A novel functional silica/lignin hybrid material as a potential bio‐based polypropylene filler

A functional silica/lignin hybrid filler was obtained using a process of mechanical grinding of precursors (Syloid^®244 silica and kraft lignin). The product underwent comprehensive physicochemical and dispersive–morphological analysis. The silica/lignin hybrid has good homogeneity and a surface area of 164 m²/g. The effectiveness of combination was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The high electrokinetic stability (over almost the whole of the analyzed pH range) and above all the thermal stability of the resulting material (mass loss equal to 12%) indicate its potential use as a polypropylene (PP) filler. Experiments showed that the incorporation of a small amount of silica/lignin hybrid filler into PP may substantially influence its elongation at break and notched impact strength. Especially at low concentrations of silica/lignin filler (below 5 wt%) an exceptional set of mechanical properties was obtained. The addition of larger amounts of the filler was found not to bring any further improvement. POLYM. COMPOS., 36:913–922, 2015. © 2014 Society of Plastics Engineers     

Novel precipitated silicas: an active filler of synthetic rubber

Highly dispersed silicas have been obtained at a semi-technical scale by precipitation from sodium metasilicate solutions using appropriately diluted solutions of ammonium hydrogencarbonate or ammonium chloride. The difference, as compared to the generally applied technology of silica precipitation using acids or their anhydrides, has been the involvement of the precipitation reaction in alkaline media. Attempts have been made at changing the silica surface character from hydrophilic to more hydrophobic, using a modifier from the group of silane coupling agents. The alkoxysilanes modifiers contained groups with chemical affinity towards functional groups of butadiene–styrene rubber. Modification of silica surface using silane coupling agents has been found to improve the reinforcement of vulcanizates, by increasing the tensile and tear strength in particular.     

Influence of selected alkoxysilanes on dispersive properties and surface chemistry of spherical silica precipitated in emulsion media

The process of silicas formation in emulsion system in the reaction of precipitation from water solutions of sodium silicate and hydrochloric acid has been studied. The effects of silica surface modifications with silane coupling agents from the group of alkoxysilanes with different functional groups have been determined. Both unmodified and modified silicas have been thoroughly characterised by scanning electron microscopy (SEM) and dynamic light scattering (DLS) and other methods.The effect of alkoxysilanes on the diameter distribution of the modified silica is insignificant; the presence of silane coupling agents causes a small increase in the particle diameter and a small increase in the tendency towards agglomeration, moreover the particles of silicon dioxide precipitated are characterised by spherical shape. The course of the electrokinetic curves depends mainly on the proton affinity of the modifiers. Significant changes in the stability of silica dispersions have been found as a result of modification with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. This compound causes the greatest increase in the tendency towards agglomeration of the primary particles. The modification mechanism has been established to be chemisorption, as indicated by the ¹³C and ²⁹Si CP MAS NMR spectra. The products have been shown to have typical mesoporous structure. The surface area of the unmodified silica is 133 m²/g, while those for the modified silicas vary from 115 to 182 m²/g.     

Removal of Persistent Sulfamethoxazole and Carbamazepine from Water by Horseradish Peroxidase Encapsulated into Poly(Vinyl Chloride) Electrospun Fibers

Enzymatic conversion of pharmaceutically active ingredients (API), using immobilized enzymes should be considered as a promising industrial tool due to improved reusability and stability of the biocatalysts at harsh process conditions. Therefore, in this study horseradish peroxidase was immobilized into sodium alginate capsules and then trapped into poly(vinyl chloride) electrospun fibers to provide additional enzyme stabilization and protection against the negative effect of harsh process conditions. Due to encapsulation immobilization, 100% of immobilization yield was achieved leading to loading of 25 μg of enzyme in 1 mg of the support. Immobilized in such a way, enzyme showed over 80% activity retention. Further, only slight changes in kinetic parameters of free (K_m = 1.54 mM) and immobilized horseradish peroxidase (K_m = 1.83 mM) were noticed, indicating retention of high catalytic properties and high substrate affinity by encapsulated biocatalyst. Encapsulated horseradish peroxidase was tested in biodegradation of two frequently occurring in wastewater API, sulfamethoxazole (antibiotic) and carbamazepine (anticonvulsant). Over 80% of both pharmaceutics was removed by immobilized enzyme after 24 h of the process from the solution at a concentration of 1 mg/L, under optimal conditions, which were found to be pH 7, temperature 25 °C and 2 mM of H₂O₂. However, even from 10 mg/L solutions, it was possible to remove over 40% of both pharmaceuticals. Finally, the reusability and storage stability study of immobilized horseradish peroxidase showed retention of over 60% of initial activity after 20 days of storage at 4 °C and after 10 repeated catalytic cycles, indicating great practical application potential. By contrast, the free enzyme showed less than 20% of its initial activity after 20 days of storage and exhibited no recycling potential.     

