Formation Of Mesopores Research Articles

Water sorption studies with mesoporous multivariate monoliths based on UiO-66.

Hierarchical linker thermolysis has been used to enhance the porosity of monolithic UiO-66-based metal-organic frameworks (MOFs) containing 30 wt% 2-aminoterephthalic acid (BDC-NH2) linker. In this multivariate (i.e. mixed-linker) MOF, the thermolabile BDC-NH2 linker decomposed at ∼350 °C, inducing mesopore formation. The nitrogen sorption of these monolithic MOFs was probed, and an increase in gas uptake of more than 200 cm3 g-1 was observed after activation by heating, together with an increase in pore volume and mean pore width, indicating the creation of mesopores. Water sorption studies were conducted on these monoliths to explore their performance in that context. Before heating, monoUiO-66-NH2-30%-B showed maximum water vapour uptake of 61.0 wt%, which exceeded that reported for either parent monolith, while the highly mesoporous monolith (monoUiO-66-NH2-30%-A) had a lower maximum water vapour uptake of 36.2 wt%. This work extends the idea of hierarchical linker thermolysis, which has been applied to powder MOFs, to monolithic MOFs for the first time and supports the theory that it can enhance pore sizes in these materials. It also demonstrates the importance of hydrophilic functional groups (in this case, NH2) for improving water uptake in materials.

Flexible carbon nanofibers with multichannel and porous structure as freestanding anode for excellent sodium storage

Hard carbon is the most commonly used anode material for sodium-ion batteries (SIBs). However, it has the drawback of having inferior capacity at high rates due to low ion-diffusion kinetics. Rational design of hard carbon with a hierarchical pore structure and multichannel structure can address this issue. Herein, we introduced an electrospinning method for preparing flexible carbon nanofibers as a freestanding anode for SIBs. The pore structure can be modified by adjusting the amount of Pluronic F-127 (F127) added to the spinning solution. This strategy results in the formation of numerous micropores and mesopores, along with pore-derived defects, effectively increasing the number of sites available for sodium storage. The existence of multichannel facilitates the migration of sodium ions. PCNF-1 possesses an appropriate pore structure with the least amount of added pore-forming agent exhibits exceptional electrochemical performance. It delivers a reversible capacity of 286 mA h g−1 at a current density of 50 mA g−1 with an initial Coulombic efficiency (ICE) of 82 %. At 5 A g−1, it delivers a capacity of 211 mAh g−1. Furthermore, it demonstrates a high retention rate of 79 % at 1 A g−1 even after 1000 cycles. Notably, in full-cell tests, PCNF-1, when paired with a Na3V2(PO4)3 cathode, achieved a specific capacity of 253 mA h g−1 in the second cycle and maintained a retention rate of 51 % after 200 cycles at a current density of 1 A g−1.

Nitrogen/oxygen doped hierarchical porous carbon with adjustable pore structure for efficient adsorption, separation, and enhancement mechanism of methanol and acetone azeotropes: Experimental and theoretical study

The adsorption and separation of methanol and acetone are crucial for environmental protection and recycling. However, the separation of methanol and acetone azeotropes using carbon-based materials remains challenging, and the underlying mechanism is still unclear. Here, we propose the synthesis of porous carbon (NaOCs) using benzimidazole as a precursor and NaOH as an activator. With the increase of the proportion of NaOH and benzimidazole, the activation reaction was intensified, leading to the formation of numerous mesopores. NaOCs exhibit a maximum specific surface area (SBET) of 3084 m2/g, and has extremely high adsorption capacity of methanol (56.9 mmol/g at 13 kPa) and acetone (34.6 mmol/g at 18 kPa) at 25 °C. The results of experiments and molecular simulations indicate that the saturation adsorption capacity of methanol and acetone is determined by micropores and narrow mesopores at 25 °C, whereas the adsorption capacity at relatively low pressure is primary determined by ultramicropores and oxygen group. Furthermore, for methanol-acetone azeotropes separation, the acetone/methanol selectivity at low pressure depends on carbon surface polarity and ultramicropore, while methanol/acetone selectivity at high pressure depends on micropores of 1–2 nm. Our findings provide insights into the design and further development of adsorbents for VOCs adsorption and azeotrope separation applications.

