Adsorption Desorption Research Articles

Reuse of polymeric waste for the treatment of marine water polluted by diesel

Accidental diesel spills can occur in marine environments such as harbors, leading to adverse effects on the environmental compartment and humans. This study proposes the surgical mask as an affordable and sustainable adsorbent for the remediation of diesel–contaminated seawater to cope with the polymeric waste generated monthly in hospital facilities. This approach can also be helpful considering a possible future pandemic, alleviating the pressure on the waste management system by avoiding improper mask incineration and landfilling, as instead occurred during the previous COVID–19. Batch adsorption–desorption experiments revealed a complete diesel removal from seawater after 120 min with the intact laceless mask, which showed an adsorption capacity of up to 3.43 g/g. The adsorption curve was better predicted via Weber and Morris's kinetic (R2 = 0.876) and, in general, with Temkin isotherm (R2 = 0.965–0.996) probably due to the occurrence of chemisorption with intraparticle diffusion as one of the rates–determining steps. A hysteresis index of 0.23–0.36 was obtained from the desorption isotherms, suggesting that diesel adsorption onto surgical masks was faster than the desorption mechanism. Also, the effect of pH, ionic strength and temperature on diesel adsorption was examined. The results from the reusability tests indicated that the surgical mask can be regenerated for 5 consecutive cycles while decreasing the adsorption capacity by only approximately 11%.

Adsorption Capacity of Carbon-Silica Composites Towards Diclofenac in Poly(acrylic acid) Containing Systems: A Crucial Study on Common Wastewater Contaminants.

Diclofenac is one of the most popular over-the-counter non-steroidal anti-inflammatory drug and poly(acrylic acid) is a frequently used as thickener, filler or stabilizer. For these reasons, they are common organic contaminants in raw wastewater. The purpose of the presented studies was to compare the adsorption capacity of three carbon-silica composites - metal-free C/SiO2, iron-enriched C/Fe/SiO2 and manganese-enriched C/Mn/SiO2 towards diclofenac. The studies were carried out in single, and mixed systems in the presence of poly(acrylic acid) polymer. Adsorption, desorption and kinetics of the adsorption process were investigated. The concentration of diclofenac in the supernatants was determined using high-performance liquid chromatography. The solids were also characterized with an ASAP apparatus using low-temperature nitrogen desorption adsorption isotherms at liquid nitrogen temperature. In addition, potentiometric titrations and electrophoretic mobility measurements, as well as stability tests of the studied suspensions were carried out. The most efficient composite among investigated ones proved to be C/Fe/SiO2 removing diclofenac at the level of 46.68 mg/g for its initial concentration of 90 ppm. The results obtained clearly demonstrated that the carbon-silica composites are effective in separation of drugs from aqueous solutions and can be successfully used in the future for the removal of organic pollutants from water environment.

Novel spinel based high entropy oxide as electrode for symmetric SOFCs

Fabrication of symmetric electrodes for intermediate temperature SOFCs can significantly reduce fuel cell production costs without compromising efficiency. Herein, we report a novel spinel based high entropy oxide (CuLiFeCoNi)1.4Mn1.6O4-δ (CM-HEO) that exhibit better symmetric electrode properties than the parent spinel oxide, Cu1.4Mn1.6O4-δ (CM). The prepared HEO exhibited good structural and thermal stability up to 800 °C as inferred from the XRD, Raman and TGA-DSC results. Temperature-programmed reduction and desorption profiles of CM-HEO outperformed CM by exhibiting hydrogen adsorption and lower CO2 desorption across different temperature ranges. The enhancement of Lewis acid-base sites is evident from the XPS analysis validating the observed increase in HOR and ORR activity. The high electrocatalytic activity of the material arise from its lower activation energies (0.27 eV in air, 0.09 eV in dry H2 and 0.03 eV in dry CH4) with a polarisation resistances of 0.152 Ωcm2 under ambient atmosphere and 0.044 Ωcm2 under dry H2. These findings exalt CM-HEO as an efficient symmetric SOFC electrode material.

Effect of Intrinsic Ferroelectric Phase Transition on Hydrogen Evolution Electrocatalysis.

