Carbon Silica Composites Research Articles

CARBON-SILICA COMPOSITE AS ADSORBENT FOR REMOVAL OF CATIONIC DYE (METHYLENE BLUE)

The aim of this research was to synthesize carbon-silica composite (CSC) as an adsorbent for cationic dye removal from wastewater. Molasses, a by-product of the sugar industry, was successfully utilized to prepare CSC by sol-gel method with tetraethoxylsilane (TEOS) as silica source. The physicochemical properties of the composites were studied by N2 adsorption, FTIR and TGA. The highest specific surface areas of CSC was 144 m2/g at a molasses/TEOS ratio of 0.8, with a mesopore volume of 83% and average pore width of 9.71 nm. This optimal CSC was evaluated for methylene blue (MB) adsorption using batch experiments under varying adsorption times and initial MB concentrations. Adsorption equilibrium was reached within 14 h and the pseudo-second order equation provided the adequate fit for the kinetic studies, suggesting that dye adsorption was limited by chemisorption. The equilibrium data were best described by the Sips model with a maximum adsorption capacity of 180.22 mg/g. The CSC derived from molasses is considered a potentially promising adsorbent for cationic dye removal in wastewater.

Determination of adsorption capacity, regeneration ability, and aggregation tendency toward inorganic and organic pollutants of metal-doped carbon–silica composites in multicomponent systems

Abstract The main aim of the study was to develop a method for determining the adsorption capacity, regeneration ability, and aggregation tendency of metal-doped carbon–silica composites (iron-doped, C/Fe/SiO2, and manganese-doped, C/Mn/SiO2) against heavy metals and selected organic substances. The properties of these composites were compared with those of metal-free silica–carbon composite (C/SiO2). Inductively coupled plasma–optical emission spectrometry (ICP–OES) and high-pressure liquid chromatography were used to determine the adsorbed amounts and the desorption degree of organic/inorganic pollutants. Potentiometric titrations and electrophoretic mobility measurements were conducted to understand the mechanisms that were driving adsorption and particle aggregation. The size of the aggregates formed in the systems as well as the stability of the examined suspension were estimated by using ultraviolet-visible spectrophotometry. The performed experiments showed that the selected combination of methods is appropriate to determine the potential of metal-doped carbon–silica composites as adsorbents as well as the ease of their removal with adsorbed contaminants from aqueous solutions by sedimentation.

Enhancing lithium-storage properties through amino functionalization in two-dimensional lamellar carbon-supported mesoporous SiO2 nanospheres

Currently, common two-dimensional (2D) carbon materials composited with Si-based materials as anode for lithium-ion batteries exhibit excellent electrochemical properties. In this study, we describe the one-step synthesis of amino-functionalized mesoporous silica (SiO2) nanospheres through self-assembly. Morphology modulation and amino group grafting were performed simultaneously without secondary modification. Using tartaric acid and melamine as dual carbon sources, the 2D lamellar structure was constructed using the dehydration condensation reaction, with the mesoporous SiO2 nanospheres uniformly intercalated within the carbon sheets. The composites were securely bonded by chemical bonding, effectively addressing the issue of structural collapse often encountered in silica–carbon composites. Ultimately, the lamellar SiO2@NC composite exhibited stable capacity of 539.5 mAh g−1 after 500 cycles at 1 A g−1. This strategy is simple and effective, compared to the complex processes typically associated with 2D carbon materials synthesis, and can be potentially extended to applications in catalysis, adsorption, and separation within diverse fields.

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.

Ultra-stable and long-lived multi-color room temperature phosphorescent carbon dot and silica composites for data encryption and anti-counterfeiting

Carbon dot (CD)-based room temperature phosphorescence (RTP) materials have garnered fundamental attention due to their unique and irreplaceable advantages. However, developing CD-based materials with stable multi-color RTP emission is also desired. Herein, we present a rational design of carbon dots and SiO2 composite (CD@ Silica) fabrication, which demonstrates excellent stability in its RTP, showcases multi-color emission, and experiences thermal enhancement. Multi-color afterglow emission is achieved in CD/fluorescence dyes@ Silica composite systems due to the high efficiency of the Förster resonant energy transfer (FRET) processes between CDs and fluorescence dyes. The covalent interactions between CDs and silica shells protect the triplet state, and the structure significantly promotes the multi-color RTP emission realized in some challenging environments (such as in acid or alkaline aqueous solution). Utilizing the stable phosphorescence emission, we successfully implement the concepts of multi-level information encryption and fingerprint anti-counterfeiting through CD@ Silica composites.

