RÉSUMÉ
This study synthesized a new thiomalic acid-modified rice husk biochar (TMA-BC) as a versatile and eco-friendly sorbent. After undergoing chemical treatments, the mercerized rice husk biochar (NaOH-BC) and TMA-BC samples showed higher BET surface area values of 277.1 m2/g and 305.8 m2/g, respectively, compared to the pristine biochar (BC) sample, which had a surface area of 234.2 m2/g. In batch adsorption experiments, it was found that the highest removal efficiency for malachite green (MG) was achieved with TMA-BC, reaching 96.4%, while NaOH-BC and BC exhibited removal efficiencies of 38.6% and 27.9%, respectively, at pH 8. The engineered TMA-BC exhibited a super adsorption capacity of 104.17 mg/g for MG dye at pH 8.0 and 25 °C with a dosage of 2 g/L. The SEM, TEM, XPS, and FTIR spectroscopy analyses were performed to examine mesoporous features and successful TMA-BC carboxylic and thiol functional groups grafting on biochar. Electrostatic forces, such as π - π interactions, hydrogen bonding, and pore intrusion, were identified as key factors in the sorption of MG dye. As compared to single-solution adsorption experiments, the binary solution experiments performed at optimized dosages of undesired ions, such as humic acid, sodium dodecyl sulfate surfactant, NaCl, and NaSCN, reflected an increase in MG dye removal of 2.8%, 8.7%, 5.4%, and 12.7%, respectively, which was attributed to unique mesoporous features and grafted functional groups of TMA-BC. Furthermore, the TMA-BC showed promising reusability up to three cycles. Our study indicates that mediocre biochar modified with TMA can provide an eco-friendly and cost-effective alternative to commercially accessible adsorbents.
Sujet(s)
Magenta I , Polluants chimiques de l'eau , Ligands , Hydroxyde de sodium , Polluants chimiques de l'eau/composition chimique , Cinétique , Charbon de bois/composition chimique , AdsorptionRÉSUMÉ
The widespread use of tetracycline (TC) inevitably leads to its increasing emission into groundwater. However, the potential risks of TC to denitrification in groundwater remain unclear. In this study, the effects of TC on denitrification in groundwater were systematically investigated at both the protein and gene levels from the electron behavior aspect for the first time. The results showed that increasing TC from 0 to 10 µg·L-1 decreased the nitrate removal rate from 0.41 to 0.26 mg·L-1·h-1 while enhancing the residual nitrite concentration from 0.52 mg·L-1 to 50.60 mg·L-1 at the end of the experiment. From a macroscopic view, 10 µg·L-1 TC significantly inhibited microbial growth and altered microbial community structure and function in groundwater, which induced the degeneration of denitrification. From the electron behavior aspect (the electron production, electron transport and electron consumption processes), 10 µg·L-1 TC decreased the concentration of electron donors (nicotinamide adenine dinucleotide, NADH), electron transport system activity, and denitrifying enzyme activities at the protein level. At the gene level, 10 µg·L-1 TC restricted the replication of genes related to carbon metabolism, the electron transport system and denitrification. Moreover, discrepant inhibitory effects of TC on individual denitrification steps, which led to the accumulation of nitrite, were observed in this study. These results provide the information that is necessary for evaluating the potential environmental risk of antibiotics on groundwater denitrification and bring more attention to their effects on geochemical nitrogen cycles.
