Carbonation Reaction Rate Research Articles

Exploring carbon dioxide sequestration in desalination reject brine via NaOH reaction: A kinetics study

Seawater desalination is one of the most sustainable means of water supply in arid and semi-arid regions. Despite its undeniable potential to meet the global water demands, there are several environmental impacts associated with its operation, including the generation of reject brine and the emission of considerable amounts of CO2. Recently, the mineralization of carbon dioxide using desalination reject brine has emerged as a potential solution for simultaneous brine management and CO2 sequestration. In this study, the reaction kinetics of desalination reject brine with CO2 in the presence of NaOH are evaluated. The effect of various operating parameters, such as the temperature, CO2 concentration, NaOH dosage, brine salinity, CO2 flowrates and inert particles volume percent were investigated by varying them within the range of 15–55 °C, 3–20 %, 6–16 g/L, 5–72 g/L, 1–5 L/min and 0–20 %, respectively. The experimental data showed that the overall rate of CO2 conversion is equal to the sum of the rates observed for Ca2+ and Mg2+ carbonation reactions and increases proportionally with the increase in CO2 concentration. The addition of NaOH improved the Ca2+ carbonation reaction rate but had no effect on Mg2+ carbonation reactions within the investigated reaction conditions. Interestingly, increasing brine salinity had a negative effect on the reaction rate, while the change in temperature and inert particles had minimal effect on the overall reaction rate. Analysis of the solid products showed that Hydromagnesite and Calcite were the two major products obtained. Finally, experimental data were used to develop a rate model representing the CO2-Brine-NaOH system. The developed model will assist in successfully predicting the performance of the process and pave the way for efficient brine management and CO2 sequestration.

Unveiling the carbonation behavior of T-C3S and M-C3S: A comparative investigation

Numerous studies have investigated the carbonation process of tricalcium silicate (C3S). However, research on the carbonation of its different crystal forms remains relatively limited. This study explored the effects of accelerated carbonation on the performance and microstructure of T-C3S and M-C3S. The findings indicated that both T-C3S and M-C3S exhibited a rapid carbonation reaction rate during the initial 12 h, which subsequently declined gradually. The carbonation products of T-C3S and M-C3S primarily consisted of calcite, with T-C3S also containing a proportion of aragonite calcium carbonate. The decomposition peak temperature of calcium carbonate weight loss increased with prolonged carbonation time for both C3S crystal forms. Prismatic or cubic morphology calcite formed in T-C3S and M-C3S during the initial carbonation stages, leading to a denser microstructure. As the carbonation duration increased, the particle size of calcite also grew, displaying a more irregular morphology. Furthermore, needle-like or rod-like aragonite calcium carbonate was observed in T-C3S. T-C3S exhibited superior compressive strength compared to M-C3S at all stages of carbonation. Additionally, a relationship was established between compressive strength, calcium carbonate content, and CO2 uptake. This study provided evidence that the crystal structure of C3S not only influenced the rate of the carbonation reaction but also impacted the type and morphology of calcium carbonate products and the development of compressive strength.

Wet combustion synthesis of new thermochemical energy-storage materials based on carbide slag/magnesium oxide using citric acid

In this study, industrial solid waste carbide slag (as the calcium source) is modified using the critic acid (as the fuel) combustion mixing method to prepare a new type of magnesium oxide–doped energy-storage material. The experimental results show that the prepared H2O-CM-100 material doped with magnesium oxide exhibits good energy-storage performance and cycling stability during calcium cycling. After 20 energy-storage cycles, the energy-storage density and effective conversion rate remained stable at 1800 kJ/kg and 0.57, respectively. These values exceed the reported energy-storage densities and effective conversion rates of carbide slag energy-storage materials modified using the dry physical mixing method employed in previous studies. In addition, the carbonation kinetics results indicate that the doping of magnesium oxide effectively improves the carbonation reaction rate of carbide slag materials in the carbide slag cycle. In summary, magnesium oxide doping can not only improve the sintering of calcium oxide particles in carbide slag materials but also effectively enhance the energy-storage performance and carbonation reaction rate of carbide slag during carbide slag cycles. Thus, this study proposes a novel method for the efficient resource utilization of carbide slag and development of energy-storage materials.