Active silicas obtained by precipitation from mixtures of sodium metasilicate and ammonium chloride solutions

Studies were conducted on the production of highly dispersed silicas using the technique of precipitation from solutions of sodium metasilicate and ammonium chloride. Parameters of the precipitation process were optimised in order to obtain highly dispersed as well as uniform and stable silicas. The silicas obtained were subjected to elementary physicochemical analysis, the tendency of the silica particles to form aggregates and agglomerates was examined using scanning electron microscopy (SEM) and dynamic light scattering (DLS), and surface analysis was performed using the BET technique. The silicas obtained manifested exceptionally low bulk density and a high capacity to absorb paraffin oil. Copyright © 2003 Society of Chemical Industry     

Structural and electrochemical properties of multifunctional silica/lignin materials

Synthesis and characterisation of silica/lignin materials is described. Silica was synthesised by the modified Stöber method and its surface was functionalised with aminosilane. The organic matrix was the activated Kraft lignin (KL). The materials obtained were subjected to thorough characterisation (physicochemical, dispersive, morphological and electrochemical) by the NIBS, SEM, FT–IR, and XPS methods. Results of the characterisation permitted evaluation of the application possibilities of the products and the choice of the best ones for specific applications. Because of high negative ionic charge the material particles could be effectively deposited on positively polarised glassy carbon electrode by electrophoretic deposition. The silica/lignin modified electrode showed enhanced charge transfer resistance for anionic redox probe (ferrocyanide/ferricyanide couple) and an enhanced capability to the adsorption of silver cations. The latter property could be exploited in anodic striping voltammetry of silver.     

Ethylene polymerization using vanadium catalyst supported on silica modified by pyridinium ionic liquid

Vanadium catalyst systems (SIL_1–3A(B)/V) for ethylene polymerization were obtained by immobilization of the Cp₂VCl₂ precursor (V) in the ionic liquid 1‐[3‐(triethoxysilyl)propyl]pyridinium chloride (IL), modified by AlCl₃ and AlEtCl₂ (A) or AlEt₂Cl (B), and supported on three types of silica carrier S_1–3. The properties of the ionic liquid supports were determined using Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller measurements, scanning electron microscopy and elemental analysis. The best results (above 2 tons PE (mol V)^?1 (0.5 h)^?1) were obtained using the catalyst system SIL₃B/V. Addition of ethyl trichloroacetate is possible in the ionic liquid medium and it further increases the activity up to 7 tons PE (mol V)^?1 (0.5 h)^?1. In contrast, application of the imidazolium ionic liquid to the SIL system or application the analogous catalyst system without the ionic liquid results in lower activities. The obtained polyethylene (PE) is a linear polymer, with molecular weight (M_w) of over 10⁶ g mol^?1 and molecular weight distribution (M_w/M_n) in the range 1.6–1.9, and has a characteristic fluffy or fibrous shape. In contrast, the PE samples obtained using the systems without ionic liquid reveal broader M_w/M_n (2.5–3.7) and replicate the support morphology. © 2016 Society of Chemical Industry     

Preparation and characterization of precipitated zinc silicates

The study aimed to obtain highly dispersed particles of zinc silicate, a potential filler of polymers or a paint pigment, by precipitation from solutions of sodium metasilicate and of zinc salts. The technique of silicate precipitation was worked out, and the conditions causing precipitation were optimized. The temperature, sodium metasilicate solution flow rate and concentration of zinc salts were selected so as to obtain silicates of the lowest possible bulk density, and which had low water‐absorbing capacity and high paraffin oil‐absorbing capacity. In the study, the effects of precipitation parameters were examined on the principal physicochemical properties of the silicates, the structure and uniform character of silicate particles, particle size distribution, and the surface morphology. Particular attention was devoted to the particle size distribution and the tendency to form primary agglomerates (aggregates) and secondary agglomerates, using dynamic light scattering (DLS). Studies were undertaken to develop a technique which could prevent formation of silicate particle agglomerates. With this aim, the silicates' surface was modified either during their precipitation or by the so‐called dry technique. For the modification, silane coupling agents were applied. The extent of silicate surface hydrophobicity was examined by estimation of the enthalpies of immersion of the modified silicate surface. The silicates obtained were tested as fillers of rubber mixtures (in butadiene–styrene rubber). © 2003 Society of Chemical Industry     

Effect of surfactants on the size and morphology of the silica particles prepared by an emulsion technique

Studies were performed on precipitation of silica in an emulsion system from aqueous solution of sodium metasilicate and hydrochloric acid. Cyclohexane formed the organic phase. Anionic, cationic and non-ionic surfactants were used as emulsifiers. Optimum composition of the emulsion and optimum parameters for the precipitation reaction were established. Effects of a dispersing medium on quality of the produced silicas were examined. The silicas were subjected to physicochemical characterization. Bulk density, water, dibutyl phthalate and paraffin oil absorbing capacities were measured. Surface charge of the obtained dispersion, particle size and shape of the formed silicas were estimated. Specific surface area (BET) was defined and the complete pore characteristics was also presented for the selected silicas. Application of Rokanol K-7 (C_16–22O(CH₂CH₂O)₇H) as an emulsifier resulted in production of almost ideally spherical silica particles of nanometric size and of a monodisperse character.