Natural Organic Matter Concentration Research Articles

The key role of hydrophobicity in the determination of pharmaceuticals by liquid chromatography–electrospray ionization-mass spectrometry under the interference of natural organic matter

The determination of trace-level pharmaceuticals in water is generally performed using liquid chromatography combined with mass spectrometry, which is susceptible to interference from non-target substances, such as natural organic matter (NOM). In this study, the interference of NOM on the determination of 20 typical pharmaceuticals using solid-phase extraction followed by ultra-performance liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (UPLC-ESI-tqMS) was investigated with a combined consideration of recoveries, matrix effects, and process efficiencies. The results showed that the recoveries of most pharmaceuticals were not significantly affected by NOM concentrations of 1-50mg/L. The matrix effects and process efficiencies decreased linearly with increasing logarithmic NOM concentrations, and the changes in matrix effects and process efficiencies both exhibited negative linear correlations with the pharmaceuticals' hydrophobicity (logKow). This result indicated that the determination of hydrophilic pharmaceuticals suffered from more severe NOM interference, as NOM entered the ESI source together with hydrophilic pharmaceuticals after UPLC separation and subsequently weakened the ionization efficiency of these pharmaceuticals. According to the correlations between logKow and the changes in matrix effects and process efficiencies, the pharmaceutical determination in positive/negative ESI modes with logKow ≤ 3.80/4.27 is considered to be significantly affected by NOM, accompanied by > 20% changes in matrix effects and process efficiencies.

Effect of particulate matters on inactivation of bacteriophage MS2 under irradiation above 320nm.

The inactivation of bacteriophage MS2 under irradiation above 320nm was investigated, focusing on different solution pH, ionic strength, and Suwannee River natural organic matter (SRNOM) concentrations when solutions contained organic or inorganic particle matters. Inorganic and organic particles were modeled using kaolinite (KAO) and Microcystis aeruginosa (MA), respectively. The results showed that the two types of particles influenced on MS2 inactivation under different conditions. The lower pH contributed to the greater MS2 aggregation within pH range of 3.0 to 8.0, leading to an increasing inactivation rate. The presence of KAO induced reactive oxygen species (ROS) under the action of irradiation above 320nm, which promoted the inactivation of MS2. By comparison, the [Formula: see text] produced by MA after irradiation promoted the inactivation at pH < 6, whereas when the pH is ≥ 6, the inactivation effect of MS2 was lower than that of particle-free solution because MS2 was no longer aggregated and MA has a shading effect. In the presence of Na+ or Ca2+ cation, irradiation above 320nm could not effectively inactivate the MS2 under particle-free solution. By comparison, KAO increased the inactivation efficiency as a photosensitizer. With the increase of Ca2+ concentration, MS2 was more easily adsorbed to MA than aggregation. Until Ca2+ concentration reached 20mM, the inactivation effect in MA solution was enhanced. In the presence of SRNOM, the inactivation effect increased with the increase of SRNOM concentration. When the SRNOM was 20mM, the inactivation increased in the particle-free solution due to the greater production of [Formula: see text]. Compared with the particle-free solution, the KAO and MA inactivation efficiency was lower.

Organic matter removal and antifouling performance of sulfonated polyaniline nanofiltration (S-PANI NF) membranes

Natural organic matter (NOM) removal from water prior to other treatment processes can improve treatment efficiency and final water quality. Here, NOM removal across five size fractions by newly developed sulfonated polyaniline nanofiltration (S-PANI NF) membranes was compared with a commercial membrane and conventional adsorption-coagulation-flocculation, optimized for NOM removal. Artificially prepared surface water and seawater containing 10 – 100 mg C L−1 NOM extract and a stabilized landfill leachate served as test solutions. S-PANI NF membranes showed best NOM separation performance for both surface and seawater followed by the commercial membrane and conventional treatment. For landfill leachate conventional treatment had the best performance followed by S-PANI NF membranes. S-PANI performed slightly better in removal of chemical oxygen demand (COD) (74%) compared to the commercial membrane (70%) and conventional treatment (70%). Both membranes performed consistent with increasing salinity and NOM concentration, while experiencing a modest carryover at higher salinity. During long-term fouling S-PANI exhibited slower growth in transmembrane pressure (TMP), less affinity towards organic matter and higher flux recovery compared to the commercial membrane, particularly at high NOM concentration. This is the first study to investigate S-PANI membranes for water treatment applications and under high-fouling conditions. Results indicate S-PANI NF membranes are promising for such applications. In addition, this study also provides an inter-process comparison for NOM removal over an extreme range of water matrix conditions.

