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In this work, the treatment efficiency of advanced oxidation processes H2O2/UV enhanced by the addition of a manganese catalyst complex (MnTACN) was investigated on a model dye solution and a real dye-house effluent. The experimental results were evaluated in terms of absorbance (A) and total organic carbon (TOC) reduction. The major degradation products of the model dye solution were identified by high resolution gas chromatography/mass spectrometry analyses. In addition, the toxicity of the final reaction solution after H2O2/UV/MnTACN treatment to Vibrio fischeri bacteria was determined. The results showed that the addition of the H2O2/UV/MnTACN system at in different concentrations of the catalyst solution increased enhance the decolourization rate compared to H2O2/UV for both the model dye solution and real dye-house effluent.

In this paper, a circular economy approach with the adsorption and desorption of heavy metal (HM) ions-i.e., lead (Pb

The objective of this study was to determine the density of anaerobic granules on different heights of a full-scale Upflow Anaerobic Sludge Bed reactor. The density was defined through the settling velocities of anaerobic granules, measured in a full-scale Upflow Anaerobic Sludge Bed reactor. In this study, granular density was calculated with the measured settling velocities and developed mathematical model. The developed mathematical model is based on the Stokes model. In the experiment, granules were taken from different heights of an Upflow Anaerobic Sludge Bed reactor, from 0.6 to 7.6 m. The granules’ diameters varied between 1 and 5 mm. The granules were taken from six different heights through the reactor. The settling velocity of the active granules (with gas in the granule pore and on the surface of the granule) was measured first. After the active granules’ settling velocity measurement, the granules were placed in a vortex to obtain degassed granules (granules without any gas in the pores or on the surface), for which the settling velocities were also measured later. It is shown that granules’ densities at different heights are independent of the reactor height.

Cellulose containing textiles (cotton) and cardboard/carton-based wastes represent a large pool of untapped organic carbon. These wastes have enormous potential for utilization as carbon feedstocks in industrial biotechnology processes. Essentially, cotton/cardboard (CC) waste is pure cellulose (with some additives) in the form of polymerised glucose composed of β (1→4) linked D-glucose subunits. CC waste materials can be enzymatically hydrolysed to monomers of D-glucose in aqueous solution, to form ‘glucose juice’, which can then be fermented to bio-ethanol. In principle, value added chemicals could also be produced from glucose juice. Bioconversion of CC waste to other compounds of importance to industry could form the basis of environmentally attractive production routes. Terpenes are one of the largest and most diverse classes of natural compounds, and are of value to industry as they have a wide range of applications as flavourings, fragrances, pharmaceuticals, bio-pesticides and biofuels. Here, we investigated the bioconversion of CC waste to the exemplar terpene limonene as a proof-of-concept. Six different CC waste streams were enzymatically hydrolysed to glucose juice and used to produce limonene by fermentation of an engineered E. coli microbial cell factory. D-glucose content was determined in the glucose juice, and then metabolized by E. coli using an engineered heterogenic biolipid synthesis pathway (the mevalonate pathway) to produce limonene (300–700 mg L− 1), which was then partitioned into a nonane overlay. This study establishes an important proof-of-concept for terpene production from hydrolysed CC waste streams.

In this paper, a circular economy approach with the adsorption and desorption of heavy metal (HM) ions—i.e., lead (Pb2+), chromium (CrT), and mercury (Hg2+)—from aqueous solutions was studied. Specific and selective binding of HM ions was performed on stabilized and amino-functionalized iron oxide magnetic nanoparticles (γ-Fe2O3@NH2 NPs) from an aqueous solution at pH 4 and 7. For this purpose, γ-Fe2O3@NH2 NPs were characterized by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), specific surface area (BET), transmission electron microscopy (TEM), EDXS, and zeta potential measurements (ζ). The effects of different adsorbent amounts (mads = 20/45/90 mg) and the type of anions (NO3−, Cl−, SO42−) on adsorption efficiency were also tested. The desorption was performed with 0.1 M HNO3. The results showed improvement of adsorption efficiency for CrT, Pb2+, and Hg2+ ions at pH 7 by 45 mg of g-Fe2O3@NH2 NPs, and the sequence was as follows: CrT > Hg2+ > Pb2+, with adsorption capacities of 90.4 mg/g, 85.6 mg/g, and 83.6 mg/g, respectively. The desorption results showed the possibility for the reuse of γ-Fe2O3@NH2 NPs with HNO3, as the desorption efficiency was 100% for Hg2+ ions, 96.7% for CrT, and 91.3% for Pb2+.

