Biomimetic fabrication of mulberry-like nano-hydroxyapatite with high specific surface area templated by dual-hydrophilic block copolymer

Novel porous and mulberry-like hydroxyapatite (HAp) nanoparticles with three-dimensionally hierarchical microstructures were developed by using the dual-hydrophilic block copolymer poly(methacrylate acid)-b-poly[N-(2-methacryloylxyethyl) pyrrolidone] (PMAA-b-PNMP) as the template. It was found that the morphology and Ca/P ratio of synthesized HAp was highly related to the concentration of block copolymer and solution pH, respectively. The morphological evolution of HAp nanoparticles in different conditions was investigated systematically by scanning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The possible mechanism of PMAA-b-PNMP assisted mulberry-like HAp formation was also proposed based on the time-dependent TEM results. Attributing to the high specific surface area (SSA) of 119 m² g⁻¹, these mulberry-like HAp nanoparticles exhibited excellent adsorption ability for Congo Red (CR). The maximum adsorption capacity was 467 mg g⁻¹ according to the Langmuir monolayer adsorption model.     

Optimization of mesoporous alumina sol-gel synthesis by Taguchi and response surface methodology

Taguchi method (TM) and response surface methodology (RSM) have been employed to optimize three parameters, including the amounts of P123, the amounts of nitric acid and calcination temperature, in order to define an optimal setting for sol-gel synthesis of high surface area mesoporous alumina powder (MA). Herein, the comparison of the both statistical approaches has been examined and discussed considering the nitrogen adsorption as the response variable because this important character for mesoporous materials is exceedingly sensitive to the synthesis parameters. The BET surface area (S_BET) and pore volume of MA under Taguchi optimal condition were 323.5 m² g⁻¹ and 0.551 cm³ g⁻¹, respectively, by conducting confirmation test. Furthermore, the confirmation test showed high S_BET of MA (363.4 m² g⁻¹), which was in a good agreement with calculated S_BET result (431.25 m² g⁻¹) by a quadratic model under RSM optimal condition. Moreover, 3D response surface plots and 2D contour plots of desirability have been discussed to visualize the influence of input factors on response variable. It is also concluded that RSM shows more appropriate (12.33% higher S_BET than TM) and efficient optimal condition with determining a quadratic function as the relationship between S_BET and synthesis parameters.     

High-performance heterocyclic para-aramid aerogels for selective dye adsorption and thermal insulation applications

The high-performance polymer para-aramid (PPTA) is discovered to gel too soon during the polymerization process, resulting in poor processing performance. In this work, a homogeneous polymer solution containing heterocyclic para-aramid (HPPTA) was successfully synthesized by introducing 2,4-aminophenyl-5-aminobenzimidazole groups into the molecular chains of PPTA, and then HPPTA aerogel was prepared using a supercritical drying technique that took advantage of the HPPTA solution's excellent property of slow gelation. When the HPPTA polymer mass fraction was 1 wt%, the aerogel had the lowest density of 0.086 g cm⁻³ with a BET specific surface area of 376.59 m² g⁻¹. The HPPTA-2 aerogel had better adsorption performance for anionic dye methyl orange, with a maximum adsorption capacity of 319.47 mol g⁻¹; however, its adsorption capacity for cationic dye methylene blue and neutral dye dimethyl yellow was very low, at only 19.68 and 0 mol g⁻¹, respectively. The selective adsorption ability of HPPTA aerogel made it a simple and scalable platform for removing anionic dyes from water solutions. Furthermore, the HPPTA aerogel has outstanding thermal properties for thermal insulation applications in severe environments due to the synergistic effect of the 3D porous structure inside the aerogel and the exceptional thermal stability of the HPPTA.     

Adsorption of toluene on mesoporous materials from waste solar panel as silica source

The adsorption of toluene was tested with MCM-41 and mesoporous silica materials (S-MCM) synthesized from waste solar panel. X-ray powder diffraction (XRD), nitrogen adsorption–desorption analysis, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) were applied to characterize the prepared samples. In addition, the adsorption capacities of MCM-41 and S-MCM were almost the same which was observed according to the breakthrough experiments. The adsorption capacity of toluene in S-MCM was 57, 104, 200 and 277 mg g^− 1 for initial toluene concentrations of 250 to 1500 ppm respectively. The effects of the operation parameters, such as contact time and initial concentration on adsorption performance, were also tested in this study.     