Unveiling the Carbonation Behavior and Microstructural Changes of Magnesium Slag at 0 ℃

Magnesium slag (MS) is an industrial byproduct with high CO2 sequestration potential. This study investigates the carbonation behavior and microstructural changes of MS during wet carbonation at 0 °C. XRD, TG, FTIR, SEM, and BET techniques were used to characterize the phase composition, microstructure, and porosity of MS samples carbonated for different durations. The results showed that the main carbonation products were calcite, vaterite, and highly polymerized silica gel, with particle sizes around 1 μm. The low-temperature environment retarded the carbonation reaction rate and affected the morphology and crystallization of calcium carbonate. After 480 min of carbonation, the specific surface area and porosity of MS increased substantially by 740% and 144.6%, respectively, indicating improved reactivity. The microstructure of carbonated MS became denser with calcite particles surrounded by silica gel. This study demonstrates that wet carbonation of MS at 0 °C significantly enhances its properties, creating an ultrafine supplementary cementitious material with considerable CO2 sequestration capacity.

Multiscale performance and environmental impact assessment of slag and Portland blended cement for optimum carbonation curing

This article presents an investigation into the potential use of ground granulated blast-furnace slag (addressed as Slag cement or ‘SC’) as a replacement to Ordinary Portland Cement (OPC) in hybrid (carbonation and hydration) cured cement-based materials. To investigate the effects of carbonation on mechanical performances and microstructures, 0 %–100 % OPC was replaced with slag cement (SC). Thermogravimetric analysis (TGA) and Fourier transformed infrared (FTIR) spectra were utilized to investigate the carbonation reaction extent, rate, and microstructural phase formations. Slag cement was found to improve the efficiency and rate of carbonation. This study revealed that a minimum of 72 h of carbonation in a CO2-containing environment yields better mechanical performance compared to the traditional curing method. Specifically, the incorporation of 72 h of carbonation curing was observed to increase the strength of concrete up to 30 % after 28 days of total curing duration (carbonation and hydration). The chloride permeability of the carbonation cured samples was observed to reduce by 80 % due to the addition of SC. Finally, it was observed that, the carbonated concrete sample with slag has nearly 60 % lower global warming potential compared to the carbonated and non-carbonated concrete sample with 100 % OPC binder.

Effect of compression molding of CaCO3 powder on the kinetics of CO2 capture towards sustainable CO2 capture and sequestration cycle.

Reducing CO2 emissions from industrial sectors and motor vehicles is currently receiving much attention. There are different strategies for CO2 capture, one of which is using calcium oxide (CaO). In our proposed carbon dioxide cycle, limestone is first calcined to get CaO, which is then used to capture CO2 by converting it to CaCO3. Next, the released CO2 could be converted to different organic matter by different sequestration techniques. For this purpose, CaCO3 discs have been prepared by compression molding to investigate the effect of sintering temperature on the mechanical and chemical properties of CaO carbonation reaction. The aim of this work is to fill the knowledge gap for the effect of the contact profile between CO2 gas and CaO disc, particularly the effect of reducing the void fraction of CaO on the rate of carbonation reaction. It was found that the flexural strength of the CaO discs was influenced by several factors, such as the calcination temperature, duration of calcination, and pressing pressure. The carbonation step indicated that both CO2 and H2O are reacting with CaO simultaneously and progressively, with the progressive reaction of H2O and CO2 being a favorable route. The carbonation process happens as a surface reaction-controlled process followed by a slower internal diffusion-controlled process. Additionally, a kinetic study of the competing reactions indicated that two factors are controlling the process: diffusion of gases through the pores and then the reaction rate. Furthermore, our data showed that the CO2 uptake rate was 1352.34mg/g CaO, indicating that 566.34mg of CO2 was adsorbed inside the pores of the CaO disc. Based on these results, we propose a new mechanism of the sequence of the competing reactions. In summary, the CaO discs revealed a significant removal of CO2 from stack gases, which will be suitable for removing CO2 from exhaust gases generated by industrial processes and other sources of emissions such as vehicles and ships.

