Addition Of Na2CO3 Research Articles

Dephosphorization in the Reduction and Melting Separation of High Phosphorus Hematite Carbon Bearing Pellets

The rotary hearth furnace iron nugget process is a new technology with a huge potential to efficiently utilize high phosphorus hematite. In this paper, the influences of the basicity and additives on the phosphorus content and distribution in the iron nuggets and the slag were investigated. At first CaCO3 was added to the pellets and then Na2CO3 and CaF2 were also added in the experiments. The experimental results showed that the increase in the basicity and the addition of Na2CO3 and CaF2 were shown to be effective to inhibit the apatite reduction in high phosphorus iron ores and to reduce the phosphorus content in the nuggets. When the pellets containing 4% Na2CO3 and 4% CaF2 with the basicity at 1.4 were reduced at the temperature of 1400°C for 12 min, the phosphorus content in the iron nuggets was only 0.4% and the dephosphorization rate reached 81.2%.

Activation of sodium percarbonate with ferrous ions for degradation of chlorobenzene in aqueous solution: mechanism, pathway and comparison with hydrogen peroxide

Environmental contextIt is practicable to remediate chlorobenzene-contaminated groundwater by in situ chemical oxidation. This study shows highly efficient degradation of chlorobenzene by an Fe-based process in a wide range of pH values. The technology is feasible for the removal of chlorobenzene from aqueous solutions and is appropriate for remediation of groundwater. AbstractSodium percarbonate (SPC) could be applied as a strong oxidant to degrade organic compounds activated by transition metals. In this study, the degradation performance of chlorobenzene (CB) in the Fe2+-catalysed SPC system was investigated at different Fe2+ and SPC concentrations and pH conditions. Fe2+/Fe3+ conversion was also studied, and the SPC system was compared with the H2O2 and H2O2/Na2CO3 systems. Free radicals were identified through scavenging tests and electron paramagnetic resonance (EPR) experiments, and the reaction intermediates and by-products were determined as well. The results show that CB was completely removed when the molar concentration ratio of Fe2+/SPC/CB was 8 : 8 : 1 and that the decomposition of CB increased as the initial Fe2+/SPC dosage increased. The optimal molar concentration of Fe2+/SPC/CB was 2 : 1 : 1, and the degradation rate was inhibited when increasing or decreasing Fe2+ or SPC. CB degradation was not significantly affected by variation of initial pH, and the variation of pH during the degradation process corresponded well with the degree of Fe2+ to Fe3+ conversion and the formation of •OH. It was confirmed that •OH, O2•− and 1O2 participate in the degradation process. Moreover, not all the •OH takes part in the degradation process, as some transforms into O2•− and 1O2. The same degradation efficiency was obtained when replacing SPC by equal stoichiometric amounts of H2O2, compared with inhibition with the addition of Na2CO3. Further, a likely degradation pathway for CB is proposed based on the identified products. These results show that the Fe2+/SPC system can form the basis of a promising technology for the remediation of CB-contaminated groundwater.

Preparation of xerogel SiO2 from roasted iron sand under various acidic solution

Xerogel SiO2 had been prepared from roasted iron sand through variation of Na2CO3 addition and sol-gel process under various acidic solution. Roasting treatment was carried out on the compositional variation of iron sand:Na2CO3 = 1:2; 1:1 and 2:1 at 1100 °C. While the sol-gel process was conducted at room temperature and neutralized using HCl 0.1 M and 6 M. The color characteristics of roasted iron sand shown light brown, dark brown and dark gray of the compositional variation of iron sand:Na2CO3 = 1:2; 1:1 and 2:1, respectively. In addition, the levels of thoughness increased by increasing the ratio of sand in the composition of the mixture. The best composition of roasted treatment was at a variety of iron sand:Na2SiO3 = 1:2 with 57.72% had been dissolved in hot water. The addition of Na2CO3 will influence the Na2SiO3 formation, because of the increase of Na2CO3 capable produced the iron sand decomposition product. Na2SiO3 gel had been produced after it was neutralized with certain amount of HCl solution. The neutralization was more effective if using high concentration of HCl because of the formation of gel SiO2 will be easier occurred. The results of SiO2 had been identified by the FTIR spectra, which an absorption spectra of Si-O-Si asymmetric stretching at 1098.51 cm-1, symmetric stretching of Si-O-Si at 804.35 cm-1 and the bending O-Si-O at 469.69 cm'1. The result of SiO2 content by XRF analysis is about 85.15%.