A new circular economy concept is presented for the textile sector to convert unwearable polyester textile waste into valuable chemical feedstock. The idea behind it is to develop a new circular economy concept for the most used material in the textile industry, that is, polyester. Hydrothermal hydrolysis, an environmentally friendly process, has been studied for recovering polyester monomeric units. Under high-temperature and high-pressure conditions complete chemical depolymerization of pure poly(ethylene terephthalate) (PET) to terephthalic acid (TPA) was achieved at high yield. The produced TPA was characterized by potentiometric titrations, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and elemental analysis. A series of experiments were performed on the PET material with different intrinsic viscosities to define the appropriate depolymerization conditions related to the temperature ( T), time ( t) and PET:H2O ratio, which enables total conversion of the polymer. Maximal conversion (92%) to TPA was defined at 250℃, pressure of 39–40 bar, PET:water ratio of 1:10 and hydrolysis time of 30 min after reaching steady-state conditions in the reactor. The applied depolymerization route resulted in moderate purity of the originated TPA, which was applied successfully in a laboratory-scale two-step re-polymerization to produce PET resins.

Herein, we present a simple modified hard-template approach for the fabrication of uniform superparamagnetic hollow maghemite ( $\gamma $ -Fe2O3) spheres. Hollow spheres were prepared by the attachment of ferric and ferrous ions onto the surface of the spherical silica (SiO2) particles synthesized by the Stober process. The synthesis consisted of four major steps. In the first step, monodispersed spherical silica particles with a narrow size distribution of around (497.5 ± 4.5) nm were prepared as hard templates. Second, Fe2+/Fe3+ ions were adsorbed onto the surface of the SiO2 particles in the aqueous solution. In the third step, Fe2+/Fe3+ ions at the SiO2 surface slowly nucleated and crystallized in the form of spinel $\gamma $ -Fe2O3 nanoparticles. SiO2 templates were dissolved simultaneously when [NaOH/NaHCO3] (pH 11) and [Na2CO3/NaHCO3] (pH 9) buffer solutions were added successively until the reaction medium reached pH of 3.0 ± 0.1. In the fourth step, the addition of an alkali solution accelerated the crystallization and formation of $\gamma $ -Fe2O3 nanocrystallites via the precipitation mechanism. The formation of the hollow spherical structures and their morphology were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The crystallinity and the phase analysis of the samples were characterized by means of X-ray powder diffractometry [X-ray diffraction (XRD)] and Fourier-transform infrared (FTIR) spectroscopy. The specific surface area and the specific magnetization of the prepared samples were also defined. It is important to note that the third step presents a novel approach [Patent GB 2526659] for the preparation of superparamagnetic hollow spheres, avoiding high temperatures of calcination or environmentally questionable etching, which usually employ strong solvents and acids. Consequently, our synthesis is faster, more economical and environmentally friendly when compared with other relevant procedures described in the literature.

Membrane technologies are a useful solution for water treatment, especially for removing trace amounts of different pollutants. Current research is focused on improving the removal efficiency of polyvinylidene fluoride (PVDF) membranes to heavy metal ions, such as lead(II), cadmium(II), and chromium(III). The surface chemistry and morphology of PVDF membranes were varied applying the sol–gel approach for functionalization. It involved (1) diethylphosphatoethyltriethoxysilane (DPTES) or 3-mercaptopropyltrimethoxysilane (MPTMS) as functionalizing precursors, (2) different concentrations of the initial sols, and (3) NH4OH or HCl as the catalysts for the hydrolysis and co-condensation reactions. According to the SEM analysis of the surface texture, alkaline catalyst and low sol concentration result in the formation of porous membrane active layers. Membrane weight loss after water filtration under pressure indicated the dependence of layer stability on the conditions of functionalization, namely the membranes with phosphonic groups prepared in an acidic medium are more resistant to rinsing. Functionalized PVDF membranes demonstrated a significant increase in sorption efficiency along with high water flux. Overall, such membranes were sufficient for treating water with ion concentrations lower than 100 mg/L, whereas the applied functionalization technique is promising for adjusting the parameters of the final membranes.

