Modified and unmodified zinc oxide as coagent in elastomer compounds

The aim of this work was to study the activity of unmodifi ed and modifi ed ZnO in the peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR) and ethylene-propylene copolymer (EPM). In the first step, zinc oxide was obtained by emulsion precipitation. Maleic acid was introduced onto the surface of ZnO using an in situ method. The unmodifi ed and modifi ed zinc oxide was characterized using dispersive and morphological analysis, BET surface area analysis, and elemental, spectroscopic and thermal analysis. In the second stage of the research, the ZnO/MA systems were incorporated into the structure of elastomer compounds improving the kinetic and mechanical properties of vulcanizates. The proposed modifi cation method had a favorable effect on the physicochemical properties of the zinc oxide and on the kinetic and mechanical properties of the vulcanizates. This study demonstrated that modifi cation of zinc oxide by maleic acid is a promising technique

Functionalized Materials as a Versatile Platform for Enzyme Immobilization in Wastewater Treatment

Purpose of Review Untreated wastewater discharge can significantly and negatively impact the state of the environment. Rapid industrialization and economic development have directly contributed to land and water pollution resulting from the application of many chemicals such as organic dyes, pharmaceuticals, and industrial reagents. The removal of these chemicals before effluent discharge is crucial for environmental protection. This review aims to explore the importance of functionalized materials in the preparation of biocatalytic systems and consider their application in eliminating water pollutants. Recent Findings Wastewater treatment methods can be classified into three groups: (i) chemical (e.g., chemical oxidation and ozonation), (ii) physical (e.g., membrane separation and ion exchange), and (iii) biological processes. Biological treatment is the most widely used method due to its cost-effectiveness and eco-friendliness. In particular, the use of immobilized enzymes has recently become more attractive as a result of scientific progress in advanced material synthesis. The selection of an appropriate support plays an important role in the preparation of such biologically active systems. Recent studies have demonstrated the use of various materials for enzyme immobilization in the purification of water. Summary This review identifies and discusses different biocatalytic systems used in the enzymatic degradation of various water pollutants. Materials functionalized by specific groups can serve as good support matrices for enzyme immobilization, providing chemical and thermal stability to support catalytic reactions. Enzymatic biocatalysis converts the pollutants into simpler products, which are usually less toxic than their parents. Due to immobilization, the enzyme can be used over multiple cycles to reduce the cost of wastewater treatment. Future studies in this field should focus on developing new platforms for enzyme immobilization in order to improve degradation efficiency

Synthesis of ZnO mesoporous powders and their application in dye photodegradation

Mesoporous ZnO materials have been synthesized through chemical deposition of different precursors from aqueous or water-ethanol solutions followed by their thermal decomposition at 400°C in air. The microstructure and morphology of the precursors and obtained ZnO powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption-desorption (BET) methods. The structure of the precursor and physico-chemical properties of final zinc oxide powders were shown to be considerably influenced by the presence of Cl– ions and ethanol in solution. In water-ethanol solutions, Zn5(OH)8Cl2∙H2O or Zn5(OH)8(NO3)2∙(H2O)2 precursors are formed, while ZnO particles are directly deposited from aqueous solution. The photocatalytic activity of the synthesized ZnO materials was evaluated by the decolorization of Rhodamine B (RhB) upon UV irradiation. The ZnO powders have demonstrated high photocatalytic efficiency, enabling decomposition of 81.497.4 % RhB within 3 hours. The increased photocatalytic efficiency of ZnO prepared by annealing of Zn5(OH)8Cl2∙H2O precursor or deposited directly from aqueous chloride-containing solutions can be originated from the presence of Cl-containing compounds remaining after thermal treatment of simonkolleite as well as from introduction of Cl-dopant in ZnO.publishe

Characterization of amino-, epoxy- and carbonyl-functionalized halloysite and its application in the immobilization of aminoacylase from Aspergillus melleus

