Sorption Performance Research Articles

Research Experiences via Integrating Simulations and Experiments (REVISE): A Model Collaborative Research Project for Undergraduate Students in CO2 Sorbent Design.

Undergraduate research experiences are an instrumental component of student development, increasing conceptual understanding, promoting inquiry-based learning, and guiding potential career aspirations. Moving one step further, as research continues to become more interdisciplinary, there exists potential to accelerate student growth by granting additional perspectives through collaborative research. This study demonstrates the utilization of a model collaborative research project, specifically investigating the development of sorbent technologies for efficient CO2 capture, which is an important research area for improving environmental sustainability. A model CO2 sorbent system of heteroatom-doped porous carbon is utilized to enable students to gain knowledge of adsorption processes, through combined experimental and computational investigations and learnings. A particular emphasis is placed on creating interdisciplinary learning experiences, exemplified by using density functional theory (DFT) to understand molecular interactions between doped carbon surfaces and CO2 molecules as well as explain underlying physical mechanisms that govern experimental results. The experimental observations about CO2 sorption performance of doped ordered mesoporous carbons (OMCs) can be correlated with simulation results, which can explain how the presence of heteroatom functional groups impact the ability of porous carbon to selectively adsorb CO2 molecules. Through an inquiry-focused approach, students were observed to couple interdisciplinary results to construct holistic explanations, while developing skills in independent research and scientific communications. This collaborative research project allows students to obtain a deeper understanding of sustainability challenges, cultivate confidence in independent research, prepare for future career paths, and most importantly, be exposed to strategies employing interdisciplinary research approaches to address scientific challenges.

Preparation of ultrathin and highly loaded MOF mixed matrix membranes with honeycomb-like structure via ordered array self-assembly

Metal-organic frameworks mixed matrix membranes (MOF MMMs) have many advantages such as structural diversity and easily large-scale preparation, but current MOF MMMs are difficult to meet the economic and technical requirements of membrane industrial applications, mainly because of the limitation of MOF loadings. Here, a type of polymer-templated MOFs (PMOFs) have been prepared, and then used to prepare the honeycomb-like mixed matrix membrane with highest MOF loading of 93.5 % by using polymer-induced ordered array self-assembly. Polymer-templating endowed MOFs with excellent self-assembly ability due to the rich functional groups of grafted polymer fragments, promoting the formation of honeycomb arrangement structure. The gas sorption, material characterizations and separation performance revealed that the PMOFs provided the resulting honeycomb-like MMMs with favorable CH4 sorption and ultrafast diffusion pathways by forming unimpeded transfer channels. Herein, the prepared honeycomb-like PCuBTC membranes with thickness of about 46.1 nm exhibited exceptionally high pure CH4 permeance of 1025 GPU and moderated ideal CH4/N2 selectivity of 6.57.

Preparation and thermal properties of zeolite/MgSO4 composite sorption material for heat storage

Thermochemical sorption heat storage based on salt hydrates offers the potential advantages such as high energy density, negligible heat loss, small volume change and flexible working modes. Magnesium sulphate (MgSO4) is a high energy density hydrated salt available for the thermochemical sorption heat storage. In this work, different types of zeolites (including 3A, 5A and 13X zeolites) have been selected as mass-transfer-enhancing and structural stabilizing materials, and a series of zeolite/MgSO4 composites have been fabricated. To investigate the thermal energy storage performance of zeolite/MgSO4 composites, the properties of the composites, such as micro-morphology, pore structure, chemical composition and sorption-desorption behavior, have been characterized and analyzed. Results indicated that the mass transfer performance of the composite materials is significantly better than that of the pure zeolites. As the mass fraction of MgSO4 in the composite sorbents increases, the specific surface area and porosity of the composite sorbent decreases, and the sorption performance has been enhanced. Compared with 3A zeolite-based and 5A zeolite-based composites, 13X zeolite/MgSO4 composite materials show the best heat storage performance. At the condition of 25 °C and 60% RH, the 13XM20 has the highest sorption capacity of 0.21 g/g, which is 24% higher than that of pure zeolite 13X. Accordingly, the maximum heat storage density is 438.4 kJ/kg, which exhibits the superior heat storage performance among of the hydrated salt sorbents. The potential of 13X zeolite/MgSO4 as sorption heat storage material in efficient utilization of solar heat and low-grade industrial waste heat has been revealed.

