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Biochar has proven effective in the remediation of excess nitrogen from soil and water. Excess nitrogen from agricultural fields ends up in aquatic systems and leads to reduced water quality and the proliferation of invasive species. This study aimed to assess the efficiency of chemically surface-modified biochar produced from invasive Pistia stratiotes L. for the adsorption of inorganic nitrogen (NH4+ and NO3-). Biochar structure was investigated using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and inductively coupled plasma mass spectrometry. The results from adsorption experiments indicate that NH4+ removal was optimal (0.8-1.3 mg N g-1) at near-neutral pH levels (6.0-7.5), while NO3- removal was optimal (0.4-0.8 mg N g-1) under acidic pH conditions (4.8-6.5) using the modified biochar. These findings highlight the significance of solution pH, biochar morphology, and surface chemistry in influencing the adsorption of NH4+ and NO3-. However, further studies are necessary to assess the potential oxidative transformation of NH4+ to NO3- by biochar, which might have contributed to the reduction in NH4+ in the aqueous phase.
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Malalignment in the lower limb structure occurs due to various causes. Accurately evaluating limb alignment in situations where malalignment needs correction is necessary. To create an automated support system to evaluate lower limb alignment by quantifying mechanical tibiofemoral angle (mTFA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) on full-length weight-bearing radiographs of both lower extremities. In this retrospective study, we analysed 404 radiographs from one hospital for algorithm development and testing and 30 radiographs from another hospital for external validation. The performance of segmentation algorithm was compared to that of manual segmentation using the dice similarity coefficient (DSC). The agreement of alignment parameters was assessed using the intraclass correlation coefficient (ICC) for internal and external validation. The time taken to load the data and measure the four alignment parameters was recorded. The segmentation algorithm demonstrated excellent agreement with human-annotated segmentation for all anatomical regions (average similarity: 89-97%). Internal validation yielded good to very good agreement for all the alignment parameters (ICC ranges: 0.7213-0.9865). Interobserver correlations between manual and automatic measurements in external validation were good to very good (ICC scores: 0.7126-0.9695). The computer-aided measurement was 3.44 times faster than was the manual measurement. Our deep learning-based automated measurement algorithm accurately quantified lower limb alignment from radiographs and was faster than manual measurement.
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Aprendizado Profundo , Osteoartrite do Joelho , Humanos , Perna (Membro) , Estudos Retrospectivos , Articulação do Joelho/diagnóstico por imagem , Tíbia , Osteoartrite do Joelho/etiologiaRESUMO
Globally, water scarcity in arid and semiarid regions has become one of the critical issues that hinder sustainable agriculture. Agriculture, being a major water consumer, presents several challenges that affect water availability. Hydrogels derived from polysaccharides seed gums are hydrophilic polymers capable of retaining substantial moisture in their three-dimensional network and releasing it back into the soil during drought conditions. Implementation of hydrogels in the agricultural sectors enhances soil health, plant growth, and crop yield. Furthermore, the soil permeability, density, structure, texture, and rate of evaporation and percolation of water are modified by hydrogel. In this review, hydrogels based on natural plant seed gum like guar, fenugreek, Tara and locust beans have been discussed in terms of their occurrence, properties, chemical structure, method of synthesis, and swelling behavior. The focus extends to recent applications of modified seed gum-based natural hydrogels in agriculture, serving as soil conditioners and facilitating nutrient delivery to growing plants. The swelling behavior and inherent structure of these hydrogels can help researchers unravel their maximum possibilities to promote sustainable agriculture and attenuate the obstacles propounded by our dynamic nature. The current review also examines market growth, prospects, and challenges of eco-friendly hydrogels in recent times.
