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1.
An Acad Bras Cienc ; 93(2): e20190144, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33852669

RESUMO

The Chapala Lake is one of the most polluted lakes in Mexico, due to the in flow of effluents from several industrial plants, the lake accumulates pollutants such as chromium(VI) which is considered important for aquatic ecosystem. This study aimed was to evaluate the ability to decrease the concentration of chromium (VI) by Lysinibacillus macroides 2(1B)104A, isolated from sediments of the Chapala Lake. The strain was identified through 16S rRNA sequencing and phylogenetic analysis. Results showed that this strain grows in concentrations of 50, 100, 200 and 300 mgL-1 Cr(VI), in pH ranging 6 to 7, showing 79.508% reduction in concentration 50 mgL-1, determining that the reduction occurs extracellularly. Likewise, it was observed that Lysinibacillus macroides reduced the concentration of Cr(IV) in the broth, it was not observed that the bacteria could sequester Cr(VI) in the membrane or intracellularly. However, it reduced the concentration of Cr(VI) in the broth. Lysinibacillus macroides 2(1B)104A isolate showed having the ability that decrease the concentration of Cr(VI), which makes it a viable options for bioremediation of water polluted with this metal.


Assuntos
Ecossistema , Lagos , Bacillaceae , Cromo/análise , Concentração de Íons de Hidrogênio , México , Oxirredução , Filogenia , RNA Ribossômico 16S/genética
2.
J Environ Manage ; 287: 112279, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33706095

RESUMO

Environment pollution is at its peak and is creating havoc for living beings. Industrial wastes containing toxic pollutants have contributed to a great extent in this disastrous environment pollution. Chromium (Cr3+/Cr6+) is highly toxic and one of the most common environmental pollutants because of its extensive use in industries especially tanneries. Lack of efficient treatment methods has resulted in extensive chromium pollution. Bioremediation of chromium using bacteria is very thoughtful due to its eco-friendly and cost-effective outcome. Bacteria possess numerous mechanisms such as biosorption, reduction, efflux or bioaccumulation, naturally or acquired to counter the toxicity of chromium. This review focuses on the bacterial responses against chromium toxicity and scope for their application in bioremediation. The differences and similarities between Gram negative and positive bacteria against chromium are also highlighted. Further, the knowledge gap and future prospects are also discussed in order to fill these gaps and overcome the problem associated with real-time applicability of bacterial bioremediation.


Assuntos
Cromo , Poluentes Ambientais , Bactérias/genética , Biodegradação Ambiental , Cromo/análise , Cromo/toxicidade , Poluentes Ambientais/análise , Resíduos Industriais
3.
Sci Total Environ ; 772: 145495, 2021 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-33770851

RESUMO

A large gap exists between laboratory findings and successful implementation of bioremediation technologies for the treatment of chromium (Cr)-contaminated sites. This work conducted the enhanced bioremediation of Cr(VI) in situ via the addition of organic carbon (ethanol) coupled with a dynamic groundwater recirculation (DGR)-based system in a field-scale study. The DGR system was applied to successfully (1) remove Cr(VI) from groundwater via enhanced flushing by the recirculation system and (2) deliver the biostimulant to the heterogeneous subsurface environment, including a sand/cobble aquifer and a fractured bedrock aquifer. The results showed that the combined extraction and bioreduction of Cr(VI) were able to reduce Cr(VI) concentrations from 1000 to 2000 mg/L to below the clean-up goal of 0.1 mg/L within the operation period of 52 days. The effectiveness of Cr(VI) bioremediation and the relationship between microbial communities and geochemical parameters were evaluated. Multiple-line of evidence demonstrated that the introduction of ethanol significantly stimulated a variety of bacteria, including those responsible for denitrification, sulfate reduction and reduction of Cr(VI), which contributed to the establishment of reducing conditions in both aquifers. Cr(VI) was removed from groundwater via combined mechanisms of physical removal through the DGR system and the bioreduction of Cr(VI) followed by precipitation. In particular, it was found competitive growth among Cr(VI)-reducing bacteria (such as the enrichment of Geobacter, along with the reduced relative abundance of Acinetobacter and Pseudomonas) was induced by ethanol injection. Furthermore, Cr(VI), total organic carbon, NO2-, and SO42- played important roles in shaping the composition of the microbial community and its functions.