Preparation of Mg@MIL-101(Fe)/NH2-MIL-125(Ti) bis-MIL composites and their sorption performance towards Pb(II) from aqueous solution

MIL-101(Fe) has received more and more attention in wastewater treatment, and how to further improve its stability and sorption capacity has become a research focus. In this study, metal Mg was used to dope MIL-101(Fe) to construct Mg@MIL-101(Fe) with bimetallic sites, which was then mixed with NH2-MIL-125(Ti) to successfully fabricate Mg@MIL-101(Fe)/NH2-MIL-125(Ti) (MOM) bis-MIL composites. MOM not only contains a large number of sorption sites but also exhibits excellent stability and reusability, realizing efficient sorption of Pb(II) from aqueous solution. In addition, the sorption performance and mechanism of Pb(II) on MOM were investigated by the characterizations of SEM, BET, TG, XRD, FTIR and XPS, as well as the kinetic and thermodynamic analyses. The sorption of Pb(II) on MOM is in accordance with the Langmuir isothermal model and pseudo-second-order kinetic model. The maximum sorption capacity of Pb(II) on MOM derived from the Langmuir model fitting is 320.941 mg·g−1. The sorption of Pb(II) on MOM is strongly affected by pH, but not by ionic strength, which indicates that MOM has good resistance to salt interferences. The strong complexation of carboxyl, hydroxyl and amino functional groups with Pb(II) is the main sorption mechanism of Pb(II) on MOM, and electrostatic interaction and ion exchange also contribute to the sorption. In conclusion, MOM has strong practical application prospects in the treatment of Pb(II)-containing wastewater.

Sorption Behaviors of Amorphous Titanium Phosphate Towards Neodymium and Dysprosium

Due to the limited supply of critical metals, their recovery from alternative sources has become a very important issue. In particular, end-of-life magnets contain significant amounts of neodymium (Nd) and dysprosium (Dy) ions and are considered secondary sources. The present study focused on the sorption and separation performance of titanium phosphate for Nd and Dy ions in an aqueous solution. In this regard, amorphous titanium phosphate (am‐TiP) was prepared via one‐step precipitation. XRD, SEM‐EDS, FTIR, and BET analysis were utilized to enlighten the morphological, structural, and surface properties of am‐TiP. The uptake of Nd3+ and Dy3+ ions was examined individually and in multiple element solutions depending on solution pH, contact time, metal concentration, and the presence of Co2+ ions. The maximum uptake capacity was 40.16 mg/g at pH 6 for Nd3+ and 26.95 mg/g at pH 4 for Dy3+. Am‐TiP has been observed to exhibit selectivity towards Nd3+ and Dy3+ ions in solutions containing Co2+ ions. The highest desorption yields obtained for Nd3+ and Dy3+ using 1.0 mol/L HCl were 95.2% and 97.4%, respectively.

Electrospun polymeric nanohybrids with outstanding pollutants adsorption and electroactivity for water treatment and sensing devices

Graphene oxide (GO) and carbon nanotubes (CNTs) were loaded at different mutual ratios into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) matrix and electrospun to construct mats that were assessed as smart sorbents for decontaminating water from methylene blue (MB) pollutant, while ensuring the additional possibility of detecting the dye amounts. The results revealed that sorption capacity enhances upon increasing GO content, which is beneficial to wettability and active area. Equilibrium adsorption of these materials is precisely predicted by the Langmuir isotherm model and the maximum capacities herein achieved, ranging from 120 to 555 mg/g depending on the formulation, are higher than those reported for similar systems. The evolution of the structure and properties of such materials as a function of dye adsorption was studied. The results reveal that MB molecules prompted the increase of electrical conductivity of the samples in a dose-dependent manner. Mats containing solely CNTs, while displaying the worst sorption performance, showed the highest electrical performances, displaying interesting changes in their electrical response as a function of the dye amount adsorbed, with a linear response and high sensitivity (309.4 µS cm−1 mg−1) in the range 0–235 µg of dye adsorbed. Beyond the possibility to monitor the presence of small amounts of MB in contaminated water and the saturation state of sorbents, this feature could even be exploited to transform waste sorbents into high-added value products, including flexible sensors for detecting low values of pressure, human motion, and so on.Graphical Multifunctional materials for dye absorption and detection, pressure sensing, fabricated by integrating GO and CNTs into PVDF-HFP matrix via electrospinning.