Intensified mineral carbonation of natural Canadian silicates using simultaneous ball milling

Carbon concentrations in the atmosphere are increasing yearly, making it the primary contributor to climate change. To reduce CO2 emissions, various strategies and technologies have been implemented. Mineral carbonation is an effective technology for mitigating climate change. Despite its efficiency, the slow pace of mineral carbonation poses a challenge when paired with the rate of emissions from point sources such as industrial facilities. To address this, the research focuses on studying mineral carbonation under mechanically and chemically intensified conditions. The project investigated the simultaneous ball milling and carbonation of Ca- and Mg-hydroxides and natural Canadian silicates (kimberlite and wollastonite) using a Retsch GrindControl jar reactor. Three additives (NaOH, MgCl2, and CH3CH2OH) were examined for their potential to enhance carbonation efficiency and reaction rate and to control carbonate mineralogy. In-situ temperature measurement enabled tracking milling and exothermic carbonation heat generation. Characterization techniques to gain insight into the reaction and products included pH testing, calcimetry, XRD analysis, and SEM imaging. For most feedstocks, water as the main solvent led to higher carbonation and precipitating of different carbonates (hydromagnesite, aragonite, calcite), while for kimberlite, using NaOH's pH buffering led to better performance. Ball-milling was shown to assist in intensifying mineral carbonation reactions by integrating milling and reaction unit processes into one, whereby the reactive surface area is increased at the right time (i.e., as passivation is about to initiate). Results indicate up to 5 and 15.7 times net increase in the carbonation content of studied silicates and hydroxides, respectively. Still, as planetary ball mills are designed primarily for comminution rather than multi-phase (gas-liquid-solid) mixing, further research is needed to identify if the gas-paste mixing efficiency achieved could be a limiting factor calling for other types of milling equipment for this application.

Experimental study on the activation of coal gasification fly ash from industrial CFB gasifiers

Coal gasification fly ash (CGFA) is an industrial solid waste from the coal circulating fluidized bed (CFB) gasification process, and it needs to be effectively disposed to achieve sustainable development of the environment. To realize the application of CGFA as a precursor of porous carbon materials, the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed. Then, the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor. Finally, the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig, and its advantages are highlighted. The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%, an ultrafine particle size (d50: 16.3–26.1 μm), and a relatively developed pore structure (specific surface area SSA: 139.29–551.97 m2·g−1). The proportion of micropores in CGFA increases gradually with the coal rank. Steam activation experiments show that the pore development of CGFA mainly includes three stages: initial pore development, dynamic equilibrium between micropores and mesopores and pore collapse. The SSA of lignite fly ash (LFA), subbituminous fly ash (SBFA) and anthracite fly ash (AFA) is maximally increased by 105%, 13% and 72% after steam activation; the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA > LFA > AFA. As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19, the carbon conversion ratio increases from 14.4% to 26.8% and the cold gas efficiency increases from 6.8% to 10.2%. The SSA of LFA increases by up to 53.9% during the fluidization activation process, which is mainly due to the mesoporous development. Relative to steam activation in a tube furnace reactor, fluidization activation takes an extremely short time (seconds) to achieve the same activation effect. It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35% to create pores in the initial development stage.

