Due to the similar sources of swage irrigation, organic fertilizer, and sludge application, microplastics (MPs) and antibiotics coexist inevitably in the agriculture soils. However, the impacts of MPs with different polymer types and aging status on the bio-accessibility of co-existing antibiotics in soils remained unclear. Therefore, we using the diffusive gradients films for organic compounds devices (o-DGT) to evaluated the distribution of sulfadiazine (SDZ) in both paddy soil and saline soil amended with 0.5 % (w/w) MPs. Four polymer types (polyethylene: PE, polypropylene: PP, polyamide: PA, and polyethylene terephthalate: PET) and two aging statuses (aged PE and aged PP) of MPs were used in this study. Results showed that soil properties significantly influence the partition of SDZ in soil and soil solution, and SDZ gained a lower degradation rate but higher mobility in saline soil. MPs pose different impacts on partition of SDZ between paddy soil and saline soil. Notably, PP reduced the labile solid phase-solution phase partition coefficient (Kdl) by 17.7 % in paddy soil, while PE, PP, and aPE increased the Kdl value by 2.00, 1.62, and 2.81 times in saline soil. Besides, in saline soil, all the MPs reduced the SDZ concentration in the soil solution, while significantly increased the SDZ in o-DGT phase. Conversely, MPs did not impact the SDZ's o-DGT concentration in paddy soil. Additionally, MPs increased the R value of SDZ in two soils, especially in saline soil. It suggested that MPs could potentially enhance the resupply of SDZ from soil to plants, particularly under saline conditions. Furthermore, aged MPs had a more pronounced effect on these indicators compared to virgin MPs in saline soil. Therefore, MPs in soil poses a potential risk for biota's uptake of SDZ, particularly in fragile environment. Moreover, the risk intensifies with aged MPs.
Understanding the source identification and distribution of heavy metal(loid)s in soil is essential for risk management. The sources of heavy metal(loid)s in farmland soil, especially in areas with rapid economic development, were complicated and need to be explored urgently. This study combined geographic information system (GIS) mapping, positive matrix factorization (PMF) model and cadmium (Cd) isotope fingerprinting methods to identify heavy metal(loid) sources in a typical town in the economically developed Yangtze River Delta region of China. Cd, As, Cu, Zn, Pb, Ni and Co in different samples were detected. The results showed that Cd was the most severely contaminated element, with an exceedance rate of 78.0 %. GIS mapping results indicated that the hotspot area was located in the northeastern area with prolonged operational histories of electroplating and non-ferrous metal smelting industries. The PMF model analysis also identified emissions from smelting and electroplating enterprises as the main sources of Cd in the soil, counted for 49.28 %, followed by traffic (25.66 %) and agricultural (25.06 %) sources. Through further isotopic analysis, it was found that in soil samples near the industrial park, the contribution of electroplating and non-ferrous metal smelting enterprises to cadmium pollution was significantly higher than other regions. The integrated use of various methodologies allows for precise analysis of sources and input pathways, offering valuable insights for future pollution control and soil remediation endeavors.
Root exudates are pivotal in plant stress responses, however, the impact of microplastics (MPs) on their release and characteristics remains poorly understood. This study delves into the effects of 0.05 % and 0.1 % (w/w) additions of polyethylene (PE) MPs on the growth and physiological properties of lettuce (Lactuca sativa L.) following 28 days of exposure. The release characteristics of root exudates were assessed using UV-vis and 3D-EEM. The results indicated that PE increased leaf number but did not significantly affect other agronomic traits or pigment contents. Notably, 0.05 % PE increased the total root length and surface area compared to the 0.1 % addition, while a non-significant trend towards decreased root activity was observed with PE MPs. PE MPs with 0.1 % addition notably reduced the DOC concentration in root exudates by 37.5 %, while 0.05 % PE had no impact on DOC and DON concentrations. PE addition increased the SUVA254, SUVA260, and SUVA280 values of root exudates, with the most pronounced effect seen in the 0.05 % PE treatment. This suggests an increase of aromaticity and hydrophobic components induced by PE addition. Fluorescence Regional Integration (FRI) analysis of 3D-EEM revealed that aromatic proteins (region I and II) were dominant in root exudates, with a slight increase in fulvic acid-like substances (region III) under 0.1 % PE addition. Moreover, prolonged PE exposure induced ROS damage in lettuce leaves, evidenced by a significant increase in content and production rate of O2·-. The decrease in CAT and POD activities may account for the lettuce's response to environmental stress, potentially surpassing its tolerance threshold or undergoing adaptive regulation. These findings underscore the potential risk of prolonged exposure to PE MPs on lettuce growth.
