Carbonation Route Research Articles

Cover Feature: Template‐Induced Self‐Activation Route for Hierarchical Porous Carbon Derived from Interpenetrating Polymer Networks as Electrode Material for Supercapacitors (ChemElectroChem 10/2019)

Cover Feature: Template‐Induced Self‐Activation Route for Hierarchical Porous Carbon Derived from Interpenetrating Polymer Networks as Electrode Material for Supercapacitors (ChemElectroChem 10/2019)

Fabrication, characterization and response surface method optimization for quantum efficiency of fluorescent nitrogen-doped carbon dots obtained from carboxymethylcellulose of oil palms empty fruit bunch

Abstract Bio based nitrogen doped carbon dots (N-CDs) were obtained from empty fruit bunch carboxymethylcellulose and ethylenediamine (EDA) through one-pot hydrothermal carbonization route. The optimum as-formed N-CDs were thoroughly characterized via Transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS), UV–vis spectra (UV–Vis) and Fluorescence spectra (PL). Response surface methodology was statistically used to assess three independent variables that have major influence on the fluorescence quantum yield (QY), including temperature (230–270 °C), time (2–6 h) and EDA mass (10%–23.3%). Based on analysis of variance (ANOVA) results, synthesis temperature was found to be the most influential factor on the QY, followed by time and EDA mass. Higher temperature, long synthesis time and high amount of EDA were satisfactorily enough for efficient carbonization conversion rate and obtaining highest QY of N-CDs. The obtained quadratic model (R2 = 0.9991) shows a good correlation between the experimental data and predicted values. The optimum synthetic parameters are of 270 °C temperature, 6 h reaction time and 23.3% of EDA mass. The optimized as-made N-CDs exhibited blue photoluminescence with both excitation dependent/independent phenomena and high nitrogen content. The maximum emission intensity was 426 nm at a maximum excitation wavelength of 320 nm, with a QY of up to 22.9%. XPS and FTIR data confirmed the existence of polar containing groups, such as carbonyl, carboxyl, hydroxyl and amino groups over the surface of N-CDs whereas nitrogen species in the form of (pyridinic and graphitic − N) were introduced in the aromatic carbon domains, which imparts the hydrophilic and photostability of N-CDs. Taking into account the low-cost and sustainable production of N-CDs, this method considered a feasible route for converting low quality waste into value-added nanomaterials and utilizing for different functionalization processes and analytical applications.

Energy Use of Flux Salt Recovery Using Bipolar Membrane Electrodialysis for a CO2 Mineralisation Process.

Mineral carbonation routes have been extensively studied for almost two decades at Åbo Akademi University, focusing on the extraction of magnesium from magnesium silicates using ammonium sulfate (AS) and/or ammonium bisulfate (ABS) flux salt followed by carbonation. There is, however, a need for proper recovery and recirculation of chemicals involved. This study focused on the separation of AS, ABS and aqueous ammonia using different setups of bipolar membrane electrodialysis using both synthetic and rock-derived solutions. Bipolar membranes offer the possibility to split water, which in turn makes it possible to regenerate chemicals like acids and bases needed in mineral carbonation without excess gas formation. Tests were run in batch, continuous, and recirculating mode, and exergy (electricity) input during the tests was calculated. The results show that separation of ions was achieved, even if the solutions obtained were still too weak for use in the downstream process to control pH. Energy demand for separating 1 kg of NH4+ varied in the range 1.7, 3.4, 302 and 340 MJ/kg NH4+, depending on setup chosen. More work must hence be done in order to make the separation more efficient, such as narrowing the cell width.

