Rapid removal of lead(II) ions from water using iron oxide–tea waste nanocomposite – a kinetic study

Lead (Pb) ions are a major concern to the environment and human health as they are contemplated cumulative poisons. In this study, facile synthesis of magnetic iron oxide–tea waste nanocomposite is reported for adsorptive removal of lead ions from aqueous solutions and easy magnetic separation of the adsorbent afterwards. The samples were characterised by scanning electron microscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction, and Braunner–Emmet–Teller nitrogen adsorption study. Adsorptive removal of Pb(II) ions from aqueous solution was followed by ultraviolet–visible (UV–Vis) spectrophotometry. About 95% Pb(II) ion removal is achieved with the magnetic tea waste within 10 min. A coefficient of regression R ²  ≃ 0.99 and adsorption density of 18.83 mg g⁻¹ was found when Pb(II) ions were removed from aqueous solution using magnetic tea waste. The removal of Pb(II) ions follows the pseudo‐second‐order rate kinetics. External mass transfer principally regulates the rate‐limiting phenomena of adsorption of Pb(II) ions on iron oxide–tea waste surface. The results strongly imply that magnetic tea waste has promising potential as an economic and excellent adsorbent for the removal of Pb(II) from water.Inspec keywords: visible spectra, scanning electron microscopy, mass transfer, ultraviolet spectra, X‐ray diffraction, nanocomposites, lead, adsorption, magnetic separation, iron compounds, nanofabrication, Fourier transform infrared spectraOther keywords: FeO, Pb, time 10.0 min, X‐ray diffraction, Fourier transform‐infrared spectroscopy, scanning electron microscopy, adsorbent, magnetic separation, rapid removal, Braunner–Emmet–Teller nitrogen adsorption, iron oxide–tea waste surface, magnetic tea waste, aqueous solution, adsorptive removal, magnetic iron oxide–tea waste nanocomposite, lead(II) ions     

First principle study of the self‐switching characteristics of the guanine based single optical molecular switch using carbon nanotube electrodes

The switching property of an optical single molecular switch based on a single DNA molecule guanine with a single walled carbon nanotube electrode has been investigated using density functional theory along with non‐equilibrium Green''s function based first principle approach. The semi‐empirical model of this single bio‐molecular switch has been operated at an ultra‐high 25 THz frequency in mid‐UV range. This single bio‐molecule comprises switching activity upon UV photo‐excitation. The influence of the highest occupied molecular orbital and lowest unoccupied molecular orbital gap and the quantum ballistic transmission into the switching activity are discussed in detail in this study. It has been observed that the maximum ON–OFF ratio, i.e. 327 is obtained at +0.8 V bias voltage. Theoretical results show that current through the twisted form is sufficiently larger than the straightened form, which recommends that this structure has smart prospective application in the future generation switching nanotechnology.Inspec keywords: molecular electronic states, density functional theory, ab initio calculations, DNA, organic compounds, molecular electronics, Green''s function methods, molecular biophysics, single‐wall carbon nanotubes, optical switches, orbital calculationsOther keywords: nonequilibrium Green''s function, semiempirical model, single bio‐molecular switch, UV photo‐excitation, lowest unoccupied molecular orbital gap, first principle study, single optical molecular switch, switching property, optical single molecular switch, single DNA molecule guanine, single walled carbon nanotube electrode, density functional theory, highest occupied molecular orbital gap, switching nanotechnology     

Removal of toxic zinc from water/wastewater using eucalyptus seeds activated carbon: non‐linear regression analysis

