Mesopore Diameter Research Articles

Composites of mesoporous silica precipitated on nanofibrillated cellulose and microfibrillated cellulose: Effect of fibre diameter and reaction conditions on particle size and mesopore diameter

Composites of MSNs (mesoporous silica nanoparticles) with nanofibrillated cellulose (NFC) and microfibrillated cellulose (MFC) were synthesized via in-situ precipitation. Controlling particle size distribution (PSD), pore diameter, and pore volume of mesoporous silica nanoparticles (MSNs) by cellulose nanofiber size has been investigated. In-situ precipitation on the 19 nm median diameter of NFC fibres produces MSNs in the diameter range 20–30 nm, the smallest MSN size reported. MSNs precipitated on MFC fibres with a 26 nm median diameter are 37% larger with broader size distribution, larger mesopore diameters, and lower specific surface area. The pore volume of MFC-MSNs composite was due to internal mesopores of MSNs and among particles and fibres, while it was primarily because of mesopores within MSNs in NFC-MSNs composite. Particle diameters were unaffected by varying the molar ratio of cellulose: TEOS (tetraethoxysilane) and reaction time. The reaction was mostly complete within only 10 min. The best NFC-MSN composite displayed a specific surface area of 567 m2/g with a saturated adsorption capacity of 134 mg/g of methylene blue (MB).

Fabrication of centimeter-sized Sb2S3/SiO2 monolithic mimosa pudica nanoflowers for remediation of hazardous pollutants from industrial wastewater

Photocatalysis using ‘easy-to-separate’ metal-oxide/sulfide monoliths is a promising method to tackle the grievous issue of water pollution. Here, ‘mimosa pudica’ flower-like Sb2S3/SiO2 monoliths were prepared by impregnation of antimony chloride solution in silica monoliths followed by treatment with potassium thiocyanate, refluxing and calcination. The nanoflower-like morphology of the synthesized monoliths was verified using field emission scanning electron microscope images. The Brunauer–Emmett–Teller model for surface area analysis showed that monoliths had a high surface area of 83 m2/g with mesopore diameter of 13.61 nm. The purity/crystallinity and the elemental state of the sulfide were confirmed using X-ray diffraction analysis and X-ray photon spectroscopy whereas energy dispersive spectroscopy verified the homogeneous elemental distribution of the catalyst. The diffuse reflectance spectroscopy and photoluminescence spectroscopy confirmed that Sb2S3/SiO2 monoliths had a narrow band gap (∼1.57 eV) and low recombination rate of photoinduced charge carriers. Thermal stability of the materials was also investigated by thermogravimetric analysis. The photocatalytic performance of monoliths was examined by photodegradation of model pollutants methylene blue (MB) and thiamethoxam (TM). At optimum pH and catalyst-concentration, monoliths exhibited best efficiency (with high rate-constant) in sunlight for degradation of MB (96%; 0.018 min−1) and in UV light for degradation of TM (70%; 0.0057 min−1). The catalyst was reused for four cycles for degrading MB (∼71% efficiency). A comparative study with reported literature data confirmed the superiority of the monoliths for MB degradation. The trapping experiments indicated that superoxide anion radicals and holes had a dominant role in the MB and TM degradation, respectively. MB was mineralized almost completely exhibiting ∼99.7% removal of total organic carbon (TOC). The photocatalytic treatment of industrial wastewater revealed ∼97% TOC- removal besides ∼92% removal of chemical oxygen demand. It validated that this photocatalyst is better than physicochemical treatment done by industries. This monolithic catalyst can indeed be advantageous for the remediation of perilous contaminants from a practical viewpoint.

