Glass-ceramics have been successfully prepared from high-carbon ferrochromium slag (HCFS) and waste glass (WG), and the microstructural characterization and mechanical properties of the glass-ceramics were subsequently investigated. The development of HCFS-based glass-ceramics involves the nucleation and crystallization stages from the parent glass. With the increase in mass ratio of HCFS and WG (R(H/W)) from 0.60 to 1.67, the number of bridging oxygens of Si in the parent glass is reduced, as shown via Raman spectroscopy. Thus, their degree of polymerization decreases with it, and the temperature of nucleation and crystallization increase, which is consistent with the DSC results. The SEM images and EDS results indicate that the increasing value of R(H/W) decreases the crystal grain size and consequently increases the microhardness of the glass-ceramics. But the porosity simultaneously increases, which makes the bending strength increase at first and subsequently decrease. And the optimum properties of HCFS-based glass-ceramic samples in the present work are obtained when R(H/ W) reaches 1.29, that is, a bending strength of 104 MPa and a microhardness of 9860 MPa.
Copper ions were first adsorbed by zeolite 4A synthesized from bauxite tailings, the desorption of Cu(II) using NaEDTA solutions was performed, and the recycling of zeolite 4A in adsorption and desorption was systematically investigated. It was observed that the Cu(II) removal efficiency was directly dependent on the initial pH value. The maximum removal efficiency of Cu(II) was 96.2% with zeolite 4A when the initial pH value was 5.0. Cu(II) was completely absorbed in the first 30 min. It was also observed that the desorption efficiency and zeolite recovery were highly dependent on the initial pH and concentration of NaEDTA in the solution. The desorption efficiency and percent of zeolite recovered were 73.6 and 85.9%, respectively, when the NaEDTA solution concentration was 0.05 mol L and the pH value was 8. The recovered zeolites were pure single phase and highly crystalline. After 3 cycles, the removal efficiency of Cu(II) was as high as 78.9%, and the zeolite recovery was 46.9%, indicating that the recovered zeolites have good adsorption capacity and can repeatedly absorb Cu(II).
Summary
In this work, a novel Na2SO4·10H2O/fly ash shape‐stabilized phase change material mortar (PCM mortar) was prepared for building energy efficiency, in the context of energy conservation and environmental protection. The working, mechanical, and thermal properties of this proposed PCM mortar were investigated. The experiment results showed that the incorporation of PCMs greatly increased the thermal inertia of the mortar, while corresponding compressive strength was little affected. Specifically, when the blending amount of PCMs reached 15%, the thermal storage capacity of mortar sample (PCM‐15) was 6.18 × 104 kJ/m3, which is 2.4 times of that for mortar sample without PCM (OPC) evaluated by theoretical calculations, while the corresponding compressive strength of mortar sample (PCM‐15) still remained above 31 MPa. Furthermore, the effects of PCM mortar on thermal comfort and energy use of buildings were studied by using experiment and simulation methods, respectively. The control experiments showed that PCM mortar can effectively alleviate the influence of outdoor temperature on indoor temperature compared with OPC. Temperature difference between PCM‐15 and OPC board can reach 4.6°C (inner surface) and 8.6°C (outer surface), respectively. Meanwhile, temperature difference of internal space reached 1.2°C. The simulation results showed that the energy consumption per unit building area was reduced by 4.4 and 18.7 kg/m2 in Guangzhou and Harbin, respectively, with PCM mortar as the envelope structure. Hence, the proposed PCM mortar showed significant thermal and mechanical properties and had broad application prospects in regulating indoor temperature and constructing energy‐efficient buildings.
Glass-ceramics were successfully prepared from high-carbon ferrochromium slag (HCFS), and the optimum heat-treatment conditions were determined by analysis of the crystallization kinetics. The parent glass is first prepared in five different ratios of HCFS to waste glass (R(H/W)), then heat-treated separately at five heating rates (α) and monitored by DSC. As the value of R(H/W) increases from 0.60 to 1.67, the crystallization activation energy (E c) decreases from 253.41 to 183.52 kJ/mol. The nucleation and crystallization temperatures decrease from 641.7 to 612.2°C, and 822.8 to 814.7°C, respectively, and both are lower than that of ordinary metallurgy slag. These results indicate that using HCFS to produce glass-ceramics both facilitates its production and saves energy. The crystallization index (n) increases with
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