Bio-based nitrogen doped carbon-silica composites from low value sugarcane by-products for the selective adsorption of Au(III) from aqueous systems

This study investigates the development of carbon-silica composite (CSC) adsorbents with tuneable surface properties for gold adsorption from silica and molasses. Nitrogen modification of the CSC adsorbents was achieved through a facile urea impregnation onto the CSC, followed by pyrolysis at 400 °C (400C-5A). Exceptional Au(III) adsorption was demonstrated from acidic solutions, with a maximum adsorption capacity of 416.9 mg g−1. While CSC with no nitrogen modification (400C) only exhibits an adsorption capacity of 337.9 mg g−1. Langmuir isotherm model and pseudo-second order kinetic model were found to best describe the adsorption behaviour for Au(III) sorption on both nitrogen-modified and non-modified CSC. Urea modification led to nitrogen containing graphitic, pyridinic and pyrrolic functionalities, of which pyridinic groups were active sites for metal coordination, leading to enhanced adsorption and high selectivity towards Au and Pd. Au adsorptions of greater than 99.8% were revealed using both modified and unmodified CSC, even at low concentrations of gold (5 or 10 ppm). X-ray Photoelectron spectroscopy (XPS) analysis of 400C-5A following adsorption indicated the presence of both Au(0) and Au(III), demonstrating that adsorption took place through both chelation and an adsorption-reduction mechanism. These effective adsorbents derived from abundantly available, low cost, bio-based chemicals or low value by-products could create new opportunities for Au and/or Pd adsorption from acidic solutions.

Enhanced synthesis of C2+ alcohols from syngas over a Co-Co2C catalyst supported on mesoporous carbon–silica composites

Higher alcohol synthesis (HAS) from syngas is a promising route for converting non-petroleum fossil energy resources into useful fuels or chemicals, while the design and preparation of highly efficient catalysts remain challenging. Herein, a series of Co0-Co2C catalysts supported on mesoporous carbon–silica composites were prepared for HAS. The composites were derived from carbon-silica nanocages, consisting of uniformly distributed carbon and silica species, which significantly affected the particle dispersion, phase evolution and catalytic performance. With increasing the carbon content, the initial carburization of cobalt was promoted, and some obtained Co2C tended to convert to hexagonal closest packed cobalt (hcp-Co, a highly active site for Fischer-Tropsch), boosting the CO dissociation and catalyst activity. While as the silica content increased, more Co2C phases can be stabilized, leading to enhanced Co2C/Co0 ratio and ROH selectivity. As a result, the optimal 15Co/22Si@C catalyst achieved a ROH selectivity of 40.1% where 96.0 wt% was higher alcohols (HA), and a space time yield (STY) towards HA of 26.5 mmol·gcat−1·h−1, which remarkably outperformed most of the reported Co-based catalysts in HAS. Moreover, the superior stability of over 250 h reaction was obtained, owing to the confinement effect and strong metal-support interaction provided by the mesoporous carbon–silica composites. This work may provide guidance for designing high-performance monometallic cobalt catalyst in HAS.

Adsorption and Release of Ibuprofen from Silica-Carbon Composites Based on Rice Husks (Oryza Sativa) and Banana Peels (Musa Acuminata)

Adsorption and Release of Ibuprofen from Silica-Carbon Composites Based on Rice Husks (Oryza Sativa) and Banana Peels (Musa Acuminata)

Application of N-Doped Carbon–Silicon Oxycarbide Based on POSS Synthesis in Lithium-Ion Batteries

Si/C materials have attracted much attention as anode materials for lithium-ion batteries. Here, nitrogen-doped silica carbon composites with a carbon-coated structure were synthesized using poly(1-vinylimidazole) in the presence of octavinyl-silsesquioxane followed by annealing and magnesium thermal reduction processes of the polymer precursor (PPVIm). Benefiting from the moderate Si–O–C bonds, the prepared NSiOC possesses a high first discharge capacity of 1862.3 mAh·g–1 at 0.2 A·g–1 and an initial Coulombic efficiency of 70.0% at 30 °C. When the temperature rises to 60 °C, the first discharge and charge specific capacities of the synthesized anode material at 0.2 A·g–1 increase to 2103.0 and 1528.7 mAh·g–1 with an ultralong lifespan of more than 1000 cycles. Moreover, the results show that the degradation of performance during the initial phase of cycles can be ascribed to the formation of an SEI layer and insufficient electrolyte penetration. The battery maintains a steady state (nearly 600 consecutive cycles) for a long time afterward as the activation of the anode material increases, attributed to the low expansion coefficient originating from the porous structure of the carbon capping layer and silicon oxide. In addition, the electrochemical attenuation process of the electrode material with a unique inorganic silica skeleton and exceptional electrochemical performance was also investigated for the assistance of future design in high-performance electrode materials.

