Advanced Photodegradation of Azo Dye Methyl Orange Using H2O2-Activated Fe3O4@SiO2@ZnO Composite under UV Treatment.

The Fe3O4@SiO2@ZnO composite was synthesized via the simultaneous deposition of SiO2 and ZnO onto pre-prepared Fe3O4 nanoparticles. Physicochemical methods (TEM, EDXS, XRD, SEM, FTIR, PL, zeta potential measurements, and low-temperature nitrogen adsorption/desorption) revealed that the simultaneous deposition onto magnetite surfaces, up to 18 nm in size, results in the formation of an amorphous shell composed of a mixture of zinc and silicon oxides. This composite underwent modification to form Fe3O4@SiO2@ZnO*, achieved by activation with H2O2. The modified composite retained its structural integrity, but its surface groups underwent significant changes, exhibiting pronounced catalytic activity in the photodegradation of methyl orange under UV irradiation. It was capable of degrading 96% of this azo dye in 240 min, compared to the initial Fe3O4@SiO2@ZnO composite, which could remove only 11% under identical conditions. Fe3O4@SiO2@ZnO* demonstrated robust stability after three cycles of use in dye photodegradation. Furthermore, Fe3O4@SiO2@ZnO* exhibited decreased PL intensity, indicating an enhanced efficiency in electron-hole pair separation and a reduced recombination rate in the modified composite. The activation process diminishes the electron-hole (e-)/(h+) recombination and generates the potent oxidizing species, hydroxyl radicals (OH˙), on the photocatalyst surface, thereby playing a crucial role in the enhanced photodegradation efficiency of methyl orange with Fe3O4@SiO2@ZnO*.

Advanced Removal of Dyes with Tuning Carbon/TiO2 Composite Properties.

This study evaluates the removal of several dyes with different charge properties, i.e., anionic (Acid Red 88), cationic (Basic Red 13), and neutral (Basic Red 5) using transition metal-doped TiO2 supported on a high-surface-area activated carbon. Experimental results confirm the successful deposition of TiO2 and the derivatives (Zr-, Cu-, and Ce-doped samples) on the surface of the activated carbon material and the development of extended heterojunctions with improved electronic properties. Incorporating a small percentage of dopants significantly improves the adsorption properties of the composites towards the three dyes evaluated, preferentially for sample AC/TiO2_Zr. Similarly, the photodegradation efficiency highly depends on the nature of the composite evaluated and the characteristics of the dye. Sample AC/TiO2_Zr demonstrates the best overall removal efficiency for Acid Red 88 and Basic Red 5-83% and 63%, respectively. This promising performance must simultaneously be attributed to a dual mechanism, i.e., adsorption and photodegradation. Notably, the AC/TiO2_Ce outperformed the other catalysts in eliminating Basic Red 13 (74%/6 h). A possible Acid Red 88 degradation mechanism using AC/TiO2_Zr was proposed. This study shows that the removal efficiency of AC/TiO2 composites strongly depends on both the material and pollutant.

In situ synthesis of AgI on the nanosilica surface for potential application as a cloud seeding material.

A series of nanosilica/AgI composites was synthesized by in situ reactions between silver nitrate and ammonium iodide deposited on the nanosilica surface using the gas-phase solvate-stimulated mechanosorption modification (GSSMSM) under both dry and wet conditions. The characterization of the synthesized materials was performed by X-ray diffraction (XRD), SEM/EDX (Scanning Electron Microscopy-Energy Dispersive X-ray), thermogravimetric (TGA) and gas sorption methods. As a result of the mechanosorption modification of nanosilica, the bulk density of the samples synthesized in the dry and wet medium increases from 45 g/l for initial nanosilica to 249 g/l and 296 g/l for the modified samples, respectively. The specific surface area of the composites decreased in compared to the nanosilica precursor. The SEM data showed a denser aggregate structure of the nanocomposites compared to the initial nanosilica. The XRD, SEM/EDX and TEM/EDX data indicated the formation of AgI clusters. The AgI particle size was in the range of 6-45 nm. The ice-forming activity of the AgI-containing samples was examined as well. The sample with a smaller size of silver iodide on the surface exhibited superior ice-forming properties, and considering the quantity of utilized AgI, the prepared samples hold promise for application in this field.