Assuntos
Água Subterrânea , Biodegradação Ambiental , Cromo/análise , Oxirredução
4.
Huan Jing Ke Xue ; 42(3): 1197-1204, 2021 Mar 08.
Artigo em Chinês | MEDLINE | ID: mdl-33742917

RESUMO

With the rapid development of industry, chromium (Cr) has become one of the main soil heavy metal pollutants in China, seriously affecting the soil ecological environment and health of residents. In this study, contaminated soil samples were taken around the tannery sludge yard area in Heibei Province. The Illumina MiSeq high-throughput sequencing technology was employed to analyze the structure and assembly processes of soil bacterial communities at different pollution levels. Results showed that chromium pollution significantly influences soil properties and soil bacterial communities. The composition and structure of bacterial communities were significantly shifted at different pollution levels. Furthermore, the α diversity of bacterial communities may decrease with relatively high concentrations of chromium. Bacterial communities in chromium polluted soil can be divided into 55 phyla, where Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, and Firmicutes are the dominant phyla (relative abundance>5%). Moreover, the soil bacterial communities were dominated by the deterministic assembly process (homogeneous selection) and the stochastic ratios decreased with increases in the concentration of chromium in soil. The total concentration of chromium, soil moisture, pH, and organic matter were significantly correlated (P<0.05) with the bacterial communities. Therefore, these soil properties might be the driving factors affecting the structure of bacterial communities.


Assuntos
Poluentes do Solo , Solo , China , Cromo/análise , Cromo/toxicidade , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/toxicidade
5.
Ecotoxicol Environ Saf ; 212: 111986, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33540338

RESUMO

Population exposure to environmental contaminants can be precisely observed through human biomonitoring studies. The present study aimed to systematically review all the biomonitoring studies conducted in Iran on some selected carcinogen environmental pollutants. In this systematic review study, 11 carcinogen agents were selected including arsenic, cadmium, chromium, nickel, lindane, benzene, trichloroethylene (TCE), pentachlorophenol (PCP), radon-222, radium-224, - 226, - 228, and tobacco smoke. The Web of Science, PubMed, and Scopus databases were searched for peer-reviewed articles published in English. After several screening steps, data were extracted from the studies. Meta-analyses (a random-effect model using the DerSimonian-Laired method) were performed only for the biomarkers with more than three eligible articles, including cadmium in blood and breast milk, and arsenic in breast milk. Methodological quality of the studies was assessed using the Newcastle-Ottawa Quality Assessment Scale adapted for cross-sectional studies. Of the 610 articles found in the database search, 30 studies were eligible for qualitative review, and 13 were included in the meta-analysis (cadmium in blood (n = 3), cadmium in breast milk (n = 6), and arsenic in breast milk (n = 4)). The overall pooled average concentrations (95% CI) of cadmium in blood, cadmium in breast milk, and arsenic in breast milk were 0.11 (95% CI: 0.08, 0.14), 5.38 (95% CI: 3.60, 6.96), and 1.42 (95% CI: 1.02, 1.81) µg/L, respectively. These values were compared with the biomarker concentrations in other countries and health-based guideline values. This study showed that there is a need for comprehensive action plans to reduce the exposure of general population to these environmental contaminants.


Assuntos
Monitoramento Biológico , Poluentes Ambientais/análise , Arsênico/análise , Cádmio/análise , Cromo/análise , Estudos Transversais , Exposição Ambiental/análise , Poluição Ambiental/análise , Feminino , Humanos , Irã (Geográfico) , Leite Humano/química , Níquel/análise
6.
Chemosphere ; 272: 129851, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33592513