Template‐Induced Self‐Activation Route for Hierarchical Porous Carbon Derived from Interpenetrating Polymer Networks as Electrode Material for Supercapacitors

AbstractHierarchical porous textures of carbon‐based electrode materials are advantageous for applications in supercapacitors, owing to their reasonable pore size distribution and large surface area. In this work, a facile yet effective one‐step carbonization method for the preparation of hierarchical porous carbons (HPCs) derived from interpenetrating polymer networks (IPNs) of phenol‐formaldehyde resin (PF) and sodium polyacrylate (PAAS) is proposed. Phenol‐formaldehyde prepolymer can be introduced into the inter network space of PAAS to form IPNs in which only hydrogen‐bonding interactions exist between them. During the carbonization process of IPNs, the PF networks tend to form a carbon matrix, which generates large amounts of micropores. While the PAAS evaporates into gaseous products, serving as a template for micro‐, meso‐, and macropores. Due to such synergistic effects, a carbon material with a large surface area of 1764 m2 g−1 and a large pore volume of 1.111 cm3 g−1 is constructed with an interconnected hierarchical porous carbon network structure. With such unique carbon structure characteristics, the electrode material of HPC delivers a high specific capacitance of 201 F g−1 at 0.5 A g−1 and excellent cyclability of approximately 100 % of capacitance retention after 10000 cycles. The ideal capacitive behavior from IPNs provides new insights for the production of carbonaceous materials for high‐performance supercapacitors applications.

Aqueous carbonation of MgSO4 with (NH4)2CO3 for CO2 sequestration

AbstractMineral carbonation is an important technical option for the effective reduction of CO2 emissions. Natural magnesium‐containing minerals, such as serpentine and blast furnace slag (BFS), have recently been used for CO2 storage with an indirect carbonation route using ammonium sulfate. In this study, the effects of the feeding mode and process parameters on the magnesium conversion, product phase, and morphology during the aqueous carbonation of MgSO4 with ammonium carbonate solution were investigated in detail. The results showed that the carbonation ratio with a parallel feed was higher than the forward and reverse feed by about 3–5% with a limited reaction time, and the product size was more uniform. The phase and morphology of the products were affected significantly by the temperature. The highest carbonation ratio appeared at 40°C because only 75% of magnesium was carbonated if hydromagnesite was produced. When the mole ratio of (NH4)2CO3 to MgSO4 was 2:1 and the concentration of magnesium sulfate was higher than 0.4 mol·L−1, the carbonated products contain ammonium magnesium carbonate, and the ammonia should be recovered by selective thermal decomposition. When the mole ratio decreased to 1.5:1, only nesquehonite appears with high crystallinity and uniform size. The optimized conditions were therefore selected as 40°C, a mole ratio of 1.5:1, and magnesium sulfate concentration of 0.7 mol·L−1. Under these conditions the carbonation ratio reached 88%. Additionally, the optimal initial pH of MgSO4 solution was 9.5 (the product was nesquehonite at low pH) while the hydromagnesite will be produced at higher pH (pH more than 10). © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Carbonation of BOF Slag in a Rotary Kiln Reactor in View of the Scale‐Up of the Wet Route Process

Carbonation of alkaline residues represents a potentially interesting technique for permanently storing in solid form CO2 contained in flue gas, syngas or biogas, as well as for the valorization of the residues. In particular, the wet carbonation route requires a low amount of water, does not generate wastewater and can be exploited to produce aggregates. The efficacy of this route has been demonstrated at laboratory scale. In view of its scale‐up, this study was aimed at evaluating the performance of a wet‐route carbonation process applied to Basic Oxygen Furnace (BOF) steel slag employing an operating procedure that could be adopted also at demonstrative or full scale. Dry residues were directly fed by a loading hopper into a rotary kiln reactor, in which gas containing 40% CO2 and steam were flown through. During the experiments, the flow and composition of the gas phase were continuously monitored, allowing to calculate the amount of CO2 captured from the gas phase and to compare it with the CO2 uptake of the solid product. In addition, the leaching behavior of the treated slag was assessed. The results of the tests were close to those obtained in previous experiments performed with pre‐humidified BOF slag, both with the same reactor used in this study and at laboratory scale; this suggests that this more automated wet‐route process could be employed for demonstration or full scale tests. The set up still needs to be optimized to obtain a product with physical and technical properties suitable for use as aggregate. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13140, 2019

Precipitation of Spherical Vaterite Particles via Carbonation Route in the Bubble Column and the Gas-Lift Reactor

Spherical vaterite particles were produced by carbonation of calcium chloride solution with addition of ammonia to facilitate CO2 absorption. Synthesis of calcium carbonate was carried out in a bubble column or gas-lift reactor. The course of the reaction was monitored by pH measurements. Precipitated solids were analyzed by Fourier-transformed infrared spectroscopy, x-ray powder diffraction and scanning electron microscopy, and the particle size distribution was determined by a laser diffraction method. Synthesized calcium carbonate products were mainly vaterite. The calcium chloride concentration and carbon dioxide volume fraction in a gas phase had the main impact on the size of the produced particles in both reactors. A slight decrease in the mean particle size was observed for the highest mixing intensity. Both tested reactors can be applied to produce vaterite particles, although formation of homogeneous non-agglomerated spherical particles in a gas-lift reactor required careful selection of the process parameters.

