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1.
Chemosphere ; 239: 124715, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31499311

RESUMO

Electrodeposition is an economical and efficient way to prepare Ti/SnO2-Sb electrode for electrochemical oxidizing pollutants in wastewater. The solvent used for electrodeposition has a great effect on electrode performance. The conventional Ti/SnO2-Sb electrode electrodeposited using aqueous solvent has poor electrochemical activity and short service life. In this study, a Ti/SnO2-Sb electrode was prepared via electrodeposition using a deep eutectic solvent (DES). This new Ti/SnO2-Sb-DES electrode performed a rate constant of 0.571 h-1 for methylene blue decolorization and long accelerated service life of 12.9 h (100 mA cm-2; 0.5 M H2SO4), which were 1.7 times and 3.2 times as high as that of the electrode prepared in aqueous solvent, respectively. The enhanced properties were related to the 1.3 times increased electrochemically active surface area of Ti/SnO2-Sb-DES electrode which had a rough, multilayer and uniform surface structure packed with nano-sized coating particles. In conclusion, this study developed a facile, green and efficient pathway to prepare Ti/SnO2-Sb electrode with high performance.


Assuntos
Antimônio/química , Técnicas Eletroquímicas/métodos , Galvanoplastia/métodos , Solventes/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Eletrodos/normas , Azul de Metileno/química , Oxirredução , Compostos de Estanho/química , Titânio/química , Águas Residuárias/química
2.
Chemosphere ; 240: 124885, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31568939

RESUMO

Chromium (Cr)-bearing electroplating sludge is a hazardous solid waste and has a detrimental effect on human health and the environment. In this study, an alkali-activated slag binders, namely, formed by the reaction of blast furnace slag (BFS) with alkali, was applied to the stabilization/solidification (S/S) of electroplating sludge. The effects of liquid-solid ratio, water glass modulus ratio (molar ratio of SiO2 to Na2O), water glass dosage, and electroplating sludge amount on the compressive strength and Cr leachability of binders were analyzed. The related mechanism of the S/S of electroplating sludge was discussed on the basis of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS). Results showed that the compressive strength of the alkali-activated slag binder first increased and then remained stable with the increase in liquid-solid ratio, water glass modulus ratio, and water glass dosage. By contrast, the leaching concentrations of Cr(VI) and total Cr decreased with the increase in liquid-solid ratio, water glass modulus ratio, water glass dosage, and curing time. In addition, XRD, FTIR, and SEM-EDS revealed that the hydration products of the binders were mainly low-crystallinity and dense calcium silicate hydrate gels, and Cr(VI) had been effectively immobilized in the structure. The reduction in Cr(VI) by the reductive components in the BFS boosted the stabilization of Cr-bearing electroplating sludge. Overall, the BFS binders containing electroplating sludge had relatively high compressive strengths and low Cr(VI) leaching concentrations. The physical encapsulation, chemical bonding, and absorption contributed the Cr immobilization during the S/S process of electroplating sludge.


Assuntos
Álcalis/química , Cromo/química , Galvanoplastia , Recuperação e Remediação Ambiental , Resíduos Perigosos/análise , Esgotos/química , Humanos
3.
Bioelectrochemistry ; 132: 107436, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31855832

RESUMO

Catalytic properties and high adsorption affinity of nucleic acids and proteins to silver amalgam electrode surface make this kind of electrified interface perspective for bioanalytical and biomedical applications. For the first time, a basal-plane pyrolytic graphite electrode (bPGE) has been used as a substrate for electrodeposition of silver amalgam particles (AgAPs). Optimization of the resulting composition, surface morphology and electrochemical properties of the AgAPs was done by scanning electron microscopy with energy disperse X-ray spectroscopy, image processing software and voltammetric detection of electrochemically reducible model organic nitro compound, 4-nitrophenol. Spectro-electrochemical applicability of bPGE-AgAP has been demonstrated by electrolysis of 4-nitrophenol. Simultaneous UV-Vis-chronoamperometry provided information on the number of exchange electrons and the reduction rate constants. Preferential adsorption of the fluorescently labelled calf thymus DNA and the green fluorescent protein (GFP) on the surface of AgAPs was observed by fluorescence microscopy. In contrast to previously studied indium-tin oxide and vapour-deposited gold decorated by AgAPs, herein the presented bPGE-AgAP has provided sufficiently wide negative potential window allowing direct electroanalysis of non-labelled DNA and GFP using intrinsic electrochemical signals independently of the fluorescent labelling. The bPGE-AgAP can thus be expected to find application opportunities in protein electrochemistry, (bio)sensor development or in-situ spectro-electrochemical studies.


