Addition Of Magnesium Hydroxide Research Articles

Magnesium hydroxide addition reduces aqueous carbon dioxide in wastewater discharged to the ocean

Ocean alkalinity enhancement (OAE) reduces the concentration of dissolved carbon dioxide (CO2) in seawater, leading to atmospheric carbon dioxide removal (CDR). Here we report laboratory experiments and a field-trial of alkalinity enhancement through addition of magnesium hydroxide to wastewater and its subsequent discharge to the coastal ocean. In wastewater, a 10% increase of average alkalinity (+0.56 mmol/kg) led to a 74% reduction in aqueous CO2 (−0.41 mmol/kg) and pH increase of 0.4 units to 7.78 (efficiency 0.73 molCO2/mol alkalinity). The alkalinization signal was limited to within a few metres of the ocean discharge, evident as 27.2 μatm reduction in CO2 partial pressure and 0.017 unit pH increase, and was consistent with rapid dilution of the alkali-treated wastewater. While this proof of concept field trial did not achieve CDR due to its small scale, it demonstrated the potential of magnesium hydroxide addition to wastewater as a CDR solution.

Effect of magnesium hydroxide and graphene nanoplatelets on the properties of peroxide cross‐linked linear low‐density polyethylene nanocomposite

AbstractLinear low‐density polyethylene (LLDPE) and different concentrations (5‐20 wt%) of magnesium hydroxide (MAH) as a filler either with or without the addition of graphene nanoplatelets (GNPs) were peroxide cross‐linked using dicumyl peroxide as a cross‐linking agent in a twin‐screw extruder. The mechanical, thermal stability, flame retardancy, morphological, and rheological properties of the prepared samples were investigated. The mechanical properties of the peroxide cross‐linked LLDPE samples with higher MAH and GNP in the matrix were significantly improvement compared to neat LLDPE. This indicates that the addition of MAH and GNP to the peroxide cross‐linked LLDPE matrix could be suitable reinforcing fillers to achieve better and enhanced mechanical properties, particularly tensile strength. Conversely, a significant decrease in the elongation at break values was found for peroxide cross‐linked LLDPE samples compared to neat LLDPE. Similarly, results of thermogravimetric analysis revealed remarkable thermal stability enhancement in the peroxide cross‐linked LLDPE samples with higher MAH and GNP compared to neat LLDPE. The results from UL94 test demonstrated that the peroxide cross‐linked LLDPE samples comprising higher MAH with GNP exhibited improved V = 0 rating compared to poor no rating (NR) for neat LLDPE. Furthermore, the scanning electron microscope and digital images shown improved flame retardancy properties for these samples because of the formation of protective char layer on the sample surface. The complex viscosity for the peroxide cross‐linked LLDPE samples, at lower frequency, increased with increasing MAH loading and further addition of GNP compared to neat LLDPE.Highlights Cross‐linked polyethylene with flame retardant (FR) and nanofiller were prepared. Effects of cross‐linking and FR on the final properties of the polymer were studied. 20wt% FR with 3 phr nanofiller promoted the final properties of the polymer. Higher filler loading in the polymer improved flame retardancy and thermal stability. Combined effect of cross‐linking and FR has shown major improvement.

Preparation and properties of a new core–shell-modified gel dry-water powder

To improve the spray fire extinguishing performance of magnesium-hydroxide gel dry-water powder, this paper studied the preparation speed, material mass ratio, fluidity, bulk density, pressure resistance, and fire extinguishing performances of modified dry-water powders. A pure-water dry-water powder was modified by applying an effective extinguishing component, magnesium hydroxide, and a coagulant, Gellan gum. The preparation process parameters of the pure-water dry-water powder system were optimized. The results showed that the optimal process parameters for the preparation of dry-water powder were a rotation speed of 4000 rpm, an SiO2:H2O ratio of 9:100, and a stirring time of 3 min. The resting angle of magnesium-hydroxide gel dry-water powder was below 28°, with good fluidity. The bulk density of the dry-water powder was lower than that of the BC-class dry powder extinguishing agent, and the bulk density of the magnesium-hydroxide gel dry-water powder was 0.467 g·mL−1. With the increase in pressure, the damage rate of the dry-water powder increased. The addition of magnesium hydroxide and Gellan gum significantly improved the pressure resistance of the dry-water powder. At a pressure of 1.4 MPa, the magnesium-hydroxide gel dry-water powder was only 11% damaged. The performance of the magnesium-hydroxide gel dry-water powder was improved by 37.21% compared with the average cooling rate of the BC-class dry powder extinguishing agent used as a control fire extinguishing group. The dry-water powders produced by modifying the dry-water powders with magnesium hydroxide and Gellan gum could withstand higher driving pressures, and they had improved powder diffusion, reduced powder charge volume, and increased fire extinguishing properties compared with those of the other dry-water powders.