Magnetic luffa/graphene/CuFe2O4 sponge for efficient oil/water separation

In this study, a novel magnetic composite material comprising luffa sponge derived graphene aerogel embedded with hollow CuFe2O4 nanospheres (LGN) is successfully synthesised for the first time by a clean and low-cost one-step solvothermal electrostatic co-assembly method. The resultant LGN aerogel exhibits superhydrophobic and superoleophilic properties with the water and oil contact angles of 162.1° and 0°, respectively, along with magnetic properties characterized by the saturation magnetization of 51.6 emu/g, and a large specific surface area of 218.8 m2/g. The saturation sorption capacity of LGN for organic solvents/oil is found to be in the range of 47.6–86.8 g/g, exhibiting an excellent oil/water emulsion separation ability. Through the capillary action, oil and organic solvents spontaneously penetrate into the interior of the aerogel, while the superhydrophobic surface prevents water from entering, thereby enabling the separation of oil and water. These characteristics enable the real-time sorption of organic pollutants from water, with the capability of exhausted sorbent being regenerated. Notably, even after 20 sorption-volatilisation cycles, the saturated sorption capacity of LGN remains high at the 92.2 % of the initial value, demonstrating a remarkable recycling performance. In addition, LGN can exhibit an oriented sorption performance by controlling the applied magnetic field, enabling sorbent recycling even under extreme environmental conditions. Such an effective strategy offers a new route to high value utilisation of biomass waste with significant potential in the field of oil spill treatment.

Synthesis and Sorption Profiles of Graphene‐Decorated Silane‐Modified Layered Clays for As(V) Removal: A Quantitative Assessment and Mechanistic Insights

AbstractA novel adsorbent material, graphene decorated silane modified layered clays enriched with Fe(III) (TEOS‐g‐LDH−Fe/rGO) was prepared via emulsion polymerization followed by in situ precipitation and its physicochemical characterization carried out by FTIR, XRD, SEM‐EDS, HRTEM, TG‐ DTG, XPS and Raman analysis. The TEOS‐g‐LDH−Fe/rGO composite utilized for the effective removal of As(V) from aqueous system and the process followed via inner‐sphere surface complexation through ligand exchange between hydroxyl groups in TEOS‐g‐LDH−Fe/rGO and As(V) species. The equilibrium data fitted well with Langmuir model and kinetic data with mixed batch model showed remarkable adsorption capacity of 103.91 mg/g at pH 5.5. The synergistic effects associated with precursors in the composite profoundly improved the removal efficiency of As(V). The optimal conditions for As(V) removal was evaluated by RSM coupled with central composite design(CCD) considering pH(3–6), dose(0.5–2.5) and time (1–80 min) at temperature 30 °C. The sorption efficacy of TEOS‐g‐LDH−Fe/rGO was found to be about four times greater than its precursors. In simulated water matrix, the TEOS‐g‐LDH−Fe/rGO exhibit a retention of sorption performance (90 %) from 98.8 % of its initial sorption capacity for As(V) removal during regeneration. This work proves TEOS‐g‐LDHFe/rGO as a promising candidate for addressing grievous environmental threats from arsenic contamination.

Comparison of Pb2+ Adsorption Properties of Biochars Modified Through CO2 Atmosphere Pyrolysis and Nitric Acid