A Novel Anthraquinone‐Containing Poly(Triphenylamine) Derivative: Preparation and Electrochemical Performance as Cathode for Lithium‐Ion Batteries

AbstractOrganic and polymeric materials are excellent candidates for next generation advanced electrode materials. Therein, 2,6‐Bis(4‐(diphenylamino)phenyl)‐9,10‐anthracenedione (BDAPA) functional monomer was synthesized through Suzuki coupling reaction, and a novel anthraquinone‐containing poly(triphemylamine) polymer (PBDAPA) was then prepared by the simple oxidative polymerization. The obtained novel functional polymer presented a unique urchin‐like morphology with outgrowth of hollow tubular spiny, which possesses the improved specific surface area of ∼129.6 m2 g−1 and the small average mesopore diameter of 1.78 nm. As cathode material, the obtained PBDAPA compared to polytriphenylamine (PTPA), demonstrated two obvious discharge plateaus, corresponding to the double charge‐discharge characteristics from p‐type triphenylamine and n‐type anthraquinone segments in the polymer, respectively. Also, PBDAPA exhibited an improved specific capacity of 132.7 mAh g−1 and an enhanced rate capability with the discharge specific capacities of 140.6, 124.3, 107.5 and 97.1 mAh g−1 at the discharge rates of 20, 50, 100 and 200 mA g−1, respectively. The introduction of anthraquinone unit in polytriphenylamine as well as the resulted open pore morphology for PBDAPA was responsible to the improved electrochemical performances, which makes it a potential strategy for the design and preparation of high performance organic lithium‐ion batteries.

CuO supported on COK-12 and SBA-15 ordered mesoporous materials for temperature swing SOx adsorption

Ordered mesoporous SBA-15 and COK-12 supports with similar mesopore diameter were loaded with 15 wt% of CuO and evaluated as adsorbents in a desulfurization process involving SOx adsorption and regeneration. Both SBA-15 and COK-12 have a hexagonal arrangement of parallel tubular mesopores. The impact of relatively small differences of the structural and textural properties of the two supports on SOx adsorption and regenerability is investigated. After impregnation with copper nitrate solution and calcination at 500 °C, the samples do not show any characteristic XRD pattern of copper-based phases, confirming the highly dispersed state of CuO, which is also checked by Transmission Electron Microscopy (TEM). The COK-CuO15 sample has slightly higher porosity than the SBA-CuO15 sample. The pore volume of both supports is slightly reduced after impregnation-calcination and shaping (Pelletized, Crushed and Sieved – PCS) steps. As for its SOx adsorptive properties, after fifteen adsorption-regeneration cycles at 400 °C, the COK-CuO15_PCS sample exhibits dynamic and total adsorption capacities higher than those of the SBA-CuO15_PCS adsorbent. In addition, both adsorbents preserve their adsorption capacities over the 15 cycles. The COK-12 support for the CuO active phase provides very promising results in comparison with the literature data for SBA-CuO15 adsorbent.

Impact of γ-alumina pore structure on structure and performance of Ni–Mo/γ-Al2O3 catalyst for 4,6-dimethyldibenzothiophene desulfurization

The pore structure plays a vital role in material properties. Therefore, in this study, we prepared γ-Al2O3 with various mesopore diameters to explore the impact of pore structure on the property of Ni–Mo/γ-Al2O3 catalyst and hydrodesulfurization of 4,6-dimethyldibenzothiophene. It reveals that the pore size adjusts the reducibility of Mo species via affecting ammonium heptamolybdate adsorption. The Ni benefits the dispersion and reduction of Mo species. The larger pore imparts weaker polarization of Al3+, which less weakens the interactions between the MoS2 layers. The different polarization of Al3+ results in the diverse Ni–Mo–S structures over the catalysts with various pore sizes, and different active sites in edges and corners are obtained. The optimum pore size of Ni–Mo/γ-Al2O3 catalyst for the desulfurization of 4,6-dimethyldibenzothiophene is 7.0 nm, rather than 5.9 nm for the MoO3/γ-Al2O3 catalyst. The reaction pathway is regulated by the pore size and Ni–Mo–S structure. 4,6-dimethyldibenzothiophene reacts mainly via the hydrogenation pathway over 4.5 nm pore sized catalyst and high edge to corner ratio of the Ni–Mo–S slab (e.g. 2.63). Whereas, the sulfur in 4,6-dimethyldibenzothiophene is preferably eliminated by the direct desulfurization pathway in the pore size of 8.7 nm and low edge to corner ratio of the Ni–Mo–S slab (e.g. 2.04). All these can also be used to design deep desulfurization catalyst for environmental protection.

