RESUMO
Antibiotics with pseudo-persistence in water have been regarded as emerging pollutants, which have obvious biological toxicity even at trace levels. On account of high reactivity, heterogeneous catalytic ozonation has been widely applied to remove antibiotics. Among the heterogeneous catalysts, with well-developed pores and regulable surface defects, carbon-based materials can act as both adsorbents and catalysts. Metal cations, surface hydroxyl (-OH) groups and oxygen vacancies (OVs) serve as primary active sites in metal oxides. However, composites (perovskite, apatite, etc.) with special crystalline structure have more crystallographic planes and abundant active sites. The unsaturated bonds and aromatic rings which have dense structure of the electron cloud are more likely to be attacked by ozone (O3) directly. Sulfonamides (SAs) can be oxidized by O3 directly within a short time due to the structure of activated aromatic rings and double bonds. With the existence of catalysts, almost all antibiotics can attain fair removal effects. The presence of water matrix can greatly influence the removal rate of pollutants via changing the surface properties of catalysts, competing active sites with O3, etc. Correspondingly, the application of diverse heterogeneous catalysts was introduced in details, based on modification including metal/non-metal doping, surface modification and carrier composite. The degradation pathways of SAs, fluoroquinolones (FQNs), tetracyclines (TCs) and ß-lactams were summarized founded on the functional group structures. Furthermore, the effects of water matrix (pH, coexisting ions, organics) for catalytic ozonation were also debated. It is expected to proffer advanced guidance for researchers in catalytic ozonation of antibiotics.
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To investigate the effect of stalk type on the metallization degrees in FeCl3-derived magnetic biochar (MBC), MBC was synthesized via an impregnation-pyrolysis method using six different stalks. The Fe0 content in MBC significantly influenced its magnetic properties and ostensibly governed its catalytic capabilities. Analysis of the interaction between stalks and FeCl3 revealed that the variation in metallization degrees, resulting from FeCl2 decomposition (6.1%) and stalk-mediated reduction (20.7%), was directly responsible for the observed differences in MBC metallization. The presence of oxygen-containing functional groups and fixed carbon appeared to promote metallization in MBC induced by reduction. A series of statistical analyses indicated that the cellulose, lignin, and hemicellulose content of the stalks were key factors contributing to differences in MBC metallization degrees. Further exploration revealed that hemicellulose and cellulose were more effective than lignin in enhancing metallization through FeCl2 decomposition and reduction. Constructing stalk models demonstrated that the variance in the content of these three biomass components across the six stalk types could lead to differences in the metallization degree attributable to reduction and FeCl2 decomposition, thereby affecting the overall metallization degree of MBC. A prediction model for MBC metallization degree was developed based on these findings. Moreover, the elevated Si content in some stalks facilitated the formation of Fe2(SiO4), which subsequently impeded the reduction process. This study provides a theoretical foundation for the informed selection of stalk feedstocks in the production of FeCl3-derived MBC.
Assuntos
Carvão Vegetal , Cloretos , Compostos Férricos , Pirólise , Carvão Vegetal/química , Compostos Férricos/química , Cloretos/química , Lignina/química , Celulose/química , PolissacarídeosRESUMO
Nitrite, as an electron acceptor, plays a good role in denitrifying phosphorus removal (DPR); however, high nitrite concentration has adverse affects on sludge performance. We investigated the precise mechanisms of responses of sludge to high nitrite stress, including surface characteristics, intracellular and extracellular components, microbial and metabolic responses. When the nitrite stress reached 90 mg/L, the sludge settling performance was improved, but the activated sludge was aging. FTIR and XPS analysis revealed a significant increase in the hydrophobicity of the sludge, resulting in improve settling performance. However, the intracellular carbon sources synthesis was inhibited. In addition, the components in the tightly bound extracellular polymeric substances (TB-EPS) of sludge were significantly reduced and indicated the disturb of metabolism. Notably, Exiguobacterium emerged as a new genus when face high nitrite stress that could maintaining survival in hostile environments. Moreover, metabolomic analysis demonstrated strong biological response to nitrite stress further supported above results that include the inhibited of carbohydrate and amino acid metabolism. More importantly, some lipids (PS, PA, LysoPA, LysoPC and LysoPE) were significantly upregulated that related enhanced membrane lipid remodeling. The comprehensive analyses provide novel insights into the high nitrite stress responses mechanisms in activated sludge systems.
