Addition Of Na2CO3 Research Articles

Selective recovery of vanadium from high-chromium vanadium slag by a mechanically activated low-sodium salt roasting-water leaching process

Stabilizing the toxic element chromium and improving vanadium recovery are crucial for the economic and efficient treatment of high chromium-bearing vanadium slag. This study employed mechanical activation to enhance vanadium extraction from high chromium-bearing vanadium slag through a low-sodium salt roasting-water leaching process. The effects of Na2CO3 addition, roasting temperature, and roasting time were investigated to determine the optimal roasting parameters. Subsequently, the effects of mechanical activation on the morphological and microstructural changes were characterized using a laser diffraction particle size analyzer, a micropore physisorption analyzer, scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. The effects of mechanical activation on the extraction of vanadium and chromium were determined by leaching the roasted samples after varying activation times. The results indicated that mechanical activation decreased particle size, increased surface area, and enhanced the activity of the samples. The leaching results demonstrated that mechanical activation enhanced the leaching efficiency of vanadium by 5 %, reduced the optimum roasting temperature by 50 ℃, and slightly increased the leaching efficiency of chromium by 0.5–1 %.

An experimental and thermodynamic equilibrium investigation of heavy metals transformation in supercritical water gasification of oily sludge

Supercritical water gasification (SCWG) is an advanced and highly efficient method for treating oily sludge. However, it is crucial to consider the transformation characteristics of heavy metals (HMs) during the SCWG process to prevent potential secondary pollution. This work studied the transformation and distribution characteristics of Cu, Cr and Zn after SCWG of oily sludge in a batch reactor at temperatures ranging from 550 to 700 °C. Additionally, thermodynamic equilibrium analysis was conducted to assess the distribution of HMs based on the minimization of Gibbs free energy. Experimental results indicated that higher temperatures led to the conversion of HMs into more stable forms, effectively immobilizing them within solid products. Furthermore, the addition of Na2CO3 enhanced this process and contributed to a reduction in HMs pollution in the effluent. Thermodynamic equilibrium results were consistent with our experimental data, indicating that the molar fraction of stable HMs forms followed the order: Cr > Cu > Zn. Besides, it is worth noting that Na2CO3 had a limited impact on the distribution of Cu and Cr. However, it played a significant role in inhibiting the formation of silicate Zn at lower temperatures, promoting the decomposition of ZnO*Al2O3 into unstable Zn. This may explain the higher presence of unstable Zn when Na2CO3 was introduced. In summary, this study offers valuable insights into the transformation characteristics of heavy metals and strategies for pollution control during SCWG of oily sludge.

Microstructure Evolution and Phase Transformation of Iron Produced from the Sustainable Carbothermic Reduction Process of High-Pressure Acid Leaching Residue.

This paper describes the microstructure evolution and phase transformation of residue from the lateritic nickel ore high-pressure acid leaching (HPAL) during carbothermic reduction using palm kernel shell (PKS) charcoal as a reductant. The study consisted of thermodynamic calculations combined with analysis of reduction experiments. The thermodynamic assessment predicted that the main phases formed during the reduction process were γ-Fe metal, liquid metal, slag, and spinel, with abundance of reducing gas (CO and H2) at the temperature range of 750-1500 °C. The experimental study shows that the resulting product upon cooling was sponge iron or direct reduced iron when HPAL residue-PKS charcoal composites were reacted up to 1400 °C for 45 min. The sponge iron had an average apparent density of 5.8 ± 0.1 g/cm3 and a 90.8 ± 0.4% metallization degree. The microstructure analysis revealed that as the reduction time was increased, small iron nuggets began forming on the surface of the reduced product. By addition of Na2CO3, the separation of iron nuggets from slag appeared to be improved, hence enhancing the overall reduction process. Furthermore, iron nuggets' highest apparent density and metallization degree were obtained at 7 ± 0.1 g/cm3 and 98 ± 0.5%, respectively, when adding Na2CO3 of 6 wt %. The phase and microstructure analyses also revealed that the iron nuggets comprised coarse pearlite, eutectic cementite, ledeburite, and sulfides. Thus, this study offers alternative sustainable process conditions for simultaneously handling the HPAL residue using PKS waste to produce metallic iron.