Sujet(s)
Nappe phréatique , Nitrites , Dénitrification , Tétracycline/pharmacologie , Antibactériens/pharmacologie , Nitrates/métabolisme , Nappe phréatique/composition chimiqueRÉSUMÉ
Fenton-like oxidation processes are widely used to degrade recalcitrant organic pollutants, but are limited by narrow application pH and low reaction efficiency. This study investigated the synchronous activation of H2O2 and persulfate (PDS) by sulfidated zero valent iron (S-nZVI) in ambient conditions for Fenton-like oxidation of bisphenol S (BPS), an estrogenic endocrine-disrupting chemical. The activation of S-nZVI induced H2O2 or PDS could be greatly enhanced with the assistance of PDS and H2O2, respectively, even across a wide range of pH value (3-11). The first-order rate constant of S-nZVI/H2O2/PDS, S-nZVI/PDS and S-nZVI/H2O2 systems was found to be 0.2766 min-1, 0.0436 min-1, and 0.0113 min-1, respectively. A significant synergy between H2O2 and PDS was achieved when the PDS-H2O2 molar ratio was above 1:1, and where sulfidation promoted iron corrosion and decreased solution pH were observed in the S-nZVI/H2O2/PDS system. Radical scavenging experiments and electron paramagnetic resonance (EPR) investigations suggest that both SO4â¢- and â¢OH were generated and that â¢OH played a crucial role in BPS removal. Furthermore, four BPS degradation intermediates were detected and three degradation pathways were proposed in line with the HPLC-Q-TOF-MS analysis. This study demonstrated that compared to the traditional Fenton-like system, the S-nZVI/H2O2/PDS system could be a more efficient, advanced oxidation technology capable of being used across a broad pH range for emerging pollutants' degradation.
Sujet(s)
Polluants environnementaux , Polluants chimiques de l'eau , Peroxyde d'hydrogène , Fer/analyse , Polluants chimiques de l'eau/analyse , Polluants environnementaux/analyseRÉSUMÉ
Reactors were established to study the feasibility of the direct addition of modified biochar to alleviate the long-term stress of oxytetracycline (OTC) on aerobic denitrification (AD) and improve the stability of the system. The results showed that OTC stimulated at µg/L, and inhibited at mg/L. The higher the concentration of OTC, the longer the system was affected. The addition of biochar, without immobilization, improved the tolerance of community, alleviated the irreversible inhibition effect of OTC, and maintained a high denitrification efficiency. Overall, the main mechanisms of AD enhancement by biochar under OTC stress were: enhancing the bacteria metabolic activity, strengthening sludge structure and substrate transport, and improving the community stability and diversity. This study confirmed that direct addition of biochar could effectively alleviate the negative effect of antibiotics on the microorganisms, strengthen the AD, which provided a new idea to broaden the application of AD technology in livestock wastewater.
Sujet(s)
Oxytétracycline , Oxytétracycline/pharmacologie , Dénitrification , Antibactériens/pharmacologie , Charbon de bois/pharmacologieRÉSUMÉ
Pollutant degradation via periodate ([Formula: see text]) and transitional metal oxides provides an economical, energy-efficient way for chemical oxidation process in environmental remediation. However, catalytic activation of periodate by manganese dioxide and the associated mechanism were barely investigated. In this study, four MnO2 polymorphs (α-, ß-, γ- and δ-MnO2) were synthesized and tested to activate [Formula: see text] for the degradation of sulfamethoxazole (SMX). The reactivity of different MnO2 structures followed the order of α-MnO2 > ß-MnO2 > γ-MnO2 > δ-MnO2, suggesting that the particular crystalline structure in α-MnO2 would exhibit higher activities via [Formula: see text] activation. Herein, in α-MnO2/[Formula: see text] system, 91.1% of SMX was eliminated within 30 min with degradation rate constant of 0.0649 min-1, and the neutral pH exhibited higher efficiency in SMX degradation compared with acidic and alkaline conditions. Singlet oxygen (1O2) was unveiled to be the dominant ROS according to the results of electron paramagnetic resonance, chemical probes and radical quenching experiments, whereas [Formula: see text] and â¢OH were mainly acted as a free-radical precursor. Six oxidation products were identified by LC-MS, and the elimination of sulfonamide bond, hydroxylation and direct oxidation were found to be the important oxidation pathways. The study dedicates to the mechanistic study into periodate activation over alpha-MnO2 and provides a novel catalytic activation for selective removal in aqueous contaminants.
Sujet(s)
Composés du manganèse , Polluants chimiques de l'eau , Oxydoréduction , Stress oxydatif , Oxydes , Acide orthoperiodique , Espèces réactives de l'oxygène , Sulfaméthoxazole , Polluants chimiques de l'eau/composition chimiqueRÉSUMÉ
A novel composite carrier (ICME-PS) was formed by coupling polyurethane sponge carriers (PS) with different pore sizes (15, 25, 40 ppi) and iron-carbon micro-electrolysis (ICME), which was used for enrichment of anammox bacteria and stable operation under no strict anaerobic condition. An increase of 5.67%-38.55% in specific anammox activity (SAA), an significant enhancement of biofilm stability and an improvement of 14.61%-42.38% in Ca.Brocadia were observed in ICME-PS, compared to PS carriers. ICME played a dual role: 1) contributed to the formation of an anaerobic microenvironment; 2) used for nitrogen cycle reactions. Additionally, small-pore carriers with highest biofilm stability can be used in high shear environments, while medium-pore carriers achieved the highest SAA in stable environments. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis indicated that ICME application reduced the energy barrier and improved aggregation performance. This study designed a novel composite carrier to broaden the application of anammox under no strict anaerobic condition.
