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In this work, a synthesis and activation path, which enabled the preparation of spherical activated carbon from a lignin precursor, characterized by high adsorption capacity in the removal of phenolic compounds from water, was successfully developed. Two industrial by-products, i.e., Kraft lignin and sodium lignosulfonate, were used to form spherical nanometric lignin grains using pH and solvent shift methods. The obtained materials became precursors to form porous activated carbons via chemical activation (using K2CO3 or ZnCl2 as activating agents) and carbonization (in the temperature range of 600–900 °C). The thermal stabilization step at 250 °C was necessary to ensure the sphericity of the grains during high-temperature heat treatment. The study investigated the influence of the type of chemical activator used, its quantity, and the method of introduction into the lignin precursor, along with the carbonization temperature, on various characteristics including morphology (examined by scanning electron microscopy), the degree of graphitization (evaluated by powder X-ray diffraction), the porosity (assessed using low-temperature N2 adsorption), and the surface composition (analyzed with X-ray photoelectron spectroscopy) of the produced carbons. Finally, the carbon materials were tested as adsorbents for removing phenol from an aqueous solution. A conspicuous impact of microporosity and a degree of graphitization on the performance of the investigated adsorbents was found.

Photoactive TiO2 materials based on a C@TiO2 core-shell structure synthesized according to the bottom-up strategy using a spherical resin core were presented in relation to commercial TiO2 (P25) used as a reference material. The studied TiO2 materials were modified with Ag nanoparticles using two alternative methods: impregnation and precipitation. Depending on the deposition technique used, different distributions of the Ag modifier were achieved within the TiO2 structure. As confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements, the precipitation technique resulted in the formation of almost twice smaller, highly dispersed Ag nanoparticles compared to impregnation. Furthermore, the effect of the performed modification on the textural properties (low-temperature N2 adsorption) and surface composition (X-ray photoelectron spectroscopy) was determined. The phase composition of the TiO2 support as well as the dispersion of the Ag modifier significantly affected the energy gap determined from UV–Vis spectra and, consequently, their performance in the process photodegradation of 4-nitrophenol tested as a model molecule. In the case of the @TiO2 material modified with highly dispersed Ag, significantly higher photoactivity in the visible light range was observed than in the presence of analogous P25-based materials.

A novel voltammetric method for the sensitive and selective determination of cadmium and lead ions using screen-printed carbon electrodes (SPCEs) modified with carbon-deposited natural halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) was developed. The electrochemical properties of the proposed sensor were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the morphology and structure were established by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). A two-factorial central composite design (CCD) was employed to select the composition of the nanocomposite modifying the electrode surface. The optimal measuring parameters of differential pulse anodic stripping voltammetry (DPASV) used for quantitative analysis were established with the Nelder–Mead simplex method. In the analytical investigation of Cd(II) and Pb(II) ions by DPASV, the MWCNTs/C_Hal/Nafion/SPCE exhibited a linear response in the concentration range of 0.1–10.0 µmol L−1 (for both ions) with a detection limit of 0.0051 and 0.0106 µmol L−1 for Pb(II) and Cd(II), respectively. The proposed sensor was successfully applied for the determination of metal ions in different natural water and honey samples with recovery values of 96.4–101.6%.

A wide series of copolymer materials with various contents of 4-vinyl-diisopropyl-phtalate ester (10–90 mol%), divinylbenzene (1–11 mol%) and styrene, as monomers, were obtained by radical copolymerization. In the last steps of the synthesis, diisopropyl ester functionalities were converted into the form of N-hydroxyphthalimide (NHPI) rings. The obtained materials with the NHPI groups immobilized in the copolymer structure were studied by various physicochemical techniques, including FT-IR, UV-Vis-DR, XPS, elemental analysis, and tested as catalysts in aerobic oxidation of p-methoxytoluene in the presence of Co(II) acetate co-catalyst. Conversion of the aromatic substrate was correlated with the NHPI content and cross-linking degree. The best catalytic performance (conversions higher than 23%) was achieved for the copolymer catalysts containing 60% and 30% of 4-vinyl-diisopropyl-phtalate ester. At too high concentrations of NHPI and DVB, some of the NHPI groups were transformed into inactive (C=O)-N=O species or not available due to embedding inside the copolymer structure. The mechanism of the process involving both NHPI centers, forming phthalimide N-oxyl (PINO) radicals, and Co(II) cations was discussed. Stability of the developed catalysts was also tested. The opening of imide rings took place during the catalytic process, resulting in the formation of carboxyl groups and the release of hydroxylamine molecules. The deactivated catalyst could be easily regenerated by repeating two last steps of closing imide ring.