The effects of pH, ionic strength, and natural organics on the transport properties of carbon nanotubes in saturated porous medium

Carbon Nanotubes (CNTs) are widely utilized, and their inadvertent release into the soil and ground water systems may have detrimental environmental implications. Therefore, it is critical to comprehend the effect of several environmental conditions on the fate and transport of CNTs in porous media. In previous studies, a narrow range of pH, ionic strength, and collector grain size have only been considered while evaluating the transport and retention of functionalized multiwalled carbon nanotubes (f-MWCNTs). None have highlighted the effect of environmentally relevant concentrations of natural organic matter and particle concentrations on the mobility of f-MWCNTs in porous medium. The current study aims to fill the knowledge gap by evaluating the fate and transport of f-MWCNTs at different, environmentally relevant physicochemical conditions of pH (5, 7, and 9), ionic strengths (10, 50, and 100 mM), humic acid as representative of natural organic matter (0.1, 1, and 10 mg/L) and particle concentrations (10, 25, and 50 mg/L) through saturated porous medium (quartz sand). It was noted that a wide range of pH and humic acid imparted an overall negative charge on the particles, enhancing their mobility (C/C0 > 0.8). However, transport of the f-MWCNTs was hindered in the presence of high ionic strength and particle concentrations (C/C0 < 0.1). The transport profile was mathematically simulated using a one-dimensional advection-dispersion equation (ADE) and colloidal filtration theory (CFT). Additionally, interaction energy profiles based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory were estimated to gain a better understanding of the mechanism of f-MWCNT deposition. In light of the potential environmental consequences, the impact of real-world water systems (tap, river, lake, and ground water) on the transport behaviour of f-MWCNTs was also investigated. The study considerably advances our understanding of the various physicochemical and environmental factors that can critically impact the transport of f-MWCNT in porous media, which could prove beneficial for environmental applications and risk management.

The effect of polyethylene microplastics on the disinfection of Escherichia coli by sodium hypochlorite

The effect of polyethylene microplastics (PE-MPs) on the disinfection of Escherichia coli (E. coli) by sodium hypochlorite was investigated in different pH value, ionic strength, and NOM concentration to illustrate the impact of MPs on the pathogenic bacteria disinfection efficiency in nature water environment. The results showed that PE-MPs tended to agglomerate rather than disperse due to their strong hydrophobicity in water. Within 30 s, about 1.5 log10 of E. coli was adsorbed on the surface of PE-MPs, forming subsequent protection for E. coli. Thus, the presence of PE-MPs reduced the inactivation rate of E. coli. As for the particle-free solutions, the higher solution pH, the presence of natural organic matter (NOM), and the higher concentrations of cations (monovalent Na+ and divalent Ca2+) were confirmed as the major influencing factors decreasing the E. coli disinfection efficiency. However, due to the adsorption and protection of PE-MPs on E. coli, the influences of complex chemistry factors on the inactivation of E. coli were reduced. The inactivation of E. coli in PE-MPs (20 NTU) solution was 1 log10 lower than that in particle-free solution under the same water quality conditions. Therefore, considering the complex water chemistry, the existence of MPs could be a potential challenge for disinfection efficiency in the water treatment plants.

Development of a low-cost method for quantifying microplastics in soils and compost using near-infrared spectroscopy

Near-infrared (NIR) spectroscopy is a promising candidate for low-cost, nondestructive, and high-throughput mass quantification of microplastics in environmental samples. Widespread application of the technique is currently hampered mainly by the low sensitivity of NIR spectroscopy compared to thermoanalytical approaches commonly used for this type of analysis. This study shows how the application of NIR spectroscopy for mass quantification of microplastics can be extended to smaller analyte levels by combining it with a simple and rapid microplastic enrichment protocol. For this purpose, the widely used flotation of microplastics in a NaCl solution, accelerated by centrifugation, was chosen which allowed to remove up to 99% of the matrix at recovery rates of 83%–104%. The spectroscopic measurements took place directly on the stainless-steel filters used to collect the extracted particles to reduce sample handling to a minimum. Partial least squares regression models were used to identify and quantify the extracted microplastics in the mass range of 1–10 mg. The simple and fast extraction procedure was systematically optimized to meet the requirements for the quantification of microplastics from common polyethylene-, polypropylene-, and polystyrene-based packaging materials with a particle size <1 mm found in compost or soils with high natural organic matter content (>10% determined by loss on ignition). Microplastics could be detected in model samples at a mass fraction of 1 mg g−1. The detectable microplastic mass fraction is about an order of magnitude lower compared to previous studies using NIR spectroscopy without additional enrichment. To emphasize the cost-effectiveness of the method, it was implemented using some of the cheapest and most compact NIR spectrometers available.