Investigation of the Interaction between Mechanosynthesized ZnS Nanoparticles and Albumin Using Fluorescence Spectroscopy.

In this paper, ZnS nanoparticles were bioconjugated with bovine serum albumin and prepared in a form of nanosuspension using a wet circulation grinding. The stable nanosuspension with monomodal particle size distribution (d50 = 137 nm) and negative zeta potential (-18.3 mV) was obtained. The sorption kinetics and isotherm were determined. Interactions between ZnS and albumin were studied using the fluorescence techniques. The quenching mechanism, describing both static and dynamic interactions, was investigated. Various parameters were calculated, including the quenching rate constant, binding constant, stoichiometry of the binding process, and accessibility of fluorophore to the quencher. It has been found that tryptophan, in comparison to tyrosine, can be closer to the binding site established by analyzing the synchronous fluorescence spectra. The cellular mechanism in multiple myeloma cells treated with nanosuspension was evaluated by fluorescence assays for quantification of apoptosis, assessment of mitochondrial membrane potential and evaluation of cell cycle changes. The preliminary results confirm that the nontoxic nature of ZnS nanoparticles is potentially applicable in drug delivery systems. Additionally, slight changes in the secondary structure of albumin, accompanied by a decrease in α-helix content, were investigated using the FTIR method after analyzing the deconvoluted Amide I band spectra of ZnS nanoparticles conjugated with albumin. Thermogravimetric analysis and long-term stability studies were also performed to obtain a complete picture about the studied system.

Nano-bio interface between As4S4 nanoparticles and albumin influenced by wet stirred media milling.

Arsenic sulfide (As4S4) nanoparticles have been intensively researched as a promising drug in a cancer treatment. For the first time, the interaction between As4S4 and bovine serum albumin has been studied in this paper. Initially, the sorption kinetics of albumin on the surface of nanoparticles was investigated. Subsequently, its structural changes influenced by interaction with the As4S4 nanoparticles during wet stirred media milling were studied in deep. Both the dynamic and static quenching were detected after analyzing the fluorescence quenching spectra. From the synchronous fluorescence spectra it was investigated, that the fluorescence intensity for tyrosine residues decreased by about 55%, and for tryptophan it was about 80%. It indicates the fluorescence from tryptophan is more intense and gets more efficiently quenched than those from tyrosine residues in presence of As4S4, implying that the tryptophan can be closer to the binding site. From the circular dichroisms and FTIR spectra it was observed that conformation of the protein remains almost unchanged. The content of appropriate secondary structures was determined by deconvolution of the absorption peak attributed to the amide I band in FTIR spectra. The preliminary anti-tumor cytotoxic effect of prepared albumin-As4S4 system was also tested on multiple myeloma cell lines.

Diamine Groups on the Surface of Silica Particles as Complex-Forming Linkers for Metal Cations.

Novel spherically shaped organosilica materials with (propyl)ethylenediamine groups were obtained via a modified one-pot Stöber co-condensation method. The porosity of these materials was tuned with the controlled addition of three silica monomers acting as structuring agents (tetraethoxysilane and bridged silanes with ethylene and phenylene bridges). The morphologies and structures of the synthesized materials were studied by SEM, DRIFT spectroscopy, CHNS elemental analysis, low-temperature nitrogen adsorption-desorption, and electrokinetic potential measurements. Their sizes were in the range of 50 to 100 nm, depending on the amount of structuring silane used in the reaction. The degree of the particles' agglomeration determined the mesoporosity of the samples. The content of the (propyl)ethylenediamine groups was directly related with the amount of functional silane used in the reaction. The zeta potential measurements indicated the presence of silanol groups in bissilane-based samples, which added new active centers on the surface and reduced the activity of the amino groups. The static sorption capacities (SSCs) of the obtained samples towards Cu(II), Ni(II), and Eu(III) ions depended on the porosity of the samples and the spatial arrangement of the ethylenediamine groups; therefore, the SSC values were not always higher for the samples with the largest number of groups. The highest SSC values achieved were 1.8 mmolCu(II)/g (for ethylene-bridged samples), 0.83 mmolNi(II)/g (for phenylene-bridged samples), and 0.55 mmolEu(III)/g (for tetraethoxysilane-based samples).