Heterogeneous electrocatalysis closely relies on the electronic structure of the catalytic materials. The ferroelectric-to-paraelectric phase transition of the materials also involves a change in the state of electrons that could impact the electrocatalytic activity, but such correlation remains unexplored. Here, we demonstrate experimentally and theoretically that the intrinsic electrocatalytic activity could be regulated as exampled by hydrogen evolution reaction catalysis over two-dimensional ferroelectric CuInP2S6. The obvious discontinuity in the overpotential and apparent activation energy values for CuInP2S6 electrode are illustrated during the ferroelectric-to-paraelectric phase transition caused by copper displacement around Tc point (318 K), revealing the ferroelectro-catalytic effect on thermodynamics and kinetics of electrocatalysis. When loading Pt single atom on the CuInP2S6, the paraelectric phase one showed an improved hydrogen evolution activity with smaller apparent activation energy over the ferroelectric phase counterpart. This is attributed to the copper hopping between two sulfur planes, which alternate between strong and weak H adsorption at the Pt sites to simultaneously promote H+ reactant adsorption and H2 product desorption.

Propane dehydrogenation on Ir single‐atom catalyst modified by atomically dispersed Sn promoters in silicalite‐1 zeolite

AbstractPropylene serves as a crucial feedstock for a wide range of industries engaged in the production of diverse petrochemical products. Propane dehydrogenation, an appealing technology aimed at supplanting conventional methodologies, confronts significant hurdles attributable to coke deposition and sintering in Pt‐based catalysts. Here, we report an Ir single atom encapsulated in silicalite‐1 zeolite modified with Sn single atoms as electronic promoters, displaying remarkable activity and stability, which is significantly greater than the previously reported Ir‐based catalysts and comparable to the majority of Pt‐based catalysts under similar industrial conditions (600°C, C3H8/H2 = 2/1). Spectroscopies results reveal that the introduction of Sn atoms promotes the transfer of electrons from Sn atoms to Ir atoms, forming electron‐rich Irδ+ species. DFT calculations show that the unique electronic structure lowers the energy barrier for two‐step dehydrogenation as well as favors the adsorption of propane and desorption of propylene, thus enhancing the activity and stability.

Effects of Polyether Amine Canopy Structure on Heavy Metal Ions Adsorption of Magnetic Solvent-Free Nanofluids.

Three Fe3O4 magnetic solvent-free nanofluids with different amine-based coronal layer structures are synthesized and characterized by using magnetic Fe3O4 as the core, silane coupling agent as the corona, and polyether amines with different graft densities and chain lengths as the canopy. The concentration of heavy metal ions after adsorption is measured by atomic absorption spectrometry (AAS) to study the effect of Fe3O4 magnetic solvent-free nanofluids on the adsorption performance of the heavy metal ions lead (Pb(II)) and copper (Cu(II)) in water. The adsorption of Fe3O4 magnetic solvent-free nanofluid was explored by changing external condition factors such as adsorption contact time and pH. Additionally, the adsorption model is established. The magnetic solvent-free nanofluid is separated from water by applying an external magnetic field to the system, and desorption and cyclic adsorption tests are carried out. Based on the adsorption mechanism, the structure design of Fe3O4 magnetic solvent-free nanofluid was optimized to achieve optimal adsorption performance.

Hierarchical aerogels based on cellulose nanofibers and long-chain polymers for enhancing oil–water separation efficiency

The hydrophobic chain length of biomass-based aerogels used for oil–water separation was evaluated as a major parameter influencing the aerogels’ hydrophobicity. The properties of the porous structure were enhanced by the hierarchical assembly of the aerogels with biopolymeric structural units and polymer mineralization. The cellulose network was strengthened through silanization, and the nanocellulose network was further enhanced through coating with mineralizers containing long-chain hydrophobic molecules. Interfacial engineering was employed to establish multiscale interactions through the freeze-drying-induced modification of cellulose nanofibers and mineralized coatings of long-chain alkyl polymers. The resulting hierarchically structured aerogel exhibits low density (11.4 kg/m3), excellent mechanical compression properties across a wide temperature range (capable of enduring 100 cycles of compression), high porosity (99.2%), superhydrophobicity (152°), and recyclability. It maintains a 57.9% adsorption rate even after 40 adsorption–desorption tests, while also preserving its shape integrity. Moreover, it can be recycled and reused. At a temperature of 700 °C, the mass loss was only 44.47%, with excellent thermal stability. The aerogel can reduce oil pollutants in the ocean by adsorption, recover oil resources, and protect the natural environment. The assembly and optimization of nanofibrous matrix interfaces through the mineralization of long-chain polymers enhanced the performance of functionalized cellulose-based aerogels.