Lattice Boltzmann simulation of multicomponent reaction-diffusion and coke formation in a catalyst with hierarchical pore structure for dry reforming of methane

In order to further enhance catalytic activity and inhibit carbon formation, the hierarchical structure-performance relationship has been investigated in dry reforming of methane (DRM). A modified random generation of macro-mesopores (RGMMP) algorithm was adopted to model the structure of the catalyst with macropore and mesopore. Based on multi-component non-continuum reaction-diffusion lattice Boltzmann model, the effects of three hierarchical pore geometrical parameters, namely the catalyst porosity, the ratio of mesopore volume to macropore volume and the ratio of average macropore diameter to average mesopore diameter, on coke formation and catalytic performance were investigated to elucidate the deactivation and reaction-diffusion mechanism of the catalyst in DRM. Based on the competitive relationship between heterogeneous reaction and intraparticle diffusion, the optimal values to define hierarchical pore structure have been identified, which provides maximum catalytic performance and coking resistance for a reaction condition.

Study of secondary porosity by SAXS and N2 adsorption in composite materials obtained from a Cuban natural clinoptilolite

In this work, a study of the secondary porosity of two zeolite‐based composites is carried out by small angle X‐ray scattering (SAXS) and N2 adsorption at 77 K. The composites were obtained by the inclusion of ZnO nanoparticles in a Cuban natural clinoptilolite by mechanosynthesis and ‘in situ’ methods. It was observed a decrease in the specific surface area as a result of ZnO nanoparticles inclusion from 149 m2 g−1 in the started material to 60 m2 g−1 in the composite prepared by in situ method, whereas the mesopore diameter remained almost constant. The results confirmed the presence of mesopores with diameter between 3 and 36 nm, with good match by both methodologies. These materials were developed in view of their future application as catalysts and adsorbents, where the presence of secondary porosity is key to favor the diffusion processes.

Mesoporous cobalt‑iron based materials as highly efficient electrocatalysts for oxygen evolution reaction

The cost-effective and high-performance electrocatalysts toward oxygen evolution reaction (OER) have been a research hotspot for the electrochemical water splitting. In view of the unique surface effect and good electrical conductivity, mesoporous nanomaterials have been a promising alternative to the precious RuO2 for OER. Herein, two mesoporous CoFe-based nanomaterials were designed and synthesized through a facile solvothermal process as efficient OER electrocatalysts in 1.0 M KOH solution. The catalysts with a larger pore size show more excellent catalytic performance, which possess a lower overpotential of 248 mV at 10 mA·cm−2 and a Tafel slope of 58.7 mV·dec−1, illustrating an increase of catalytic activities toward OER with the enhancement of mesoporous pore diameters. This work also contributes to the development of OER nanomaterials and the understanding of the effects of mesoporous on catalytic activity.

Mechanistic insights and consequences of intrapore liquids in ethene, propene, and butene dimerization on isolated Ni2+ sites grafted within aluminosilicate mesopores