RESUMO

Adsorption media of hybrid composites is a promising candidate to eliminate the toxic contaminants from an aqueous environment, and good regeneration ability has received considerable interest to be utilized in water and wastewater treatment. Herein, we synthesized Fe3O4 anchored polyaniline intercalated graphene oxide (Fe3O4x%-PANI@GO, where x = 10, 20 and 50% of Fe3O4 particles) hybrid composites by co-precipitation and modified Hummers' method, followed by in-situ polymerization. The as-synthesized Fe3O4x%-PANI@GO acts as a potential host in welcoming the guest ions such as anionic contaminants with different interactions in this work. Besides, the advantages of easy separation by the external magnetic field, the Fe3O4x%-PANI@GO hybrid composite also achieve a great adsorption efficiency of 143.54 and 135.67 mg/g for Cr(VI) and phosphate ions, respectively, than the other adsorbents reported in the literature. The as-synthesized adsorbents were characterized by different analytical techniques and influencing parameters such as contact time, co-existing anions, solution pH, adsorption isotherms, and kinetics were studied in detail. The adsorption system of Fe3O450%-PANI@GO hybrid composite follows the Langmuir isotherm and pseudo-second-order kinetic model for the elimination of Cr(VI) and phosphate ions from aqueous solutions. The feasible removal mechanism of Cr(VI) and phosphate ions was explored by FTIR and XPS techniques for anionic pollutants. Moreover, the selectivity and recyclability tests showed that the Fe3O450%-PANI@GO hybrid composites demonstrated a high adsorption capacity towards the anionic ions from the aqueous environment. Therefore, the present investigation suggested that the Fe3O450%-PANI@GO hybrid composites is an effective adsorbent for the elimination of Cr(VI) and phosphate ions from wastewater.


Assuntos
Poluentes Químicos da Água , Adsorção , Compostos de Anilina , Cromo/análise , Grafite , Íons , Cinética , Fosfatos , Poluentes Químicos da Água/análise
7.
Environ Pollut ; 276: 116745, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33640653

RESUMO

Nanoscale zero-valent iron (nZVI) modified by cationic polyquaternium-7 (M550-nZVI) or anionic carboxymethyl cellulose (CMC-nZVI) were freshly synthesized, and followed by the successful applicability for the stabilization of Cr(VI) in soil. Scanning electron microscope (SEM) showed that the sizes of M550-nZVI and CMC-nZVI were 42-170 nm and 66-200 nm, respectively. X-ray diffraction (XRD) confirmed the presence of Fe0 and Fe3C in the as-synthesized composites. The kinetics were well fitted with pseudo-second order model (R2 > 0.99), indicating that the process was principally chemical reduction. Additionally, we observed that M550-nZVI had better resistance to oxidation than that of CMC-nZVI. Besides, RSM experiments showed that acetate ion (AA) could promote the Cr(VI) removal but humic acid ion (HA) and carbonate ion (CA) resulted in negative effects. Moreover, the modeling predication revealed that the optimum Cr(VI) removal of 92.44% by CMC-nZVI was available, being 22.52% higher than that of M550-nZVI. In conclusion, this work demonstrated that the inoxidizability of M550-nZVI had a dominant advantage, while CMC-nZVI had the more excellent reactivity than M550-nZVI. We believe that our conducted research work will open the new avenues for effective removal of heavy metals from the soil.


Assuntos
Ferro , Poluentes Químicos da Água , Adsorção , Cromo/análise , Cinética , Polímeros , Solo , Poluentes Químicos da Água/análise
8.
Water Sci Technol ; 83(3): 556-566, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33600361

RESUMO

Heavy metals are one of the most dangerous and critical threats to human and environment. In this study, the adsorption efficiency of activated carbon from cassava peels considered as agricultural waste (CPR) was evaluated for removal of heavy metals Cr (VI) and Co (II) from aqueous media. Cassava peel carbon (CPC) was obtained by acid treatment. Structural and morphological properties were investigated using Fourier Transform Infra-Red (FTIR), Scanning Electron Microscopy (SEM), Brunauer-Emmet-Teller surface area (BET) and X-Ray Diffraction (XRD). The adsorption experiments were conducted in batch mode under natural solution pH and complexation of the heavy metals, which allows the use of UV-Visible spectroscopy technique. CPC adsorbent exhibited a high adsorption capacity, according to Langmuir model, for Cr (VI) (166.35 mg/g) and Co (II) (301.63 mg/g) at 25 °C. Kinetic and adsorption isotherms followed the pseudo second-order and Langmuir isotherm models for both metals, respectively. Thermodynamic study confirmed the spontaneity and endothermic nature of both metals adsorption onto CPC surface.