In the present study, a novel activated carbon was prepared from low‐cost eucalyptus seeds, which was utilised for the effectively removal of toxic zinc from the water/wastewater. The prepared adsorbent was studied by Fourier transform infrared spectroscopy and scanning electron microscopic characterisation studies. Adsorption process was experimentally performed for optimising the influencing factors such as adsorbent dosage, solution pH, contact time, initial zinc concentration, and temperature for the maximum removal of zinc from aqueous solution. Adsorption isotherm of zinc removal was ensued Freundlich model, and the kinetic model ensued pseudo‐second order model. Langmuir monolayer adsorption capacity of the adsorbent for zinc removal was evaluated as 80.37 mg/g. The results of the thermodynamic studies suggested that the adsorption process was exothermic, thermodynamically feasible and impulsive process. Finally, a batch adsorber was planned to remove zinc from known volume and known concentration of wastewater using best obeyed model such as Freundlich. The experimental details showed the newly prepared material can be effectively utilised as a cheap material for the adsorption of toxic metal ions from the contaminated water.Inspec keywords: wastewater treatment, activated carbon, zinc, toxicology, regression analysis, Fourier transform infrared spectra, scanning electron microscopy, adsorption, pH, reaction kinetics, monolayers, thermodynamics, contaminationOther keywords: Zn, toxic metal ion adsorption, contaminated water, batch adsorber, exothermic process, thermodynamic process, Langmuir monolayer adsorption capacity, pseudosecond‐order model, kinetic model, Freundlich model, adsorption isotherm, aqueous solution, temperature value, initial zinc concentration, contact time, pH value, adsorbent dosage, scanning electron microscopic characterisation, Fourier transform infrared spectroscopy, nonlinear regression analysis, eucalyptus seed activated carbon, wastewater, toxic zinc removal     

Comprehensive analysis of retroreflection in Papilio crino Fabricius, 1792 wings

Multilayer thin‐film structures in the wings of a butterfly; Papilio crino produce a colourful iridescence from reflected light. In this investigation, scanning electron microscope images show both the concave cover scales and pigmented air‐chamber ground scales. The microstructures with the concavities retroreflect incident light, thus causing the double reflection. This gives rise to both the colour mixing and polarisation conversion clearly depicted in the optical images. The result of the numerical and theoretical analysis via the CIELAB, and optical reflection and transmission of light through the multilayer stacks with the use of transfer method show that the emerging colouration on the Papilio crino is structural and is due to the combination of colours caused by multiple bounces within the concavities. The butterfly wing structure can be used as the template for designing the photonic device.Inspec keywords: bio‐optics, scanning electron microscopy, photodiodes, optical sensors, optical images, light reflection, reflectivity, colour, optical links, multilayers, optical multilayers, light polarisationOther keywords: pigmented air‐chamber ground scales, concavities, incident light, double reflection, colour mixing, polarisation conversion, optical images, numerical analysis, theoretical analysis, optical reflection, multilayer stacks, emerging colouration, butterfly wing structure, papilio crino fabricius, thin‐film structures, colourful iridescence, reflected light, electron microscope images, concave cover scales     

Adsorption of direct dye on palm ash: kinetic and equilibrium modeling

Palm ash, an agriculture waste residue from palm-oil industry in Malaysia, was investigated as a replacement for the current expensive methods of removing direct blue 71 dye from an aqueous solution. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with Freundlich model in the range of 50-600mg/L. The equilibrium adsorption capacity of the palm ash was determined with the Langmuir equation and found to be 400.01mg dye per gram adsorbent at 30 degrees C. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The results indicate that the palm ash could be employed as a low-cost alternative to commercial activated carbon.     

Recyclable adsorbents based on Fe3 O4 nanoparticles on lanthanum‐modified montmorillonite for the efficient phosphate removal