Multi-angle comparison of UV/chlorine, UV/monochloramine, and UV/chlorine dioxide processes for water treatment and reuse

Advanced oxidation processes (AOPs) have been increasingly studied and practiced for micropollutant abatement in drinking water treatment and potable water reuse. This study conducted the multi-angle comparison of the UV/chlorine, UV/monochloramine (UV/NH2Cl), and UV/chlorine dioxide (UV/ClO2) AOPs with respect to reactive species generation, micropollutant degradation, byproduct formation, and toxicity change. The concentrations of radicals (HO·, Cl·, and ClO·) generated in the three AOPs followed the order of UV/chlorine > UV/NH2Cl > UV/ClO2 at an oxidant dose of 70 μM, an irradiation wavelength of 254 nm, and a pH of 7.5. The concentration of ozone generated in the UV/ClO2 AOP was higher than that in the UV/chlorine AOP, while ozone was not generated in the UV/NH2Cl AOP. The effects of pH (pH 6.0, 7.5, and 9.0) and UV wavelength (254 nm, 285 nm, and 300 nm) on the three AOPs were evaluated and compared. Using the radical and ozone concentrations determined in this study, the pseudo-first-order degradation rate constants of 24 micropollutants by the three AOPs were predicted and compared. When the three AOPs were used to treat the water containing the same concentration of natural organic matter, the formation of total organic chlorine (TOCl) and the organic byproduct-associated toxicity followed the same order of UV/chlorine > UV/NH2Cl > UV/ClO2. On the contrary, the inorganic byproduct-associated toxicity followed the order of UV/ClO2 > UV/chlorine > UV/NH2Cl, due to the high concentrations of chlorite and chlorate formed in the UV/ClO2 AOP. Findings in this study offer fundamental information useful for the selection and operation of AOPs for micropollutant abatement in drinking water treatment and potable water reuse.

Photocatalytic degradation of a typical macrolide antibiotic roxithromycin using polypropylene fibre sheet supported N–TiO2/graphene oxide composite materials

ABSTRACT The post-treatment of recycling the fine photocatalyst nanoparticles restricts their application. In this study, a new photocatalytic material was synthesized by immobilizing the N-doped TiO2 and graphene oxide (GO) composite on polypropylene (PP) (N–TiO2/GO/PP) fibre sheet, and characterized based on X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Scanning Electron Microscope (SEM). The photocatalytic activity was evaluated using roxithromycin (ROX) as a typical antibiotic pollutant. XRD, Raman spectra and SEM images proved that N–TiO2/GO/PP fibre sheet was successfully synthesized. The photocatalytic degradation of 10 mg L−1 ROX can reach up to 90% and the degradation rate constant was 0.2299 h−1 in surface water with the application amount of TiO2/GO/PP fibre sheet of 24.6 cm × 2.7 cm and reaction time of 9 h under the irradiation of simulated sunlight. The application amount of TiO2/GO/PP fibre sheet, initial concentration of ROX and water matrix significantly affect the degradation of ROX. A low concentration of natural organic matter (NOM) slightly promoted the degradation of ROX, while a high concentration of NOM significantly inhibited the degradation of ROX. Alkaline condition (pH 8–9) is favourable for the photocatalytic degradation of ROX by TiO2/GO/PP fibre sheet. The photocatalytic reactivity of the TiO2/GO/PP fibre sheet showed no significant decrease after three runs. Two primary degradation products of ROX were identified and they showed lower ecotoxicity than ROX. The results demonstrate that the new synthesized TiO2/GO/PP fibre sheet shows promising application prospects in the treatment of antibiotics in wastewater and surface waters.