Diblock Copolymers of Methacryloyloxyethyl Phosphorylcholine and Dopamine Methacrylamide: Synthesis and Real-Time Adsorption Dynamics by SEIRAS and RAIRS.

Amphiphilic diblock copolymers containing a block of 2-methacryloyloxyethyl phosphorylcholine (MPC) with unique properties to prevent nonspecific protein adsorption and enhance lubrication in aqueous media and a block of dopamine methacrylamide (DOPMA) distinguished by excellent adhesion performance were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization for the first time. The DOPMA monomer with an acetonide-protected catechol group (acetonide-protected dopamine methacrylamide (ADOPMA)) was used, allowing the prevention of undesirable side reactions during polymerization and oxidation during storage. The adsorption behavior of the diblock copolymers with protected and unprotected catechol groups on gold surfaces was probed using attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy, surface-enhanced infrared absorption spectroscopy (SEIRAS), and reflection-absorption infrared spectroscopy (RAIRS). The copolymers pMPC-b-pADOPMA demonstrated physisorption with rapid adsorption and ultrasound-assisted desorption, while the copolymers pMPC-b-DOPMA exhibited chemical adsorption with slower dynamics but a stronger interaction with the gold surface. SEIRAS and RAIRS allowed proving the reorientation of the diblock copolymers during adsorption, demonstrating the exposure of the pMPC block toward the aqueous phase.

Perovskite-Derivative Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO3 perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N2 adsorption–desorption isotherms, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface.

Tyrosol removal by photo–Fenton–like process using CaAlFe mixed oxides synthesized via hydrocalumite from aluminum salt cake

Solids with potential application in tyrosol (Ty) removal by photo–Fenton processes have been synthesized using aluminum salt cake as a source. Two series of hydrocalumite layered double hydroxides (LDH) were synthesized: one containing structural Fe3+ (occupying octahedral positions in the LDH) and another containing surface impregnated Fe3+; all solids were calcined in air at 750 °C. The solids were characterized by powder X–ray diffraction, FT–infrared spectroscopy, thermal analysis, N2 adsorption–desorption isotherms at –196 °C, particle size distribution and electron microscopy. One of the main differences between the two series was that Fe3+ impregnation by the incipient wetness method and subsequent calcination at 750 °C did not lead to the formation of CaAlFe mixed oxides. The calcined solids were evaluated as photocatalysts in the photo–Fenton process for Ty removal (a typical compound found in olive oil mill wastewater), the samples containing surface Fe3+ showing better results. The solid prepared by impregnation of hydrocalumite with 20% iron and subsequently calcined at 750°C, under the optimum reaction conditions (catalyst dose = 0.5 g/L, [H2O2] = 0.468 g/L and [Ty]0 = 100 mg/L, in the presence of UV light), reached complete Ty removal with contaminant mineralization of 95% after only 60 min reaction. The cyclic study showed that this sample maintained its stability after 3 cycles of reuse without iron leaching, and a better performance than other materials reported in the literature.

Fabrication of porous beta-cyclodextrin functionalized PVDF/Fe–MOF mixed matrix membrane for enhanced ciprofloxacin removal

Herein, we demonstrate the synthesis of beta-cyclodextrin (β–CD) functionalized polyvinylidene fluoride (PVDF) and iron-based metal-organic framework (Fe–MOF) mixed matrix membrane (MMM) for the enhanced removal of ciprofloxacin (CIP) from water. The membranes were prepared using the phase inversion technique with PVDF as the polymer matrix, Fe–MOF as the filler, and polyvinylpyrrolidone (PVP) as the porogen. The optimized MMM with 7% wt. Fe–MOF exhibited excellent performance with 87.6% removal efficiency. Moreover, the maximum adsorption capacity was 6.43 mg g–1. The β–CD functionalization improved the MMM hydrophilicity exhibited by the water contact angle (WCA) analysis (WCA = 55°). Furthermore, excellent adsorption performance can be attributed to the large Fe–MOF specific surface area (682.5 m2 g–1), the high porosity (77%), and the average pore diameter (395 nm) of the membrane. The inclusion of PVP (1% wt.) enhanced the porous nature of the MMM and, consequently, the adsorption performance for CIP. Notably, the hydrophilic and macroporous membrane showed good reusability with over 70% removal efficiency after five sequential adsorption–desorption cycles. The insights from this study suggest that the PMC–7 membrane can be an excellent candidate for the remediation of organic contaminants from aquatic environments.