Assuntos
Manihot , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Cromo/análise , Humanos , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/análise
9.
Environ Pollut ; 275: 116650, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33581635

RESUMO

Soil acidification is causing more and more attention, not only because of the harm of acidification itself, but also the greater harm to bacteria brought by some pollutants under acidic condition. Therefore, the toxicities of two typical soil pollutants (perfluorooctane sulfonate (PFOS) and chromium (Cr(VI)) to growth and metabolisms of soil bacteria (Bacillus subtilis as modol) were investigated. Under acidic condition of pH = 5, Cr(VI), PFOS and PFOS + Cr(VI) show stronge inhibition to bacteria growth up to 24.3%, 42.3%, 41.6%, respectively, and this inhibition was about 2-3 times of that at pH = 7. Moreover, acid stress reduces the metabolism of bacteria, while PFOS and Cr(VI) pollution futher strengthens this metabolic inhibition involving oxidative stress and cell permeability. The activities of dehydrogenase (DHA) and electron transport system (ETS) at pH = 5 exposed to Cr(VI), PFOS and combined PFOS + Cr(VI) was 21.5%, 16.9%, 23.2% and 8.9%, 32.2%, 19.1% lower than the control, respectively. However, the relative activity of DHA and ETS at pH = 7 are 5-8 and 2-13 times of that at pH = 5, respectively. Isoelectric point, cell surface hydrophobicity and molecular simulation analysis show that the corresponding mechanism is that acidic conditions enhance the interaction between bacteria and PFOS/Cr(VI) through hydrogen bonding, hydrophobic and electrostatic interactions. The results can guide the remediation of acid soil pollution, and provide a reference for the combined toxicity evaluation of heavy metals and micro-pollutants in acid soil.


Assuntos
Poluentes do Solo , Solo , Ácidos Alcanossulfônicos , Cromo/análise , Cromo/toxicidade , Fluorcarbonetos , Concentração de Íons de Hidrogênio , Estresse Oxidativo , Permeabilidade , Poluentes do Solo/análise , Poluentes do Solo/toxicidade
10.
J Environ Manage ; 285: 112174, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33607566

RESUMO

Chromium (Cr) is a trace element critical to human health and well-being. In the last few decades, its contamination, especially hexavalent chromium [Cr(VI)] form in both terrestrial and aquatic ecosystems, has amplified as a result of various anthropogenic activities. Chromium pollution is a significant environmental threat, severely impacting our environment and natural resources, especially water and soil. Excessive exposure could lead to higher levels of accumulation in human and animal tissues, leading to toxic and detrimental health effects. Several studies have shown that chromium is a toxic element that negatively affects plant metabolic activities, hampering crop growth and yield and reducing vegetable and grain quality. Thus, it must be monitored in water, soil, and crop production system. Various useful and practical remediation technologies have been emerging in regulating chromium in water, soil, and other resources. A sustainable remediation approach must be adopted to balance the environment and nature.


Assuntos
Recuperação e Remediação Ambiental , Poluentes do Solo , Animais , Cromo/análise , Ecossistema , Saúde Ambiental , Humanos , Solo , Poluentes do Solo/análise
11.
J Environ Manage ; 281: 111876, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33418386

RESUMO

As a result of intensive anthropogenic activities, population growth and unplanned urbanization, enormous quantities of organic and inorganic pollutants are discharged into the environment every year. The primary hazardous substances of concern regarding their environmental load and health effects are heavy metals. Heavy metal pollution of aquatic ecosystems, including resources of drinking water and water intended for food processing, has been of increasing interest. Biosorption technology is a promising strategy, as it utilizes industrial or agricultural wastes to remove metals from aqueous media passively, and they represent efficient, cost-effective and environmentally friendly alternatives to traditional adsorbents such as activated carbon. In this paper, the efficiency of biosorption of copper and chromium ions was examined using different agricultural waste biomass - sugar beet shreds, poplar sawdust and wheat straw. The possibility of applying a parallel sigmoidal (PS) model to describe the biosorption process was investigated to confirm its applicability to different types of biomass and various kinds of heavy metal ions. The results showed that the biosorption of copper ions using poplar sawdust and wheat straw consist of two steps. The moiety of one step in the overall process, defined by the parameter p, was determined to be 0.85 for poplar sawdust and 0.86 for wheat straw. These values, being less than 1, clearly indicate that the process consists of two simultaneous, kinetically different steps that shift in their dominance over the process and thus could be successfully modelled by the PS model. These studies also deal with the phenomenological examination of an unusual breakthrough curve obtained for the chromium ions biosorption by sugar beet shreds, by the comparative view of the process flow and changing the pH of the effluent. The clarification of the appearance of a double curve with a negative trend in one part allows adjusting the biosorption conditions to avoid the initial blockage of chromium ion binding to the adsorbent and thus increase the adsorption process efficiency.