Assuntos
Desnitrificação , Metabolômica , Nitritos , Fósforo , Esgotos , Esgotos/microbiologia , Nitritos/metabolismo , Fósforo/metabolismo , Eliminação de Resíduos Líquidos/métodos , Microbiota/efeitos dos fármacos , Reatores Biológicos/microbiologiaRESUMO
Zinc oxide nanoparticles (ZnO NPs), as the highly efficient photocatalysts, could enhance the transformation of biogenic organic phosphorus (OP) to orthophosphate (PO43-) by photodegradation, accelerating eutrophication. Conversely, orthophosphate can also transform ZnO NPs and thus potentially alter their catalytic and chemical properties. Here, we investigated the transformation mechanisms of three biogenic OP compounds and ZnO NPs under ultraviolet light (UV) illumination: inositol phosphates (IHPs), nucleic acids (DNA), and aminoethylphosphonic acid (AEP). The physicochemical characteristics of the resulting products were systematically characterized. Results show that ZnO NPs accelerated the transformation of IHPs, DNA, and AEP to inorganic phosphorus with the direct photolysis efficiencies of 98.14, 87.68, and 51.76%, respectively. The main component of the precipitates remained ZnO NPs, and Zn3(PO4)2 was identified. Zinc phytate was determined in the ZnO NP-IHP system. 31P NMR and FTIR further confirmed that the aquatic phase contained orthophosphate. Photoproduced hydroxyl (·OH) and superoxide (·O2-) were proved to play a dominant role in the OP photomineralization. Furthermore, ZnO NPs significantly enhanced the intensity of ·OH and ·O2- compared to the OP and Zn2+ solution alone. This work explored the light-induced mineralization processes of OP with ZnO NPs indicating that nanophotocatalysts may play a positive role in transformation of OP species in aquatic environments to further contribute to eutrophication.
Assuntos
Nanopartículas Metálicas , Nanopartículas , Óxido de Zinco , Fósforo/química , Nanopartículas/química , Fosfatos , ZincoRESUMO
In recent years, iron mediated autotrophic denitrification has been a concern because it overcomes the absence of organic carbon and has been successfully used in denitrification for low C/N ratio wastewater. However, there is currently a lack of a more systematic summary of iron-based materials that can be used for denitrification, and no detailed overview about the mechanism of iron mediated autotrophic denitrification has been reported. In this study, the iron materials with different valence states that can be used for denitrification were summarized, and emphasized, as well as the mechanism in different interaction systems were emphasize. In addition, the contribution of various microorganisms in nitrate reduction were analyzed and the effects of operating conditions and water quality were evaluated. Finally, the challenges and shortcomings of the denitrification process were discussed aiming to find better practical engineering applications of iron-based denitrification.
Assuntos
Desnitrificação , Águas Residuárias , Ferro , Reatores Biológicos , Nitrogênio , NitratosRESUMO
Although lakes dominated by macrophytes are conducive to ecological balance, this balance is easily disrupted by excessive nutrients flowing into the lake. However, knowledge of whether excessive nutrients lead to different microbial environmental vulnerabilities in the lake sediment between macrophyte-dominated areas and macrophyte-free areas is a prerequisite for the implementation of targeted protection measures. In this study, we investigated bacterial communities in sediments using high-throughput sequencing of 16S rRNA genes. Our results showed that the sources of total nitrogen (TN) and organic matter (OM) were related to the macrophytes. The structure, drivers, and interspecific associations of bacterial community, which were more susceptible to increased changes in TN and OM, differed significantly between macrophyte-dominated areas and macrophyte-free areas. More precisely, the lake edge, where was occupied by macrophytes, had a higher proportion of deterministic phylogenetic turnover (88.89%) than other sites, as well as a wider ecological niche and a tighter network structure. Further, as the difference in TN increased, the main assembly processes in surface sediments changed from stochastic to deterministic. However, the majority of phyla from the lake edge showed a greater correlation with excessive nutrients, and the selection of the community by excessive nutrients was more obvious at the edge of the lake. In addition, our results demonstrated that the stability of the bacterial community in macrophyte-free areas is greater than in macrophyte-dominated areas, while an excessively high deterministic process ratio and nutrient (TN and OM) concentration significantly reduced bacterial community stability at macrophyte-dominated areas. Taken together, these results provide a better understanding of the effects of excessive nutrients derived from macrophytes on bacterial community patterns, and highlight the importance of avoiding the accumulation of TN and OM in macrophyte-dominated areas to enhance the sustainability of the ecosystem after restoration of lakes with macrophytes.