In this study, we developed hexagon silver nanoparticles (AgNPs) prepared by the polyol method in ethylene glycol media using aminopropyltrimethoxysilane (APTMS) as a capping agent for the first time. The presence of the primary amine group makes APTMS a great candidate as a capping agent for the synthesis of silver nanostructures, but it has not been used for this purpose until now. The synthesized silver nanostructures were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry and ultraviolet-visible spectroscopy. The molar ratio of APTMS to AgNO3 varied from 0.5 to 6.8, which resulted in an average diameter of the obtained nanoparticles from 50 to 100 nm. The optimum morphology of hexagonally shaped AgNPs was obtained at a molar ratio of 2.2. The prepared AgNPs were evaluated for their antibacterial and antifungal properties. Antimicrobial tests showed that a cotton textile coated with colloidal amino functionalized AgNPs has excellent antimicrobial properties as an inhibitor of growth against the gram-positive bacteria Staphylococcus aureus, gram-negative bacteria, Escherichia coli and fungus Candida albicans, and therefore showing potential for real applications.

The mesoporous silica samples with different concentrations of phosphonic acid groups on the surface were obtained by direct template synthesis. The block-copolymer Pluronic P123 was used as a template, and sodium meta-silicate with diethylphosphatoethyltriethoxysilane as precursors. According to the SAXS diffractograms, mesoporous silica samples have a p6mm hexagonal symmetry. In addition, we used sol–gel method to synthesize xerogel with the same groups for comparison. All samples possess high values of specific surface area 615–730 m2/g and sorption pore volume. FTIR and potentiometric titration methods were used to investigate the surface layer of these samples. Sorption properties of the samples with phosphonic acid groups were studied in respect to a row of metal cations, among which we focused on lead(II), cadmium(II), and dysprosium(III) cations.

A series of magnetic adsorbents was created by grafting selected functional ligands directly on the surface of iron oxide nanoparticles (NP). The produced materials were characterized by SEM-EDS, TEM, AFM, FTIR, XRD, Mossbauer spectroscopy, low temperature gas sorption, and in relation to functional properties. Each of the applied ligands carried two functional groups including phosphonic acid involved in grafting, and either alcohol, thiol, amino, carboxylic- or phosphonic acid. The kinetics and thermodynamics of metal cation adsorption were investigated for Rare Earth (REE, Sm3+, Nd3+, Dy3+ and Tb3+) and Late Transition Metals (LTM, Co2+ and Ni2+) as representative for the content of magnetic materials, requiring recycling. Long linear alkyl chain (C10-C12) and, in case of phosphonic acid, even a shorter one (C6), were used to trace potential stabilization of the particles against iron leaching on desorption of adsorbed cations in acidic medium. The NP demonstrated high adsorption capacity, efficient desorption and considerable selectivity in separation of REE from LTM. Modification with ligands offers appreciable protection of magnetic particles against iron leaching.

This study presents an optical chemical sensing system based on an SiO 2 sensor layer for continuous determination of biogenic amines (BAs), such as isopentylamine, propylamine and putrescine. For this purpose, the indicator dye ETH4001 was chosen and immobilized in different sol-gel sensor layers, which were prepared by various combinations of hydrophilic tetraethoxysilane and hydrophobic sol-gel precursors propyl-trimethoxysilane, and 3,3,3-trifluoropropyltrimethoxysilane. The preparation of the starting sol-gel solution containing the indicator ETH4001 was carried out via the acid-catalyzed process and at a constant molar ratio R = 7 in all cases. The sensing system was optimized according to spectral properties, dynamic range, sensitivity, response and regeneration time and sensor layer aging time.