Assuntos
Metais Pesados , Poluentes Químicos da Água , Purificação da Água , Adsorção , Biomassa , Cromo/análise , Ecossistema , Concentração de Íons de Hidrogênio , Cinética , Água , Poluentes Químicos da Água/análise
12.
J Environ Manage ; 282: 111939, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33485033

RESUMO

The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g-1 for Cu(II) and 3.86 and 0.98 mmol g-1 for Cr(VI), respectively. The reuse of C1 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower re-adsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.


Assuntos
Quitosana , Poluentes Químicos da Água , Adsorção , Cromo/análise , Cobre/análise , Concentração de Íons de Hidrogênio , Cinética , Piridinas
13.
Ecotoxicol Environ Saf ; 208: 111769, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396087

RESUMO

Soils contaminated with heavy metals such as Chromium (Cr) and Cadmium (Cd) severely impede plant growth. Several rhizospheric microorganisms support plant growth under heavy metal stress. In this study, Cr and Cd stress was applied to in vitro germinating seedlings of a Legume plant species, Sesbania sesban, and investigated the plant growth potential in presence and absence of Bacillus anthracis PM21 bacterial strain under heavy metal stress. The seedlings were exposed to different concentrations of Cr (25-75 mg/L) and Cd (100-200 mg/L) in Petri plates. Growth curve analysis of B. anthracis PM21 revealed its potential to adapt Cr and Cd stress. The bacteria supported plant growth by exhibiting ACC-deaminase activity (1.57-1.75 µM of α-ketobutyrate/h/mg protein), producing Indole-3-acetic acid (99-119 µM/mL) and exopolysaccharides (2.74-2.98 mg/mL), under heavy metal stress condition. Analysis of variance revealed significant differences in growth parameters between the seedlings with and without bacterial inoculation in metal stress condition. The combined Cr+Cd stress (75 + 200 mg/L) significantly reduced root length (70%), shoot length (24%), dry weight (54%) and fresh weight (57%) as compared to control. Conversely, B. anthracis PM21 inoculation to seedlings significantly increased (p ≤ 0.05) seed germination percentage (5%), root length (31%), shoot length (23%) and photosynthetic pigments (Chlorophyll a: 20%; Chlorophyll b: 16% and total chlorophyll: 18%), as compared to control seedlings without B. anthracis PM21 inoculation. The B. anthracis PM21 inoculation also enhanced activities of antioxidant enzymes, including superoxide dismutase (52%), peroxidase (66%), and catalase (21%), and decreased proline content (56%), electrolyte leakage (50%), and malondialdehyde concentration (46%) in seedlings. The B. anthracis PM21 inoculated seedlings of S. sesban exhibited significantly high (p ≤ 0.05) tissue deposition of Cr (17%) and Cd (16%) as compared to their control counterparts. Findings of the study suggested that B. anthracis PM21 endured metal stress through homeostasis of antioxidant activities, and positively impacted S. sesban growth and biomass. Further experiments in controlled conditions are necessary for investigating phytoremediation potential of S. sesban in metal-contaminated soils in presence of B. anthracis PM21 bacterial strain.