Montmorillonite (MMT) clay modified with lanthanum (La) ions and Fe₃ O₄ nanoparticles was proposed for the effective removal of phosphate ions from aqueous solution. Characterisation of the adsorbent using FTIR, SEM, XRD, XPS, XRF, BET and VSM techniques were carried out. The effects of initial phosphate concentration, contact time, dosage and pH on the phosphorus adsorption were investigated. La‐MMT/Fe₃ O₄ exhibited an excellent adsorption capacity of up to 14.35 mg/g, with 97.8% removal within 60 min. Langmuir isotherm model fits well with the equilibrium isotherm data, with a maximum adsorption capacity of 15.53 mg/g at room temperature. The kinetic study was well fitted with pseudo‐second‐order kinetics, and the adsorption rate was mainly controlled by liquid‐film diffusion. The manufactured adsorbent was effectively regenerated using 0.1 M NaOH solutions, with 90.18% adsorption efficiency remaining after six adsorption/desorption cycles. These results demonstrate that La‐MMT/Fe₃ O₄ provides an example of regenerable high‐performance adsorbents for removal of PO₄ ³⁻ from wastewater.Inspec keywords: wastewater treatment, desorption, phosphorus, pH, recycling, adsorption, X‐ray diffraction, iron compounds, nanoparticles, X‐ray photoelectron spectra, clay, scanning electron microscopy, reaction kinetics theory, X‐ray fluorescence analysis, chemical engineering, chemical equilibrium, Fourier transform infrared spectra, sodium compounds, lanthanum, liquid films, diffusionOther keywords: maximum adsorption capacity, high‐performance adsorbents, recyclable adsorbents, lanthanum‐modified montmorillonite, montmorillonite clay, Langmuir isotherm model, phosphate removal, aqueous solution, FTIR spectroscopy, SEM, XRD, XPS, XRF, BET, VSM techniques, pH value, equilibrium isotherm data, pseudo second‐order kinetics, liquid‐film diffusion, adsorbent regeneration, adsorption‐desorption cycles, wastewater treatment, temperature 293.0 K to 298.0 K, time 60.0 min, NaOH, La, P     

Metal nanoparticles synthesis through natural phenolic acids

For being applied in medicine as therapeutic agents, nanostructures need to be biocompatible and eco‐friendly. Plant‐derived phenolic acids have been utilised for green synthesis of metallic or metallic oxide nanoparticles (NPs). The phenolic acids play role as both reducing agents and stabilisers in the process of NPs synthesis. Many experiments have been dedicated to develop efficient green synthesis techniques for producing metal NPs. Using phenolic acids represents a reproducible, simple, profitable, and cost‐effective strategy to synthesise metal NPs. As a phytochemical for metal NPs synthesis, phenolic acids are antioxidants that represent many health benefits. However, limited studies have been dedicated to the synthesis and characterisation of NPs produced by phenolic acids. Thus, this review focused on phenolic acids mediated nanomaterial synthesis and its biomedical applications. It should be noted the mechanism of metal ion bioreduction, phenolic acids surface adsorption, characterisation, and toxicity of metal NPs made with different phenolic acids have been discussed in this review.Inspec keywords: bio‐inspired materials, organic compounds, adsorption, nanofabrication, nanoparticles, biomedical materials, nanomedicineOther keywords: toxicity, biomedical applications, antioxidants, phytochemical synthesis, reducing agents, therapeutic agents, medicine, metallic oxide nanoparticles, plant‐derived phenolic acids, natural phenolic acids, metal nanoparticles synthesis, phenolic acids surface adsorption, metal ion bioreduction, nanomaterial synthesis, efficient green synthesis techniques     

A comparative investigation on adsorption performances of mesoporous activated carbon prepared from waste rubber tire and activated carbon for a hazardous azo dye--Acid Blue 113

A mesoporous carbon developed from waste tire rubber, characterized by chemical analysis, FTIR, and SEM studies, was used as an adsorbent for the removal and recovery of a hazardous azo dye, Acid Blue 113. Surface area, porosity, and density were determined. The adsorption of the dye over the prepared adsorbent and a commercial activated carbon was achieved under different pH, adsorbate concentration, sieve size, adsorbent dosage, contact time and temperature conditions. Langmuir and Freundlich adsorption isotherm models were applied and thermodynamic parameters were calculated. Kinetic studies indicated that the adsorption process follow first order kinetics and particle diffusion mechanisms are operative. By percolating the dye solution through fixed-bed columns the bulk removal of the Acid Blue 113 was carried out and necessary parameters were determined to find out the percentage saturation of both the columns. Recovery of the dye was made by eluting 0.1 M NaOH through the column.     