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Hidrogéis , Polissacarídeos , Hidrogéis/química , Polissacarídeos/química , Agricultura , Solo/química , Sementes , Água/química , Gomas Vegetais/químicaRESUMO
Phenoxyacetic acid herbicides are widely used in agriculture for controlling weeds. These organic compounds are persistent and recalcitrant, often contaminating water and soil. Therefore, we studied five pristine biochars (BCs), and southern yellow pine (SYP) based self-activated carbon (SAC) for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. Among the tested adsorbents, SYP-SAC-15 demonstrated higher (>90%) 2,4-D removal from water. The SYP-SAC-15 was produced using a facile and green route where the biomass pyrolysis gases worked as activating agents creating a highly porous structure with a surface area of 1499.79 m2/g. Different adsorption kinetics and isotherm models were assessed for 2,4-D adsorption on SYP-SAC-15, where the data fitted best to pseudo-second order (R2 > 0.999) and Langmuir (R2 > 0.991) models, respectively. Consequently, the adsorption process was mainly dominated by the chemisorption mechanism with monolayer coverage of SYP-SAC-15 surface with 2,4-D molecules. At the optimum pH of 2, the maximum 2,4-D adsorption capacity of SYP-SAC-15 reached 471.70 mg/g. Furthermore, an increase in the water salinity demonstrated a positive influence on 2,4-D adsorption, whereas humic acid (HA) showed a negative impact on 2,4-D adsorption. The regeneration ability of SYP-SAC-15 showed excellent performance by retaining 71.09% adsorption capability at the seventh adsorption-desorption cycle. Based on the operating pH, surface area, spectroscopic data, kinetics, and isotherm modeling, the adsorption mechanism was speculated. The 2,4-D adsorption on SYP-SAC-15 was mainly governed by pore filling, electrostatic interactions, hydrogen bonding, hydrophobic and π-π interactions.
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Herbicidas , Poluentes Químicos da Água , Herbicidas/química , Carvão Vegetal/química , Adsorção , Água , Poluentes Químicos da Água/análise , Concentração de Íons de Hidrogênio , Ácido 2,4-Diclorofenoxiacético/química , CinéticaRESUMO
This research presents a novel and environmentally friendly approach for the synthesis of multifunctional nanobiocomposites for the efficient removal of toxic heavy metal and dye, as well as the disinfection of wastewater microorganisms. The nanobiocomposites (KAC-CS-AgNPs) were prepared by incorporating photochemically generated silver nanoparticles (AgNPs) within a chitosan (CS)-modified, high-surface-area activated carbon derived from kenaf (KAC), using a unique self-activation method. The even distribution of AgNPs was visible in the scanning electron microscopy images and a Fourier transform infra red study demonstrated major absorption peaks. The experimental results revealed that KA-CS-AgNPs exhibited exceptional adsorption efficiency for copper (Cu2+), lead (Pb2+), and Congo Red dye (CR), and showed potent antibacterial activity against Staphylococcus aureus and Escherichia coli. The maximum adsorption capacity (mg g-1) of KAC-CS-AgNPs was 71.5 for Cu2+, 72.3 for Pb2+, and 75.9 for CR, and the adsorption phenomena followed on the Freundlich and Langmuir isotherm models and the second-order kinetic model (R2 > 0.99). KAC-CS-AgNPs also exhibited excellent reusability of up to four consecutive cycles with minor losses in adsorption ability. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The bacterial inactivation tests demonstrated that KAC-CS-AgNPs had a strong bactericidal effect on both E. coli and S. aureus, with MIC calculated for E. coli and S. aureus as 32 µg mL-1 and 44 µg mL-1, respectively. The synthesized bioinspired nanocomposite KAC-CS-AgNPs could be an innovative solution for effective and sustainable wastewater treatment and has great potential for commercial applications.
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Quitosana , Nanopartículas Metálicas , Staphylococcus aureus , Prata/farmacologia , Prata/química , Nanopartículas Metálicas/química , Escherichia coli , Cobre/farmacologia , Chumbo , Antibacterianos/química , Quitosana/químicaRESUMO
Rapid population growth and the resultant pollution of freshwater resources have created a water stress condition reducing the availability of safe and affordable water. Guar gum, a biocompatible macromolecule obtained from the endosperm of the seeds of Cyamopsis tetragonolobus, is a fascinating raw material for multifunctional adsorbents. This review assembled the work conducted by various researchers over the past few decades and discussed the structure, properties, and different modifications methods employed to develop versatile guar gum-based adsorbent. The paper also summarized the recent progress of guar gum-based nanocomposites for the remediation of multiple hazardous substances such as organic dyes, toxic heavy metal ions, oil-water separation as well as inhibiting the growth of bacterial pathogens. Thus, the important contribution of guar gum composites to safeguard the water quality is highlighted which will overcome the limitations and streamline the future course of innovative research.