Bearing in mind the need to develop optimal transition metal oxide-based catalysts for the combustion of volatile organic compounds (VOCs), yolk-shell materials were proposed. The constructed composites contained catalytically active Co3O4 nanoparticles, protected against aggregation and highly dispersed in a shell made of porous SiO2, forming a specific type of nanoreactor. The bottom-up synthesis started with obtaining spherical poly(styrene-co-acrylic acid) copolymer (PS30) cores, which were then covered with the SiO2 layer. The Co3O4 active phase was deposited by impregnation using the PS30@SiO2 composite as well as hollow SiO2 spheres with the removed copolymer core. Structure (XRD), morphology (SEM), chemical composition (XRF), state of the active phase (UV-Vis-DR and XPS) and reducibility (H2-TPR) of the obtained catalysts were studied. It was proven that the introduction of Co3O4 nanoparticles into the empty SiO2 spheres resulted in their loose distribution, which facilitated the access of reagents to active sites and, on the other hand, promoted the involvement of lattice oxygen in the catalytic process. As a result, the catalysts obtained in this way showed a very high activity in the combustion of toluene, which significantly exceeded that achieved over a standard silica gel supported Co3O4 catalyst.

The paper discusses a formation of Mt–PAA composite containing a natural montmorillonite structure partially exfoliated by poly(acrylic acid) introduced through intercalation polymerization of acrylic acid. Mt–PAA was subsequently modified by controlled adsorption of Co2+ ions. The presence of aluminosilicate packets (clay) and carboxyl groups (hydrogel) led to the deposition of significant amounts of Co2+ ions, which after calcination formed the Co3O4 spinel particles. The conditions of the Co2+ ions’ deposition (pH, volume and concentration of Co(NO3)2 solution, as well as a type of pH-controlling agent) were widely varied. Physicochemical characterization of the prepared materials (including X-ray fluorescence (XRF), X-ray powder diffraction (XRD), low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (H2-TPR)) revealed that the modification conditions strongly influenced the content as well as the distribution of the Co3O4 active phase, tuning its reducibility. The latter parameter was, in turn, very important from the point of view of catalytic activity in the combustion of aromatic volatile organic compounds (VOCs) following the Mars–van Krevelen mechanism.

The polycondensation of resorcinol and formaldehyde in a water–ethanol mixture using the adapted Stöber method was used to obtain resol resins. An optimization of synthesis conditions and the use of an appropriate stabilizer (e.g., poly(vinyl alcohol)) resulted in spherical grains. The resins were carbonized in the temperature range of 600–1050 °C and then chemically activated in an aqueous HNO3 solution, gaseous ammonia, or by an oxidation–reduction cycle (soaking in a HNO3 solution followed by treatment with NH3). The obtained carbons were characterized by XRD, the low-temperature adsorption of nitrogen, SEM, TGA, and XPS in order to determine degree of graphitization, porosity, shape and size of particles, and surface composition, respectively. Finally, the materials were tested in phenol adsorption. The pseudo-second order model perfectly described the adsorption kinetics. A clear correlation between the micropore volume and the adsorption capacity was found. The content of graphite domains also had a positive effect on the adsorption properties. On the other hand, the presence of heteroatoms, especially oxygen groups, resulted in the clogging of the pores and a decrease in the amount of adsorbed phenol.

Neodymium enriched TiO2 anatase-brookite powders were prepared by unconventional method via using pressurized hot fluids for TiO2 crystallization and purification. The photocatalysts were tested in the CH3OH photocatalytic decomposition and they were characterized with respect to the textural (nitrogen adsorption), structural (XRD, XPS, and Raman spectroscopies), chemical (XRF), and optical (DR UV-Vis spectroscopy) and photoelectrochemical measurement. All prepared materials were nanocrystalline, had biphasic (anatase- brookite) structure and relatively large specific surface area (125 m2.g−1). The research work indicates that the doping of neodymium on TiO2 photocatalysts significantly enhances the efficiency of photocatalytic reaction. The photocatalytic activity increased with increasing portion of hydroxyl oxygen to the total amount of oxygen species. It was ascertained that the optimal amount of 1 wt% Nd in TiO2 accomplished the increasing of hydrogen production by 70% in comparison with pure TiO2. The neodymium doped on the titanium dioxide act as sites with accumulation of electrons. The higher efficiency of photocatalytic process was achieved due to improved electron-hole separation on the modified TiO2 photocatalysts. This result was confirmed by electrochemical measurements, the most active photocatalysts proved the highest photocurrent responses.

Photoactive TiO2 materials based on a C@TiO2 core-shell structure synthesized according to the bottom-up strategy using a spherical resin core were presented in relation to commercial TiO2 (P25) used as a reference material. The studied TiO2 materials were modified with Ag nanoparticles using two alternative methods: impregnation and precipitation. Depending on the deposition technique used, different distributions of the Ag modifier were achieved within the TiO2 structure. As confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements, the precipitation technique resulted in the formation of almost twice smaller, highly dispersed Ag nanoparticles compared to impregnation. Furthermore, the effect of the performed modification on the textural properties (low-temperature N2 adsorption) and surface composition (X-ray photoelectron spectroscopy) was determined. The phase composition of the TiO2 support as well as the dispersion of the Ag modifier significantly affected the energy gap determined from UV–Vis spectra and, consequently, their performance in the process photodegradation of 4-nitrophenol tested as a model molecule. In the case of the @TiO2 material modified with highly dispersed Ag, significantly higher photoactivity in the visible light range was observed than in the presence of analogous P25-based materials. [ABSTRACT FROM AUTHOR]