Study of In Situ Formation of Magnesium Hydroxide Whisker via Basic Magnesium Chloride Whisker Regulated by Organic Parcels at Low Temperature

In this work, we demonstrate an in situ phase conversion from basic magnesium chloride（BMC） into magnesium hydroxide whisker by using polar organic solvent at low temperature. The morphology and phase composition of magnesium hydroxide whiskers prepared at different reaction temperature, alkali concentration and organic solvent were analyzed by X-ray diffraction（XRD） and scanning electronic microscope（SEM）. It was found that when one of the organic solvents such as absolute ethyl alcohol, butanol, polyethylene glycol（PEG-400）, acetone, et al. was selected as the template, the precursor BMC can transform into whisker-like magnesium hydroxide through precipitate transformation in low temperature and non-hydrothermal system. It can be reasonably explained that the regulation of Mg^2＋ solubility by those organic solvents and the sustained release of Mg^2＋ dissolution by organic adsorption played a significant role in the formation of magnesium hydroxide whisker via BMC whisker as the precursor.

Flame Retardancy, Smoke Suppression Effect and Mechanism of Aryl Phosphates in Combination with Magnesium Hydroxide in Polyamide 6

The flammability, smoke emission behavior and mechanical properties of two oligomeric aryl phosphates [bisphenol A bis（diphenyl phosphate） （BDP） and resorcinol bis（diphenyl phosphate） （RDP）] combined with magnesium hydroxide （MH） in polyamide 6 （PA6） have been investigated. Combining 5 wt% BDP, 50 wt% MH imparts a limiting oxygen index （LOI） of 40.9% and UL94 V-0 rating to PA6, meanwhile the peak rate of smoke release （pRSR）, total release of smoke （TSR） and Izod notched impact strength are 41%, 33% and 233% relative to the corresponding value of 55 wt% MH without BDP, respectively. Dynamic mechanical analysis （DMA） indicates that the improvement of toughness attributes to the enhanced compatibility between MH and PA6 by adding BDP. Furthermore, based on the comprehensive analysis of thermogravimetry （TG）, cone calorimeter and SEM-EDX investigations, possible flame retardancy and smoke suppression mechanisms were revealed. Besides the fuel dilution and barrier effect of MH, the combination of MH and RDP shows an additional flame inhibition effect. The combination of MH and BDP results in a dominant condensed phase barrier effect which leads to obvious reduction on smoke emission and flammability.

Synthesis and characterization of magnesium hydroxide by batch reaction crystallization

Magnesium hydroxide with high purity and uniform particle size distribution was synthesized by the direct precipitation method using MgCl_(2) and NaOH as reactive materials and NaCl as additive to improve the crystallization behavior of the product.The particle size distribution,crystal phase,morphology,and surface area of magnesium hydroxide were characterized by Malvern laser particle size analyzer,X-ray diffraction(XRD),scanning electron microscope(SEM)and Branauer-Emmett-Teller(BET)method,respectively.The purity of products was analyzed by the chemical method.The effects of synthesis conditions on the particle size distribution and water content(filtration cake)of magnesium hydroxide were investigated.The results indicated that feeding mode and rate,and reaction temperature had important effects on water content and the particle size distribution of the product,and sodium chloride improved the crystallization behavior of magnesium hydroxide.The ball-like magne-sium hydroxides with the particle size distribution of 6.0–30.0μm and purity higher than 99.0%were obtained.This simple and mild synthesis method was promising to be scaled up for the industrial production of magnesium hydroxide.

Magnesium hydroxide whisker modified via in situ copolymerization of n-butyl acrylate and maleic anhydride

Magnesium hydroxide(MH) whiskers were modified via in situ polymerization of n-butyl acrylate and maleic anhydride. Sodium dodecyl sulfonate was used as emulsifier. The modifying effect was evaluated by using contact angle and activation index. The thermal stability,functional groups, structure, morphology, phase composition and surface element valence of MH whiskers were characterized by thermogravimetry-differential scanning calorimetry(TG-DSC), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). Results reveal that the contact angle and activation index of modified MH whiskers are 105°and 76.5%, the thermal stability shows little change, and the decomposition temperature ranges between 38 and419 ℃. The copolymer of n-butyl acrylate and maleic anhydride absorbed on the surface of MH whiskers leads to the increased diameter and makes the surface of whiskers be rougher. Furthermore, the absorption of element C on the surface of MH whiskers increases, and the diffraction intensity of C 1 s spectra increases; thus, the compatibility of whiskers in the organic phase can be improved significantly. Lastly, the surface molecular model of MH whiskers modified via in situ copolymerization of n-butyl acrylate and maleic anhydride is established.

Optimal Parameters of Response Surface Methodology for Preparation of Magnesium Hydroxide Flame Retardant

The yield of magnesium hydroxide was investigated via response surface methodology using bischofite and aqueous ammonia as raw materials. The experimental results indicated that the effects of reaction temperature,magnesium ion and aqueous ammonia concentrations on the yield of magnesium hydroxide gradually decreased. In particular,reaction temperature and magnesium ion concentration had a significant influence on the yield. After the regression and fitting of the response value and each factor,the regression equation was obtained. As proven by experiments,the predicted value and actual value showed a good fit. The products of the center experiment were characterized by particle size analysis,scanning electron microscopy,and X-ray diffraction. The results show that the morphology is irregular and shows a lamellar structure. The particles have a narrow size distribution ranging from 0.64 to 0.68 μm of D50 size. The difference in particle size of D10 and D90 is less than 0.91 μm,and the purity very high.