Assuntos
Bacillus anthracis/fisiologia , Metais Pesados/toxicidade , Sesbania/fisiologia , Poluentes do Solo/toxicidade , Bacillus anthracis/metabolismo , Biodegradação Ambiental , Cádmio/metabolismo , Catalase/metabolismo , Clorofila , Clorofila A/metabolismo , Cromo/análise , Germinação/efeitos dos fármacos , Ácidos Indolacéticos , Metais Pesados/análise , Plântula/metabolismo , Sesbania/metabolismo , Sesbania/microbiologia , Solo , Poluentes do Solo/análise
14.
Ecotoxicol Environ Saf ; 208: 111735, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396064

RESUMO

The transformation between hexavalent chromium (Cr6+) and trivalent chromium (Cr3+) has a significant impact on ecosystems, as Cr6+ has higher levels of toxicity than Cr3+. In this regard, a variety of Cr6+ reduction processes occurring in natural environments have been studied extensively. In this work, we investigate the reductive transformation of Cr6+ by ferrous ions (Fe2+) in ice at -20 °C, and compare the same process in water at 25 °C. The Fe2+-mediated reduction of Cr6+ occurred much faster in ice than it did in water. The accelerated reduction of Cr6+ in ice is primarily ascribed to the accumulation of Cr6+, Fe2+, and protons in the grain boundaries formed during freezing, which constitutes favorable conditions for redox reactions between Cr6+ and Fe2+. This freeze concentration phenomenon was verified using UV-visible spectroscopy with o-cresolsulfonephthalein (as a pH indicator) and confocal Raman spectroscopy. The reductive transformation of Cr6+ (20 µM) by Fe2+ in ice proceeded rapidly under various Fe2+ concentrations (20-140 µM), pH values (2.0-5.0), and freezing temperatures (-10 to -30 °C) with a constant molar ratio of oxidized Fe2+ to reduced Cr6+ (3:1). This result implies that the proposed mechanism (i.e., the redox reaction between Cr6+ and Fe2+ in ice) can significantly contribute to the natural conversion of Cr6+ in cold regions. The Fe2+-mediated Cr6+ reduction kinetics in frozen Cr6+-contaminated wastewater was similar to that in frozen Cr6+ solution. This indicates that the variety of substrates typically present in electroplating wastewater have a negligible effect on the redox reaction between Cr6+ and Fe2+ in ice; it also proposes that the Fe2+/freezing process can be used for the treatment of Cr6+-contaminated wastewater.


Assuntos
Cromo/química , Congelamento , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Cromo/análise , Ecossistema , Galvanoplastia , Ferro/química , Cinética , Oxirredução , Águas Residuárias/química , Água/química , Poluentes Químicos da Água/análise
15.
Chemosphere ; 272: 129606, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33465610

RESUMO

Reduction and recycling of Cr(VI) can offer environmental governance and sustainable development. Polypyrrole/sugarcane bagasse composites (PPy/SCB) for efficient adsorption and reduction of Cr(VI) in wastewater were prepared by in-situ polymerization. The effects of the initial pH, Cr concentration, adsorbent dosage, contact time, composition ratio and temperature on adsorption capacity were explored. The optimal Cr(VI) adsorption capacity of PPy/SCB was achieved when the pH value was 2.0. The adsorbents before and after adsorption were characterized, which confirmed that adsorption process affects the morphology, composition and structure of the PPy/SCB surface. The adsorption kinetics data of Cr(VI) were best fitted by the pseudo-second-order model, which indicated that Cr(VI) concentration gradient played a driving role in this process. The adsorption isotherm data were consistent with the Langmuir isotherm model with the adsorption capacity of 156-251 mg/g. Synergic effect of PPy and SCB during the processes of electrostatic adsorption and ion exchange, in-situ reduction of electron donors, and coordination were found to be responsible for the rapid removal and toxicity reduction of total Cr in aqueous solution. Cr(VI) anions can be chelated by oxygen-containing functional groups on SCB surface after reduction to simple cations, which was confirmed by Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy results. This study provides a reasonable scheme for the targeted use of waste biomass for heavy metal pollution control.