Assuntos
Lagos , Microbiota , Ecossistema , Sedimentos Geológicos/microbiologia , RNA Ribossômico 16S/genética , Filogenia , Nitrogênio , Bactérias/genética , Nutrientes , China , FósforoRESUMO
The emission standards for textile printing and dyeing wastewater are stricter due to serious environmental issues. A novel technology, hydrodynamic cavitation combined with ozone (HC + O3), has attracted wide attention in wastewater advanced treatment, whereas the contaminants removal mechanism and transformation of dissolved organic matter (DOM) were rarely reported. This study investigated the removal efficiency and mechanism of HC + O3. The maximum removal rates of UV254, chrominance, CODCr, and TOC were 64.99%, 91.90%, 32.30%, and 36.67% in 60 min, respectively, at the inlet pressure of 0.15 MPa and O3 dosage of 6.25 mmol/L. The synergetic coefficient of HC + O3 was 2.77. The removal of contaminants was the synergy of 1O2, ·OH and ·O2-, and high molecular weight and strong aromaticity organic matters were degraded effectively. The main components in DOM were tryptophan-like and tyrosine-like, which were effectively removed after HC + O3. Meanwhile, most DOM had decreased to low apparent relative molecular weight (LARMW) compounds. Additionally, the HC + O3 effluent can reach the emission standard in 60 min for 8.07 USD/m3. It can be concluded that HC + O3 is an effective technology for the advanced treatment of industrial wastewater. This study will provide suggestions for the engineering application of HC + O3.
Assuntos
Águas Residuárias , Purificação da Água , Corantes , Matéria Orgânica Dissolvida/química , Hidrodinâmica , Ozônio/química , Têxteis , Águas Residuárias/química , Purificação da Água/métodosRESUMO
The recycling of sewage is an economical option to solve the water resource pressure. However, to avoid health risks to humans, pathogens in sewage must be removed before reuse. In this study, a biological sand filter (BSF) was used to remove pathogen indicator Escherichia coli (E. coli) from sewage. The biolayer (schmutzdecke layer) formation process of BSFs, operation performance, factors affecting E. coli removal and microbial community structure were evaluated. The results of schmutzdecke layer culture showed that a large number of microorganisms were attached to the upper medium of BSFs. At the same time, the BSFs could reduce both conventional contaminants and E. coli. The E. coli removal experiments revealed that the removal rate of E. coli was about 96.1% at higher effective medium depth (50 cm), the removal rate was about 95% when set hydraulic loading rate (HLR) to 0.16 m3/m2/h and the removal efficiency reached 93.6% at lower influent bacteria concentration. Finally, the microbial community analysis indicated that different BSFs had similar microbial structure, and the microbial abundance in the schmutzdecke layer was higher than that in the bottom layer in the same BSFs. Besides, Biological action played a significant role in the removal of E. coli, including the bacteriolysis of Bdellovibrio and the competition between other bacteria and E. coli. In summary, BSF was a promising technology for removing E. coli from sewage.