Effect of magnesium hydroxide as cigarette paper filler to reduce cigarette smoke toxicity

The use of magnesium hydroxide(Mg(OH)_(2))was proposed as a filler to replace part of the calcium carbonate(CaCO_(3))in cigarette paper and reduce the toxicity of the smoke from cigarettes.Physical property changes and smoke reducing ability of this possible substitution were effectively studied.The results showed that adding 10%Mg(OH)_(2) could meet the requirements of the physical property of the cigarette paper.Moreover,with the addition of Mg(OH)2 as a filler in the cigarette paper,the pyrolysis temperature of the cigarette paper decreased,while the porosity and specific surface area increased.As a result,the main-stream smoke had a lower smoke total particle matter(STMP),tar,nicotine and carbon monoxide content,and the side-stream smoke also had a lower STMP.

Effect of GMA Polymer Compatibilizers on Highly Filled Composites of Low Density Polyethylene/Magnesium Hydroxide

Functional polymers such as polyethylene grafted glycidyl methacrylate （PE-g-GMA） and ethylene-methyl acrylate-glycidyl methacrylate terpolymer （E/MA/GMA） were used as compatibilizers in the preparation of highly filled composites of polyethylene/magnesium hydroxide（PE/MH）. Comparative studies were performed on the effect of magnesium hydroxide and stearic acid on the interface within polymer and magnesium hydroxide composites. The effect of polymeric compatibilizers on the properties of the composites was studied using tensile and impact tests, torque rheological analysis, differential scanning calorimetry and environmental scanning electron microscopy （ESEM）. The microstructure of highly filled PE/MH composites changed after the addition of functional polymers. The mechanical properties of the composite material increased after compatibilization. The compatibilization processes of PE-g-GMA and E/MA/GMA were different. The grafted polymer was more compatible with polyethylene, which led to a polar polymer phase. In contrast, the tercopolymer tended to adhere to the surface of MH particles.

Synthesis of cation exchange resin-supported iron and magnesium oxides/hydroxides composite for nitrate removal in water

In this study,we reported on the concept and practical use of cation exchange resin(CER)for removing anions in water via pretreating the CER with metal salts.The cation exchange resinsupported iron and magnesium oxides/hydroxides composite(FeMg/CER)was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment.Characteristics of FeMg/CER were determined by techniques such as Fouriertransform infrared spectroscopy,scanning electron microscopy,and Xray diffraction.The results showed that FeMg/CER material had a high nitrate adsorption capacity of 200 mg NO_(3)^()·g^(1)with a fast equilibrium adsorption time of 30 min at pH 5.In addition,it had good durability of at least 10 times of regeneration,which could be applied to practical water and wastewater treatment.

Studies on Y- Potential of Positive Sol of Magnesium Aluminum Hydroxide

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Coordination Structure of Aluminum in Magnesium Aluminum Hydroxide Studied by (27)Al NMR

The coordination structure of aluminum in magnesium aluminum hydroxide was studied by 27Al NMR. The result showed that tetrahedral aluminum (AlIV) existed in magnesium aluminum hydroxide, and the contents of AlIV increased with the increase of the ratio of Al/Mg and with the peptizing temperature. AlIV originated from the so-called Al13 polymer with the structure of one Al tetrahedron surrounded by twelve Al octahedrons.

Study on Isoelectric Point of Magnesium Aluminum Hydroxide

Yoon's equation which predicted point of zero charge of complex oxide should predict the zero point of net charge (ZPNC) of mixture of variable and permanent charge rather than the point of zero charge (PZC) of the variable charge component. The calculated values with modified Yoon's equation agreed with the experimental values.

A Novel Thixotropic Phenomenon——Complex Thixotropic Behavior

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Study on electric property at interface of positive sol of magnesium aluminum hydroxide

The isoelectric point (IEP) and zero point of charge (ZPC) of magnesium aluminum hydroxide were studied by electrophoresis method, potentiometric titration method, and elemental analysis. Results showed that the charge of magnesium aluminum hydroxide was composed of variable charge and permanent positive charge. Because of the permanent positive charge, the IEP and ZPC obtained were higher than calculated. The LEP decreased and ZPC increased as X increased.

