RESUMO
Developing cost-efficient wastewater treatment technologies for safe reuse is essential, especially in developing countries simultaneously facing water scarcity. This study developed and evaluated a hybrid constructed wetlands (CWs) approach, incorporating tidal flow (TF) operation and utilising local Jordanian zeolite as a wetland substrate for real pharmaceutical industry wastewater treatment. Over 273 days of continuous monitoring, the results revealed that the first-stage TFCWs filled with either raw or modified zeolite performed significantly higher reductions in Chemical Oxygen Demand (COD, 58 %-60 %), Total Nitrogen (TN, 32 %-37 %), and Phosphate (PO4, 46 %-64 %) compared to TFCWs filled with normal sand. Water quality further improved after the second stage of horizontal subsurface flow CWs treatment, achieving log removals of 1.09-2.47 for total coliform and 1.89-2.09 for E. coli. With influent pharmaceutical concentrations ranging from 275 to 2000 µg/L, the zeolite-filled hybrid CWs achieved complete removal (>98 %) for ciprofloxacin, ofloxacin, erythromycin, and enrofloxacin, moderate removal (43 %-81 %) for flumequine and lincomycin, and limited removal (<8 %) for carbamazepine and diclofenac. The overall accumulation of pharmaceuticals in plant tissue and substrate adsorption accounted for only 2.3 % and 4.3 %, respectively, of the total mass removal. Biodegradation of these pharmaceuticals (up to 61 %) through microbial-mediated processes or within plant tissues was identified as the key removal pathway. For both conventional pollutants and pharmaceuticals, modified zeolite wetland media could only slightly enhance treatment without a significant difference between the two treatment groups. The final effluent from all hybrid CWs complied with Jordanian treated industry wastewater reuse standards (category III), and systems filled with raw or modified zeolite achieved over 95 % of samples meeting the highest water reuse category I. This study provides evidence of using hybrid CWs technology as a nature-based solution to address water safety and scarcity challenges.
Assuntos
Indústria Farmacêutica , Eliminação de Resíduos Líquidos , Águas Residuárias , Poluentes Químicos da Água , Áreas Alagadas , Águas Residuárias/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Jordânia , Zeolitas/química , Análise da Demanda Biológica de OxigênioRESUMO
Antimony (Sb) contamination in certain areas caused by activities such as antimony mining and smelting poses significant risks to human health and ecosystems. In this study, a stable composite material consisting of natural zeolite-supported nanoscale zero-valent iron (Z-ZVI) was successfully prepared. The immobilization effect of Z-ZVI on Sb in contaminated soil was investigated. Experimental results showed that Z-ZVI exhibited superior performance compared to pure nano zero-valent iron (nZVI) in terms of stability, with a lower zeta potential (-25.16 mV) at a pH of 7 and a higher specific surface area (54.54 m2/g). It can be easily applied and dispersed in contaminated soils. Additionally, Z-ZVI demonstrated a more abundant porous structure. After 60 days of treatment with 3% Z-ZVI, the leaching concentration of Sb in the contaminated soil decreased from 1.32 mg/L to 0.31 mg/L (a reduction of 76%), and the concentration of available Sb species decreased from 19.84 mg/kg to 0.71 mg/kg, achieving a fixation efficiency of up to 90%. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis confirmed the effective immobilization of Sb in the soil through reduction of antimonate to antimonite, precipitation, and adsorption processes facilitated by Z-ZVI. Moreover, the addition of Z-ZVI effectively reduced the bioavailability of Sb in the contaminated soil, thereby mitigating its toxicity to earthworms. In conclusion, Z-ZVI can be utilized as a promising material for the safe remediation and antimony and other heavy metal-contaminated soils.