Assuntos
DNA/análise , Técnicas Eletroquímicas/métodos , Galvanoplastia , Proteínas de Fluorescência Verde/análise , Nitrofenóis/análise , Prata/química , Adsorção , Microscopia Eletrônica de Varredura
4.
Ecotoxicol Environ Saf ; 185: 109734, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31574371

RESUMO

In the present study we are investigating the Cr(VI) reduction potential of a multi-metal tolerant fungus (isolate CR700); isolated from electroplating wastewater. Based on the ITS region sequencing, the isolate was identified as Trichoderma lixii isolate CR700 and able to tolerate As(2000 mg/L), Ni(1500 mg/L), Zn(1200 mg/L), Cu(1200 mg/L), Cr(1000 mg/L), and 100 mg/L of Pb and Cd evident from tolerance assay. Cr(VI) reduction experiment was conducted in Erlenmeyer flasks containing different concentration of Cr(VI) (0-200 mg/L) amended potato dextrose broth medium followed by inoculating with a disk (0.5 cm diameter) of 7 days grown isolate CR700, and achieved a maximum of 99.4% within 120 h at 50 mg/L of Cr(VI). However, the accumulation of total Cr by isolate CR700 was 2.12 ±â€¯0.15 mg/g of dried biomass at the same concentration after 144 h of exposure. Isolate CR700 showed the capability to reduce Cr(VI) at different physicochemical stress conditions such as pH, temperature, heavy metals, metabolic inhibitor and also in tannery wastewater. Fungus exhibited multifarious morphological and biochemical response under the exposure of Cr(VI); the scanning electron microscopic analysis revealed that Cr(VI) treated mycelia of isolate CR700 comparatively irregular, aggregated and swelled than without treated mycelia which might be due to the tolerance mechanism and vacuolar compartmentation of chromium. Moreover, energy dispersive spectroscopy and x-ray photoelectron spectroscopic analysis exposed the Cr(III) precipitation on the mycelia surface of isolate CR700 and Fourier-transform infrared spectroscopic analysis suggested the contribution of the protein associated functional group in the complexation of Cr(VI). The phytotoxicity test of fungal treated 100 mg/L of Cr(VI) supernatant on Vigna radiata and Cicer arietinum revealed the successful detoxification/remediation of Cr(VI).


Assuntos
Cromo/toxicidade , Galvanoplastia , Estresse Oxidativo/efeitos dos fármacos , Trichoderma/metabolismo , Águas Residuárias/microbiologia , Biodegradação Ambiental , Cicer/efeitos dos fármacos , Modelos Teóricos , Oxirredução , Vigna/efeitos dos fármacos
5.
Chemosphere ; 237: 124567, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31549665

RESUMO

Hexavalent chromium reduction by microbes can mitigate the chromium toxicity to the environment. In the present study Cr[VI] tolerant fungal isolate (CR500) was isolated from electroplating wastewater, was able to tolerate 800 mg/L of Cr[VI. Based on the ITS region sequencing, the isolate was identified as Aspergillus flavus CR500, showed multifarious biochemical (reactive oxygen species, antioxidants response and non-protein thiol) and morphological (protrusion less, constriction and swelling/outwards growth in mycelia) response under Cr[VI] stress. Batch experiment was conducted at different Cr[VI] concentration (0-200 mg/L) to optimize the Cr[VI] reduction and removal ability of isolate CR500; results showed 89.1% reduction of Cr[VI] to Cr[III] within 24 h and 4.9 ±â€¯0.12 mg of Cr per gram of dried biomass accumulation within 144 h at the concentration of 50 mg/L of Cr[VI]. However, a maximum of 79.4% removal of Cr was recorded at 5 mg/L within 144 h. Fourier-transform infrared spectroscopy, energy dispersive x-ray spectroscopy and X-ray diffraction analysis revealed that chromium removal also happened via adsorption/precipitation on the mycelia surface. Fungus treated and without treated 100 mg/L of Cr[VI] solution was subjected to phytotoxicity test using Vigna radiata seeds and result revealed that A. flavus CR500 successfully detoxified the Cr[VI] via reduction and removal mechanisms. Isolate CR500 also exhibited efficient bioreduction potential at different temperature (20-40 °C), pH (5.0-9.0), heavy metals (As, Cd, Cu, Mn, Ni and Pb), metabolic inhibitors (phenol and EDTA) and in sterilized tannery effluent that make it a potential candidate for Cr[VI] bioremediation.


