Magnesium Sulfite Research Articles

Enhanced oxidation of MgSO3 during desulfurization by a novel spray method in magnesium-based seawater exhaust gas clean system

The magnesium-based seawater exhaust gas clean system is effective in reducing sulfur dioxide emission from marine diesel engines. Oxidation of the desulfurization by-product, magnesium sulfite (MgSO3), is required for recycling. However, the oxidation efficiency is generally low in the aeration tank after the desulfurization process, making the tank volume too large for practical use on ocean vessels. In this article, we propose a novel spray oxidation method to enhance the oxidation of MgSO3 during the desulfurization process. The effects of MgSO3 content, pH and temperature on the oxidation rate were investigated. The results showed that the spray oxidation rate of MgSO3 was 1.5 order with respect to the MgSO3 concentration under both unsaturated and saturated conditions of MgSO3 solution, which is different from the aeration oxidation researches. The spray oxidation rate decreased with the increase in pH and raised slowly as the temperature increased. The MgSO3 oxidation mechanism of the spray oxidation method was analyzed and discussed in comparison with the traditional bubble aeration method. The novel spray oxidation method is effective in reducing the cost of the subsequent MgSO3 aeration oxidation process and the offprint of aeration tanks, thus is promising to be applied on ocean vessels.

Optimization of micro-bubble aeration process for magnesium sulfite oxidation in desulphurization wastewater with response surface methodology

Optimization of micro-bubble aeration process for magnesium sulfite oxidation in desulphurization wastewater with response surface methodology

A green and robust solid catalyst facilitating the magnesium sulfite oxidation in the magnesia desulfurization process

Effect of cobalt loading on the dispersity and catalysis performance.

Mechanism and kinetics of magnesium sulfite oxidation catalyzed by multiwalled carbon nanotube

Oxidation of magnesium sulfite is crucial for recycling the byproduct in magnesia desulfurization. Using impregnation method, a multiwalled carbon nanotube catalyst loaded with cobalt was prepared to promote the oxidation rate of magnesium sulfite (MgSO3). The performance of catalysts impregnated by different concentration of Co(NO3)2 were compared, which showed that the optimal impregnating concentration was 30%. The catalysts prepared with various concentration of Co(NO3)2 were characterized by Brunauer–Emmett–Teller analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyzed oxidation kinetics of magnesium sulfite was investigated in a bubbling tank, indicating that the general reaction orders with respect to carbon nanotube, oxygen, and magnesium sulfite were 0.22, 0.45, and 0.01, respectively. The apparent activation energy was 23.43kJmol−1. The three-phases reaction model revealed that the internal diffusion of oxygen might be the rate-controlling step of magnesium sulphite oxidation. The results can serve as a useful reference for designing sulfite oxidation by using multiwalled carbon nanotube catalyst.

Kinetics and mechanism of magnesium sulphite oxidation promoted by a novel cobalt-based molecular sieve catalyst

The oxidation of magnesium sulphite is crucial in recycling the byproduct of magnesium desulphurisation. In this study, a novel cobalt-based catalyst was prepared using a wet impregnation method by loading cobalt species on a molecular sieve carrier. The catalyst was characterised using scanning electron microscopy, X-ray fluorescence, Brunauer–Emmett–Teller analysis, X-ray diffraction, and energy dispersive X-ray spectroscopy. The catalyst was confirmed to be a mesoporous material. The macroscopic kinetics of magnesium sulphite oxidation catalysed by this cobalt-based catalyst was investigated in a stirred tank reactor. The results showed that reaction orders with respect to catalyst, magnesium sulphite, and oxygen concentrations were 0.39, 0, and 0.41, respectively. The apparent activation energy was 35.2kJmol−1. In addition, a comparison of the rates of external diffusion, internal diffusion, and intrinsic reaction revealed that the internal diffusion of oxygen might be the rate-controlling step of magnesium sulphite oxidation. The results provide a new approach for recycling the magnesium desulphurisation byproduct.