Functionalized halloysite was used as a support for the immobilization of an enzyme. The surface of halloysite was modified with amino (–NH), epoxy (–C(O)C) and carbonyl (–C=O) groups. Both unmodified and modified forms of the support underwent a comprehensive physicochemical and structural evaluation, including morphological, structural, thermogravimetric and spectroscopic analysis. Aminoacylase from Aspergillus melleus was used as the enzyme in the immobilization process. The process of immobilization by adsorption was performed for 1, 6 and 24 h using different concentrations of enzyme solution (0.5, 1 and 3 mg/cm3). The quantity of aminoacylase loaded onto the support was calculated by the Bradford method. Free and immobilized aminoacylase were used to catalyze the deacetylation of N-acetyl-L-methionine. Additionally, the thermal and chemical stability of the obtained biocatalytic systems were evaluated, as well as the reusability of the immobilized systems. The biocatalytic system with amino groups demonstrated activity above 70% in the pH range 4–9 and 60% in the temperature range 30–70 °C. Aminoacylase immobilized on amino-functionalized halloysite also retains around 50% of its initial activity after five reaction cycles

Zinc Oxide—From Synthesis to Application: A Review

Zinc oxide can be called a multifunctional material thanks to its unique physical and chemical properties. The first part of this paper presents the most important methods of preparation of ZnO divided into metallurgical and chemical methods. The mechanochemical process, controlled precipitation, sol-gel method, solvothermal and hydrothermal method, method using emulsion and microemulsion enviroment and other methods of obtaining zinc oxide were classified as chemical methods. In the next part of this review, the modification methods of ZnO were characterized. The modification with organic (carboxylic acid, silanes) and inroganic (metal oxides) compounds, and polymer matrices were mainly described. Finally, we present possible applications in various branches of industry: rubber, pharmaceutical, cosmetics, textile, electronic and electrotechnology, photocatalysis were introduced. This review provides useful information for specialist dealings with zinc oxide

Zinc Oxide—From Synthesis to Application: A Review

Zinc oxide can be called a multifunctional material thanks to its unique physical and chemical properties. The first part of this paper presents the most important methods of preparation of ZnO divided into metallurgical and chemical methods. The mechanochemical process, controlled precipitation, sol-gel method, solvothermal and hydrothermal method, method using emulsion and microemulsion enviroment and other methods of obtaining zinc oxide were classified as chemical methods. In the next part of this review, the modification methods of ZnO were characterized. The modification with organic (carboxylic acid, silanes) and inroganic (metal oxides) compounds, and polymer matrices were mainly described. Finally, we present possible applications in various branches of industry: rubber, pharmaceutical, cosmetics, textile, electronic and electrotechnology, photocatalysis were introduced. This review provides useful information for specialist dealings with zinc oxide

Structural Characterisation of ZnO Particles Obtained by the Emulsion Precipitation Method

Zinc oxide was obtained by precipitation in an emulsion system with zinc acetate used as a precursor of ZnO and potassium hydroxide or sodium hydroxide as a precipitating agent. The cyclohexane, as an organic phase, and a nonionic surfactant mixture were also used for preparation of the emulsion. By applying modifications of the ZnO precipitation process, such as changing the precipitating agent, composition of substrates, and the rate of substrate dosing, some interesting structures of ZnO particles were obtained. The morphology of the modified samples was analysed based on SEM (scanning electron microscope) and TEM (transmission electron microscope) images. Moreover the samples were characterised by determination of their dispersive properties using the noninvasive back scattering method (NIBS), adsorption parameters (BET), and crystalline structure (XRD). Thermogravimetric analysis (TG) as well as infrared spectrophotometry (FT-IR) was also applied. For selected samples their electrical properties (dielectric permittivity and electric conductivity) were also measured. The zinc oxide obtained consisted of particles in the shapes of solids, ellipsoids, rods, and flakes, with size ranging from 164 to 2670 nm and showed well-developed surface area with values as high as 20 m2/g