Assuntos
Microbiota , Purificação da Água , Escherichia coli , Filtração/métodos , Humanos , Esgotos/química , Dióxido de Silício/química , Purificação da Água/métodosRESUMO
Many azo dyes are consumed in the textile and dyeing industry, which makes the wastewater recalcitrant and toxic to the aquatic environment. Dye degradation by the combination of hydrodynamic cavitation and ozone (HC + O3) has caused extensive interest. The degradation mechanism of the hybrid system needs further investigation. This study investigated the degradation of acid red 73 (AR73) by HC + O3. Meanwhile, the degradation pathways and mechanisms were present. The optimal operation parameters were: inlet pressure of 0.15 MPa, O3 dosage of 45 mg/min, initial dye concentration of 10 mg/L, and initial pH at 7.5. As a result, the decolorization rate, removal of UV254 and NH3-N were 100%, 71.28%, and 87.36% in 30 min, respectively. Humic acid and most of the co-existing anions (HCO3-, SO42-, Cl-, PO43-, NO3-) played a positive role in the degradation of AR73, while NO2- restrained. The reactive species of singlet oxygen (1O2), hydroxyl radicals (·OH) and super oxygen radicals (·O2-) showed synergism in the hybrid system, and the decolorization was attributed to the fracture of azo bonds by 1O2. Meanwhile, aromatic amines were generated and further degraded into small molecule compounds. The research certificated that the HC + O3 can be an effective technology for azo dye degradation.
Assuntos
Ozônio , Águas Residuárias , Compostos Azo/metabolismo , Corantes , Hidrodinâmica , Naftalenossulfonatos , Ozônio/química , Águas Residuárias/químicaRESUMO
In this paper, the material types were preferentially selected for different kinds of heavy metals, the effect of calcination temperatures on metal adsorption was investigated, and the adsorption mechanism was explored and summarized. The results show that the pseudo-first-order kinetic was better to fit the adsorption of heavy metals. The biomass type and pyrolysis temperature had an effect on the rate at which heavy metals were absorbed. Based on their adsorbed capacity, 350 °C pyrolyzed corn stalk char, 550 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, and 500 °C pyrolyzed wheat stalk char were shown to be the best adsorbents for Cr2O72-, Cd2+, Cu2+, Zn2+ and Pb2+, respectively. The largest adsorption rate were in the order of Cr6+ (Cr2O72-, 0.5380 /min) > Pb2+ (0.2276 /min) > Cd2+ (0.1354 /min) > Cu2+ (0.1273 /min) > Zn2+ (0.1000 /min), which might be positively related to the ion radius. Meanwhile, the yield of biomass decreased from 43.9% to 29.0% with the increase of pyrolysis temperature from 350 °C to 550 °C. In addition, the specific surface area and functional groups of the biochar, as well as the ionic radius and initial concentration of heavy metals affect the adsorption rate.
Assuntos
Cádmio , Metais Pesados , Adsorção , Carvão Vegetal , Íons , Chumbo , ÁguaRESUMO
Increased release of engineered nanoparticles (ENPs) from widely used commercial products has threatened environmental health and safety, particularly the repeated exposures to ENPs with relatively low concentration. Herein, we studied the response of Chlorella pyrenoidesa (C. pyrenoidesa) to single and repeated exposures to silver nanoparticles (AgNPs). Repeated exposures to AgNPs promoted chlorophyll a and carotenoid production, and increased silver accumulation, thus enhancing the risk of AgNPs entering the food chain. Notably, the extracellular polymeric substances (EPS) content of the 1-AgNPs and 3-AgNPs groups were dramatically increased by 119.1% and 151.5%, respectively. We found that C. pyrenoidesa cells exposed to AgNPs had several significant alterations in metabolic process and cellular transcription. Most of the genes and metabolites are altered in a dose-dependent manner. Compared with the control group, single exposure had more differential genes and metabolites than repeated exposures. 562, 1341, 4014, 227, 483, and 2409 unigenes were differentially expressed by 1-0.5-AgNPs, 1-5-AgNPs, 1-10-AgNPs, 3-0.5-AgNPs, 3-5-AgNPs, and 3-10-AgNPs treatment groups compared with the control. Metabolomic analyses revealed that AgNPs altered the levels of sugars and amino acids, suggesting that AgNPs reprogrammed carbon/nitrogen metabolism. The changes of genes related to carbohydrate and amino acid metabolism, such as citrate synthase (CS), isocitrate dehydrogenase (IDH1), and malate dehydrogenase (MDH), further supported these results. These findings elucidated the mechanism of biological responses to repeated exposures to AgNPs, providing a new perspective on the risk assessment of nanomaterials.