Calcium extraction and synthesis of precipitated calcium carbonate from Mg-rich dolomite

Abstract A green-reaction assisted synthesis using a natural occurring dolomite is reported for precipitated calcium carbonate production over aloe barbadensis miller extract template under ambient condition. Uniform, hierarchical aragonite precipitated calcium carbonate stacked from nanoparticles was synthesized. The tainted Mg influence on resultant PCC purity was averted via D-glucose extraction of dolomite constituent calcium and subsequent precipitation using CO2. The as-synthesized PCC was characterized using SEM, XRD, PSD, and FTIR spectroscopy. Under ambient conditions using carbonation route and 1 L/min CO2 flowrate, aragonite polymorph with hierarchical flower-like structure was produced. Energy is conserved as heat is not required for phase transformation. Minerals & Environment (RAMM) 2018.

A High-Pressure Gas–Solid Carbonation Route to Produce Vaterite

A novel synthetic strategy based on a high pressure gas–solid reaction using urea as an additive to produce value-added CaCO3 material is reported. Results showed that at about 150 °C and 12 MPa the reaction attained complete carbonation with predominant spherical vaterite crystals via a self-sustained reaction. The influences of working conditions including pressure, temperature, Ca(OH)2/urea mass ratio, and reaction time on the mineralization process were studied. The as-prepared CaCO3 powder exhibited vaterite content as high as 94.2% and a surface area up to 32.9 m2/g. The mechanism study showed that the high-pressure CO2 acted as an inhibitor for urea decomposition at high temperature besides as a reactant; the urea entrapped Ca(OH)2 via its melt to stabilize vaterite formation by an amine functional group and initiated the carbonation process via tiny water triggered by its slight decomposition. The separation to obtain the fine product was simple and allowed high urea recovery (for example, 93.6%)....

Placing hubs in CO2 pipelines: An application to industrial CO2 emissions in the Iberian Peninsula

Carbon capture and geological storage (CCS) is a key technology for the World deep decarbonization. However, several challenges remain, such as the optimization of the carbon transportation infrastructures. This study proposes a methodology that applies the Kernel Density function in a geographic information system software and uses as input, CO2 emission sources data to identify emission clusters and emission high-density hotspots. The main goal of the proposed methodology is to perform a preliminary screening to identify areas of interest to install hubs when designing an optimized CO2 pipeline network. The methodology includes an estimation of capturable CO2 emissions and a density analysis that was based on Kernel Density function from the ArcGIS Desktop 10. The methodology was applied to the Iberian Peninsula CO2 industrial emission sources such as refineries, coal and natural gas power plants and cement factories (case study) and the results showed that in Portugal, CO2 industrial emissions reduction can reach up to 68% and, in Spain, up to 74% of CO2 industrial emissions, could be avoided. These are called capturable CO2 emissions which means that they are the portion of the total emissions that can be captured from industrial processes before they reach the atmosphere. Moreover, hubs were shown to be more viable when Portugal and Spain are considered together, therefore, carbon routes (pipeline network) in the future may consider an integrated route for the Iberian Peninsula.

