Adsorption Properties Research Articles

Enrichment of deoxynojirimycin in mulberry using cation exchange resin: Adsorption/desorption characteristics and process optimization

Deoxynojirimycin (DNJ) is an α-glucosidase inhibitor with high food values. However, the complex and costly enrichment processes have greatly prevented its application. Herein, this study aimed to propose a simple and efficient enrichment process for DNJ from Morus alba L. extracts using cation exchange resins. The LSI and D113 resins were chosen due to their excellent adsorption and desorption properties. The adsorption characteristics agreed with the pseudo-first-order kinetic model and the Langmuir isotherm model. This adsorption was chemisorption, spontaneous, endothermic and entropy-driven. Furthermore, the concentration and pH of the extracts, desorption solvent, breakthrough and elution curves, sample loading and elution rate were investigated to optimize the enrichment process by resin column chromatography. The results also showed that the purity of DNJ was improved to 44.00 % with a total recovery of 78.21 % using the LSI-D113 combination strategy. This research demonstrated the industrial feasibility of DNJ enrichment using cation exchange resins.

Machine Learning Models to Predict Early Breakthrough of Recalcitrant Organic Micropollutants in Granular Activated Carbon Adsorbers.

Granular activated carbon (GAC) adsorption is frequently used to remove recalcitrant organic micropollutants (MPs) from water. The overarching aim of this research was to develop machine learning (ML) models to predict GAC performance from adsorbent, adsorbate, and background water matrix properties. For model calibration, MP breakthrough curves were compiled and analyzed to determine the bed volumes of water that can be treated until MP breakthrough reaches ten percent of the influent MP concentration (BV10). Over 400 data points were split into training, validation, and testing sets. Seventeen variables describing MP, background water matrix, and GAC properties were explored in ML models to predict log10-transformed BV10 values. Using the ML models on the testing set, predicted BV10 values exhibited mean absolute errors of ∼0.12 log units and were highly correlated with experimentally determined values (R2 ≥ 0.88). The top three drivers influencing BV10 predictions were the air-hexadecane partition coefficient and hydrogen bond acidity (Abraham parameters L and A) of the MPs and the dissolved organic carbon concentration of the GAC influent water. The model can be used to rapidly estimate the GAC bed life, select effective GAC products for a given treatment scenario, and explore the suitability of GAC treatment for remediating emerging MPs.

The Phosphonitrilic-derived graphynes as promising adsorbents of greenhouse gases

The new hybrid graphyne-like materials with highly developed specific surface area and excellent greenhouse gas adsorption properties have been described. Inorganic P3N3Cl6 was selected as a building block and 1,4-diacetylene benzene was chosen as a linker for these materials. The chemical structure of P3N3Cl6 allows for creation of three-dimensional materials with the BET surface area ranging from 600 to 1000 m2 g−1 and a pore volume as high as 0.3 cm3 g−1. The obtained materials showed microporous structure and distinctive greenhouse gas adsorption properties. For those materials, CO2 adsorption reached as high as 1.5 mmol g−1, while for N2O ranged from 1.5 to 1.7 mmol g−1, and for CH4 was 0.4 mmol g−1 when adsorption was carried out at 100 kPa and 300 K. Moreover, obtained by the modified Dubinin adsorption model, the maximum adsorption values were 2.5–11 mmol g−1 depending on the type of materials used. This finding suggests that new materials are promising high-pressure adsorbents of greenhouse gases.

Interactions between microplastics and heavy metals in leachate: Implications for landfill stabilization process

The emission of microplastics and heavy metals in landfills has attracted widespread attention for its stabilization process. Microplastics have become carriers of heavy metals due to their adsorption properties, affecting their environmental behavior. However, the effects of landfill stabilization on the interaction between microplastics and heavy metals in leachate are ambiguous. This work explored the abundance characteristics of microplastics and heavy metals in leachate from 10 landfills in Beijing. Overall, the average abundance of microplastics was 196.3 items/L, dominated by small particle size (20–50 µm) and film microplastics. The levels of Cr and As were much higher than other heavy metals. The average abundance of microplastics and polymer types tended to decrease as the landfill stabilization proceeded, and the surface composition of microplastics became more complex. Statistical analysis revealed that the correlations between microplastics and heavy metals in the leachate of landfill stabilization presented significant parabolic characteristics, and Cr and As were more susceptible to landfill stabilization with significant positive correlation with a wide range of microplastics such as 20–30 µm. These results were intended to provide a scientific basis for the treatment and disposal of waste leachate and the synergistic prevention and control of new and traditional pollutants.