Assuntos
Antimônio , Ferro , Poluentes do Solo , Solo , Zeolitas , Antimônio/química , Poluentes do Solo/química , Zeolitas/química , Ferro/química , Solo/química , Recuperação e Remediação Ambiental/métodos , Adsorção , AnimaisRESUMO
In recent years, nanomaterials have gained widespread use in the biomedical field, with ZIF-8 and ZnO emerging as promising candidates due to their remarkable performance in osteogenesis, angiogenesis, and antimicrobial therapy. However, before advancing these nanomaterials for clinical applications, it is imperative to evaluate their biocompatibility. In particular, comparing nanomaterials with similar biomedical functions is crucial for identifying the most suitable nanomaterials for further development and market entry. Our study aimed to compare the biocompatibility of nano-ZIF-8 and nano-ZnO under the same conditions. We found that nano-ZIF-8 exhibited lower toxicity both in vitro and in vivo compared to nano-ZnO. To gain insights into the underlying mechanisms responsible for this difference, we conducted further experiments to investigate lysosome damage, mitochondrial change, and the occurrence of ferroptosis. Additionally, we performed transcriptome sequencing to analyze the expression of relevant genes, thereby providing robust validation for our findings. In summary, our study highlighted the importance of evaluating nanomaterials with similar biomedical effects. Through this comparative study, we have not only shed light on the superior biocompatibility of nano-ZIF-8 over nano-ZnO, but also contributed valuable insights and methodological references for future material screening endeavors. Ultimately, our study served as a stepping stone toward the development of safer and more effective nanomaterials for various biomedical applications.
Assuntos
Materiais Biocompatíveis , Óxido de Zinco , Óxido de Zinco/química , Óxido de Zinco/farmacologia , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Animais , Camundongos , Humanos , Zinco/química , Zinco/farmacologia , Ferroptose/efeitos dos fármacos , Teste de Materiais , Nanoestruturas/química , Nanoestruturas/toxicidade , Sobrevivência Celular/efeitos dos fármacos , Zeolitas/química , Zeolitas/farmacologiaRESUMO
This work focuses to the value added utilization of animal sewage sludge into gases, bio-oil and char using synthetic zeolite (ZSM-5 and Y-zeolite) and natural sourced (diatomite, kaolin, perlite) materials as catalysts. Pyrolysis was performed in a one-stage bench-scale reactor at temperatures of 400 and 600 °C. The catalyst was mixed with the raw material before the pyrolysis. Catalysts had a significant effect on the yield of products, because the amount of volatile products was higher in their presence, than without them. In case of kaolin, due to the structural transformation occurring between 500-600 °C, a significant increase in activity was observed in terms of pyrolysis reactions resulting in volatiles. The hydrogen content of the gas products increased significantly at a temperature of 600 °C and in thermo-catalysts pyrolysis. In the presence of catalysts, bio-oil had more favourable properties.
Assuntos
Óleos de Plantas , Polifenóis , Pirólise , Esgotos , Zeolitas , Zeolitas/química , Catálise , Esgotos/química , Biocombustíveis , Óxido de Alumínio/química , Caulim/química , Temperatura Alta , Dióxido de Silício/química , Temperatura , Carvão Vegetal/químicaRESUMO
Clinoptilolite based zeolite-geopolymer foams (abbreviated as CFs) were prepared from natural clinoptilolite and calcined clinoptilolite, using H2O2 solution as pore former through a straightforward process. Natural clinoptilolite and CFs are characterized by analytical techniques including optical microscope, XRF, FTIR, XRD, BET, MIP and SEM. The obtained CFs possesses micropores of zeolite and meso/macropores of geopolymer matrix. The porosities range from 66.7 to 69.5%. Clinoptilolite (partially dissolved) and impurity minerals (montmorillonite, illite and albite) contribute to the formation of geopolymer. CFs shows a good static sorption performance for toxic heavy metals at pH = 5 and sorption time of 24 h. Results show that the adsorption amount of CFs for Cr3+, Pb2+, Ni2+, Cu2+ and Cd2+ in the 50 mg/L working solutions are 6.21 mg/g, 6.11-6.13 mg/g, 5.92-6.07 mg/g, 5.53-5.93 mg/g and 5.44-5.79 mg/g, respectively. In addition, CFs could reach a high removal rate (Cr removal rate >80% and Cd > 60%) for different heavy metals after three cycles. The elimination order of toxic metals is Cr3+ > Pb2+ > Ni2+ > Cu2+ > Cd2+. The sequence is in accordance with Hard-Soft-Acid-Base principle, it is also related to the speciation and the ionic radii of the hydrated metal ions. This research provides a feasible approach for preparation of promising foams sorbent based on natural zeolite for wastewater management.