Thermodynamic analysis of the carbothermic reduction of a high-phosphorus oolitic iron ore by FactSage

A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore (HPOIO) was conducted by the FactSage thermochemical software. The effects of temperature, C/O ratio, additive types, and dosages both on the reduction of fluorapatite and the formation of liquid slag were studied. The results show that the minimum thermodynamic reduction temperature of fluorapatite by carbon decreases to about 850°C, which is mainly ascribed to the presence of SiO2, Al2O3, and Fe. The reduction rate of fluorapatite increases and the amount of liquid slag decreases with the rise of C/O ratio. The reduction of fluorapatite is hindered by the addition of CaO and Na2CO3, thereby allowing the selective reduction of iron oxides upon controlled C/O ratio. The thermodynamic results obtain in the present work are in good agreement with the experimental results available in the literatures.

Microstructure Characteristic and Phase Evolution of Refractory Siderite Ore during Sodium-carbonate-added Catalyzing Carbothermic Reduction

Thermodynamic analysis of refractory siderite ore during carbothermic reduction was conducted. Microstructure characteristics and phase transformation of siderite ore during sodium-carbonate-added catalyzing carbothermic reduction were investigated. X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive analysis of X-rays were used to characterize the reduced samples. Results indicate that the solid reaction between FeO and SiO2 is inevitable during carbothermic reduction and the formation of fayalite is the main hindrance to the rapid reduction of siderite. The phase transformation of present siderite ore can be described as: siderite-magnetite-metallic iron, complying with the formation of abundant fayalite. Improving the reduction temperature (≤ 1050 °C) and duration is helpful for the formation and aggregation of metallic iron. The iron particle size in the reduced ore was below 20 μm, and fayalite was abundant in the absence of sodium carbonate. With 5% Na2CO3 addition, the iron particle size in the reduced ore was generally above 50 μm, and the diffraction intensity associated with metallic iron in the XRD pattern increased. The Na2O formed from the dissociation of Na2CO3 can catalyze the carbothermic reduction of the siderite. This catalytic activity may be mainly caused by an increase in the reducing reaction activity of FeO.

Equilibrium and kinetics studies of adsorption phosphate on raw and novel lithium silica fume based adsorbent

In this study, the adsorption of phosphate from aqueous solution by lithium silica fume (LSF) with or without iron oxides modification was investigated. Iron oxides modification was achieved by in situ generation of iron oxides on LSF by applying three different kinds of ferric solution (FeCl3·6H2O, Fe(NO3)3·9H2O, and Fe2(SO4)3) with Na2CO3 addition. Batch adsorption studies were carried out for better understanding of their adsorption behaviors towards phosphate. Among three iron oxide modified adsorbents, FeCl3-modified LSF (FeCl3/LSF) exhibited highest SBET, and best adsorptive capability towards phosphate. The adsorption kinetics data of phosphate adsorption onto FeCl3/LSF fitted well with Langmuir model and Freundlich model. The maximum phosphate adsorption capacity onto FeCl3/LSF is 13.39 mg g−1 at 25°C, almost three times higher than that of LSF. The X-ray diffraction pattern showed new species of Fe(PO3)3 that was formed on FeCl3/LSF after adsorbing onto phosphate, which indicated chemisorption was involved in phosphate adsorption; this phenomenon is in accordance with SEM-EDS, FTIR, and X-ray photoelectron spectroscopy analysis. The coexistence of Cl−, NO3-, SO42- slightly affected phosphate removal, while coexistence of CO32- greatly reduced the adsorption of phosphate. The relatively low cost and high capabilities of FeCl3/LSF make it a potentially attractive adsorbent for removing phosphate from aqueous solution.