Selectivity of transition metal catalysts in promoting the oxidation of solid sulfites in flue gas desulfurization

Wet flue gas desulfurization (WFGD) has been widely used to reduce the harmful effects of sulfur dioxide during coal combustion, of which sulfite is a byproduct. Recycling this desulfurization byproduct requires the oxidation of sulfite, and transition metals might considerably promote the sulfite oxidation rate. We compared the oxidation rates of four sulfites—sodium sulfite, ammonium sulfite, magnesium sulfite, and calcium sulfite—and found that transition metals have selective catalytic performance. Although each transition metal was confined to specific sulfites, Co2+ and Mn2+ were the most effective catalysts. In addition, the sensitivity levels of the sulfite oxidation rates to various transition metals were classified. The orders of the reactions of the four sulfites catalyzed by Co2+ and Mn2+ were calculated. Although both magnesium sulfite and calcium sulfite exist as solids, the oxidation rate of magnesium sulfite was considerably sensitive to Co2+. The same results were observed for sodium sulfite and ammonium sulfite. However, the oxidation rate of calcium sulfite was sensitive only to Mn2+. The properties of the two prepared solid samples, magnesium sulfite and calcium sulfite, were compared using X-ray diffraction, scanning electron microscopy, and particle size analysis. The position-occupying hypothesis was applied to determine the selective catalytic behaviors of transition metals for the oxidation of various sulfites by comparing the ionic potentials of the metals. The results provide an effective theoretical basis for catalyzing the sulfite oxidation in WFGD.

Experimental investigation of MgSO3 oxidation process by catalysis in the magnesium desulfurization

Catalytic oxidation of magnesium sulfite (MgSO3) into magnesium sulfate (MgSO4) is essential for recycling and utilization in the magnesium desulfurization processes. In this paper, laboratory-scale experiments were carried out to compare catalytic activity of different catalysts, which showed that cobalt ions (Co2+) were highly efficient for MgSO3 oxidation catalysis. Moreover, Pilot-scale tests were conducted to validate the major reaction conditions influencing catalytic performance of Co2+, such as air flow rate, pH, temperature, and Co2+ concentrations. Possible reaction mechanism and reaction kinetics of MgSO3 oxidation catalysis was discussed and interpreted, respectively. The MgSO3 oxidation by catalysis has much potential application in the industrial field of the magnesium desulfurization.

English

Piriformospora indica (Hymenomycetes, Basidiomycota) is a cultivable endophyte that colonizes roots and has been extensively studied. P. indica has multifunctional activities like plant growth promoter, biofertilizer, immune-modulator, bioherbicide, phytoremediator, etc. Growth promotional characteristics of P. indica have been studied in enormous number of plants and majority of them have shown highly significant outcomes. Certain secondary metabolites from the fungus are reasons behind such promising outputs. Effect of P. indica has been studied on more than 150 plants. Promising outputs of laboraatory experiments and small field trials indicated the need for its mass cultivation and usage. For field trials, a formulation “Rootonic” was prepared by mixing P. indica biomass in magnesium sulphite. The quantity of formulation (Rootonic) to be used per acre of land for maximum productivity has also been standardized for about 50 plants. P. indica has proved to be highly beneficial endophyte with high efficacy in field. This article is a review on our journey from P. indica to “Rootonic”. Key words: Piriformospora indica, Rootonic, Mycorrhizae, endophyte, biofertilizer.

The Treatment and Recycling of FGD Waste

At present, wet lime - gypsum flue gas desulfurization (FGD) technology is very common in the field of gas desulfurization technology. In addition, wet carbide slag - gypsum FGD and Magnesia FGD are also used. In the process of eliminating SO2, with the first two technology, the byproducts of desulfurization wastewater and gypsum will be produced; With Magnesia FGD, the byproducts of magnesium sulfite and magnesium will be produced. The way to utilize desulfurization wastewater, gypsum and magnesium comprehensively and to achieve circular economy is worth exploring.

Oxidation Rate of Magnesium Sulfite Catalyzed by Cobalt Ions

Oxidation of magnesium sulfite is important for recycle of byproduct in the magnesium desulfurization. The oxidation rate of magnesium sulfite, prepared by vacuum evaporation method, was investigated in a bubbling tank in presence of transition metal catalysts, which shows cobalt is the most effective. The general reaction orders with respect to cobalt, magnesium sulfite, and oxygen are 0.44, 0, and 0.46, respectively, and the apparent activity energy is 17.43 KJ·mol. The catalytic performance of cobalt compared with other metals was also analyzed employing the ion potential theory. Integrated with the three-phase reaction model, we inferred that the general oxidation rate of magnesium sulfite is controlled by mass transfer of oxygen. Further, the intrinsic kinetics was predicted, indicating that the reaction orders with respect to cobalt and oxygen are 1.0 and 0, respectively. The results are helpful for the recycle of magnesium sulfite in magnesia desulfurization.