Scalable fabrication of hypercrosslinked imidazole cationic polymer membranes for the efficient removal of 99TcO4−/ReO4−

Developing efficient and low-cost materials and technologies for the radioactive pertechnetate anion (99TcO4−) removal from contaminated groundwater is highly desired but remains a challenge. Herein, hypercrosslinked imidazole cationic polymers (HIPs), HIPs-1 and HIPs-2, were prepared. Benefiting from high density imidazole cationic groups, HIPs-2 exhibited rapid removal kinetics (with ∼100 % removal efficiency within 30 s) and considerable adsorption capacity (632.5 mg/g) in perrhenate anion (ReO4−, nonradioactive surrogate of 99TcO4−) spiked aqueous solution. HIPs-2 also showed excellent capture for ReO4− in groundwater (with dynamic adsorption capacities of 136.4 mg/g in ReO4−-spiked groundwater). Theoretical calculation revealed the adsorption mechanism of ion exchange. Encouraged by the excellent adsorption properties, HIPs-2 were fabricated into membranes M-HIPs-2/PAN using electrospinning. Dynamic adsorption experiments showed that ∼0.0934 g M-HIPs-2/PAN could continuously purify 1110 mL of ∼5.66 ppm ReO4−-spiked tap water to 0 ppm, with dynamic adsorption capacity of 87.3 mg/g. And still the dynamic adsorption capacity was 32.4 mg/g in ReO4−-spiked groundwater. M-HIPs-2/PAN exhibited satisfactory cycling stability, removing more than 97.5 % of the ReO4− after six cycles. More importantly, M-HIPs-2/PAN, derived from inexpensive raw materials with simple synthesis process, provides an efficient and economical approach for the large-scale treatment of groundwater contaminated with 99TcO4−.

Fluorescent cellulose nanofibrils hydrogels for sensitive detection and efficient adsorption of Cu2+ and Cr6+

Increasing chromium and copper pollution poses a significant threat to the global environment and human health. It is crucial to detect and remove Cu (II) and Cr (VI) from water. Cellulose nanofibrils (CNF)-based hydrogels were a natural, abundant, and biocompatible material that has attracted great attention for bio adsorption applications. In this work, a new fluorescent CNF-based hydrogel (PAA-CNF-W) was prepared for the high-efficiency adsorption and sensitive detection of Cu (II) and Cr (VI). CNF was introduced as a natural backbone to construct a three-dimensional porous structure, which increased the specific surface area and provided additional active sites, exhibiting excellent adsorption properties for Cu (II) (159.24 mg/g) and Cr (VI) (173.87 mg/g). Moreover, the synthesized dansyl chloride derivatives with fluorescent properties were introduced to the hydrogel and formed chelates with the metals leading to fluorescence quenching. PAA-CNF-W hydrogels showed high sensitivity to the detection limit (LOD) of Cu (II) (28.70 mg/L) and Cr (VI) (1.45 mg/L). The kinetic study revealed that pseudo-second order kinetics was the best-fitting model. The Langmuir isotherm was the best adjustment model. The study provides a new idea for efficient detection and removal of Cu (II) and Cr (VI) from wastewater by cellulose materials.

Safe detoxification on acid-washed activated carbon combined with chitosan for aflatoxins from contaminated peanut oil.