Sujet(s)
Bioréacteurs , Carbone , Oxydation anaérobie de l'ammonium , Anaérobiose , Bactéries , Électrolyse , Fer , Azote , Oxydoréduction , PolyuréthanesRÉSUMÉ
This study provided a novel pathway to develop activated carbon with enhanced adsorption performance via feedstock pretreatment by fungi. The growth of Pleurotus ostreatus on cottonseed husks offered this feedstock an advantageous pore size for porous carbon making. The prepared activated carbons derived from cottonseed husks (CSH-ACs) during different fungal growth periods exhibited extraordinary performance than commercial activated carbon for sulfanilamide adsorptive removal. Their experimental data of adsorption capacities for sulfanilamide were 139.43, 146.15, and 146.16 mg g-1, respectively. The adsorption behaviors of sulfanilamide on CSH-ACs were evaluated by kinetic, isotherm and thermodynamic models. Pore filling, hydrogen-bond forming and π-π staking interactions all contributed to the rapid sulfanilamide removal. The microporous-mesoporous structure, stronger hydrophilicity, and richer functional groups moieties owing to the lignocellulose decomposition in the plant wall significantly strengthened the adsorption process on the microbial-mediated activated carbon. The effects of pH and water impurities (H2PO4-, CO32-, SO42-, Cl-, and humic acid) on sulfanilamide removal were investigated by a single factor experimental design. Results indicated that CSH-ACs were suitable for sulfanilamide removal in actual wastewater treatment with wide pH adaptability and resilience to interference.
Sujet(s)
Charbon de bois , Polluants chimiques de l'eau , Adsorption , Huile de coton , Concentration en ions d'hydrogène , Cinétique , SulfanilamideRÉSUMÉ
Doxycycline (DC) is a second generation tetracycline antibiotic and its occurrence in the aquatic environment due to the discharge of municipal and agricultural wastes has called for technologies to effectively remove DC from water. The objective of the study was to characterize the synergistic benefits of adsorption and biotransformation in removing DC from water using rice straw particles (RSPs) covered with DC degrading bacteria, Brevundimonas naejangsanensis strain DD1. First, optimal experimental conditions were identified for individual processes, i.e., hydrolysis, adsorption, and biotransformation, in terms of their performance of removing DC from water. Then, synergistic effects between adsorption and biotransformation were demonstrated by adding DD1-covered RSPs (DD1-RSPs) to DC-containing solution. Results suggest that DC was quickly adsorbed onto RSPs and the adsorbed DC was subsequently biotransformed by the DD1 cells on RSPs. The adsorption of DC to DD1-RSPs can be well described using the pseudo-second-order kinetics and the Langmuir isotherm. The DD1 cells on RSPs converted DC to several biotransformation products through a series of demethylation, dehydration, decarbonylation, and deamination. This study demonstrated that adsorption and biotransformation could work synergistically to remove DC from water.
Sujet(s)
Oryza , Polluants chimiques de l'eau , Adsorption , Biotransformation , Caulobacteraceae , Doxycycline , Concentration en ions d'hydrogène , Cinétique , Eau , Polluants chimiques de l'eau/analyseRÉSUMÉ
The feasibility of applying electric fields to mitigate inhibition of tetracycline (TC) on anammox process and improve system stability was evaluated in this study. Three electric field intensities of 1, 3 and a variable intensity of 1-6 V (VEF) were used to optimize electric field intensity under gradually increasing addition of TC (0.5, 2 and 10 mg L-1). Results showed that the application of electric fields (3 V and VEF) could improve TC tolerance and keep relatively high-efficiency nitrogen removal performance, especially at TC ≥ 2 mg L-1. Furthermore, applying electric fields contributed to mitigate irreversible inhibition and improve the stability of community structure. Underlying mechanism analysis indicated that the main mechanism of applying electric fields to mitigate inhibition relies on sludge structure strengthening. This study explored a novel strategy to reduce the inhibition of antibiotics on microbial denitrification and broaden the application of anammox in industrial water treatment.