Assuntos
Metais Pesados , Poluentes Químicos da Água , Zeolitas , Humanos , Zeolitas/química , Cádmio/química , Peróxido de Hidrogênio , Chumbo , Metais Pesados/química , Adsorção , Íons , Poluentes Químicos da Água/químicaRESUMO
The application of small-pore chabazite-type SSZ-13 zeolites, key materials for the reduction of nitrogen oxides (NOx) in automotive exhausts and the selective conversion of methane, is limited by the use of expensive N,N,N-trimethyl-1-ammonium adamantine hydroxide (TMAdaOH) as an organic structure-directing agent (OSDA) during hydrothermal synthesis. Here, we report an economical and sustainable route for SSZ-13 synthesis by recycling and reusing the OSDA-containing waste liquids. The TMAdaOH concentration in waste liquids, determined by a bromocresol green colorimetric method, was found to be a key factor for SSZ-13 crystallization. The SSZ-13 zeolite synthesized under optimized conditions demonstrates similar physicochemical properties (surface area, porosity, crystallinity, Si/Al ratio, etc.) as that of the conventional synthetic approach. We then used the waste liquid-derived SSZ-13 as the parent zeolite to synthesize Cu ion-exchanged SSZ-13 (i.e., Cu-SSZ-13) for ammonia-mediated selective catalytic reduction of NOx (NH3-SCR) and observed a higher activity as well as better hydrothermal stability than Cu-SSZ-13 by conventional synthesis. In situ infrared and ultraviolet-visible spectroscopy investigations revealed that the superior NH3-SCR performance of waste liquid-derived Cu-SSZ-13 results from a higher density of Cu2+ sites coordinated to paired Al centers on the zeolite framework. The technoeconomic analysis highlights that recycling OSDA-containing waste liquids could reduce the raw material cost of SSZ-13 synthesis by 49.4% (mainly because of the higher utilization efficiency of TMAdaOH) and, meanwhile, the discharging of wastewater by 45.7%.
Assuntos
Zeolitas , Zeolitas/química , Oxirredução , Amônia/química , Óxidos de Nitrogênio/químicaRESUMO
This work explores the techno-economic aspects of landfill leachate treatment by an integrated scheme composed of microfiltration (MF), nanofiltration (NF), and zeolite application for carbon and nitrogen removal. In bench-scale experiments, MF and NF were investigated, and zeolite batch tests were carried out to determine optimum conditions. A preliminary economic analysis is presented for a 200 m3 d-1 full-scale treatment facility based on the data obtained from experimental tests and literature surveys. The maximum removals of 92%, 94%, and 79% for chemical oxygen demand (COD), absorbance at 254 nm, and ammonium nitrogen (NH4+-N) were achieved in bench experiments, respectively. It was possible to reach the local discharge standard for COD (200 mg L-1), but it was not possible to reach the Brazilian disposal requirement for NH4+-N (20 mg L-1). The total cost of the integrated MF + NF + zeolite system was estimated at 19.89 US$m-3. In this study, the costs of the zeolite application account for around 70% of the total costs of the integrated scheme. Membrane process integration was an adequate strategy for removing organic compounds at low operating costs; However, further NH4+-N depuration is needed to meet discharge requirements.