Small‐sized probe for local measuring electrical properties of the tissues inside of human body: design,modelling and simulation

In this study, a new idea is suggested for designing an appropriate bio‐impedance probe in the form of a biopsy forceps to measure the electrical properties of the tissues inside the body. First, by analytically solving the Laplace equation for wedge‐shaped tissue in the mouth of the probe, the relationship between electric potential (results from excitation current) in a different point on the tissue and the electrical properties of the tissue is obtained. Then, to evaluate the designed bio‐impedance probe using the finite element method and the experimental data obtained for different tissues by Gabriel et al., modelling and simulation at different frequencies from 50 Hz to 5 MHz were done. Finally, to evaluate the performance of the designed probe in comparison to other methods, measurements were carried out using three methods for the same tissue. Nyquist curves were drawn and electrical properties extracted for all the three methods. It was found that the designed probe results are close to the actual values with an error of <2%. The main features of the designed probe are small size and non‐invasive measurement.Inspec keywords: Laplace equations, biological tissues, finite element analysis, electric impedance measurement, bioelectric potentials, biomedical measurementOther keywords: noninvasive measurement, local measuring electrical properties, human body, wedge‐shaped tissue, electric potential, finite element method, bio‐impedance probe, small‐sized probe, biopsy forceps, excitation current, Nyquist curves, frequency 50.0 Hz to 5.0 MHz     

Synthesis and application of alginate immobilised banana peels nanocomposite in rare earth and radioactive minerals removal from mine water

This study describes the preparation, characterisation and application of pelletised immobilised alginate/montmorillonite/banana peels nanocomposite (BPNC) in a fixed‐bed column for continuous adsorption of rare earth elements and radioactive minerals from water. The materials was characterised by Fourier transform infrared, X‐ray diffraction and scanning electron microscopy analyses. Analyses indicated that the pellets are porous and spherical in shape. FT‐IR analysis showed that the functional groups responsible for the coordination of metal ions were the carboxylic (–COO–) and siloxane (Si–O–Si and Si–O–Al) groups. XRD analysis showed two additional peaks which were attributed to alginate and montmorillonite. The influence of the initial concentration, bed depth and flow rate were investigated using synthetic and real mine water in order to determine the breakthrough behaviour of both minerals. The processed bed volume, adsorbent exhaustion rate and service time, were also explored as performance indices for the adsorbent material. Furthermore, the breakthrough data were fitted to both the Thomas and Bohart–Adams models. The BPNC exhibited high affinity for U, Th, Gd and La in the real mine water sample. However, studies may still be required using waters from different environments in order to determine the robustness of BPNC.Inspec keywords: scanning electron microscopy, nanocomposites, chemical technology, X‐ray diffraction, minerals, adsorption, wastewater treatment, Fourier transform infrared spectra, hazardous materials, nanofabrication, waste recovery, recycling, uranium, thorium, gadolinium, lanthanumOther keywords: fixed‐bed column, rare earth elements, adsorption process, microstructural analysis, bed depth, flow rate, processed bed volume, adsorbent exhaustion rate, mine water sample, X‐ray diffraction analysis, scanning electron microscopy analyses, siloxane group, pelletised immobilised alginate‐montmorillonite‐banana peels nanocomposite, radioactive mineral removal, Fourier transform infrared spectroscopy, carboxylic group, Thomas model, Bohart–Adams model, U, Th, Gd, La     

Synthesised magnetic nano‐zeolite as a mycotoxins binder to reduce the toxicity of aflatoxins,zearalenone, ochratoxin A,and deoxynivalenol in barley