Microplastics , Plastics , Microplastics/metabolism , Plastics/metabolism , Polyethylene/metabolism , Lactuca , Hydroponics , Oxidative Stress
Micro/nanoplastics (MPs) are attracting increasing attention owing to the potential threats they pose to the sustainability of the environment and the health of living organisms. Thus, a comprehensive understanding of the influence of MPs on living organisms is vital for developing countermeasures. We conducted an extensive literature search to retrieve the articles related to MPs via the Web of Science. Accordingly, 152 articles published in the last decade and in influential journals were selected to analyze the effects of MPs on plants, animals, microorganisms, and humans as well as the current status, hotspots, and trends of studies on MPs. The results showed that owing to the special characteristics of MPs and anthropogenic activities, MPs have become ubiquitous worldwide. MPs are ingested by plants and animals and enter the human body through various pathways, resulting in numerous adverse effects, such as growth inhibition, oxidative stress, inflammation, organ damage, and germ cell lesions. Moreover, they affect microorganisms by reshaping the structure and function of microbial communities and changing the spread pathway. However, microorganisms can also contribute to the degradation of MPs. With increasing evidence of the adverse effects of MPs on biota, coping with MP pollution and mitigating harmful outcomes have emerged as major challenges. This review focuses on (1) the main effects of MPs on living organisms, ranging from microorganisms to humans, (2) the current status and hotspots of studies related to MPs, and (3) the challenges and prospects of further studies on MPs.
Microplastics , Water Pollutants, Chemical , Animals , Humans , Plastics , Environmental Pollution , Water Pollutants, Chemical/analysis , Ecosystem
Objective: To study the differences in computed tomography angiography (CTA) imaging of gothic arches, crenel arches, and romanesque arches in children with Aortic Coarctation (CoA), and to apply computational fluid dynamics (CFD) to study hemodynamic changes in CoA children with gothic arch aorta. Methods: The case data and CTA data of children diagnosed with CoA (95 cases) in our hospital were retrospectively collected, and the morphology of the aortic arch in the children was defined as gothic arch (n = 27), crenel arch (n = 25) and romanesque arch (n = 43). The three groups were compared with D1/AOA, D2/AOA, D3/AOA, D4/AOA, D5/AOA, and AAO-DAO angle, TAO-DAO angle, and aortic arch height to width ratio (A/T). Computational fluid dynamics was applied to assess hemodynamic changes in children with gothic arches. Results: There were no significant differences between D1/AOA and D2/AOA among gothic arch, crenel arch, and romanesque arch (P > 0.05). The differences in D3/AOA, D4/AOA, and D5/AOA among the three groups were statistically significant (P < 0.05), D4/AOA, D5/AOA of the gothic arch group were smaller than the crenel arch group, and the D3/AOA and D5/AOA of the gothic arch group were smaller than the romanesque arch group (P < 0.05). The difference in AAO-DAO angle among the three groups was statistically significant (P < 0.05), and the AAO-DAO angle of gothic arch was smaller than that of romanesque arch and crenel arch group (P < 0.05). There was no significant difference in the TAO-DAO angle between the three groups (P > 0.05). The difference in A/T values among the three groups was statistically significant (P < 0.05), and the A/T values: gothic arch > romanesque arch > crenel arch (P < 0.05). The CFD calculation of children with gothic arch showed that the pressure drop between the distal stenosis and the descending aorta was 58â mmHg, and the flow rate at the isthmus and descending aorta was high and turbulent. Conclusion: Gothic aortic arch is common in CoA, it may put adverse effects on the development of the aortic isthmus and descending aorta, and its A/T value and AAO-DAO angle are high. CFD could assess hemodynamic changes in CoA.