Assuntos
Poluentes Químicos da Água , Zeolitas , Análise da Demanda Biológica de Oxigênio , Carbono/análise , Nitrogênio/análise , Poluentes Químicos da Água/análise , Zeolitas/químicaRESUMO
Diazepam has been detected in water sources around the world affecting the quality of drinking water. Even in small quantities, recent studies have proven the negative effects of the drug on human body. Since traditional water and sewage treatment do not remove this type of contaminant, it became interesting to evaluate forms to remove them from water sources. A cheap and eco-friendly alternative to remove this drug from the water is through adsorption using the natural clinoptilolite zeolite as an adsorbent. This work goal was to study the characterizations of clinoptilolite, such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), and Fourier transform infrared spectroscopy (FTIR) and analyze the potential of this material as an adsorbent. Kinetic studies and isotherm analysis were performed in batch. The results showed the potential of the natural zeolite to remove the pollutant in an aqueous medium reaching a maximum adsorption capacity of 8.25 mg g-1. The adsorption process followed a pseudo-second-order kinetics indicating that the adsorption was based on a chemisorption process. The isotherms curves shown favorable adsorption and the Langmuir isotherm model fit the experimental data better.
Assuntos
Água Potável , Poluentes Químicos da Água , Zeolitas , Humanos , Zeolitas/química , Adsorção , Cinética , Diazepam , Esgotos , Poluentes Químicos da Água/análise , Termodinâmica , Espectroscopia de Infravermelho com Transformada de Fourier , Concentração de Íons de HidrogênioRESUMO
Zeolitic imidazole framework (ZIF) is an emerging class of metal organic frameworks exhibiting unique features such as crystalline nature with tunable pore size, large surface area and biocompatible nature. Exceptional thermal and chemical stabilities of ZIF-L make it a suitable candidate for biomedical applications. The present study has focused on the single step fabrication of catechin encapsulated ZIF-L and evaluation of its antibiofilm efficiency, larvicidal activity and dye degradation ability. The as- prepared CA@ZIF-L nanocomposite was characterized by spectroscopic and microscopic techniques. The results revealed that the CA@ZIF-L showed significant toxicity against mosquito larvae in a dose dependent manner with the IC50 63.43±1.25 µg/mL. CA@ZIF-L showed dose dependent reduction of biofilm formation in both ATCC and clinical MRSA strains. In addition, CA@ZIF-L exhibited excellent photocatalytic activity with around 92% degradation of methylene blue under direct sunlight. Overall, the present work highlights the possibility of employing the multifunctional CA@ZIF-L nanocomposite as a suitable material for biomedical and photocatalytic applications.
Assuntos
Biofilmes/efeitos dos fármacos , Catequina/química , Estruturas Metalorgânicas/química , Nanocompostos/toxicidade , Zeolitas/química , Animais , Catálise , Culicidae/efeitos dos fármacos , Culicidae/crescimento & desenvolvimento , Imidazóis/química , Larva/efeitos dos fármacos , Luz , Staphylococcus aureus Resistente à Meticilina/fisiologia , Azul de Metileno/química , Nanocompostos/química , Tamanho da Partícula , Fotólise/efeitos da radiaçãoRESUMO
The use of rare earth elements is a growing trend in diverse industrial activities, leading to the need for eco-friendly approaches to their efficient recovery and reuse. The aim of this work is the development of an environmentally friendly and competitive technology for the recovery of those elements from wastewater. Kinetic and equilibria batch assays were performed with zeolite, with and without bacterial biofilm, to entrap rare earth ions from aqueous solution. Continuous assays were also performed in column setups. Over 90% removal of lanthanum and cerium was achieved using zeolite as sorbent, with and without biofilm, decreasing to 70% and 80%, respectively, when suspended Bacillus cereus was used. Desorption from the zeolite reached over 60%, regardless of the tested conditions. When in continuous flow in columns, the removal yield was similar for all of the rare earth elements tested. Lanthanum and cerium were the elements most easily removed by all tested sorbents when tested in single- or multi-solute solutions, in batch and column assays. Rare earth removal from wastewater in open setups is possible, as well as their recovery by desorption processes, allowing a continuous mode of operation.