In this work, mono-dispersed mercapto-functionalized silica (SiO2@SH) particles with a narrow particle size distribution of around (420 ± 10) nm were prepared by the sol–gel method for the adsorption of aqueous dissolved lead (Pb2 +) ions from modeled wastewater. Transmission Electron Microscopy (TEM), in combination with Energy-Dispersive X-ray Spectroscopy (EDXS), was used to obtain information about the particle size and morphology of the prepared samples. Dispersive X-ray Spectroscopy (EDXS) indicated strong signals of Si and S, implying successful completion after the mercapto ( SH) functionalization of the silica (SiO2) surfaces. Fourier Transform Infrared Spectroscopy (FTIR) was used to determine the occurrences of Si–O–Si and SH vibrations within the samples and, thus, come to a conclusion about the formations of the mercapto-functionalized samples. Analysis was performed of Pb2 + adsorption with mercapto-groups ( SH) on the surface of the SiO2@SH particles. The results for Pb2 + adsorptions from the modeled wastewater showed affinity of around 55% and the obtained value of the maximum amount of adsorbed Pb2 + ions with the SiO2@SH samples was 10.82 mg/g under the conditions used during this study. The results of the adsorptions were fitted with the Langmuir and Freundlich isotherm models and the pseudo-first and pseudo-second kinetic models were evaluated. We employed Pb-L3 edge X-ray absorption spectroscopy techniques XANES (X-ray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure) for probing the local environments of Pb within the tentative Pb-S complex after adsorptions of Pb2 + by the mercapto groups. The EXAFS/XANES analysis indicated complete Pb2 + complexation with two SH groups of the prepared SiO2@SH samples.

Rare earth elements are widely used in chemical engineering, the nuclear industry, metallurgy, medicine, electronics, and computer technology because of their unique properties. To fulfil ever increasing demands for these elements, recycling of rare-earth-element-containing products as well as their recovery from wastewater is quite important. In order to recover rare earth elements from wastewater, their adsorption from low-concentration aqueous solutions, by using nanomaterials, is investigated due to technological simplicity and high efficiency. This paper is a review of the state-of-the-art adsorption technologies of rare earth elements from diluted aqueous solutions by using various nanomaterials. Furthermore, desorption and reusability of rare earth metals and nanomaterials are discussed. On the basis of this review it can be concluded that laboratory testing indicates promising adsorption capacities, which depend significantly on nanomaterial type and adsorption conditions. The adsorption process, which mostly follows the Langmuir, Freundlich, Sips, and Temkin isotherms, is typically endothermic and spontaneous. Furthermore, pseudo-second order, pseudo-first order, and intra-particle diffusion models are the best models to describe the kinetics of adsorption. The dominant adsorption mechanisms are surface complexation and ion exchange. More investigation, however, will be required in order to synthesize appropriate, environmentally friendly, and efficient nanomaterials for adsorption of rare earth elements from real wastewater.

New magnetic stabilized and functionalized core@shell nanoparticles (NPs) were synthesized in a simple way and characterized in order to adsorb Tb3+ from aqueous solution with a very low Tb3+ concentration. For the fluorescence determination of adsorption efficiency and capacity, tiron monohydrate as a ligand was used. The obtained results confirm the potential of the synthesized magnetic &gamma, Fe2O3-NH4OH@SiO2 NPs, functionalized with (3-Aminopropyl) trimethoxysilane (APTMS), to be used for adsorption of Tb3+ from aqueous solution, with the possibility of its removal from aqueous solution via an external magnet. The endothermic and spontaneous adsorption follows a pseudo-second-order kinetic model, and the adsorption equilibrium data fit the Temkin isotherm well. The maximum adsorption efficiency from aqueous solution with a 2 &times, 10&minus, 6 M concentration of Tb3+ is over 90% at pH 7.