Assuntos
Chlorella , Nanopartículas Metálicas , Clorofila A , Metabolômica , Nanopartículas Metálicas/toxicidade , Prata/toxicidade , TranscriptomaRESUMO
This work investigated the effects of THP temperature (140-200 °C) and time (10-60 min) on the surface morphology, pyrolysis properties, and soluble compounds of dewatered sludge. Results indicate that higher temperature and longer pretreatment time considerably improve organics hydrolysis (the SCOD content increased 1.4-2.46 times, increasing 2.46 times at 200 °C). In addition, high temperature also improved the sludge pyrolysis efficiency (the highest at 200 °C), and reduced the harmful gas release, especially HCN. Moreover, the surface morphology of the sludge changed, the gap and floccules on the surface of the sludge increased. The carbohydrate content increased the highest; approximately 91.9% at 170 °C. THP promoted the decomposition of the nitrogen compounds in the sludge and facilitated their transition to a liquid phase. The total nitrogen and ammonia nitrogen content doubled, and the organic nitrogen content decreased by 50% with time increased from 10 to 60 min.
Assuntos
Amônia , Esgotos , Temperatura Alta , Hidrólise , TemperaturaRESUMO
Perfluorinated compounds (PFCs) contamination of soil has attracted global attention in recent years but influences of PFCs on microorganisms in the soil environment have not been fully described. In this study, the effects of perfluorooctane sulphonate (PFOS) and perfluoroctanoic acid (PFOA) on bacterial communities were determined by Illumina Miseq sequencing and Illumina Hiseq Xten. The stimulation of PFCs pollutants on soil bacterial richness and community diversity were observed. Sequencing information indicated that Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, Firmicutes, and Gemmatimonadetes were the dominant bacterial phyla. Two genera, Bacillus and Sphingomonas, exhibited adverse responses toward PFCs pollution. Carbohydrate-active enzymes (CAZy), Kyoto Encyclopedia of Genes and Genomes (KEGG) and NCBI databases were used to elucidate the proteins and function action of soil microbial to PFCs pollution. Pathways such as Carbohydrate metabolism, Global and overview maps and Membrane transport in the soil microbes were affected by PFCs stress. CAZy analysis revealed that glycosyl transferases (GTs) in PFCs-polluted soils showed more active, while glycoside hydrolases (GHs) were inhibited severely.
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Ácidos Alcanossulfônicos , Microbiota , Poluentes do Solo , Fluorocarbonos , Solo , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/toxicidadeRESUMO
Mine tailing dumps represent significant threats to ecological environments due to the presence of toxic substances. The present work investigated the relationship among microbial activity, the community, antibiotic resistance genes (ARGs) and trace metals in soil surrounding gold mine tailings. Using microbial metabolic activity and high-throughput sequencing analysis, we found the trace metals Cd and Hg could be main factors influencing the microbial community. According to bacterial co-occurrence pattern analysis, the effects of total cadmium and total mercury on bacterial diversity are potentially mediated by influencing bacteria community in the keystone module II. Additionally, most of metal-resistant bacteria belong to Actinobacteria and Proteobacteria, and the metal tolerance suggested to be linked with various functions including replication, recombination and repair, as well as inorganic ion transport and metabolism based on PICRUSt2 analysis. We also found that metals generated by mining activity may trigger the co-selection of antibiotic resistance in the phyla Actinobacteria and Proteobacteria due to co-resistance or cross resistance. Additionally, PLS-PM analysis revealed that metals could indirectly affect ARGs by influencing bacterial diversity in gold mining areas.
