Magnesium Hydroxide Slurry Research Articles

Magnesium Hydroxide Slurry Coagulation-Adsorption Performance for Reactive Orange Removal Assisted with PAM

Magnesium Hydroxide Slurry Coagulation-Adsorption Performance for Reactive Orange Removal Assisted with PAM

Solubility Data of Potential Salts in the MgO-CaO-SO2-H2O-O2 System for Process Modeling

This review studies unwanted precipitation reactions, which can occur in SO2 absorption processes using a magnesium hydroxide slurry. Solubility data of potential salts in the MgO-CaO-SO2-H2O system are evaluated. The reviewed data can serve as a reliable basis for process modeling of this system used to support the optimization of the SO2 absorption process. This study includes the solubility data of MgSO3, MgSO4, Mg(OH)2, CaSO3, CaSO4, and Ca(OH)2 as potential salts. The solubility is strongly dependent on the state of the precipitated salts. Therefore, this review includes studies on the stability of different forms of the salts under different conditions. The solubility data in water over temperature serve as a base for modeling the precipitation in such system. Furthermore, influencing factors such as pH value, SO2 content and the co-existence of other salts are included and available data on such dependencies are reviewed. Literature data evaluated by the International Union of Pure and Applied Chemistry (IUPAC) are revisited and additional and newer studies are supplemented to obtain a solid base of accurate experimental values. For temperatures higher than 100 °C the available data are scarce. For a temperature range from 0 to 100 °C, the reviewed investigations and data provide a good base to evaluate and adapt process models for processes in order to map precipitations issues accurately.

Least Cost Analysis for Biocorrosion Mitigation Strategies in Concrete Sewers

The changing role of the municipal water and wastewater authorities, together with the need for a sustainable maintenance treatment in the sewer systems, have been the catalysts for the integration of technical and financial information into asset management systems. This paper presents results from a cost-comparative analysis focusing on an annuities calculation for the evaluation of microbiologically induced corrosion (MIC) or biocorrosion mitigation methodologies used in the maintenance of concrete sewers. The replacement cost of deteriorated sewer concrete pipes is high, and MIC mitigation methods can be used to increase the current service life of concrete pipes. From the MIC mitigation methods that are frequently used, the authors examined those of flushing with high-pressure water (i.e., a common method used in Greece), and spraying with magnesium hydroxide slurry (MHS). The authors chose four different cities for the assessment, which presented different sewer characteristics and socioeconomic backgrounds. In addition, all methods for concrete sewer MIC mitigation were compared to the present value of replacement of sewer concrete pipes with new PVC ones. Results showed that flushing with high-pressure water is very cost demanding and should be avoided, while spraying with MHS could be a sustainable and economic solution in the long term.

Gas-liquid mass transfer of carbon dioxide capture by magnesium hydroxide slurry in a bubble column reactor

Magnesium hydroxide (Mg(OH)2) has been considered as a potential solvent for C02 removal of coal-fired power plant and biomass gas. The chemistry action and mass to transfer mechanism of C02-H20-Mg(OH)2 system in a slurry bubble column reactor was described, and a reliable computational model was developed. The overall mass transfer coefficient and surface area per unit volume were obtained using experimental approach and simulation with software assistance. The results show that the mass transfer process of C02 absorbed by Mg(OH)2 slurry is mainly liquid-controlled, and slurry concentration and temperature are main contributory factors of volumetric mass transfer coefficient and liquid side mass transfer coefficient. High concentration of C02 has an adverse effect on its absorption because it leads to the fast deposition of MgC03-3H20 crystals on the surfaces of unreacted Mg(OH)2 particles, reducing the utilization ratio of magnesium hydroxide. Meanwhile, high CO32 ion concentration limits the dissolution of MgC03 to absorb C02 continually. Concentration of 0.05 mol/L Mg(OH)2, 15% vol C02 gas and operation temperature at 35 °C are recommended for this C02 capture system

Mathematical model of precipitation of magnesium carbonate with carbon dioxide from the magnesium hydroxide slurry