Alkali Precipitation Properties of Magnesium Lignosulfonate Isolated from Acid Sulfite Pulping Waste Liquor

To establish a simple method to separate and purify the magnesium lignosulfonate from the red liquor, the properties of the alkali precipitation of magnesium lignosulfonate in the red liquor were investigated. The results show that the magnesium lignosulfonate could be precipitated by alkali from red liquor. The maximum amount of precipitation occurs when pH value was 13. The precipitation of the red liquor of acid magnesium sulfite is caused by magnesium. It was different from sodium lignosulfonate of the red liquor of acid sodium sulfite. The repeated alkaline precipitation after acid soluble method could be isolated and purified lignosulfonate magnesium effectively at some extent.

Research on sulfur recovery from the byproducts of magnesia wet flue gas desulfurization

To recycle sulfur from byproducts of magnesia wet flue gas desulfurization, the authors conducted an experimental study and computational analysis on the factors influencing the SO2 mole fraction in the calciner gas by an industrial demonstration unit. With a sulfur content of 1.65% in coal and a generating capacity of 300 MW of power plant, the economics of the renewable magnesium oxide desulfurization technology was compared to that of limestone–gypsum desulfurization technology. The results show that the decomposition reaction of byproducts mainly occurred in the lower zone of the furnace. When the excess air coefficient was 1.05 and the magnesium sulfite content in the byproducts was 60%, the SO2 mole fraction in the calciner gas was 10.5%. Decreasing the excess air coefficient can improve the SO2 mole fraction in the calciner gas. When the moisture content in the byproducts was 15%, the SO2 mole fraction reached 9.2%. The calciner exit gas temperature should be controlled at 1253.5 K or below. Adopting oxygen-enriched combustion, the oxygen content in air should be controlled to 31%. The magnesium oxide desulfurization renewable technology was found to be more economic.

Study on washwater effluent quality discharged by ship exhaust gas DeSO<SUB align="right">x system with magnesium and seawater desulphurisation method

The latest convention of ship pollution prevention was carried out by the International Maritime Organization (IMO), which requires that sulphur dioxide emissions from ships around the world must be further reduced. A novel wet scrubber system with MgO and seawater (M&S) as desulphuriser was proposed to deal with the new convention. The quality of the washwater effluent discharged by M&S DeSO x system has not been studied systematically yet. This paper used a variety of methods to analyse the effluent, including chemical method, spectrophotometry and X-ray diffractometer. The effluent was detected to contain a large amount of chloride, sulphate and nitrate ions, and the mass fraction of chloride ion was as high as 3.2%. The main components of suspended solids were magnesium hydroxide, magnesium sulphite, and silicon dioxide. In the effluent, COD, SS, total oil content and turbidity were above the limitation set by the washwater discharge criteria. Based on the analysis of the effluent quality, the sulphite, nitrite, PAHs and total oil content were regarded as the main factors affecting COD.

A cause of water-sensitivity in modern oil paint films: The formation of magnesium sulphate

Unvarnished twentieth-century oil paintings are often sensitive to aqueous swabbing, a method routinely employed by conservators for surface cleaning. This study proposes a connection between sensitivity and the presence of magnesium sulphate heptahydrate which has been identified on the surface of some of water-sensitive paintings. The probable source of magnesium is magnesium carbonate, an additive in some twentieth-century oil paints, which has reacted with atmospheric sulphur dioxide (SO2). Films made using modern manufactured paints and formulations made in the laboratory were exposed to gaseous SO2 and raised relative humidity and examined using scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction to characterize the crystalline entities. Films containing magnesium carbonate formed magnesium sulphite and sulphate hydrates. Films containing zinc oxide were also investigated. These formed zinc and sulphur containing salts. Sensitivity to swabbing with water before and after exposure was evaluated. Films that developed salts, demonstrated increased sensitivity to aqueous swabbing after exposure to SO2. Findings suggest that increased water sensitivity may be due to a combination of the formation of hygroscopic degradation products and to weakening of the paint film due to salt-induced disruption of the surface.

The Kinetics of Oxidation Inhibition of Magnesium Sulfite in the Wet Flue Gas Desulphurization Process

Using a stirred bubbling reactor, the kinetics of oxidation inhibition of MgSO3 from a magnesium-based wet flue gas desulphurization process were investigated. The reaction was found to be 0.7 order with respect to magnesium sulfite and −0.3 order with respect to sodium thiosulfate. The pH value should be controlled at a lower level in order to hamper the oxidation of sulfite. The apparent activation energy of the reaction was calculated to be 8.68 kJ/mol and a kinetic model has been established. Pilot tests showed that sodium thiosulfate can effectively inhibit the oxidation of magnesium sulfite in the magnesium-based wet flue gas desulphurization process.