Assuntos
Bacillus cereus/crescimento & desenvolvimento , Metais Terras Raras/isolamento & purificação , Águas Residuárias/análise , Zeolitas/química , Adsorção , Cério/isolamento & purificação , Resíduos Industriais , Cinética , Lantânio/isolamento & purificação , Poluentes Químicos da Água , Purificação da ÁguaRESUMO
The objective of the present study was firstly acute toxicity bioassay of arsenic on common carp (Cyprinus carpio) and then the development of natural sorbent beds (clinoptilolite and pumice) to reduce bioconcentration of arsenic in muscle tissue were considered in comparative evaluation. In this regard, the acute toxicity of arsenic on juvenile fish was assessed according to the OECD guideline (No. 203). Moreover, the efficacy of clinoptilolite and pumice as natural sorbents was assessed to reduce bioconcentration of arsenic in the fish muscle tissue during a 21 day by response surface methodology (RSM) under central composite design (CCD). The most important point of this study was to evaluate the interactions between independent variables (clinoptilolite and pumice as sorbents and arsenic as pollutant) and arsenic bioconcentration in fish muscle tissue as a dependent variable (response). In these regards, a total of 24 sets of experiments (12 sets for clinoptilolite and pumice separately) were designed by the software to achieve the best adsorption conditions. According to the arsenic toxicity test, results as estimated by Probit method, the 96â¯h LC50 was 9.48⯱â¯1.01â¯mg/L. Analysis of variance (ANOVA) which was applied to modeling and optimization of response revealed that the predicted values were in relatively good agreement with the experimental data. Additionally, the obtained value for model desirability by clinoptilolite and pumice were 0.932 and 0.958, respectively. Overall, the obtained results indicate that both adsorbents reduced the bioconcentration of As (V) in the muscle tissue of common carp, but clinoptilolite was more effective.
Assuntos
Arseniatos/toxicidade , Carpas/metabolismo , Poluentes Químicos da Água/toxicidade , Poluição da Água/prevenção & controle , Zeolitas/química , Adsorção , Animais , Arseniatos/metabolismo , Dose Letal Mediana , Músculos/metabolismo , Testes de Toxicidade , Poluentes Químicos da Água/metabolismoRESUMO
Adsorption of 5-Fluorouracil and Thioguanine drugs into three Zeolitic Imidazolate Frameworks (ZIFs), (ZIF-1, ZIF-3 and ZIF-6) were studied in detail through Monte Carlo (MC) and Molecular Dynamics (MD) simulations. GCMC results showed that the adsorption capacity of 5-Fluorouracil on the studied ZIFs is slightly higher than those of Thioguanine. The order of adsorption capacities of the two studied drugs on ZIFs structures is ZIF-6â¯>â¯ZIF-3â¯>â¯ZIF-1, where ZIF-6 shows a higher adsorption capacity for both drugs than the two other ZIFs due to its larger pore volume. Also, the isosteric heats of adsorption of both drugs in ZIF-6 are greater than those of ZIF-3 and ZIF-1. The preferential adsorption sites of 5-Fluorouracil and Thioguanine in ZIF-1 and ZIF-6 are surrounding the cage II (4-membered Zn-imidazolate ring). Finally, the microscopic details of the adsorbates in the studied ZIFs are investigated through radial distribution functions (RDFs) for characteristic atoms of drugs and ZIFs. It was found that the studied drugs preferentially adsorb in the vicinity of the metal site of ZIFs.
Assuntos
Fluoruracila/química , Tioguanina/química , Zeolitas/química , Adsorção , Imidazóis/química , Simulação de Dinâmica Molecular , Método de Monte CarloRESUMO
Food waste management (FWM) is considered to be an extremely important social issue besides an environmental one. Worldwide, it is estimated that 1.3 billion t/year of foods are disposed of in landfills (including edible and inedible foods). Moreover, FAO indicated that if food waste (FW) was a country, it could be the 3rd biggest CO2 producer after China and the USA with more than 3.5-4.2 billion of t equivalence CO2. Each citizen in the entire EU produces approximately 179 kg/year FW equal more or less with 600 /year. This paper focuses on the concept of circular economy (CE) and how can we optimize and improve the production of biogas from UASB-R (upflow anaerobic sludge blanket reactor) using FW and natural minerals (clinoptilolite). The study was elaborated through laboratory scale experiments using different mixtures of FW, liquid waste from slaughterhouse (LWS), and natural clinoptilolite (Cli). The amount of biogas produced and the methane content of biogas were used as indicators in order to monitor and asses the performance of the anaerobic digester. The results of the present study were encouraging towards the use of FW in existing anaerobic treatment plants, suggesting selective collection at source of FW, diversion from landfills, and use as a secondary resource for energy recovery through a transition to a CE. The results indicate that the use of FW with zeolite duplicates the production of CH4 within the same days of production compared with the control sample.