Sujet(s)
Bioréacteurs , Dénitrification , Antibactériens , Azote/analyse , Oxydoréduction , Eaux d'égout , Tétracycline , Eaux uséesRÉSUMÉ
Sulfidated nanoscale valent iron in form of FeS/Fe (0) shell-core nanoparticle has the aptitude to be a promising remediation material toward reductive removal of metal oxyanions. However, disrupted contact between Fe (0) core and FeS shell by thick iron oxides limited its reactivity improvement, and its mechanism of electron transfer remains unveiled. In this study, a novel sulfidated nZVI core-shell particles (FeS/Fe (0)) was fabricated via a modified post sulfidation approach to achieve a more uniform coverage of FeS for aqueous Cr(VI) sequestration. SEM and STEM tests confirmed the formation of the core-shell FeS/Fe (0) structure with a more solid interaction between FeS layer and Fe (0) core. The highest Cr(VI) removal rate was offered at optimal S/Fe molar ratio of 1/25 that the most chelated Fe2+ was also observed. The improved performance was due to that FeS shell with greater electronegativity could significantly accelerate the corrosion of Fe (0), facilitate the electron transfer form Fe (0) core to FeS shell according to the electrochemical tests. Moreover, FeS shell provided a protective layer for Fe (0) core so as to alleviate its anoxic passivation in water that FeS/Fe (0) had a better longevity for Cr(VI) removal than nFe (0). Characterizations of STEM and XPS revealed that Cr(VI) was reduced to Cr(III) and evenly coprecipitated with surface Fe(II)/Fe(III).
Sujet(s)
Chromates , Polluants chimiques de l'eau , Chrome/analyse , Électrons , Composés du fer III , Composés du fer II , Polluants chimiques de l'eau/analyseRÉSUMÉ
Advanced oxidation processes (AOPs) based on peroxydisulfate (PDS) or peroxymonosulfate (PMS) activation have attracted much research attention in the last decade for the degradation of recalcitrant organic contaminants. Sulfate (SO4â¢-) and hydroxyl (â¢OH) radicals are most frequently generated from catalytic PDS/PMS decomposition by thermal, base, irradiation, transition metals and carbon materials. In addition, increasingly more recent studies have reported the involvement of singlet oxygen (1O2) during PDS/PMS-based AOPs. Typically, 1O2 can be produced either along with SO4â¢- and â¢OH or discovered as the dominant reactive oxygen species (ROSs) for pollutants degradation. This paper reviews recent advances in 1O2 generation during PDS/PMS activation. First, it introduces the basic chemistry of 1O2, its oxidation properties and detection methodologies. Furthermore, it elaborates different activation strategies/techniques, including homogeneous and heterogeneous systems, and discusses the possible reaction mechanisms to give an overview of the principle of 1O2 production by activating PDS/PMS. Moreover, although 1O2 has shown promising features such as high degradation selectivity and anti-interference capability, its production pathways and mechanisms remain controversial in the present literatures. Therefore, this study identifies the research gaps and proposes future perspectives in the aspects of novel catalysts and related mechanisms.