Effective protect of oxygen vacancies in carbon layer coated black TiO2−x/CNNS hetero-junction photocatalyst

Carbon layer coated black TiO2−x/g-C3N4 nanosheets (C@TiO2−x/CNNS) heterojunction photocatalysts were successfully prepared via a polydopamine dopamine carbonization route for the first time. It was found that the hydrogen evolution rate of C@TiO2−x/CNNS was 417.2 μmol h−1 g−1 under visible light irradiation, which was much higher than that of other prepared photocatalysts in solar water splitting process at the same conditions, and obvious decrease in catalytic activity can be observed after three recycles. The formation of carbon layer on the surface of TiO2−x can effectively protect Ti3+ and oxygen vacancies (Ovs) from oxidation by air and dissolved O2, afterwards much more Ti3+/Ovs are exsited, which can serve as charge carrier traps to inhibit the recombination of light-excited electrons-holes. Therefore, C@TiO2−x/CNNS showed a highly conductivity, rapidly effective electron-hole separation and lower transmission resistance comprehensive consideration of the advantages of carbon layer and hetero-junction, which are of great benefit to the improvement of photocatalytic performance. Hence, a new catalytic tactic namely layer-protection effect was founded and this strategy for boosting hydrogen evolution and protection Ti3+/Ovs may give us some hints on the design of photocatalytic systems.

Synthesis and electrochemical performance of a nanocrystalline Li4Ti5O12/C composite for lithium-ion batteries prepared using resorcinol–formaldehyde resins

Recently, spinel lithium titanate (Li4Ti5O12, LTO) has attracted attention as an anode material for lithium-ion batteries (LIBs). However, the poor electronic conductivity and low lithium-ion diffusion coefficient of LTO suppresses its electrochemical performance during quick charging. One possible way to improve the electrochemical performance is to reduce the LTO particle size to the nanometer range and modify the surface conductivity. In this study, LTO/C was synthesized by a one-step carbonization route without any specialized equipment using a resorcinol–formaldehyde (RF) resin as a carbon source, lithium acetate as a lithium source and polymerization catalyst, and commercial nano-sized TiO2 as a titanium source. The homogeneous mixing of the RF resin dissolved in water led to the uniform dispersion of the TiO2 and the Li source. The polymerization of the RF resin, TiO2, and dissolved Li source formed a closely structured matrix. LTO/C is comprised of crystalline LTO covered by a thin carbon layer. The RF resin plays an essential role in producing a suitable reaction field, preventing grain growth, and controlling the LTO primary particle size. The specific capacities of the LTO/C composite (carbon 15 wt%, carbonized at 900 °C) are 161 and 90 mAh/g at 0.1C and 25C, respectively. The composite shows improved electrochemical properties compared to commercial LTO.

CO2 Sequestration by Mineral Carbonation: A Review

<p>The mineral sequestration, one of the methods of CO2 sequestration, is considered advantageous, as it not only facilitates permanent and leakage free storage of CO2 but also obviates the need for regular monitoring. Mineral sequestration involves the dissolution of minerals and subsequently carbonation of dissolved minerals. In the direct mineral sequestration all the processes occur within a single reactor, whereas in the cases of indirect mineral sequestration, they take place in separate reactors. The main aim of the present study is to investigate the efficacy of these mineral sequestration methods and examine their suitability for industrial application and ensuring environmental friendliness. For this purpose, literature pertaining to these methods was extensively reviewed, and observations made by several researchers were collected, collated and compared based on the various parameters such as reaction pathways, reaction kinetics and cost of the process. The process cost was found to depend on the type of the process, process parameters, input materials and additives. It was noted that the direct mineral sequestration suffers from the sluggish reaction kinetics, thereby becomes economically unviable. The success of direct mineral sequestration process is yet to be achieved despite research carried out for several years. The problem of sluggish reaction kinetics was overcome by using multi-steps indirect carbonation routes, where separate reactors were used for dissolution and precipitation processes. The indirect sequestration method was noted to be most efficient as it offered several advantages such as improved reaction kinetics and recovery of the market value of by-product due to the better quality control of the product. Hence, based on interpretation of an extensive review of literature it can be concluded that the indirect mineral sequestration may be a viable option to carry out the CO2 sequestration and may be proved as a guiding light to ensure the clean environment for future generation.</p>

Facile and cost-efficient indirect carbonation of blast furnace slag with multiple high value-added products through a completely wet process