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Galactanos , Águas Residuárias , Galactanos/química , Gomas Vegetais/química , Mananas/química , BiopolímerosRESUMO
Angle measurement methods for measuring pes planus may lose consistency by errors between observers. If the feature points for angle measurement can be provided in advance with the algorithm developed through the deep learning method, it is thought that the error between the observers can be reduced. A total of 300 weightbearing lateral radiographs were used for the development of the deep learning-based algorithm, and a total of 95 radiographs were collected for the clinical validation test set. Meary angle (MA) and calcaneal pitch (CP) were selected as measurement methods and measured twice by three less-experienced physicians with the algorithm-based tool and twice without. The intra- and inter-observer agreements of MA and CP measures were assessed via intra-class correlation coefficient. In addition, verification of the improvement of measurement performance by the algorithm was performed. Interobserver agreements for MA and CP measurements with algorithm were more improved than without algorithm. As for agreement with reference standard, combining the results of all readers, both MA and CP with algorithm were greater than those without algorithm. The deep learning algorithm tool is expected to improve the reproducibility of radiographic measurements for pes planus, especially by improving inter-observer agreement.
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Aprendizado Profundo , Pé Chato , Humanos , Variações Dependentes do Observador , Radiografia , Reprodutibilidade dos Testes , Suporte de CargaRESUMO
A mix proportion of off-spec fly ash (FA)-added, seawater-mixed pervious concrete (SMPC) was optimized for compressive strength and permeability and then the optimized SMPC was tested for the rate and extent of aqueous phosphorus removal. An optimum mix proportion was obtained to attain the percentages (% wt.) of FA-to-binder at 15.0%, nano SiO2 (NS)-to-FA at 3.0%, liquid-to-binder at 0.338, and water reducer-to-binder at 0.18% from which a 7-day compressive strength of 14.0 MPa and a permeability of 5.5 mm/s were predicted. A long-term maximum compressive strength was measured to be ~16 MPa for both the optimized SMPC and the control ordinary pervious concrete (Control PC). The phosphorus removal was favorable for both the optimized SMPC and the Control PC based on the dimensionless Freundlich parameter (1/n). Both the optimized SMPC and Control PC had a first-order phosphorus removal constant of ~0.03 h-1. The optimized SMPC had a slightly lower capacity of phosphorus removal than the Control PC based on the Freundlich constant, Kf (mg1-1/n kg-1 L1/n): 15.72 for the optimized SMPC vs. 16.63 for Control. This study demonstrates a cleaner production and application of off-spec FA-added, seawater-mixed pervious concrete to simultaneously attain water, waste, and concrete sustainability.
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Pervious concrete mix was optimized for the maximum compressive strength and the desired permeability at 7 mm/s with varying percentages of water-to-binder (W/B), fly ash-to-binder (FA/B), nano-iron oxide-to-binder (NI/B) and water reducer-to-binder (WR/B). The mass ratio of coarse aggregates in sizes of 4.75-9.5 mm to the binder was fixed at 4:1. Waste FA used in the study was not compliant with a standard specification for use as a mineral admixture in concrete. One optimum pervious concrete (Opt A) targeting high volume FA utilization had a 28-day compressive strength of 22.8 MPa and a permeability of 5.6 mm/s with a mix design at 36% W/B, 35% FA/B, 6% NI/B and 1.2% WR/B. The other (Opt B) targeting a less use of admixtures had a 28-day compressive strength and a permeability of 21.4 MPa and 7.6 mm/s, respectively, at 32% W/B, 10% FA/B, 0.5% NI/B and 0.8% WR/B. During 10 loads at a 2-h contact time each, the Opt A and Opt B achieved the average fecal coliform removals of 72.4% and 77.9% and phosphorus removals of 49.8% and 40.5%, respectively. Therefore, non-compliant waste FA could be utilized for a cleaner production of pervious concrete possessing a greater structural strength and compatible hydrological property and pollution control potential, compared to the ordinary pervious concrete.
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Cinza de Carvão/química , Materiais de Construção/análise , Força Compressiva , Enterobacteriaceae/isolamento & purificação , Monitoramento Ambiental , Fezes/microbiologia , Resíduos Industriais/análise , Fósforo/isolamento & purificação , Poluentes do Solo/isolamento & purificação , Gerenciamento de Resíduos , Poluentes da Água/isolamento & purificação , Purificação da ÁguaRESUMO
Nanotechnology and its application is one of the rapidly developing sciences. As demand of fresh drinking water is increasing, nanotechnology can contribute noticeable development and improvement to water treatment process. Disinfection process is the last and most important step in water and wastewater treatment process. Some nanomaterials can be used as disinfectants due to their antimicrobial properties and reduce the possibility of harmful disinfection by-products (DBPs) formation during traditional disinfection process. A significant number of research efforts is done or going on to understand the mechanisms and enhance the efficiency of nanomaterials as antimicrobial agents, although it will take more time to understand the full potential of nanomaterials in this field. This review paper focuses on inactivation pathways of benign nanomaterials, their possible and probable application and limitations as disinfectants and future opportunities for their application in water cleaning processes.