Aflatoxins are one of the most toxic mycotoxins and can cause serious harm to humans and animals. Adsorption is a practical decontamination technique favored by the industry because of its advantages of low cost, speed and simplicity, and environmental friendliness. In this work, the adsorption features of activated carbon and chitosan were fabricated in a composite through chemical co-precipitation to improve its properties for adsorption. Furthermore, the capacity of the synthesized chitosan and acid-washed activated carbon composite (CS-AAC) to attenuate the aflatoxins in contaminated peanut oil and the adsorption capacity at different initial aflatoxins content, contact duration, and temperature were evaluated. The results showed a higher adsorption capacity (removal efficiency to 93.45% of AFB1, 94.05% of AFB2, 89.16% of AFG1, 83.26% of AFG2). The Freundlich isothermal and D-R model and the pseudo-second-order rate expression both implied a good correlation with the test data and explained the adsorption mechanism well. The adsorption mechanism was found to be accomplished primarily via ion exchange and chelation. According to thermodynamic results (△G < 0, △H > 0, △S > 0), the adsorption process was endothermic and spontaneous. Compared to acid-washed activated carbon, CS-AAC enhanced the retention of VE and sterols (especially VE by 23%), and the safety of CS-AAC adsorbent was explored by cellular experiments. In conclusion, CS-AAC is a promising adsorbent material for the removal of aflatoxins from edible oils.

Ellipsoidal micelle formation of quaternary ammonium salt-based gemini surfactants: structural analysis through small-angle X-ray scattering.

Gemini surfactants exhibit better adsorption and aggregation properties than those of monomeric surfactants. However, to enhance the functional properties of gemini surfactants, the effect of spacer structures on their aggregation behavior must be elucidated. Small-angle X-ray scattering (SAXS) has been performed to study the aggregate structures of monomeric surfactants, but its application has not been expanded to the analysis of gemini surfactants. Therefore, in this study, we performed a structural analysis of aggregates formed by quaternary ammonium salt-based gemini surfactants with different spacer structures in aqueous solutions through viscosity, dynamic light scattering (DLS), and SAXS measurements. We also investigated the effects of the spacer structure and surfactant concentration on the aggregation behavior. The DLS results indicated that gemini surfactants with spacers containing cyclic structures, such as diethylene and triethylene chains, formed small micelles (several nanometers in size) at the limiting concentration for dissolution in water. In contrast, gemini surfactants with nitrogen and oxygen atoms at the center of the spacer formed ellipsoidal micelles at low concentrations, as shown by SAXS results. The core and overall radii of the minor and major axes of the ellipsoidal micelles decreased with increasing surfactant concentration and were larger for spacers with two ethylene chains connected to central nitrogen and oxygen atoms than for spacers with rigid diethylene and ethylene chains connected to a central nitrogen atom.

Insights into the dynamics of supported Au nanoparticles in the wet environments from first-principles and ReaxFF MD simulations

The interactions between metal and oxide supports have been widely studied, where the size effect of metal nanoparticles (NPs) and the gas environment play critical roles in catalytic performance. We employed density functional theory and ReaxFF reactive force field to investigate the size dependent properties of gold NPs supported on cerium dioxide, such as structural dynamics, adsorption, and electronic properties under wet environments. Distinct dynamic behaviors were observed in wet environments compared to vacuum conditions. In the wet environments, the hydroxide (OH) species preferentially adsorbs on the low coordination sites, such as edge sites, of NPs. This selective absorption induces a reconstruction effect on small NPs. Moderate-sized NPs exhibit significant surface reconstruction due to abundant OH adsorption at interface sites. However, this effect is negligible in larger NPs. A high interfacial population of OH significantly contributes the high catalytic performance of moderate-sized NPs. Moreover, OH adsorption modulates the charge distribution within the NPs, leading to their stabilization through OH-induced charge transfer. These findings provide insights into understanding and optimizing reactions in wet environments, offering a foundation for the development of more effective catalyst.