Thermal characteristics and recoverability of early-age mortar consisting of a flame retardant Mg(OH)2

Since fire accidents happen randomly and many of them occur during the construction period of buildings, it is of great significance to study the thermal behavior of early-age mortar and its recoverability after re-curing. In this study, the thermal characteristics and recoverability of early-age mortars with addition of magnesium hydroxide (Mg(OH)2) were experimentally investigated. The mechanical properties and micro characteristics of early-age mortars before heating, after heating, and re-cured after heating are investigated in detail. Experimental results show that compression strength reduces significantly after heating, which can recover to a certain level after re-curing when exposed to temperature below 400 °C. For early-age mortars exposed to temperature over 600 °C, the strength cannot recover. NMR results illustrate that the addition of magnesium hydroxide to mortars can slow down the pore growth rate during heating, and decrease pore numbers and pore size during re-curing. The research results indicate that the addition of Mg(OH)2 to mortar can not only improve the ability to resist high temperature, but also improve the ability of mortars to repair itself after being damaged by high temperature.

Flammability, morphological and mechanical properties of sugar palm fiber/polyester yarn-reinforced epoxy hybrid biocomposites with magnesium hydroxide flame retardant filler

This paper aims to study the surface morphology, flammability and tensile properties of sugar palm fiber (SPF) hybrid with polyester (PET) yarn-reinforced epoxy composite with the addition of magnesium hydroxide (Mg(OH)2) as a flame retardant. The composites were prepared by hybridized epoxy and Mg(OH)2/PET with different amounts of SPF contents (0%, 20%, 35% and 50%) using the cold press method. Then these composites were tested by horizontal burning analysis, tensile strength testing and scanning electron microscopy (SEM) analysis. The specimen with 35% SPF (Epoxy/PET/SPF-35) with the incorporation of Mg(OH)2 as a flame retardant showed the lowest burning rate of 13.25 mm/min. The flame took a longer time to propagate along with the Epoxy/PET/SPF-35 specimen and at the same time producing char. Epoxy/PET/SPF-35 also had the highest tensile strength of 9.69 MPa. Tensile properties of the SPF hybrid with PET yarn (SPF/PET)-reinforced epoxy composite was decreased at 50% SPF content due to the lack of interfacial bonding between the fibers and matrix. Surface morphology analysis through SEM showed uniform distribution of the SPF and matrix with less adhesion, which increased the flammability and reduced the tensile properties of the hybrid polymeric composites. These composites have potential to be utilized in various applications, such as automotive components, building materials and in the aerospace industry.

Thermal and flammability properties of polyethylene composites with fibers to replace natural wood

Composites of high-density polyethylene and lignocellulosic fiber residues from banana, papaya, and peach palm trees, in addition to sponge gourd and coconut fiber, were investigated to identify the least flammable composite as a potential substitute for natural pine wood. The high-density polyethylene/lignocellulosic fiber composites were prepared in a twin-screw extruder, injection molded to obtain specimens, and characterized in terms of thermogravimetry, flammability using the UL-94 burning test and limiting oxygen index, impact resistance and heat deflection temperature. The high-density polyethylene/sponge gourd fiber composite showed the best impact resistance and was selected for further tests, with the addition of 10wt% magnesium hydroxide and (or) rice husk ash as flame retardants. The use of both retardants provided greater thermal stability to the composite. The addition of magnesium hydroxide to the high-density polyethylene/sponge gourd fiber composite improved the flammability properties of horizontal burning and thermal stability and is a potential candidate to replace natural wood.