A Simple Method to Synthesize Novel Mesoporous Carbon–silica Composites from the By-product of Ethanol Production

A Simple Method to Synthesize Novel Mesoporous Carbon–silica Composites from the By-product of Ethanol Production

Metallothermic Reduction of Silica–Carbon Composites: Revealing the Relationship Between Silicon-Based Products and the Reactivity of Reductants

Suppressing the formation of SiC during the magnesiothermic reduction of SiO2–C composite is still challenging. In this paper, the formation of SiC can be tentatively controlled by tuning the reactivity of reductants that can be modulated by alloying with Si at different atomic ratios. The reduction product is SiC when using Mg as the reductant, while the C–Si composites are formed when using the reductants with relatively low reactivity (e.g., Mg–Si alloy, Ca–Si alloy). The obtained C–Si composites reduced from C–SiO2 show excellent electrochemical performance, delivering a specific discharge capacity of 925 mAh g−1 at 1 A g−1 after 200 cycles and 825 mAh g−1 at 2 A g−1 after 300 cycles. In addition, when bio-silica is used as Si resource, the C–Si composites prepared from the rice husks also exhibit excellent electrochemical performance, delivering a specific discharge capacity of 687 mAh g−1 at 2 A g−1 after 300 cycles. Overall, the revealed reactivity–composition relationship can be extended to selectively prepare carbon- or carbide-based target materials as well as to harvest both C and Si from Si-containing waste biomasses.

Recent Advances in Carbon-Silica Composites: Preparation, Properties, and Applications

The thermal catalytic conversion of biomass is currently a prevalent method for producing activated carbon with superb textural properties and excellent adsorption performance. However, activated carbon suffers severely from its poor thermal stability, which can easily result in spontaneous burning. In contrast, silica material is famed for its easy accessibility, high specific surface area, and remarkable thermal stability; however, its broader applications are restricted by its strong hydrophilicity. Based on this, the present review summarizes the recent progress made in carbon-silica composite materials, including the various preparation methods using diverse carbon (including biomass resources) and silica precursors, their corresponding structure–function relationship, and their applications in adsorption, insulation, batteries, and sensors. Through their combination, the drawbacks of the individual materials are circumvented while their original advantages are maintained. Finally, several bottlenecks existing in the field of carbon-silica composites, from synthesis to applications, are discussed in this paper, and possible solutions are given accordingly.

Exploring the Iron Oxide Functionalized Biobased Carbon-silica-polyethyleneimine Composites for Hexavalent Chromium Removal from Dilute Aqueous Solutions

The contamination of water resources by toxic hexavalent chromium remains a challenge. In this study, amino-functionalized iron oxide biobased carbon-silica composites were prepared through co-precipitation of Fe(II) and Fe(III) over Macadamia activated carbon and explored as feasible adsorbents for the removal of Cr(VI) from dilute aqueous solutions. The energy dispersive spectroscopy (EDS) elemental analysis confirmed the existence of Fe, Si, O, and C atoms, which form the backbone of the composite. The FTIR also showed the presence of Fe-O and Si-O-Si and Si-OH spectral bands, affirming the backbone of the adsorbents. Cr(VI) adsorption efficiency (5.76 mg/g) was achieved at pH 1 when an initial concentration of 2.5 mg/L, contact time of 90 min, and dosage concentration of 1.7 g/L were used. The data were best described by the Langmuir adsorption model and pseudo-second-order rate model. ΔG° (−3 to −12 kJ/mol) and ΔH° (46, 12 and 5 kJ/mol) values affirmed that the adsorption of Cr(VI) was spontaneous and endothermic and dominated by chemical interactions.

Carbon–Silica Composites from Sago Waste for the Removal of Chromium, Lead, and Copper from Aqueous Solution: Kinetic and Equilibrium Isotherm Studies

Utilizing agricultural wastes into value-added products of a low-cost adsorbent has become of interest in recent years. In this study, sago-silica composite with a ratio of 80:20 (w/w%) was prepared via chemical grafting of abundantly available sago waste and rice husk. The physicochemical properties of the composites were characterized, and their efficiencies as adsorbents on the removal of chromium (Cr), lead (Pb), and copper (Cu) in aqueous media were studied as a function of pH, adsorbent dosage, initial concentration, and contact time. Results showed that the sago-silica composite has a more extensive surface area of 227.7 m2/g compared to SAC (167.3 m2/g). The adsorption of Cr and Cu gave excellent monolayer and heterolayer adsorption on sago-silica composite represented by Langmuir and Freundlich’s isotherm based on coefficient regression, R2 > 0.9. Pseudo-second-order kinetics model showed best fitted with excellent adsorption capacity qe of Cr, Pb, and Cu adsorption on sago-silica composites, which demonstrated the occurrence of chemisorption process between the composite and metal ions. The composite from carbon–silica is one of the cost-effective natural sorbents which demonstrate excellent removal of heavy metal from the aqueous environment.