Effects of density and heat treatment of C/C preforms on microstructure and mechanical properties of C/C–SiC composites

AbstractTwill multidirectional carbon‐fiber‐reinforced carbon and silicon carbide composites (i.e., C/C–SiC) were prepared via chemical vapor infiltration combined with reactive melt infiltration process. The effect of heat treatment (HT) on the microstructure and mechanical properties of C/C–SiC composites obtained by C/C preforms with different densities was thoroughly investigated. The results show that as the bulk density of C/C preforms increases, the thickness of the pyrolytic carbon (PyC) layer increases and open pore size distribution narrows, making the bulk density and residual silicon content of C/C–SiC composites decrease. Moreover, the flexural strength and tensile strength of the C/C–SiC composites were improved, which can be attributed to the increased thickness of the PyC layer. The compressive strength reduces due to the decrease of the ceramic phase content. HT improves the graphitization degree of PyC, which reduces the silicon–carbon reaction rate and thereby the content of the SiC phase. HT induces microcracks and porosity but not obviously affects the mechanical properties of C/C–SiC composites. However, the negative impact of HT can be compensated by the increased density of the C/C preforms.

Kinetic investigation and numerical modelling of CaCO3/Al2O3 reactor for high-temperature thermal energy storage application

This study conducts kinetic analyses of the carbonation reaction of CaCO3 (doped with Al2O3) as well as parametric analyses of the performance of a thermochemical reactor, which can act as a thermal battery. Kinetic measurements of CO2 release and absorption were carried out using thermogravimetric analysis (TGA) at 815, 830 and 845 °C on a CaCO3/Al2O3 sample that had been previously cycled over 500 times. The rapid reaction kinetics revealed that the Avrami nucleation growth model with exponent 3 fits well to explain the carbonation reaction. The numerical study considered a cylindrical reactor with a height and diameter of 100 mm. According to numerical analysis, at an applied CO2 pressure of 1 bar, increasing the thermal conductivity of the reactor bed from 1.33 to 5 W/m.K increases the rate of carbonation reaction by 74%. When the applied CO2 pressure is increased from 1 to 2 bar, the performance of the reactor bed with thermal conductivity of 1.33 W/m.K improves by 42%; however, when the applied CO2 pressure is increased from 2 to 3 bar, the performance improves by only 18%. Additionally, when the boundary temperature of the reactor was lowered by 30 °C, performance was enhanced by 43% at an applied CO2 pressure of 1 bar. This study also examined the effect of using a graphite fin as a heat extraction system. The graphite fin allowed for more rapid heat extraction and increased the carbonation reaction by 44% in the reactor bed with poor thermal conductivity (1.33 W/m.K) but had no effect in the reactor with modest thermal conductivity of (5 W/m.K) due to its ability to already transfer heat effectively to the reactor shell.

Mineral carbonation of ultramafic tailings: A review of reaction mechanisms and kinetics, industry case studies, and modelling

Reduction of greenhouse gas emissions is becoming a greater priority in the mining industry due to increasing social pressures, government incentives, and its consideration in companies stock evaluation. Carbon capture and sequestration in ultramafic tailings (mineral carbonation) is one technology companies can use to offset their carbon emissions. Mineral carbonation refers to the spontaneous reaction of carbon dioxide with divalent metal minerals, which safely and permanently stores carbon dioxide as a carbonate sediment. Carbon sequestration can occur passively in ultramafic mine tailings storage facilities or under optimized conditions in process designs. This review discusses the literature on mineral carbonation reaction mechanisms, candidate minerals, kinetic parameters, potential methods to accelerate mineral carbonation, examples of industry mineral carbonation, and mine-scale mineral carbonation modelling. • Mineral carbonation reaction rate limiting mechanisms and thermoynamics. • Effect of water saturation, temperature, mineralogy, depth, pH, CO 2 and grain size. • Technologies to improve CO 2 sequestration in ultramafic tailings. • Reactive transport modelling of mineral carbonation in ultramafic tailings.