Assuntos
Aspergillus flavus/metabolismo , Cromo/metabolismo , Cromo/toxicidade , Águas Residuárias/microbiologia , Adsorção , Aspergillus flavus/efeitos dos fármacos , Aspergillus flavus/genética , Biodegradação Ambiental , Galvanoplastia , Metais Pesados/análise , Fenol/análise , Sementes/efeitos dos fármacos , Espectrometria por Raios X , Espectroscopia de Infravermelho com Transformada de Fourier , Vigna/efeitos dos fármacos , Águas Residuárias/análise , Águas Residuárias/toxicidade , Difração de Raios X
6.
Chemosphere ; 234: 917-924, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31519100

RESUMO

Nickel, massively used in plating industry but detrimental to ecosystem, tends to form stable complexes with organic additives in industrial effluents. Currently, most of the available processes aim at water decontamination from free toxic metal ions and thus, could not effectively remove nickel-carboxyl complexes from water. Herein, we employed a proprietary combined process Fe(III)/UV/NaOH, namely Fe(III) displacement and UV irradiation followed by alkaline precipitation, to validate its feasibility on the efficient removal of nickel-carboxyl complexes from synthetic and authentic effluents. Fe(III)/UV/NaOH outperformed other commonly used processes including NaOH precipitation, UV/NaOH, Fe(III) coagulation, and Fenton/NaOH. Each unit of the combined process was optimized, and the underlying mechanism was elucidated. Fe(III) displacement favored the stoichiometric release of free nickel ions and formation of Fe(III)-carboxyl complexes, which could be decarboxylated via ligand-metal charge transfer under UV irradiation. The precipitation unit aims at simultaneously removing the released Ni along with Fe species. Attractively, the presence of other organic species (ethylene glycol, ethyl acetate and humic acid) and anions (chloride and sulfate) exerted very slight effect on the final Ni removal, whereas greatly adverse effect occurred on the Fenton process under similar conditions. The feasibility of the combined process was validated by testing on an authentic electroplating effluent, resulting in the residual Ni below 0.1 mg/L, the most stringent discharge standard for Ni in electroplating effluent in China.


Assuntos
Compostos Férricos/química , Níquel/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , China , Ecossistema , Galvanoplastia , Hidróxido de Sódio , Sulfatos , Raios Ultravioleta , Água , Poluentes Químicos da Água/análise
7.
Mater Sci Eng C Mater Biol Appl ; 104: 109880, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500020

RESUMO

The direct electron transfer and enzyme catalytic activity were investigated in electrochemical biosensor based on glucose oxidase (GOx) and electrochemical reduced graphene oxide-poly-(l-lysine) (ERGO-PLL) hybrid composite film embedded in a biocompatible matrix of Nafion. The ERGO-PLL was fabricated onto glassy carbon electrode (GCE) through one step electrodeposition of RGO incorporating PLL from graphene oxide-l-lysine aqueous dispersion. The fabrication process of Nafion/GOx/ERGO-PLL/GCE has been characterized by cyclic voltammetry and electrochemical impedance spectroscopy, and the surface morphology of modified electrodes were characterized by scanning electron microscopy. A pair of well-defined redox peaks with formal potential and peak separation of -0.461 V and 30 mV were observed at scan rate of 50 mV s-1, the electron transfer rate constant was calculated to be 18.7 s-1, demonstrated that direct electron transfer between immobilized GOx with ERGO-PLL and GCE was achieved. Moreover, the fabricated enzyme biosensor exhibited excellent electrocatalytic activity for determination of glucose in O2-free PBS (7.40) with linear voltammetric response from 0.005 to 9.0 mmol L-1, and detection limits (S/N = 3) of 2.0 µmol L-1. This work indicates that ERGO-PLL based modified electrode is superior to that of graphene based, and could be applied in biosensors, bioelectronics and electrocatalysis, etc.