Assuntos
Saccharum , Poluentes Químicos da Água , Adsorção , Celulose , Cromo/análise , Conservação dos Recursos Naturais , Política Ambiental , Concentração de Íons de Hidrogênio , Cinética , Polímeros , Pirróis , Poluentes Químicos da Água/análise
16.
Bull Environ Contam Toxicol ; 106(1): 134-145, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33392691

RESUMO

To explore the adsorption removal mechanism of Mg-Al layered double oxides (LDOs) for low-concentration (≤ 5 mg L-1) Cr(VI), the adsorption kinetics, adsorption isotherms and its influencing factors were studied by batch experiments. Cr(VI) adsorption reached equilibrium after 6, 11 and 15 h for initial Cr(VI) concentrations of 1, 3 and 5 mg L-1, respectively, and the final adsorption efficiency exceeded 99.0%. The residual concentration of Cr(VI) was within the allowable limit of Drinking Water Quality Standard of World Health Organization (0.05 mg L-1). The experimental data fitted the pseudo-second-order and Freundlich models well. Mg-Al LDOs showed effective adsorption efficiency in the range of pH 3-9, and the adsorption efficiency was influenced by anions competition (HPO42- > SO42- > CO32- > NO3- > Cl-). The analyses of XRD, SEM and FT-IR spectra suggested adsorption Cr(VI) on Mg-Al LDOs was caused by capturing dichromate ions to reconstruct its structure. Therefore, Mg-Al LDOs is promising adsorbents for the low-concentration Cr(VI) treatment in polluted surface water and groundwater.


Assuntos
Óxidos , Poluentes Químicos da Água , Adsorção , Cromo/análise , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/análise
17.
Sci Total Environ ; 768: 144604, 2021 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-33444867

RESUMO

Fe-modified biochar (FeBC) has been considered for aqueous hexavalent chromium (Cr(VI)) removal, but a better understanding is needed with respect to the removal behavior, chemical processes, and removal mechanisms under aerobic and anaerobic conditions. Aqueous Cr(VI) removal was evaluated using unmodified (BC) and FeBC. The Cr(VI) was completely removed in a pH range of 2-10. The removal behavior was properly depicted using pseudo-second-order (PSO) and Langmuir models under aerobic conditions, and using PSO and Freundlich models under anaerobic conditions. Removal rate and capacity were enhanced by up to 3.8 times under anaerobic conditions. Desorption experiments indicated removed Cr in FeBC was stable except under strong acid condition. X-ray absorption spectroscopy (XAS) analysis suggested removed Cr in FeBC was 100% in Cr(III) form and bound to Fe with a bond length of 3.01 Å in the stable form of Fe(III)nCr(III)(1-n)(OOH). The removal mechanisms of Cr(VI) under aerobic conditions by FeBC mainly included electrostatic adsorption, chemical reduction, and complex precipitation.


Assuntos
Síncrotrons , Poluentes Químicos da Água , Adsorção , Anaerobiose , Carvão Vegetal , Cromo/análise , Compostos Férricos , Poluentes Químicos da Água/análise
18.
Chemosphere ; 270: 129412, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33401077

RESUMO

The removal of groundwater contamination is a complex process due to the hydro-geochemical characteristics of the specific site, related maintenance and the possible presence of several types of pollutants, both organic and inorganic. In recent decades, there has been an increasing drive towards more sustainable treatment for contaminated groundwater as opposed to "intensive" treatments, i.e. with high requirements for onsite infrastructure, energy and resource use. In this study, a new remediation technology is proposed, combining the use of advanced drainage systems with adsorption processes, termed "In-situ reactive DRAINage system for groundwater TREATment" (In-DRAIN-TREAT). By taking advantage of the groundwater natural gradient, In-DRAIN-TREAT collects the contaminated groundwater via a drainage system and treats the polluted water directly into an active cell located downstream, avoiding external energy inputs. Preliminary results indicate the applicability and high efficiency of In-DRAIN-TREAT when compared with a permeable reactive barrier (PRB). In-DRAIN-TREAT is applied to remediate a theoretical aquifer with low permeability, contaminated by a 13 m wide hexavalent chromium (CrVI) plume. This is achieved in less than a year, via a drain DN500, 32 m long, a 30 m3 treatment cell filled with activated carbon and no energy consumption. A comparison with permeable barriers also shows a preliminary 63% volume reduction, with a related 10% decrease of remediation costs.


