High Humic Acid Content Research Articles

Novel VUV/g-C3N4 system with high adaptability to varied environmental conditions and outstanding degradation capacity for chlorophenols

Given the limitations of conventional vacuum ultraviolet (VUV) systems, a novel vacuum ultraviolet/graphite carbon nitride (VUV/g-C3N4) system with high adaptability to varying environmental conditions was developed. Compared with conventional VUV and UV/g-C3N4 systems, the VUV/g-C3N4 system demonstrates a much higher ability for the efficient degradation of chlorophenols (CPs). In particular, the VUV/g-C3N4 system exhibits outstanding performance even at low pH and high concentrations of humic acid and SO42-. Alkaline conditions and the presence of HCO3- can further promote CP removal. In addition, the feasibility of the VUV/g-C3N4 system was verified by its stable operation in both river water and tap water. Unlike conventional photochemical systems relying on •OH, the dominant reactive species for CP degradation by the VUV/g-C3N4 system was identified to be •O2-. This study conclusively provided a novel system for the efficient photocatalytic treatment of pollutants.

Biochar-facilitated remediation of nanoplastic contaminated water: Effect of pyrolysis temperature induced surface modifications

“Nanoplastics- the emerging contaminants” and “agricultural waste to resource conversion” both are currently at the scientific frontiers and require solutions. This study aims to utilize sugarcane bagasse-derived biochar for the removal of nanoplastics (NPs) from aqueous environment. Three types of biochar were synthesized at three different pyrolysis temperatures, i.e. 350, 550, and 750 ℃ and evaluated for their potential in removing NPs. Effect of various environmental parameters, i.e., competing ions, pH, humic acid and complex aqueous matrices on NPs sorption was also studied. Results showed that attributing to decreased carbonyl functional groups, increased surface area and pore abundance, biochar prepared at 750 ℃ showed drastically higher NPs removal (>99%), while BC-550 and BC-350 showed comparatively lower NPs sorption (<39% and <24%, respectively). Further sorption studies confirmed instantaneous NPs removal with equilibrium attainment within 5 min of interaction and efficient NPs sorption capacity, i.e. 44.9 mg/g for biochar prepared at 750 ℃. Non-linear-kinetic modeling suggested pseudo 1st order removal kinetics while isotherm and thermodynamic modeling confirmed- monolayer instantaneous sorption of NPs sorption. Enhanced electrostatic repulsion resulted in decrease in NPs sorption at alkaline conditions, whereas steric hindrance caused limited removal (<25%) at higher humic acid concentrations.

Photochemical transformation of decachlorobiphenyl (PCB-209) on the surface of microplastics in aqueous solution

• Photochemical transformation of PCB-209 on PS microplastics in water was studied. • ROS attacked PCB-209 and PS to form chlorine-related radicals and polymer radicals. • Direct photolysis, photooxidation and radical reactions were main reactions. • Products from interactions of PS with PCB-209 were also detected. • DFT calculations were used to interpret reactions of PS with OH. The accumulation of persistent organic pollutants (POPs) and microplastics in the water environment has attracted widespread attention. Given the easy adsorption of PCB-209 by microplastics, this work aimed at examining the photochemical transformation behaviors of PCB-209 on the surface of polystyrene (PS) under simulated solar irradiation. The slowest degradation was observed at pH 7.0, with a rate constant of 0.0158(±0.0004) h −1 . The presence of NO 3 − , NH 4 + and high concentrations of humic acid would inhibit the removal of PCB-209, due to the decreased amount of available free radicals. The direct photolysis of PCB-209 resulted in the formation of lower chlorinated PCBs, while the irradiation of PS could produce reactive oxygen species (ROS) and various polymer radicals. Hydroxyl radicals, as the major ROS, would attack PCB-209 to form hydroxyl substitution products, with the release of chlorine and pentachlorobenzene radicals. Polymer radicals would undergo oxidation or scission to generate olefin type products and styrene/benzene-containing products, or react with chlorine/pentachlorobenzene radicals to form (poly)chlorinated PS products. Thus, the respective transformation products of PCB-209 and PS, as well as products resulting from the interactions of the polymer with the compound were detected. Toxicity predictions by ECOSAR revealed that some intermediate products are toxic to aquatic organisms. This study provides some new insights on the environmental fate of PCBs and the photochemical roles of microplastics in sunlit surface waters.