Assuntos
Metano/análise , Gerenciamento de Resíduos , Zeolitas/química , Anaerobiose , Biocombustíveis , Reatores Biológicos , China , Alimentos , Metano/química , EsgotosRESUMO
Zeolites are important materials for research and industrial applications. Mesopores are often introduced by desilication but other properties are also affected, making its optimization difficult. In this work, we demonstrate that Perturbation Theory and Machine Learning can be combined in a PTML multioutput model describing the effects of desilication. The PTML model achieves a notable accuracy ( R2 = 0.98) in the external validation and can be useful for the rational design of novel materials.
Assuntos
Aprendizado de Máquina , Silício/química , Zeolitas/química , Simulação por Computador , Modelos Moleculares , Método de Monte Carlo , Propriedades de SuperfícieRESUMO
Unlike the well-known simplified molecular input-line entry system (SMILES), the so-called quasi-SMILES contains information related to physicochemical and biochemical conditions by a special additional symbols (codes), each standing for different conditions (time exposure, concentration, type of cell, etc.). Thus, quasi-SMILES can be used to build up models for cytotoxicity of functionalized nanozeolites using a mathematical function of eclectic information. These calculations were done with the Monte Carlo CORAL software. The statistical quality of models based on quasi-SMILES was usually considerably better than the statistical quality of models based on traditional SMILES.
Assuntos
Citotoxinas/química , Relação Quantitativa Estrutura-Atividade , Zeolitas/química , Modelos Moleculares , Método de Monte Carlo , Nanopartículas/química , SoftwareRESUMO
Grey water reclamation is a sustainable solution for managing water shortages. However, grey water contains high levels of detergents, particularly surfactants, which alongside other chemical constituents can pose a serious risk to human health and the environment. Biological treatments are not effective in the treatment of grey water since the detergents inhibit the activities of microorganisms. Chemical treatment options have an impact on public perception and could be cost prohibitive for domestic and small scale reuse applications. In this paper, we review the characterization of the constituents of grey water and the application of various low cost sustainable materials such as zeolite, activated carbon, mussel shells, tyre granules, fly ash, ground granulated blast furnace slag and silica gel for the treatment and removal of detergent characteristics.
Assuntos
Cinza de Carvão/química , Águas Residuárias/química , Poluentes Químicos da Água/química , Purificação da Água/economia , Purificação da Água/métodos , Zeolitas/químicaRESUMO
Palm oil fuel ash (POFA) is an agricultural waste which was employed in this study to produce novel adsorptive ceramic hollow fibre membranes. The membranes were fabricated using phase inversion-based extrusion technique and sintered at 1150 °C. The membranes were then evaluated on their ability to adsorb cadmium (Cd(II)). These membranes were characterised using (nitrogen) N2 adsorption-desorption analysis, field emission scanning electron microscopy-energy-dispersive X-ray spectroscopy (FESEM-EDX) mapping, X-ray fluorescence (XRF), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses while adsorptivity activity was examined by batch adsorption studies. The adsorption test results show that the quantity of hollow fibre used and water pH level significantly affected the adsorption performance with the 3-fibre membrane yielding 96.4% Cd(II) removal in 30 min equilibrium time at pH 7. These results are comparable to those reported by other studies, and hence demonstrate a promising alternative of low-cost hollow fibre adsorbent membrane. Graphical abstract Figure of FESEM image of the hollow fibre, proposed mechanism and the graph of percentage removal of Cd(II) using POFA.