Application of Cold Sintering Process for Stabilizing Heavy Metals in Municipal Solid Waste Incineration Fly Ash

Municipal solid waste incineration fly ash (MSWI FA) consists predominantly of compounds comprising elements such as calcium, aluminum, silicon, sodium, and others. Additionally, it encompasses a complex mixture of heavy metals, chlorides, sulfates, organic pollutants, and other constituents. The effective and economically viable treatment of MSWI FA poses a formidable challenge for resource cycling at the current stage. In this research report, we adopt a novel low-temperature sintering method called the “Cold Sintering Process” (CSP) as a means to immobilize heavy metals within the fly ash. By utilizing a Taguchi orthogonal array method, we will adjust five control factors in the CSP, including sintering temperature, uniaxial pressure, sintering time, initial water addition, and sodium carbonate dosage. The leaching of cadmium from the fly ash, as measured by the Toxicity Characteristic Leaching Procedure (TCLP), will serve as the quality indicator of products. Through the application of CSP, MSWI FA was transformed into structurally stable ceramic blocks, and the heavy metals within the blocks were effectively immobilized. The results of the experiments showed that MSWI FA under the conditions of a temperature of 300 °C, uniaxial pressure of 312 MPa, sintering time in 60 min, 25 wt% water addition, and 9 wt% Na2CO3 addition could effectively reduce the leaching of cadmium by 77.71%, lead by 21.14%, zinc by 42.37%, and chromium by 99.99%, as compared to the original MSWI FA TCLP results. The X-ray Diffraction (XRD) results indicate that during the CSP, fly ash forms phases such as calcium silicate, rankinite, hydrogrossular, anorthite, and marilite. These phase transformations are considered beneficial for preventing the leaching of internal heavy metals. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) results reveal that CSP is advantageous for compacting the overall structure, and EDS results further demonstrate that some of the Pb and Zn are carried out from the interior of the blocks, with uneven distribution on the surface of fly ash particles. The aforementioned experimental results serve as preliminary indications of CSP’s capability to stabilize detrimental components within high-purity fly ash. Future research endeavors may entail the refinement of material proportions, modification of experimental parameters, and other methodologies, thus facilitating potential scalability to industrial applications. Such developments align with the overarching goal of resource utilization.

Enhancing lipases reactivity in benzylic acetates hydrolysis: impact of kosmotropic salts under non-conventional conditions

The effect of four kosmotropic salts additives, namely Na2CO3, Na2SO4, Na2HPO4, and NaCl, on the reactivity and selectivity of immobilized Candida antarctica lipase B (CAL-B) and a free lipase of Pseudomonas cepacia (PCL) during the hydrolysis of rac-4-(1-methoxyphenyl) ethyl and rac − 1-phenyl ethyl acetates (1a-2a) was investigated in this study. The study was carried out in two different mediums: non-aqueous conditions and in low water content media. The impact of the anionic counter-ions was examined in four solvents: nonpolar, semipolar, protic, and aprotic, with and without the aforementioned salts. In non-aqueous media, the addition of Na2CO3 significantly enhanced CAL-B hydrolysis rates, resulting in a conversion of 50% for 1a and 44% for 2a, with high enantioselectivities (E > 200). These effects were independent of the solvent hydrophobicity. In contrast, PCL required the presence of external water for effective hydrolysis of both acetates. The addition of salt additives had an adverse impact on PCL activity during the hydrolysis of 1a in hexane, toluene, and TBME solvents. However, when 2M2B was used, the inclusion of salt additives had a notable positive effect on the conversion rates, except for NaCl, which resulted in a lower conversion rate with a value of 15.5%. The presence of Na2CO3 improved the conversion rate during the hydrolysis of 2a in both hexane and TBME. Na2HPO4 further enhanced the conversion rate, reaching 44% in TBME. However, in 2M2B solvent, the addition of Na2HPO4 significantly reduced the enantioselectivity.