The antagonistic effect of magnesium hydroxide particles on vascular endothelial activation induced by acidic PLGA degradation products.

Although drug-eluting stents (DESs) are mainly coated with biodegradable polymers such as PLGA and PLLA, their acidic degradation products can alter the local microenvironment and affect the homeostasis of adjacent tissue. Previously, we developed anti-inflammatory PLGA-based materials including magnesium hydroxide (MH) to relieve the side effects caused by PLGA degradation. However, the underlying molecular mechanism of its protective effects has not yet been clarified. Here, we demonstrated the pathological mechanism of vascular endothelial activation caused by PLGA by-products. The PLGA by-products accumulated in HCAECs through MCT1, followed by oxidative stress and the activation of the MAPK/NF-κB signaling pathway. Finally, the PLGA by-products increased the expression of VCAM-1 as well as the secretion of proinflammatory cytokines. However, the addition of MH particles significantly diminished the activation of this molecular pathway and the expression of inflammation-related factors induced by acidic PLGA degradation products. Furthermore, Mg2+ released from MH particles restored endothelial function in both intracellular and extracellular spaces. Taken together, MH particles prevent the accumulation of PLGA degradation products in HCAECs, thereby repressing the associated vascular endothelial activation. These findings on the biochemical mechanisms are expected to provide important clues for addressing the safety issues in nearly all biodegradable polymer-based implants.

Flammability and Mechanical Properties of Arenga Pinnata Fibre/PET Reinforced Epoxy for Fire Retardant Composites

The aim of this paper is to study the effect of magnesium hydroxide burning rate, mechanical properties and surface morphology analysis of Arenga pinnata fibre hybrid with polyester yarn (APF/PET) reinforced epoxy composite with the addition of magnesium hydroxide as flame retardant. The composites were prepared with different amount of fibres (i.e. 0%, 20%, 35% and 50% by weight percent) and two constant material of 5% which are the magnesium hydroxide and the polyester yarn with epoxy resin as the matrix. With the incorporation of the flame retardant the horizontal burning rate of APF/PET reinforced epoxy decreased with the amount of 35% APF. The fibre loading increased to 50% as the mechanical properties of the hybrid composite decreased which due to the lack of interfacial bonding between the fibres and matrix. Surface morphology studies through scanning electron microscopy showed the similar distribution of Arenga pinnata fibres and matrix with less adhesion which reduce the mechanical properties of the hybrid composites.

Effect of Magnesium Hydroxide and Aluminum Hydroxide on the Thermal Stability, Latent Heat and Flammability Properties of Paraffin/HDPE Phase Change Blends.

In this study, paraffin was selected as the phase change material (PCM) and high-density polyethylene (HDPE) as the supporting material to prepare a flame-retardant PCM system. The system consisted of paraffin, HDPE, expanded graphite (EG), magnesium hydroxide (MH) and aluminum hydroxide (ATH). The thermal stability and flame retardancy were studied by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and cone calorimeter test (CONE). The SEM proved that the addition of MH and ATH can produce an oxide film on the surface of the composite material and form a “physical barrier” with the char layer, generated by the expansion of EG, preventing the transfer of heat and oxygen. The TGA test showed that, compared with other flame-retardant systems, the materials with added MH and ATH have a higher thermal stability and carbonization ability, and the amount of char residue has increased from 17.6% to 32.9%, which reduces the fire risk of the material. The flame retardant effect is obvious. In addition, the addition of MH and ATH has no significant effect on the phase transition temperature and latent heat value of PCMs. The CONE data further confirmed that MH and ATH can work with EG to prevent heat release, reduce the total heat release rate (THR) value and effectively suppress the generation of smoke, CO and CO2. The peak heat release rate (PHRR) value also decreased, from 1570.2 kW/m2 to 655.9 kW/m2.