Assuntos
Metais Pesados , Microbiota , Poluentes do Solo , Antibacterianos/toxicidade , Resistência Microbiana a Medicamentos , Ouro , Metais Pesados/toxicidade , Mineração , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/toxicidadeRESUMO
With the rapid advancement of industrialization without effective supervision, industrial aquatic toxic metal (TM) emissions pose threats to human health in China. Due to differences in socioeconomic development, the regional disparity of industrial aquatic TM emissions is obvious nationwide. In this study, the human health impacts (HHIs) of industrial aquatic TM emissions (i.e., mercury (Hg), cadmium (Cd), hexavalent chromium (Cr(VI)), lead (Pb), and arsenic (As)) in the 31 provinces of China were evaluated based on the ReCiPe method, and the driving factors affecting HHIs from 2000 to 2015 were decomposed using the logarithmic mean Divisia index (LMDI) method. The results showed that the HHIs gradually decreased, with more than an 80% decrease from 2000 to 2015. The order of the TMs contributing to the national HHIs in 2015 was as follows: As (79.5%) > Cr(VI) (19.6%) > Hg (0.4%) > Pb (0.2%) = Cd (0.2%), and 21 (68%) provinces were dominated by industrial aquatic As emissions. Economic development is the major driving factor of the increase in HHIs, while the HHI strength and wastewater discharge intensity are the key driving factors causing reductions in the HHIs. Hunan, Inner Mongolia, Hubei, and Jiangxi accounted for approximately 55% of the total HHIs in 2015. Some suggestions for reducing HHIs based on the local realities of different provinces were put proposed considering two aspects: economic strategy and technical capability.
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Mercúrio , Metais Pesados , Poluentes da Água , China , Saúde Ambiental , Monitoramento Ambiental , Intoxicação por Metais Pesados , Humanos , Indústrias , Poluentes da Água/toxicidadeRESUMO
Dimethylamine-based pharmaceutical personal care products (DMA-based PPCPs) are a group of N-nitrosodimethylamine (NDMA) precursors. The acid dissociation constant (pKa) values of four DMA-based PPCPs were determined by potentiometric titration over the pH range of 3-11. The pKa values of ranitidine, nizatidine, doxylamine and carbinoxamine corresponding to the DMA moiety were 8.4, 6.8, 9.4 and 9.1, respectively. Competition reaction kinetics and pseudo-first-order reaction kinetics were used to determine the reaction rate constant (k) of the DMA-based PPCPs with O3, NaClO, ClO2 and KMnO4. Comparing the degradation rate constants of the four DMA-based PPCPs, the results of ClO2 oxidation were close, and for the other three oxidants, the order was kranitidine ≈ knizatidine > kdoxylamine ≈ kcarbinoxamine. Comparing the reaction rate of the four oxidants, for ranitidine and nizatidine, the order was kNaClO > kO3 > kKMnO4 > kClO2, and for doxylamine and carbinoxamine, the order was kO3 > kNaClO > kClO2 > kKMnO4.
Assuntos
Cosméticos/química , Dimetilnitrosamina/química , Oxidantes/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Cinética , Modelos Químicos , Oxirredução , Ozônio/química , Permanganato de Potássio/química , Hipoclorito de Sódio/químicaRESUMO
As an important causative factor of environmental accidents, natural disasters have recently received much attention for environmental risk assessment. Typhoons are one of the most frequent natural disasters in the northern Pacific Ocean and South China Sea and cause enormous damage to agriculture, daily livelihood, and industry. In this study, an environmental risk assessment for industrial enterprises is conducted when considering typhoon disasters. First, a Na-tech (natural hazard triggering technological disasters) environmental risk assessment index system with the aid of an analytic hierarchy process and fuzzy evaluation model (ERA-FAM) is developed to explore the major determinants related to risk level. The impact of typhoon disasters on environmental risk from chemical enterprises is discussed using a comparative analysis of risk levels with and without typhoon disaster scenarios. A chemical plant located in Zhejiang, China, is selected as a case study using this methodology. Three hypothetical scenarios are assumed, based on actual situations, to explore the impact of various factors on environmental risk. The results demonstrate that production factors and surrounding environmental conditions are the most sensitive factors for typhoon disasters, while emergency preparation is most important for reducing environmental risk. The influence of typhoons on environmental risk values is much higher for enterprises with imperfect management and vulnerable water risk receptors. Incorporating disaster management into environmental risk management will aid in developing strategies and policies for environmental risk mitigation and risk reduction practices.