The stability, selectivity, and reactivity conferred by intrapore liquids onto Ni2+ species grafted within mesoporous aluminosilicates for the dimerization of C2-C4 alkenes are reported and interpreted by the preferential stabilization of dimer desorption transition states, which inhibit further growth during the surface sojourn that forms these dimers. The marked decrease in deactivation rate constants leads to catalyst half-lives > 600 h for all alkenes and to turnover rates (per Ni) at sub-ambient temperatures (240–260 K) that exceed those at the higher temperatures previously used for Ni-based solid catalysts (350–500 K). These effects appear at the relative pressures required for alkene capillary condensation within Ni-Al-MCM-41 catalysts with different mesopore diameters and are also evident when the intrapore liquids consist of unreactive alkanes, indicative of solvation effects conferred by non-covalent interactions mediated by dispersion forces. For all alkenes, turnover rates (per Ni) are unaffected by Ni content until each acidic proton in the Al-MCM-41 is replaced by one Ni atom, consistent with the involvement of grafted (Ni-OH)+ monomers as active centers and excess Ni leading to inactive NiO species. The stable nature of these catalysts allows accurate mechanistic assessments and a demonstration of the kinetic relevance of the CC coupling elementary steps on essentially bare (Ni-OH)+ centers, leading to rates described by second-order dimerization constants (αn′) and adsorption constants (βn′) for each alkene (Cn); these parameters are influenced only slightly by intrapore liquids, because they reflect free energies of formation of surface-bound species and transition states from gaseous precursors. These αn′ and βn′ parameters increase with alkene size, with the enthalpic component of αn′ increasing from 21 to 46 kJ mol−1 and the activation entropy becoming more negative (−103 to −187 J (mol K)−1), consistent with CC coupling transition states that occur late along the reaction coordinate and resemble its bound dimer product. The low C3n/C2n ratios observed in the presence of intrapore liquids (<0.04, for n = 2–4) reflect the endothermic nature of dimer desorption events, for which product-like transition states benefit from the solvation of desorbing products by a non-polar liquid phase, thus allowing detachment from Ni centers before subsequent growth. The inhibition of such growth events accounts not only for the unique dimer selectivity observed, but also for the unprecedented stability conferred by intrapore liquids by inhibiting the formation of oligomers that bind more strongly with increasing chain size, as evident from the βn′ values reported here for alkene reactants.

Highly selective hierarchical ZSM-5 from kaolin for catalytic cracking of Calophyllum inophyllum oil to biofuel

Upgrading the inferior properties of Calophyllum inophyllum oil via catalytic cracking into biofuel required a porous heterogeneous acid catalysts. Hierarchical ZSM-5 (Hi-ZSM-5(K)) produced from desilication of kaolin-derived ZSM-5 was employed as catalyst and the activity was compared with hierarchical ZSM-5 obtained from templating method (Hi-ZSM-5(T)). Catalytic cracking of Calophyllum inophyllum oil was carried out in one-pot reaction at 475 °C for 120 min under the flow of H2 and the products analysed using GC-MS were consisted of the mixtures of alkane, alkene, oxygenated carbon and aromatics compound. The advantages of desilication method for the formation of highly selective hierarchical ZSM-5 was observed when the catalyst exhibited enhanced acidity with mesopores diameter of 2–5 nm to give 93% conversion and high selectivity towards light C7–C9 hydrocarbons. However, Hi-ZSM-5(T) showed low acidity to give only 43% conversion, and selectivity towards C11–C12 hydrocarbons due to the mesopores diameter of 3–12 nm. The activity of hierarchical ZSM-5 was also compared with microporous ZSM-5 that produced biofuel with approximately equal distribution of C5–C18 hydrocarbons. The role of hierarchical structures was further discussed on the composition of aromatics compound, oxygenates content and alkene/alkane ratios of the biofuel.

Effect of water intrusion on the characteristics of surface morphology and pore fracture spaces in argillaceous meagre coal