Alkaline flocculation of Microcystis aeruginosa induced by calcium and magnesium precipitates

The biotechnological potential of Microcystis aeruginosa brings requirements for efficient cultivation and harvesting of biomass. Flocculation of M. aeruginosa at alkaline pH induced by calcium or magnesium precipitates was studied under model conditions, in culture medium with/without cellular organic matter (COM). The effect of independent variables (Ca2+, Mg2+, PO43−, and pH) on the zeta potential and turbidity of cells and inorganic precipitates was quantified by response surface methodology. The experimentally obtained flocculation efficiencies (FEs) were compared with predictions of physicochemical interaction (DLVO) models. The results presented here delimited the concentration ranges of Ca2+, Mg2+, PO43−, and pH, resulting in FE > 85%. The DLVO prediction model suggested that for high FE, positively charged precipitates and sufficient precipitate turbidity were required. At pH 10, alkaline flocculation was more advantageous using magnesium precipitates, since it required less phosphate. High FE with COM was achieved at pH 12 when precipitate formation was induced at a low phosphate concentration by the addition of magnesium hydroxide.

Influence of expandable graphite on flame retardancy and thermal stability property of unsaturated polyester resins/organic magnesium hydroxide composites

ABSTRACTAn eco‐friendly flame retardant unsaturated polyester resin (UPR) material was prepared by combination organic magnesium hydroxide (OMH) and expandable graphite (EG). Different from direct addition of magnesium hydroxide (MH) in UPR matrix‐like traditional method, OMH as a reactive monomer participates in the polycondensation reaction of UPR was more effective in improving the compatibility of flame retardant with matrix. Interestingly, the flame retardant UPR composites exhibited a more satisfactory flame retardant effect when a certain amount of 8 wt % EG was added into UPR/OMH matrix because of the synergistic effect between OMH and EG, resulted in the limited oxygen index from 21.7 to 28.5% and UL‐94 test passed V‐0 rating. Moreover, the peak heat release rate, total heat release, and smoke production rate of flame retardant UPR composites significantly reduced. The excellent flame retardancy was due to the formation of a dense and continuous carbon layer in the later stages of combustion. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47881.

Full scale optimisation of sludge dewatering and phosphate removal at Harnaschpolder wwtp (The Hague, NL)

Abstract At Harnaschpolder wwtp phosphate removal from wastewater and sludge dewatering is optimised by dosing magnesium hydroxide to digested sludge. To optimise sludge dewatering and phosphate removal, a full-scale test has been executed since August 2015 using temporary equipment. In this test magnesium hydroxide is added to the digested sludge buffer. Significant positive results are achieved. An excellent quality of the reject water is obtained, through which the phosphorus load in this reject water returned to head of works is negligible. This decrease in combination with other optimisations are beneficial for the biological phosphorus removal process. In 2016 the phosphorus effluent quality remained constant, while 42% less iron chloride was added to meet the legal phosphorus effluent quality requirements (yearly moving average Ptotal < 1.0 mg P/l). The polymer usage decreased by 25% and the year average dry matter content of the dewatered sludge increased from 22% in 2014 to 24% in 2016. Struvite scaling or blockage is avoided in piping, pumps or dewatering equipment, through optimised control of dosage of magnesium hydroxide. The full-scale test results prove that the addition of magnesium hydroxide to digested sludge leads to a significant cost reduction and major environmental benefits. In 2017 a permanent installation will be realised. The magnesium hydroxide dosage will be further optimised based on lessons learnt. Also an improved operation control of sludge dewatering is possible through additional in-line measurements for dry solids content of dewatered sludge. It is therefore expected that results will further improve concerning the use of iron chloride and polymers, dry solids content of dewatered sludge and phosphate effluent quality. Through this optimisation, the operating costs1 of Harnaschpolder wwtp are reduced by over 4%. The return on investment is estimated at 1.5 years.