Enhanced diclofenac elimination in Fe(II)/peracetic acid process by promoting Fe(III)/Fe(II) cycle with ABTS as electron shuttle

Fe(II)/peracetic acid (Fe(II)/PAA) process exhibits a great potential in abatement of micropollutants because of the fast reaction between Fe(II) and PAA. Similar to Fenton system, the slow reduction from Fe(III) to Fe(II) leads to the high dosage of Fe(II) in Fe(II)/PAA process. This study introduced 2,2′-azino-bis(3-ethylbenz- -othiazoline-6-sulfonate) (ABTS) as electron shuttle to improve the oxidation capacity of Fe(II)/PAA process by accelerating the redox cycle of Fe(III)/Fe(II). ABTS/Fe(II)/PAA process possessed high elimination efficiency of diclofenac in acidic conditions. Alcohols quenching experiments confirmed that ABTS•+ was the primary reactive species responsible for diclofenac elimination, although FeIVO2+ and carbon-centered radicals (R-O•) also existed in ABTS/Fe(II)/PAA process. ABTS•+ was generated via various pathways, including the reactions of ABTS with Fe(III), FeIVO2+ and R-O•. ABTS was not an ideal electron shuttle because R-O• could decompose partial ABTS•+ to sulfoxides and sulfones. Two possible degradation pathways of diclofenac were proposed based on the detected transformation products. ABTS/Fe(II)/PAA process was highly-efficient for diclofenac elimination in underground water and reservoir water, while high concentration of humic acid had inhibition effect on diclofenac degradation. The present study provides a promising way to alleviate the intrinsic drawbacks of Fe(II)/PAA process and might advance its potential application in water treatment.

Determination of phenols in natural and waste waters by capillary electrophoresis after preconcentration on magnetic nanoparticles coated with aminated hypercrosslinked polystyrene.

An efficient sorbent for magnetic solid-phase extraction was developed from Fe3 O4 nanoparticles covered with aminated hypercrosslinked polystyrene. The sorbent has a saturation magnetization of 47 emu/g and a surface area of 509mg/g and was tested for the extraction of 11 phenols from aqueous media. The optimum conditions were as follows: pH 3; adsorbent mass, 20.0mg; adsorption time, 30min; eluent (acetone) volume, 0.5mL; and desorption time, 5min. The enrichment factor after desorption reached 1595-1716 and the maximum adsorption capacity was 501-909mg/g. Capillary electrophoresis was applied successively to separate 11 phenols after solid-phase extraction. The best separation was achieved using a fused silica capillary and borate buffer (pH 10.7) as a supporting electrolyte. After optimization, the linearity range was from 0.2 to 950 μg/L, and the limits of detection were 0.05-0.2 μg/L. The relative standard deviation varied from 6.1 to 8.7% (C=1 μg/L) and from 2.9 to 3.5% (C=500 μg/L). The determination of phenols is complicated in eutrophic water and spring water with a high content of humic and fulvic acids.

Arsenopyrite weathering in acidic water: Humic acid affection and arsenic transformation

Arsenopyrite is a common metal sulfide mineral and weathers readily in the open environment, releases As, and pollutes the surrounding environment. Humic acid (HA) is ubiquitous in soils, sediments and waters, and contains various functional groups and complex with arsenic, iron and other metal ions that affect the weathering behavior of arsenopyrite. Because As, iron, and HA are redox-active compounds, electrochemical techniques, including polarization curves, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), were used to fundamentally investigate the weathering process and mechanism of arsenopyrite over a wide range of environmental relevant conditions. Polarization curves showed higher HA concentrations (0-1000 mg•L−1), higher temperatures (5-35°C) or acidities (pH 1.0-7.0) promoted arsenopyrite weathering; there was a linear relationship between the corrosion current density (icorr), temperature (T) and acidity (pH): icorr = -3691.2/T + 13.942 and icorr = -0.2445pH + 2.2125, respectively. Arsenopyrite weathering readily occurred in the presence of HA as confirmed by its activation energy of 24.1 kJ•mol−1, and EIS measurements confirmed that the kinetics were controlled by surface reaction as confirmed by decreased double layer resistance. CV and surface characterization (FTIR and XPS) showed that arsenopyrite initially oxidized to S0, As(III) and Fe2+, then S0 and Fe2+ were ultimately converted into SO42− and Fe3+, while As(III) oxidized to As(V). Furthermore, the carboxyl (–COOH) and phenolic (–OH) of HA could bind with As(III)/(V) and Fe3+ via a ligand exchange mechanism forming As(III)/(V)-HA and As(III)/(V)-Fe-HA complexes that hinders the formation of FeAsO4 and decreases the bioavailability of As. Findings gained from this study are valuable for the understanding of the fate and transport of As in acidic conditions, and have powerful implications for the remediation and management of As-bearing sites affected by mining activities.