Assuntos
Glucose Oxidase/química , Glucose/química , Grafite/química , Lisina/química , Técnicas Biossensoriais/métodos , Carbono/química , Catálise , Técnicas Eletroquímicas/métodos , Eletroquímica/métodos , Eletrodos , Galvanoplastia/métodos , Enzimas Imobilizadas/química , Concentração de Íons de Hidrogênio , Nanocompostos/química , Oxirredução , Polimerização
8.
Environ Sci Pollut Res Int ; 26(29): 29736-29747, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31402438

RESUMO

Developing low cost and efficient method for the treatment of electroplating wastewater containing heavy metals complexed with chelating agent has attracted increasing attention in industrial wastewater treatment. This study involved a system combining Fenton oxidation (FO) and recycled ferrite (RF) process for treating synthetic solution containing Ni(II)-EDTA at ambient temperature. In this system, the FO reaction can produce hydroxyl radicals with high redox potential to decomplex the metal-organic complexes and degrade the organics, thereby enhancing the removal efficiency of heavy metals. The RF process is to incorporate the non-iron metal into the spinel ferrites at room temperature, and stabilize the sludge. As a result, the toxicity characteristic leaching procedure can fulfill the relevant standards. Furthermore, the ferrous ions in Fenton reaction could be used as the source of irons in RF process. After treatment by the combined process, the effluent water fulfills the relevant standard in China. In comparison with conventional alkaline precipitation, the sludge sedimentation velocity of FO-RF is 2.16 times faster than that of conventional alkaline precipitation and the volume of sludge is reduced by half, which strongly demonstrated the advantages of the presented FO-RF system and indicated the huge potential for the treatment of EDTA-chelated nickel.


Assuntos
Ácido Edético/química , Galvanoplastia , Compostos Férricos/química , Níquel/química , Eliminação de Resíduos Líquidos/métodos , Óxido de Alumínio/química , Quelantes/química , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Ferro/química , Óxido de Magnésio/química , Metais Pesados/química , Oxirredução , Reciclagem , Esgotos , Temperatura Ambiente , Águas Residuárias/química , Poluentes Químicos da Água/química
9.
Biosens Bioelectron ; 142: 111577, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31430613

RESUMO

A novel nonsemiconductor photoelectrochemical biosensor was first constructed using the unique plasmonic AuNi nanodendrite arrays. The AuNi nanodendrite arrays were rapidly prepared by a one-step electrodeposition method using the porous anodic aluminum templates. Owing to its hierarchical structure with abundant active sites, the synergistic catalytic of Au and Ni can be better exploited. These plasmonic AuNi nanodendrite arrays display exceptional photoelectrocatalytic activities for glucose oxidation and hydrogen peroxide reduction reaction under visible light illumination. Specifically, the detection sensitivity for glucose (3.7277 mA mM-1 cm-2) under illumination is about 3.3 folds improvement than in the dark (1.1287 mA mM-1 cm-2), together with high accuracy and low detection limit of 3 µM. The markedly enhanced performance of AuNi nanodendrite arrays can be attributed to its hierarchical structure with abundant active sites and plasmonic effect of Au with strong absorption band in visible region. Such a newly developed method via the facile and low-cost route is of great significance in designing the plasmon-aided photoelectrochemical biosensors.


Assuntos
Técnicas Biossensoriais/métodos , Glicemia/análise , Ouro/química , Peróxido de Hidrogênio/análise , Nanoestruturas/química , Níquel/química , Técnicas Eletroquímicas/métodos , Galvanoplastia/métodos , Humanos , Limite de Detecção , Masculino , Nanoestruturas/ultraestrutura , Semicondutores
10.
Bioelectrochemistry ; 130: 107325, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31295700

RESUMO

In order to understand how energy metabolism adapts to changes in neuronal activity it is imperative to perform direct measurements of the flux of glucose (and other metabolites) in brain tissue. Metabolic studies using brain slice preparations are attractive due to the controllability of recording conditions, absence of anesthetic interference and refined animal experimental protocols. In this work, taking advantage of the small size and versatility of carbon fiber microelectrodes (CFMs), we aimed to develop an amperometric glucose microbiosensor suitable for glucose measurement in brain slices. Potentiostatic- or galvanostatic-driven platinum electrodeposition was used to improve the analytical properties of CFMs towards detection of hydrogen peroxide. The platinized CFMs served as platform for the development of glucose microbiosensors through the immobilization of glucose-oxidase (GOx) by cross-linking with glutaraldehyde in the presence of BSA. Selective glucose measurements were attained by modifying the electrode with a permselective layer of meta-phenylenediamine and by integrating a null sensor. The in vitro characterization studies support the good analytical features of the CFM/Pt-based microbiosensors to reliably measure glucose in brain tissue. The ex vivo experiments in rodent hippocampal slices validated their suitability to measure evoked changes in extracellular glucose. This approach, encompassing the use of null sensor to cross-check the selectivity on a moment-to-moment basis, allowed us to provide the temporal and quantitative profile of extracellular glucose changes in hippocampal slices following a spreading depolarization event. Overall, these results support the potential of these microbiosensors to be used as a valuable tool to investigate the complex nature of glucose utilization in brain tissue linked to neuronal activation both in physiological and pathological conditions.