A biobased flame retardant towards improvement of flame retardancy and mechanical property of ethylene vinyl acetate

A new biobased flame retardant(MHPA)with remarkable compatibility was synthesized via a facile and low-cost neutralization reaction of magnesium hydroxide(MH)and phytic acid(PA).By blending the prepared MHPA into ethylene vinyl acetate(EVA),the fire retardancy,smoke suppression and mechanical properties of the composites were significantly improved.When 50 wt%of MH was added into EVA matrix,the value of limiting oxygen index(LOI)reached 26.1%.Whereas,when 10 wt%MH in the EVA composites(with initial 50 wt%MH)was replaced by MHPA,the resulted EVA composites had a LOI value of 30.8%,indicating high efficiency of addition of MHPA to improve flame retardancy.Moreover,the heat release rate(HRR)and total smoke production(TSP)of the EVA composites reduced by 54.4%and 27.6%,respectively,suggesting that incorporation of MHPA could effectively hinder rapid degradation of EVA composites during burning process.The fire-retardant mechanism may reside in that the MHPA combined with MH can present the excellent carbonization and expansion effects.This study illustrates that the biobased MHPA has a broad application prospect to develop flame-retardant EVA composites.

Preparation and crystallization kinetics of micron-sized Mg（OH）2 in a mixed suspension mixed product removal crystallizer

Magnesium hydroxide is an important chemi- cal, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal （MSMPR） crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction （XRD）, Scanning Electron Micro- scopy （SEM） and Malvem laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg（OH）2. The spherical Mg（OH）2 with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients （R2） based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the size- dependent growth models.

Town-scale microbial sewer community and H2S emissions response to common chemical and biological dosing treatments

Controlling hydrogen sulfide(H2S)odors and emissions using a single,effective treatment across a town-scale sewer network is a challenge faced by many water utilities.Implementation of a sewer diversion provided the opportunity to compare the effectiveness of magnesium hydroxide(Mg(OH)2)and two biological dosing compounds(Bioproducts A and B),with different modes of action(MOA),in a field-test across a large sewer network.Mg(OH)2 increases sewer p H allowing suppression of H2S release into the sewer environment while Bioproduct A acts to disrupt microbial communication through quorum sensing(QS),reducing biofilm integrity.Bioproduct B reduces H2S odors by scouring the sewer of fats,oils and grease(FOGs),which provide adhesion points for the microbial biofilm.Results revealed that only Mg(OH)2 altered the microbial community structure and reduced H2S emissions in a live sewer system,whilst Bioproducts A and B did not reduce H2S emissions or have an observable effect on the composition of the microbial community at the dosed site.Study results recommend in situ testing of dosing treatments before implementation across an operational system.

Highly efficient and selective removal of low-concentration antibiotics from aqueous solution by regenerable Mg（OH）2

The prevalent presence of fluoroquinolone antibiotics in aquatic environments has attracted considerable attention because of their harmful effects on humans and the ecological environment.Magnesium hydroxide nanocrystals were found to act as a simple and effective adsorbent to remove low-concentration ciprofloxacin(CIP)in aqueous solution.The as-prepared Mg(OH)2 nanocrystals exhibited excellent CIP adsorption performance and high selectivity toward CIP molecules compared with other antibiotics or aromatics,e.g.,norfloxacin(NOR)and eosin B(EB).The adsorbent showed pH-dependent adsorption,indicating that the adsorption process is probably dominated by an electrostatic interaction mechanism.In addition,structural analysis of the adsorbent indicated that coordination and hydrogen bonding between CIP and Mg(OH)2 nanocrystal might also be involved in the adsorption process.Moreover,the adsorbent could be easily recovered by pyrolysis and hydration without significant reduction of adsorption capacity.The superior adsorption behavior of Mg(OH)2 nanocrystal indicates that it may serve as a potential adsorbent material candidate for the selective removal of CIP from aquatic environments.

Composition and morphology of the thermal decomposition products of 3Mg（OH）2·MgCl2·8H2O nanowires

The thermal decomposition of 3Mg（OH）2·MgCl2·8H2O （318MHCH） nanowires synthesized from agglom- erated Mg（OH）2 microspheres was investigated. The influence of heating rate and temperature on the composition and morphology of the products was investigated. Thermogravimetric-differential scan- ning calorimetry, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction showed that increasing the heating rate from I to 20 ℃/min promoted the escape of crystalline water from the 318MHCH nanowires. 318MHCH nanowires were dehydrated stepwise to 310MHCH porous nanowires from room temperature to 320℃, and then to MgO cubic nanoparticles from 420 to 700 ℃. The nanowires retained their one-dimensional morphology, until the phase changed to MgO. The immediate collapse of the one-dimensional structure was attributed to the presence of Mg-O/Cl chains.

Synthesis of Mg(OH)_(2) micro/nano flowers at room temperature

The inexpensive and green method of synthesis for self-assembled micro/nano structures is an important area of emerging research.Such structures can be chemically tuned with predesigned functional properties.Therefore,they hold very good promise for future applications,e.g.,biomedicine,electronic device,solar energy,gas sensing.Here we report for the first time an inexpensive and green method for chemical deposition of magnesium hydroxide(Mg(OH)_(2))micro/nano flowers in thin films on commercial soda lime silica glass substrates at room temperature.Under identical conditions,chemically synthesized Mg(OH)_(2) powders are also prepared in absence of the soda lime silica glass substrates.The condition that favors the growth of micro/nano flowers in thin films is identified from X-ray diffraction(XRD),scanning electron microscopy(SEM),field emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),and energy dispersive X-ray spectroscopy(EDX)data.Finally,the possible growth mechanism of micro/nano flowers in thin films is discussed.