Linker-Free Magnetite-Decorated Gold Nanoparticles (Fe3O4-Au): Synthesis, Characterization, and Application for Electrochemical Detection of Arsenic (III).

Linker-free magnetite nanoparticles (Fe3O4NPs)-decorated gold nanoparticles (AuNPs) were grown using a new protocol that can be used as a new platform for synthesis of other intact metal–metal oxide nanocomposites without the need for linkers. This minimizes the distance between the metal and metal oxide nanoparticles and ensures the optimum combined effects between the two material interfaces. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the successful synthesis of the Fe3O4-Au nanocomposite, without any change in the magnetite phase. Characterization, using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, revealed the composite to consist of AuNPs of 70 ± 10 nm diameter decorated with tiny 10 ± 3 nm diameter Fe3O4NPs in Au:Fe mass ratio of 5:1. The prepared Fe3O4-Au nanocomposite was embedded in ionic liquid (IL) and applied for the modification of glassy carbon electrode (GCE) for the electrochemical detection of As(III) in water. By combining the excellent catalytic properties of the AuNPs with the high adsorption capacity of the tiny Fe3O4NPs towards As(III), as well as the good conductivity of IL, the Fe3O4-Au-IL nanocomposite showed excellent performance in the square wave anodic stripping voltammetry detection of As(III). Under the optimized conditions, a linear range of 1 to 100 μg/L was achieved with a detection limit of 0.22 μg/L (S/N = 3), and no interference from 100-fold higher concentrations of a wide variety of cations and anions found in water. A very low residual standard deviation of 1.16% confirmed the high precision/reproducibility of As(III) analysis and the reliability of the Fe3O4-Au-IL sensing interface. Finally, this proposed sensing interface was successfully applied to analyzing synthetic river and wastewater samples with a 95–101% recovery, demonstrating excellent accuracy, even in complex synthetic river and wastewater samples containing high concentrations of humic acid without any sample pretreatments.

Heteroaggregation of humic acid with montmorillonite in divalent electrolytes: effects of humic acid content and ionic concentration

Clay-humic substance complexes play a major role in controlling the mobility of elements and colloids in natural soils. The purpose of the present study is to explore the different reaction mechanisms induced by cations on the humic acid (HA) and montmorillonite (Mt) heteroaggregation and to analyze the binding mechanism of HA-Mt. HA is extracted from soil and colloidal Mt are prepared as K+-saturated. The aggregation kinetics of HA-Mt composite nanoparticles in Ca(NO3)2, Mg(NO3)2, and Cu(NO3)2 solutions were detected by dynamic light scattering. Furthermore, FT-IR spectroscopy was used to characterize the reactive sites involved in interaction with the metal ions. The results revealed that the order of reaction of these three metal cations with the HA-Mt composite was Cu2+ > Ca2+ > Mg2+, as evident from the total average aggregation rate, critical coagulation concentration, and activation energy. The heteroaggregation process was sensitive to the 1% mass percentage of HA; however, more HA (4% mass percentage) did not significantly affect this process compared with 1% HA. Higher cation concentration and higher HA content (10% mass percentage) were two necessary conditions for promoting HA-Mt heteroaggregation. The vibration peak intensities of the carboxyl group C-O bonds and hydroxyl group O-H bonds of HA were affected by the formation of coordinate bonds with different metal ions. Metal cations were preferentially complexed by the carboxyl groups of HA, and due to its polarization-induced and electric field–enhanced oxidizing properties, Cu2+ has the strongest aggregation ability for HA-Mt, followed by Ca2+ and Mg2+. The HA-Mt heteroaggregation is partially reversible by adjusting electrostatic repulsion. The results of this study improve our understanding of the roles of cations and HA in clay-humic substance interactions.

