Papers by Keyword: Mg(OH)₂

Abstract: Polyether sulfone (PES) stands as a widely utilized polymeric membrane in separation technology. However, due to certain undesirable drawbacks encountered in its application, researchers consistently strive to enhance its characteristics and performance. In this study, we delve into the effects of Mg(OH)₂ addition on the characteristics and performance of PES membranes employed for humic acid removal from water. The membrane fabrication involves PES as the primary polymer, NMP as the solvent, and a blend of ethanol and water as non-solvents. Characterization of the membranes encompasses the assessment of functional groups via FTIR, morphological structure through SEM imaging, and porosity evaluation. Notably, the Mg(OH)₂ additive exerted a positive influence on the prepared PES membranes, leading to discernible alterations in the morphological structure, as evident in SEM cross-sectional images. The augmentation of Mg(OH)₂ concentration resulted in increased membrane porosity. The FTIR spectra revealed the presence of water derived from Mg(OH)₂ crystals. The research yielded notable results, with the most outstanding membrane exhibiting a pure water flux of 41.6 L/m2·h and a rejection rate of 71%. Furthermore, it displayed a Water Flux Recovery Ratio (FRR) of 72%. These findings underscore the effectiveness of incorporating Mg(OH)₂ as an additive in enhancing the performance of PES membranes for humic acid removal, with promising implications for water purification applications.

Abstract: The Thermal Decomposition Kinetics of Mg(OH)2 Modified with Sodium Dodecyl Benzene Sulfonate (SDBS) by the Liquid Phase Method Was Investigated Using Differential Thermal Analysis and Thermo Gravimetric (DTA-TG) at Different Heating Rates. the Results Show that the Mg(OH)₂ Modified with SDBS Is Mg(OH)₂ with Hexagonal Phase Structure. the Average Apparent Activation Energy of the Decomposition Stages of Mg(OH)₂ Modified with SDBS Was Calculated Using the Doyle-Ozawa and Kissinger Methods as 169.13 Kj•mol-1. the Reaction Order and Frequency Factor Can Be Also Determined by Kissinger Method. the Kinetics Equations of Reaction Were Deduced as Dα/dt = (5.71×10¹²/β) e^-20340/T (1-α)^1.52.

Abstract: A zinc hydroxystannate-coated mineral grade Mg(OH)₂ (ZHSCMH) was synthesized as flame retardant and smoke suppressant for flexible poly (vinyl chloride). The powder of ZHSCMH was characterized by the x-ray diffraction (XRD) and scanning electron microscopy (SEM). The flame retardancy, smoke suppression and thermal behavior of PVC treated with ZHSCMH and mineral grade Mg(OH)₂ were comparative studied by means of limiting oxygen index (LOI), smoke density rating (SDR), thermogravimetry (TG), differential thermogravimetry (DTG) and SEM. The results show that, ZHSCMH can be used as a high effective flame retardant and smoke suppressant for PVC. The flame retardant of ZHSCMH can effectively promote the crosslinking reaction of poly (vinyl chloride) (PVC) in the first stage, and improve the stability of the char residue in the second stage.

Abstract: The Magnesium hydroxide sulfate hydrate whiskers (5Mg(OH)₂.MgSO₄.3H₂O, abbreviated 513MHSH) have attracted much attention due to its practical applications as filler and reinforcement. However, it is difficult to produce high quality MHSH because plate-like Mg(OH)₂ impurities were formed in high concentrations of OH^- and interaction between Mg²⁺ and OH^-. In this work, to reduce formation Mg(OH)₂, molar ratio of^{Superscript text} magnesium oxide (MgO) and magnesium sulfate (MgSO₄.7H₂O) were controlled. As a result, when low concentration of SO₄^2-, MHSH whiskers co-existed with hexagonal plate Mg(OH)₂. The molar ratio of MgSO₄.7H₂O/MgO was high, uniform MHSH whiskers were formed without Mg(OH)₂. In addition, appropriate amount of NH₄OH has affected formation of high quality MHSH. Their morphologies and structures were determined by powder X-ray diffraction (XRD) scanning electron microscopy (SEM) and thermo-gravimetric analyzer (TGA)

Abstract: Paper properties, including physical properties and optical properties, fiber quality analysis and COD in the pulp effluent were used to investigate the effects of substituting Mg (OH)₂ for NaOH on the properties of poplar APMP in this paper. The results from fiber quality analysis showed that increasing the substitution levels of Mg (OH)₂ for NaOH in the poplar APMP could increase the content of fiber fines,the pulp had shorter average length,and levels of kinking and curl reduced.The results of paper properties analysis ,including physical properties and optical properties ,showed that the bulk and light scattering coefficient of handsheets could be improved,while the physical strength and brightness couled be decreased after using Mg (OH)₂.The research for COD in the pulp effluent showed that it could reduce content of COD in the pulp effluent after substituting Mg (OH)₂ for NaOH on the properties of poplar APMP,so that clean production can come true easierly,while it could retrench the cost of production and yield good economic returns.

Abstract: Using Mg(NO₃)₂·6H₂O as raw materials, Mg(OH)₂ crystals were synthesized by a composite-hydroxide-mediated(CHM) method at 160-200 °C for 24 h. Hexagonal plates Mg(OH)₂ crystal were formed at high content of magnesium nitrate. The size of the plates increased to 5-15 μm while the content of magnesium nitrate was 30 mmol. The strength of (001) plane became stronger than (101) plane with the high content of magnesium nitrate, and this tendency became more obvious at high magnesium nitrate concentration. It is explained that the more Mg²⁺ ion fill the polar plane. The strength of (001) plane became stronger than (101) plane at high temperature. It can be explained Mg(OH)₂ crystal become more steady with more non-polar plane at high temperature, and the shape of the sample showed a change from irregular to cubic shape with heated temperature increase. It indicates that the Mg(OH)₂ crystal growth benefits from high temperature. It is conjectured that the connecting of the [Mg(OH)₆]⁴⁺ basic units with the common edges change into common vertex angle.

Abstract: The present work sought to make a contribution to the study on application of Mg(OH)₂ in peroxide bleaching of the wheat straw soda-AQ pulp. The results showed that: (1) for an unbleached pulp, when 24-73% of the NaOH was replaced with Mg(OH)₂, a higher brightness and viscosity were achieved comparing to the NaOH as the sole alkaline source. The brightness and viscosity of the bleached pulp at 48% of Mg(OH)₂ replacement were respectively 6.4%ISO and 107 mL.g^-1 higher than those of the NaOH as the sole alkaline source. (2) for a chelated oxygen-delignified pulp, the brightness of bleached pulp at 24% Mg(OH)₂ replacement was considerable to that of the NaOH as the sole alkaline source, and at 48% Mg(OH)₂ replacement 2.8% ISO lower than that of the NaOH as the sole alkaline source. While the viscosity increased consistently with the increase of Mg(OH)₂, and the COD load of bleaching filtrates at 24-48% Mg(OH)₂ replacement was lower 22-31% than that of the NaOH as the sole alkaline source. Therefore, partial substitution of Mg(OH)₂ for NaOH had positive effects on peroxide bleaching of wheat straw soda-AQ pulp.