Properties investigation of recycled aggregates and concrete modified by accelerated carbonation through increased temperature

Carbonation can modify waste concrete aggregate and sequester CO2; however, the slow reaction speed in a room environment limits its industrial application. In this study, the carbonation reaction of recycled coarse aggregates were accelerated at 70 °C. The physical properties of the recycled coarse aggregate before and after accelerated carbonation treatment and the mechanical properties of recycled concrete were tested and evaluated. Based on the results, an increased carbonation temperature can accelerate the carbonation reaction rate of the recycled concrete aggregate. The calcium hydroxide contained was fully carbonated in the first 12 h. Carbonation modification reduced the water absorption rate to 23.6% and the crushing value to 36.2%. Moreover, the mechanical performance of recycled concrete mixed with carbonation-modified aggregates was evaluated through a uniaxial stress–strain constitutive test. The 28 d compressive strength showed a 14.2% increase at 100% substitution of recycled modified aggregates relative to recycled aggregates. The elastic modulus and brittleness of the recycled concrete were also improved.

Effect of Graphene Nanoplatelet on the Carbonation Depth of Concrete under Changing Climate Conditions

Climate change has been unprecedented in the past decades or even thousands of years, which has had an adverse impact on the mechanical properties of concrete structures. Many researchers have begun to study new concrete materials. Graphene nanoplatelet (GNP) is an attractive nanomaterial that can change the crystal structure of concrete and improve durability. The aim of the present study was to investigate the effect of GNP (0.05%wt) on the carbonation depth of concrete under simulated changing climate conditions (varying temperature, relative humidity, and carbon dioxide (CO2) concentration), and compare it with ordinary concrete. When the concentration of CO2 is variable, the carbonation depth of graphene concrete is 10% to 20% lower than that of ordinary concrete. When the temperature is lower than 33 °C, the carbonation depth of graphene concrete is less than that of the control sample; however, above 33 °C, the thermal conductivity of GNP increases the carbonation reaction rate of concrete. When the humidity is a variable, the carbonation depth of graphene concrete is less than 15% to 30% of ordinary concrete, and when the humidity is higher than 78%, the difference in the carbonation depth between the ordinary concrete and the graphene concrete decreases gradually. The overall results indicated that GNP has a favorable effect on anti-carbonation performance under changing climate conditions.

Real-time investigation of the CO2 mineral carbonation reaction rate through direct aqueous route using semi-dry desulfurization slag

Mineral carbonation via alkaline solid wastes is considered an effective approach to capture and store flue gas CO2 from industries and power plants. In this study, direct mineral carbonation of semi-dry desulfurization slag (SDe-S) through an aqueous route was investigated with an online carbonation setup to measure the amount of CO2 consumed by Ca(OH)2 at atmospheric pressure in a slurry reactor. The carbonated solid and liquid products were characterized by X-ray fluorescence, X-ray diffraction and field emission scanning electron microscopy with energy dispersive X-ray spectrometry. The results show that carbonation caused the sample particle size to become more uniform. A large amount of Ca2+ was dissolved in the waste solution which could be recycled, thus increasing the utilization rate of Ca2+. The CO2 carbonation efficiency and absorption rate of SDe-S could be improved by controlling the reaction operation parameters. The optimal reaction conditions of this reactor were 100 g/L, 60 °C, 400 rpm and 300 mL/min, and the optimal reaction termination time was limited to 249 min to ensure a CO2 absorption efficiency of higher than 90 %. The carbonation process was controlled first by the film diffusion of liquid CO2, then by the chemical reaction, then by the film diffusion of liquid Ca(OH)2, and finally by the diffusion of the product layer. Experimental simulation suggests that the semi-dry desulfurization ash could achieve high CO2 absorption efficiency at atmospheric pressure and low temperature without producing any waste liquid. That is, it pretty economical and environmentally friendly.