Effects of different types of humic acid isolated from coal on soil NH3 volatilization and CO2 emissions

Humic acid can improve soil nutrients and promote plant growth. Weathered coal and lignite can be used as agricultural resources due to high humic acid content, but their impact on soil NH3 volatilization and CO2 emissions are yet to be determined. In this study, a field experiment was carried out to compare the effects of four types of humic acid isolated from coal (pulverized weathered coal (HC), pulverized lignite (HL), alkalized weathered coal (AC) and alkalized lignite (AL)) on NH3 volatilization, CO2 emissions, pH, the C/N ratio and enzyme activities in soil cultivated with maize. The effect of biotechnology humic acids (BHA) was also examined for comparison. HL, AC, AL and BHA all increased cumulative NH3 losses by 147.7, 278.5, 113.9, and 355.3%, respectively, compared with the control (chemical fertilizer only), and notably, BHA caused an increase of 90.71% compared with the humic acids isolated from coal. A significant increase in cumulative CO2 losses was observed only under AL treatment, by 14.44–24.90% compared with all other treatments. Soil urease activity was positively correlated with cumulative NH3 losses (P < 0.001), while the soil C/N ratio (P < 0.001) and soil sucrase activity (P < 0.05) were positively correlated with cumulative CO2 losses. Since humic acid from pulverized weathered coal caused no increase in NH3 volatilization or CO2 emissions, it is therefore thought to be the most suitable humic acid for field application.

Перспективи використання торфів для вилучення гуматів (Львівська область)

The paper briefly considers the problems of the Ukraine’s peat industry and identifies the reasons for its decline, including the low quality of peat as an energy source. We assume that the use of peat for briquetting will be stopped in the near future due to economic and political factors. On the other hand, peat can be a source of chemicals and their mixtures that have found application in agriculture and industry. It is known that the addition of sodium humates to the drilling mud improves its rheological properties and makes them environmentally safe, especially when passing through aquifers. We set a goal to determine the geological, technological and geochemical characteristics of peat in the Lviv Region, to establish its suitability for the humic acids extraction and to identify promising deposits for future processing. The study of the peats microelement composition of the Radekhiv district (Lviv Region) showed that the studied peats are not contaminated with heavy metals, as evidenced by the values of pollution indices. It is shown that the content of chemical elements in peats of Lviv Region is less than clarke in the lithosphere, soils and terrestrial plants. There is a tendency to scatter chalcophilic and most siderophilic elements, to a lesser extent lithophilic. Determining the yield of total and free humic acids testified to the possibility of using peat in the Lviv Region to extract humates. The studied samples were characterized by a high content of humic acids in terms of dry weight. Preliminary assessment of deposits suitability for peat extraction was performed according to the following parameters: field reserves, degree of decomposition, humus content and ash content. After constructing maps of these geochemical characteristic’s distribution, we have identified several of the most promising deposits in the Lviv Region: in the Kamyanka-Buzka district – Didylivske and Yarychivske deposits; in the Mykolayiv district – Verbizke, Saikivske, Demnyanske and Trostyanetske.

Influence Factors on Photochemical Production of Methyl Iodide in Seawater

Methyl iodide (CH3I) is an important trace greenhouse gas in the atmosphere and an ozone-depleting substance. The influence of different environmental factors, such as the duration of illumination; the strength of illumination; the concentrations of humic acid, ferric ion (Fe3+), and iodide ion (I−); and pH, on the photochemical production of CH3I in artificial seawater (ASW) were tested by simulated solar irradiation. In addition, Yangtze River Estuary waters from inshore to offshore were used to explore the relationship between the photochemical production of CH3I and different sources of dissolved organic matter (DOM) in natural sea-water (NSW). The results revealed that higher concentrations of humic acid and I−, as well as higher strengths of illumination and longer illumination durations, promoted the photochemical formation of CH3I in ASW. The addition of Fe3+ accelerated the photochemical production of CH3I, but high concentrations of Fe3+ inhibited the formation of CH3I. Experiments on NSW obtained from the Yangtze River estuary spiked when concentrations of DOM were high, confirming that DOM plays an important role in facilitating the photochemical production of CH3I within the Yangtze River Estuary. The photochemical production of CH3I in the seawater was significantly higher under light conditions relative to dark conditions, indicating that illumination accelerated the production of CH3I.