Hydrothermal synthesis, characterization of Co3Sb4O6F6 and carbon doped Co3Sb4O6F6 and their application towards photocatalytic dye degradation, adsorption, catalytic Knoevenagel condensation and bacterial disinfection

Single crystals of Co3Sb4O6F6 have been grown by employing hydrothermal techniques. Table sugar was utilized to prepare carbon-doped Co3Sb4O6F6. The objective was to employ Co(II)-based metal oxyfluoride comprising a stereochemically active lone pair element (Sb3+) and its carbon-doped analogues for the multifunctional applications. The impact of carbon doping on Co3Sb4O6F6 has been evaluated towards the changes in photocatalytic, catalytic, and adsorbent efficiency. The changes in carbon percentage affect the physical and chemical properties of the host material. A larger percentage of carbon doping turns the photocatalytic ability of the host material into an adsorbent for the removal of dye. The single crystal X-ray diffraction study reveals that Co3Sb4O6F6 crystallizes into cubic symmetry. However, powder X-ray diffraction study reveals the structural transformation in the carbon-doped Co3Sb4O6F6. It also reduces the band gap energy of the host material, and 4 wt% C@Co3Sb4O6F6 turns out to be an efficient photocatalyst. Large-scale carbon doping (15 wt%) appears to be an effective strategy to increase the surface charge and BET surface area, as consequences adsorption property develops in 15 wt% C@Co3Sb4O6F6/H2O2 for the elimination of methylene blue (MB). This favourable chemical adsorption process occurs with large maximum adsorption capacity (qmax = 58.41169 mg g-1), as evident from the Langmuir adsorption isotherm. Scavenger experiment confirms that the photocatalytic activities of the as-synthesised compounds were triggered by the active participation of the hydroxyl radical (.OH). The catalytic efficiencies of both parent and doped compounds are also established for the solvent-free Knoevenagel condensation reaction with 90 % yield at moderate temperature. Bacterial disinfection studies by the ‘Disc diffusion method’ confirm that Co3Sb4O6F6 shows better efficiency than the carbon doped compound against both Gram-positive and Gram-negative bacteria.

Hierarchically porous MgO/biochar composites for efficient CO2 capture: Structure, performance and mechanism

For enhancing the CO2 uptake performance of MgO-based materials, hierarchically porous MgO/biochar composites were prepared using a microwave-assisted hydrothermal method. The CO2 adsorption properties was investigated in detail and the adsorption mechanism was revealed by considering structure − function relationships and performing density functional theory calculations. The MgO/biochar-1 had hierarchical pore structure and high specific surface area (1453 m2·g−1) with abundant narrow micropores (<1.0 nm), facilitating the adsorption of CO2. The results demonstrated that MgO/biochar-1 exhibited the highest CO2 capture capacity of 6.65 mol⋅kg−1 (273 K, 1 bar) and excellent selectivity for CO2/N2 (96.70 at CO2/N2 = 15:85, v/v). After 3 cycles, the adsorption capacity of MgO/biochar-1 still remained at 5.70 mol⋅kg−1 (273 K, 1 bar), suggesting the well cycling performance. The results of density functional theory calculation indicated that the oxygen-containing functional groups and MgO particles substantially enhanced the CO2 capture performance due to the enhanced interactions between MgO/biochar and CO2. This study provides novel insights for the construction of efficient and cheap solid adsorbents for CO2 capture.

First-principles study of the electronic, optical adsorption, and photocatalytic water-splitting properties of a strain-tuned SiC/WS2 heterojunction

