32 research outputs found
Adsorptive removal of cationic dye from aqueous solutions by ZnO/ZnMn<sub>2</sub>O<sub>4</sub> nanocomposite
No full textAdsorption of Acid Red 88 Anionic Dye from Aqueous Solution onto ZnO/ZnMn2O4 Nanocomposite: Equilibrium, Kinetics, and Thermodynamics
No full textPressureless and Low-Pressure Synthesis of Microporous Carbon Spheres Applied to CO2 Adsorption
No full textIn this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO2 adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO2 uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO2 uptake at 25 °C, but had no effect on it at 0 °C
Comprehensive evaluation of early-age hydration and compressive strength development in seawater-mixed binary and ternary cementitious systems
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Early-Age Mechanical Properties of 3D-Printed Mortar with Spent Garnet
No full textThis study determines the effect of spent garnet as a replacement for natural sand in 3D-printed mortar at early ages. Five mixes with different spent garnet amounts were prepared (0%, 25%, 50%, 75% and 100% by volume). The ratio of binder to aggregate remained unchanged. In all mixes the water/binder ratio was assumed as a constant value of 0.375. Tests were performed to confirm the printability of the mix (a path quality test using a gantry robot with an extruder). Determinations of key buildability properties of the mix (green strength and Young’s Modulus) during uniaxial compressive strength at 15 min, 30 min and 45 min after adding water were conducted. A hydraulic press and the GOM ARAMIS precision image analysis system were used to conduct the study. The results showed that an increase in spent garnet content caused a decrease in green strength and Young’s Modulus (up to 69.91% and 80.37%, respectively). It was found that to maintain proper buildability, the recommended maximum replacement rate of natural sand with garnet is 50%. This research contributes new knowledge in terms of using recycled waste in the 3D printing technology of cementitious materials
FMR study of 0.30(Fe
No full textZnO nanocrystals doped with Fe2O3 have been synthesized by the calcination method. Ferromagnetic resonance (FMR) study of 0.3(Fe2O3/0.7(ZnO) nanocomposite has been carried out in the 4–300 K range. The presence of magnetic zinc ferrite ZnFe2O4 nanoparticles with an average crystallite size of 11 nm was identified by XRD. Temperature dependence of the resonance field, linewidth and the integrate intensity calculated from FMR spectra has been determined. Existence of two temperature regimes: high (above 50 K) and low (below 50 K) has been established, further divided into two temperature ranges. The results of FMR study of agglomerated ZnFe2O4 nanoparticles indicate an important role of magnetic interactions, both inter-particle (exchange and dipolar) and intra-particle connected with the core-shell magnetic structure
Raman study of surface optical phonons in ZnO(Co) nanoparticles prepared by hydrothermal method
No full textInfluence of Potassium-Based Activation on Adsorptive Properties of Carbon Spheres Modified with Iron(III) Citrate
No full textComposites synthesized from iron(III) citrate and carbon spheres, and activated with potassium compounds were prepared and then characterized using XRD, SEM, and low-temperature nitrogen adsorption methods. The adsorption properties of the composites toward carbon dioxide were assessed using CO2 uptake measurement, as well as by measuring their selectivity toward carbon dioxide, given their further application as photocatalysts for the reduction of this gas. The effect of changing preparation conditions on the structural and adsorption properties of the material was assessed. The potential strength of such material is a synergistic effect between the high adsorption capacity related to the microporosity of carbon spheres combined with the catalytic properties of iron particles