Exploring soil water retention hysteresis in the entire suction range and microstructure evolution of loess: The influence of sediment depths

Sediment depths can influence both soil structure and hydraulic processes, resulting in diverse soil-water retention properties. This study aimed to investigate the impact of sediment depths on soil-water retention hysteresis across the entire suction range, as well as the microstructure evolution of loess during the drying-wetting cycle. Laboratory tests were conducted to achieve this objective. The test results demonstrated that the water retention properties of the natural loess were significantly affected by sediment depths over the entire suction range. And the tested samples shrank considerably due to drying, while the swelling curves were almost linear induced by the wetting. Besides, the commonly used four water retention models were adopted to fit the test data, and Zhou's model showed the best-fitting performance. Furthermore, the local degree of hysteresis in the low suction range was generally larger than that in the high suction range for all samples, and the minimum local degree of hysteresis corresponded to the in-situ suction of tested samples. The average degree of hysteresis of JY-5 m, JY-15 m, and JY-30 m samples were 0.12, 0.14, and 0.13 respectively. Regarding microstructure change, the void ratios (which were smaller than the actual void ratios of soil samples) measured by the mercury intrusion porosimetry (MIP) tests became larger after undergoing the drying-wetting cycle, and most of the increased pores were primarily attributed to the formation of small mesopores in the vicinity of the main capillary pores. The results of this study contribute valuable insights into the dynamics of soil-water retention hysteresis and the associated microstructure evolution of loess.

Waste-Wood-Isolated Cellulose-Based Activated Carbon Paper Electrodes with Graphene Nanoplatelets for Flexible Supercapacitors

Waste wood, which has a large amount of cellulose fibers, should be transformed into useful materials for addressing environmental and resource problems. Thus, this study analyzed the application of waste wood as supercapacitor electrode material. First, cellulose fibers were extracted from waste wood and mixed with different contents of graphene nanoplatelets (GnPs) in water. Using a facile filtration method, cellulose papers with GnPs were prepared and converted into carbon papers through carbonization and then to porous activated carbon papers containing GnPs (ACP−GnP) through chemical activation processes. For the morphology of ACP−GnP, activated carbon fibers with abundant pores were formed. The increase in the amount of GnPs attached to the fiber surfaces decreased the number of pores. The Brunauer–Emmett–Teller surface areas and specific capacitance of the ACP−GnP electrodes decreased with an increase in the GnP content. However, the galvanostatic charge–discharge curves of ACPs with higher GnP contents gradually changed into triangular and linear shapes, which are associated with the capacitive performance. For example, ACP with 15 wt% GnP had a low mass transfer resistance and high charge delivery of ions, resulting in the specific capacitance value of 267 Fg−1 owing to micropore and mesopore formation during the activation of carbon paper.

Regulation of collagen-derived carbon material structures through in-situ precipitation templating for fast sodium storage

Limited capacity with sluggish Na+ diffusion kinetics limits the application of carbon anodes in sodium ion batteries (SIB). Herein, we present a straightforward approach for fabricating porous carbons with delicate structural regulation using collagen fibers as precursor, in-situ generated Mg(OH)2 as template. The utilization of small-sized Mg(OH)2 facilitates the formation of mesopores further to enhance the diffusion kinetics of Na⁺. The collagen fiber precursors contain abundant N and S elements, resulting in N, S co-doping. Leveraging the absorption mechanism facilitated by rapid charge transfer, the synthesized porous carbon exhibits exceptional SIB performance in ether-based electrolytes: a capacity of 459 mAh g−1 at 0.05 A g−1 and 125 mAh g−1 at 50 A g−1; a capacity of 128 mAh g−1 with an average Coulombic efficiency of ≈99 % and a decay rate of 0.0072 % per cycle after 5000 cycles at 10 A g−1. Coupled with Na3V2(PO4)3 cathode, the fabricated full cell also demonstrates a high specific capacity of 290 mAh g−1 at 0.2 A g−1 with an initial Coulombic efficiency of 75.6 %. These findings offer an effective and practical strategy for the fabrication of porous carbon materials and the advancement of SIB through the development of advanced carbon anodes.