Development of polyester filters with polymer nanocomposite active layer for effective dye filtration.

Organic dyes such as methyl orange (MO) and methylene blue (MB) are widely used in different industries and have become one of the leading emerging water contaminants. The purpose of the current research is to develop new polymer nanocomposite filters for the effective elimination of the dyes, which are non-biodegradable and not efficiently removed by traditional treatment methods. New padded and covered filters were produced applying polystyrene-acrylic/ZnO nanocomposite on the polyester surface by blade coating and one-bath pad methods. Principal results determined by SEM analysis confirm that functionalised layer can create unprecedented function of filter textile material depending on the way of treatment. Due to the modification, the surface area increased from 5.9 for untreated polyester to 85.2 (padded), 44.6 (covered) m2/g. The measured pore size of produced filters is around 3.4 nm, which corresponds to the mesoporous structure. Our study reported effective filters with the rate of MB and MO removal efficiencies up to 60%. Moreover, a colourless reduced form of MB-leuco-methylene blue (LMB) could be created. The functionalised layer of the developed filters through hydrogen bonding between the -OH groups of styrene-acrylic molecules and the -N(CH3)2 groups on LMB can stabilise LMB.

New perception of Zn(II) and Mn(II) removal mechanism on sustainable sunflower biochar from alkaline batteries contaminated water.

The combination of several methods (X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis, infrared spectroscopy) was applied to study the changes that have occurred during the adsorption of Zn(II) and Mn(II) ions on a carbonized sunflower sample for understanding a mechanism of heavy metals adsorption. Sunflower biochar was obtained from the stem and inflorescences sunflower wastes through pyrolysis at 600 °C for 30 min. According to the infrared spectroscopy and Boehm titration data, this carbonized material has acidic and basic functional groups on its surface, but they do not participate in the metal ions adsorption. However, the synthesized carbon proved to be a sustainable high-effective adsorbent for zinc(II) and manganese(II) ions removal with adsorption capacity 138.3 mg g-1 of Zn2+ and 45.4 mg g-1 for Mn2+. Surface analysis of the carbonized material by energy dispersive X-ray analysis, X-ray diffraction, and X-ray photoelectron spectroscopy indicated the presence of soluble and insoluble inorganic salts, such as KCl, NaCl, NaHCO3, KHCO3, CaCO3, MgCO3. It was established, that during the adsorption process, soluble salts are washed away, and new insoluble ones are formed assisting by Zn(II) and Mn(II) ions. It has been revealed that the adsorptive removal of Zn2+ and Mn2+ is caused by the precipitation mechanism. The efficiency of removing Zn(II) and Mn(II) ions from water contaminated with battery waste by the same mechanism is shown.

Production of high-performance lead(II) ions adsorbents from pea peels waste as a sustainable resource.

This research deals with a highly efficient, selective, low-cost, and recyclable adsorbent for the fast removal of lead (Pb)(II) ions from aqueous solutions, and an investigation of the related adsorption mechanisms. Three types of materials were prepared from pea peels waste using simple, energy-efficient and environmentally friendly treatment. Obtained adsorbents were characterized by elemental analysis, infrared spectroscopy, scanning electron microscopy, Boehm titration, and the main parameters were determined. The highest adsorption capacity was observed for the biochar prepared by heating of pea peels at 600°C for 30 minutes. The uptake of Pb(II) ions on pea peels-derived samples was examined as a function of pH, contact time, and initial Pb2+ concentration. Obtained results from adsorption experiments of Pb(II) ions on the biochar surface indicate high adsorption capacity, and the possibility of its preconcentration and selective removal in the presence of zinc(II) and cadmium(II) ions. This confirms a potential application of such materials in water remediation.

Diverse Pathway to Obtain Antibacterial and Antifungal Agents Based on Silica Particles Functionalized by Amino and Phenyl Groups with Cu(II) Ion Complexes.