Acid modification has been widely used to modify the structural properties of biochars. However, acid modification led to the large consumption of acid, increased difficulty of waste effluent disposal, and a high application cost. To evaluate the advantages and application potential of biochars prepared under CO2, utilizing pyrolysis to directly modify biochars to improve heavy metal removal efficiency and reduce production cost, would be an important prerequisite for the broad application of biochars. The sorption performance of Pb2+ with CO2-modified biochars was compared with that of HNO3-modified biochar. The elemental compositions and structural properties of biochars were characterized through elemental analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results revealed that for biochars produced at 500℃, HNO3 modification produced abundant carboxylic groups and -NO2 (asy) and -NO2 (sym) groups, promoting the surface activities and complexing abilities of biochars. The CO2-modified biochars contained abundant carbonate minerals, which could remove Pb2+ by electrostatic ion exchange and coprecipitation or complex. In addition, compared to that of HNO3-modified biochars, CO2-modified biochars had the larger specific surface area and better microporous structures, which were beneficial to the diffusion of Pb2+ and further promoted surface sorption. CO2 modification increased the maximum Pb2+ sorption capacity of W500CO2 and W700CO2, which were 60.14 mg·g-1 and 71.69 mg·g-1. By contrast, HNO3-modified biochars W500N2-A and W700N2-A showed the lower Pb2+ sorption capacities, which were 42.26 mg·g-1 and 68.3 mg·g-1, respectively. The increasing of the specific surface area and functional groups simultaneously promoted the sorption capacity of CO2-modified biochars. Consequently, the CO2-modified biochar had the advantages of low cost, environmental friendliness, and high heavy metal removal efficiency, which is a modification method worthy of promotion and application.

Facile synthesis of a porous sorbent derived from the rice husk biomass: A new and highly efficient material for water remediation

This study describes a novel semi-synthetic sorbent for the sorption of cadmium nanoparticles (Cd-NPs) made from rice husks functionalized with nitric acid (NT-RH). Powder X-ray diffraction (PXRD) analysis verified the NT-RH synthesis and Cd sorption at the NT-RH (Cd@NT-RH). The surface functionalities of NT-RH that contributed most to the sorption of Cd-NPs were discovered using FTIR analysis. Scanning electron microscopic (SEM) examination shows that the acid-functionalized rice husk-based sorbent has a porous structure resembling a network with macro-sized voids. These voids practically vanish in the Cd@NT-RH, indicating their effective contribution to the sorbent's overall sorption activity. The elemental analysis further supports the PXRD and FTIR results and confirms the formation of NT-RH and its sorption potential for Cd-NPs. Furthermore, the effect of varied working temperatures, sorbent dosages, sorbent-sorbate contact period, and pH values on NT-RH sorption performance was investigated. Since the NT-RH's point of zero charge was determined to be 6.6, the sorbent's Cd-NPs elimination capacity was found to be highest at pH = 7, where a minimal quantity of competing (H+) and precipitating (OH–) ions is present. Cd sorption on NT-RH was better described by the Langmuir isotherm and pseudo-2nd order kinetics model. Thermodynamic analysis of Cd sorption at NT-RH demonstrates that the sorption process is exothermic and occurs spontaneously.

Preparation of nano-MFI zeolites doped with Al/Ti and their performance in VOC sorption.

Highly crystalline nano-MFI-type zeolites containing different elements were synthesized, and the sorption effects of the elements on volatile organic compounds (VOCs) were investigated. The results showed that the optimal toluene and acetone breakthrough time of the synthesized zeolites was 2.1 and 1.9 times as long as that of the commercial zeolite, respectively. For a weakly polar toluene molecule, MFI zeolites (aluminum-free) showed better adsorption properties than aluminum-containing zeolites. For the highly polar acetone molecule, zeolites with a Si/Al ratio of 87 showed the highest adsorption capacity, which was 7% higher than that of the all-silica zeolite and 1.4 times that of the commercial zeolite. Furthermore, MFI zeolites with Ti replacing part of Al proved to have better performance for highly polar molecules. In the adsorption process of VOCs, in addition to internal diffusion, diffusion on the external surface of the zeolite also played a remarkable role, and the adsorption data of all samples fitted better with the pseudo-first-order model. This study may provide a reliable structure-performance relationship for the synthesis of nanosized zeolite-based adsorbents and their use in the industrial recovery/treatment of VOCs.