Catalytic reforming of cellulose pyrolysis volatiles over hierarchical HZSM-5: Mechanism of a protective effect of tetrapropylammonium (TPA+) during alkali treatment

A series of HZSM-5 with hierarchical pores was obtained by using a modified NaOH treatment method. This modification incorporated the use of tetrapropylammonium bromide. Furthermore, their catalytic performance for reforming of cellulose pyrolysis volatiles at 600 °C was investigated. TPAB-assisted alkali treatment increased the mesoporosity, relative crystallinity, and surface integrity of ZSM-5. Additionally, a significant portion of the acidic sites was preserved. The 0.1TPAB-0.2AT, treated with 0.1 M TPAB and 0.2 M NaOH, yielded the highest light aromatics at 156.9 mg/g. The coking resistance of the catalyst was also improved. Tetrapropylammonium (TPA+) achieves surface protective desilication by selectively adsorbing Si(0Al) on the zeolite. Subsequently, the continuous adsorption of TPA+ leads to mesopore formation within the zeolite. This continuous restriction on desilication limits the increase in mesopore volume, resulting in a relatively abundant and uniform distribution of smaller mesopores on ZSM-5. This mechanism holds promise for future synthesis of highly mesoporous ZSM-5.

Dissolution of alkali lignin in ionic liquid to fabricate nitrogen-doped carbon microspheres for electrochemical supercapacitors

Ionic liquids (ILs) have been extensively sought after for green solvents, catalysts, adsorbents, and carbon precursors. Herein, 1-ethyl-3-methylimidazolium acetate ([Emim][Ac])–lignin nitrogen-doped carbon microspheres (ECLMs) were easily synthesized through pre-oxidation and carbonization processes using a solution containing [Emim][Ac] and alkali lignin. The pre-oxidation process is analogous to the ionothermal carbonization method, wherein [Emim][Ac] serves as a reaction medium for preparing the ELCMs precursor. During the carbonization process, [Emim][Ac] served as a templating agent and heteroatom source to facilitate nitrogen doping and formation of micropores and mesopores. The as-synthesized ELCMs exhibits a considerably high specific surface area of 1267.2 m2/g and an optimal nitrogen-doping level of 2.21 %. This reveals its potential as a promising candidate for electrode materials in supercapacitor. The ELCMs demonstrate a remarkable specific capacitance of 262.5 F/g at 0.5 A/g and excellent rate capability in a three-electrode system. Additionally, the symmetric supercapacitor fabricated with electrode materials of ELCMs and a cellulose separator exhibits excellent cycling stability, with an impressive capacitance retention rate of 91.0 % after undergoing 5000 cycles at 5 A/g. Moreover, it achieves an ideal energy density of 4.17 Wh/kg at power density of 126 W/kg. This study investigates an effective strategy for designing and synthesizing different heteroatom-doped carbon materials from IL-biomass resources to enhance their applicability in energy storage devices.

Constructing Intrapenetrated Hierarchical Zeolites with Highly Complete Framework via Protozeolite Seeding.

Creation of intrapenetrated mesopores with open highway from external surface into the interior of zeolite crystals are highly desirable that can significantly improve the molecular transport and active sites accessibility of microporous zeolites to afford enhanced catalytic properties. Here, different from traditional zeolite-seeded methods that generally produced isolated mesopores in zeolites, nanosized amorphous protozeolites with embryo structure of zeolites were used as seeds for the construction of single-crystalline hierarchical ZSM-5 zeolites with intrapenetrated mesopores (mesopore volume of 0.51 cm3 g-1 ) and highly complete framework. In this strategy, in contrast to the conventional synthesis, only a small amount of organic structure directing agents and a low crystallization temperature were adopted to promise the protozeolites as the dominant growth directing sites to induce crystallization. The protozeolite nanoseeds provided abundant nucleation sites for surrounding precursors to be crystallized, followed by oriented coalescence of crystallites resulting in the formation of intrapenetrated mesopores. The as-prepared hierarchical ZSM-5 zeolites exhibited ultra-long lifetime of 443.9 hours and a high propylene selectivity of 47.92 % at a WHSV of 2 h-1 in the methanol-to-propylene reaction. This work provides a facile protozeolite-seeded strategy for the synthesis of intrapenetrated hierarchical zeolites that are highly effective for catalytic applications.