The application of plastic mulch film could effectively enhance the productivity of facility agriculture. However, releasing microplastic and phthalate from mulch films in soil has attracted increasing concerns, and releasing characters of microplastic and phthalate from mulch films during their mechanical abrasion remains unclear. This study elucidated the dynamics and impact factors of microplastic generation, including the thickness, polymer types and ageing of mulch film during mechanical abrasion. Releasing characters of the di(2-Ethylhexyl) phthalate (DEHP), a common type of phthalate in soil, from mulch film during mechanical abrasion were also explored. Results showed that 2 pieces of mulch film debris increased to 1291 pieces of microplastic after five days of mechanical abrasion, with exponential growth in the microplastic generation. After mechanical abrasion, the thinnest (0.008 mm) mulch film completely transformed into microplastics. However, the thicker mulch (>0.01 mm) suffered slight disintegration, making it feasible to be recycled. The biodegradable mulch film discharged the most microplastics (906 pieces) compared with the HDPE (359 pieces) and LDPE (703 pieces) mulch film after three days of mechanical abrasion. In addition, the mild thermal and oxidative ageing could result in 3047 and 4532 pieces of microplastic emissions from mulch film after three days of mechanical abrasion, which were ten times more than the original mulch film (359 pieces). Furthermore, negligible DEHP was released from mulch film without mechanical abrasion, while the released DEHP significantly correlated with generated microplastics during mechanical abrasion. These results demonstrated the crucial role of mulch film disintegration in phthalate emissions.
Microplastics (MPs) contamination in soils seriously threatens agroecosystems globally. However, very few studies have been done on the effects of MPs on the soil nitrogen cycle and related functional microorganisms. To assess MP's impact on the soil nitrogen cycle and related functional bacteria, we carried out a one-month soil incubation experiment using typical acidic soil. The soil was amended with alfalfa meal and was spiked with 1% and 5% (mass percentage) of low-density polyethylene (LDPE) and polyvinyl chloride (PVC) MPs. Our results showed that both LDPE and PVC addition significantly increased soil nitrification rate and nitrate reductase activity, which could further promote soil denitrification. The relative abundance of diazotrophs, ammonium oxidizing, and denitrifying bacterial groups were significantly altered with MPs addition. Moreover, the MPs treatments greatly enhanced denitrifying bacteria richness. Redundancy analysis showed that nitrate reductase activity was the most significant factor affecting the soil functional bacterial community. Correlation analysis shows that Nitrosospira genus might be for the improvement of soil nitrification rate. Our results implied that MPs exposure could significantly affect the soil nitrogen cycling in farmland ecosystems by influencing essential nitrogen functional microorganisms and related enzymatic activities.
Nitrification , Polyethylene , Polyethylene/pharmacology , Microplastics/pharmacology , Plastics , Polyvinyl Chloride , Ecosystem , Soil , Nitrogen/pharmacology , Bacteria , Nitrate Reductases/pharmacology , Soil Microbiology
Microplastics (MPs) and sulfamethoxazole (SMX) are emerging contaminants that are ubiquitous in the soil environment. In this study, we investigated MPs polymer type and soil environmental factor effects on SMX adsorption behavior in the soil system. Our results showed that MPs dosage affected the soil particles' SMX adsorption rate and capacity (Qe). Adding 1 % polystyrene (PS) increased the SMX adsorption rate significantly. The value of K1, which represented the adsorption rate, increased from 0.569 h-1 to 1.019 h-1. However, the addition of MPs reduced the soil's SMX equilibrium adsorption capacity slightly. Moreover, increasing salinity strength enhanced SMX adsorption capacity by MPs significantly. However, increasing calcium ions concentration decreased SMX adsorption in the MPs amended soil due to multivalent cationic bridging and competitive adsorption mechanisms. In addition, we observed that fulvic acid addition inhibited SMX adsorption. This study suggests that the addition of MPs reduced the adsorption of SMX in the soil slightly due to dilution effect. Meanwhile, changes in environmental factors also affected the adsorption behavior of SMX in soil amended with MPs.