Activated reaction synthesis of silicon oxynitride from silica and silicon nitride

This study investigates the preparation of samples with equimolar parts of silica and silicon nitride and the subsequent reaction synthesis of silicon oxynitride. The influence of the raw material and the processing parameters on the conversion yield was analyzed. In detail, the effects of the silica crystallinity and of the grain size of the silicon nitride were investigated. Furthermore, the reaction synthesis was activated by magnesium hydroxide or calcium hydroxide. The samples were prepared by slip casting in plaster molds. Firstly, the optimal dispersant type, a synthetic polyelectrolyte, was determined. For the batches with the finer silicon nitride the measured optimal amount was 0.6 wt%. For the batches with the coarser silicon nitride it was 0.18 wt%. From the cast and demolded samples, broken pieces were fired at 1550 °C for 1, 8 or 15 h in nitrogen atmosphere. The conversion yield of silicon oxynitride was analyzed by quantitative X-ray diffraction. The fraction of silicon oxynitride increased with extended holding time at the sintering temperature, by the use of fine silicon nitride, and by the addition of magnesium hydroxide as sintering additive. The silica crystallinity had no statistically significant effect. The obtained maximum conversion yield was 92 wt%.

Induced Struvite Precipitation of Anaerobically Digested Biosolids Stream at NYC’s Wards Island WRRF Through the Addition of Magnesium Hydroxide

Induced Struvite Precipitation of Anaerobically Digested Biosolids Stream at NYC’s Wards Island WRRF Through the Addition of Magnesium Hydroxide

Performance of Palm Oil Clinker as a Bio-Filler with Hybrid Fillers in Intumescent Fire Protective Coatings for Steel

Intumescent coatings are an effective method for fire protection of steel structures. The search for more environmental friendly intumescent coatings has led to the utilization of palm oil clinker (POC) as a bio-filler in solvent-borne intumescent coatings in order to improve fire protection performance, mechanical strength and water resistance of steel structures. In this research, POC and hybrid fillers are mixed with an acrylic binder and then blended with flame-retardant additives in order to produce intumescent coatings. The samples were tested using Bunsen burner test, thermogravimetry analysis, surface spread of flame test, field emission scanning electron microscopy, static immersion test, and adhesion strength test. It was found that the optimum composition of POC and hybrid fillers gives the best fire protection performance with the lowest equilibrium temperature (171.3°C), high thermal stability, good water resistance and excellent mechanical properties. The results of the surface spread of flame test show that Sample A3, A4, and A6 were classified as Class 1, which is the best classification. For Sample A6 (a hybrid formulation), the addition of aluminium hydroxide gives better water resistance with the lowest rate of weight change (<0.2%), while the addition of magnesium hydroxide enhances the bonding strength of the coating up to 125% compared with Sample A1 which only has a single filler POC. It can be concluded that the optimum composition of POC and hybrid fillers results in intumescent coating with the greatest fire protection performance.

The corrosion of carbon steel in nitrate hydrates used as phase change materials

Corrosion behaviour of mild carbon steel was studied in five assumed phase change materials: magnesium nitrate hexahydrate, magnesium nitrate hexahydrate with the addition of magnesium hydroxide (0.5 wt%) and strontium hydroxide (0.5 wt%), respectively, at 90 °C; calcium nitrate tetrahydrate at 50 °C and a mixture of magnesium nitrate hexahydrate and calcium nitrate tetrahydrate (1:1) at 72 °C. Corrosion rate was studied via mass loss and the steel specimens were analysed after the study. The corrosion rate of steel specimens is over recommended limit except of the mixture Mg(NO3)2 · 6 H2O − Ca(NO3)2 · 4 H2O (1:1). Steel can be used for the long‐term service in this mixture while in the other cases it can be used only with caution based on the specific application.