Fluidized bed chemical looping for CO2 capture and catalytic methanation using dual function materials

CO2 capture from combustion flue gas combined to its catalytic hydrogenation to synthetic methane is considered as a promising technology in the field of Carbon Capture and Utilization (CCU). In this work, the integrated CO2 capture and methanation process was investigated in an innovative chemical looping configuration using dual function materials (DFMs) recirculated alternately between two interconnected bubbling fluidized bed reactors. By physically separating the CO2 capture step and the catalytic hydrogenation reaction in two coupled fluidized bed reactors it is possible to effectively control and independently optimize the operating temperature of each half cycle while running the process continuously. A high-performing Lithium-Ruthenium/Al2O3 was selected to investigate the effect of the specific temperature level for the CO2 capture and the methanation phases in the range 200 - 400 °C, checking the stability and repeatability of the CO2 sorption and catalytic performance over 5 repeated cycles for each operating condition. Subsequently, under the best conditions in terms of methanation performance, a similar Na-promoted dual function material was also tested. The DFMs performance appeared to be quite reproducible over the cycles, but it was subject to kinetic limitations, especially in the case of Na-Ru/Al2O3. Interestingly, the methane yield approached 100 % under the highest tested temperatures for the Li-based DFM. Despite some limitations due to the experimental purge phases of the lab-scale system, the study provides the proof-of-concept of the process which enables the possibility of decoupling the two steps with the aim of a large potential intensification.

Novel robust hierarchical porous membrane for uranium enrichment: fabrication, degradation behavior, and uranium sorption performance

Fabrication of hierarchical porous CAP membrane for uranium sorption.

Characterization of Water Vapor Sorption Performance and Heat Storage of MIL-101 (Cr) Complex MgCl2, LiCl/LaCl3 System for Adsorptive Thermal Conversion.

Adsorption heat conversion systems can provide heating and cooling across time and space in a more environmentally friendly way. Porous materials are potential candidates for water-based adsorption thermal conversion, in which a metal-organic framework (MOF) has a larger specific surface area and porosity than other porous matrices. However, many MOFs with high saturated adsorption capacity have great deficiencies in performance at low water vapor partial pressure, which hinder their application in adsorption thermal conversion. To improve the water vapor adsorption performance of MIL-101 (Cr), different contents of magnesium chloride, lithium chloride, and lanthanum chloride are mixed into MIL-101 (Cr) by an impregnation method. The properties and structures of the materials are characterized by XRD, SEM, nitrogen adsorption tests, water vapor adsorption tests, TG, FTIR, and so on. The results show that the saturated water vapor adsorption capacity of the sample impregnated with salt increases by 1.5-2.3 times, up to 2.24 g/g, compared with that of the unimpregnated sample. When the partial pressure of water vapor is 0.3, the adsorption capacity increases by 5.3-7.5 times and reaches 0.68 g/g at most. The maximum heat storage density of impregnated samples can be increased by 866 J/g. Impregnated MgCl2 can greatly improve the adsorption and thermal conversion performance of MOF, and impregnated MgCl2 and the proper amount of LiCl can further improve the performance of the material system. Our experiments show that the composite impregnation of magnesium chloride and the proper amount of lithium chloride can improve the application performance of the MOF materials in the adsorption thermal conversion process.

Engineering application of recyclable guanidine hydrochloride-hexamethylenediamine phytic acid polydopamine supported melamine sponge for the efficient elimination of europium and chromium from industrial wastewater

Synthesis and application of recyclable adsorbents with many available active sites and high adsorption capacity for accomplishing quick kinetics and high removal proportion have been become significant challenges in the purified fields of radionuclides and heavy metals contamination. Herein, regenerative ploy (guanidine hydrochloride hexamethylenediamine-phytic acid)-polydopamine decorated melamine sponges (PGH/HDPA/PDA/MS) were successfully synthesized using melted polymerization approach to remove Eu(III) and Cr(VI). The sorption behaviors and interactive mechanisms of Eu(III) and Cr(VI) by PGH/HDPA/PDA/MS were obtained via macroscopical experiments under various water chemistry factors conditions. The findings of our experimental studies demonstrated that specific sorption performances of Eu(III) and Cr(VI) onto PGH/HDPA/PDA/MS hybrids could achieve equilibrium within 3 h. The maximum adsorption capacities were respectively 2.43 × 10−3 mol/g and 6.75 × 10−3 mol/g for Eu(III) and Cr(VI), which were higher than large numbers of adsorbents reported among the anterior literatures. The interactive mechanism between PGH/HDPA/PDA/MS hybrids and Eu(III) and Cr(VI) was displayed through electrostatic attraction, cation exchange, surface complexation. Besides, the partially trivalent Cr(III) was also adhered to PGH/HDPA/PDA/MS surfaces through reductive reaction. According to our studies, the PGH/HDPA/PDA/MS hybrids are regarded as feasible adsorbents for highly effective purification of trivalent lanthanides and heavy metal ions pollutions from industrial wastewater.