Constructing Intrapenetrated Hierarchical Zeolites with Highly Complete Framework via Protozeolite Seeding

AbstractCreation of intrapenetrated mesopores with open highway from external surface into the interior of zeolite crystals are highly desirable that can significantly improve the molecular transport and active sites accessibility of microporous zeolites to afford enhanced catalytic properties. Here, different from traditional zeolite‐seeded methods that generally produced isolated mesopores in zeolites, nanosized amorphous protozeolites with embryo structure of zeolites were used as seeds for the construction of single‐crystalline hierarchical ZSM‐5 zeolites with intrapenetrated mesopores (mesopore volume of 0.51 cm3 g−1) and highly complete framework. In this strategy, in contrast to the conventional synthesis, only a small amount of organic structure directing agents and a low crystallization temperature were adopted to promise the protozeolites as the dominant growth directing sites to induce crystallization. The protozeolite nanoseeds provided abundant nucleation sites for surrounding precursors to be crystallized, followed by oriented coalescence of crystallites resulting in the formation of intrapenetrated mesopores. The as‐prepared hierarchical ZSM‐5 zeolites exhibited ultra‐long lifetime of 443.9 hours and a high propylene selectivity of 47.92 % at a WHSV of 2 h−1 in the methanol‐to‐propylene reaction. This work provides a facile protozeolite‐seeded strategy for the synthesis of intrapenetrated hierarchical zeolites that are highly effective for catalytic applications.

Benign-by-design N-doped activated carbon from wasted aqueous assisted hydrochar of leftover rice for efficient H2S removal

The N-doped activated carbon is a potential material for H2S removal, reusing N-rich waste aqueous as a nitrogen source is promising to prepare in-expensive N-doped activated carbon. In this study, N-rich waste aqueous assisted hydrothermal carbonization and KOH activation were used to prepare activated carbon from starchy waste, concentrating on the effects of the nitrogen species (inorganic-N and organic-N) on the physicochemical characteristics and desulfurization performance of carbon material. Introducing inorganic-N (i.e., NH3·H2O) can increase the defect degree and enhance the formation of micropores and mesopores for N-doped activated carbon, leading to high storage ability for desulfurization products and well oxidation performance. The organic-N (i.e., alanine) was conducive to forming pyridinic-N and quinonyl for N-doped activated carbon, resulting in a strong ability of adsorption, dissolution, and oxidation for H2S. The organic-N determined the high breakthrough sulfur capacity for hydrothermal aqueous doping activated carbon (110.7 mg/g), which was ∼ 4.08 times than undoped activated carbon. The primary product of the desulfurization process was elemental sulfur (74.08%), with sulfuric acid and sulfonic acid as the subsequent by-products. After nitrogen doping, the contents of elemental sulfur and sulfuric acid increased by 5.65 and 1.73 times, respectively. The results revealed the correlations between nitrogen species in hydrothermal aqueous and the desulfurization performance of activated carbon, which could guide the selection of nitrogen-rich aqueous for synthesizing H2S removal N-doped activated carbon via the above novel method.