Influence of manganese oxide‐coated granular media on disinfection byproduct formation

AbstractThe objective of this study was to determine the influence of manganese oxide (MnOx) coated granular media on disinfection byproduct (DBP) formation for dissolved manganese (Mn(II)) and natural organic matter (NOM) concentrations typical in drinking water treatment (DWT). Instantaneous and 24‐h haloacetic acid and total trihalomethane concentrations of influent and effluent samples from two DWT plants, one using MnOx‐coated dual media (DM) filters and the other using second‐stage contactors for Mn(II) sorption by coarse MnOx‐coated ceramic media after DM filtration, were examined. Results showed that interaction with MnOx‐coated surfaces did not increase measured DBP concentrations. Observed increases in 24‐h DBP concentrations for the surface water plant were attributed to filter‐associated NOM, and not the MnOx coating. The findings of this study indicate that a second‐stage contactor – with MnOx‐coated media utilized for Mn(II) removal after a particle removal filter – does not increase DBP formation under typical treatment conditions.

Ozonation/adsorption hybrid treatment system for improved removal of natural organic matter and organic micropollutants from water – A mini review and future perspectives

Elevated concentrations of natural organic matter (NOM) and organic micropollutants (OMPs) can contaminate the quality of drinking water, and current water treatment technologies are not always successful in removing all their constituents. Ozonation and adsorption are two advanced processes with different removal mechanisms used to treat NOM and OMPs. Their treatment efficiency depends on the strength and kinetics of adsorption and ozonation (ozone molecule and OH radical (OH•) reaction) of the individual NOM constituents and OMPs. They are individually able to remove many of the NOM fractions and OMPs but not satisfactory in removing the vast array of their components which differ in their physico-chemical characteristics, for example molecular weight, charge, functional groups, aromaticity, and hydrophobicity/hydrophilicity. Significant progress has been made by integrating these processes (ozonation followed by activated carbon (AC) adsorption) but they need further improvement to efficiently target all NOM fractions and the various OMPs. Ozonation transforms the larger NOM molecules into smaller molecular sizes with lower aromaticity and hydrophobicity, subsequently resulting in reduced adsorption. The reduced adsorption of these molecules diminishes their competition against OMP adsorption resulting in increased OMP removal. Adsorption can remove unoxidized pollutants as well as the by-products of ozonation, and some of them are suspected to be human carcinogens. Of the commonly used adsorbents, anion exchange resin and AC, the former has higher affinity towards negatively charged humic fraction and OMPs. Conversely, the latter has higher affinity towards the hydrophobic constituents and smaller sized constituents which diffuse into AC pores and get adsorbed. Biofilm formed by long-term use of AC also contributes to enhanced removal of NOM and OMPs. This paper briefly reviews the currently available literature on removing NOM and OMPs by the ozonation/adsorption integrated process. It also suggests a new method for further increasing the efficiency of this process.

Accumulation of chiral pharmaceuticals (ofloxacin or levofloxacin) onto polyethylene microplastics from aqueous solutions

Drug chirality is attracting increasing attention because the enantiomers of the same chiral pharmaceutical usually exhibit different biological activities, metabolic pathways, and toxicities. The ubiquitous presence of microplastics (MPs) can enrich organic pollutants commonly found in the environment. However, knowledge about the enrichment of pharmaceutical enantiomers to MPs is relatively limited. We investigated the occurrence of enantioselectivity of ofloxacin (OFL) and levofloxacin (LEV) in the adsorption processes on polyethylene (PE) and the interactions influenced by environmental factors. The results showed that the adsorption efficiency of OFL was generally 3–5% (p < 0.05) higher than that of LEV, indicating the different affinities of the enantiomers to PE, but the adsorption process of OFL and LEV on PE was both well described by pseudo-first-order kinetics and liner isotherm models. The chirality of OFL and LEV was not affected by sizes of PE particles and solution salinity due to the identical physicochemical properties. An examination of pH effect indicated that OFL showed better acid-base adaptability than LEV. Moreover, the differences in enantiomeric enrichment between OFL and LEV on PE were promoted with increasing UV light exposure time and natural organic matter (NOM) concentrations. Using Fourier transform infrared spectroscopy (FTIR), we demonstrated that the constituents of the functional groups in chiral NOM were greatly related to the enantiomer stereoselectivity of OFL, subsequently affecting their adsorption in a chiral environment. The excitation-emission matrix (EEM) spectra confirmed the enantioselective behaviors of chiral pharmaceuticals under UV light due to the different optical activity and humic acid-like and fulvic acid-like molecular structure of the enantiomers. These findings imply that the enantioselectivity of drug enantiomers should be considered in presence of microplastics, leading to a more accurate environmental fate and risks assessments of chiral pharmaceuticals.