Effect of core-shell reversal on the structural,magnetic and adsorptive properties of Fe2O3-GO nanocomposites

Effect of core-shell reversal on the nanocomposites of graphene oxide (GO) and ferric oxide (Fe₂O₃) was studied. Fe₂O₃@GO core-shell nanosheets were synthesized by sonication method, while the GO@Fe₂O₃ core-shell nanospheres by employing N,N′-dicyclohexylcarbodimide as the binding agent for the wrapping of GO sheets on pre-formed Fe₂O₃ nanoparticles (NPs). The phase composition, crystallinity and morphology of the nanocomposites were characterized by FT-IR, TEM, SEM-EDS, VSM, BET surface area study and XRD techniques. The saturation magnetization (M_s) was 1.25 and 0.51 emu g⁻¹ for GO@Fe₂O₃ and Fe₂O₃@GO respectively owing to the dependence of magnetic properties on the reversal of core-shell. BET analysis revealed the surface area of 100.32 m² g⁻¹ and 45.69 m² g⁻¹ for GO@Fe₂O₃ and Fe₂O₃@GO nanocomposites respectively. The fabricated nanocomposites were analyzed as adsorbents for the uptake of Pb (II) ions. The impact of various factors affecting adsorption process such as pH, adsorbent dose, contact time, temperature and metal ion concentration was also investigated. GO@Fe₂O₃ core-shell nanospheres showed a higher adsorption capacity for Pb (II) ions as compared to Fe₂O₃@GO core-shell nanosheet with the maximum adsorption capacities (q_m) of 303.0 and 125.0 mg g⁻¹ respectively. The equilibrium data was estimated by Freundlich, Langmuir, D-R and Temkin isotherm models. Thermodynamic analysis confirmed the spontaneous and exothermic nature of the adsorption process. The adsorption kinetics was significantly fitted to pseudo-second order model. The results confirmed that core-shell reversal can significantly alter the adsorptive properties of Fe₂O₃-GO nanocomposite     

In vitro evaluation of natural hydroxyapatite from Osteoglossum bicirrhosum fish scales for biomedical application

This study reports the obtainment of bioactive hydroxyapatite (HAp) extracted from scales of arowana fish (FSHA) (Osteoglossum bicirrhosum) by alkaline treatment followed by calcination at 600 and 800°C. The cell viability and bioactivity of hydroxyapatite particles (FSHA) were investigated and compared with those of HAp synthesized (s.HA) by the precipitation method. The HAp particles from fish scales showed non-toxic behavior to dental pulp stem cells similar to HAp synthesized. Additionally, bioactivity assays show that the Hap from natural source forms the bone-like apatite layer faster than s.HA sample, after being incubated in McCoy medium for 3 days. The results illustrate that HAp obtained from Osteoglossum bicirrhosum fish scale bio-waste showed excellent biocompatibility. Besides, this study provides an effective method for converting low-cost bio-waste into a value-added and it can be a potential alternative biomaterial for various biomedical applications.     

Magnetic porous carbons with high adsorption capacity synthesized by a microwave-enhanced high temperature ionothermal method from a Fe-based metal-organic framework

Magnetic porous carbons with high surface areas were easily synthesized from a Fe-based metal-organic framework (MOF) by a novel microwave-enhanced high temperature ionothermal method. By choosing a Fe-based MOF called MIL-100(Fe) as both a Fe and C precursor and a porous template, and furfuryl alcohol as a second precursor, a series of γ-Fe₂O₃/C composites with strong magnetism were prepared in 3 min by a microwave-enhanced high temperature ionothermal method. Structure, morphology and magnetic property, as well as porosity of the products, were carefully studied by powder X-ray diffraction, X-ray photoelectron spectroscopy, the BET surface area method, thermogravimetry, vibrating sample magnetometry, scanning electron microscopy, and high resolution transmission electron microscopy. The obtained γ-Fe₂O₃/C composites possess both high surface areas and magnetic characteristics. Their adsorption properties were preliminarily tested by the adsorptive removal of methylene blue from aqueous solution. The results suggest that such magnetic carbon composite exhibited high adsorption capacity (303.95 mg g⁻¹) and fast adsorption kinetics, as well as a perfect magnetic separation performance (M_s = 4.12–19.54 emu g⁻¹), for the MB removal from aqueous solution.     