Sujet(s)
Peroxydes , Oxygène singulet , Radical hydroxyle , SulfatesRÉSUMÉ
The aim of this study is to identify and investigate levels of toxic heavy metals in PM2.5 fractioned road dust to better understand the associated inhalation risk and potential health impacts. To achieve this aim, concentrations of seven traffic generated heavy metals (Cu, Pb, Zn, Cd, Ni, Sb, and Cr) were determined in the PM2.5 fraction of road dust samples from four different locations (offices, residential, hospital, and school) in two cities (Karachi and Shikarpur) of Pakistan using ICP-MS. The average concentration values of heavy metals in Karachi were as follows: 332.9 mg/kg Cu, 426.6 mg/kg Pb, 4254.4 mg/kg Zn, 62.3 mg/kg Cd, 389.7 mg/kg Ni, 70.4 mg/kg Sb, 148.1 mg/kg Cr, whereas the average concentration values of heavy metals in Shikarpur were 245.8 mg/kg Cu, 538.4 mg/kg Pb, 8351.0 mg/kg Zn, 57.6 mg/kg Cd, 131.7 mg/kg Ni, 314.5 mg/kg Sb, 346.6 mg/kg Cr. The pollution level was assessed through two pollution indices enrichment factor (EF) and geoaccumulation index (Igeo). These indices showed moderate to extreme level pollution in studied areas of both cities. The health risk assessment through inhalation contact was conducted according to the United States Environmental Protection Agency's (USEPA) model for children and adults. Both non-cancerous and cancerous risks were characterised in the road dust samples for each location. As yet, there is not a single study on the concentrations of heavy metals in PM2.5 fractions of road dust in Karachi and Shikarpur, findings of this research will facilitate researchers for further investigations in current field.
Sujet(s)
Poussière/analyse , Surveillance de l'environnement/méthodes , Métaux lourds/analyse , Adulte , Enfant , Chine , Villes , Humains , Pakistan , Appréciation des risquesRÉSUMÉ
A green, high-efficiency mesoporous magnetic material with strong reusability and oxidation resistance, named graphene oxide immobilized nanoscale zero-valent iron (GO-nFe0), was prepared by a co-precipitation method. The structure, appearance, surface elements, and valence of GO-nFe0 were characterized via FESEM, TEM, FTIR, BET, XRD, and XPS. The characteristics and mechanism of Cr(â ¥) treatment in water using a weak magnetic field (WMF) coupled with GO-nFe0 (GO-nFe0/WMF) were studied. Batch experiments established that when the load mass ratio of GO to nFe0 was 1:10 under 20 mT weak magnetic field strength, the GO-nFe0/WMF system could completely remove the 10 mg·L-1 of Cr(â ¥) solution in 30 min, consistent with first-order dynamics. With a decrease in initial pH value and an increase in material dosage, the removal efficiency of Cr(â ¥) increased significantly by enhancing the release rate of Fe2+. ClO4- had no effect on the reaction, Cl- could encourage corrosion and promote the corrosion of nFe0 to release Fe2+, CO32- restrained the reaction through an increase in initial pH of the solution, and SO42- could promote the dissolution of the nFe0 surface passivation film to accelerate the reaction process. The GO-nFe0/WMF system can maintain high activity after five reuses and 30 days of exposure to air. XRD, XPS, and 1,10-phenanthroline shielding experiments proved that its great conductivity allowed GO to provide electron transfer sites to accelerate the transfer of electrons, and nFe0 could quickly release Fe2+. WMF generated a magnetic gradient force (FΔB) that pushed the paramagnetic Fe2+ ions in the diffusion boundary layer concentrated on the two poles of GO-nFe0, where the most magnetic intensity was present, to exposed active sites on both sides. The high removal rate ability of GO-nFe0 to release Fe2+ continuously was maintained.
RÉSUMÉ
The threat of antibiotics in the environment causing antibiotics resistance is a global health concern. Enzymes catalyze pollutant transformations, and how commercially available enzymes like horseradish peroxidase (HRP), with or without a redox mediator, may be used to degrade antibiotics in water treatment is of great interest. This work demonstrates tetracycline transformation by HRP, and how it is significantly enhanced by free radicals created from the mediator 2,2-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Water temperature and pH strongly inï¬uence the tetracycline removal rate due to their correlation with the enzyme activity, abundance and stability of ABTSâ¢+. Four transformation products were identified in the pure HRP system using a liquid chromatography tandem mass spectrometry hybrid quadrupole-orbitrap mass spectrometer system. Addition of 25 µmol L-1 ABTS not only accelerated the degradation of tetracycline, but also expanded the range of degradation pathways. Potential tetracycline transformation pathways are proposed based on these observations, which include a range of mechanisms such as hydroxylation, demethylation, dehydration, decarbonylation and secondary alcohol oxidation. Despite of decreased efficiency, the HRP/ABTS system was able to degrade tetracycline in a domestic wastewater treatment plant effluent matrix, which demonstrates the potential of the system to be utilized in wastewater treatment.