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Tempestades Ciclônicas/prevenção & controle , Desastres/prevenção & controle , Monitoramento Ambiental/métodos , Indústrias , Gestão da Segurança/métodos , China , Lógica Fuzzy , Humanos , Modelos Teóricos , Oceano Pacífico , Medição de RiscoRESUMO
The molecular weight of dissolved organic matter (DOM) is one of the essential factors controlling the properties of metal complexes. A continuous ultrafiltration experiment was designed to study the properties of Cu complexes with different molecular weights in a river before and after eutrophication. The results showed that the concentration of DOM increased from 26.47 to 38.20 mg/L during the eutrophication process, however, DOM was still dominated by the small molecular weight fraction before and after eutrophication. The amount of Cu-DOM complexes increased with the increasing of molecular weight, however, the amounts of DOM-Cu complexes before eutrophication were higher than those after eutrophication. This is because DOM contained more -COOH and -OH before eutrophication and these functional groups are the active sites complexed with Cu.
Assuntos
Cobre/análise , Eutrofização , Compostos Orgânicos/análise , Rios/química , Poluentes Químicos da Água/análise , China , Peso Molecular , UltrafiltraçãoRESUMO
In this work, activated carbon (AC)-supported TiO2 containing 1.0% (mass percent) of 1.0 at.% (atomic percent) Fe(3+)-doped TiO2 nanotubes (Fe-TNTs) were successfully synthesized. The catalyst was used to effectively decompose toluene in water under O3/UV conditions, and some properties including the morphology, X-ray photoelectron spectroscopy, X-ray diffraction patterns, specific surface area and UV-visible diffuse reflectance spectroscopy were analyzed. A removal efficiency of 90.7% was achieved in the presence of fresh AC-supported Fe-TNTs calcined at 550 °C, with a pseudo-first-order rate constant of 0.038/min. The removal efficiency of toluene was reduced when the catalysts were repeatedly used, since the amount of adsorption sites of the supporting substrates decreased. However, even after AC-supported catalyst was used four times, the removal efficiency of toluene was still sufficient in water treatment. The enhanced photocatalytic activity of AC-supported Fe-TNTs was related to the synergistic effect of AC adsorption and Fe-TNTs photocatalytic ozonation. The water from a petrochemical company in China was used to obtain the removal efficiency of the pollutants, and the toluene and total organic carbon removal efficiencies were 69.9% and 58.3%, respectively.
Assuntos
Carbono/química , Ferro/química , Nanotubos/química , Titânio/química , Tolueno/química , Poluentes Químicos da Água/química , Adsorção , Catálise , Oxidantes/química , Oxirredução , Ozônio/química , Espectroscopia Fotoeletrônica , Titânio/efeitos da radiação , Raios Ultravioleta , Purificação da Água/métodos , Difração de Raios XRESUMO
Toluene is an extensively used reagent that could cause water pollution and endanger human health. In this work, an O3/UV/ion-doped TiO2 nanotubes process was investigated to obtain the optimum TiO2 nanotubes for effective toluene decomposition. Photocatalytic activity is found to be influenced by the doped-ion type by affecting the ionic radius, valence state, and configuration of the dopant. The calcination temperature and doping concentration, which change the weight fractions of the anatase phase (fA), the Brunauer-Emmett-Teller surface area (SBET), and the energy band gap (Eg) of the catalyst, also affect the photocatalytic activity. When TiO2 is doped with ions, SBET decreases and Eg becomes narrower. The photocatalytic activities of TiO2 for toluene removal increase after doping with Ag(+), Al(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), V(5+), and Zn(2+). Moreover, the 1.0% Fe(3+)-doped TiO2 nanotubes calcined at 550 °C have the highest catalytic activity, with a toluene removal efficiency of 70.7%.