Preparation of foam glass ceramics from hazardous waste vitrification slag with the addition of Na2CO3

Hazardous waste vitrification has been recognized as an effective method for waste treatment, but there is still a need to explore the utilization of its vitrification slag. The feasibility of preparing foam glass ceramics from hazardous waste vitrification slag was verified in this study based on the thermodynamics analysis and the experimental exploration of the effect of the Na2CO3 addition on the transformation of hazardous waste vitrification slag (HWVS) during the roasting process. Thermodynamic calculations and TG-DSC analysis results inferred that the suitable theoretical roasting temperature for preparing foam glass ceramics from the HWVS/Na2CO3 should be 900 °C–1000 °C. The experimental results demonstrated that a good foam glass ceramics with bulk density of 0.50 g/cm3, compressive strength of 1.93 MPa, apparent porosity of 74.10%, and water absorption ratio of 0.30% can be obtained by roasting HWVS with 4 wt% Na2CO3 and 2 wt% trisodium phosphate at 950 °C for 1 h. During the preparation process of foam glass ceramics, the thermal decomposition of Na2CO3 generated a large number of bubbles, achieving foaming and expansion. Additionally, the appropriate content of the liquid phase generated during roasting acted as a consolidating agent during cooling, enhancing the strength of foam glass ceramics. These findings provide valuable insights for the resource utilization of vitrification slag.

Effect of sodium carbonate on the properties of seventy percent of Tartary buckwheat composite flour-based doughs and noodles and the underlying mechanism.

The impact of Na2 CO3 on the properties of doughs and noodles containing 70% Tartary buckwheat flour was investigated. Low-field 1 H nuclear magnetic resonance showed the mobility of water in the doughs significantly declined with the addition content of alkali from 0% to 0.9%. Na2 CO3 promoted the transformation from free sulfhydryl groups to disulfide bonds in doughs because the sulfhydryl groups in cysteine preferred to form thiolate anion and then oxidate under alkaline conditions. As for non-covalent chemical interactions, a significant increase of hydrogen bonds and a decrease of hydrophobic interactions were observed after Na2 CO3 addition. Quantitative analysis of microstructure showed that more uniform and denser gluten networks with higher branching rate and shorter average protein length and width formed in the doughs with 0.3%-0.6% of Na2 CO3 . The aggregated glutenin macropolymer and enhanced protein structure led to significantly stronger tensile of Tartary buckwheat dough sheets, which could meet the demand of continuous processing in the factory. Dough with alkali had higher swelling power and pasting viscosities, contributing to higher water absorption, and improved textural attributes of cooked noodles. This study demonstrated the possibility of adding Na2 CO3 at a moderate level for promoting the sheeting, cooking, and eating properties of high Tartary buckwheat flour composite noodles.

Effects of sodium carbonate admixture and mix design ratios on the compressive strength of concrete

This study aimed to investigate the impact of sodium carbonate (Na2CO3) admixture on the acceleration and long-term compressive strength of ordinary Portland cement (OPC) concrete at different mix ratios. Concrete cube specimens (150 × 150 × 150mm3 size) were cast at three different mix ratios (1:1.5:3, 1:2:4, and 1:3:6) with sodium carbonate admixture added in increasing dosage of 0.5% from 0 to 2.0% by weight of OPC. Compressive strength tests were conducted on the cast specimens after curing under water for 7, 28, 56 and 90days. Additionally, tests were done to see how sodium carbonate would accelerate setting times of OPC paste. The results of the tests showed that Na2CO3 decreased the initial and final setting times of cement paste from 96 to 67mins and 543 to 387mins respectively. Compressive strength test results for 1:2:4 and 1:3:6 mix ratios showed an increasing trend up to 1.0% Na2CO3 admixture, after which there was a decrease. Meanwhile, 1:1.5:3 mix ratio showed a decrease in strength from 21.87 N/mm2 at 0% to 14.90 N/mm2 at 1.0% Na2CO3 addition, after which the strength increased with Na2CO3 percent addition. These results suggest that sodium carbonate has an accelerating effect on concrete setting time, and may aid its early strength development, but has negative long-term effects on concrete strength with increasing dosage. An optimal percentage of 1% Na2CO3 by weight of OPC is advised for accelerating effects in concrete, based on the results of this study.