Dry coal samples and coal samples with different water invasion times (DWITs) were prepared, and X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and low-pressure nitrogen adsorption (LPNA) experiments were carried out to analyze the pore fracture volume and distribution. The fractal dimension of the aperture surface was calculated with the MIP and LPNA data of these coal samples. We found that the pore diameter of macropores decreases, and the fractal dimensions of macropores and mesopores change greatly, on the score of the dispersion of clay minerals and clay expansion; in addition, water intrusion has little effect on the pore size and fractal dimension of minipores and micropores with increasing water invasion time. We conclude that long-term water invasion greatly damages the pore diameter and surface morphology of macropores and mesopores and reduces the permeability of the fractures in coal seams. Long-term water invasion causes little damage to the pore diameter and surface morphology of minipores and micropores. Water plays an important role in sealing off gas and competing for gas adsorption position in minipores and micropores. In addition, by combining the fractal dimension data of MIP and LPNA, we found that water invasion for 20 days was an effective time point to change the pore structure and surface morphology of coal particles. We anticipate that the research conclusions could save coal seam water injection time, and the conclusions could improve the efficiency of natural gas extraction and improve coal and gas outburst prevention engineering.

Copper-doped Ordered Mesoporous Bioactive Glass: A Promising Multifunctional Platform for Bone Tissue Engineering †.

The design and development of biomaterials with multifunctional properties is highly attractive in the context of bone tissue engineering due to the potential of providing multiple therapies and, thus, better treatment of diseases. In order to tackle this challenge, copper-doped silicate mesoporous bioactive glasses (MBGs) were synthesized via a sol-gel route coupled with an evaporation-induced self-assembly process by using a non-ionic block co-polymer as a structure directing agent. The structure and textural properties of calcined materials were investigated by X-ray powder diffraction, scanning-transmission electron microscopy and nitrogen adsorption-desorption measurements. In vitro bioactivity was assessed by immersion tests in simulated body fluid (SBF). Preliminary antibacterial tests using Staphylococcus aureus were also carried out. Copper-doped glasses revealed an ordered arrangement of mesopores (diameter around 5 nm) and exhibited apatite-forming ability in SBF along with promising antibacterial properties. These results suggest the potential suitability of copper-doped MBG powder for use as a multifunctional biomaterial to promote bone regeneration (bioactivity) and prevent/combat microbial infection at the implantation site, thereby promoting tissue healing.

Enzymatic monolithic reactors for micropollutants degradation

Silica monoliths with uniform macro-/mesoporous structures (20 μm and 20 nm macro- and mesopores diameters, respectively), high porosity (83 %) and high surface area (370 m2 g−1) were prepared. The monoliths were grafted with amino groups (0.9 mmol NH2 g−1) and used to immobilize laccase from Trametes versicolor by covalent grafting with glutaraldehyde (GLU) (1.0 mmol GLU g−1) leading to an ABTS activity of 20 U g−1. Immobilization yield was 80 %, based on the difference of initial and final activity of enzymatic solution used for immobilization. Enzymatic monoliths were used for the degradation of tetracycline (TC) in aqueous solution (20 mg L−1) in continuous flow with recycling configuration. TC degradation efficiency was found to be 40–50 % after 5 h of reaction at pH 7. Enzymatic monoliths were used during 75 h of sequential operation without losing activity. A Steady-state computational fluid dynamics (CFD) model based on Michaelis Menten reaction kinetics, allowed computing TC degradation efficiency.

Colorimetric cutoff indication of relative humidity based on selectively functionalized mesoporous silica

We present a novel – cutoff concept of colorimetric indication of relative humidity based on dye dissolution in condensed water in capillaries of selectively functionalized mesoporours host SiO2 material. Consistently high levels of indoor air humidity induces mold and algae growth which represent a potential risks for human health and have deteriorating effect on walls as well. Simple localized humidity detection of high humidity with naked eye especially at places with low air circulation, where growth of mold usually starts first, is therefore highly desirable. The reporting dye was integrated in the non-functionalized mesoporous silica matrix with different pore diameters and selective-functionalized mesoporous silica material. After exposure to the environment of different air humidities the dye dissolved in water causing color change of adsorbent. With the use of adsorbents with different mesopore diameters high ability to tune the value of relative humidity when complete capillary condensation occurred was achieved. Materials with pore diameters of 3.0 nm, 3.5 nm and 7.0 nm exhibit gradual color change when reaching relative humidity up to 55, 79 and 88 RH % respectively. After selective methylation of the material with 7.0 nm pore diameter, non-gradual cutoff color change was achieved. Sample exhibited color change at narrow range of relative humidity (cutoff color change). Due to selective functionalized outer surface the dye dissolution occur only in condensed water in pores and therefore provide colorimetric indication only in this range. Selectively modified silica material has a great potential for a straightforward detection of high humid environment.