Effects of iron/silicon/magnesium/aluminum on CaO carbonation of CO2 in steel slag-based building materials during carbonation curing

Carbonation curing can enhance the mechanical properties of steel slag-based building materials and consume large amounts of CO2, making it a widely process. Due to the complexity of steel slag, in addition to CaO, other concomitant metallic/nonmetallic elements, such as Fe, Si, Mg and Al also have a certain influence on carbonation reaction. In this study, Fe2O3, Fe3O4, SiO2, MgO and Al2O3 was added to CaO to form a binary system according to the chemical composition of real steel slag. The influences of these oxides on the carbonation rate and CaO carbonation efficiency were investigated, respectively. The results showed that compared with pure CaO, the rates of carbonation reaction of CaO + Fe2O3, CaO + Fe3O4, CaO + SiO2, CaO + MgO and CaO + Al2O3 were increased by 5.5%, 13.2%, 13.2%, 6.9% and 8.5%, respectively. The carbonation efficiency of CaO in CaO + Fe2O3, CaO + Fe3O4, CaO + MgO, CaO + Al2O3 increased by 3.6%, 4.3%, 10.1%, and 1.2%, respectively. Synergistic effect was recognized between CaO and Fe2O3, Fe3O4, MgO and Al2O3, respectively. The carbonation efficiency of CaO in CaO + SiO2 decreased by 2.4%. One reason should be the carbonation products, which exhibited ectopic dispersion and covered the surfaces of Fe2O3, Fe3O4, MgO and Al2O3, which effectively helped to avoid in-situ aggregation and thus covered the surfaces of the CaO particles. This improved the carbonation reaction rate and efficiency. Another reason could be the alkaline oxides, such as Fe2O3, Fe3O4 and MgO, and amphoteric oxides, such as Al2O3, stimulated the carbonation reaction of CaO and CO2, while acid oxides, such as SiO2, inhibited the carbonation reaction.

Effect of water-to-cement ratio induced hydration on the accelerated carbonation of cement pastes.

Recently, the use of accelerated carbonation curing has attracted wide attention as a promising method to reduce carbon dioxide (CO2) emission and improve the mechanical properties of cement-based materials. However, the diffusion mechanism of CO2 in the matrix and the content of hydration products are the key factors that restrict the carbonation reaction rate. To understand the combined behavior of hydration and carbonation reactions, this paper investigates the influence of cement hydration induced by water-to-cement ratio (w/c) (ranging from 0.25 to 0.45) on microstructure and microhardness properties of cement paste. The experimental results demonstrated that carbonation only occurred at the surface layer of cement paste samples and carbonation efficiency was significantly influenced by greater hydration due to higher w/c. The carbonation depth of the sample with 0.45 w/c was about 6 times higher than that of sample with 0.25 w/c after 28 days of CO2 curing. XRD results revealed that calcite-type calcium carbonate is the main carbonation product and consumption of clinker phases (C2S and C3S) during the hydration enhanced the calcite precipitation in the pores of the surface layer. According to FTIR, with increasing w/c, the position of Si-O-Si stretching bond of the carbonated surface changed from Q2 to Q3, confirming the formation of amorphous silica-rich gel, along with the appearance of CO32- bonds related to calcite. In overall, the micro-mechanical analysis in this study showed that the carbonation significantly improved the surface microhardness of cement paste samples, while the refinement of capillary pores due to carbonation also decreased the negative impact of large pores formed in the matrix of cement paste prepared with high w/c.

Catalyzed Sintering of Regenerated CaO Induced by Partition Evolution of Calcium Carbonate

AbstractThe partition evolution of parent calcium carbonate (CaCO3) and its effect on the catalyzed sintering of regenerated CaO during calcium looping cycles were investigated. The carbonation reaction rate has a heterogeneous distribution either in the particle radial direction or in the same layer, which causes the partition structure evolution of CaCO3 from overall dense structure to region partition structure. Both the residual and sintering of regenerated CaO were enhanced with the structural evolution of carbonate precursor. Within the first five cycles, an initial structural division of the CaCO3 matrix occurs accompanied by a sharp decrease in the number of mesopores, indicating a dependence of the CO2 capture ability on the structure evolution of the sorbent skeletal.