Optimized synthesis of cysteine-functionalized nanocrystalline hydroxyapatite for synchronous decontamination of Cd(II) and Pb(II)

The synchronous removal of toxic heavy metals (e.g., cadmium (Cd), lead (Pb), and etc.) from the contaminated water environment is an urgent demand in the pollution control field. Herein, an innovative adsorbent synthesis idea was proposed and a series of cysteine-functionalized nanohydroxyapatite (CysHAP) composites were prepared by adopting different reaction temperatures, cysteine/HAP ratios, and synthesis methods. According to the single factor tests, a co-precipitation temperature of 25 °C with a molar cysteine/HAP ratio of 2.0 was selected to synthesize the optimum CysHAP2.0–25 composite. Multiple characterization results showed that cysteine markedly altered the morphology, crystallinity, and crystal structure of HAP, leading to the formation of CysHAP2.0–25 composite with a superior dispersity, a smaller crystal size, a higher specific surface area, and a greater number of binding sites. Compared with HAP-25, the CysHAP2.0–25 composite exhibited a better Cd(II) sorption performance and a 100% Pb(II) removal in a wide range of solution pH and background electrolyte concentration. The removal performance of CysHAP2.0–25 composite towards Cd(II) was suppressed by the coexisting aqueous components with an obviously stronger inhibiting action of humic acid (HA) than low molecular weight organic acids (LMWOAs) and mixed inorganic components (IC). Pb(II) slightly reduced the sorption ratio of Cd(II) and forced Cd(II) to bind on the -SOx sites derived from sulfhydryl oxidation. In contrast, Cd(II) had no impact on the sorption behaviors of Pb(II). Overall, the synthesized CysHAP2.0–25 composite could be potential applied for the purification of Cd- and Pb-bearing water systems.

Biochar supported nanoscale zerovalent iron-calcium alginate composite for simultaneous removal of Mn(II) and Cr(VI) from wastewater: Sorption performance and mechanisms

Heavy metal pollution in water caused by industrial activities has become a global environmental issue. Among them, manganese mining and smelting activities have caused the combined pollution of Cr(VI) and Mn(II) in water, posing a serious ecotoxicological risk to ecological environments and human health. To efficiently remove Cr(VI) and Mn(II) from wastewater, a novel biochar supported nanoscale zerovalent iron-calcium alginate composite (CA/nZVI/RSBC) was synthesized by liquid-phase reduction and calcium alginate embedding methods. The adsorption performance and mechanisms of Cr(VI) and Mn(II) by CA/nZVI/RSBC were investigated. The maximum adsorption capacities of Cr(VI) and Mn(II) onto CA/nZVI/RSBC fitted by the Langmuir model were 5.38 and 39.78 mg/g, respectively, which were much higher than the pristine biochar. The iron release from CA/nZVI/RSBC was comparatively lower than that of nZVI/RSBC. Mn(II) presence enhanced the reduction of Cr(VI) by CA/nZVI/RSBC. The results of XRD, XPS, and site energy distribution analysis indicated that redox was the predominant mechanism of Cr(VI) adsorption, while electrostatic attraction dominated Mn(II) adsorption. This study provides a novel alternative way for the simultaneous removal of Cr(VI) and Mn(II) in wastewater.

Carbon capture from low CO2 concentration stream through ternary alkali metal nitrates promotion of MgO sorbents at intermediate temperature and low space velocity

