers were organised by type of nanomaterial, and their important findings summarised. Although many authors have demonstrated effective solutions in the laboratory, the following areas still need to be addressed: the challenges posed by larger pilot and full scale continuously operated processes; the treatment of complex natural water matrices; which technologies will be required to economically separate nanoparticles from the treated water; whether the nanoparticles will be more economically and environmentally sustainable than other techniques available. Despite these significant gaps in the literature, the body of work carried out thus far, as summarised in this review paper, strongly suggests that full scale treatment solutions applying (magnetic) nanomaterials may prove highly effective in the future for both arsenic and NOM removal.

Dual-functional Z-scheme CdSe/Se/BiOBr photocatalyst: Generation of hydrogen peroxide and efficient degradation of ciprofloxacin

The major challenges of clean energy and environmental pollution have resulted in the development of photocatalysis technologies for energy conversion and the degradation of refractory pollutants. Herein, a novel CdSe/Se/BiOBr hydrangea-like photocatalyst was used to produce hydrogen peroxide (H2O2) and degrade ciprofloxacin (CIP). The Z-scheme heterojunction structure of the photocatalyst and the doping of selenium (Se) led to the efficient separation of electron-hole pairs and charge transfer. The optimized sample of 2 wt% CdSe/Se/BiOBr produced 142.15 mg·L−1 rate of H2O2, which was much higher than that produced by pure BiOBr (89.4 mg·L−1) or CdSe/Se (10.9 mg·L−1). Additionally, almost 100 % of CIP was degraded within 30 min, with a first order rate constant of nearly 5.35 times that of pure BiOBr and 81.44 times that of pure CdSe/Se. The excellent removal efficiency of CIP from natural water matrices confirmed that the composites are promising for the removal of contaminants from natural waterways. Based on trapping experiments, electron spin resonance spectra (ESR) spectroscopy, and density functional theory (DFT) calculations, the photocatalytic mechanisms of H2O2 and CIP degradation by the Z-scheme CdSe/Se/BiOBr composites were proposed. Overall, the dual-functional CdSe/Se/BiOBr composite could potentially be applied for photocatalytic production of H2O2 and treatment of organic pollutants in water.

BDD electrochemical oxidation of neonicotinoid pesticides in natural surface waters. Operational, kinetic and energetic aspects

Neonicotinoids pesticides were introduced to the market in the 1990s to control various pests. Its accumulation in the environment supposes a severe problem that can affect human health. This study investigates the electrochemical degradation of four common neonicotinoid pesticides; thiamethoxam (TMX), imidacloprid (ICP), acetamiprid (ACP) and thiacloprid (TCP), in different natural surface waters by a boron-doped diamond anode (BDD). The most influencing variable was the current density (j), and to a lesser extent, the supporting electrolyte concentration (Ce). In optimal conditions (j = 34.14 mA cm−2 and Ce = 10.00 mM, using Na2SO4 as electrolyte) pesticide removals for TMX, ICP, ACP and TCP were 97.2, 96.9, 87.8 and 98.2 %, respectively. The obtained results with different support electrolytes (Na2SO4, NaCl, NaNO3 and HK2PO4) suggest that sulphate electrolyte was the optimum for TMX, ICP and ACP. However, for TCP, a total removal was achieved in less than 10 min using NaCl. It was also verified that the initial pH of the solution did not significantly influence the process in the range 3–9. All these results were rationalized in this paper. Finally, to evaluate the matrix influence, some experiments were carried out in different natural surface water matrices (river, reservoir and two different WWTP effluents). The factors influencing the process were the conductivity of the solution and the organic matter content. It was noticeable that the specific energy consumption (SEC) reduced by approximately 15 % for river water and WWTP effluent. High mineralization rates were obtained for all water matrices, with TOC removals ranging between 60 and 80 %.