Mineral carbonation of blast furnace slag (BFS) has been proposed as a comprehensive method for carbon capture and storage and utilization of the industrial solid waste. However, the challenge for this technology to be applied practically is how to reduce the cost of process. A completely wet process combining a CO2-mineralization cell for CO2 capture and membrane electrolysis for recovery of carbonated mother liquor is proposed to simultaneously fix CO2 and produce multiple value-added products. In this process, Ca, Mg, Al, and Si are extracted from BFS with an NH4HSO4 solution prepared from H2SO4 and (NH4)2SO4 with extraction ratios of 97.3%, 98.8%, 96.4%, and 94.3% under optimized conditions, respectively. The extracted Al and Si are then recovered as NH4Al(SO4)2·12H2O (99.59 wt%) and SiO2 (97.70 wt%) with 93% and 98.1% yield, respectively. The CaSO4-rich leaching residue and MgSO4-rich leachate after complete depletion of the residual Al and Si are successively carbonated with an NH4HCO3 solution obtained from a CO2-mineralization cell with total CO2 capacity up to 361 kg-CO2 per tonne BFS. The preliminary economic evaluation shows that the present carbonation route is a cost-efficient method to comprehensively utilize BFS and reduce CO2 emissions.

Optimising the recovery of high-value-added ammonium alum during mineral carbonation of blast furnace slag

A route for the indirect mineral carbonation of blast furnace slag (BFS) with (NH4)2SO4 as a recyclable reagent has been proposed recently. To improve the economy of the process, an improved recovery route was put forward herein, guided by thermodynamic studies and phase diagrams. A purer, and thus higher-value-added byproduct, ammonium alum, can be obtained during the mineral carbonation of BFS. The effects of parameters such as roasting temperature and time, mass ratio of liquid to solid during leaching, and crystallisation temperature were investigated systematically. The results showed that the extraction reaction of BFS with ammonium sulfate occurred not only in the roasting stage but also in the leaching stage. The purity and recovery of aluminium as NH4Al(SO4)2·12H2O can reach 99.6% and 73%, respectively, at the optimal conditions. A preliminary economic evaluation predicted that this route can achieve 2.5 times the profit of the original process.

High‐Surface‐Area Nitrogen/Phosphorus Dual‐Doped Hierarchical Porous Carbon Derived from Biochar for Sulfur Holder

AbstractBiomass jellyfish umbrellas are used to prepare N,P‐codoped activated carbon (denoted as NPAC) through a soaking in NH4H2PO4 solution and activation process by potassium hydroxide. The key features of NPAC materials are the micro‐/mesopore coexistent structure and ultrahigh surface area (2307 m2 g−1), which displays the significance of carbon synthesis from biochars. When NPAC serves as the sulfur holder, it not only benefits the maximum encapsulation of sulfur in the pores but also restrains the dissolution of polysulfides through physisorption. Meanwhile, the N and P co‐doping is favorable for binding polysulfides by providing additional chemical adsorption sites via bonding with polysulfides. Relying on the synergistic effect of physi‐/chemisorption, the sulfur‐infiltrated NPAC material (NPAC−S) shows superior electrochemical performance to AC−S. After 300 cycles at a high current density of 1 C, the NPAC−S72 composite indicates a reversible capacity of 517 mAh g−1 with the capacity decay of 0.103% per cycle after 300 cycles. This work demonstrates that the biomass‐derived carbon route promises due to the unexpected textures of the as‐obtained carbon materials inherently from the special biological structures. The NPAC also shows a promising prospect in the application of absorbents, electrochemical catalysts, and capacitor materials, which inspires researcher to explore other new functional carbonaceous materials.

A facile synthetic route of nitrogen-doped graphite derived from chitosan for modifying LiFePO4 cathode

Nitrogen-doped carbon has been proved to be able to improve the cathode performance of lithium ion batteries (LIBs). As a cathode material, LiFePO4 (LFP) has been widely used for LIBs. However, it needs higher quantity of conductive carbons to enhance its electrochemical performances due to the low ion diffusion coefficient and poor electronic conductivity. Herein, we demonstrate a one-step and facile synthetic route of nitrogen-doped graphite carbon (NGC) for coating the LFP particles. It derives from the chitosan precursor by freeze drying technology and annealing at 600–800 °C. Raman spectroscopy and high-resolution transmission electron microscopy indicate the coating layer is the graphite carbon with a single layer nature. X-ray photoelectron spectroscopy test proves the existence of C–N or C=N (285.2 eV) bonding in the graphite carbon. After coating, the LFP@NGC cathode achieves a specific capacity of ∼ 155.5 mAh g−1 with Coulombic efficiency ∼ 97% at 0.1 C. The cell has a capacity of 63.2 mAh g−1 at 5 C after 100 cycles with Coulombic efficiency and capacity retention ratio of ∼ 100%. This work offers a new and facile route to fabricate NGC for the energy storage.