This paper deals with synthesis and characterization of novel γ-Fe

The decolorization and mineralization of two reactive dyes C.I. Reactive Blue 4 (RB 4) and C.I. Reactive Blue 268 (RB 268) were studied using various advanced oxidation processes (AOPs) such as H2O2/UV, H2O2/UV/Fe2+, and the H2O2/UV/Fe°. All processes were performed within a laboratory-scale photo-reactor setup. The experimental results were assessed in terms of absorbance (A) and total organic carbon (TOC) reduction. The main degradation products were identified by high resolution gas chromatography/high resolution mass spectrometry analyses. The results of our study demonstrated that the additions of moderate concentrations of H2O2 and Fe catalyst during the AOPs evidently increased the decolorization efficiencies within the first few minutes of the processing time (5–10 min) for both tested dyes, and prolonged irradiation does not necessarily significantly improve decolorization. On contrary, TOC removal rate increased with the processing time and with the addition of the catalyst from 40–50% u...

Hexahistidine-tagged organophosphate hydrolase (His6-OPH), an organophosphate degrading enzyme, immobilised by physical adsorption and covalent binding methods on mesoporous silica (MPS) particles, was examined as a biocatalyst for organophosphate hydrolysis within an aqueous medium and for providing an efficient tool in the detection/detoxification of paraoxon. His6-OPH was immobilised on mesoporous silica particles of different pore size distributions (10–40 and 6 nm) and sizes (5 μm and 500 nm), through covalent attachment and physical adsorption. The biocatalysts showed good activities and enhanced stabilities with respect to the free enzymes, depending on the material and used immobilisation technique. Biomaterial based on hexahistidine-tagged organophosphorus hydrolase (His6-OPH) was developed by enzyme immobilisation into/onto two types of silica particles with different porosity. While adsorbed enzymes showed higher activities, covalent attached enzymes showed minimal or no losses in activity as well as reusability.

In this study, we report on the fluorimetric method for the determination of biogenic amine agmatine based on hybrid SiO2 particles functionalized with thiol groups of 3-mercaptopropyltrimethoxysilane (MPTMS, SiO2–SH) and further conjugated with indicator dye o-phthaldialdehyde (OPA, SiO2–SH–OPA). Under optimal conditions, OPA reacted with agmatine and formed a fluorescent product in the alkaline media (pH 13). The fluorescence excitation and emission wavelengths were located at 340 and 430 nm. The relative fluorescence intensity was linear in the concentration range between 1.0 × 10−7 and 1.0 × 10−2 mol/L. Obtained SiO2–SH particles were characterized using infrared spectroscopy (FTIR), transmission electron microscopy, zeta potential and potentiometric titration.

Investigations were conducted to explore the use of anaerobic treatment options that may allow complete recovery of primary and waste activated sludge streams for incineration from a graphic paper mill with an integrated deinked pulp plant. The effective reduction of waste activated sludge quantity (55%–65%) was obtained by the anaerobic treatment of wastewater from the deinked pulp plant or by the anaerobic stabilization of the mill effluent from primary treatment, where chemical oxygen demand (COD) removal efficiency of 67.6% and 64.8%, and biogas potential of 440 and 496 m3/t CODremoved were achieved, respectively. The anaerobic treatment of wastewater and alkali hydrolysis of waste activated sludge decreased the dewatering properties of solids residue in treated effluent resulting in a negative impact on the sludge recovery energy balance. The addition of municipal wastewater to anaerobic treatment in the amount of 18 vol%, representing 10% of the total COD, increased the reduction of waste activated sludge to 78%, with a positive impact on the treatment costs and efficiency. Anaerobic treatment of the studied effluents may enable incineration of all mill sludge with a positive energy balance, a reduction of biological wastewater treatment operational cost by up to 83%, and mill conventional energy demands by up to 2.7%, resulting in total cost savings of up to EUR 5.2 (USD 5.60) per ton of paper.