Assuntos
Técnicas Biossensoriais/métodos , Fibra de Carbono/química , Glucose/análise , Platina/química , Animais , Aspergillus niger/enzimologia , Encéfalo/metabolismo , Química Encefálica , Galvanoplastia , Enzimas Imobilizadas/química , Glucose/metabolismo , Glucose Oxidase/química , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Microeletrodos , Ratos Wistar
11.
Environ Sci Pollut Res Int ; 26(24): 25372-25385, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31264158

RESUMO

Electroplating manufacturing processes release industrial effluents that comprise severe levels of heavy metals into the environment. This study investigated the utilization of nanoparticles of zero-valent iron (nZVI) for the treatment of electroplating wastewater industry containing multiple heavy metal ions. In batch experiments using Cu2+ as a single solute, the optimum operating condition was pH 7.3, nZVI dosage 1.6 g/L, time 36 min, temperature 30 °C, and agitation speed 180 rpm, achieving almost 100% Cu2+ removal efficiency. The adsorption mechanisms were illustrated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) spectrometer. Moreover, continuous-feed experiments were performed to treat real electroplating wastewater industry via adsorption and sedimentation processes. The system attained removal efficiencies of 91.3% total suspended solids (TSS), 68.3% chemical oxygen demand (COD), 94.2% nitrogen (N), 98.5% phosphorus (P), 66.7% Cr6+, 91.5% Pb2+, 83.3% Ag+, 80.8% Cu2+, 17.4% Ni2+, 47.1% Mn2+, 54.6% Zn2+, 94.7% Fe3+, 100.0% Al3+, and 42.1% Co2+. The removal mechanisms included reduction of Men+ to Me(n-x)+/Me0 by the Fe0 core, adsorption to the oxide shell as Me(OH)x and Me-Fe-OOH, oxidation of Men+ to Me(n+z)+, specific surface bonding, and sequential steps of electron transfer and precipitation. The total cost, including amortized and operating expenses for scaling up the adsorption system, was 4.45$ per m3 of electroplating wastewater. Graphical abstract.


Assuntos
Galvanoplastia , Nanopartículas/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/análise , Adsorção , Análise da Demanda Biológica de Oxigênio , Ferro/química , Metais Pesados/análise , Oxirredução , Espectrometria por Raios X
12.
Chemosphere ; 236: 124330, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31319309

RESUMO

Shear-induced dissociation coupling with ultrafiltration (SID-UF) is an efficient and environment-friendly technology for the separation of heavy metal ions. In this paper, SID-UF was successfully employed for the selective recovery of nickel, zinc and copper from electroplating effluent using poly (acrylic acid) sodium (PAAS) and copolymer of maleic acid and acrylic acid (PMA) as complexants, respectively. The effects of the pH, mass ratio of polymer to metal ions (P/M) and the rotating speed on the metals removal efficiency are discussed in detail. The shear stabilities of the polymer-metal complexes were explored and the complexes critical shear rates (γc) were calculated. The results show that the order of the shear stabilities of PAA-metal complex is PAA-Zn > PAA-Cu > PAA-Ni, and that of PMA-metal complex is PMA-Cu > PMA-Ni > PMA-Zn. In addition, the construction of the stable structures of complexes and the calculation of the energies of the frontier molecular orbital by density functional theory method further predict and confirm the shear stabilities of the polymer-metal complexes.


Assuntos
Galvanoplastia/métodos , Metais Pesados/química , Ultrafiltração/métodos
13.
Artigo em Chinês | MEDLINE | ID: mdl-31256522