Fe-Mn bi-metallic oxides loaded on granular activated carbon to enhance dye removal by catalytic ozonation.

A Fe-Mn bi-metallic oxide supported on granular activated carbon (Fe-Mn GAC) has been fabricated by an impregnation-desiccation method and tested in the catalytic ozonation of methyl orange (MO) degradation and mineralization. X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy characterizations revealed that Fe-Mn oxides were successfully loaded and uniformly distributed on the GAC, and nitrogen adsorption isotherms showed that the supported GAC retained a large surface area and a high pore volume compared with the pristine GAC. The catalytic activity was systematically assessed by monitoring the MO removal efficiencies at different operational parameters, such as catalyst dosage, initial solution pH, and ozone flow rate. The Fe-Mn GAC exhibited better catalytic activity relative to ozone alone and GAC alone, improving the TOC removal by 24.5 and 11.5% and COD removal by 13.6 and 7.3%, respectively. The reusability of the hybrid was examined over five consecutive cyclic treatments. The Fe-Mn GAC catalytic activity was only a slight loss in the cycles, showing good stability. The addition of Na2CO3 as hydroxyl radicals (•OH) scavengers proved that the catalytic ozonation mechanism was the enhanced generation of •OH by the Fe-Mn GAC. The above results render the Fe-Mn GAC an industrially promising candidate for catalytic ozonation of dye contaminant removal.

Catalytic effects of alkali carbonates on coal char gasification

In this work, effects of K2CO3 and Na2CO3 additives on catalytic gasification of Shenfu coal were studied by the combination of thermogravimetric analyzer (TGA) and an in-situ heating stage microscope. Effects of loading amounts of catalysts (2.2 wt.%, 4.4 wt.%, and 6.6 wt.%) and gasification temperatures (700–950 °C) on the interactions during the char–ash/slag transition were analyzed. The results show that the interactions of catalysts with coal at gasification phase varied with reaction temperature, and compared to K-form char, Na-form char showed a more significant melt and flow of catalysts when the temperature was higher than the melting point of catalyst. The different aggregation states of catalysts on the surface of char matrix and development degrees of pore structure of char matrix accounted for the differences in interaction forms of K catalyst and Na catalyst with coal char. The interaction mechanisms of catalysts with char matrix during char–ash/slag transition were proposed and were related to the variation of gasification reactivity of char with increasing reaction temperature. Moreover, the ratio of the initial reaction rate of char loading catalyst to that of raw coal char (the specific reactivity) and the optimal loading amount of catalysts were analyzed considering the optimal gasification efficiency. There is a threshold value of reaction temperature lower than the melting point of catalyst for the optimal gasification efficiency during the gasification processes of Na-form and K-form chars.

Simultaneous dispersive liquid-liquid microextraction based on a low-density solvent and derivatization followed by gas chromatography for the simultaneous determination of chloroanisoles and the precursor 2,4,6-trichlorophenol in water samples.

Chloroanisoles, particularly 2,4,6-trichloroanisole, are commonly identified as major taste and odor compounds in water. In the present study, a simple and efficient method was established for the simultaneous determination of chloroanisoles and the precursor 2,4,6-trichlorophenol in water by using low-density-solvent-based simultaneous dispersive liquid-liquid microextraction and derivatization followed by gas chromatography with electron capture detection. 2,4-Dichloroanisole, 2,6-dichloroanisole, 2,4,6-trichloroanisole, 2,3,4-trichloroanisole, and 2,3,6-trichloroanisole were the chloroanisoles evaluated. Several important parameters of the extraction-derivatization procedures, including the types and volumes of extraction solvent and disperser solvent, concentrations of derivatization agent and base, salt addition, extraction-derivatization time, and temperature were optimized. Under the optimized conditions (80 μL of isooctane as extraction solvent, 500μL of methanol as disperser solvent, 60 μL of acetic anhydride as derivatization agent, 0.75% of Na2 CO3 addition w/v, extraction-derivatization temperature of 25°C, without salt addition), a good linearity of the calibration curve was observed by the square of correlation coefficients (R(2) ) ranging from 0.9936 to 0.9992. Repeatability and reproducibility of the method were < 4.5% and <7.3%, respectively. Recovery rates ranged from 85.2 to 101.4%, and limits of detection ranged from 3.0 to 8.7 ng/L. The proposed method was applied successfully for the determination of chloroanisoles and 2,4,6-trichlorophenol in water samples.