Adsorption–desorption characteristics of coal-bearing shale gas under three-dimensional stress state studied by low field nuclear magnetic resonance spectrum experiments

The micro-scale gas adsorption–desorption characteristics determine the macro-scale gas transport and production behavior. To reveal the three-dimensional stress state-induced gas adsorption–desorption characteristics in coal-bearing shale reservoirs from a micro-scale perspective, the coal-bearing shale samples from the Dongbaowei Coal Mine in the Shuangyashan Basin were chosen as the research subject. Isothermal adsorption–desorption experiments under three-dimensional stress state were conducted using the low field nuclear magnetic resonance (L-NMR) T2 spectrum method to simulate the in-situ coal-bearing shale gas adsorption–desorption process. The average effective stress was used as the equivalent stress indicator for coal-bearing shale, and the integral of nuclear magnetic resonance T2 spectrum amplitude was employed as the gas characterization indicator for coal-bearing shale. A quantitative analysis was performed to examine the relationship between gas adsorption in coal-bearing shale and the average effective stress. And a quantitative analysis was performed to examine the relationship between the macroscopic and microscopic gas quantities of coal-bearing shale. Experimental findings: (1) The adsorption–desorption process of coal-bearing shale gas follows the L-F function model and the D-A-d function model respectively with respect to the amount of gas and the average effective stress. (2) There is a logarithmic relationship between the macroscopic and microscopic gas quantities of coal-bearing shale during the adsorption–desorption process. This quantitatively characterizes the differences in the curves, which may be related to the elastic–plastic deformation, damage and fracture of the micropores in coal-bearing shale, as well as the hysteresis of gas desorption and the stress field of the gas occurrence state.

Hexavalent chromium ion removal from wastewater using novel nanocomposite based on the impregnation of zero-valent iron nanoparticles into polyurethane foam

In this study, we developed a novel nanocomposite, polyurethane foam impregnated with zero-valent iron nanoparticles (PU@nZVI), for the effective removal of chromium(VI) from various water sources. The characterization of nanocomposite (PU@nZVI) was performed by XRD, SEM–EDS, TEM and FT-IR techniques. Using the response surface methodology, we optimized the removal conditions, achieving an optimal pH of 2 and a dose of 0.5 g/L. The PU@nZVI demonstrated an excellent maximum adsorption capacity of 600.0 mg/g for Cr6+. The adsorption kinetics and isotherms were best described by the pseudo-second-order model and the Freundlich isotherm, respectively. Significantly, the nanocomposite removed 99.98% of Cr6+ from tap water, 96.81% from industrial effluent, and 94.57% from treated sewage wastewater. Furthermore, the PU@nZVI maintained its efficiency over five adsorption–desorption cycles, highlighting its reusability. These results suggest that the PU@nZVI nanocomposite is a highly efficient and sustainable option for chromium(VI) removal in water treatment applications.

Construction of SU-102 for adsorption and photocatalytic synergistic removal of tetracycline.

Tetracycline (TC) is a significant group of broad-spectrum antibiotics that are frequently employed in medical health and animal husbandry. However, the problem of TC residues has been increasing globally with the large-scale production and widespread use, posing a serious threat to the human health and ecological environment. In this paper, a green plant-based MOF SU-102 was prepared, and the adsorption characteristics of SU-102 on TC were investigated. SU-102 was columnar crystal with considerable specific surface area and pore structure, and it could adsorb TC quickly and effectively. And compared to SU-102-a, the adsorption rate of TC by SU-102-b has increased by nearly four times. The adsorption reaction was a spontaneous, entropy-gaining, heat-absorbing process. The adsorption mechanisms between SU-102 and TC were π-π interaction and hydrogen bonding. In addition, SU-102 also had considerable photocatalytic properties, and its application in adsorbent desorption treatment effectively solved the problem of secondary pollution.