A mathematical model is proposed for a precipitation process of magnesium carbonate in a heterogeneous stirred tank reactor. The model includes a description of dissolution of Mg(OH)2, absorption of CO2 and precipitation of MgCO3. The Nernst-Planck equation is used in the dissolution model to maintain the mass balance and electroneutrality. The van Krevelen–Hoftijzer expression is introduced to describe the enhancement effect of reaction between dissolved CO2 and OH− on the mass transfer rate of dissolution and absorption. In the precipitation model, a simplified population balance equation is solved by a moment method for both dissolving and precipitating particles. Unknown precipitation kinetics parameters for Mg(OH)2MgCO3 system are fitted against experimental data and compared with Ca(OH)2CaCO3 system. According to the present analysis, the liquid−solid and gas−liquid mass transfer dominate the global rate of precipitation. The precipitation kinetics and pH have strong influences on the concentration of reactants and the yield of precipitation.

Evaluation of the hydration process of an industrial magnesia compound to obtain struvite crystals: a technique for recovering nutrients

Struvite crystallization as a technique for recovering nutrients from wastewater streams has proven to be an attractive alternative to conventional treatments. The process becomes economically viable with the cost reductions related to the chemical reagents, especially magnesium ions. Thus, this study assessed the processing of a cheap and high-grade industrial magnesia compound in obtaining magnesium hydroxide slurries through a hydration reaction using different hydrating agents (magnesium acetate and sodium chloride solutions and water). The optimum hydration condition was achieved in acetate solution with a conversion rate to hydroxide about 67%. The efficiency of the obtained slurries as alternative reagents on the struvite crystallization process was evaluated in terms of the nutrient removal, NH4+-N and PO43--P. In experimental conditions of Mg2+:NH4+:PO43-ratio equal to 1.5:1.0:1.25 and pH equal to 8.5, the best results were achieved by using the magnesium hydroxide slurry obtained in acetate solution, which promoted removals of about 62% and 67% of NH4+-N and PO43--P, respectively. Finally, instrumental analysis confirmed the formation of struvite crystals in a purity degree that allows its use as a potential fertilizer.

Neutralization of Acid Wastewater and Magnesium Hydroxide Slurry from Seawater Electrolytic Pretreatment

Produced in industrial production processes such as electrolysis, electroplate and metal pickling, industrial wastewater, which contains acids, varieties of heavy metal and whose pH value is less than 6, can be very damaging to our daily life and environment and is an urgent issue to be solved. In recent years, with environmental protection becoming an important issue around the world, and environmental regulations becoming more and more complete, the traditional water treatment technology which can cause secondary pollution is gradually restricted, and this leads to the result that environmental scientists and engineers pay more attention on the development and application of "environmentally friendly" water treatment technology[1]. Of all acid wastewater neutralizers, magnesium hydroxide, known as "green and safe neutralizer"[2, 3], is safe, reliable, non-toxic, harmless, and has high buffer performance, high activity, high adsorption capacity, and no corrosivity compared with traditional strong alkali substances (such as CaO, Ca (OH)2and NaOH, etc.). Therefore magnesium hydroxide has been widely used in the acid wastewater neutralization[4].

Modification of Magnesium Hydroxide Flame Retardant Using Oleic Acid by Wet Method

The magnesium hydroxide (Mg(OH)2, MH) was modified using oleic acid (C17H33COOH, OA) by wet techonlogy. The modification effect of MH was evaluated by activation index and oil absorption rate. The optimum technological conditions were as follows: the concentration of magnesium hydroxide slurry was 35wt%, the oleic acid 2wt% ,temperature 70 °C, time 40 min and a stirring rate 2200 rpm. Additionally, the structure and morphology of the improved modified MH powders were characterized by SEM, XRD, FTIR, TGA-DSC. Compared with the unmodified MH, the modified MH had better dispersibility and hydrophobicity.