Microplastics , Soil , Sulfamethoxazole , Plastics , Polymers , Osmolar Concentration , Adsorption
The large amount of untreated pyrite tailings has caused serious environmental problems, and the recycling of pyrite tailings is considered as an attractive strategy. Here, we reported a novel non-sintered ceramsite prepared with pyrite tailings (PTNC) as the main active raw material for phosphorus control, and the dosage effect of ingredients on total phosphorus (TP) removal ability was investigated. The results from Plackett-Burman Design (PBD) suggested the dosages of dehydrated sludge, sodium bicarbonate, and cement were the factors which significantly affect the TP removal ability. The Box-Behnken Design (BBD) based response surface methodology was further employed, and it indicated the interactions between different factors, and the optimized recipe for PTNC was 84.5 g (pyrite tailings), 10 g (cement), 1 g (calcined lime), 1 g (anhydrous gypsum), 3 g (dehydrated sludge), and 0.5 g (sodium bicarbonate). The optimized PTNC was characterized and which presented much higher specific area (7.21 m2/g) than the standard limitation (0.5 m2/g), as well as a lower wear rate (2.08%) rather than 6%. Additionally, the leaching metal concentrations of PTNC were far below the limitation of Chinese National Standard. The adsorption behavior of TP on PTNC was subsequently investigated with batch and dynamic experiments. It was found that the calculated max adsorption amount (qmax) was about 7 mg/g, and PTNC was able to offer a stable TP removal ability under different hydraulic retention time (HRT). The adsorption mechanism was discussed by model fitting analysis combined with XRD and SEM characterization, and cobalt phosphide sulfide was observed as the newly formed substance through the adsorption process, which suggested the existing of both physical and chemical adsorption effect. Our research not only offered an economic preparation method of ceramsite, but also broadened the recycling pathway of pyrite tailings.
1,4-Dioxane degradation under both batch-scale and column experiments has been investigated within the biochar activated peroxymonosulfate (PMS) system for in-situ remediation of 1,4-dioxane contaminated groundwater. In case of the batch experiments, the 1,4-dioxane degradation efficiencies were significantly increased with the increased biochar pyrolysis temperatures. The optimized 1,4-dioxane degradation efficiency at 89.2% was achieved with 1.0 g L-1 of biochar (E800) and 8.0 mM PMS. In the absence of PMS, the breakthrough rates of 1,4-dioxane in biochar packed column experiments under the dynamic flow conditions were relatively slow compared with those in sand packed columns. Simultaneously, based on the integrated areas (IA) from the 1,4-dioxane breakthrough curves, the degradation efficiency at 70.2% was estimated in biochar packed column (WE800:WSand = 1:9) under continuous injections of 16.0 mM PMS. Electron paramagnetic resonance (EPR) indicated that hydroxyl, sulfate and superoxide radicals were generated within the biochar/PMS systems and alcohol quenching experiments suggested that the dominated hydroxyl and sulfate radicals were responsible for 1,4-dioxane degradation. The findings of this study suggested that the biochar activated PMS system is a promising and cost-effective strategy for the remediation of 1,4-dioxane contaminated groundwater.
Charcoal , Peroxides , Dioxanes
The attapulgite of different morphologies and mineral compositions were successfully obtained following the treatment by HCl and HF with different concentrations. Variations of morphologies, elemental and mineral components of the pristine and modified attapulgite were investigated and assessed in detail by a series of characterization methods. The SEM-EDS results indicated significant variations on the contents and morphologies of silicon after acid modification. The Cr(VI) removal efficiencies under pristine and modified attapulgite-supported nZVI composites were evaluated with the removal rate in case of 0.5HAT-nZVI being 69.2% more superior than that of 6FAT-nZVI. The reaction kinetic is well fitted with pseudo second order kinetics model. The correlation analysis indicated that Cr(VI) removal efficiency was positively correlated with the content of active silicon in the attapulgite-nZVI composites (R2 = 0.979∗∗). Additionally, the reduction of Cr(VI) is more likely to occur in silicon-rich composites based on the analysis of XPS spectra and Cr concentration changes, which were mainly attributed to the enhanced Si-O-Fe coupling mediated by silicon. Attapulgite with more exposure sites of silicon enhanced the Cr(VI) reduction process and promoted crystallization of the reaction products. Simultaneously, the nZVI consumption caused by oxidation and aggregation were improved by silicon in attapulgite. It is concluded that silicon played a significant role on Cr(VI) removal through the reductive precipitation by Si-O-Fe coupling.