Recycling of silicon from waste PV diamond wire sawing silicon powders: A strategy of Na2CO3-assisted pressure-less sintering and acid leaching

Recycling diamond wire sawing silicon powders (DWSSP) from photovoltaic (PV) silicon wafers production has become an urgent problem. The challenge of recovery is the surface oxidation and contamination of the ultra-fine powder with impurities during the sawing and collection process. In this study, a clean recovery strategy of Na2CO3-assisted sintering and acid leaching was proposed. Due to the Al contamination from the perlite filter aid, the introduced Na2CO3 sintering aid can react with the SiO2 shell of DWSSP to form a slag phase with accumulated impurity Al during the pressure-less sintering process. Meanwhile, the evaporation of CO2 contributed to the formation of ring-like pores surrounded by a slag phase, which can be easily removed by acid leaching. When 15 % Na2CO3 was added, the content of impurity Al in DWSSP could be reduced to 0.07 ppm with a removal rate of 99.9 % after acid leaching. The mechanism suggested that the addition of Na2CO3 can trigger the liquid phase sintering (LPS) process of the powders, and the cohesive force and liquid pressures difference generated during the process facilitated the transportation of impurity Al from the SiO2 shell of DWSSP to the formed liquid slag phase. The efficient silicon recovery and impurity removal of this strategy demonstrated its potential for solid waste resource utilization in the PV industry.

Structure of Na Species in Promoted CaO‐Based Sorbents and Their Effect on the Rate and Extent of the CO2 Uptake

AbstractTo advance CaO‐based CO2 sorbents it is crucial to understand how their structural parameters control the cyclic CO2 uptake. Here, CaO‐based sorbents with varying ratios of Na2CO3:CaCO3 are synthesized via mechanochemical activation of a mixture of Na2CO3 and CaCO3 to investigate the effect of sodium species on the structure, morphology, carbonation rate and cyclic CO2 uptake of the CO2 sorbents. The addition of Na2CO3 in the range of 0.1–0.2 mol% improves the CO2 uptake by up to 80% after 10 cycles when compared to ball‐milled bare CaCO3, while for Na2CO3 loadings >0.3 mol% the cyclic CO2 uptake decreases by more than 40%. Energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy, X‐ray absorption spectroscopy (XAS), and 23Na MAS NMR, reveal that in sorbents with Na2CO3 contents <0.3 mol% Na exists in highly distributed, noncrystalline [Na2Ca(CO3)2] units. These species stabilize the surface area of the sorbent in pores of diameters >100 nm, and enhance the diffusion of CO2 through CaCO3. For Na2CO3 contents >0.3 mol%, the accelerated deactivation of the sorbents via sintering is related to the formation of crystalline Na2Ca(CO3)2 and the high mobility of Na.

Physicochemical properties of sodium alginate from brown algae Sargassum aquifolium and Sargassum cinereum

Synthesis and characterization of sodium alginate from Sargassum aquifolium dan Sargassum cinereum have been successfully performed. S. aquifolium and S. cinereum were collected from the Dompu Islands, West Nusa Tenggara, Indonesia. Extraction was performed by acid pathway, due to cell disruption and the addition of Na2CO3 for extraction. The addition of HCl was to convert acid alginate into alginate, then transformed acid alginate into sodium alginate using NaOH. NaOCl and IPA were used for purification. Physicochemical properties were characterized using SEM-EDS, FTIR, and TG/DTG. The morphological structure of synthetic sodium alginate shows layer structure and fiber fibrils. Sodium alginate contained C, O, Na, and Cl elements. FTIR spectrum indicated the presence of functional groups at the following wavelengths: OH at 3343 cm−1, CH2 at 2915 cm−1, CO double bonds at 1614 cm−1, and fingerprint indicated by the presence of uronic acid, which functioned as the CH group stretched at 935 cm−1. The sodium alginate sample shows a three-step thermal degradation pattern. The first step was starting at 41.7 °C associated with dehydration and was followed by 206.4 and 241 °C associated with decomposition. TGA/DTG results showed a reduction in thermal stability at 250–300 °C. It is suitable for modification and application.