Polymer-derived mesoporous Ni/SiOC(H) ceramic nanocomposites for efficient removal of acid fuchsin

In this paper, magnetic porous Ni-modified SiOC(H) ceramic nanocomposites (Ni/SiOC(H)) were successfully prepared via a template-free polymer-derived ceramic route, which involves pyrolysis at 600 °C of nickel-modified allylhydridopolycarbosilane (AHPCS-Ni) precursors synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with nickel(II)acetylacetonate (Ni(acac)₂). The resultant Ni/SiOC(H) nanocomposites are comprised of in-situ formed nanoscaled Ni socialized with small amounts of NiO and nickel silicides embedded in the amorphous SiOC(H) matrix. The materials show ferromagnetic behavior and excellent magnetic properties with the saturation magnetization in the range of 1.71–7.08 emu g⁻¹. Besides, the Ni/SiOC(H) nanocomposites are predominantly mesoporous with a high BET surface area and pore volume in the range of 253–344 and 0.134–0.185 cm³ g⁻¹, respectively. The measured porosity features cause an excellent adsorption capacity towards a template dye acid fuchsin with the adsorption capacity Q_t at 10 min of 80.7–85.8 mg g⁻¹ and the Q_e at equilibrium of 123.8–129.8 mg g⁻¹.     

A facile one-step synthesis and fabrication of hexagonal palladium-carbon nanocubes (H-Pd/C NCs) and their application as an efficient counter electrode for dye-sensitized solar cell (DSSC)

Hexagonal palladium-carbon nanocubes (H-Pd/C NCs) were prepared using a simple one-step chemical synthesis protocol and subsequently the prepared materials were used as the counter electrode (CE) in dye sensitized solar cell (DSSC) to replace the platinum (Pt) electrode. The H-Pd/C NCs were characterized by a variety of suitable analytical techniques including powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis to evaluate the crystalline, structural, morphological, compositional, chemical state and surface area. The BET nitrogen adsorption /desorption analysis shows that the as-prepared H-Pd/C NCs sample had a large surface area (568.8 m² g⁻¹) with average pore size of ∼3 nm. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses indicate that the H-Pd/C NCs have low charge-transfer resistance on the electrolyte/electrode interface and high electrocatalytic activity for the reduction of triiodide to iodide redox electrolyte and hence it is used as a CE in DSSC. The H-Pd/C NCs showed an overall power conversion efficiency (PCE) of 4.1% which performance is comparable with the conventional Pt CE (4.0%) under the identical condition.     

Evaluation of the Mn(II) adsorption potential of SiO2 obtained by different wet chemical methods

This paper describes the development of SiO₂ by 2 different wet chemical methods: polymeric precursor (PP) and sol-gel (SG). These samples were used as adsorbents of Mn(II) metal ions. Physicochemical characteristics of the 2 adsorbents were established, while zeta potential, Scanning Electron Microscopy, and Brunauer-Emmett-Teller (BET) surface area methods were further employed for characterization. Efficiencies of the prepared adsorbents in the adsorption of Mn(II) from aqueous solutions were investigated. The BET surface areas of the prepared adsorbent were 171 and 7 m² g⁻¹ for SiO₂ PP and SiO₂ SG, respectively. Optimal adsorption occurred at pH 8.5, 5g L⁻¹ of adsorbent concentration, and 90 minutes of contact time for both adsorbents. The Langmuir and Freundlich isotherms models fitted the experimental data of SiO₂ PP and SiO₂ SG, respectively, and SiO₂ PP showed the highest adsorption capacity due, probably, to its greater specific area.     

Highly selective CO2 capture by S-doped microporous carbon materials

S-doped microporous carbon materials were synthesized by the chemical activation of a reduced-graphene-oxide/poly-thiophene material. The material displayed a large CO₂ adsorption capacity of 4.5 mmol g⁻¹ at 298 K and 1 atm, as well as an impressive CO₂ adsorption selectivity over N₂, CH₄ and H₂. The material was shown to exhibit a stable recycling adsorption capacity of 4.0 mmol g⁻¹. The synthesized material showed a maximum specific surface area of 1567 m² g⁻¹ and an optimal CO₂ adsorption pore size of 0.6 nm. The microporosity, surface area and oxidized S content of the material were found to be the determining factors for CO₂ adsorption. These properties show that the as synthesized S-doped microporous carbon material can be more effective than similarly prepared N-doped microporous carbons in CO₂ capture.     

Adsorption characteristics of carbonized bark for phenol and pentachlorophenol

The potential of using carbonized slash pine bark as a substitute for activated carbon was examined in this study. The bark was carbonized by slow heating in nitrogen for 6·5 h to 672°C. The BET-N₂ surface area, average micropore and mesopore diameter, and micropore volume were 332 m² g⁻¹ 21·7 Å, and 0·125 cm³ g⁻¹, respectively. The adsorption capacities for phenol and pentachlorophenol (PCP) at pH 2 and pH 8 were evaluated. The Langmuir equation provided a slightly better fit than the Freundlich equation to two sets of phenol data. The calculated Freundlich constants, K = 0·41–0·58 mmol/g/(mmol dm⁻³)^1/n and 1/n = 0·30–0·41, were lower and higher, respectively, than literature values for activated carbons. The adsorption capacity of the carbonized bark was much lower for PCP than for phenol. The protonated and anionic PCP isotherms were Type II or III, respectively, in the Brunauer classification. The BET equation provided the best fit to protonated PCP isotherm data. The anionic PCP data were fitted to both the BET model and an equation used in the literature to represent phosphate adsorption on activated carbons. Non-linear regression of the data for both phenol and PCP adsorption with the Freundlich, Langmuir and BET equations generally gave more accurate param-eters, compared with the use of linearized equations to obtain the parameters. © 1998 SCI.     