Iron , Water Pollutants, Chemical , Chromium/analysis , Magnesium Compounds , Silicon , Silicon Compounds , Water Pollutants, Chemical/analysis
Biochar pyrolysed at 300 °C, 500 °C, 700 °C was modified by hydrochloric acid (HCl), hydrofluoric acid (HF), sodium hydroxide (NaOH), hydrogen peroxide (H2O2), nitric acid (HNO3) and potassium permanganate (KMnO4), and subsequently evaluated for removal efficiency of 1,2,4-trichlorobenzene (1,2,4-TCB) by biochar supported nanoscale zero-valent iron (nZVI) and palladium (Pd) composites. Under the initial 1,2,4-TCB concentration of 10 mg L-1 and the solid-liquid ratio of 0.16 g L-1, the synthesized composites of nZVI-Pd with BC700 modified by HF (FBC700-nZVI-Pd) and nZVI-Pd with BC300 modified by NaOH (SBC300-nZVI-Pd) demonstrated significantly enhanced removal efficiencies for 1,2,4-TCB achieving 98.8% and 94.7% after 48 h, respectively. The physicochemical properties of biochar including specific surface area, aromaticity and hydrophobicity after the modification by HF and NaOH were improved. Increased the supporting sites for Fe/Pd nanoparticles and the contact between composites and 1,2,4-TCB were mainly responsible for enhanced removal efficiency for 1,2,4-TCB. Both the adsorption by biochar and reduction by Fe/Pd nanoparticles effectively contributed to the removal of 1,2,4-TCB. It is estimated that the proportion of reduction was about twice that of adsorption in the first 12 h, which produced 1,2-DCB, benzene and other degradation products. Therefore, biochar treated with HF and NaOH and supported Fe/Pd nanoparticles could be effective functional materials for remediation of groundwater contaminated by 1,2,4-TCB.
Chlorobenzenes/chemistry , Iron/chemistry , Palladium/chemistry , Water Pollutants, Chemical/chemistry , Water Purification/methods , Adsorption , Charcoal , Groundwater/chemistry , Hydrogen Peroxide , Nanoparticles , Water Pollutants, Chemical/analysis
A novel insight on the role of interactions between target pollutants and the catalyst in the copper-containing layered double oxide (LDO)-catalyzed persulfate (PS) system was elucidated in the present study. 4-Chlorophenol (4-CP), as a representative benzene derivative with a hydroxyl group, was completely removed within 5 min, which was much faster than the reaction of monochlorobenzene (MCB) without a hydroxyl group, with the degradation efficiency of 31.7% in 240 min. Through the use of radical quenching and surface inhibition experiments, it could be concluded that the interaction between 4-CP and CuMgFe-LDO, rather than free radicals, played a key role in the decomposition of 4-CP, while only the free radicals participated in the MCB degradation process. According to electron paramagnetic resonance and X-ray photoelectron spectroscopy data, the formation of a Cu(II)-complex between phenolic hydroxyl groups and surface Cu(II) was primarily responsible for the degradation of phenolic compounds, in which PS accepted one electron from the complex and generated sulfate radicals and chelated radical cations. The chelated radical cations transferred one electron to Cu(II) followed by Cu(I) generation and pollutant degradation successively.
Benzene Derivatives , Environmental Pollutants , Catalysis , Hydroxyl Radical , Oxidation-Reduction , Oxides , Sulfates
The application of biochar-supported nanoscale zero-valent iron (biochar-nZVI) was successfully implemented in a field demonstration for the first time. To overcome the significant shortcomings of nZVI agglomeration for in-situ groundwater remediation, biochar-nZVI was injected into groundwater using direct-push and water pressure driven packer techniques for a site impacted by chlorinated solvents in the North China Plain. The field demonstration comprising two-step injections was implemented to demonstrate the effectiveness of nZVI and biochar-nZVI respectively. The outcome of the demonstration revealed a sharp reduction of contaminant concentrations of chlorinated solvents in 24â¯h following the first injection of nZVI, but the rebound of the concentrations of these contaminants in groundwater has occurred within the next two weeks. However, application of biochar-nZVI greatly enhanced the removal of chlorinated solvents in groundwater over the longer period of 42â¯days. The enhanced removal of chlorinated solvents in groundwater by biochar-nZVI is mainly attributed to the synergistic effects of adsorption and reduction. The adsorption by biochar significantly reduced the level of chlorinated solvents in groundwater. Overall increases in ferrous iron and chloride concentrations after the injections indicated that the reduction has occurred during the removal of chlorinated solvents in groundwater. In summary, biochar-supported nZVI could be potentially used for the effective remediation of chlorinated solvents in groundwater.