0D/2D Nb2O5/ZnIn2S4 heterojunctions with enhanced utilization of light and separation of photogenerated carrier for efficient visible light photocatalytic performance

0D/2D heterojunctions via the single-photon excitation can avoid the light shielding of non-active component to promote the photocatalytic activity. However, it is very difficult to prepare ultrasmall nanoparticles loaded on 2D nanosheets via one pot method. Heren, we fabricated a Nb2O5/ZnIn2S4 (Nb-ZIS) heterojunction via a simple solvothermal process assisted by the Na2CO3 and thioacetamide (TAA), where zero-dimensional (0D) ultra-small Nb2O5 particles (≈10 nm) are uniformly in-situ grown on two-dimensional (2D) ZnIn2S4 nanosheets (ZIS). Structural characterizations and density functional theory (DFT) calculation suggest that the 0D-on-2D interface can not only alleviate the blocking effect of light, promoting light absorption for photocatalytic process, but also enhances the separation of photon-generated carriers through the built-in electric field (BIEF). Encouragingly, the Nb-ZIS heterojunction shows significant enhancement for H2 evolution and degradation of lignin, where the hydrogen evolution rate reaches 5.4 mmol h−1 g−1 and the lignin degradation rate achieves 78.5%, surpassing the commercial block Nb2O5 supported on ZIS heterojunction (Nb-ZIS-C) (4.0 mmol h−1 g−1 for hydrogen evolution and 61.9% for degradation) and the 0.2Nb/ZIS without the addition of Na2CO3 (4.5 mmol h−1 g−1 for hydrogen evolution and 72.3% for degradation), respectively.

Effect of alkaline metals (Na, Ca) on heavy metals adsorption by kaolinite during coal combustion: Experimental and DFT studies

Kaolinite can adsorb heavy metals (Cu, Zn, Pb, and Cd) and alkaline metals (Na and Ca) during coal combustion. However, the effect of alkaline metals on the heavy metals (HMs) adsorption by kaolinite is not clear. In this paper, in order to minimize the interference of associated minerals in the coal during the HMs adsorption by kaolinite, demineralized coal and kaolinite were assembled as base coal. Then experimental and density functional theory (DFT) were combined to analyze the effect of NaCl, Na2CO3, and CaO on the adsorption of Cu, Zn, Pb, and Cd by kaolinite. The results showed that the addition of NaCl decreased the fixation rate of Pb from 46.54% to 4.27% at 1000 °C. The fixation rates of HMs gradually decreased with the addition of Na2CO3. However, the addition of CaO did not cause a significant reduction in the fixation rates of HMs. Meanwhile, the alkaline metals increased the leaching risk of HMs from the ash. From 800 °C to 1200 °C, the fixation rates of Pb and Cd fell significantly with increasing temperatures at a CaO loading amount of 6 wt%. However,the fixation rates of Cu and Zn were little affected by increasing temperatures. The DFT calculations indicated that the adsorption of HMs on the metakaolin(001) surface was inhibited by NaCl and Na2O. Effective adsorption of HMs was still feasible after the combination of CaO and metakaolin, and Ca was the adsorption site for O (from oxidized HMs) atoms. This work revealed the effect and mechanisms of alkaline metals on the HMs adsorption by kaolinite.

Decontamination of uranium-containing radioactive waste from stainless steel surfaces using NaOH-based molten salts.

Herein, we report a new strategy for the rapid removal of uranium-containing contaminants from metal surfaces, and it relies on decontaminants made of NaOH-based molten salts. The addition of Na2CO3 and NaCl to NaOH exhibited superior decontamination performance, with a decontamination rate of 93.8% within 12 min, outdoing the performance of the single NaOH molten salt. The experimental results demonstrated that the synergistic effects between CO32- and Cl- promoted the corrosion efficiency of the molten salt on the substrate, which accelerated the decontamination rate. Additionally, benefiting from the optimization of the experimental conditions by the response surface method (RSM), the decontamination efficiency was improved to 94.9%. Notably, it also showed remarkable results in the decontamination of specimens containing different uranium oxides at low and high levels of radioactivity. This technology is promising for broadening the path in rapid decontamination of radioactive contaminants on metal surfaces.