Agricultural commodities, particularly cereals can be contaminated with mycotoxins during the pre‐ and post‐harvest stage. The main goal of this study was to evaluate the efficacy of magnetic zeolite nanocomposite (MZNC) as an adsorbent for the reduction of mycotoxins in barley flour. The MZNC is synthesised using an eco‐friendly and efficient procedure and characterised by zeta potential, field emission scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. The adsorbent amount that affects the adsorption capacity was optimised. Low amounts of the nanocomposite removed >99% of aflatoxins, 50% of ochratoxin A, 22% of zearalenone, and 1.8% of the deoxynivalenol from the contaminated sample and adsorption by MZNC was better than the natural zeolite; this phenomenon is related to the wide surface of nanocomposites. Results provide new insights into possible future research that could overcome the challenges of using nanotechnology to eliminate mycotoxins from agricultural products. It can be hoped that the presence of cheap and eco‐friendly mycotoxin binders such as the MZNC that is synthesised and utilised in this research will help to produce secure food and feed products.Inspec keywords: toxicology, field emission electron microscopy, zeolites, scanning electron microscopy, adsorption, X‐ray chemical analysis, nanotechnology, nanocomposites, agricultural products, contaminationOther keywords: synthesised magnetic nanozeolite, mycotoxins binder, zearalenone, deoxynivalenol, ochratoxin A, agricultural commodities, cereals, post‐harvest stage, magnetic zeolite nanocomposite, MZNC, barley flour, zeta potential field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, adsorption capacity, natural zeolite, agricultural products, eco‐friendly mycotoxin binders, aflatoxins, toxicity     

Biogenic synthesis and thermo‐magnetic study of highly porous carbon nanotubes

Nanomaterials synthesis using natural sources is the technology to up come with advanced materials through extracts of plant, microorganisms, poultry waste etc. In this study, the authors report the synthesis of porous carbon nanotubes using high‐temperature decomposition technique facilitated by cobalt salt using chicken fats, a poultry waste as a precursor. Since chicken fats contain fatty acids which can decompose into short hydrocarbon chains and cobalt can act as the catalyst. The formation of carbon nanotubes was confirmed by Raman spectra, peaks at 1580 and 1350.46 cm⁻¹ confirmed the graphite mode G‐band and structural imperfections defect mode D‐band, respectively. Transmission electron microscopy showed the formation of tube‐like structures. Nitrogen adsorption–desorption studies showed the high‐surface area of 418.1 m² g⁻¹ with an estimated pore diameter of 8.1 nm. Thermogravimetry analysis–derivative thermogravimetric analysis–differential thermal analysis showed the instant weight loss at 517°C attributed to the rapid combustion of nanotubes. A vibrating‐sample magnetometer showed the paramagnetic nature of the so‐formed carbon nanotubes formed.Inspec keywords: transmission electron microscopy, infrared spectra, nanomagnetics, pyrolysis, decomposition, adsorption, desorption, carbon nanotubes, differential thermal analysis, thermal analysis, nanofabrication, Raman spectra, X‐ray diffraction, scanning electron microscopy, paramagnetic materialsOther keywords: biogenic synthesis, highly porous carbon nanotubes, microorganisms, high‐temperature decomposition technique, cobalt salt, chicken fats, fatty acids, short hydrocarbon chains, Raman spectra, graphite mode G‐band, structural imperfections defect mode D‐band, transmission electron microscopy, paramagnetic nature, thermo‐magnetic properties, poultry waste, nitrogen adsorption‐desorption studies, thermogravimetry analysis, differential thermal analysis, carbon nanotubes, temperature 517.0 degC, C     