Environmental impacts of the widespread use of chlorine-based disinfectants during the COVID-19 pandemic.

Chlorinated disinfectants are widely used in hospitals, COVID-19 quarantine facilities, households, institutes, and public areas to combat the spread of the novel coronavirus as they are effective against viruses on various surfaces. Medical facilities have enhanced their routine disinfection of indoors, premises, and in-house sewage. Besides questioning the efficiency of these compounds in combating coronavirus, the impacts of these excessive disinfection efforts have not been discussed anywhere. The impacts of chlorine-based disinfectants on both environment and human health are reviewed in this paper. Chlorine in molecular and in compound forms is known to pose many health hazards. Hypochlorite addition to soil can increase chlorine/chloride concentration, which can be fatal to plant species if exposed. When chlorine compounds reach the sewer/drainage system and are exposed to aqueous media such as wastewater, many disinfection by-products (DBPs) can be formed depending on the concentrations of natural organic matter, inorganics, and anthropogenic pollutants present. Chlorination of hospital wastewater can also produce toxic drug-derived disinfection by-products. Many DBPs are carcinogenic to humans, and some of them are cytotoxic, genotoxic, and mutagenic. DBPs can be harmful to the flora and fauna of the receiving water body and may have adverse effects on microorganisms and plankton present in these ecosystems.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-021-18316-2.

Combination of Coagulation, Adsorption, and Ultrafiltration Processes for Organic Matter Removal from Peat Water

The high content of natural organic matter (NOM) is one of the challenging characteristics of peat water. It is also highly contaminated and contributes to some water-borne diseases. Before being used for potable purposes, peat water must undergo a series of treatments, particularly for NOM removal. This study investigated the effect of coagulation using aluminum sulfate coagulant and adsorption using powdered activated carbon (PAC) as a pretreatment of ultrafiltration (UF) for removal of NOM from actual peat water. After preparation and characterization of polysulfone (Psf)-based membrane, the system’s performance was evaluated using actual peat water, particularly on NOM removal and the UF performances. The coagulation and adsorption tests were done under variable dosings. Results show that pretreatment through coagulation–adsorption successfully removed most of the NOM. As such, the UF fouling propensity of the pretreated peat water was substantially lowered. The optimum aluminum sulfate dosing of 175 mg/L as the first pretreatment stage removed up to 75–78% NOM. Further treatment using the PAC-based adsorption process further increased 92–96% NOM removals at an optimum PAC dosing of 120 mg/L. The final UF-PSf treatment reached NOM removals of 95% with high filtration fluxes of up to 92.4 L/(m2.h). The combination of three treatment stages showed enhanced UF performance thanks to partial pre-removal of NOM that otherwise might cause severe membrane fouling.

Enhanced degradation of iohexol in water by CuFe2O4 activated peroxymonosulfate: Efficiency, mechanism and degradation pathway

Iohexol as an iodinated X-ray contrast agent is widely used, and it is the potential precursor for toxic iodinated disinfection by-products in the disinfection process. In this study, a series of CuFe2O4 catalysts were prepared by sol-gel method with different molar ratios of total metal cations to citric acid ([Men+]T/CA) and employed as heterogeneous catalysts to activate peroxymonosulfate (PMS) for the removal of iohexol. The catalysts were characterized by various technologies, and the effect of [Men+]T/CA molar ratio on the catalysts' properties was explored. The CuFe2O4 synthesized with [Men+]T/CA molar ratio of 1:1 showed the best catalytic activity to PMS, and 95.0% of 1.0 mg/L iohexol was removed within 15 min by using 50 mg/L CuFe2O4 and 20 mg/L PMS. The quenching experiment and electron spin resonance (ESR) spectra indicated the generation of SO4- and OH in the CuFe2O4/PMS system, and the quantity experiments revealed that the generation concentration of SO4- was ten times higher than that of OH. The generation mechanism of SO4- and ·OH were investigated by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) spectra. The effects of catalyst dosage, PMS and iohexol concentration on the removal of iohexol were studied, and various water matrix factors including solution pH, natural organic matter (NOM) concentration and inorganic ions were also considered. Based on the twelve intermediate products of iohexol detected by UPLC-QTOF/MS, the degradation pathway was proposed. The high catalytic activity and reusability of CuFe2O4 indicated that CuFe2O4 activating PMS is an effective and sustainable way for the treatment of iohexol.