Reusing warm-paste waste as catalyst for peroxymonosulfate activation toward antibiotics degradation under high salinity condition: Performance and mechanism study

Resourcing solid waste as catalysts for activating peroxymonosulfate (PMS) used in high-salt organic wastewater treatment, to realize waste control, is meaningful, promising, and a win–win strategy for environmental remediation. Here, a magnetically recyclable hybrid originating from used warm paste (greater than92% yield) was developed using water washing to activate PMS for antibiotics degradation under hypersaline system. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) measurements indicated that the hybrid is a sheet structure with active Fe sites uniformly dispersed on the surface. The hybrid displayed an excellent PMS activation capacity; it is superior to those of classical Fe3O4 and Co3O4, which could degrade the tetracycline (TC). However, under a high-salt (0.2 mol/L Na2SO4) or mixed salts condition, the hybrid exhibited TC degradation performance. Moreover, a detailed investigation of the impact on of TC removal indicated that the preferable conditions were pH = 6, temperature = 25 °C, catalyst = 0.3 g/L and PMS = 0.3 g/L. Systematic experiments uncovered the hybrid exhibiting superb catalysis universality and adaptability in three refractory organics, 5 natural polluted water matrices, and coexisting-ions system, as well as five times, recycle processes. The surface chemical analysis combined with quenching experiment and electron paramagnetic resonance (EPR) test confirmed the PMS activation mechanism and the reactive radicals contributed in order of 1O2 > •OH > SO4•−. Considering its performance, stability and applicability, the warm paste hybrid would be good for PMS activation toward high-salt environment remediation. Thus inducing a novel direction for solid waste treatment and mitigated resource scarcity.

Degradation of 2,4-dinitrotoluene using ferrous activated persulfate: Kinetics, mechanisms, and effects of natural water matrices

The sulfate radicals (SO4•−)-based advanced oxidation process is an efficient way to degrade stubborn pollutants. However, the degradation products of 2,4-dinitrotoluene and the effects of different natural water matrices on 2,4-dinitrotoluene degradation by persulfate/Fe2+ are largely unknown. In this study, the degradation kinetics of 2,4-dinitrotoluene by persulfate/Fe2+ were investigated in different water matrices. The degradation of 2,4-dinitrotoluene can be divided into rapid-slow reaction stages, which was suitably described by the pseudo-first-order kinetics model (R2 >0.95). The concentrations of persulfate and Fe2+ had a significant effect on 2,4-dinitrotoluene degradation, and a molar ratio of persulfate/Fe2+ of < 5:1 is favorable for 2,4-dinitrotoluene degradation. Based on the intermediate products, degradation pathways of 2,4-dinitrotoluene, such as hydroxylation/oxidation and removal of the nitro group from the benzene ring, were proposed. The presence of HCO3−, CO32−, and NO3− inhibited the degradation of 2,4-dinitrotoluene by persulfate/Fe2+. In natural aquatic environments with low Cl− concentrations, the persulfate/Fe2+ oxidation process demonstrated superior efficiency in degrading 2,4-dinitrotoluene. The present results will provide vital information for successfully cleaning up 2,4-dinitrotoluene from the aquatic environment using SO4•−-based advanced oxidation process.

Degradation of trimethoprim by sulfate radical-based advanced oxidation processes: kinetics, mechanisms, and effects of natural water matrices.

In this study, we investigated the removal efficiency of a broad-spectrum antimicrobial agent trimethoprim (TMP) in a UV-activated persulfate system (UV/PS). The pseudo-first-order reaction kinetic model based on the steady-state hypothesis was used to explain TMP degradation behavior in UV-activated persulfate system. Due to the low quantum yield and molar absorptivity of TMP at 254 nm, the direct photolysis of TMP was slower. Since the free radicals generated by adding H2O2 or PS to the system can react with TMP, the degradation rate was significantly accelerated, and mathrm{S}{mathrm{O}}_4^{bullet -} played a dominant role in the UV/PS system. {k}_{mathrm{H}{mathrm{O}}^{bullet },mathrm{TMP}} and {k}_{{mathrm{SO}}_4^{bullet -},mathrm{TMP}} were determined by the pseudo-first-order reaction kinetic model to be 6.02×109 and 3.88×109 M−1s−1, respectively. The values were consistent with competitive kinetic measurements. The pseudo-first-order reaction kinetics model can predict and explain the effect of PS concentration, natural organic matter, and chloride ion on the TMP degradation in the UV/PS system. The observed pseudo first-order rate constants for TMP degradation (kobs) increased with the persulfate concentration, but it significantly decreased in the presence of NOM and chloride. mathrm{S}{mathrm{O}}_4^{2-} has no effect on the degradation of TMP, while mathrm{HC}{mathrm{O}}_{mathsf{3}}^{-} promotes the degradation and mathrm{N}{mathrm{O}}_3^{-} inhibits the degradation. The common transition metal ion (such as Cu2+, Zn2+, and Co2+) in industrial wastewater has a synergistic effect on the TMP degradation in the UV/PS system, but excessive metal ions will lead to a decrease of the degradation rate.