The presented work describes the optimising of sol–gel process parameters including the aging time of the sol, the water/silane ratios, type of precursor [tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS)], and the precursor ratios using organically modified silanes [methyltrimethoxysilane (MTMOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS)], for the successful entrapment of hexahistidine-tagged organophosphorus hydrolase (His6-OPH) and its applicability during organophosphate detoxification processes. The prepared bio-composite films retained enzyme activity by up to 90 % with expected differences between the starting sols’ compositions. The obtained values of KM and Vmax for TMOS/MTMOS and TEOS/GPTMS bio-composites equalled 1.5 ± 0.1, 1.4 ± 0.3 mM, 0.40 ± 0.02 and 1.8 ± 0.2 μM/s for paraoxon, respectively, thus assuming effective application of such biocatalysts during the detoxifications of organophosphorus compounds. Furthermore, the bio-composite films showed enhanced pH and temperature stability with respect to the free enzymes as they can be easily separated from the reactive media, as well as having multiple reusages. Bio-composite materials based on hexahistidine-tagged organophosphorus hydrolase were developed by enzyme encapsulation into silica sol–gel matrixes (tetramethoxysilane/methyltrimethoxysilane, tetraethoxysilane/3-glycidoxypropyltrimethoxysilane). The process of biomaterial production was optimised in several pathways and biomaterials were characterised via IR-spectroscopy, SEM-imaging, so as their catalytic efficiency in organophosphate hydrolysis.

This study presents an optical determination of agmatine at pH 13. The fluorescent product formed between the indicator reagent o-phthaldialdehyde and agmatine sulfate reached its maximum intensity within twenty minutes of incubation time when excited at 340 nanometers. The determination of agmatine sulfate was linear within a concentration range between 6.0 × 10−7 and 8.0 × 10−6 moles per liter and the limit of detection was 1.5 × 10−8 molar. Under the optimized conditions, the fluorescent intensity of o-phthaldialdehyde in the presence of other biogenic amines (histamine, tyramine, putrescine, noradrenaline, etc.) was at least fourteen-fold lower than that of the o-phthaldialdehyde–agmatine sulfate product. The method was applied for the determination of agmatine sulfate in dietary supplements.

The need for an improved sensor performance is always encouraging us towards exploring new materials. Following the invention of dendrimers, the possibility was recognised of using them for improving optical sensor performance. Their more important aspects are their two main structural properties: three-dimensional structure and multiple terminal functional groups. In this review, firstly a brief introduction to dendrimers is provided with the focus on PAMAM dendrimers and optical sensors. Recent advances have been reported in those PAMAM dendrimer-based optical sensors, which are used for the detection of pH, cations, and other analyte.

Mercaptopropyl-coated cobalt ferrite (CoFe2O4) magnetic nanoparticles synthesized using the co-precipitation method and surface modified using the Stober method were investigated as a convenient and effective adsorbent for aqueous Hg2+ ions. The surfaces of the colloidal-CoFe2O4 nanoparticles were functionalized with tetraethoxysilane and 3-mercaptopropyltrimethoxysilane via the co-condensation process. The characteristics of these particles were assessed at different stages of the production process using X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and vibrating-sample magnetometry. The adsorption capacity of the mercaptopropyl-coated CoFe2O4 nanoparticles with respect to the aqueous Hg2+ ions was evaluated using atomic absorption spectrometer. It was found that the pH value of the model solution, the mass of the adsorbent, the temperature and the time of the adsorption significantly influence the sorption of Hg2+ ions on the mercaptopropyl-coated cobalt ferrite nanoparticles. The maximum removal efficiency of the aqueous Hg2+ ions was 97 % at room temperature and neutral pH value.

This paper deals with synthesis and characterization of novel γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles formed from magnetic γ-Fe2O3 core, stabilized electrostatically in basic media NH4OH, doped with SiO2 shell and functionalized with 3-aminopropyltrimethoxysilane. The gradually synthesized nanoparticles are characterized in order to analyze their structural, morphology, thermogravimetry, surface area and charge, and magnetic properties. The novel synthesized γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles are suitable to adsorb dysprosium ions (Dy3+), as one of the most critical rare earth elements, from aqueous solution. The Dy3+ adsorption from aqueous solution follows a pseudo-second order kinetic model and the adsorption equilibrium data fits well to the Temkin isotherm. Thermodynamic studies imply that the adsorption process is endothermic and spontaneous in nature. The maximum adsorption efficiency for Dy3+ from aqueous solution with 2·10−6M concentration of Dy3+ is over 90% at pH 7.