Sujet(s)
Horseradish peroxidase/composition chimique , Tétracycline/composition chimique , Polluants chimiques de l'eau/composition chimique , Antibactériens , Benzothiazoles , Catalyse , Chromatographie en phase liquide , Radicaux libres/composition chimique , Oxydoréduction , Acides sulfoniques , Eau , Purification de l'eau/méthodesRÉSUMÉ
The advanced oxidation processes (AOPs), especially sulphate radical (SO4â¢-)-based AOPs (SR-AOPs), have been considered more effective, selective, and prominent technologies for the removal of highly toxic emerging contaminants (ECs) due to wide operational pH range and relatively higher oxidation potential (2.5-3.1 V). Recently, biochar (BC)-based composite materials have been introduced in AOPs due to the dual benefits of adsorption and catalytic degradation, but the scientific review of BC-based catalysts for the generation of reactive oxygen species (ROSs) through radical- and non-radical-oriented routes for EC removal was rarely reported. The chemical treatments, such as acid/base treatment, chemical oxidation, surfactant incorporation, and coating and impregnation of minerals, were applied to make BC suitable as supporting materials (SMs) for the loading of Fenton catalysts to boost up peroxymonosulphate/persulphate/H2O2 activation to get ROSs including â¢OH, SO4â¢-, 1O2, and O2â¢- for targeted pollutant degradation. In this review, all the possible merits of BC-based catalysts including supportive, adsorptive, and catalytic role are summarised along with the possible route for the development prospects of BC properties. The limitations of SR-AOPs especially on production of non-desired oxyanions, as well as disinfection intermediates and their potential solutions, have been identified. Lastly, the knowledge gap and future-oriented research needs are highlighted.
Sujet(s)
Polluants chimiques de l'eau , Purification de l'eau , Adsorption , Charbon de bois , Peroxyde d'hydrogène , OxydoréductionRÉSUMÉ
This study presents a novel periodate oxidation system mediated by manganese oxides for the rapid removal of aqueous contaminants. The catalytic activation of periodate on manganese oxides was demonstrated as an efficient advanced oxidation system for degradation of sulfanilamide. The reactivity of manganese oxides with different Mn valence followed the order of MnO2>Mn3O4>Mn2O3, all of which showed extraordinary reusability during repeated activation of periodate. Sulfanilamide was rapidly degraded along with stoichiometric transformation of IO4- to IO3-, and both processes exhibited good linear correlations with the dosage of manganese oxides. While the degradation of sulfanilamide in the MnO2/IO4- system was accelerated at lower solution pH, it was only slightly affected by ionic strength, water anions and humic acid. In contrast to the homogeneous system of Mn2+/IO4-, sulfanilamide degradation was not influenced in oxic and anoxic environment. It was evidenced by quenching studies and EPR tests that both singlet oxygen (1O2) and iodate radicals (IO3â¢) were generated when the metastable Mn(IV)-O-IO3 interacted with sulfanilamide. The XPS spectra of Mn 2p and O 1s before and after reactions indicated that the catalytic activation of periodate on MnO2 was not in company with the redox cycling of Mn(IV) species.
Sujet(s)
Composés du manganèse , Oxydes , Oxydoréduction , Acide orthoperiodique , SulfanilamideRÉSUMÉ
H2O2 and persulfate (PDS) activated by iron are attracting much attention due to their strong oxidation capacity for the effective degradation of organic pollutants. However, they face problems such as requiring an acidic reaction pH and difficulty of Fe2+ regeneration. In this study, the simultaneous activation of H2O2 and persulfate by nanoscaled zero valent iron (nZVI) was investigated for the degradation of p-nitrophenol (PNP). The nZVI/H2O2/PDS oxidation system exhibited significantly higher reactivity toward PNP degradation than the systems with a single oxidant. A synergistic effect was explored between H2O2 and PDS during nZVI-mediated activation, and the molar ratio of H2O2/PDS was a key parameter in optimizing the performance of PNP degradation. The nZVI/H2O2/PDS system could function well in a wide pH range, and even 95% PNP was removed at an initial pH 10, thus markedly alleviating the pH limitations of Fenton-like processes. Both hydroxyl radicals and sulfate radicals could be identified during H2O2/PDS activation, in which H+ produced during PDS decomposition promoted H2O2 activation. The increase of oxidant concentration could significantly enhance the PNP degradation, while the presence of HCO3 - and HPO4 2- exerted great inhibition. Furthermore, five degradation intermediates of PNP were detected and its degradation pathways in the nZVI/H2O2/PDS system were presented. This study reveals that the simultaneous activation of H2O2 and PDS by nZVI is a promising advanced oxidation tool as an alternative to typical Fenton processes for recalcitrant pollutant removal.