Hydrothermal Synthesis and Characterization of Hexagonal Mg(OH)<sub>2</sub> Flame Retardant with Bischofite and NH<sub>3</sub>

Regular hexagonal plates of magnesium hydroxide with high slurry concentration were prepared by hydrothermal reaction without any organic additive or catalyst using bischofite and ammonia as raw materials. The effects of hydrothermal temperature, stirring speed, hydrothermal duration, and dilution multiple on the preparation of Mg(OH)2 flame retardant were investigated. Scanning electron microscopy, X-ray diffraction, and laser particle analysis were performed to characterize the product morphologies, structures, and size distributions. Results indicated that the growth direction of Mg(OH)2 crystal changed, and the regular hexagonal plates of Mg(OH)2 with uniform particle size and high dispersion characteristic formed after hydrothermal modification treatment. A mass fraction of 15.50% Mg(OH)2 of magnesium hydroxide slurry was obtained by high-concentration (4.30mol/L) magnesium chloride and ammonia as the raw materials.

Study on Advanced Pretreatment of Seawater by Electrolysis and Neutralization of Acidic Waste Water with By-Product Magnesium Hydroxide

The advanced pretreatment by electrolysis of Bohai seawater in Tianjin used a diaphragm electrolyzer in the experiment. Removal efficiency and influence factors of the method were analyzed. Results show that turbidity, organic compounds, SDI and chroma of seawater were effectively decreased by electrolysis. Removal efficiency was significantly increased by current density, operation time and inter-electrode distance, and the optimum electrolytic conditions was determined as inter-electrode distance of 2 cm, current density of 15.87 mA·cm-2, operation time of 10 minutes. It was investigated that when the water quality after electrolysis was of pH 8.6, the chroma and turbidity decreasing trend slowed down, with chroma of 0.052 A, removal rate reached 88.4%; the residual turbidity reduced to 2.52 NTU, removal rate reached 90.71%. A PH of about 8.5, CODCr decreasing trend slowed down, and when CODCr < 750 mg/L, it conformed to the requirements of the reverse osmosis water. With the study on neutralization of steel pickling waste liquor by the by-product of magnesium hydroxide, it is found that the quality of treated water reached 3rd level national emissions standards (300-1000 mg/L). Magnesium hydroxide slurry of Cr (VI) removal rate reached 100%, conforming to the 1st level national industrial wastewater discharge standards (< 0.5 mg/L).

Effect of impurity ions on preparation of novel saponifier for rare earth extraction

Magnesium bicarbonate, prepared by the carbonation of magnesium hydroxide slurry, was used as a novel saponifier to eliminate the ammonia nitrogen pollution in the rare earth extraction separation process. The effect of impurity ions introduced by system on the carbonation reaction of magnesium hydroxide was studied in the work. The results showed that the presence of Ca2+ could lead to side reactions so as to reduce the conversion rate of magnesium hydroxide, and a small number of rare earth ions would have great influence on the carbonation reaction. What's more, there was no influence on carbonation reaction with the low concentration of Na+ or Mg2+, the conversion rate of magnesium hydroxide could reach above 96%. This paper showed a practical theory which could provide scientific guidance for the preparation of novel saponifier in rare earth extraction separation process.

A mass transfer model of absorption of carbon dioxide in a bubble column reactor by using magnesium hydroxide slurry

A bubble column reactor was tested and evaluated for carbon dioxide removal from flue gases by using magnesium hydroxide slurry. The study showed that a high CO2 removal efficiency could be achieved. An absorption model was developed for system analysis and CO2 removal data analysis. The overall mass transfer coefficients for CO2-H2O and CO2-Mg(OH)2-H2O systems have been calculated. The chemistry of the system, temperature effects, and changes of equilibrium constants also have been discussed.

Decreasing the peroxide decomposition in the magnesia slurry

AbstractThe peroxide bleaching process for mechanical pulps using weak alkali sources such as magnesium hydroxide (Mg(OH)2), received much attention recently. The magnesia slurry (containing 61.2% Mg(OH)2) can be used for this purpose. In this paper, we studied the manganese‐induced peroxide decomposition in commercial magnesium hydroxide slurry (magnesia). The results showed that peroxide decomposition occurs under the conditions of magnesia based bleaching process. This is due to impurities, particularly manganese in the magnesia slurry. Similar to the conventional sodium hydroxide based process, sodium silicate can effectively decrease the manganese‐induced peroxide decomposition. However, the amount of silicate required is significantly less. It was found that diethylenetriaminepentaacetic acid (DTPA) or its sodium salt, can also be an effective stabiliser in the system. The chemistry of the manganese‐induced peroxide decomposition was discussed.