Effect of oxygen and additives on thermal decomposition of aqueous urea solution

The thermal decomposition of aqueous urea solution was studied in a lab-scale experimental system. The experimental research was focused on the effect of oxygen concentration and different additives on NH3 yields, N2O production, and CO concentration. Without oxygen or additives, the NH3 yields increased gradually as the temperature increased from 473K to 923K and remained approximately 60% in the temperature range of 923–1073K. Oxygen promoted the thermal decomposition process and enhanced the NH3 yields in the temperature range of 473–773K, but it brought about the oxidation of NH3 and led to significant decline of the NH3 yields when the reaction temperature was above 823K. The addition of Na2CO3 promoted the NH3 yields obviously, but it did not restrain the NH3 oxidation at high temperatures. Furthermore, Na2CO3 reduced the production of N2O and CO at 623–1073K. Similar to Na2CO3, the addition of NaNO3 also increased the NH3 yields and decreased the N2O and CO concentration.

Switching the Cleavage Sites in Palladium on Carbon-Catalyzed Carbon-Carbon Bond Disconnection.

We have demonstrated a palladium on carbon-catalyzed approach to regioselectively alter the cleavage sites of the C-C bonds of cinnamaldehyde derivatives by a slight change in the reaction conditions in isopropanol under an O2 atmosphere. Styrene derivatives could be selectively formed by the addition of Na2CO3 in association with the dissociation of carbon monoxide, while benzaldehyde derivatives were generated by the addition of CuCl and morpholine instead of Na2CO3.

Influence of Na2CO3 as Additive on Direct Reduction of Boron-bearing Magnetite Concentrate

Boron-bearing magnetite concentrate is typically characterized by low grade of iron and boron (wTFc = 51 %— 54 %, wB2O3 = 6 % — 8%), as well as the close intergrowth of ascharite phase and magnetite phase. A promising technology was proposed to separate iron and boron by coupling the direct reduction of iron oxides and Na activation of boron minerals together. The influence of Na2CO3 as additive on the direct reduction of boron-bearing magnetite was studied by chemical analysis, kinetic analysis, XRD analysis and SEM analysis. The results showed that the addition of Na2CO3 not only activated boron minerals, but also reduced the activation energy of the reaction and promoted the reduction of iron oxides. Besides, the addition of Na2CO3 changed the composition and melting point of non-ferrous phase, and then promoted the growth and aggregation of iron grains, which was conducive to the subsequent magnetic separation. Thus, the coupling of the two processes is advantageous.

Stability of green tea nanoscale zero-valent iron

Colloidal suspension of nano zero-valent iron (nZVI), obtained as a result of mixing green tea (GT) solution with iron solutions (FeCl2 and FeSO4 separately to form two suspensions: GT-nZVIFeCl2 and GT-nZVIFeSO4 ) was assessed in terms of stability. The particles of suspensions had a tendency rapidly aggregation to form larger aggregates, and then settled. The absolute value of zeta potential (ζ) of suspensions did not exceed 17 mV. To prevent the aggregation of nZVI particles, the pHs were changed by the addition of Na2 CO3 to obtain higher values of ζ. For both suspensions, the zeta potential at a satisfactory level was obtained at pH values higher than 7.5. Then, the potential was lower than −40 mV for GT-nZVIFeCl2 and lower than −25mV for GT-nZVIFeSO4 . This means that the first suspension had a better stability than second. The isoelectric point (IEP) of GT-nZVIFeCl2 was in the range from 4.5 to 5, while in the case of GT-nZVIFeSO4 all measured ζ were negative. To investigate the effect of increased ionic strength (IS) on the stability of suspensions at different pH values, NaCl and MgSO4 were added to the irons solutions. The final IS in the GT-nZVI was 12 mM. In both of the suspensions the absolute values of ζ were lower than previous and were about 25 and 20 mV, for GT-nZVIFeCl2 and GT-nZVIFeSO4 , respectively.