Heterojunction is widely acknowledged as a potent strategy as an effective means for achieving quality electronic, optical adsorption, and photocatalytic water-splitting properties. Strain also can regulate these properties effectively. In this study, we have fabricated and studied a heterojunction comprised SiC and WS2. Utilizing a first-principles method, we systematically investigated the SiC/WS2 heterojunction's structure, stability, electronic, and optical properties, as well as its photocatalytic water splitting characteristics under strain engineering. Our calculations reveal that the SiC/WS2 heterojunction is a type-II heterostructure with two stable structures, which exhibits a direct bandgap and well performance in the visible light region, facilitating efficient separation of photogenerated electron-hole pairs. We have explored and discussed the impacts of biaxial strain on the various properties. The bandgaps of System-A and B are 1.778 eV and 1.820 eV, respectively, without strain. Under strain from −6% to 10%, they initially rise, peak at 1.858 eV and 1.899 eV respectively at −2% strain, then decline. Without strain, effective mass mh/me for both structures are 1.642 and 1.673. Under positive strain, they increase, decrease, then increase again, peaking at 6% with 2.116 and 2.260. At −2% strain, values drop to 0.901 and 0.910 for A and B, respectively. Our calculations also demonstrate that the SiC/WS2 heterostructure qualifies as a promising photocatalytic material, fulfilling the criteria for water splitting under strain conditions of −4%, −2%, and 0%. And the heterojunction with System-B under −4% strain has the optimal performance in photocatalytic water splitting. At a strain of −4%, System-B achieves the maximum η′STH of 16.91%. In conclusion, our study not only offers fundamental insights into the utilization of SiC/WS2 heterojunctions for photocatalytic water splitting, but also provides the foundational design principles of heterojunctions.

The collaborative effect of Ni3S2-NiO heterojunction and porous carbon network modified lithium-sulfur battery separator for effectively inhibiting polysulfides shuttle

As an important part of lithium-sulfur battery (LSB), separator not only provides ion transport channel but also plays a key role in ensuring battery safety. However, the aperture of the commercial separator polypropylene (PP) is relatively large, which cannot effectively inhibit the migration of polysulfides generated during the charging and discharging process between the positive and negative electrodes, resulting in a decrease in the cycle stability of LSB. In this work, a modified LSB separator Ni3S2-NiO@AC-4@PP is designed, which is anchored by Ni3S2-NiO heterojunction on volcanic rock-like three-dimensional porous carbon network (AC) as the functional interlayer. The AC possesses a large specific surface area and excellent electrical conductivity, creating sufficient space for the physical and chemical adsorption of insoluble polysulfides. The Ni3S2-NiO heterojunction is embedded and attached to the AC, which helps to hinder the diffusion of polysulfides and accelerate the redox reaction. It is also confirmed by density functional theory (DFT) calculation that Ni3S2-NiO heterojunction inhibited the shuttle of polysulfides through the adsorption capacity of NiO and the catalytic activity of Ni3S2. Thus, the Ni3S2-NiO@AC-4@PP battery exhibits an elevated initial specific capacity of 1027.8 mAh g−1 at 0.2C, maintaining long-term stability after 200 cycles with the capacity retention rate of 81.4 %. At the higher current density (2C), Ni3S2-NiO@AC@PP battery demonstrates durable cycle with the capacity retention rate of 91.3 %. This study proposes a new feasible strategy to obtain high-performance, low-cost modified separators by designing functional interlayers with excellent adsorption and catalytic properties.

Synergetic studies on the thermochemical activation and polyaniline integration on the adsorption properties of natural coal for chlorpyrifos pesticide: steric and energetic studies

Three types of synthetic coal-derived adsorbents were characterized as potential enhanced structurers during the removal of chlorpyrifos pesticide. The raw coal (CA) was activated into porous graphitic carbon (AC), and both CA and AC were blended with polyaniline polymers (PANI/CA and PANI/AC) forming two advanced composites. The adsorption performances of the modified structures in comparison with CA were evaluated based on both the steric and energetic parameters of the applied advanced isotherm model (the monolayer model of one energy). The uptake performances reflected higher capacities for the PANI hybridized form (235.8 mg/g (PANI/CA) and 309.75 mg/g (PANI/AC) as compared to AC (156.9 mg/g) and raw coal (135.8 mg/g). This signifies the impact of activation step and PANI blending on the surface and textural properties of coal. The steric investigation determined the saturation of the coal surface with extra active sites after the activation step (Nm(AC) = 62.05 mg/g) and the PANI integration (Nm(PANI/CA) = 113.5 mg/g and Nm(PANI/AC) = 169.7 mg/g) as compared to raw coal (Nm(CA) = 39.6 mg/g). This illustrated the reported uptake efficiencies of the modified samples, which can be attributed to the enhancement in the surface area and the incorporation of additional chemical groups. The results also reflect that each site can be loaded with 3–4 molecules of chlorpyrifos, which are arranged vertically and adsorbed by multi-molecular mechanisms. The energetic studies (< 40 kJ/mol) suggested the physical uptake of pesticide molecules by dipole bonding and hydrogen bonding processes. The thermodynamic functions donate the exothermic properties of 47reactions that occur spontaneously.