Surface coverage ratio of contaminated Taylor bubbles in a square microchannel

Experiments on contaminated Taylor flows in a microchannel were carried out to investigate the surface coverage ratio for different surfactant properties. Nitrogen and water were used for the gas and liquid phases, respectively. Triton X-100, sodium dodecyl sulfate (SDS) of 90% purity and SDS of 99% purity were used as surfactant. The cross section of the microchannel was square and its width was 200μm. The gas and liquid volumetric fluxes were 0.54 and 0.50 m/s, respectively. Taylor flows were formed by mixing the two phases at the T-junction. Shapes of Taylor bubbles were observed using a microscope and a high-speed video camera. The liquid film thickness changed in the film region, demonstrating that a steep gradient of the interfacial surfactant concentration was formed there. The interface was therefore separated into the clean interface region and the immobilized region by detecting the change in the liquid film thickness. The surface coverage ratio estimated from bubble shapes agreed with that measured from the reduction in the bulk concentration due to surfactant separation by bubbles. The surface coverage ratio increased with increasing the bulk concentration and the increasing rate was smaller than that for the adsorption–desorption equilibrium because of the presence of interfacial advection. The data, however, could be fitted by modifying the functional form for the ad-desorption equilibrium. The bulk concentration normalized by the concentration for the breakdown of the logarithmic relation between the surface tension and the concentration given by the isotherm worked for correlating the surface coverage ratio for the three different surfactants, which can be understood from the order of magnitude of the Marangoni stress.

Preparation of hollow carbon nanospheres from oxidation of spent tyre oil‐derived carbon black in air

AbstractHollow carbon nanospheres (HCNS) were prepared from carbon black (CB) derived from spent tyre pyrolysis oil. The pristine CB produced by partial oxidation of the pyrolysis oil in a drop tube furnace was subsequently oxidised in air in a fixed bed reactor to yield HCNS. The effect of oxidation temperature (300 to 700°C) and time (1 to 8 h) on the burn‐off (Bt) of the sample over the duration (t) of oxidation and average reaction rate (Rt) was assessed. The BET surface area and pore volume and the nanostructure of the HCNS samples obtained were characterised using N2 adsorption–desorption and high‐resolution transmission electron microscope (HRTEM) techniques, respectively. Higher temperature and longer oxidation time led to higher Bt. As Bt increased, the BET surface area and pore volume initially increased linearly due to the removal of the amorphous core and then decreased because of the collapse of the shell of the carbon nanostructure. At Bt of ~56%, the maximum BET surface area and pore volume of the HCNS were 383.2 m2 g−1 and 0.39 cm3 g−1, respectively, compared to ~19.5 m2 g−1 and 0.033 cm3 g−1 of the pristine CB. The HRTEM images indicate that the change in BET surface area corresponds to the formation of the HCNS, as the core of the CB particle was preferentially consumed to create a hollow structure. The formation of HCNS follows an internal oxidation model, which is characterised by rapid core consumption and relatively slow shell consumption.

A novel magnetic geopolymer-based adsorbent prepared from heated glauconite and separated magnetite: Experiments and statistical physics treatment for crystal violet

Sinai copper ore with 9.48 % of Fe2O3 was treated using a laboratory-scale mineral processing techniques that included size reduction (below 75 µm) and a wet low intensity drum-type magnetic separation. After this treatment method, the separated magnetite product containing about 85 % of Fe2O3 was extracted. A mixture of heated glauconite (900 °C/2h) and the extracted magnetite was activated by sodium silicate (Na2SiO3) to obtain a novel glauconite-based magnetic geopolymer (namely GMG). Several analytical techniques (i.e., XRD, XRF, FESEM, FTIR, EDX, TEM, elemental mapping, and zeta potential) were used in the characterization of GMG and its performance for crystal violet (CRV) remediation was studied. The equilibrium data at pH 8.0 and 25 – 50 °C were fitted to a statistical physics multilayer model and classical isotherm equations to understand the CRV adsorption mechanism. The theoretical calculations indicated that GMG can adsorb 1.12 to 1.39 of CRV molecules per functional group (n), suggesting the presence of a multi-interaction mechanism and vertical adsorption orientation on GMG surface. For this basic dye, the estimated saturation adsorption capacities (Qsat) ranged from 684 to 612 mg/g, and an exothermic binding interaction was associated with the removal of this dye molecule. The adsorption energies (ΔE) ranged between 15.05 and 36.74 kJ/mol, indicating that physical forces, such as electrostatic interactions and hydrogen bonds, governed the GMG-CRV interactions. After fourth adsorption–desorption cycles, the regenerated GMG showed 74 % of its adsorption capacities, which suggested the suitability of this adsorbent to be regenerated and reused multiple times in water treatment. Overall, the combination between the separated magnetite and glauconite was an effective approach for the remediation of effluents that contain dye molecules