Desorption of micropollutant from superfine and normal powdered activated carbon in submerged-membrane system due to influent concentration change in the presence of natural organic matter: Experiments and two-component branched-pore kinetic model

Submerged-membrane hybrid systems (SMHSs) that combine membrane filtration with powdered activated carbon (PAC) take advantage of PAC's ability to adsorb and remove contaminants dissolved in water. However, the risk of contaminant desorption due to temporal changes in the influent concentration of the contaminant has not been thoroughly explored. In this study, we used a SMHS with conventionally-sized PAC or superfine PAC (SPAC) to remove 2-methylisoborneol (MIB), a representative micropollutant, from water containing natural organic matter (NOM), with the goal of elucidating adsorption–desorption phenomena in the SMHS. We found that 20–40% of the MIB that adsorbed on PAC and SPAC while the influent was contaminated with MIB (6 h, contamination period) desorbed to the liquid phase within 6 h from the time that the MIB-containing influent was replaced by MIB-free influent (no-contamination period). The percentage of desorption during the no-contamination period increased with increasing MIB breakthrough concentration during the contamination period. These findings indicate that the PAC/SPAC in the SMHS should be replaced while the breakthrough concentration is low, not only to keep a high removal rate but also to decrease the desorption risk. SPAC is fast in removal by adsorption, but it is also fast in release by desorption. SPAC (median diameter: 0.94 µm) showed almost the same adsorption-desorption kinetics as PAC (12.1 µm) of a double dose. A two-component branched-pore diffusion model combined with an IAST (ideal adsorbed solution theory)–Freundlich isotherm was used to describe and analyze the adsorption–desorption of MIB. The diffusivity of MIB molecules in the pores of the activated carbon particles decreased markedly in a short period of time. This decrease, which was attributed to fouling of the activated carbon in the SMHS by coagulant-treated water containing NOM, not only reduced the rate of MIB removal during the contamination period but also hindered the rate of MIB desorption during the no-contamination period and thus prevented the effluent MIB concentration from becoming high. On the other hand, coagulation did not change the concentration of NOM that competes with MIB for adsorption sites.

MgO-supported CuO with encapsulated structure for enhanced peroxymonosulfate activation to remove thiamphenicol

Copper-base catalysts with high load content of CuO were commonly utilized to activate peroxymonosulfate (PMS) for removal of contaminants but limited catalytic efficiency and increased risk of copper ion leaching restricted their use. In this paper, Cu-Mg mixed metal oxides with highly dispersed minute quantities of CuO were successfully prepared by one-pot synthesis for efficiently activating PMS to remove thiamphenicol (TAP), which was economical and environmentally friendly. The catalytic activities of catalysts with different molar ratios of Cu and Mg for PMS and their characteristics were evaluated, illustrating the optimal molar ratio of Cu and Mg (1:15, named CuMg-MMO) in the catalyst. For the CuMg-MMO catalyst, MgO widely dispersed and wrapped CuO nanoparticles, minimized the copper ion leaching and promoted the generation of Cu-OH complex and non-radical species. In the CuMg-MMO/PMS system, the influence factors for TAP degradation were analyzed, including different systems, catalyst dosages, PMS concentrations, temperatures, initial pH values, TAP concentrations, anions (NO3-, HCO3-, Cl-, HPO42- and H2PO4-) and natural organic matter (NOM) concentrations. Under the optimal conditions (i.e., [catalyst]: 75 mg/L, [PMS]: 0.3 mM, temperature: 30 °C and initial pH: 6.5), TAP removal efficiency obtained by this system was 99.9%. SO4·-, ·O2- and 1O2 played more important roles than HO· in TAP degradation. Four successive repeated experiments indicated that CuMg-MMO possessed good reusability and stability. PMS decomposition, mineralization of TAP, the activation mechanism of PMS and possible degradation pathways of TAP were analyzed.

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.