Multi‐bit Boolean model for chemotactic drift of Escherichia coli

Dynamic biological systems can be modelled to an equivalent modular structure using Boolean networks (BNs) due to their simple construction and relative ease of integration. The chemotaxis network of the bacterium Escherichia coli (E. coli ) is one of the most investigated biological systems. In this study, the authors developed a multi‐bit Boolean approach to model the drifting behaviour of the E. coli chemotaxis system. Their approach, which is slightly different than the conventional BNs, is designed to provide finer resolution to mimic high‐level functional behaviour. Using this approach, they simulated the transient and steady‐state responses of the chemoreceptor sensory module. Furthermore, they estimated the drift velocity under conditions of the exponential nutrient gradient. Their predictions on chemotactic drifting are in good agreement with the experimental measurements under similar input conditions. Taken together, by simulating chemotactic drifting, they propose that multi‐bit Boolean methodology can be used for modelling complex biological networks. Application of the method towards designing bio‐inspired systems such as nano‐bots is discussed.Inspec keywords: cell motility, microorganisms, Boolean functionsOther keywords: multibit Boolean approach, conventional BNs, high‐level functional behaviour, steady‐state responses, chemoreceptor sensory module, drift velocity, chemotactic drifting, multibit Boolean methodology, complex biological networks, bio‐inspired systems, multibit Boolean model, chemotactic drift, dynamic biological systems, equivalent modular structure, Boolean networks, simple construction, chemotaxis network, bacterium Escherichia coli, biological systems     

Removal of phenol from aqueous solution and resin manufacturing industry wastewater using an agricultural waste: rubber seed coat.

Activated carbon prepared from rubber seed coat (RSCC), an agricultural waste by-product, has been used for the adsorption of phenol from aqueous solution. In this work, adsorption of phenol on rubber seed coat activated carbon has been studied by using batch and column studies. The equilibrium adsorption level was determined to be a function of the solution pH, adsorbent dosage and contact time. The equilibrium adsorption capacity of rubber seed coat activated carbon for phenol removal was obtained by using linear Freundlich isotherm. The adsorption of phenol on rubber seed coat activated carbon follows first order reversible kinetics. The suitability of RSCC for treating phenol based resin manufacturing industry wastewater was also tested. A comparative study with a commercial activated carbon (CAC) showed that RSCC is 2.25 times more efficient compared to CAC based on column adsorption study for phenolic wastewater treatment.     

Synthesis of Co3 O4 /graphene nanocomposite using paraffin wax for adsorption of methyl violet in water

This study discusses the use of Co₃ O₄ impregnated graphene (CoOIG) as an efficient adsorbent for the removal of methyl violet (MV) dye from wastewater. CoOIG nanocomposites have been prepared by pyrolyzing paraffin wax with cobalt acetate. The synthesised nanocomposite was characterised by X‐ray diffraction, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscope, Raman spectroscopy, and Brunauer–Emmett–Teller isotherm studies. The above studies indicate that the composites have cobalt oxide nanoparticles of size 51–58 nm embedded in the graphene nanoparticles. The adsorption studies were conducted with various parameters, pH, temperature and initial dye concentration, adsorbent dosage and contact time by the batch method. The adsorption of MV dye by the adsorbent CoOIG was about 90% initially at 15 min and 98% dye removal at pH 5. The data were fitted in Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich and Sips isotherm models. Various thermodynamic parameters like Gibbs free energy, enthalpy, and entropy of the on‐going adsorption process have also been calculated.Inspec keywords: cobalt compounds, graphene, nanoparticles, nanocomposites, nanofabrication, adsorption, dyes, scanning electron microscopy, field emission electron microscopy, transmission electron microscopy, Raman spectra, Fourier transform infrared spectra, free energy, enthalpy, entropyOther keywords: nanocomposite, paraffin wax, adsorption, methyl violet dye, water, X‐ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer‐Emmett‐Teller isotherm, cobalt oxide nanoparticles, graphene nanoparticles, thermodynamic parameters, Gibbs free energy, enthalpy, entropy, Co₃ O₄ ‐C     

Construction of active bio‐nanocomposite by inseminated metal nanoparticles onto activated carbon: probing to antimicrobial activity