Effects of humic acid on enhanced removal of lead ions by polystyrene-supported nano-Fe (0) nanocomposite

Polymer-supported nanozero-valent iron composites (D001-nZVI) were fabricated for the removal of lead ions from aqueous solutions by embedding nZVI into the porous polystyrene anion exchanger D001. Humic acid (HA) was selected as a model species because of its ubiquitous existence to gain insight into the influencing factors in the actual application process. The iron contents of the composites were approximately 11.2%, and the smallest ZVI particle size was ~ 5 nm. The experimental results showed that the effect of HA on the reduction of lead ions by D001-nZVI was a concentration-dependent process. At low HA concentrations, the surface-competitive adsorption of HA and Pb2+ dominated; therefore, the removal efficiency of Pb2+ by D001-nZVI decreased from 97.5 to 90.2% with an increasing HA concentration. When the HA concentration increased to 30 mg/L or more, the lead ions removal remained constant with the following possible cooperation mechanism: the competitive adsorption of HA and Pb2+ on the nZVI surface and the well-dispersed particles were caused by electrostatic interactions between the HA coating and the nZVI surface. In addition, the adsorption complexation between HA and Pb2+ also had a positive effect on the removal of Pb2+ at higher concentrations of HA.

Facet-controlled activation of persulfate by magnetite nanoparticles for the degradation of tetracycline

Three kinds of magnetite nanoparticles (MNPs) with different exposed crystal facets were synthesized by hydrothermal methods to investigate the effects of exposed facets on the catalytic performance. Under the heterogeneous activation of persulfate (PS), MNPs exposed with {111} facet exhibited better catalytic performance than that exposed with {110} or {100} facet in the degradation of tetracycline, and catalytic performance followed the order of MNPs{111} > MNPs{100} > MNPs{110}. The degradation efficiency of PS/MNPs{111} system reached 74.38% in 4 h, which was much higher than PS/MNPs{110} (19.29%) or PS/MNPs{100} (33.79%) system. Hydroxide, physically adsorbed H2O on the MNPs surface and transformations of Fe(II)/Fe(III) were the main factors to determine the high catalytic performance of MNPs{111} for PS, as illustrated by the X-ray photoelectron spectroscopy (XPS) analysis. The corresponding catalytic oxidation mechanism has been proposed on the basis of attenuated total reflection flourier transformed infrared spectroscopy (ATR-FTIR), electron paramagnetic resonance (EPR) spectroscopy and quenching tests. SO4− and OH were the main radicals in catalytic degradation of tetracycline. Density functional theory (DFT) analysis suggested that the difference of {110}, {111} and {100} facets of magnetite determine the electron density and the density of states on the surface of catalysts. In addition, relatively low concentration of humic acid promoted the removal of tetracycline, and higher concentration of humic acid inhibited the tetracycline removal.

Microplastics generated under simulated fire scenarios: Characteristics, antimony leaching, and toxicity.

Intentional or incidental thermal changes inevitably occur during the lifecycle of plastics. High temperatures accelerate the aging of plastics and promote their fragmentation to microplastics (MPs). However, there is little information available on the release of MPs after fires. In this study, an atomic force microscope combined with nanoscale infrared analysis was used to demonstrate the physicochemical properties of polypropylene (PP) plastics under simulated fire scenarios. Results showed that the chemical composition and relative stiffness of heat-treated plastic surfaces changed, significantly enhancing the generation of MPs under external forces; over (2.1±0.2)×105 items/kg abundance of MPs released from PP which were burned at 250°C in air and trampled by a person. The leaching of antimony (Sb) from MPs in different solutions first increased and then decreased with increasing temperature, reaching a maximum at 250°C. Higher concentrations of humic acid (10 vs 1mg/L) caused a greater release of Sb. Furthermore, the tap water leachates of PP burned at 250°C had the greatest effect on the growth and photosynthetic activity of Microcystis aeruginosa. Our results suggest fires as a potential source of MPs and calls for increased focus on burning plastics in future research.

Subcritical water extraction of organic acids from chicken manure.