RESUMO

Objective: To apply the semi-quantitative risk assessment model in the Technical Guidelines for Occupational Health Risk Assessment of Chemical Hazardous Factors in the Workplace to assess the occupational health risk of electroplating enterprises and explore its applicable conditions and characteristics. Methods: Three electroplating enterprises were selected as the research objects. Occupational hygiene survey and hazard factor detection were conducted on the spot. Three semi-quantitative risk assessment methods were used to assess the risk, and the evaluation results were compared. Results: The consistency between the contact index method and the comprehensive index method was strong. The weighted Kappa value was 0.946 and the P value was less than 0.001, but the consistency between the contact ratio method, the contact index method and the comprehensive index method was poor. The weighted Kappa value was 0.345 and 0.391, and the P value was 0.009 and 0.004, respectively. When the contact concentration is less than 50% OELs, the evaluation results of the contact ratio method are lower than those of the exponential method and the comprehensive exponential method. The consistency of the three methods was the highest when the contact concentration (>50%) and (OELs, the results of the contact ratio method are higher than those of the index method and the comprehensive index method. Conclusion: Contact ratio method is suitable for occupational health risk assessment under the condition of incomplete occupational health information and for enterprise managers to identify key control points of health risk through self-assessment; Contact index method is suitable for hazard risk assessment of occupational hazards without sampling test conditions or OELs, and pre-assessment of occupational hazards of construction projects without access to analogical test data. The index method is suitable for occupational health risk assessment with available testing data and complete occupational health information.


Assuntos
Galvanoplastia , Humanos , Exposição Ocupacional , Saúde do Trabalhador , Medição de Risco , Local de Trabalho
14.
Chemosphere ; 233: 559-569, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31195261

RESUMO

In this study, the performance of glyphosate removal in an electrocoagulation batch with two electrodes formed by the same metal type, consisting of aluminum, iron, steel and copper have been compared. The aim of this study intends to remove glyphosate from an aqueous solution by an electrocoagulation process using metal electrode plates, which involves electrogeneration of metal cations as coagulant agents. The production of metal cations showed an ability to bind together to form aggregates of flocs composed of a combination of glyphosate and metal oxide. Electrocoagulation using aluminum electrodes indicated a high percentage removal of glyphosate, 94.25%; followed by iron electrodes, 88.37%; steel electrodes, 62.82%; and copper electrodes, 46.69%. The treated aqueous solution was then analyzed by Fourier Transform Infrared Spectroscopy. Percentages of Carbon, Hydrogen, Nitrogen, Sulfur remaining in the treated aqueous solution after the electrocoagulation process have been determined. The treated water and sludge were characterized and the mechanism of the overall process was concluded as an outcome. An X-Ray Diffraction analysis of dried sludge confirmed that new polymeric compounds were formed during the treatment. The sludge composed of new compounds were also verified the removals. This study revealed that an electrocoagulation process using metal electrodes is reliable and efficient.


Assuntos
Glicina/análogos & derivados , Herbicidas/química , Alumínio , Cobre , Eletrocoagulação/métodos , Eletrodos , Galvanoplastia , Glicina/química , Concentração de Íons de Hidrogênio , Ferro/química , Modelos Químicos , Esgotos , Espectroscopia de Infravermelho com Transformada de Fourier , Purificação da Água/métodos
15.
Mater Sci Eng C Mater Biol Appl ; 102: 623-633, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31147034

RESUMO

The current work deals with a time-dependent study to track the antibacterial action of electrodeposited Cu, Cu-SiC functionally graded coating (FGC) against Escherichia coli NCIM 2931 (Gram-negative) and Bacillus subtilis NCIM 2063 (Gram-positive). After 24 h of incubation, the Cu, Cu-SiC FGC causes 7 Escherichia coli NCIM 2931 and 10 Bacillus subtilis NCIM 2063 log reduction of planktonic cells. The outer membrane permeabilization experiment proves that the intake of excessive Cu ions leads to the damage of bacterial cell membrane followed by lipid degradation. The thiobarbituric acid reactive substances assay reveals that Cu ions released from the surface of Cu, Cu-SiC FGC triggers the oxidative degeneration of phospholipids (most abundant constituent of bacterial cell membrane). This was further cross-verified using atomic absorption spectroscopy. From 0 to 24 h, the bacterial morphology is characterized using transmission electron microscope and scanning electron microscope which shows the cytoplasmic leakage and cell death. The Cu, Cu-SiC FGC also exhibits hydrophobic surface (contact angle of 144°) which prevents the bacterial adherence to the surface and thus, inhibits them to penetrate into its bulk. The observed results of antibacterial and anti-adhesion properties of Cu, Cu-SiC FGC are compared with single-layered metallic Cu and Cu-SiC nanocomposite coatings. Hence, the electrodeposited Cu, Cu-SiC FGC has the potential to serve as an inexpensive touch surface alternative for the healthcare industries.