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Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Desinfetantes/farmacologia , Desinfecção/métodos , Nanoestruturas/química , Purificação da Água/métodos , NanotecnologiaRESUMO
Waste materials containing Di-(2-ethylhexyl) phthalate (DEHP), a suspected endocrine disruptor and reasonably anticipated human carcinogen, are typically disposed of in landfills. Despite this, very few studies had been conducted to isolate and identify DEHP-degrading bacteria in landfill leachate. Therefore, this study was conducted to isolate and characterize bacteria in landfill leachate growing on DEHP as the sole carbon source and deteriorating PVC materials. Four strains LHM1, LHM2, LHM3 and LHM4, not previously reported as DEHP-degraders, were identified via 16S rRNA gene sequence. Gram-positive strains LHM1 and LHM2 had a greater than 97% similarity with Chryseomicrobium imtechense MW 10(T) and Lysinibacillus fusiformis NBRC 15717(T), respectively. Gram-negative strains LHM3 and LHM4 were related to Acinetobacter calcoaceticus DSM 30006(T) (90.7% similarity) and Stenotrophomonas pavanii ICB 89(T) (96.0% similarity), respectively. Phylogenetic analysis also corroborated these similarities of strains LHM1 and LHM2 to the corresponding bacteria species. Strains LHM2 and LHM4 grew faster than strains LHM1 and LHM3 in the enrichment where DEHP was the sole carbon source. When augmented to the reactors with PVC shower curtains containing DEHP, strains LHM1 and LHM2 developed greater optical densities in the solution phase and thicker biofilm on the surfaces of the shower curtains.
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Bactérias/classificação , Bactérias/isolamento & purificação , Dietilexilftalato/metabolismo , Disruptores Endócrinos/metabolismo , Cloreto de Polivinila/metabolismo , Poluentes Químicos da Água/metabolismo , Bactérias/genética , Bactérias/metabolismo , Biodegradação Ambiental , DNA Bacteriano/genética , Filogenia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Eliminação de Resíduos , Análise de Sequência de RNARESUMO
Newly isolated, not previously reported, di-(2-ethylhexyl) phthalate (DEHP)-degraders were augmented to assess their role in polyvinyl chloride (PVC) shower curtain deterioration and DEHP leaching. The biofilms that developed on the surfaces of the bioaugmented shower curtains with Gram-positive strains LHM1 and LHM2 were thicker than those of the biostimulated and Gram-negative strain LHM3-augmented shower curtains. The first derivative thermogravimetric (DTG) peaks of the bioaugmented shower curtains with the Gram-positive bacteria were observed at ~287°C, whereas the control and Gram-negative strain LHM3-augmented shower curtains were detected at ~283°C. This slight delay in the first DTG peak temperature is indicative of lower plasticizer concentrations in the shower curtains that were bioaugmented with Gram positive bacteria. Despite bioaugmentation with DEHP-degraders, aqueous solutions of the bioaugmentation reactors were not DEHP-free due probably to the presence of co-solutes that must have supported microbial growth. Generally, the bioaugmented reactors with the Gram-positive strains LHM1 and LHM2 had greater aqueous DEHP concentrations in the first-half (<3 wk) of the biodeterioration experiment than the biostimulated and strain LHM3-augmented reactors. Therefore, strains LHM1 and LHM2 may play an important role in DEHP leaching to the environment and PVC biodeterioration.
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This study was conducted to evaluate the effect of commercially available engineered iron oxide nanoparticles coated with a surfactant (ENP(Fe-surf)) on effluent water quality from a lab-scale sequencing batch reactor as a model secondary biological wastewater treatment. Results showed that ~8.7% of ENP(Fe-surf) applied were present in the effluent stream. The stable presence of ENP(Fe-surf) was confirmed by analyzing the mean particle diameter and iron concentration in the effluent. Consequently, aqueous ENP(Fe-surf) deteriorated the effluent water quality at a statistically significant level (p < 0.05) with respect to soluble chemical oxygen demand, turbidity, and apparent color. This implied that ENP(Fe-surf) would be introduced into environmental receptors through the treated effluent and could potentially impact them.