Revealing the Effect of Anions on the Formation and Transformation of Zeolite LTA in Caustic solutions: AnIn SituSynchrotron PXRD Study

Zeolite LTA is one of the largest industrial zeolites in both volume and market value. Natural resources or manufacturing wastes such as clay minerals, fly ash, and lithium slag are now used as raw materials for the economically and environmentally friendly synthesis of zeolites. However, soluble impurities such as inorganic anions (CO32–, SO42–, and PO43–) in these feeds have significant effects on the quality of zeolite LTA products, because these impurities enhance or inhibit the formation of other unwanted phases (amorphous zeolites or sodalite) via mechanisms that remain poorly investigated. Here we use in situ synchrotron powder X-ray diffraction to study the effects of different inorganic salts (Na2CO3, Na2SO4, and Na3PO4) on the kinetics of the sequential phase transformations in zeolite LTA during 2.5 h of reaction at 90 °C in both weakly and highly alkaline solutions. The results show that different salts have no effects on the amorphous phase formation stage but do affect the zeolite or sodalite crystallization stage. The addition of Na2CO3 increases the dissolution rate of zeolite, but it barely promotes the crystallization rate of sodalite. The addition of Na3PO4 inhibits sodalite crystallization, whereas the addition of Na2SO4 is most effective in facilitating sodalite formation and improving final sodalite particle size. Also, SO42–-bearing sodalite has a larger unit cell than other types of sodalites. These outcomes suggest that both CO32– and SO42– have negative effects on stabilizing zeolite LTA phases but PO43– has positive effects on these products.

Hydrogen production from oilfield wastewater by gasification in supercritical water with a continuous system

Multi-component supercritical thermal fluid (MCSCTF) generated based on supercritical water gasification (SCWG) technology can significantly enhance heavy oil recovery. In this paper, the performance of oilfield wastewater SCWG was systematically investigated with a continuous system. Thermodynamic analysis showed that total gasification of oilfield wastewater in supercritical water (SCW) was feasible due to the inhibition of coke generation. The addition of Na2CO3 or K2CO3 can facilitate steam reforming and water–gas shift reactions to achieve high H2 yields and carbon gasification efficiency (CE). The generation of the abundant gas was attributed to the rapid decomposition of the liquid products by free radical reactions at high temperatures. As the feedstock concentration increased, the oil–water emulsion structure may favor the intense pyrolysis reaction over the steam reforming reaction resulting in lower CE. The suitable ratio of emulsion to preheat water flow (1:5) can increase the heating rate of the feedstock and ensure the decomposition time of the intermediate products to obtain high CE (96%). The trends in the change of gas products at different operating parameters were supported by thermodynamic calculations. This work can provide the basis for the subsequent coupled hydrogen oxidation technology to generate MCSCTF.

Effect of alkali metal promoters on catalytic performance of Co-based catalysts in selective hydrogenation of aniline to cyclohexylamine

Abstract In this study, a series of Co-based catalysts with alkali metal carbonate promoters were prepared to investigate the interrelation between promotion effect of these carbonates and catalytic performance for aniline hydrogenation to cyclohexylamine in vapour phase. The chemical promoters Li2CO3 and Na2CO3 leading to decrease in catalytic activity of cobalt catalysts for aniline hydrogenation. Catalysts with K2CO3 and Cs2CO3 loadings have practically no catalytic activity for hydrogenation of aniline. Results of TPD of aniline proved that presence of alkali metals carbonates restricts the adsorption of aniline on the surface of cobalt catalysts. Further, it was found that the addition of Na2CO3 greatly enhances the catalytic selectivity towards the cyclohexylamine and inhibits the consecutive reactions of cyclohexylamine leading to formation of by-products such as dicyclohexylamine and N-phenylcyclohexylamine.