Assuntos
Membrana Celular/metabolismo , Materiais Revestidos Biocompatíveis/farmacologia , Galvanoplastia/métodos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Peroxidação de Lipídeos/efeitos dos fármacos , Antibacterianos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/crescimento & desenvolvimento , Bacillus subtilis/ultraestrutura , Aderência Bacteriana/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Contagem de Colônia Microbiana , Cobre/metabolismo , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/ultraestrutura , Íons , Testes de Sensibilidade Microbiana , Viabilidade Microbiana/efeitos dos fármacos , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismo , Fatores de Tempo
16.
Mater Sci Eng C Mater Biol Appl ; 102: 661-669, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31147039

RESUMO

A selective electrochemical sensor based on poly(3,4-ethylenedioxythiophene) (PEDOT) - Prussian blue nanoparticles (PBNPs) for hydrogen peroxide (H2O2) determination was prepared by innovative sinusoidal voltage (SV) method. The successful incorporation of citrate-stabilized PBNPs into PEDOT matrix was confirmed by energy dispersive X-ray analysis (EDX), Raman spectroscopy, UV-Vis spectroelectrochemistry and cyclic voltammetry measurements. The SV preparation method provides a PEDOT-PBNPs coating with rough surface morphology and good electrocatalytic activity toward H2O2 reduction. The amperometric response of PEDOT-PBNPs-based sensor at -50 mV vs. Ag/AgCl is linear within the range of concentrations from 5 µM to 1 mM H2O2 with a detection limit of 1.4 µM H2O2. The proposed Pt/PEDOT-PBNPs sensor displays good repeatability, reproducibility, operational stability as well as good selectivity toward H2O2 determination in the presence of interfering species like dopamine (DA), uric acid (UA), KNO2 glucose (Glu), KNO3 and ascorbic acid (AA), and was successfully applied to H2O2 determination in human blood samples without biofouling.


Assuntos
Técnicas Biossensoriais/métodos , Compostos Bicíclicos Heterocíclicos com Pontes/química , Eletricidade , Galvanoplastia/métodos , Ferrocianetos/química , Peróxido de Hidrogênio/sangue , Nanopartículas/química , Polímeros/química , Espectroscopia Dielétrica , Feminino , Humanos , Pessoa de Meia-Idade , Nanopartículas/ultraestrutura , Espectroscopia de Infravermelho com Transformada de Fourier
17.
Chemosphere ; 232: 345-355, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31158629

RESUMO

The semi-pilot scale bioleaching of electroplating sludge by the moderately thermophilic acidophilic consortium was carried out for the first time. During the microbial cultivation, Leptospirillum ferriphilum CS13, Acidithiobacillus caldus S2, and Sulfobacillus acidophilus CS5 could grow rapidly in a 300 L aeration packed reactor, in which the total suspended cell concentration could fluctuate around 3 × 108 cells/mL and the community structure remained relatively stable. During the bioleaching process, the microbial stock solution could effectively leach heavy metals from electroplating sludge in a stirred reactor within a few hours. Meanwhile, the effects of pH, temperature, the quantity of active culture, and liquid-solid ratio on the bioleaching behavior were also investigated. The optimal conditions for electroplating sludge bioleaching were pH 1.5, temperature 45 °C, bacterial liquid ratio 40%, liquid-solid ratio 4:1 L kg-1, and leaching time 5 h. The total removal rate of various heavy metals in electroplating sludge was over 99%. The bioleaching residue was successfully passed the TCLP test, and the total contents of heavy metals in the residue were also well below the regulatory criteria. In addition, the XRD analysis of the bioleaching residue was also confirmed that the moderately thermophilic consortium bioleaching provided a cleaner process than chemical leaching on the removal of the residual fraction metals, which was feasible and attractive for industrial treatment of electroplating sludge.


Assuntos
Galvanoplastia , Eliminação de Resíduos/métodos , Acidithiobacillus , Bactérias , Reatores Biológicos , Concentração de Íons de Hidrogênio , Metais Pesados/análise , Projetos Piloto , Temperatura Ambiente
18.
Chemosphere ; 232: 430-438, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31158638