RÉSUMÉ
A green, highly efficient, and porous copper-ferrite heterogeneous catalyst (Fe-Cu-400) with good magnetism was synthesized via a coprecipitation method. The catalysts were characterized using XRD, BET, FESEM, and EDS. The performance of Fe-Cu-400 as a catalyst was evaluated by activating peroxymonosulfate (PMS) for degradation of tetracycline (TC) in aqueous solution and investigating the influence of several water parameters. The Fe-Cu-400/PMS system showed a greater TC degradation ability, and the degradation rate of TC was enhanced with an increase in the PMS concentration and the initial pH of the coupled Fe-Cu-400/PMS system. Anions including H2PO4-, HCO3-, and Cl- promoted TC degradation, whereas NO3- showed a low inhibitory influence. In addition, Fe-Cu-400 exhibited excellent reusability towards activating PMS for TC degradation after five runs of tests. Possible mechanisms of the activation of PMS by Fe-Cu-400 and the main reactive species were proposed based on radical identification tests and XPS analysis. Furthermore, a potential degradation pathway was proposed that included hydrolysis and sequential removal of N-methyl, hydroxyl, and amine functional groups according to the results of LC-MS and TOC detections.
RÉSUMÉ
Mercury (Hg) contamination of wastewater streams as a result of anthropogenic activities is a great threat to living organisms due to its acute toxicity. Therefore, current research is focused on the development of effective remediation technologies to protect human health and the environment. In this study, a novel chemical modification route was applied for the multi-functionalization of biochar in order to make it more efficient and selective for Hg(ii) removal from aqueous solution. The amino-grafted modified biochar (AMBC) having multifunctional groups on its surface was successfully synthesized through the activation of excessively available carboxylic groups (-COOH) on pre-oxidized biochar (BC-COOH). The maximum Hg(ii) adsorption capacity for the optimized amino-BC2 sample was 14.1 mg g-1, which was almost twice as that for pristine biochar (BC, 7.1 mg g-1). SEM, FTIR, and XPS techniques were applied for the confirmation of chemically grafted amino groups as well as the presence of residual -COOH groups on the biochar surface. Based on the batch adsorption data, adsorption kinetics and isotherms as well as XPS results, it was concluded that the Hg(ii) removal mechanism was purely driven by chemisorption such as electrostatic interaction, surface complexation, ion exchange with no precipitation and crystalline material being adsorbed on the adsorbent surface. These research findings not only provide a suitable adsorbent for decontamination of Hg(ii) from aqueous solution but also offer a new route for the multi-functionalization of biochar in order to make environment-friendly and inexpensive adsorbents.
RÉSUMÉ
A heterogeneous manganese/magnetite/graphene oxide (Mn-MGO) hybrid catalyst was fabricated through the reduction of KMnO4 by ethylene glycol in the presence of magnetite/GO (MGO) particles. The Mn-MGO catalyst exhibited high efficacy and long-term stability in activating peroxymonosulfate (PMS) to generate sulfate radicals for the removal of bisphenol A (BPA) from water. The results of the batch experiments indicated that an increase in the catalyst dose and solution pH could enhance BPA degradation in the coupled Mn-MGO/PMS system. Regardless of the initial pH, the solution pH significantly dropped after the reaction, which was caused by catalytic PMS activation. The production of sulfate radicals and hydroxyl radicals was validated through radical quenching and electron paramagnetic resonances (EPR) tests. BPA degradation pathways were proposed on the basis of LC-MS and GC-MS analyses. Finally, a possible mechanism of catalytic PMS activation was proposed that involved electron transfer from MnO or Mn2O3 to PMS with the generation of sulfate radicals, protons and MnO2, as well as the simultaneous reduction of MnO2 by PMS.