Carbonation Reaction of Lithium Hydroxide during Low Temperature Thermal Energy Storage Process

In order to apply lithium hydroxide (LiOH) as a low temperature chemical heat storage material, the carbonation reaction of LiOH and the prevention method are focused in this research. The carbonation of raw LiOH at storage and hydration condition is experimentally investigated. The results show that the carbonation reaction of LiOH with carbon dioxide (CO₂) is confirmed during the hydration reaction. The carbonation of LiOH can be easily carried out with CO₂ at room temperature and humidity. LiOH can be carbonated at a humidity range of 10% to 20%, a normal humidity region that air can easily be reached. Furthermore, the carbonation reaction rate has not nearly affected by the increase of reaction temperature. An improved storage method by storing LiOH at a low humidity less than 1.0% can be effectively prevented the carbonation of LiOH. The hydration reaction ratio of LiOH at the improved storage method shows a better result compared to the ordinary storage method. Therefore, the humidity should be carefully controlled during the storage of LiOH before hydration and dehydration reaction when apply LiOH as a low heat chemical storage material.

CO2 storage and conversion to CH4 by wet mechanochemical activation of olivine at room temperature

Wet mechanochemical processing of olivine under a CO2 atmosphere promotes the CO2 sequestration in the form of MgCO3 and the CO2 reduction to CH4 at room temperature. The effects of milling time and CO2 pressure on the CO2 storage and CO2 reduction were evaluated at lab-scale. Wet mechanochemical introduces progressively significant morphological, structural, microstructural, and textural changes in olivine for prolonged milling times, inducing fast carbonation reaction after 15 min of ball milling. Long milling times stimulate the CO2 conversion to CH4 and decrease the carbonation reaction rate, because both reactions occurred simultaneously. The CO2 sequestrated as MgCO3 is about 4.83 wt% and 6.81 wt% for 1.0 atm of CO2 after 120 min and 180 min of milling using different CO2 charge strategy. The amount of CO2 reduced to CH4 was 24 and 33 mmoles/kg of olivine after 120 min with 1.0 and 1.5 atm of CO2, respectively. Wet milling of olivine in CO2 atmosphere is a technique with potential for large-scale carbon mineralization.

Highly efficient removal of amoxicillin from water by three-dimensional electrode system within granular activated carbon as particle electrode

Amoxicillin (AMX) is a widely used broad-spectrum antibiotic. In this study, a three-dimensional electrode system (3DES) was constructed with granular activated carbon (GAC) packed between the anode and cathode electrodes to degrade AMX. Under optimal conditions of 3DES (current density of 5 mA/cm2, 17 mM NaCl as the electrolyte, an initial pH of 5.56, and a GAC-quartz sand volume ratio of 9:1), the removal efficiency of AMX reached 98.98 % after 2 h of treatment. It was also shown that the total organic carbon (TOC) removal efficiency (R) and reaction rate constant (k) of 3DES were 47.6 % and 0.22 h−1, respectively, much higher than the sum of the two-dimensional electrode system (2DES) and adsorption process (30.7 % and 0.12 h−1). Thus, there existed the synergy between electrolysis and adsorption in 3DES, which enhanced the TOC removal efficiency and removal rate by up to 35.5 % and 46.8 %, respectively. Electrochemical characterization was explored using an electrochemical workstation. It demonstrated that GAC played an important role in reducing the mass transfer resistance, and the mass transfer rate of 3DES was 2.24 times that of the 2DES. It was also deduced that AMX adsorbed on the surface of GAC directly participated in the electrochemical oxidation to achieve the in-situ regeneration of activated carbon. The results of Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) of GAC verified it again. In summary, 3DES has good electrochemical performance, and it is an efficient, cost-effective, and environmentally friendly system for AMX degradation.