Sensitive Electrochemical Detection of Microcystin-LR in Water Samples Via Target-Induced Displacement of Aptamer Associated [Ru(NH3)6]3.

In this study, we demonstrate the successful development of an electrochemical aptamer-based sensor for point-of-use detection and quantification of the highly potent microcystin-LR (MC-LR) in water. The sensor uses hexaammineruthenium(III) chloride ([Ru(NH3)6]3+) as redox mediator, because of the ability of the positively charged (3+) molecule to associate with the phosphate backbone of the nucleic acids. We quantitatively measure the target-induced displacement of aptamer associated, or surface confined, [Ru(NH3)6]3+ in the presence of MC-LR. Upon the addition of MC-LR in the water, surface-confined [Ru(NH3)6]3+ dissociates, resulting in less faradaic current from the reduction of [Ru(NH3)6]3+ to [Ru(NH3)6]2+ Sensing surfaces of highly packed immobilized aptamers were capable of recording decreasing square wave voltammetry (SWV) signals after the addition of MC-LR in buffer. As a result, SWV recorded substantial signal suppression within 15 min of target incubation. The sensor showed a calculated limit of detection (LOD) of 9.2 pM in buffer. The effects of interferents were minimal, except when high concentrations of natural organic matter (NOM) were present. Also, the sensor performed well in drinking water samples. These results indicate a sensor with potential for fast and specific quantitative determination of MC-LR in drinking water samples. A common challenge when developing electrochemical, aptamer-based sensors is the need to optimize the nucleic acid aptamer in order to achieve sensitive signaling. This is particularly important when an aptamer experiences only a small or localized conformational change that provides only a limited electrochemical signal change. This study suggests a strategy to overcome that challenge through the use of a nucleic acid-associated redox label.

Guidelines for surfactant selection to treat petroleum hydrocarbon-contaminated soils

The present study determined the most effective surfactants to remediate gasoline and diesel-contaminated soil integrating information from soil texture and soil organic matter. Different ranges for aliphatic and aromatic hydrocarbons (> C6–C8, > C8–C10, > C10–C12, > C12–C16, > C16–C21, and > C21–C35) in gasoline and diesel fuel were analyzed. This type of analysis has been investigated infrequently. Three types of soils (silty clay, silt loam, and loamy sand) and four surfactants (non-ionic: Brij 35 and Tween 80; anionic: SDBS and SDS) were used. The results indicated that the largest hydrocarbon desorption was 56% for silty clay soil (SDS), 59% for silt loam soil (SDBS), and 69% for loamy sand soil (SDS). Soils with large amounts of small particles showed the worst desorption efficiencies. Anionic surfactants removed more hydrocarbons than non-ionic surfactants. It was notable that preferential desorption on different hydrocarbon ranges was observed since aliphatic hydrocarbons and large ranges were the most recalcitrant compounds of gasoline and diesel fuel components. Unlike soil texture, natural organic matter concentration caused minor changes in the hydrocarbon removal rates. Based on these results, this study might be useful as a tool to select the most cost-effective surfactant knowing the soil texture and the size and chemical structure of the hydrocarbons present in a contaminated site.

Visible light-driven g-C3N4 peroxymonosulfate activation process for carbamazepine degradation: Activation mechanism and matrix effects

In this study, g-C3N4 with a high portion of tri-s-triazine groups was synthesized to activate peroxymonosulfate (PMS) under visible light irradiation, termed as Vis/g-C3N4/PMS process, to degrade one frequently detected recalcitrant micropollutant carbamazepine (CBZ). The Vis/g-C3N4/PMS process increased pseudo first-order degradation rate constant of CBZ by 2 times compared with that in the absence of PMS. The enhanced CBZ degradation was because of the production of HO and SO4– from the PMS activation, but not the enhanced charge separation of g-C3N4 due to the presence of PMS. The Vis/g-C3N4/PMS process is insensitive to dissolved oxygen, chloride and bicarbonate concentrations, effective over a wide pH range from 6.0 to 10.0, and less affected by high concentrations of natural organic matter compared with the UV/chlorine and UV/TiO2 processes. In addition, photocatalytic activity of g-C3N4 remains stable over 5-cycle of reuse. These features make the process practically relevant and implementable in degrading micropollutants in drinking water, treated wastewater, surface water, groundwater, etc., using more efficient visible light LEDs or even sunlight.