A new adsorbent of amidoxime functionalized porous corn stalk carbon and its adsorption properties for U(VI) from seawater

A new adsorbent of amidoxime functionalized porous corn stalk carbon and its adsorption properties for U(VI) from seawater

Removal of Remazol Red Dyes Using Zeolites-Loaded Nanofibre Coated on Fabric Substrates

Nanofibre-based membranes have shown great potential for removing textile wastewater due to their high porosity and surface area. However, nanofibre membranes exhibit lower dye removal efficiency. Hence, this study aims to improve the dye removal performance of nanofibre membranes by incorporating zeolites. The research involved fabricating composite membranes by electrospinning polyvinyl alcohol (PVA) nanofibres incorporated with zeolites. Mechanical strength was enhanced by placing the PVA/zeolite nanofibre membrane between fusible nonwoven interfacing and woven polyester fabric, followed by heat treatment. Morphological analysis revealed the uniform dispersion of zeolite particles within the PVA nanofibres. EDX analysis confirmed the successful incorporation of zeolites into the fibres. Among all membrane samples, the PZ-0.75 membrane exhibited the highest pure water flux (PWF) with approximately 1358.57 L·m−2·min−1 for distilled water and 499.85 L·m−2·min−1 for batik wastewater. Turbidity of batik wastewater increased proportionally with zeolite concentration, with removal rates of 84.79%, 78.8%, 76.96%, and 74.19% for PZ-0.75, PZ-0.5, PZ-0.25, and PVA membranes, respectively. Furthermore, the UV/Vis spectrophotometer demonstrated that dye removal efficiency increased from 2.22% to 8.89% as the zeolite concentration increased from 0% to 0.75%. In addition, the PZ-0.75 membrane effectively removed RR dye at a concentration of 1 mg/L, with an optimal contact time of approximately 60 min. The adsorption mechanism of the PZ-0.75 membrane aligns with the Freundlich model, with an R2 value of 0.983. Overall, this study demonstrates the efficiency of zeolite in the fabric substrates to improve the filtration and adsorption properties for wastewater treatment, particularly in textile industries.

Enhanced hydrogen adsorption properties of Zeolite Templated Carbon via chemical activation: DFT study

In this study, Density Functional Theory (DFT) simulation method was applied to show that hydrogen-storage properties of Zeolite Templated Carbon (ZTC) can be enhanced via chemical activation. Study results calculated via simulation and the Monte Carlo integration technique showed that in comparison to unactivated ZTC, the theoretical specific surface area (SSA) for Zeolite Templated Activated Carbon (ZTAC) increased by 4.79 and 2.13 %, when activated with either Zinc dichloride (ZnCl2) or Potassium Hydroxide (KOH), respectively. In addition, calculation of accessible surface area (ASA) resulted in 7809.40 m2/g and 7611.74 m2/g, correspondingly. Simulations of H2 adsorption revealed that H2 molecules were adsorbed primarily on the concave region of the ZTAC. Also, it was found the that the largest amountof H2 adsorbed molecules on ZTAC activated with either ZnCl2 or KOH were13 and 15, and the average binding energies were 0.184 eV and 0.202 eV, respectively. In this regard, the maximum hydrogen storage capacity obtained in this study was 5.2 wt% (ZTAC-13H2) and 5.95 wt% (ZTAC-15H2) with a volumetric density of 0.065 kg H2/L and 0.074 kg H2/L for the ZTAC activated with either ZnCl2 or KOH. These results are in accordance with the U.S. Department of Energy (DOE) ultimate target by the 2025 year. In addition, thermal stability and desorption temperatures of ZTAC structures were determined via molecular dynamics simulations and through the van’t Hoff equation, showing that hydrogen molecules were easy to desorb at room temperature (T=300 K). These results pose these systems suitable for automotive onboard applications, leading to future research on synthesis techniques of ZTAC materials which certainly require more experimental investigation.