Properties of Stratified Alkaline Precipitate Isolated from Red Liquor of Acidic Magnesium Sulfite Pulping

Alkaline precipitate isolated from red liquor of acidic magnesium sulfite pulping exhibited obvious stratification. The properties of the stratified alkaline precipitate were investigated via infrared spectroscopy, ion chromatography, thermogravimetric analysis, and high efficiency liquid chromatography. The sulfonic group of lignosulfonate showed a characteristic absorption peak from 1210 cm-1 to 1170 cm-1. There were no significant differences between the structures of the functional groups of the upper and lower layers of the precipitate. The peak time of the sulfonic group was 6.350 min, as measured by ion chromatography. Compared with the upper precipitate, the lower precipitate had more groups with high carbon and low oxygen contents and did not easily decompose. The relative molecular weight of the lower precipitate was greater than that of the upper precipitate. The difference in relative molecular weight of the precipitates gave rise to the observed stratification.

Oxidation Kinetics of Magnesium Sulfite in Presence of Synthesized Solid Catalyst

In the present paper, a bubbling reactor is employed to investigate the macroscopical kinetics of magnesium sulfite oxidation in presence of the solid catalysts. A synthesized solid metal catalyst M was selected by performance comparison, which had significant catalytic effect on the oxidation rate of magnesium sulfite. The experimental results indicated that the reaction orders are 0 and 0.61 with respect to magnesium sulfite concentration and oxygen partial pressure. Moreover the apparent activation energy of the reaction is 10.66 KJ/mol. Thus a useful reference is provided for recycle of byproduct by catalyzed oxidation in magnesia desulphurization.

Macrokinetics of magnesium sulfite oxidation inhibited by ascorbic acid

Magnesia flue gas desulfurization is a promising process for small to medium scale industrial coal-fired boilers in order to reduce sulfur dioxide emissions, in which oxidation control of magnesium sulfite is of great importance for the recycling of products. Effects of four inhibitors were compared by kinetic experiments indicating that ascorbic acid is the best additive, which retards the oxidation process of magnesium sulfite in trace presence. The macrokinetics of magnesium sulfite oxidation inhibited by ascorbic acid were studied. Effects of the factors, including ascorbic acid concentration, magnesium sulfite concentration, oxygen partial pressure, pH, and temperature, were investigated in a stirred reactor with bubbling. The results show that the reaction rate is −0.55 order in ascorbic acid, 0.77 in oxygen partial pressure, and zero in magnesium sulfite concentration, respectively. The apparent activation energy is 88.0kJmol−1. Integrated with the kinetic model, it is concluded that the oxidation rate of magnesium sulfite inhibited by ascorbic acid is controlled by the intrinsic chemical reaction. The result provides a useful reference for sulfite recovery in magnesia desulfurization.

3d electron transitions in Co- and Ni-doped MgSO3·6H2O

Absorption spectra of magnesium sulfite hexahydrate (MgSO3·6H2O), doped with Co and Ni, have been studied in the spectral region 1.46–3.1 eV. Investigations have been carried out with linear polarized light E‖c, E⊥c (c is the optical axis of MgSO3·6H2O) that propagates in the (1210) direction. The Co structure manifests in the spectral region 2.06–3.1 eV and the Ni structures manifest in the spectral region 1.46–2.26 eV. The peculiarities of the Jahn–Teller effect and spin–orbit interaction with respect to the impurity ions in the crystal lattice of MgSO3·6H2O are analyzed and discussed. The electron transitions in Co2+ and Ni2+ ions are determined for E‖c, E⊥c. The crystal field parameter Dq and Racah parameters B and C are also calculated.

Kinetics and Mechanism of Sulfite Oxidation in the Magnesium-Based Wet Flue Gas Desulfurization Process

The kinetics of sulfite oxidation in the magnesium-based wet flue gas desulfurization (FGD) process were investigated in a stirred bubbling reactor by varying the concentrations of MgSO3 and MgSO4, pH, air flow and temperature. The reaction was found to be 0.88 order with respect to magnesium sulfite and the oxidation could reach the maximum rate when the pH value was close to 6.5. The mechanism of the oxidation was discussed, and it was concluded that the oxidation is controlled by diffusion of oxygen. These results would be useful for the design or process optimization of the magnesium-based wet FGD system.