Single-step process without organic template for the formation of zeolite A from RHA

Dice-shaped zeolite A (NaA) was prepared via direct dissolution of rice husk ash (96.5% SiO₂) in the presence of NaOH and sodium aluminate solution by autoclave process at 90°C/6 h without using any templating agent. The prepared particles were characterized by DTA/TG, XRD, FTIR, N₂ adsorption-desorption physisorption analysis, FESEM, and TEM. XRD results confirmed crystallization of pure NaA zeolite phase. FTIR study shows the characteristic bands at 554 cm⁻¹ for double 4 membered ring (D4R) of NaA zeolite. The total BET surface area of the product was found to be 31.6 m² g⁻¹. FESEM and TEM images show dice shaped NaA particles of size around 1 μm which is formed via oriented crystalline aggregation of primary particles (30-40 nm). A tentative mechanism was proposed for the formation of NaA crystals through direct dissolution of rice husk ash. The synthesized NaA zeolite could be used for purification of alcohol and separation of toxic and radioactive ions from waste water via a cost-effective process.     

Hydroxyethyl cellulose hydrogel modified with tannic acid as methylene blue adsorbent

This work developed an effective way to improve the methylene blue (MB) adsorption performance of cellulose-based hydrogel by modified with tannic acid (TA). HEC-co-p(AA-AM)/TA hydrogel was synthesized by grafting of acrylic acid (AA) and acrylamide (AM) onto hydroxyethyl cellulose (HEC), followed by modified with TA. Fourier transform infrared spectroscopy manifested that AA and AM were successfully grafted onto the hydrogel, and TA was immobilized in the hydrogel. Field emission scanning electron microscope demonstrated that the hydrogel after TA modification had a homogeneous pore structure. Brunauer-Emmett-Teller (BET) surface areas, total pore volume, and average pore diameters of the hydrogel are 11.821 m² g⁻¹, 0.0641 cm³ g⁻¹, and 2.538 nm, respectively. The high swelling ratio (1179.2 g g⁻¹ in deionized water) was in favor of the MB adsorption. The results of the adsorption experiments illustrated that HEC-co-p(AA/AM) hydrogel had excellent MB adsorption performance. As the pH increases, the electrostatic attraction is enhanced, and the adsorption capacity is improved. The adsorption process was more fit with pseudo-second-order kinetics, and the maximum adsorption capacity (3438.27 mg g⁻¹) was determined by Langmuir model. Thermodynamic studies suggested that the adsorption process is spontaneous, exothermic, and entropy reduction. X-ray photoelectron spectroscopy analysis confirmed that MB molecules were reacted with the oxygen atoms in hydroxyl and carboxyl groups by ion-exchange. High reusability demonstrated that the hydrogel could be a potential candidate for removal cationic dye from industrial effluents.     

Magnetic molecularly imprinted polymers obtained by photopolymerization for selective recognition of penicillin G

Some of the most important life-saving medications are β-lactam antibiotics (such as Penicillin G). However, these medicines have not adequately been discharged into the environment; penicillin residues offer health risks and enhance the development of resistances. Thus, its selective separation from complex matrices is a challenge worth tackling. A novel strategy of synthesis, by photopolymerization, was applied to develop magnetic molecular imprinted polymers (mag-MIPs) aiming the recognition of penicillin G (also known as benzylpenicillin). Photopolymerization, when compared with the more common thermopolymerization, has the advantage of occurring at lower temperatures, which prevents analyte degradation. The Mag-MIP presented higher surface area than the conventional MIP and good adsorption capacity of the analyte while maintaining its selectivity. The synthesized material was characterized by X-ray diffraction, showing that the magnetite nanoparticles were formed and the MIP polymerization on their surface was performed, once the material was amorphous. Furthermore, the pore formation was evaluated by BET, indicating a high surface area (832 m² g⁻¹) and large pore volume (0.80 cm³ g⁻¹) in the mag-MIP compared to the magnetic non-imprinted polymer (mag-NIP: 147 m² g⁻¹ and 0.33 cm³ g⁻¹). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48496.     