Synthesis of bifunctional tin-based silica–carbon catalysts, Sn/KIT-1/C, with tunable acid sites for the catalytic transformation of glucose into 5-hydroxymethylfurfural

Catalytic transformation of carbohydrates to bio-chemicals such as 5-Hydroxymethylfurfural (HMF) has become a hot research topic, but development of cost-effective/efficient catalysts and processes remains a challenge for industrial application. In this study, efficient bifunctional Sn/KIT-1/C catalysts with controllable acid sites were synthesized and applied for glucose-to-HMF conversion. Strong Lewis acid sites were introduced into the framework of disordered mesoporous silica by liquid-phase grafting of tin chloride, and Bronsted acid sites were generated by inserting carbon into the mesopores, followed by controlled oxidation of the carbon. Characterizations revealed that optimizing the amount of carbon source, and carbonization and oxidation temperature provided a proper amount and strength of acidity that could significantly catalyze glucose dehydration reaction to HMF with suppressed byproducts formation. The best catalyst Sn/KIT-1/C(75–400-300) demonstrated superior catalytic performance at 175 °C for 2 h under THF/H2O biphasic system, obtaining 78.4 ± 2.1% and 82.9 ± 2.4% HMF yield and selectivity, respectively. The high activity may be attributed to catalyst high surface area/porosity, and the presence of well-balanced amounts and strength of Lewis/Bronsted acid sites. The catalyst could maintain its excellent catalytic activity for five consecutive runs, suggesting the high physical–chemical stability of the catalyst. The results obtained in this work demonstrated that bifunctional metal-supported silica–carbon composites can be a promising catalyst for simple/complex carbohydrates conversion to HMF/bio-based chemicals.

The effect of polyethylene glycol addition on the synthesis of solid acid catalyst and its applications in esterification reaction

Synthesis of a catalyst by a sol-gel method is commonly conducted using a template to form pores to increase the number of active sites. In this work, mesoporous silica-carbon composites were prepared by sol-gel method using polyethylene glycol (PEG) 6000 as the template. Sodium silicate, commercially known as water glass, a cheap material, was used as the silica source. Here, PEG 6000 served as both the carbon source and the template. The silica-PEG composite was then carbonized at 550°C for 1 h to obtain silica-carbon composite. The sulfonate group was grafted into the composite by sulfonation with sulfuric acid at 100°C for 5 h. The sulfonated silica-carbon catalyst had a surface area of approximately 1490.8 m2/g. The very high surface area was able to hold a large amount of sulfonate group resulting an ion capacity of approximately 2.09. The composite was successfully be used as heterogeneous catalyst for esterification of acetic acid with ethanol with a conversion of 90.27%, higher than that of commercially Flotrol F-007.

Preparation of core-shell silica-carbon composite microspheres stationary phase and application in saccharide separation

In this study, core-shell mesoporous silica-carbon composite microspheres (Sil@MC) were prepared by one-step coating of the phenol formaldehyde polymer (PF) on SiO2 surface and by carbonizing the PF polymer under nitrogen atmosphere. The morphology observation of the Sil@MC stationary phase showed that it had good monodispersity. Surface area (302 m2/g), mean pore diameter (9.5 nm), and pore volume (0.63 cm3/g) of Sil@MC materials were also measured by pore structure analysis. The results showed that the Sil@MC was successfully immobilized on the silica particles via copolymerization and carbonization. As a stationary phase of HPLC, the Sil@MC column was filled by a slurry method. The Sil@MC materials formed after calcination of SiO2 coated with phenolic resin could be used for the separation of four polar sugar compounds (D-(+)-glucosamine hydrochloride, glucose, D-(+)-trehalose dihydrat and raffinose) with the mobile phase of acetonitrile-water (containing 0.1% (v/v) formic acid). However, the material formed by calcinating SiO2 without coating phenolic resin could not separate these polar sugar compounds by HPLC-MS. Finally, the representative oligosaccharide isomers of raffinose, melezitose and stachyose, nystose, and human milk oligosaccharide isomers, such as 3'-sialyllactose, 6'-sialyllactose and lacto-N-newtetraose, lacto-N-tetraose, were successfully separated by the Sil@MC column with good peak shapes. The results demonstrates that silica-carbon composites derived from phenolic resin have potential application in polar compounds chromatographic separation.