Macropore-assisted electrolyte transfer inside binder-free templated carbon xerogels as carbon electrode for electric double layer capacitors

Capacitive performance of electric double layer capacitors is influenced by specific surface area, while pore structure also promotes electrolyte transfer inside a carbon electrode. Organic electrolytes require macropores, whereas aqueous electrolytes operate best using mesopores for electrolyte transfer. Templated carbon xerogels (TCXs) were prepared from resorcinol and formaldehyde with cotton fibers as a hard template containing macropores, mesopores and micropores as the carbon electrode. Results suggested that macropores (>50 nm) were contiguously created and connected with mesopore diameters (2–50 nm), leading to convenient ion transport inside the TCXs. Vacuum drying formed sponge-like carbon xerogels that permitted electrolyte transfer. Despite the insignificant change of porous properties, TCXs possessing sponge-like carbon xerogels showed increased capacitance values from 137 F/g to 317 F/g at 200 mA/g in a three-electrode system as a result of macropore-assisted electrolyte transfer in aqueous electrolytes.

Enzymatic Degradation of Micropollutants in Water: the Case of Tetracycline Degradation by Enzymes Immobilized on Monoliths

Enzymatic monolithic reactors were applied for the degradation of micropollutants through flow-through reactor configuration. Silica monoliths with uniform macro-/mesoporous structures (20 µm and 20 nm macro- and mesopores diameters) high porosity (83%) and high surface area (370 m2 g-1) were prepared. The monoliths were cladded in steel tubing and laccase from Trametes versicolor was immobilized by covalent grafting. Enzymatic monoliths presented a very good oxidation activity and were used for the degradation of tetracycline (TC) in aqueous solutions in a tubular plug reactor with recycling configuration. TC degradation efficiency was found to be 40-50 % after 5 h of reaction at pH 7. The immobilized laccase on silica monoliths exhibited high operational stability during 75 hours of sequential operation.

Polar mesoporous zinc sulfide nanosheets encapsulated in reduced graphene oxide three-dimensional foams for sulfur host

Lithium-sulfur (Li-S) batteries exhibit the high specific capacity and energy density, but prevented by the low coulombic efficiency and weak cycle life. Herein, we fabricate reduced graphene oxide (r-GO) three-dimensional (3D) foams encapsulating polar mesoporous zinc sulfide (ZnS) nanosheets and subsequently utilize the ZnS/r-GO foams to load sulfur (ZnS/r-GO/S) as cathodes for improving the performance of Li-S batteries. The mesoporous diameter of the ZnS nanosheets is approximately 10~30 nm and lots of pores in the 3D foams are observed. The porous structure provides abundant sites to adsorb and accommodate sulfur species. The cathode of the ZnS/r-GO/S exhibits 1259 mA h g−1 of initial capacity and 971.9 mA h g−1 of the reversible capacity after 200 cycles at 0.1 C (1 C = 1675 mA g−1). At 1 C, it still exhibits the tiny capacity decay rate of 0.019% per cycle after 300 cycles. This work may be adopted to combine the nonpolar and polar materials as a 3D network structure for high-performance Li-S batteries.

Structural reversibility of Cu doped NU-1000 MOFs under hydrogenation conditions.