Recycling lead from waste lead-acid batteries by the combination of low temperature alkaline and bath smelting

Recycling lead from waste lead-acid batteries has substantial significance in environmental protection and economic growth. Bearing the merits of easy operation and large capacity, pyrometallurgy methods are mostly used for the regeneration of waste lead-acid battery (LABs). However, these processes are generally operated at the temperature higher than 1300 °C. To shorten the energy consumption, a novel pyrometallurgy process which consisted of low temperature alkaline and bath smelting was proposed in this work. The reduction of lead and smelting of slag system are the key factors determine the energy consumption. Thermodynamic calculation suggested that the addition of Na2CO3 can make the reduction of PbSO4 spontaneously at the temperature higher than 288 °C (PbSO4 → PbCO3 → PbO → Pb), while direct reduction of PbSO4 necessitated the temperature higher than 1499 °C (PbSO4 → PbO → Pb). To achieve the efficient reduction of PbSO4, the molar ratios of C/PbSO4 and Na2CO3/PbSO4 should be higher than 0.5 and 1.0, respectively. Meanwhile, a new smelting system (i.e., FeO-SiO2-CaO-Na2O) was established in the presence of Na2CO3. Phases with low melting temperatures, such as NaFe2O3, Na2FeSiO4, Na2Ca2Si2O7, Na14Fe6O16 and Na0.5FeO2, were formed. The melting temperature of Fe-Si-Ca-Na system was lowered to 1050 °C at the mass dosage of Na2CO3 at 30%. Recovery of lead under various reduction conditions were systematically evaluated. Under optimum operational conditions, i.e., the dosages of C and Na2CO3 at 10% and m(actual)/m(theory) ratio of 1.3 (all in mass), smelting temperature of 1050 °C, and smelting time of 75 min, respectively, the lead recovery efficiency reached >98.0%. Moreover, this method has been successfully applied for the industrial recovery of lead at the scale of 200, 000 tons annually since 2019. Taken together, this method is robust for recovery of lead from the waste LABs and is helpful for building the resource-conserving society.

Development and comprehensive characterization of low-cost hybrid clay based ceramic membrane for power enhancement in plant based microbial fuel cells (PMFCs)

A variety of low-cost hybrid clay based ceramic membranes were developed for application in plant based microbial fuel cells (PMFCs). The membranes were prepared by using locally available clay mixed with varying concentrations of sodium carbonate, sodium metasilicate, boric acid, bentonite, and fly ash. Physiochemical characterization was carried out by using TGA, XRD, FESEM, FTIR, flexural strength test, water uptake, proton conductivity, oxygen and acetate diffusion and compared with Nafion117. Performance of ceramic membranes in PMFCs was evaluated by using the plant E. aureum with carbon fiber brush electrode. Membrane having composition of clay-55%, bentonite-15%, flyash-15%, Na2Co3-8%, Na2Sio3-2%, H3Bo3-5% exhibited maximum power density of 22.38 mW m−2 which was 78% higher than control (100% clay) with a decrease in internal resistance from 346 Ω to 234 Ω. The study demonstrates that the addition of bentonite, fly ash, Na2Co3, Na2Sio3 and H3Bo3 with clay at a concentration of 15%, 15%, 8%, 2%, and 5% respectively improved membrane cation transport ability, reducing oxygen diffusion and substrate crossover at the same time. The membrane demonstrated extreme stability for long term operations involving more than six months’ period. The low cost of production of clay based ceramic membrane at ₹1279/ft2 can be a good alternative to highly priced commercially available proton exchange membranes.

A new iron recovery and dephosphorization approach from high‑phosphorus oolitic iron ore via oxidation roasting-gas-based reduction and magnetic separation process

Deep dephosphorization of high‑phosphorus oolitic iron ore (HPOIO) is extremely difficult because of its refractory characteristics. A new approach for simultaneous iron recovery and dephosphorization from HPOIO by oxidation roasting–gas-based reduction (ORGR) and magnetic separation process was developed. The underlying mechanism was investigated using thermodynamic calculations, X-ray diffraction (XRD), and scanning electron microscopy combined with energy dispersive spectroscopy (SEM–EDS). The results showed that the powdery reduced iron produced contained 91.37% iron and 0.14% phosphorus, and the iron recovery was 92.81%, which is an ideal for steelmaking. The addition of Na2CO3 formed nepheline, which promoted the formation and coarsening of hematite during oxidation. Concurrently, Na2CO3 reacted with the phosphorus in the iron minerals and fluorapatite to form sodium calcium phosphate, which was embedded in hematite with a simple relationship. Hematite was subsequently converted into metallic iron, sodium calcium phosphate was not reduced, and metallic iron and phosphorus were separated efficiently.