Conversion of Biomass-Derived Molecules into Alkyl Levulinates Using Heterogeneous Catalysts

Alkyl levulinates are promising and versatile biomass-derived chemicals, which are utilized as fuel additives, flavoring agents, fragrances, solvents, and precursors for synthesizing valuable γ-valerolactone. A method for synthesizing alkyl levulinates involves the esterification of levulinic acid with the corresponding alkyl alcohols in the presence of solid acid catalysts that have abundant Brønsted acid sites. Alkyl levulinates can also be synthesized from other biomass-derived molecules such as furfuryl alcohol and furfural via alcoholysis and one-pot conversion, respectively. Thus far, various heterogeneous catalysts have been developed for the conversion of the biomass-derived molecules (levulinic acid, furfuryl alcohol, and furfural) into alkyl levulinates. To obtain the target products in high yields, numerous strategies have been employed including increasing Brønsted acidity, dispersing and incorporating Brønsted acid sites, inducing the formation of mesopores, and inducing a synergistic effect of metal–Brønsted acid sites that are present on a catalyst surface. Here, we summarily reviewed the performances of the heterogeneous catalysts in the conversions, describing the design and development of the heterogeneous catalysts that ensured the excellent yield of alkyl levulinates.

Nanoarchitectonics of hierarchical porous carbon based on carbonization of heavy fraction of bio-oil and its supercapacitor performance

As a by-product of biomass pyrolysis process, the heavy fraction in bio-oil is characterized by high carbon content, easy polymerization and carbonization and abundant oxygen-containing functional groups, making it a suitable precursor for the synthesis of porous carbon. In this study, nanoarchitectonics of hierarchical porous carbon were prepared from the heavy fraction in bio-oil produced by pyrolysis of rice husk biomass with calcium citrate (C12H10Ca3O14) as a template agent and potassium oxalate (K2C2O4) as an activator. The roles of templating agents and activators in the carbonization polymerization of heavy oil were discussed by TG, BET, SEM, TEM, FTIR, XRD, Raman, XPS and other characterization analyses. C12H10Ca3O14 could promote the formation of mesopores, while the activation etching effect of K2C2O4 was the main source of micropores. The porous carbon effectively inherited the rich oxygen-containing functional groups in bio-oil and had a nanosheet structure with a specific surface area of 1905.3 m2/g. Supercapacitor performance of porous carbon was analyzed through electrochemical performance tests. The specific capacitance reached 233.4 F/g at 0.5 A/g and remained 205.0 F/g at 10 A/g. The attenuation rate was only 12.2 % when the current density increased by 50 times. After 10,000 cycles, the specific capacitance retention of the sample reached 92.3 %. The energy density reached 7.2 Wh/kg at a power density of 239.3 W/kg.

Characterization and optimization of pore structure and water adsorption capacity in pinecone-derived activated carbon by steam activation

Activated carbon, due to its notable porosity and cost-effectiveness, emerges as a promising desiccant material. This research delves into the utilization of pinecones as a precursor for the production of activated carbon through steam activation. The resultant activated carbon samples presented a porous structure and exhibited a high water adsorption capacity, with the highest adsorption capacity reaching 0.35 kg/kg, placing it in competition with commercial silica gel. Various experimental parameters were systematically manipulated during the production process to optimize both the pore structure and water adsorption capacity of the activated carbon samples. Elevating the carbonization temperature from 700 °C to 900 °C proved effective in enhancing pore distribution and elevating water adsorption capacity. Furthermore, higher activation temperatures contributed to the formation of additional mesopores and macropores, possibly attributable to micropore enlargement through steam activation. Nevertheless, these elevated activation temperatures resulted in an undesired increment in mesopores concerning water adsorption. The extension of activation time led to increased micropore formation, albeit with concurrent disruption, culminating in heightened total pore volume and surface area. This extension shifted the water adsorption-desorption isotherm to higher relative pressure ranges, accompanied by a larger hysteresis loop. Moreover, an increased steam mass flow rate was found to enhance the pore structure and water adsorption capacity of the activated carbon. The activated carbons exhibited sigmoid-shaped isotherms, signifying their suitability for both open-cycle and closed-cycle adsorption systems.

Rational Design and Development of a Soluble Mesoporous Carrier for the Solidification of a Preconcentrated Self-Nanoemulsion Formulation.