The attapulgite supported nanoscale zero-valent iron composite (AT-nZVI) was synthesized and used for Cr(VI) removal. X-ray diffraction (XRD) and transmission electron microscope (TEM) indicated that nZVI particles were well distributed and immobilized on the attapulgite surface. Batch experiments of Cr(VI) removal were conducted at varying mass ratios, initial Cr(VI) concentrations and kinetics. The results indicated that the removal efficiency of Cr(VI) by AT-nZVI approaches 90.6%, being greater than that by non-supported nZVI (62.9%). The removal kinetics could be more accurately explained using pseudo second order kinetics model. The composite exhibited a synergistic interaction instead of simple mixture of AT and nZVI. Reduction was the dominant mechanism at low concentrations as opposed to adsorption at high concentrations. FeCr2O4 was the main reduction product by AT-nZVI, which was attributed to the reduction of Cr(VI) by nZVI and co-precipitation of CrFe oxides on the surface of AT. In the meantime, Fe(II) ion contributed to 64% for the Cr(VI) removal, which resulted from the dissolution of nZVI during the removal process. From the analysis of XRD and XPS results, the crystallization of FeCr2O4 is believed to be formed easily after the reaction of the AT-nZVI composite with Cr(VI) which is more stable and greatly reduce the risk of secondary pollution compared with nZVI. The introduction of AT enhanced adsorption of Cr(VI) and crystallization of the products. The above results suggested that AT-nZVI could be a promising remediation material for Cr(VI)-contaminated groundwater.
Chromium/isolation & purification , Environmental Restoration and Remediation/methods , Iron/chemistry , Water Pollutants, Chemical/analysis , Adsorption , Crystallization , Groundwater/chemistry , Kinetics , Magnesium Compounds/chemistry , Silicon Compounds/chemistry
The potential of silicon-rich biochar and Pd were evaluated for the enhanced removal of Cr(VI) in solution by nanoscale zero-valent iron (nZVI) composites. The composition and structures of the nZVI, RS700-supported nZVI, and Pd-doped samples were analyzed by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy before and after reaction with Cr(VI). The amount of Cr(VI) removed by nZVI-RS700-Pd was considerably greater than the removal by nZVI, nZVI-Pd, or nZVI-RS700. This was mainly due to the enhanced reduction and adsorption of Cr(VI) by silicon-rich biochar and Pd. Silicon and Pd promoted the reduction of Cr(VI) due to the Fe0 crystallinity in the nZVI structures. The significantly decreased removal of Cr(VI) by the silicon-removed sample (nZVI-RS700 (-Si)) further confirmed that silicon played a significant role in the removal of Cr(VI). Cr(VI) adsorption was enhanced by the dispersion and adsorption of RS700. Following the reaction of RS700-supported nZVI with Cr(VI), ferrous chromite (FeCr2O4) was observed on the nZVI-RS700 composite surface. The formation of FeCr2O4 can be attributed to the reduction of Cr(VI) by the nZVI and coprecipitation of chromium oxide with iron on the RS700 surface. Therefore, nZVI-RS700-Pd is a potential remediation reagent that can be used to effectively treat Cr(VI)-contaminated groundwater.
Chromium/chemistry , Iron/chemistry , Nanoparticles/chemistry , Palladium/chemistry , Silicon/chemistry , Adsorption , Oxidation-Reduction , Particle Size , Surface Properties
Silicon-rich biochar-supported nanoscale zero-valent iron (nZVI) was studied to evaluate enhanced removal of hexavalent chromium (Cr(VI)) in solution. The compositional structures of the nZVI and biochar-supported nZVI were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectra before and after Cr(VI) reaction. The removal amount of Cr(VI) by nZVI-RS700 (rice straw pyrolyzed at 700⯰C) was considerably greater than that by nZVI and other biochar-supported nZVI samples. Upon the silicon was removed from RS700 (nZVI-RS700(-Si)), a significant decreased removal of Cr(VI) was observed. It was revealed that nZVI supported by silicate particles of biochar and the promotion of iron oxidation by SiO2 both contribute to the enhanced Cr(VI) removal. We found that the reduction and adsorption both contributed to the removal of Cr(VI), ferrous chromite (FeCr2O4) was observed on the surface of the nZVI-RS700 composite. The formation of FeCr2O4 is attributed to the reduction of Cr(VI) by nZVI and the adsorption of chromium oxide with iron on the surface of RS700. Therefore, RS700-supported nZVI can be used as a potential remediation reagent to treat Cr(VI)-contaminated groundwater.