Chicken manure waste has a wide range of organic substances and mineral elements. This enriched source has stimulated great scientific interest in finding cleaner and more environmentally benign nutrient recovery options. This study aimed to determine an effective and eco-friendly method (i.e. subcritical water extraction) for processing fresh poultry manure. The high content of total organic carbon, including humic acids carbon and fulvic acids carbon, in extract was found to release under subcritical conditions. The organic compounds obtained by extraction with subcritical water correspond to humic acid in composition because of the presence in the sample of all the functional groups: polymer bonded by molecular hydrogen bond (3400 cm-1 ), the presence of CH2 and CH3 groups (2870 cm-1 ), the presence of carboxyl groups (1720 cm-1 ) and quinones (1640-1680 cm-1 ). The solid phase left over was characterized by a high content of organic carbon, phosphorus, potassium, and microelements. The maximum extraction of humic acid and fulvic acid carbon was found between 210 and 250 °C at a pressure of 50-60 atm, and the content was a maximum of 3647.2 × 10-6 g kg-1 at an extraction temperature of 250 °C. Given the high content of humic acid found in the extracted medium, the proposed subcritical extraction opens up new opportunities for nutrients recovery in the poultry industry. © 2020 Society of Chemical Industry.

Synthesis of alkyl-functionalized magnetic for fluoroquinolones removal: Adsorption performance and mechanism studies in single and binary systems

The functionalized mesoporous silica (FMS) and core-shell magnetic functionalized mesoporous silica (MMS) were synthesized on the basis of unfunctionalized mesoporous silica (UMS) via alkyl modification and one-pot reaction. Its adsorption properties to enrofloxacin (ENR), pefloxacin (PEF) and ciprofloxacin (CIP) were systematically investigated in single and binary systems. The results indicated the adsorption performance of MMS is five times higher than UMS. Batch adsorption experiments demonstrated the MMS had a higher adsorption capacity and adsorption efficiency for FQs, with the maximum adsorption capacities of 201.52 mg g-1 for CIP, 275.46 mg g-1 for PEF and 286.35 mg g-1 for ENR. Meanwhile, over 80% and 90% removals were achieved within 5 min and 10 min. Experiment results also presented that: MMS was able to reach the maximum adsorption capacity around pH 7.0 and maintain high adsorption capacity at a high concentration of humic acid. Besides, MMS showed the selective adsorption to three FQs in the binary adsorption experiments. The reusability experiment suggested the MMS possess excellent stability. H-bonding, electrostatic interaction and hydrophobic interaction were the main driving force between three FQs and MMS. Moreover, the adsorbent can be readily separated from water solution by an external magnet. These obtained results could be used for adsorbent design in considering of the properties of the adsorbates and the reuse of adsorbents.

Aggregation behavior of zinc oxide nanoparticles and their biotoxicity to Daphnia magna: Influence of humic acid and sodium alginate

The widespread applications of zinc oxide nanoparticles (ZnO NPs) have raised increasing concerns due to their adverse environmental effects. The ubiquitous natural organic matter in natural aqueous environments can interact with ZnO NPs, thereby affecting their aggregation, sedimentation and biotoxicity. Here, we systematically investigated the effects of humic acid (HA) and sodium alginate (SA) on the aggregation behavior of ZnO NPs and their biotoxicity to Daphnia magna. High concentrations (9.0 mg/L) of HA and SA accelerated the aggregation of ZnO NPs with maximum aggregation rates (ΔD/Δt) of 22.1 and 19.2 nm/min, respectively. Both HA and SA led to 31.2% and 30.1% decrease of ZnO NPs concentration compared with the control experiment. The results calculated by Derjaguin-Landau-Verwey-Overbeek theoretical formula were consistent with these of aggregation and sedimentation of ZnO NPs. Furthermore, excitation-emission-matrix fluorescence spectroscopy verified that the carboxylic groups of HA and SA have high complexation capacity with ZnO NPs. Daphnia magna was used to evaluate the biotoxicity of ZnO NPs, and the toxicity of ZnO NPs to Daphnia magna was alleviated as the HA concentration increased from 0 to 1.2 mg/L. Toxicity mitigation experiments confirmed that photocatalytic generation of reactive oxygen species was more toxic to Daphnia magna than dissolved Zn2+ in acute and chronic toxicity tests. Moreover, the attacks of active oxygen free radical damaged the antioxidant system of Daphnia magna. The information obtained will help us to improve the understanding of the impacts of ZnO NPs on freshwater ecosystems.