Assuntos
Cádmio/química , Membranas Artificiais , Óleo de Palmeira/química , Poluentes Químicos da Água/química , Purificação da Água/instrumentação , Adsorção , Cádmio/isolamento & purificação , Estudos de Viabilidade , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Espectrometria por Raios X , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/economia , Purificação da Água/métodos , Difração de Raios X , Zeolitas/químicaRESUMO
Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n-alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n-butane was observed, followed by an increase for n-pentane, and another decrease for n-hexane. This observation was confirmed by uptake measurements with n-butane/n-pentane mixtures, which yield faster uptake of n-pentane. Further evidence is provided by the observation of overshooting effects, i.e., by transient n-pentane concentrations exceeding the (eventually attained) equilibrium value. Accompanying grand canonical Monte Carlo simulations reveal, for the larger n-alkanes, significant differences between the adsorbed and gas phase molecular configurations, indicating strong confinement effects within ZIF-4, which, with increasing chain length, may be expected to give rise to configurational shifts facilitating molecular propagation at particular chain lengths.
Assuntos
Alcanos/química , Estruturas Metalorgânicas/química , Zeolitas/química , Estrutura Molecular , Método de Monte CarloRESUMO
This paper shows the effect of organic shock loads (OSLs) on the anaerobic digestion (AD) of synthetic swine wastewater using an expanded granular sludge bed (EGSB) reactor modified with zeolite. Two reactors (R1 and R2), each with an effective volume of 3.04 L, were operated for 180 days at a controlled temperature of 30 °C and hydraulic retention time of 12 h. In the case of R2, 120 g of zeolite was added. The reactors were operated with an up-flow velocity of 6 m/h. The evolution of pH, total Kjeldahl nitrogen, chemical oxygen demand (COD) and volatile fatty acids (VFAs) was monitored during the AD process with OSL and increases in the organic loading rate (OLR). In addition, the microbial composition and changes in the structure of the bacterial and archaeal communities were assessed. The principal results demonstrate that the presence of zeolite in an EGSB reactor provides a more stable process at higher OLRs and after applying OSL, based on both COD and VFA accumulation, which presented with significant differences compared to the control. Denaturing gradient gel electrophoresis band profiles indicated differences in the populations of Bacteria and Archaea between the R1 and R2 reactors, attributed to the presence of zeolite.
Assuntos
Reatores Biológicos/microbiologia , Modelos Teóricos , Esgotos/química , Águas Residuárias/análise , Purificação da Água/métodos , Zeolitas/química , Anaerobiose , Animais , Análise da Demanda Biológica de Oxigênio , Fazendas , SuínosRESUMO
Application of immobilizing agents may efficiently reduce the bioavailability of nickel (Ni) in the soil. Here we report the effect of biochar (BC), gravel sludge (GS) and zeolite (ZE) as a sole treatment and their combinations on the bioavailability of Ni after their application into a Ni-polluted soil. The bioavailability of Ni after the application of immobilizing agents was assessed through an indicator plant (red clover) and chemical indicators of bioavailability like soil water extract (SWE), DTPA and Ca(NO3)2 extracts. Additionally, the effects of Ni bioavailability and immobilizing agents on the growth, physiological and biochemical attributes of red clover were also observed. Application of ZE significantly reduced Ni concentrations in all chemical extracts compared to rest of the treatments. Similarly, the combined application of BC and ZE (BC+ ZE) significantly reduced Ni concentrations, reactive oxygen species (ROS) whereas, significant enhancement in the growth, physiological and biochemical attributes along with an improvement in antioxidant defence machinery of red clover plant, compared to rest of the treatments, were observed. Furthermore, BC+ ZE treatment significantly reduced bioconcentration factor (BCF) and bioaccumulation factor (BAF) of Ni in red clover, compared to rest of the treatments. The Ni concentrations in red clover leaves individually reflected a good correlation with Ni concentrations in the extracts (SWE at R2=0.79, DTPA extract at R2=0.84 and Ca(NO3)2 extracts at R2=0.86). Our results indicate that combined application of ZE and BC can significantly reduce the Ni bioavailability in the soil while in parallel improve the antioxidant defence mechanism in plants.