Magnesium Hydroxide Slurry as a Cost Effective Solution for Effective H<SUB>2</SUB>S Odor and Corrosion Control in Sanitary Sewer Systems

Magnesium Hydroxide Slurry as a Cost Effective Solution for Effective H2S Odor and Corrosion Control in Sanitary Sewer SystemsCorrosion in sanitary sewer systems occurs when hydrogen sulfide (H2S) is biologically converted to sulfuric acid. Although reducing metals was necessary to protect public health, pretreatment has contributed significantly to increased sulfides, leading to heightened H2S odor and ultimately to accelerated corrosion. As the main contributor to odor and corrosion in collection systems, H2S is...Author(s)Aileen GibsonSteve LeykaufChris KnappSourceProceedings of the Water Environment FederationSubjectSession 10: Odor and Corrosion Control in Collection Systems: From the Pipes to the PlantsDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2008ISSN1938-6478SICI1938-6478(20080101)2008:17L.761;1-DOI10.2175/193864708790893062Volume / Issue2008 / 17Content sourceWEFTECFirst / last page(s)761 - 768Copyright2008Word count254

The chemistry and technology of magnesia

Preface. Acknowledgments. 1 History of Magnesia. 1.1 History of Magnesia. 2 Formation and Occurrence of Magnesite and Brucite. 2.1 Introduction. 2.2 Sedimentary Magnesite-Basis for Carbonate Deposition. 2.3 Serpentine Alteration by Hydrothermal Processes. 2.4 Cryptocrystalline Magnesite Formation by Infiltration. 2.5 Crystalline Magnesite-Replacement of Limestone and Dolomite. 2.6 Brucite. 2.7 Worldwide Occurrence of Magnesite and Brucite. 2.8 Physical and Chemical Properties of Magnesite. 2.9 Chemical and Physical Properties of Brucite. 3 Synthetic Magnesia. 3.1 Introduction. 3.2 Composition of Seawater and Brines. 3.3 Process Description. 3.4 Calcination. 3.5 Grinding. 3.6 Packaging. 3.7 Sampling and Testing and In-Process Quality Control. 3.8 Aman Process. 3.9 General Properties of Synthetic Magnesia. 4 Mining and Processing Magnesite. 4.1 Mining Operations. 4.2 Processing Magnesite. 4.3 Gravity Concentration. 4.4 Tertiary Crushing. 4.5 Postcalcination Screening and Grinding. 5 Calcination of Magnesium Hydroxide and Carbonate. 5.1 Calcination of Magnesite. 5.2 Calcination of Magnesium Hydroxide. 6 Furnaces and Kilns. 6.1 Introduction. 6.2 Multiple-Hearth Furnaces. 6.3 Horizontal Rotary Kilns. 6.4 External Water Coolers. 6.5 Shaft Kilns. 7 Postcalcination Processing. 7.1 Introduction. 7.2 Grinding. 8 Physical and Chemical Properties of Magnesium Oxide. 8.1 Introduction. 8.2 Physical Properties of Magnesium Oxide. 8.3 Chemical Properties of Magnesium Oxide. 8.4 Surface Structures of MgO. 8.5 Molecular Adsorption on MgO. 9 Other Magnesia Products. 9.1 Production of Hard-Burned Magnesia. 9.2 Production of Dead-Burned Magnesia. 9.3 Fused Magnesia. 9.4 Magnesium Hydroxide Slurry. 9.5 Purification by Carbonation of Magnesium Hydroxide Slurry. 10 Water and Wastewater Applications for Magnesia Products. 10.1 Introduction to Applications. 10.2 Industrial Wastewater Treatment. 10.3 Advantages of Magnesium Hydroxide in Wastewater Treatment. 10.4 Adsorption of Dyes on Magnesium Hydroxide. 10.5 Biological Wastewater Treatment. 10.6 Bioflocculation and Solids Settling. 10.7 Phosphorus Removal from Wastewater and Struvite Formation. 10.8 Odor and Corrosion Control in Sanitary Collection Systems. 10.9 Acid Mine Drainage. 10.10 Silica Removal from Industrial Plant Water. 11 Magnesia in Polymer Applications. 11.1 Magnesium Hydroxide as a Flame Retardant for Polymer Applications. 