The aims of this work were to efficiently immobilize organophosphate degrading enzyme, His6-OPH, on hierarchical mesoporoustitania thin films and further, to use this biocatalyst films as efficient tools in the detection/detoxofication of pesticides, paraoxon in our case. His6-OPH was immobilized on mesoporous thin films with uniform (9nm) and bimodal (13-38nm) pore size distribution, through covalent attachment and physical adsorption. The biocatalyst films show good activity, and enhanced stability with respect to the free enzyme at extreme conditions of pH and temperature, especially around neutral pH and room temperature. In addition, they can be easily separated from the reaction media and reused multiple times without significant loss in activity. Fil: Francica, Cynthia. University of Maribor. Faculty of Mechanical Engineering. Centre of Sensor Technology; Eslovenia Fil: Bellino, Martin Gonzalo. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lobnik, A.. University of Maribor. Faculty of Mechanical Engineering. Centre of Sensor Technology; Eslovenia

This article presents a novel systematic approach to the fabrication of highly functionalized, silica (SiO2) nanoparticles used for the adsorption of heavy-metal ions (Hg2+, Pb2+, Cd2+, Zn2+). Almost monodispersed silica (SiO2) nanoparticles with narrow particle size distributions of around 85 ± 5 nm were formed using the Stober process. The prepared SiO2 nanoparticles were successfully surface-treated during a one-step procedure by the covalent attachment of mercaptopropyl groups onto the surfaces of the SiO2 nanoparticles. A FTIR spectra analysis confirmed that the binding of the mercaptosilane molecules onto the surface of the silica nanoparticles mediated the Si–O–Si and –SH vibrations. TEM/EDXS micrographs indicated the almost monodispersed and spherical morphology of the prepared product with strong signals of Si and S, thus implying that the coating procedure involving the mercapto groups onto the silica surface had been successfully accomplished. The final results for the heavy-metal (Hg2+, Pb2+, Cd2+, Zn2+) adsorption showed the strongest affinity within the following sequence Hg2+ (99.9%) > Pb2+ (55.9%) > Cd2+ (50.2%) > Zn2+ (4%). Adsorption equilibrium was achieved after 1 h for all the analyzed samples.

We have investigated the removal of Pb2+ ions from water using thiol-functionalized, cobalt-ferrite, magnetic nanoparticles. These magnetic nanoparticles were prepared using the co-precipitation method and their surfaces were modified with tetraethoxy silane and 3-mercaptopropyl trimethoxysilane in order to provide a sufficient surface concentration of the thiol (–SH) functional groups. The adsorption of the Pb2+ ions from the aqueous solutions onto the thiol-functionalized, cobalt-ferrite, magnetic nanoparticles was studied. The investigated parameters include the pH value of the model water, the concentration of the adsorbent, the contact time and the temperature of adsorption. The removal of the Pb2+ was found to be greater at the higher pH values and increasing the temperature was also found to increase the removal of Pb2+ ions.

The characterization of nanofiltration (NF) membranes is necessary for predicting their performance under different operating conditions, and for optimizing the membrane-separation process. A thin-film composite (TFC) polymer membrane for nanofiltration, modified with tri- and tetra-alkoxysilanes, was produced using a sol–gel procedure. The surface charges of the modified membranes were determined at different pHs by means of the zeta-potential. The streaming current was measured for a zeta-potential analysis of the flat-sheet membranes. Knowledge of the zeta-potential is essential for designing and operating membrane processes, and its measurement provides the key to understanding the control of charge-related phenomena. The zeta-potential of modified membranes is distinct from that of an untreated membrane. The isoelectric point was found to be at a higher pH after a treatment with any of the alkoxysilanes. The surfaces of the modified membranes showed an amphoteric behaviour. The homogeneity and stability of the treatment were assessed by a repeated zeta-potential analysis of the same and different membrane samples.