Production of environmentally friendly multitasking materials is among the urgent challenges of chemistry and ecotechnology. The current research paper describes the synthesis of amino-/silica and amino-/phenyl-/silica particles using a one-pot sol-gel technique. CHNS analysis and titration demonstrated a high content of functional groups, while scanning electron microscopy revealed their spherical form and ∼200 nm in size. X-ray photoelectron spectroscopy data testified that hydrophobic groups reduced the number of water molecules and protonated amino groups on the surface, increasing the portion of free amino groups. The complexation with Cu(II) cations was used to analyze the sorption capacity and reactivity of the aminopropyl groups and to enhance the antimicrobial action of the samples. Antibacterial activities of suspensions of aminosilica particles and their derivative forms containing adsorbed copper(II) ions were assayed against Gram-positive (Staphylococcus aureus ATCC 25923) and Gram-negative bacteria (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853). Meanwhile, antifungal activity was tested against fungi (Candida albicans UCM Y-690). According to zeta potential measurements, its value could be depended on the suspension concentration, and it was demonstrated that the positively charged suspension had higher antibacterial efficiency. SiO2/-C6H5/-NH2 + Cu(II) sample's water suspension (1%) showed complete growth inhibition of the bacterial culture on the solid medium. The antimicrobial activity could be due to occurrence of multiple and nonspecific interactions between the particle surfaces and the surface layers of bacteria or fungi.

Protection of Thiol Groups on the Surface of Magnetic Adsorbents and Their Application for Wastewater Treatment.

The magnetite nanoparticles were functionalized with silica shells bearing mercaptopropyl (monofunctional) and mercaptopropyl-and-alkyl groups (bifunctional) by single-step sol-gel technique. The influence of synthetic conditions leading to increased amounts of active functional groups on the surface and improved capacity in the uptake of Ag(I), Cd(II), Hg(II), and Pb(II) cations was revealed. The physicochemical properties of obtained magnetic nanocomposites were investigated by FTIR, Raman, XRD, TEM, SEM, low-temperature nitrogen ad-/desorption measurements, TGA, and chemical microanalysis highlighting the efficiency of functionalization and mechanisms of the preparation procedures. The removal of the main group of heavy metal cations was studied in dependence from the pH, contact time and equilibrium concentration to analyze the complexes composition for the large scale production of improved adsorbents. It was demonstrated that introduction of the alkyl groups into the surface layer prevents the formation of the disulfide bonds between adjacent thiol groups. The obtained adsorbents were employed to treat real wastewater from Ruskov, Slovakia with concentration of Fe 319 ng/cm3, Cu 23.7 ng/cm3, Zn 36 ng/cm3, Mn 503 ng/cm3, Al 21 ng/cm3, As 34 ng/cm3, Pb 5.8 ng/cm3, Ni 35 ng/cm3, Co 4.2 ng/cm3, Cr 9.4 ng/cm3, Sb 6 ng/cm3, Cd 5 ng/cm3. These materials proved to be highly effective in the removal of 50% of all metal ions, espeсially Zn, Cd, and Pb ions from it and turned recyclable, opening for their sustainable use in water purification.

Sol-Gel Derived Adsorbents with Enzymatic and Complexonate Functions for Complex Water Remediation.

Sol-gel technology is a versatile tool for preparation of complex silica-based materials with targeting functions for use as adsorbents in water purification. Most efficient removal of organic pollutants is achieved by using enzymatic reagents grafted on nano-carriers. However, enzymes are easily deactivated in the presence of heavy metal cations. In this work, we avoided inactivation of immobilized urease by Cu (II) and Cd (II) ions using magnetic nanoparticles provided with additional complexonate (diethylene triamine pentaacetic acid or DTPA) functions. Obtained nanomaterials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). According to TGA, the obtained Fe3O4/SiO2-NH2-DTPA nanoadsorbents contained up to 0.401 mmol/g of DTPA groups. In the concentration range Ceq = 0-50 mmol/L, maximum adsorption capacities towards Cu (II) and Cd (II) ions were 1.1 mmol/g and 1.7 mmol/g, respectively. Langmuir adsorption model fits experimental data in concentration range Ceq = 0-10 mmol/L. The adsorption mechanisms have been evaluated for both of cations. Crosslinking of 5 wt % of immobilized urease with glutaraldehyde prevented the loss of the enzyme in repeated use of the adsorbent and improved the stability of the enzymatic function leading to unchanged activity in at least 18 cycles. Crosslinking of 10 wt % urease on the surface of the particles allowed a decrease in urea concentration in 20 mmol/L model solutions to 2 mmol/L in up to 10 consequent decomposition cycles. Due to the presence of DTPA groups, Cu2+ ions in concentration 1 µmol/L did not significantly affect the urease activity. Obtained magnetic Fe3O4/SiO2-NH2-DTPA-Urease nanocomposite sorbents revealed a high potential for urease decomposition, even in presence of heavy metal ions.