11.2 Flame-Retardant Mechanisms. 11.3 Properties Required of Magnesium Hydroxide for Flame-Retardant Applications. 11.4 Novel Applications for Magnesium Hydroxide as a Flame Retardant. 11.5 Polymer Curing and Thickening. 12 Environmental Applications. 12.1 Flue Gas Desulfurization. 12.2 Regenerative Process. 12.3 Remediation Applications. 12.4 Nuclear Waste Disposal. 12.5 Hazardous Spill Cleanup. 12.6 Antibacterial Activity of Magnesium Oxide Powder. 12.7 Carbon Dioxide Sequestration Using Brucite. 13 Role of Magnesium in Animal, Plant, and Human Nutrition. 13.1 Role of Magnesium in Plant Nutrition. 13.2 Magnesium Fertilizers. 13.3 Magnesium in Animal Nutrition. 13.4 Magnesium in Human Health and Nutrition. 14 Magnesium Salts and Magnesium Metal. 14.1 Magnesium Acetate. 14.2 Magnesium Alkyls. 14.3 Magnesium Chloride. 14.4 Magnesium Nitrate. 14.5 Magnesium Sulfate. 14.6 Magnesium Soaps. 14.7 Magnesium Overbase Sulfonates. 14.8 Magnesium Peroxide. 14.9 Magnesium Metal Production. 15 Pulp Applications. 15.1 Sulfite Pulping. 15.2 Magnefite Pulping Process. 15.3 Pulp Bleaching. 15.4 Deinking. 16 Magnesia Cements. 16.1 Introduction. 16.2 Magnesium Oxychloride Cement. 16.3 Magnesium Oxysulfate (MOS) Cement. 16.4 Thermal Insulative and Fire Resistance Properties of Sorel Cement. 16.5 Magnesium Phosphate Cement. 17 Miscellaneous Magnesia Applications. 17.1 Sugar Manufacture. 17.2 Chrome Tanning of Leather. 17.3 Magnesia as a Catalyst Support. 17.4 Fuel Additives. 17.5 Well-Drilling Fluids. 17.6 Nanoparticulate Magnesia. 17.7 Transformer Steel Coating. Appendix. Index.

Preparation of a magnesium hydroxy carbonate from magnesium hydroxide

The preparation of a magnesium hydroxy carbonate from magnesium hydroxide and carbon dioxide is described. The procedure involves the formation of a magnesium hydroxide slurry and sparging CO 2 gas through it. Various experimental conditions are evaluated in order to obtain the conditions that result in the formation of the magnesium hydroxy carbonate. Slurry pH, slurry temperature, drying temperature, drying time and HCl addition are the conditions that are evaluated. The products that are obtained are identified by XRD and its decomposition characteristics studied with TG/DTA. It is evident from the results obtained that the experimental parameters have a significant influence on the products obtained.

Gas absorption into aqueous reactive slurries of calcium and magnesium hydroxide in a multiphase reactor

Investigation of absorption of SO 2 into aqueous slurries of fine and reactive hydroxide particle of calcium and magnesium was carried out in a stirred vessel at 298 K at realistically high mass transfer coefficients. Enhancement in the rate of gas absorption was measured at different solid loadings and speed of agitation. The absorption process is theoretically analyzed using two different models. For the SO 2–Ca(OH) 2 system, a single reaction plane model was used and for the SO 2–Mg(OH) 2 system, a two reaction plane model incorporating the solids dissolution promoted by the reactions with the absorbed SO 2 in the liquid film was employed. A correct procedure was adopted to estimate the contribution of the suspended particles in the enhancement of gas absorption. Theoretical enhancement factors thus obtained compared well with the experimental data. The extra enhancement observed for the SO 2–Mg(OH) 2 system could be explained from the reaction between SO 2 and the dissolved [SO 3] 2−.