This article presents the influence of low frequency, high intensity ultrasonic irradiation on the characteristics (average size, polydispersity index) of ethyl cellulose nanocapsules encapsulating a photochromic dye. Photochromic nanocapsules were prepared by the emulsion-solvent evaporation method. The acoustic densities entering the system were systematically studied with respect to their abilities to modify and reduce the average sizes and polydispersity indexes of the nanocapsules. Scanning electron microscope, confocal laser microscope, and dynamic light scattering were utilised to characterise the structure, shape, size, and polydispersity of ethyl cellulose photochromic nanocapsules. We were able to tailor the size of the photochromic nanocapsules simply by varying the acoustic densities entering the system. At an acoustic density of 1.5 W/mL and 60 s of continuous irradiation, we were able to prepare an almost monodispersed population of the nanocapsules with an average size of 193 nm.

The surface of magnetite nanoparticles was coated with functional polysiloxane layers using reaction of hydrolytic copolycondensation of tetraethoxysilane and 3-aminopropyltriethoxysilane (or N-[3-trimethoxysilylpropyl]ethylendiamine), and also that of tetraethoxysilane, 3-aminopropyltriethoxysilane and methyltriethoxysilane (or n-propyltriethoxysilane). It was shown that these functionalized magnetically controllable particles (about 60–150 nm in size as aggregates), as opposed to magnetite, adsorb urease well from aqueous solutions (up to 1 g/g), and that the level of residual activity of adsorbed layers is up to 84 % in the case of a bifunctional sample. It was established that the activity of immobilized urease is normally gradually reduced during storage of the samples, but in the case of ethylenediamine functional group is not decreased for 45 days. The synthesized samples are promising for use as magnetically directed biocatalysts.

Because of their size and versatile chemistry, nanomaterials represent today powerful tools for (bio) sensing applications. Various types of nanomaterials have proven to be practical, not only for the determination of clinically relevant parameters, but also for diagnostics, drug delivery and treatment of diseases (e.g. cancer). In this short review, types of nanomaterials used in medical applications are briefly described along with some of their applications where the nanomaterials optical properties can be exploited. The question of the toxicity of nanomaterials and the issue of future trends are also raised.

Heavy metal pollution is one of the more serious environmental problems; therefore, there is a constant demand for the development of new analytical tools for its monitoring. An optical chemical sensor represents a good alternative to classical instrumental methods. The mesoporous materials used in optical chemical sensors’ fabrications have properties such as high porosity, exceptional adsorption capacity, tuneable 3D shape, geometry, and morphology, which enable improved limit of detection, response time, and selectivity properties of optical sensors. In this review, we firstly present the properties of mesoporous materials, provide a brief description of sensing mechanisms, and briefly discuss the importance of continuous monitoring. Recent advances in those mesoporous silica-based optical sensors used for heavy metal detection have been reported and their advantages and limitations also discussed. This review covers publications that have appeared since 2008.

Luminescent sensors are chemical systems that can deliver information on the presence of selected analytes through the variations in their luminescence emission. With the advent of luminescent nanoparticles several new applications in the field of chemical sensing were explored. Among them, quantum dots (QD) represent inorganic semiconductor nanocrystals that are advantageous over conventional organic dyes from many different points of view. In this short review, the optical detection of various analytes using QD-based probes/sensors is presented and significant sensors characteristics are discussed. The biosensing approaches are not included in this article.

CO2 gas with a special isotopic signature (δ13C = −35.2‰ vs. VPDB) was used as a marker to evaluate the efficiency of a drinking water treatment method and the effect of an ultrasonic (US) stirrer. This treatment was developed to prevent precipitation and corrosion effects in water–supply systems. The research work was performed using a laboratory-scale pilot plant that was filled with tap water. The stable isotope analyses of δ13C-DIC (Dissolved Inorganic Carbon) in the water samples indicated that the maximum content of added CO2 gas in DIC was in the range of 35 to 45%. The use of the US stirrer during the entire experiment decreased the method's overall efficiency by 10%, due to degassing at a late stage of the experiment but accelerated the dissolution process in the early experimental stage.