The bio‐nanocomposite role in wastewater treatment is a primary concern of this research. The physical, chemical, mechanical stability and antimicrobial activity of these bio‐nanocomposites were investigated. The method is based on the biological reduction of aqueous copper sulphate pentahydrate, lead nitrate, silver nitrate, zinc sulphate heptahydrate salt using seed extract of Eucalyptus globulus as reducing agent at ambient temperature. The synthesised metal nanoparticles (MNPs) were analysed by UV‐visible spectroscopy and Fourier transform infrared spectroscopy analyses. An ex‐situ method involves constructing bio‐nanocomposite by blending MNPs with tea waste activated carbon. Cross‐linking in activated carbon takes place which was confirmed by changes in the mixture of components. The present yield of activated carbon was characterised by scanning electron microscopy and energy dispersive X‐ray measurements. A few micro or nano range, spherical shape of activated carbon was studied by SEM. The main elements found in the activated carbon by EDX are C, O, S, Ag, Cl and Cu. The efficacy of such active bio‐nanocomposite (ABN) tested against human pathogen includes both type of bacteria and fungus. The inhibitory effects of ABN are discernible from the results that reveal biologically inseminated MNPs can be used to clean up the contaminated environment.Inspec keywords: nanocomposites, activated carbon, wastewater treatment, copper compounds, nitrogen compounds, Fourier transform infrared spectra, scanning electron microscopyOther keywords: active bio‐nanocomposite, inseminated metal nanoparticles, activated carbon, antimicrobial activity, wastewater treatment, mechanical stability, biological reduction, aqueous copper sulphate pentahydrate, lead nitrate, silver nitrate, zinc sulphate heptahydrate salt, Eucalyptus globulus, synthesised metal nanoparticle, MNP, UV‐visible spectroscopy, Fourier transform infrared spectroscopy analysis, scanning electron microscopy, energy dispersive X‐ray measurement, SEM     

Extracellular biosynthesis of biocompatible CdSe quantum dots

An extracellular biosynthesis method has been developed to prepare cadmium selenide (CdSe) quantum dots (QDs) with strong fluorescence emission by incubating cheap Cd and Se inorganic salts with Escherichia coli (E.coli) bacteria. Ultraviolet–visible absorption spectra, photoluminescence (PL) spectra, and high‐resolution transmission electron microscopy analysis showed that the biosynthesised CdSe QDs have an average size of 3.1 nm, the excellent optical properties with fluorescence emission around 494 nm, and the good crystallinity. It was found that addition of 80 mg of mercaptosuccinic acid resulted in the formation of CdSe QDs with highest PL intensity. Furthermore, Fourier‐transform infrared spectra of as‐synthesised CdSe QDs confirmed the presence of a surface protein capping layer. The biosynthesised CdSe QDs were incorporated into the yeast cells as illustrated by laser confocal scanning microscopy images, showing a great potential in bio‐imaging and bio‐labelling application.Inspec keywords: microorganisms, molecular biophysics, fluorescence, visible spectra, nanofabrication, nanobiotechnology, proteins, cellular biophysics, nanostructured materials, wide band gap semiconductors, cadmium compounds, semiconductor quantum dots, II‐VI semiconductors, transmission electron microscopy, photoluminescence, optical microscopy, ultraviolet spectra, Fourier transform infrared spectra, biological techniques, semiconductor growthOther keywords: biocompatible CdSe quantum dots, extracellular biosynthesis method, cadmium selenide quantum dots, high‐resolution transmission electron microscopy analysis, biosynthesised CdSe QDs, Fourier‐transform infrared spectra, Escherichia coli, ultraviolet‐visible absorption spectra, PL intensity, fluorescence emission, photoluminescence spectra, optical properties, surface protein capping layer, laser confocal scanning microscopy images, bioimaging, biolabelling application, yeast cells, f mercaptosuccinic acid, CdSe     

Adsorptive studies of hazardous dye Tropaeoline 000 from an aqueous phase on to coconut-husk