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Compostos Férricos/química , Tensoativos/química , Purificação da Água/métodos , Adsorção , Reatores Biológicos , Nanopartículas/química , Tamanho da Partícula , Purificação da Água/instrumentação , Qualidade da ÁguaRESUMO
In Fenton-driven oxidation treatment systems, reaction intermediates derived from parent compounds can play a significant role in the overall treatment process. Fenton-like reactions in the presence of toluene or benzene, involved a transformation mechanism that was highly efficient relative to the conventional Fenton-driven mechanism. A delay in hydrogen peroxide (H2O2) reaction occurred until the complete or near-complete transformation of toluene or benzene and involved the simultaneous reaction of dissolved oxygen. This highly efficient transformation mechanism is initiated by Fenton-like reactions, and therefore dependent on conventional Fenton-like parameters. Results indicated that several potential parameters and mechanisms did not play a significant role in the transformation mechanism including electron shuttles, Fe chelates, high valent oxo-iron complexes, anionic interferences in H2O2 reaction, and H2O2 formation. The Fenton-like initiation, formation, and propagation of a reaction intermediate species capable of transforming toluene, while simultaneously inhibiting H2O2 reaction is the most viable mechanism.
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Tolueno/química , Peróxido de Hidrogênio/química , Ferro/química , CinéticaRESUMO
Fenton-driven regeneration of methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) involves an Fe amendment step to increase the Fe content and to enhance the extent of MTBE oxidation and GAC regeneration. Four forms of iron (ferric sulfate, ferric chloride, ferric nitrate, ferrous sulfate) were amended separately to GAC. Following Fe amendment, MTBE was adsorbed to the GAC followed by multiple applications of H2O2. Fe retention in GAC was high (83.8-99.9%) and decreased in the following order, FeSO(4).7H2O>Fe2(SO4)(3).9H2O>Fe(NO3)(3).9H2O>FeCl3. A correlation was established between the post-sorption aqueous MTBE concentrations and Fe on the GAC for all forms of Fe investigated indicating that Fe amendment interfered with MTBE adsorption. However, the mass of MTBE adsorbed to the GAC was minimally affected by Fe loading. Relative to ferric iron amendments to GAC, ferrous iron amendment resulted in lower residual iron in solution, greater Fe immobilization in the GAC, and less interference with MTBE adsorption. MTBE oxidation was Fe limited and no clear trend was established between the counter-ion (SO4(2-), Cl-, NO3-) of the ferric Fe amended to GAC and H2O2 reaction, MTBE adsorption, or MTBE oxidation, suggesting these processes are anion independent.
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Carbono/química , Peróxido de Hidrogênio/química , Ferro/química , Éteres Metílicos/química , Adsorção , Poluição Ambiental/prevenção & controle , OxirreduçãoRESUMO
Fenton-driven oxidation of methyl tert-butyl ether (MTBE) (0.11-0.16mM) in batch reactors containing ferric iron (5mM) and hydrogen peroxide (H(2)O(2)) (6mM) (pH=3) was performed to investigate MTBE transformation mechanisms. Independent variables included the forms of iron (Fe) (Fe(2)(SO(4))(3).9H(2)O and Fe(NO(3))(3).9H(2)O), H(2)O(2) (6, 60mM), chloroform (CF) (0.2-2.4mM), isopropyl alcohol (IPA) (25, 50mM), and sulfate (7.5mM). MTBE, tert-butyl alcohol and acetone transformation were significantly greater when oxidation was carried out with Fe(NO(3))(3).9H(2)O than with Fe(2)(SO(4))(3).9H(2)O. Sulfate interfered in the formation of the ferro-peroxy intermediate species, inhibited H(2)O(2) reaction, hydroxyl radical (()OH) formation, and MTBE transformation. Transformation was faster and more complete at a higher [H(2)O(2)] (60mM), but resulted in lower oxidation efficiency which was attributed to ()OH scavenging by H(2)O(2). CF scavenging of the superoxide radical (()O(2)(-)) in the ferric nitrate system resulted in lower rates of ()O(2)(-) reduction of Fe(III) to Fe(II), ()OH production, and consequently lower rates of MTBE transformation. IPA, an excellent scavenger of ()OH, completely inhibited MTBE transformation in the ferric nitrate system indicating oxidation was predominantly by ()OH. ()OH scavenging by HSO(4)(-), formation of the sulfate radical (()SO(4)(-)), and oxidation of MTBE by ()SO(4)(-) was estimated to be negligible. The form of Fe (i.e., counter anion) selected for use in Fenton treatment systems impacts oxidative mechanisms, treatment efficiency, and post-oxidation treatment of residuals which may require additional handling and cost.