The solidification of self-preconcentrated nanoemulsion without changes in nanodroplet formation gains particular consideration due to the interaction between solidified carriers. This work aimed to develop mannitol mesoporous as a soluble carrier for supersaturated self-nanoemulsion (SSNE) using a design of experiment (DoE) approach. The mesoporous carrier was prepared by a spray-drying technique. The type of templating agent (TA) used to form a porous system, the amount of TA, and solid loading in the spray-drying process were studied. Several characterizations were performed for mannitol mesoporous formation, namely, powder X-ray diffraction, thermal analysis, scanning electron microscopy, and surface area analyzer. Solidification of SSNE incorporated into the mesoporous mannitol was carried out, followed by compaction behavior, flowability, and nanodroplet formation. The results revealed several process parameters for preparing the mesoporous mannitol, notably TA, which gained more significant consideration. Solid loading in the mesoporous preparation system reduced the surface area and pore size and did not affect solid SSNE flowability. The amount of TA increased the pore size and volume dramatically as well as the compactibility and flowability. Ammonium carbonate was the preferable TA for preparing the mesoporous carrier, particularly for the nanodroplet formulation process. In addition, synergistic and antagonistic interactions between factors were also observed. The optimized mesoporous carrier was applied for solidification, and there was no difference between SSNE and solid SSNE in the performance of nanodroplet formation.

Pyrolysis of sawdust impregnated with bio-oil of the same origin: Influence of organics in bio-oil on property of biochar

Reactive organics in bio-oil might further react with biochar of the same origin during pyrolysis. This was investigated herein via conducting the pyrolysis of poplar sawdust impregnated with a heavy fraction of the bio-oil from the same biomass at 400 or 600 °C. The results showed that the organics in the bio-oil for impregnation involved in the pyrolysis by enhancing biochar production via cross-polymerization with the organics on biochar and/or the reactive products like aldehydes/furans and some heavy organics. This led to the formation of additional carbonaceous deposit of aliphatic nature on the surface of biochar. This, however, did not enhance the thermal stability of the biochar but lowered activation energy and ignition temperatures for combustion. In addition, the organics in the bio-oil impregnated could also enhance deoxygenation, producing the biochar with the O mass fraction lower than counterpart by 24.1% at 400 °C. Moreover, impregnation of bio-oil also facilitated the formation of mesopores (S > 2nm: 178.6 m2 g−1 versus 117.6 m2 g−1 of counterpart) and created a carbonyls-deficient surface of the biochar.

Zeolitic Imidazolate Framework-8 and redox-additive electrolyte based asymmetric supercapacitor: A synergetic combination for ultrahigh energy and power density

In the present work, the electrochemical study of the synthesized electrode (ZIF-8 at 300 °C named as Z1) material was done in a three- and two-electrode (device) assembly using non redox-additive (6 M NaOH) and redox-additive (0.35 M K4(Fe(CN)6).3H2O in 6 M NaOH) electrolyte (RAE). X-ray diffraction (XRD) of Z1 sample confirmed the cubic phase with I -43 m space group. The hexagonal-type morphology was revealed by high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) analysis. The formation of narrow mesopores with average pore diameter of 1.53 nm and a large specific surface area of 1272 m2/g was confirmed by Brunauer-Emmett-Teller (BET) examination. The thermal stability of pristine ZIF-8 is investigated by Thermogravimetric analysis (TGA). In the three-electrode system, the Z1 sample as electrode reveals the pseudocapacitive (in NaOH) and battery-like redox behavior (in RAE). The fabricated electrode provides the specific capacitance of 30.6 F/g (1 A/g) and 33.1 F/g (10 mV/s) in NaOH. Moreover, the Z1 electrode exhibited an excellent specific capacity of 500.0C/g (at 10 A/g) and 532.5C/g (at 10 mV/s) in RAE. Additionally, an asymmetric supercapacitor (ASSC) device was assembled via RAE with activated carbon (AC) as an anode and Z1 as a cathode to investigate the practical feasibility. The constructed device in 0.0–2.0 V voltage window provides a significant power density of 20,000 W/Kg (for an energy density of 38.89 Wh/kg at 40 A/g) and an outstanding energy density of 75 Wh/kg (for a power density of 10,000 W/kg at 20 A/g). It exhibits good capacitance retention (80 % at 20 A/g) after 1500 cycles. Furthermore, three ASSC devices are connected in series to illuminate green, yellow, white, and red Light Emitting Diodes, thus demonstrating the potential realistic advantage of the current research work in supercapacitive energy storage devices.