RESUMO

Long-term effects of Pb2+ on the operating performance and membrane fouling of two hydrolytic-anoxic-oxic-membrane bioreactors treating synthetic electroplating wastewater were investigated. The COD, NH4+-N and TN removal efficiencies decreased by 5.5%, 10.4% and 7.9% with long-term exposure of 2 mg L-1 Pb2+, while serious decreases achieved 25.4%, 35.0% and 26.2% with 6 mg L-1 Pb2+ exposure, respectively. 2 mg L-1 Pb2+ mitigated the cake layer fouling rate by 25.4% but increased the pore blocking rate by 69.1%, which was contributed by the increase of low and moderate molecular weight (MW) components in the soluble and colloidal foulants (SCFs). 6 mg L-1 Pb2+ accelerated the cake layer fouling rate by 101.1%, but mitigated the pore blocking rate by 6.4% due to the increase of high MW SCFs (especially polysaccharides). Thermodynamic analyses showed that Pb2+ regulated the concentration and protein/polysaccharide ratio of loosely bound extracellular polymeric substances, thus changing the flocs hydrophobicity and aggregation capacity, leading the cake layer fouling rate variation.


Assuntos
Incrustação Biológica , Reatores Biológicos/microbiologia , Galvanoplastia , Chumbo/toxicidade , Membranas Artificiais , Águas Residuárias/química , Poluentes Químicos da Água/toxicidade , Aerobiose , Anaerobiose , Chumbo/análise , Poluentes Químicos da Água/análise
19.
Environ Sci Pollut Res Int ; 26(22): 22596-22610, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31165447

RESUMO

Comprehensive understanding of the influence of soil properties on the potential availability of heavy metals could facilitate soil environment management. This study investigated the distribution of heavy metals and their potential availability in paddy and vegetable fields around electroplating factory outlets and irrigated with its wastewater. The potential availability was assessed using secondary phase fraction (SPF) of heavy metals, including acid-soluble, reducible, and oxidizable fractions resulting from BCR sequential extraction procedure. In total, 94 of topsoil samples (0-20 cm) were collected. Total and SPF concentrations of heavy metals as well as soil physicochemical properties were determined. Multivariable statistical analyses (i.e., principal component analysis (PCA) and redundancy analysis (RDA)) were employed. Results showed that total and SPF concentrations of heavy metals in soil decreased (P<0.05) as sampling distance away from the electroplating factories increased, suggesting that sampling distance was the major parameter that affected gradient variations of both total and potential availability of soil heavy metals. According to PCA, soil samples distributed on the PCA axis representing anthropogenic effect, illustrating that the variation of soil properties resulted from irrigation with electroplating wastewater. RDA and stepwise regression indicated that soil Mn oxides, amorphous Fe oxides, silt content, and pH could explain 68.8% and 43.5% of the variation of SPF concentration in paddy and vegetable garden soil, respectively, suggesting they were the most important factors influencing the potential availability of heavy metals in soils. The potential availability of heavy metals in soil was positively correlated with soil Mn oxides but negatively associated with soil amorphous Fe oxides, indicating that Mn oxides enhanced the potential availability of heavy metals while amorphous Fe oxides reduced the potential availability.


Assuntos
Galvanoplastia , Monitoramento Ambiental , Metais Pesados/análise , Poluentes do Solo/análise , Solo/química , Verduras
20.
J Environ Manage ; 245: 447-453, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31170633

RESUMO

Nickel ions in electroplating wastewater can be removed by the bio-mineralization method. Bacillus subtilis can produce alkaline phosphatase, which hydrolyzes organophosphate monoesters and produces phosphate ions. Fourier-transform infrared spectroscopy (FTIR) showed that the precipitated material contains phosphate ions. X-ray diffraction (XRD) showed that nickel ions in electroplating wastewater react with Bacillus subtilis and organophosphate monoesters to obtain nickel phosphate octahydrate (Ni3(PO4)2·8H2O). The removal efficiency of nickel ions could reach 76.41% with the optimum content of the organophosphate monoester (0.02 mol), Bacillus subtilis powder (2 g), pH (6), standing time (36 h), and reaction temperature (25 °C) in the medium solution (100 mL). The average particle size of Ni3(PO4)2·8H2O was 80.51 nm, which was calculated by the Scherrer formula. The Lorentz-Transmission Electron Microscope (L-TEM) further showed that Ni3(PO4)2·8H2O was composed of clusters of irregular nanoparticles, and the individual particle size was in the range of 40-90 nm. The TGA curve shows that the mass loss of crystal water was 25.45%, which was close to the theoretical total mass loss of 28.24% in bio-Ni3(PO4)2·8H2O.


Assuntos
Níquel , Águas Residuárias , Adsorção , Galvanoplastia , Organofosfatos , Fosfatos
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