Carbon quantum dots-modified reduced ultrathin g-C3N4 with strong photoredox capacity for broad spectrum-driven PPCPs remediation in natural water matrices

• Carbon quantum dots-modified reduced ultrathin g-C 3 N 4 (RUCN/CQD) was prepared with facile method. • The RUCN/CQD possessed enhanced photoresponse and photoredox activities. • The RUCN/CQD exhibited superior photocatalytic activities in simulated natural conditions. Graphitic carbon nitride (g-C 3 N 4 ) has been extensively applied for the photocatalytic degradation of pharmaceuticals and personal care products (PPCPs); however, its catalytic performance remains restricted by a poor photoresponse and modest photoredox capacity toward the generation of free radicals. Herein, a novel carbon quantum dots-modified reduced ultrathin g-C 3 N 4 (RUCN/CQD) photocatalyst was successfully synthesized, with the capacity for direct •OH and O 2 •− yields and a broad-spectrum response. Upon broad-spectrum light irradiation, the RUCN/CQD demonstrated a 100% removal rate for diclofenac (DCF) within six min. This remarkable performance was attributed to a customized band structure with a thermodynamic driving potential for the generation of •OH, CQD with an effective electron transfer capacity for promotional formation of O 2 •− , and ultrathin porous structure with abundant reaction sites. Simultaneously, the up-converted fluorescent properties of the CQD endowed the photocatalyst with a broad-spectrum response. The RUCN/CQD system also exhibited superior photocatalytic activities under simulated natural conditions, which implied an immense potential for the remediation of PPCPs in ambient waterways.

Extraction of cerium(III) ions from dilute aqueous solutions by emulsion liquid membrane: effects of operating conditions, salts and natural water matrices

Extraction of cerium(III) ions from dilute aqueous solutions by emulsion liquid membrane: effects of operating conditions, salts and natural water matrices

Synergy between Iron and Selenide on FeSe2(111) Surface Driving Peroxymonosulfate Activation for Efficient Degradation of Pollutants.

In this study, iron selenide nanoparticles (FeSe2) were synthesized and applied in Fenton-like reactions for degradation of pollutants. It was found that FeSe2 exerts excellent catalytic reactivity toward different oxidants including peroxymonosulfate (PMS), peroxydisulfate, and H2O2, which can degrade a wide range of pollutants such as 2,4,4'-trichlorobiphenyl, bisphenol A, sulfamethoxazole, chlortetracycline, and perfluorooctanoic acid, with the degradation efficiency and TOC removal of pollutants reaching 55-95 and 20.3-50.9%, respectively. The mechanism of PMS activation by FeSe2 was elucidated, and the synergistic effect between Fe and Se for PMS activation was discovered to be the dominant catalytic mechanism, as evidenced by free-radical quenching, electron paramagnetic resonance, and density functional theory studies. Briefly, the Fe(II) site on the FeSe2 surface (111) accounted for PMS activation, while the reducing Se species on the surface not only acted as an electron donor contributing to Fe(II) regeneration but also produced Se vacancies further facilitating Fe(II) regeneration to improve the performance of PMS activation. In addition, FeSe2 exhibited high catalytic activity and stability for PMS activation with different pH, and can degrade PCBs efficiently in the presence of anions, natural organic matter water matrices or in complex soil eluents. This study presents the development and evaluation of FeSe2 as a novel and highly efficient activator that exhibits promise for practical applications for the degradation of pollutants in wastewater and soil wash eluent with Fenton-like reactions.