Enhancement of visible light photocatalytic removal of residual tetracycline by Ni doped WO3 nano structures

In this study, Ni was used to dope into WO3 structure to improve its photocatalytic performance for tetracycline degradation. The obtained characterized results indicated that Ni dopants acted as nuclei during crystallization resulting in crystal size increase. However, Nickel dopants substituted several Tungsten elements in the WO3 leading to lattice distortion preventing agglomeration of these newly formed Ni-WO3 crystals resulting in particle size decrease. Thus, Ni-WO3 crystals were larger than WO3 crystals while Ni-WO3 particles were much smaller than WO3 particles. Ni dopants also induced formation of mesopore on WO3 surface resulting in surface areas increase of the Ni-WO3. On other hand, as compared to pristine WO3, the synthesized Ni-WO3 exhibited significant enhancement in visible light absorption as well as effectively prevented electron-hole recombination. Thus, the Ni-WO3 exhibited novel photocatalytic performance even under visible light. Among synthesized Ni-WO3, the 3Ni-WO3, which mole ratio of Ni/WO3 was 3 %, presented the highest photocatalytic performance for tetracycline degradation.

Adsorption of methylene blue from aqueous solution on biochar prepared from a K-rich biomass Alternanthera philoxeroides

ABSTRACT Alternanthera philoxeroides (AP) is a typical invasive plant. The quick spread of AP biomass may cause serious threat to ecological balance and biodiversity of the local area. However, AP has a high content of potassium, making it possible for preparing biochar through a self-activation process. In this study, AP biomass was employed to prepare porous carbon through a simple one-step pyrolysis. The effect of pyrolysis temperature (T) and carrier gas flow rate (v) onto the target carbon was intensively discussed. The obtained carbon were employed as adsorbents for methylene blue (MB) adsorption. Results showed that both of the T and v played great influence on the porous structure of the obtained biochar. Higher pyrolysis temperature and lower carrier gas flow rate were in favor of the formation of micropore and mesopore. The biochar obtained from 900°C pyrolysis temperature and 20 cm3 min−1 carrier gas flow rate (BC/900–20) possessed a satisfying specific surface area (825.6 m2 g−1) through the direct one-step pyrolysis, verifying the existence of pyrolysis gas self-activation and inorganic salt template self-activation effect. The maximum adsorption capacities calculated from Langmuir model were 424.9 mg g−1 for BC/900–20, which was comparable to that of the adsorbents reported recently.

Controllable structure of porous starch facilitates bioactive encapsulation by mild gelatinization

This research aims to explore encapsulation of probiotic Lactobacillus plantarum using porous starch (PS) by mild gelatinization (37 °C). The influence of amylose/amylopectin ratio on the maintenance of bioactivities of encapsulated probiotic was also investigated, and the pores size of PSs can be controlled by amylose/amylopectin ratio for the formation of macropores (1–10 μm), mesopores (10–100 nm), and/or micropores (1–10 nm). Scanning electron microscopy observed the morphology of multistage pores and based on this, the encapsulation of the microorganism (Lactobacillus plantarum, lpl) was successfully obtained by various existence forms. PS0:1-lpl demonstrated a higher encapsulation efficiency (9.5 × 1010 CFU/g) for L. plantarum than NS-lpl, PS1:4-lpl, PS1:1-lpl, and PS4:1-lpl. Encapsulation with PS1:1-lpl provides the best overall maintenance of bioactivities of L. plantarum in the presence of food processing stresses (retention rate up to 61.1%). Our study provides a new alternative strategy for bioencapsulation of probiotic by using porous starch, showing good potential for industrial application.