This contribution presents result pertaining to the adsorptive removal of water-soluble hazardous dye Tropaeoline 000, on to a low cost adsorbent-coconut-husk and its efficiency in the dye colour sorption was compared with activated carbon (AC). The results obtained from the batch experiments revealed the ability of the coconut-husk to remove the Tropaeoline 000 dye. The adsorption of dye was carried out at different pH, temperatures, amount of adsorbent, contact time, concentration of adsorbate (initial dye concentration) and particle size. The adsorption studies revealed that the ongoing adsorption validates both Langmuir and Freundlich adsorption isotherm at temperatures 30, 40 and 50 degrees C. The adsorption isotherm data was also employed to calculate thermodynamic parameters like DeltaG degrees , DeltaH degrees and DeltaS degrees . The negative values of DeltaG degrees indicate that the dye adsorption process is a spontaneous in nature. The positive value of DeltaH degrees shows the endothermic nature of AC/coconut-husk system whereas negative value of DeltaH degrees indicates that the exothermic nature of AC/coconut-husk. The adsorption was found to undergo via a pseudo-second order adsorption kinetics and the results revealed that coconut-husk, an agricultural waste, proved to be an excellent low cost adsorbent.     

The adsorption of basic dye (Astrazon Blue FGRL) from aqueous solutions onto sepiolite, fly ash and apricot shell activated carbon: kinetic and equilibrium studies

In this study, sepiolite, fly ash and apricot stone activated carbon (ASAC) were used as adsorbents for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the basic dye (Astrazon Blue FGRL) from aqueous solutions at various concentrations (100-300 mg/L), adsorbent doses (3-12 g/L) and temperatures (303-323 K). The result showed that the adsorption capacity of the dye increased with increasing initial dye concentration, adsorbent dose and temperature. Three kinetic models, the pseudo-first-order, second-order, intraparticle diffusion, were used to predict the adsorption rate constants. The kinetics of adsorption of the basic dye followed pseudo-second-order kinetics. Equations were developed using the pseudo-second-order model which predicts the amount of the basic dye adsorbed at any contact time, initial dye concentration and adsorbent dose within the given range accurately. The adsorption equilibrium data obeyed Langmuir isotherm. The adsorption capacities (Q0) calculated from the Langmuir isotherm were 181.5 mg/g for ASAC, 155.5 mg/g for sepiolite and 128.2 mg/g for fly ash at 303 K. Thermodynamical parameters were also evaluated for the dye-adsorbent systems and revealed that the adsorption process was endothermic in nature.     

Electrochemical assessment of the interaction of microbial living cells and carbon nanomaterials

This work considers the effects of various carbon nanomaterials and fibres on bioelectrocatalytic and respiratory activity of bacterial cells during the oxidation of ethanol in the presence of an electron transport mediator. Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells were immobilised on the surfaces of graphite electrodes and had an adsorption contact with a nanomaterial (multi‐walled carbon nanotubes, thermally expanded graphite, highly oriented pyrolytic graphite, graphene oxide, reduced graphene oxide). The electrochemical parameters of the electrodes (the polarisation curves, the value of generated current at the introduction of substrate, the impedance characteristics) were measured in two‐electrode configuration. Modification by multi‐walled carbon nanotubes led to the increase of microbial fuel cell (MFC) electric power by 26%. The charge transfer resistance of modified electrodes was 47% lower than unmodified ones. Thermally expanded and pyrolytic graphites had a slight negative effect on the electrochemical properties of modified electrodes. The respiratory activity of bacterial cells did not change in the presence of nanomaterials. The data can be used in the development of microbial biosensors and MFC electrodes based on Gluconobacter cells.Inspec keywords: nanofabrication, catalysis, microorganisms, adsorption, charge exchange, microbial fuel cells, electrochemical electrodes, graphite, graphene, oxidation, multi‐wall carbon nanotubes, cellular biophysicsOther keywords: reduced graphene oxide, electrochemical parameters, two‐electrode configuration, multiwalled carbon nanotubes, microbial fuel cell, respiratory activity, bacterial cells, microbial biosensors, MFC electrodes, microbial living cells, electron transport mediator, graphite electrodes, adsorption contact, highly oriented pyrolytic graphite, Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells, polarisation curves, bioelectrocatalytic activity, ethanol, thermally expanded graphite, charge transfer resistance, C