Influence of pH Modifiers and HPMC Viscosity Grades on Nicotine–Magnesium Aluminum Silicate Complex-Loaded Buccal Matrix Tablets

Hydroxypropyl methylcellulose (HPMC) tablets containing nicotine-magnesium aluminum silicate (NCT-MAS) complex particles and pH modifiers, namely, sodium chloride, citric acid, and magnesium hydroxide, were prepared using the direct compression method. The effects of HPMC viscosity grades and pH modifiers on NCT release and permeation of the matrix tablets were examined. The results showed that the higher the viscosity grade of HPMC that was used in the tablets, the lower was the unidirectional NCT release rate found. The unidirectional NCT permeation was not affected by the viscosity grade of HPMC because the NCT diffusion through the mucosal membrane was the rate-limiting step of the permeation. Incorporation of magnesium hydroxide could retard NCT release, whereas the enhancement of unidirectional NCT release was found in the tablets containing citric acid. Citric acid could inhibit NCT permeation due to the formation of protonated NCT in the swollen tablets at an acidic pH. Conversely, the NCT permeation rate increased with the use of magnesium hydroxide as a result of the neutral NCT that formed at a basic microenvironmental pH. The swollen HPMC tablets, with or without pH modifiers, gave sufficient adhesion to the mucosal membrane. Furthermore, the addition of magnesium hydroxide to the matrix tablets was the major factor in controlling buccal delivery of NCT. This study suggests that the NCT-MAS complex-loaded HPMC tablets, which contained magnesium hydroxide, are potential buccal delivery systems of NCT.

Research and Preparation of Halogen-free Flame-retardant Polypropylene

Two different types of magnesium hydroxide namely, platy magnesium hydroxide (MH) and magnesium hydroxide sulfate hydrate (HMOS) whiskers were used to fill with Polypropylene (PP) in this study. Addition of MH and HMOS enhanced flame retardancy of PP, but the filler content needed to reach 40wt% loading. Either MH or HMOS reduced the mechanical properties of PP, due to the poor adhesion between PP matrix and filler in SEM observation. However, PP/HMOS composites showed higher tensile strength than PP/MH composites.

Pyrolysis properties and kinetic model of an asphalt binder containing a flame retardant

AbstractIn this study, thermogravimetry (TG) experiments were employed to study the influence of magnesium hydroxide (MH) on the pyrolysis characteristics of an asphalt binder. Pyrolysis models of the asphalt binder were developed to reveal the flame‐retarding mechanism of MH. The TG experimental results showed that the pyrolysis process of the asphalt binder in N2 was a one‐stage reaction. The asphalt binder containing MH had a higher residue yield ratio at a high temperature, and TG and differential TG curves showed a dramatic shift toward higher temperatures with an increase in the MH concentration; this indicated that MH inhibited the thermal decomposition of the asphalt binder. By optimal identification of the pyrolysis mechanism function, the pyrolysis reaction of the asphalt binder was found to follow the model of one‐dimensional diffusion (parabolic law), whereas that of the flame‐retarding asphalt binder followed the model of three‐dimensional diffusion (the Ginstling–Brounshtein equation). On the basis of the models, the calculation results for the pseudo activation energy indicated that the thermal stability of the asphalt binder in the pyrolysis process was obviously improved by the addition of MH. We conclude that the flame retardancy of asphalt binders can be enhanced by the use of MH, and MH may be a potential flame retardant for asphalt binders used in tunnel asphalt pavement. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Flame-Retardant Polypropylene Composites with Magnesium Hydroxide Encapsulated by Polypropylene Grafted with Maleic Anhydride

A novel surface-treated magnesium hydroxide (MH) was prepared through the encapsulation of polypropylene grafted with maleic anhydride (PP-g-MA) for the flame retardance of polypropylene (PP). Compared with surface-treating inorganic flame retardants by using conventional modifiers, this method possesses lower cost and better effects. Due to the interaction between maleic anhydride group and hydroxyl group and the similarity for the resin encapsulating inorganic particles (PP-g-MA) and matrix resin (PP), better compatibility and dispersion of MH in PP can be obtained. Therefore, it showed that MH encapsulated by PP-g-MA significantly improved the processablity, flame retardancy, and mechanical properties of the flame retardant composites. Additionally, the effects of the modified MH on the crystallization behavior of PP were also investigated through differential scanning calorimetry (DSC). Interesting results that PP-g-MA and MH had heterogeneous nucleation effect were found. Both the crystallization temperature and the crystallinity were increased by addition of MH encapsulated by PP-g-MA.