Modifying ceramic membranes with in situ grown iron oxide nanoparticles and their use for oily water treatment

A facile technique for impregnating commercial ceramic membranes with in situ grown iron oxide nanoparticles (NPs) and their use for synthetic produced water treatment is presented. Unlike most literature, our technique led to NPs forming on the surface as well as within the pores of the membrane. The antifouling properties of the membrane were evaluated in terms of surface characteristics, hydrophilicity, fouling characteristics, organic rejection, and regeneration capacity. The contact angle and the rate of water penetration were used to determine optimum precursor concentration for which membrane hydrophilicity is improved without major pore blockage due to NP agglomeration and deposition. At such concentration, in situ generation of the NPs, mostly with sizes less than 4 nm, did not affect membrane morphology, porosity or the intrinsic hydraulic resistance. Membrane organic rejection and fouling behavior showed considerable enhancement in humic acid, a model natural organic matter also existing in produced water, retention at different transmembrane pressures. Organic rejection along with the permeate flux suggest fouling transition from concentration polarization and pore plugging to gel/cake layer formation occurs at higher critical gel concentration for the modified membranes. The steady permeate flux for modified and unmodified membranes are comparable, especially at higher humic acid concentration, and flux recovery and fouling ratios reveal enhanced antifouling properties. A new dimensionless number, membrane performance number, is introduced to couple the performance of the membrane in terms of permeate flux and contaminant rejection.

Impact of CeO2 nanoparticles on the aggregation kinetics and stability of polystyrene nanoplastics: Importance of surface functionalization and solution chemistry

The increasing application of plastics is accompanied by increasing concern over the stability and potential risk of nanoplastics. Heteroaggregation with metal-based nanoparticles (e.g., CeO2-NPs) is critical to the environmental mobility of nanoplastics, as they are likely to be jointly emitted to the aquatic environment. Here, time-resolved dynamic light scattering was employed to evaluate the influence of CeO2-NPs on the aggregation kinetics of differentially surface functionalized polystyrene nanoplastics (PS-NPs) in various water types. Natural organic matters and ionic strength were dominating factors influencing the heteroaggregation of PS-NPs and CeO2-NPs in surface waters. The critical coagulation concentrations of PS-NPs were dependent on their surface coatings, which decreased in the presence of CeO2-NPs due to electrostatic attraction and/or specific adsorption. Incubation of PS-NPs and CeO2-NPs under different pH confirmed the importance of electrostatic force in the aggregation of PS NPs. A relatively low humic acid (HA) concentration promoted the heteroaggregation of NH2-coated PS-NPs and CeO2-NPs because the introduction of a HA surface coating decreased the electrostatic hindrance. At high HA concentrations, the aggregation was inhibited by steric repulsion. The combined effects of high efficiency of double layer compression, bridging and complexation contributed to the high capacity of Ca2+ in destabilizing the particles. These findings demonstrate that the environmental behavior of nanoplastics is influenced by the presence of other non-plastic particles and improve our understanding of the interactions between PS-NPs and CeO2-NPs in complex and realistic aqueous environments.

EFFECT OF ADDITION HUMIC AND PROLINE ACID IN THE PRODUCTIVITY OF CORN UNDER WATER STRESS

This study was carried out in th (Adai village) of Baquba during the spring season 2018 in order to find the effect of different concentrations of proline and humic acid and irrigation divergence intervals and their interaction in the anatomical characteristics of maize plants Zea mysa L. The experiment included spraying plants with concentrations of 0,100,200,300 mg. L-1 proline acid and the use of four concentrations of humic acid 0.1, 2, 3 gm.m-2 Irrigation intervals were spaced every 5, 10 and 15 days. This experiment involved the study of the number of vascular bundles in the leg, the number of vascular bundles in the middle race of the leaves and the stomatal coefficient of the upper and lower epidermis, and the frequency of the upper and lower epidermis of the yellow maize plants. . The results indicated the following. Significant effect was shown in the case of adding high concentrations of proline and humic acid or spraying them together. Also significant effects were due to overlap between them and reducing the negative effects of water stress due to divergence of irrigation durations.