Immobilization of Schiff base-Pd complex in mesoporous silica KIT-6 channels: A novel, green, recyclable, and highly versatile mesoporous catalyst for the carbon-carbon cross-coupling reaction

In this study, we developed an efficient and novel nanocatalyst by immobilizing Schiff base-Pd complex inside mesoporous silica KIT-6 channels, which were successfully synthesized by using a simple procedure. The catalytic activity of KIT-6@Schiff base-Pd was investigated in the synthesis of a wide variety of biphenyl derivatives. The N2 adsorption–desorption isotherms indicated the excellent Brunauer–Emmett–Teller surface area for KIT-6@Schiff base-Pd of 121.65 m2/g. The chemical and physical properties of raw and modified samples (KIT-6@Schiff base-Pd) were characterized based on Fourier transform-infrared spectra, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, N2 adsorption–desorption, scanning electron microscopy, X-ray elemental mapping, and X-ray diffraction analyses. We found that the synthesized catalyst could be recovered and reused up to four times.

Methionine-stevensite derived bionanocomposite: A green and efficient adsorbent for the removal of antibiotics

The persistent appearance of antibiotic residues in the aquatic ecosystem is considered an issue of great concern. This study examined the adsorptive efficiency of a novel bionanocomposite (L-methionine/stevensite, MET/ST) for promising decontamination of nine antibiotics. Results revealed that MET/ST allows an excellent antibiotic removal efficiency, from 87% for trimethoprim (TMP) to almost 100% for the eight remaining antibiotics, at neutral pH, an adsorbent dose of 2 g/L, and 1.5 mg/L of the antibiotics mixture. Equilibrium was achieved in less than 1 min, except for TMP (30 min), and the kinetics was consistent with the pseudo-second order model (R2 > 0.927). The isotherm data were fitted with the Langmuir and Freundlich models (R2 > 0.960) (qmax from 21.48 to 28168 mg/g for TMP and chlortetracycline, respectively). The high surface area (170.49 m2/g) and pore volume (0.16 cm3/g) of MET/ST, together with electrostatic and hydrogen bonding interactions, played a dominant role in antibiotic adsorption. TMP was the only antibiotic affected by temperature (from 61% to 85% at 5 and 45ºC) and salinity (from 87% to 37% at 0 and 4% w/v of NaCl). The MET/ST was used consecutively for at least four adsorption–desorption cycles after being regenerated with a capacity > 97% in the last cycle for 7 out of 9 antibiotics. In addition to its adsorption capacity, reusability and low-cost features, the material demonstrated an excellent efficiency (up to 69% for TMP and 100% for other antibiotics) in wastewater and surface water samples denoting a great application for water purification.

A novel preparation of microporous nanosilica derived from aluminum-extracted residue of coal fly ash for highly selective CO2 adsorption

Currently, the poor adsorption performance caused by the unsatisfactory pore size seriously restricts the further development of microporous nanosilica (MS). Herein, an excellent microporous nanosilica was constructed by preparing calcium silicate hydrate (CSH) support from the aluminum-extracted residue of coal fly ash and modifying it with different activating agents (H2SO4, HNO3, HCl, CH3COOH, KOH, NaOH and Na2CO3). The results indicated that CH3COOH at 30 wt% was the optimal modifier, achieving a CO2 uptake of 1.42 mmol/g at 298 K and 1.0 bar. Then the effects of synthesis parameters including mass fraction, liquid–solid ratio, temperature, and time on the adsorption capacity of CO2 were further investigated. The obtained MSCp exhibited a high specific surface area (up to 505.71 m2/g), well-developed microporosity (0.085 cm3/g), and excellent CO2 uptake (2.12 mmol/g at 273 K, 1.41 mmol/g at 298 K). Based on the study of kinetics, isosteric heat of adsorption (Qst), and situ diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS), the adsorption mechanism of MSCp was determined to be mainly physical adsorption. Besides, the excellent CO2/CH4 selectivity of 20.91 (15/85, v/v) and 30.75 (50/50, v/v), CO2/N2 selectivity of 53.79 (15/85, v/v) and 163.76 (50/50, v/v) were obtained from MSCp at 298 K and 1.0 bar. Finally, the binary gas breakthrough experiments and eight adsorption–desorption cycles confirmed the MSCp was suitable for selective adsorption of CO2 in practical applications.