Zeolite-carbon composite synthesis and its adsorption property

In this study, SUZ-4 zeolite-carbon composites were synthesized by a one-step hydrothermal method with solid waste, silica fume (SF), aluminum ash (AA), and chitosan (CS), as raw materials. The composites were analyzed by XRD, SEM, FTIR and BET characterizations. The adsorption capacities of the composites for lead ions (Pb2+) and methyl orange (MO) from aqueous solutions were investigated. Based on the adsorption data, pseudo-second-order model and the Freundlich model were suitable to describe the adsorption process of Pb2+ on the composite, while the pseudo-second-order model and the Langmuir model were preferred to describe the adsorption process of MO on the composite. The maximum adsorption capacity of the composite for Pb2+ was 102.2 mg/g at pH=6, and that for MO was 488.3 mg/g at pH=3. The resulting composites have practical applications as adsorbents for wastewater treatment, thus achieving the goal of “waste for waste”.

Effects of Over-Sintering on Cyclic Calcination and Carbonization of Natural Limestone for CO2 Capture

To know the sustainable performance of calcium-based adsorbents is one of the important aspects to realize efficient and economical carbon capture, and to systematically study the properties of natural adsorbents is conducive to their industrialization. The cyclic calcination and carbonation characteristics of a typical natural limestone were investigated using a thermal gravimetric analyzer. Two kinds of over-sintering conditions were selected to emphatically study the cyclic separation of CO2 from limestones through prolonging the calcination time and increasing the calcination temperature. The results showed that the untimely end of the chemical reaction control stage caused by excessive sintering is the direct reason for the reduction in cyclic carbonation conversion, and the changes in surface morphology of calcined products due to pore collapse and fusion are the fundamental reasons for the reduction in cyclic carbonation conversion. The excessive sintering caused by extending the calcining time or increasing the calcining temperature has great inhibition on this cycle only; the inhibition decreases rapidly in subsequent cycles. In addition, SEM and BET–BJH tests further confirm the influence of the over-sintering phenomenon. With the further increase in cycle number, the early excessive sintering has certain stimulative effects on the subsequent carbonation reaction. It is expected to provide a reference for the subsequent research and development of natural calcium-based adsorbents.

Highly porous carbon with rich inherent groups for ultrahigh adsorption of organic dyes from wastewater

Activated carbon from renewable biomass or its waste to purify various dyeing wastewater from textile industry is highly desired. In this work, porous activated carbon was prepared by using silk waste as precursor via a simple one-step carbonization process. The obtained SWC-1-800 had ultrahigh adsorption for anionic dye AR73 and cationic dye MB owing to its ultrahigh specific surface area (2774 m2 g−1) and rich functional groups. SWC-1-800 had an increased adsorption capacity reaching 1310 and 928 mg g−1 for AR73 and MB respectively as the initial concentration up to 1000 mg L−1. Moreover, the adsorption capacity was stable under a wide range of Na+ and SDS concentration. By adjusting the temperature and pH value, the maximum adsorption capacity reached 1337 and 1000 mg g−1 for AR73 and MB respectively, keeping the removal rate of AR73 and MB more than 80 % after 5 adsorption cycles. Besides, SWC-1-800 demonstrated quite good adsorption ability for many other kinds of dyes, which adsorption capacity as high as 1998 mg g−1 (Rh B). The adsorption mechanism was further proposed according to the structural characteristics, inherent functional groups and adsorption properties. Using silk waste-derived carbon to effectively absorb the harmful dyes in the wastewater shows dual value for cleaner production via a “waste-waste to clean products” model, which has great application potential in dyeing wastewater purification.