The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor

Abstract The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (Mw) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to Mw decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].

Oleaginous yeast platform for producing biofuels via co-solvent hydrothermal liquefaction.

BackgroundOleaginous microorganisms are attractive feedstock for production of liquid biofuels. Direct hydrothermal liquefaction (HTL) is an efficient route that converts whole, wet biomass into an energy-dense liquid fuel precursor, called ‘biocrude’. HTL represents a promising alternative to conventional lipid extraction methods as it does not require a dry feedstock or additional steps for lipid extraction. However, high operating pressure in HTL can pose challenges in reactor sizing and overall operating costs. Through the use of co-solvents the HTL operating pressure can be reduced. The present study investigates low-temperature co-solvent HTL of oleaginous yeast, Cryptococcus curvatus, using laboratory batch reactors.ResultsIn this study, we report the co-solvent HTL of microbial yeast biomass in an isopropanol–water binary system in the presence or absence of Na2CO3 catalyst. This novel approach proved to be effective and resulted in significantly higher yield of biocrude (56.4 ± 0.1 %) than that of HTL performed without a co-solvent (49.1 ± 0.4 %)(p = 0.001). Addition of Na2CO3 as a catalyst marginally improved the biocrude yield. The energy content of the resulting biocrude (~37 MJ kg−1) was only slightly lower than that of petroleum crude (42 MJ kg−1). The HTL process was successful in removing carboxyl groups from fatty acids and creating their associated straight-chain alkanes (C17–C21). Experimental results were leveraged to inform techno-economic analysis (TEA) of the baseline HTL conversion pathway to evaluate the commercial feasibility of this process. TEA results showed a renewable diesel fuel price of $5.09 per gallon, with the HTL-processing step accounting for approximately 23 % of the total cost for the baseline pathway.ConclusionsThis study shows the feasibility of co-solvent HTL of oleaginous yeast biomass in producing an energy-dense biocrude, and hence provides a platform for adding value to the current dairy industry. Co-solvents can be used to lower the HTL temperature and hence the operating pressure. This process results in a higher biocrude yield at a lower HTL temperature. A conceptual yeast HTL biofuel platform suggests the use of a dairy waste stream for increasing the productivity and sustainability of rural areas while providing a new feedstock (yeast) for generating biofuels.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0345-5) contains supplementary material, which is available to authorized users.

The impact of modifications of the smectite-bearing raw materials on their thermal expansion ability

The effects of modifications of the clay rocks containing smectite on their thermal expansion have been studied at the example of the claystones from Dylągowka (Dynow Foothills, south-eastern Poland). Hot-stage microscopy was employed combining a dedicated procedure of digital image analysis. The chemical modification of three rock types from the Dylągowka deposit included the treating with an addition of Na2CO3, activation with a H2SO4 solution, and firing at 560 °C. X-ray diffraction and thermal analyses (DTA, TG) helped determine the impact of the modification processes on the structural changes in smectite, the major component of the rocks in question. The investigations into thermal expansion have shown that the clay rock varieties poor in CaO can be acid-activated with a significant improvement their expansion in comparison with such an ability of natural rock equivalents. It is a result of introducing silica into the melt that forms on heating the natural clay rock at high temperatures due to its presence of alkalis (Na2O and K2O). The silica, in turn, comes from the protonated silica gel generated due to the acid treatment of smectite-bearing rocks. The liquid phase (the melt) with a high viscosity may form a cover on the surface of granules of the product being fired and prevents the expulsion of gases into the ambience. An addition of Na2CO3 is favourable as it considerably lowers the firing temperature of the expanded product, both in the case of clay raw materials poor and rich in CaO. The acid activation of the latter variety (CaO-rich) is less effective because of the reaction of acid (H2SO4 used by the authors) with calcite; the mineral is decomposed, and at least part of the acid does not activate a clay material.