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Compostos Férricos/química , Sequestradores de Radicais Livres/química , Peróxido de Hidrogênio/metabolismo , Ferro/metabolismo , Éteres Metílicos/metabolismo , Nitratos/química , 2-Propanol/química , Peróxido de Hidrogênio/química , Radical Hidroxila/química , OxirreduçãoRESUMO
This study was conducted to assess the applicability of alkaline hydrolysis as an alternative ex situ technology for remediating 2,4,6-trinitrotoluene (TNT)-contaminated water. TNT reactivity had a strong dependence on the reaction pH (11-12) and initial TNT (5-25 mg L(-1)) in batch systems, resulting in pseudo first-order transformation rate, k ranging between 1.9 x 10(-3) and 9.3 x 10(-5) min(-1). In continuous flow stirred-tank reactor (CFSTR) systems with initial TNT of 1 mg L(-1), the highest 74% of TNT reduction was achieved at the reaction pH of 11.9 and 2-day hydraulic retention time under steady-state condition. Oxalate was produced as the major hydrolysate in the CFSTRs, indicating a ring cleavage during alkaline hydrolysis. It was also believed that TNT alkaline hydrolysis occurred through the production of color-forming intermediates via dimerization. It is concluded that alkaline hydrolysis can be an alternative treatment technology for remediation of TNT-contaminated water.
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Trinitrotolueno/química , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Álcalis/química , Cor , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Titulometria , Trinitrotolueno/metabolismo , Água/químicaRESUMO
Laboratory batch sorption experiments were conducted to investigate the impact of hydrogen peroxide (H2O2) pre-application on post-sorptive behavior of 2,4,6-trinitrotoluene (TNT) in different natural soils (average soil, high Fe soil, and high pH soil). After H2O2 application, the values of Freundlich coefficient Kf were increased by approximately 160% for the average and high pH soils and by approximately 120% for the high Fe soil, showing that the soils became more favorable for TNT sorption after H202 application. Nonlinearity in terms of the Freundlich exponent n was increased by approximately 40% for the average and high pH soils and by approximately 30% for the high Fe soil, showing greater sorption affinity of TNT for the oxidized soils at lower TNT concentrations and also implying greater TNT availability for transport at high concentrations. The increase in sorption extent for the H2O2-oxidized soils was presumably attributed to the oxygen-induced enhancement in the sorption capacity of the soils and the more dominant contribution of clay minerals to sorption. Therefore, enhanced sorption following H2O2 application may inhibit the subsequent formation of a TNT plume after either source zone remediation or plume remediation using H2O2 such as Fenton oxidation.
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Peróxido de Hidrogênio/química , Oxidantes/química , Poluentes do Solo , Trinitrotolueno/química , Adsorção , Silicatos de Alumínio , Carbono/análise , Argila , Concentração de Íons de Hidrogênio , Ferro , Oxirredução , Poluentes do Solo/análise , Fatores de Tempo , Trinitrotolueno/análise , Gerenciamento de Resíduos/métodosRESUMO
The hypothesis evaluated was that sorption/desorption experiments conducted under nonequilibrium conditions would sorb/desorb smaller amounts of polycyclic aromatic hydrocarbons (PAHs) in comparison to those conducted under an equilibrium condition. The magnitude of phenanthrene's (PHEs) sorption coefficient was approximately the same for both equilibrium and nonequilibrium conditions. However, when the initial PHE concentrations were varied, sorption nonequilibrium resulted in a 1.4-4.8% decrease in the actual PHE sorbed than those obtained under equilibrium conditions. Similarly, thermodynamic nonequilibrium led to a smaller pyrene (PYR) desorption. For example, when PYR was initially spiked at 10 mg/L, a total of 3.1 mg PYR/kg was desorbed under desorption nonequilibrium, whereas 3.6 mg/kg when equilibrium had been achieved. Mechanistic analysis of sorptive phenomena with respect to soil organic matter (SOM), clay minerals, and dissolved organic matter (DOM) demonstrated that both expandable clays and aliphatic SOM served as main sorbents for PAH sorption/desorption; that DOM was not a primary desorptive factor; and the interaction with clay minerals were stronger than that with SOM.