Solution combustion synthesis of CeO2 powders and its application in water treatment

CeO₂ powders were synthesized via a solution combustion method. The product was characterized by X-ray diffraction scanning electron microscope, and BET surface area analysis. The results indicated that the CeO₂ powders present a foaming state with a surface area of 28.17 m² g^–1. The adsorption performance of the CeO₂ powders was tested toward the removal of typical pollutants of Cr(VI) and Congo red (CR). The results showed that the adsorption of Cr(VI) and CR onto CeO₂ powders followed the Langmuir isotherm model and pseudo-second-order kinetics, with an adsorption capacity of 5.69 mg g^–1 and 35.51 mg g^–1, respectively.     

Novel synthesis of mesoporous hydroxyapatite using carbon nanorods as a hard-template

A novel hard-template synthesis approach for the fabrication of mesoporous hydroxyapatite (HAP) is described herein. Carbon nanorods, synthesised using mesoporous silica (SBA-15) and an acidified sucrose solution, are used as a hard template, after which, they are utilised to synthesise mesoporous HAP. Transmission electron microscopy (TEM), X-ray diffraction (XRD) energy-dispersive X-ray spectroscopy (EDX) and nitrogen adsorption/Brunauer–Emmett–Teller (BET), are all employed to characterise the synthesised materials. We demonstrate that this approach allows for the successful fabrication of single phase HAP with surface area 242.20±2.27 m² g⁻¹ and average pore diameter 3.5 nm and 18.9 nm. This work proposes for the first time a bespoke innovative procedure that employs carbon nanorods as a template for the synthesis of mesoporous HAP via a hard templating protocol.     

Functionalized N-doped interconnected carbon nanofibers as an anode material for sodium-ion storage with excellent performance

The electrochemical performance of sodium-ion battery was improved by using functionalized interconnected N-doped carbon nanofibers (FN-CNFs) as the anode. The material was synthesized with polypyrrole as precursor by a simple method. The FN-CNF electrode exhibits excellent rate capability and cycling stability, delivering a capacity of 134.2 mAh g⁻¹ at a high current density of 200 mA g⁻¹ after 200 cycles and retains a capacity of 73 mAh g⁻¹ even at an extremely high current density of 20 A g⁻¹. The superior performance can be attributed to N-doped sites and functionalized groups, which are capable of capturing sodium ions rapidly and reversibly through surface adsorption and surface redox reactions.     

Lanthanum-doped spinel cobalt ferrite (CoFe2O4) nanoparticles for environmental applications

Magnetic nanomaterials have been widely studied as adsorbents in the removal of contaminants from effluents. In this context, lanthanum-doped cobalt ferrites (CoLa_xFe_2-xO₄) were successfully synthesized via sol-gel method at 300 °C. XRD, TEM and BET analyses showed that minute particle size was achieved, with decreases along increasing La³⁺ content. XRD patterns confirm single cubic spinel CoFe₂O₄ nanoparticles. The average crystallite size confirmed via TEM images ranges between 5 nm and 12 nm. Surface area increased from 74.3 to 109.3 m² g⁻¹ with the addition of La³⁺. Raman spectra indicate a tendency towards inversion of the spinel induced by the addition of the lanthanide. The optical band gap of the samples doped with La showed a progressive decrease from 1.35 to 1.1 eV, which was not expected. Hysteresis loops indicate a transition from hard to soft magnetism. A significant decrease in coercivity from 740 to 158 Oe was observed with increase in La³⁺ (CoFe₂O₄ to CoLa_0.025Fe_1.975O₄). Total magnetization (M* defined for maximum available field H = 20 kOe) decayed from 44.6 to 29.0 emu.g⁻¹. These results show that the produced nanoparticles are ideally suited as magnetic adsorbents in separation of pollutants from wastewater.     

Synthesis of citric acid modified β-cyclodextrin/activated carbon hybrid composite and their adsorption properties toward methylene blue

In this article, citric acid modified β-cyclodextrin/activated carbon hybrid (CA-β-CD/AC) composites were synthesized by crosslinking reaction, and their adsorption properties for methylene blue were studied. The scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) method were used to characterize the structure and the morphology of composite materials. It was investigated that the effect of experiment parameters on the adsorption performance including weight fraction of AC in the composite, the adsorbent dose, the initial concentration of MB, the solution pH value, contact time, and temperature. The maximum adsorption capacity calculated by the Langmuir isotherm is 862.07 mg g⁻¹. Kinetic studies show that the adsorption process follows the pseudo-first-order and pseud-second-order reaction models. Thermodynamic analysis indicated that the adsorption behavior was an exothermic reaction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48315.