Tailoring bifunctional hybrid organic-inorganic nanoadsorbents by the choice of functional layer composition probed by adsorption of Cu2+ ions.

Spherical silica particles with bifunctional (≡Si(CH2)3NH2/≡SiCH3, ≡Si(CH2)3NH2/≡Si(CH2)2(CF2)5CF3) surface layers were produced by a one-step approach using a modified Stöber method in three-component alkoxysilane systems, resulting in greatly increased contents of functional components. The content of functional groups and thermal stability of the surface layers were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and 13C and 29Si solid-state NMR spectroscopy revealing their composition and organization. The fine chemical structure of the surface in the produced hybrid adsorbent particles and the ligand distribution were further investigated by electron paramagnetic resonance (EPR) and electron spectroscopy of diffuse reflectance (ESDR) spectroscopy using Cu2+ ion coordination as a probe. The composition and structure of the emerging surface complexes were determined and used to provide an insight into the molecular structure of the surfaces. It was demonstrated that the introduction of short hydrophobic (methyl) groups improves the kinetic characteristics of the samples during the sorption of copper(II) ions and promotes fixation of aminopropyl groups on the surface of silica microspheres. The introduction of long hydrophobic (perfluoroctyl) groups changes the nature of the surface, where they are arranged in alternately hydrophobic/hydrophilic patches. This makes the aminopropyl groups huddled and less active in the sorption of metal cations. The size and aggregation/morphology of obtained particles was optimized controlling the synthesis conditions, such as concentrations of reactants, basicity of the medium, and the process temperature.

Magneto-Sensitive Adsorbents Modified by Functional Nitrogen-Containing Groups.

In order to obtain amino-functionalized silica materials with magnetic core, one-step synthesis was carried out. Several materials, differ in number and structure of amino groups, were synthesized on the basis of sol-gel method. The synthesized materials were examined by several analytical techniques. The presence and content of amino groups were measured by using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and acid-base titration, respectively. Specific surface areas were measured by nitrogen/adsorption desorption isotherms. It was proved that sol-gel approach leads to obtain materials with high content of amino groups built into their surfaces (in the range 1.6-2.7 mmol/g). As-obtained materials were tested as potential adsorbents for copper(II) ions. The received maximum adsorption capacities were in the range 0.4-0.7 mmol/g.

Mesoporous silica containing ≡Si(CH2)3NHC(S)NHC2H5 functional groups in the surface layer.

One-step synthesis technique of mesoporous SBA-15 type silica with thiourea ≡Si(CH(2))(3)NHC(S)NHC(2)H(5) groups in the surface layer was developed. According to elemental analysis, the content of surface groups is 1.25 mmol/g, which is consistent with TGA data. FT-IR spectra of the obtained sample contain characteristic absorption bands of thiourea groups (-NH-C(S)-NH-), as well as polysiloxane network (SiOSi). The synthesized sample was studied by XRD, TEM, SEM, and adsorption method. It was demonstrated that the sample features porous microspheres ~0.5 µm with well-ordered internal spatial structure of the hexagonal lattice type due to the usage of template P123 during synthesis. According to XRD and TEM, the diameter of pores is 4.2-5 nm and the wall thickness between them is 2.6 nm. These data are consistent with the structural-adsorption characteristics calculated from nitrogen adsorption-desorption isotherms: S(sp.)=510 m(2)/g, V(s)=0.47 cm(3)/g, and d=4.3 nm. Equilibrium is established within 60 min during sorption of silver(І) and mercury(ІІ) ions from acidified aqueous solutions for this sample, and with the complexes are formed 1.1/1 for Ag(+) and 0.8/1 for Hg(2+) at metal/ligand ratio.