The metal-organic framework (MOF), NU-1000, and its metalated counterparts have found proof-of-concept application in heterogeneous catalysis and hydrogen storage among others. A vapor-phase technique, akin to atomic layer deposition (ALD), is used to selectively deposit divalent Cu ions on oxo, hydroxo-bridged hexa-zirconium(IV) nodes capped with terminal -OH and -OH2 ligands. The subsequent reaction with steam yields node-anchored, CuII-oxo, hydroxo clusters. We find that cluster installation via AIM (ALD in MOFs) is accompanied by an expansion of the MOF mesopore (channel) diameter. We investigated the behavior of the cluster-modified material, termed Cu-AIM-NU-1000, to heat treatment up to 325 °C at atmospheric pressure with a low flow of H2 into the reaction cell. The response under these conditions revealed two important results: (1) Above 200 °C, the initially installed few-metal-ion clusters reduce to neutral Cu atoms. The neutral atoms migrate from the nodes and aggregate into Cu nanoparticles. While the size of particles formed in the MOF interior is constrained by the width of mesopores (∼3 nm), the size of those formed on the exterior surface of the MOF can grow as large as ∼8 nm. (2) Reduction and release of Cu atoms from the MOFs nodes is accompanied by the dynamic structural transformation of NU-1000 as it reverts back to its original dimension following the release. These results show that while the MOF framework itself remains intact at 325 °C in an H2 atmosphere, the small, AIM-installed CuII-oxo, hydroxo clusters are stable with respect to reduction and conversion to metallic nanoparticles only up to ∼200 °C.

Impact of sugar beet seed priming using the SMP method on the properties of the pericarp

BackgroundThis study determined the effects of two solid matrix priming methods on changes in the characteristics of two lots of the same variety of sugar beet fruits that differ in the level of vigour.ResultsSeed treatment within each level of vigour did not significantly affect helium and apparent density, total pore volume and total porosity. However, there was a tendency to increase porosity due to priming. This is probably why seed priming significantly increased mesopore diameter in both high and low vigour seeds. These changes increased the water content in the pericarp and the seeds and increased the water potential during germination. The high level of electrical conductivity of the fruit extracts was associated with low seed vigour. Low vigour resulted in higher humidity of the pericarp and decreased seed moisture and was also associated with lower water potential of the pericarp and seeds.ConclusionsA significant difference in the water content in the pericarp and seeds was indicative of imbibition and problems with water flow between these centres, which resulted in a low water diffusion coefficient of the pericarp. This low water diffusion coefficient was correlated with the prolongation of the seed germination time.

Investigating Microcystin-LR adsorption mechanisms on mesoporous carbon, mesoporous silica, and their amino-functionalized form: Surface chemistry, pore structures, and molecular characteristics

Microcystin-LR (MC-LR) is the most common cyanotoxin released from algal-blooms. The study investigated the MC-LR adsorption mechanisms by comparing adsorption performance of protonated mesoporous carbon/silica (MC-H, MS-H) and their amino-functionalized forms (MC-NH2 and MS-NH2) considering surface chemistry and pore characteristics. The maximum MC-LR adsorption capacity (Langmuir model) of MC-H (37.87 mg/g) was the highest followed by MC-NH2 (29.25 mg/g) and MS-NH2 (23.03 mg/g), because pore structure is partly damaged during amino-functionalization. However, MC-NH2 (k2 = 0.042 g/mg/min) reacted faster with MC-LR than MC-H during early-stage adsorption due to enhancing electrostatic interactions. Intra-particle diffusion model fit indicated Kp,1 of MC-H (2.11 mg/g/min1/2) was greater than MC-NH2 due to its greater surface area and pore volume. Also, large mesopore diameters are favorable to MC-LR adsorption by pore diffusion. The effect of adsorbate molecular size on adsorption trend against MC-H, MC-NH2 and MS-NH2 was determined by kinetic experiments using two dyes, reactive blue and acid orange: MS-NH2 achieved the highest adsorption for both dyes due to the large number of amino groups on its surface (41.2 NH2/nm2). Overall, it was demonstrated that adsorption of MC-LR on mesoporous materials is governed by (meso-)pore diffusion and π – π (and hydrophobic) interactions induced by carbon materials; in addition, positively-charged grafted amino groups enhance initial MC-LR adsorption rate.