Assuntos
Recuperação e Remediação Ambiental , Água Subterrânea , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Cromo/análise , Permeabilidade , Poluentes Químicos da Água/análise
19.
Ecotoxicol Environ Saf ; 209: 111858, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33385680

RESUMO

A novel amino-functionalized magnetic adsorbent (Fe3O4@C@DETA) was developed for adsorption of Cr(III) and Cr(III)-EDTA from wastewater. Fe3O4@C@DETA were successfully prepared by modification of Fe3O4@C with diethylenediamine (DETA), which exhibits a core-shell structure and sufficient saturation magnetization. Fe3O4@C@DETA exhibits much better adsorption performance for Cr(III) and its chelates than the Fe3O4@C because of newly introduced amino active sites. The enhanced adsorption capacity of Fe3O4@C@DETA for Cr(III) is 44.74 mg g-1 (at 25 °C and pH 3.0), which is due to the surface coordination with the newly introduced amino functional sites. The Cr(III)-EDTA anions as a whole was adsorbed through the electrostatic interaction with protonated amino species of the Fe3O4@C@DETA and have maximum adsorption capacity of 47.27 mg g-1 (at 25 °C and pH 3.0). The adsorption data of free and EDTA coordinated Cr(III) were followed the Langmuir equation, while the adsorption dynamics was well explained by pseudo second order model indicating the chemical nature of adsorption process. The higher concentration of Ca2+ ions in the wastewater compete for adsorption sites and inhibit the Cr(III) removal, while on other hand Ca2+ ions promotes the adsorption of Cr(III)-EDTA, because of electrostatic interaction with adsorbent active sits. Furthermore, the adsorbent can be easily separated by external magnetic field and regenerated in acidic solution. The adsorbent is stable, recyclable and have more than 75% regeneration efficiency and can be repeatedly used in the adsorption process.


Assuntos
Cromo/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Carbono , Ácido Edético , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Magnetismo , Águas Salinas , Salinidade , Águas Residuárias/química , Água/química
20.
Ecotoxicol Environ Saf ; 208: 111685, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396017

RESUMO

The wastewater utilization for irrigation purposes is common practice in peri-urban areas located in vicinity of developed cities. This water contains elements like chromium (Cr), nickel (Ni), cadmium (Cd) and nitrate (NO3-N) that poses health risk when exposed to human. In this study effect of wastewater irrigation from Chakara wastewater plant, Faisalabad on growth of wheat and health risks was assessed. Pot experiment was conducted at Institute of Soil and Environmental, University of Agriculture, Faisalabad using different concentration of wastewater as treatment 100% tap water, 25% wastewater + 75% tap water, 50% wastewater + 50% tap water, 75% wastewater + 25% tap water, 100% wastewater. The results indicated that the wastewater irrigation negatively effects the plant growth and physiological parameters. The minimum plant height, grain weight, spike length, osmotic potential and SPAD values were recorded 50.33 cm, 1.47 g plant-1, 7.00 cm, 423 and 38.91 respectively in 100% wastewater irrigation. The risk quotient (RQ TEs) for each toxic element and cumulative risk index (RI TEs) values were calculated. The cadmium risk quotient (Cd RQ) for adults was on margin and value was >1 for in 75% wastewater + 25% tap water and 100% wastewater irrigation, while the RQ for Ni and Cr was <1. Maximum RI TEs values calculated in 100% wastewater irrigation 0.424 and 0.294 for children and adults respectively. Hence it was concluded that wastewater irrigation significantly increased the accumulation rate of metals and nitrate in wheat and cause potential health risks for children and adults.


Assuntos
Irrigação Agrícola/métodos , Bioacumulação/efeitos dos fármacos , Metais Pesados/toxicidade , Nitratos/toxicidade , Poluentes do Solo/toxicidade , Triticum/efeitos dos fármacos , Águas Residuárias/química , Adulto , Cádmio/análise , Cádmio/toxicidade , Criança , Cromo/análise , Cromo/toxicidade , Cidades , Grão Comestível/química , Humanos , Metais Pesados/análise , Modelos Teóricos , Níquel/análise , Níquel/toxicidade , Nitratos/análise , Paquistão , Medição de Risco , Solo/química , Poluentes do Solo/análise , Triticum/crescimento & desenvolvimento , Triticum/metabolismo , Águas Residuárias/análise
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