Highly passivated phosphorous and nitrogen co-doped carbon quantum dots and fluorometric assay for detection of copper ions.

Carbon quantum dots are becoming powerful fluorophore materials for metal ion analysis. Here, highly passivated green phosphorous and nitrogen co-doped carbon quantum dots (C-dots) were prepared using low-temperature carbonization route. Strong green fluorescence emission around 490nm and excitation wavelength independent C-dots were obtained. Morphological, surface, and optical properties of the C-dots were characterized. Fluorescence emission of C-dots was quenched selectively by copper ions and restored by adding copper chelators, such as EDTA and sulfide ions. Thus, C-dots were successfully used for direct determination of copper ions. Detection limit as low as 1.5nM (s/n = 3) was achieved for copper ions. Such a low detection limit is very significant for metal analysis using our proposed facile method and low-cost substrates. Experimental results showed that the prepared C-dots demonstrated high sensitivity and selectivity for Cu2+ ion detection and the method is robust and rugged. Graphical abstract ᅟ.

Phase diagrams of the MgSO4-Al2(SO4)3-(NH4)2SO4-H2O system at 25 and 55 °C and their application in mineral carbonation

A route for the indirect mineral carbonation of blast furnace slag using (NH4)2SO4 as a recyclable reagent has recently been proposed. The main challenges associated with this route are reducing its energy consumption and improving its cost-efficiency. In this process, the recycling of (NH4)2SO4 by evaporation of the carbonation liquor make up a large proportion of the total energy consumption. Thus, controlling the water dosage during leaching of the products of roasting the blast furnace slag with (NH4)2SO4, which are mainly various sulfates of Ca, Mg, Al, and NH4+, is of great importance. In this study, the solubilities of the quaternary MgSO4-Al2(SO4)3-(NH4)2SO4-H2O system were measured at 25 and 55 °C using the isothermal method. The resulting phase diagrams are instructive for determining the lowest liquid-to-solid ratio required for leaching and for recovery of the value-added byproduct, ammonium alum, from the leachate. The results show that the crystalline region of NH4Al(SO4)2·12H2O dominates in the phase diagrams, indicating that it is easily crystallized out and that the use of this route for the separation of aluminum as ammonium alum is feasible. The liquid-to-solid ratios for the leaching unit were calculated to be 4.55 and 1.97 mL/g at 25 and 55 °C, respectively. The liquid-to-solid ratio at 55 °C was reduced by 56.7% compared to the ratio at 25 °C.

Dimethyl Carbonate as a Promising Oxygenated Fuel for Combustion: A Review

Energy shortage and environmental problems are two dominant subjects. Dimethyl carbonate (DMC) is one of the oxygenated fuels with increasing interest as the alternative to diesel fuel or additive for conventional hydrocarbon fuels. In the last decade, comprehensive studies on DMC have been carried out in terms of synthesis, use, and oxidation and combustion mechanism. DMC synthesis from greenhouse gas such as carbon dioxide can achieve the carbon circulation between air and fuel. Ethylene carbonate route is one of the most promising ways to utilize carbon dioxide and synthesize DMC in terms of particle efficiency, energy consumption per one unit of product, and net carbon dioxide emission. In addition, the results show that pure DMC in compression ignition (CI) engines or DMC addition in diesel/gasoline could decrease emissions significantly. Moreover, DMC pyrolysis form carbon dioxide before carbon monoxide which is different from other oxygenated fuels. However, DMC can produce formaldehyde during oxidation process in high concentration, which is harmful to the environment and human health as well. The present DMC kinetic model needs to update the major reactions constant through recognizing the initial decomposition routes and low-temperature oxidation. In addition, further studies on the DMC/hydrocarbon fuels mixtures for the interaction chemistry are needed.