Charcoal/chemistry , Chromium/isolation & purification , Groundwater/chemistry , Iron/chemistry , Nanotechnology , Silicon/chemistry , Water Pollutants, Chemical/isolation & purification , Chromium/analysis , Water Pollutants, Chemical/analysis , Water Purification
Nano magnetite biochar composite (nFe3O4/biochar) was synthesized and used to activate persulfate for the degradation of 1,4-dioxane. Analytical techniques using X-ray diffraction (XRD), fourier transform infrared analysis (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) indicated that nFe3O4 was spherical and successfully loaded onto the surface of biochar. The results of batch-scale experiments illustrated that the 1,4-dioxane degradation efficiency in aqueous phase was 98.0% after 120 min reaction with the composite mass ratio of 1:1 between nFe3O4 and the pine needle biochar pyrolyzed at 400 °C (P400) under the initial neutral pH. An electron paramagnetic resonance (EPR) study, free radical quenching experiment and XPS analysis were undertaken to illustrate the mechanism of persulfate activation by nFe3O4/biochar. Under acidic and neutral conditions, the predominant free radical was SO4- whereas OH and SO4- predominated when the initial pH was 9.0. The XPS analysis indicated that Fe(II) and oxygenated functional groups activated persulfate. In addition, carbon-carbon double bonds would be transformed into ketone and quinone which could activate persulfate during the reaction.
Charcoal/chemistry , Dioxanes/chemistry , Ferrosoferric Oxide/chemistry , Nanoparticles/chemistry , Free Radicals/chemistry , Microscopy, Electron, Scanning , Photoelectron Spectroscopy , Sulfates/chemistry , X-Ray Diffraction
CuMgFe layered double hydroxide (CuMgFe-LDH) was successfully synthesized and characterized as an efficient catalyst of persulfate (PS) for the degradation of ethylbenzene. Under the conditions of 0.2gL-1 CuMgFe-LDH and 4.0mmolL-1 persulfate at pH 7.6, the degradation efficiency of 0.08mmolL-1 ethylbenzene was 93.7% with TOC removal efficiency of 65.2% in 24h, and the concentration of Cu leached into the solution was as low as 0.095mgL-1 after the reaction. The reuse of CuMgFe-LDH showed that the catalyst was highly stable after 5 recycles. Electron Spin Resonance (ESR) test and free radical quenching experiment indicated that SO4- and OH radicals were the dominant species accounted for the degradation of ethylbenzene in the CuMgFe-LDH/persulfate system. Catalytic mechanism of the formation of a complex of Cu(II)O3SOOSO32- and the subsequent redox cycle of Cu(II)/Cu(III) accounted for the generation of radicals was proposed.
Composite of nanoscale Zero Valent Iron (nZVI) loaded on Biochar (BC) was prepared and characterized as hydrogen peroxide (H2O2) activator for the degradation of trichloroethylene (TCE). nZVI is homogeneously loaded on lamellarly structured BC surfaces to form nZVI/BC with specific surface area (SBET) of 184.91 m2 g-1, which can efficiently activate H2O2 to achieve TCE degradation efficiency of 98.9% with TOC removal of 78.2% within 30 min under the conditions of 0.10 mmol L-1 TCE, 1.13 g L-1 nZVI/BC and 1.50 mmol L-1 H2O2. Test results from the Electron Spin Resonance (ESR) measurement and coumarin based fluorescent probe technology indicated that âOH radicals were the dominant species responsible for the degradation of TCE within the nZVI/BC-H2O2 system. Activation mechanism of the redox action of Fe2+/Fe3+ generated under both aerobic and anaerobic conditions from nZVI and single electron transfer process from BC surface bound C-OH to H2O2 promoted decomposition of H2O2 into âOH radicals was proposed.