Many MgO sorbents exhibit high CO2 uptake in the presence of high concentration CO2 and aided by high space velocity, which unfortunately leads to low CO2 capture efficiency from the gas stream. This study investigates the effect of Li/Na/K ratio on sorption performance in dilute CO2 streams (15% CO2) using alkali metal nitrates-promoted MgO sorbents at a low space velocity of 20 ml/g·min in fixed bed reactor. Study shows that the ratio of Li/Na/K in ternary alkali nitrate salt mixture significantly affects the induction periods for the second phase CO2 sorption, which is a key contributor to high CO2 uptake. High LiNO3 content in ternary mixture leads to long induction period, and therefore lower CO2 capacity during the 4 h period. Conversely, high ratios of NaNO3 and KNO3 leads to shorter induction periods. Among the samples, MgO with 9 mol% (Li0.18Na0.52K0.3) exhibits the highest CO2 sorption capacity of 5.56 mmol/g at 240°C in 4 h (20.6% CO2 capture efficiency) and 3.18 mmol/g after 5 cycles (10.8% CO2 capture efficiency). Comparative studies show that optimal temperatures for CO2 sorption are higher when using pure CO2 (280 to 320°C) than when using 15% CO2 (240°C) due to the thermodynamic equilibrium. CO2-TPD results indicate that CO2 desorption proceeds in two phases similar to CO2 sorption, and the presence of alkali salt in MgO also promotes the decomposition of bulk carbonate to CO2. It is shown that molten salt migration and agglomeration of MgO particles are likely the factors that lead to decline in CO2 uptake over the sorption-desorption cycles.

Mechanistic insights to sorptive removal of four sulfonamide antibiotics from water using magnetite-functionalized biochar

Magnetite-functionalized biochar (MBC) is a promising engineered material for remediation of antibiotic-contaminated fields. However, sorption mechanisms of ionizable organic compounds such as sulfonamide antibiotics (SAs) on MBC are still unclear. This study employed four representative SAs including sulfamethazine (SMT), sulfamerazine (SMR), sulfadiazine (SDZ), and sulfamethoxazole (SMX), to compare the difference in sorption on MBC. Results showed that the sorption capacities and affinities of the four SAs varied with their substituents, hydrophobic properties, and dissociation constants (pKa). Synergistic effect during co-pyrolysis with Fe3+ enhanced the sorption performance of MBC towards SAs compared to original BC. Spectral methods confirmed structural changes of MBC such as the variance in oxygen-containing groups and defective/graphitized phases. Results of modeling pH-dependent sorption revealed that H-bonding or π-bond assisted H-bonding determined the sorption affinities and capacities of SAs. In particular, the SAs with lower pKa were thermodynamically favorable to form H-bonding with MBC via proton exchange with water molecules. Quantum calculation results quantified the contributions of H-bonding strengths and found that the energies of H-bonding were correlated with affinities of SAs. Moreover, contributions of oxygen-containing groups instead of minerals dominated the H-bonding energies. Mechanistic insights from this study can be valuable in exploring engineered BC composites for practical application in field remediation.Graphical

Converting Nanoflower-like Layered Double Hydroxides into Solvent-Free Nanofluids for CO2 Capture.

Due to the flexibility and versatility of the layered crystal structure of layered double hydroxides (LDHs), they have shown great potential in various fields. However, LDH nanosheets (LDH-NSs) are easy to agglomerate, leading to the problem of accumulation, which hinders their further application. Accordingly, once LDHs are combined with solvent-free nanofluids (SFNs), the advantages of LDHs and SFNs could be combined to achieve an extraordinary performance. However, the stacked structure of traditional LDHs is not conducive to the exposure of hydroxyl functional groups, and hydroxyl sites are key to the conversion of LDHs to SFNs. Therefore, in this work, nanoflower-like LDHs (NFLs) with abundant exposed hydroxyl groups were prepared and combined with organic oligomers to achieve a solid-to-liquid transition. The formation mechanism of NFLs and the grafting mechanism of OS-PEA on their surface were identified. The prepared NFL-F3 still has good fluidity and dispersion stability in different solvents after storage for 100 days. The high-saturated grafting density on the surface of NFLs increased the steric hindrance effect of the nanoparticles, thereby improving the dispersion stability and reducing the viscosity of NFL-F3. Notably, the CO2 sorption performance of NFL-F3 is significantly improved, which is attributed to the voids between polymers, physical sorption, and good fluidity caused by high-saturation grafting on the surface of NFL-F3. Finally, by combining the sorption behavior and model fitting, it was confirmed that the physical effect was dominant in CO2 sorption by the NFL-F, which saved energy for the sorption-desorption process of its industrial application. Moreover, NFL-F3 has a good CO2/N2 separation performance and cycle stability. We envision that this general strategy will open up new insights into the construction of innovative low-viscosity LDH-based SFNs with high CO2 capacity and facilitate CO2/N2 selectivity and offer new directions for LDH utilizations.