Absorption of sulfur dioxide into aqueous reactive slurries of calcium and magnesium hydroxide in a stirred cell

Chemical absorption of pure SO 2 into aqueous slurries of fine and reactive Ca(OH) 2 and Mg(OH) 2 was studied in a stirred vessel at 298 K at realistically high mass transfer coefficients. The absorption process was theoretically analyzed using two different models. For the SO 2–Ca(OH) 2 system, a single-reaction plane model was used and for the SO 2–Mg(OH) 2 system, a two-reaction plane model incorporating the solids dissolution promoted by the reactions with the absorbed SO 2 in the liquid film was employed. A correct procedure was adopted to estimate the contribution of the suspended particles to the enhancement of gas absorption. Theoretical enhancement factors thus obtained compared well with the experimental data. The extra enhancement observed for the SO 2–Mg(OH) 2 system could be explained from the reaction between SO 2 and the dissolved [SO 3] 2−.

Controlled struvite crystallisation for removing phosphorus from anaerobic digester sidestreams

Enhanced biological phosphorus removal wastewater treatment plants that use anaerobic digesters for sludge treatment, have high phosphorus concentrations in the sidestreams from their sludge dewatering equipment. To remove phosphorus from such sidestreams controlled struvite crystallisation can be used. Struvite (or MAP) is a naturally occurring crystal of magnesium, ammonium and phosphate. We present operational results obtained with a continuously operated pilot-scale MAP reactor. The pilot-scale reactor (143 l) was an air agitated column reactor with a reaction and a settling zone, based on the Phosnix process of Unitika Ltd., Japan. The influent to the MAP reactor was centrate from the centrifuge that dewaters anaerobically digested sludge at the Oxley Creek wastewater treatment plant in Brisbane. We used a 60% magnesium hydroxide slurry to add the required magnesium to the process and to obtain the alkaline pH value required. The pilot-scale MAP process achieved an ortho-P removal ratio of 94% from an average influent ortho-P concentration of 61 mg/l. The reactor was operated at a pH of around 8.5. Insufficient dosing of magnesium reduced the P removal performance. There was no influence of the hydraulic residence time on the process in the range of 1–8 h. The dry MAP product had cadmium, lead and mercury concentrations well below the legal limits for fertilisers in Queensland, Australia and can be reused as a valuable slow-release fertiliser.

Control concrete sewer corrosion via the crown spray process

The crown spray process involves the spray application of a high‐pH mixture to the crown area of the sewer. The aim is to deactivate the sulfur‐ or sulfide‐oxidizing bacteria (SOB) and neutralize the acid at the sewer crown; to render the sewer crown environment unfavorable for regrowth and recolonization of SOB; to leave a residual alkalinity on the sewer crown to neutralize the acid produced as the SOB recolonize the sewer, and, consequently, control the crown corrosion process. A number of different chemicals, both hazardous and nonhazardous, were investigated for use with the process. The use of biocides as additives to enhance the deactivation potentials of the various treatment mixtures was also evaluated. To gauge the effectiveness of the treatment, surface pH of the sewer crown is measured before and after treatment. Immediately after spraying the surface, pH of the crown generally increases from less than 2 to greater than 9 and then gradually decreases with time to background levels. The mechanism of deactivation and regrowth of the organisms is discussed. Magnesium hydroxide slurry, a nonhazardous chemical, is the most effective treatment chemical tested to date. Application of a 50% slurry to the crown of a highly corroded active sewer has maintained the surface pH at or greater than 9 for approximately 9 months. Microbiological assays indicate a reduction in population of SOB from 107 to 102 cells/g of corrosion product (below detectable levels). Approximately 9 months after treatment, the number of SOB are still 1 to 2 orders of magnitude below the background population level. The operational aspects, economics, and the mechanism of the crown spray process are discussed. The data indicate the crown spray process is the most economical corrosion control technology of eight other methods previously evaluated by the districts.