Graphitic mesoporous carbon-silica composites from low-value sugarcane by-products for the removal of toxic dyes from wastewaters.

Highly porous carbon-silica composites (CSC) were prepared for the first time through a simple wet impregnation process and subsequent pyrolysis of low-value sugarcane by-products, namely molasses. These CSC materials demonstrate a distinct range of functionalities, which significantly differ from similar materials published in the literature. Importantly, the carbon-silica composites prepared at 800°C exhibited exceptional adsorption capacities for the azo-dye congo red (445 mg g−1), due to the graphitic carbon coating and unique functionality including C-O-C within the porous structure. Congo red adsorption capacity of the highly mesoporous graphitic carbon-silica composites significantly exceeds that of commercial activated carbon and silica, these carbon-silica composites therefore represent an effective step towards the development of porous bio-derived adsorbent for remediation of dye wastewaters. Both the porous properties (surface area and pore size distribution) and the functionality of the carbon coating were dependent on the temperature of preparation. The sustainable synthetic methods employed led to a versatile material that inherited the mesoporosity characteristics from the parent silica, demonstrating mesoporous volumes greater than 90% (as calculated from the total pore volume). Adsorption on the 800°C prepared carbon-silica composites demonstrated an excellent fit with the Langmuir isotherm and the pseudo-first-order kinetic model.

Study on Adsorption and Aggregation in the Mixed System of Polyacrylamide, Cu(II) Ions and Innovative Carbon-Silica Composite.

The paper presents an original study on adsorption and aggregation phenomena in a mixed system consisting of a macromolecular compound, heavy metal ions and an innovative adsorbent. The authors used ionic polyacrylamides (PAM), Cu(II) ions and carbon–silica composite (C-SiO2) in the experiments. Such a system has not yet been described in the literature and therefore, the article is of significant novelty and great importance. The composite was prepared by mixing phenol–formaldehyde resin with silica and pyrolysis at 800 °C. The adsorbed amounts of Cu(II) ions and PAM were determined spectrophotometrically. C-SiO2 was characterized using potentiometric titration, microelecrophoresis and Fourier Transform Infrared Spectroscopy (FTIR) analysis. In turn, the C-SiO2 aggregation was established turbidimetrically as well as using a particle size analyzer. The obtained results indicated that both Cu(II) ions and ionic polyacrylamide were adsorbed on the composite surface at pH 6. The highest noted adsorbed amounts were 9.8 mg/g for Cu(II) and 35.72 mg/g for CT PAM-25%. Cu(II) ions increased the anionic PAM adsorbed and reduced the cationic PAM one. The adsorption of anionic PAM (50 ppm) stimulated the solid aggregation significantly. What is more, Cu(II) ions enhanced this process. The size of particles/aggregates formed without additives equaled 0.44 μm, whereas in the mixed Cu(II)/AN PAM system, they were even at 1.04 μm.

Adsorption layer structure on the surface of carbon-silica composite in the presence of proteins of different internal stability and Cu(II) ions – The effect on solid aggregation

The paper focused on the structure of adsorption layer formed on the surface of carbon-silica composite (C-SiO2) in the presence of proteins (ovalbumin (OVA), lysozyme (LSZ)) as well as its impact on the solid aggregation tendency. The composite was characterized using nitrogen adsorption/desorption isotherms method as well as FTIR analysis. In turn, adsorption and aggregation mechanisms were explained based on the results of measurements: zeta potential study, potentiometric titration, CPS analysis and adsorbed amount determination. The experiments were conducted without and with heavy metal ions – copper(II). It was observed that the C-SiO2 composite was a good sorbent relative to proteins, especially at protein isoelectric point (pI), i.e. at pH 5 for OVA and pH 11 for LSZ. For the protein initial concentration equal to 800 mg/L, the adsorbed amount of OVA was 150.6 mg/g (pH 5), whereas that of LSZ was 216.7 mg/g (pH 11). Cu(II) ions reduced the protein adsorption on the composite surface significantly. At pH 5 the adsorbed amount of proteins did not exceed 8.2 mg/g. The strongest aggregation of the C-SiO2 particles was noted in the simultaneous presence of ovalbumin and Cu(II) ions. Then the aggregate diameter equaled 0.152 μm. This phenomenon was enhanced by OVA denaturation caused by heavy metal ions.