The influence of lignin on steam pretreatment and mechanical pulping of poplar to achieve high sugar recovery and ease of enzymatic hydrolysis

With the goal of enhancing overall carbohydrate recovery and reducing enzyme loading refiner mechanical pulping and steam pretreatment (210°C, 5min) were used to pretreat poplar wood chips. Neutral sulphonation post-treatment indicated that, although the lignin present in the steam pretreated substrate was less reactive, the cellulose-rich, water insoluble component was more accessible to cellulases and Simons stain. This was likely due to lignin relocation as the relative surface lignin measured by X-ray photoelectron spectroscopy increased from 0.4 to 0.8. The integration of sulphite directly into steam pretreatment resulted in the solubilisation of 60% of the lignin while more than 80% of the carbohydrate present in the original substrate was recovered in the water insoluble fraction after Na2CO3 addition. More than 80% of the sugars present in the original cellulose and xylan could be recovered after 48h using an enzyme loading of 20mgprotein/g cellulose at a 10% substrate concentration.

Synthesis of novel CaCO3/Ag2CO3/AgI/Ag plasmonic photocatalyst with enhanced visible light photocatalytic activity

In this work, novel CaCO3/Ag2CO3/AgI/Ag plasmonic photocatalysts were successfully synthesized by a two-step in situ ion exchange process and their photocatalytic properties were studied. The morphology, crystal structure and optical properties of the as-prepared CaCO3/Ag2CO3/AgI/Ag nanocomposites were characterized by transmission electron microscopy (TEM), X-Ray diffraction (XRD), and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the obtained nanocomposites was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation. It was found that the as-prepared CaCO3/Ag2CO3/AgI/Ag plasmonic photocatalyst exhibits high visible light photocatalytic activity. With an optimized composition, MO dye can be decomposed by more than 94% within 15 min under visible light irradiation. Moreover, the photocatalytic stability could be greatly improved upon the addition of Na2CO3 into the photocatalytic system. From the proposed photocatalytic mechanism, the strong surface plasmon resonance effect of Ag nanoparticles and the efficient separation of photogenerated electrons and holes can effectively enhance the photocatalytic performance of the CaCO3/Ag2CO3/AgI/Ag composites.

Improvement in liquid fuel product quality from reactions of grape marc with CO/H2O

Abstract Reactions of grape marc with CO/H2O have been investigated over a range of temperatures (320–425 °C) with and without added sodium carbonate (Na2CO3) or sodium aluminate (NaAlO2) with a view to optimising liquid fuel quality. The quality of the product can be improved by raising the temperature and/or by addition of alkali, Na2CO3 or NaAlO2, which helped to decarboxylate/decompose fatty acids and lower the oxygen content. The energy recovery of the dichloromethane soluble products ranged from 50% to 75%.

Roles of Na2CO3 in lignite hydroliquefaction with Fe-based catalyst

In this paper, the roles of Na2CO3 were investigated mainly for the lignite hydroliquefaction process with Fe-based catalyst. As a whole, Na2CO3 could play a synergistic role with Fe-based catalyst in obviously promoting the lignite conversion and the oil production and reducing water production. The synergistic effect mainly originated from these promotion actions of Na2CO3 to the depolymerization (for macromolecular structures in lignite) and hydrolyzation (for abundant oxygen-containing moieties in lignite). The promotion action of Na2CO3 for reducing water production was mainly attributed to the simultaneous promotion to the hydrolyzation of the ether bonds and carbonyl groups (especially ether bonds). The addition of Na2CO3 is more beneficial for the asphaltene conversion to oil than that for the preasphaltene conversion to oil in lignite hydroliquefaction with Fe-based catalyst.