Modified Silica Gel Research Articles

Phenylboronic Acid and Amino Bifunctional Modified Adsorbent for Quickly Separating Phenolic Acids from Crude Extract of Clerodendranthus spicatus and Evaluation of Their Antioxidant and Hypoglycemic Activities.

A novel phenylboronic acid and amino bifunctional modified silica gel (SiO2-NH2-FPBA) was prepared, which was 30-80 μm, had a pore size of 8.69 nm, a specific surface area of 206.89 m2/g, was stable at low temperature, and contained 0.4793 mmol/g of the phenylboronic acid group and 1.6377 mmol/g of the amino group. It was used to develop a rapid separation method for phenolic acids. The results showed that it could adsorb 93.64 mg/g caffeic acid, 89.35 mg/g protocatechuic acid and 79.66 mg/g gallic acid. The adsorption process was consistent with the pseudo-second-order model (R2 > 0.99), and fitted the Langmuir isotherm model well (R2 > 0.99). CH3COOH could effectively desorb phenolic acids (>90%) and did not destroy their structures. When SiO2-NH2-FPBA was added to crude extract of Clerodendranthus spicatus, 93.24% of the phenolic acids could be captured, and twenty-two kinds of phenolic acids were identified by Q Exactive HF LC-MS. Furthermore, the isolated phenolic acids from Clerodendranthus spicatus possessed great DPPH, ABTS, and hydroxyl radicals scavenging activities and ferric reducing power. They also demonstrated effective inhibition of α-amylase and α-glucosidase activities (IC50 = 110.63 ± 3.67 μg/mL and 64.76 ± 0.30 μg/mL, respectively). The findings indicate that SiO2-NH2-FPBA has significant potential in practical applications of separating active constituents from natural resources.

Synthesis, Characterization, and Application of Molecularly Imprinted Polymer - Modified Silica Gel for Andrographolide Purification from Andrographis paniculata (Burm.f.) Nees Methanol Extract

Synthesis, Characterization, and Application of Molecularly Imprinted Polymer - Modified Silica Gel for Andrographolide Purification from Andrographis paniculata (Burm.f.) Nees Methanol Extract

Riboflavin and Eosin Y Supported on Chromatographic Silica Gel as Heterogeneous Photocatalysts.

The application of photocatalysis for organic synthesis, both in the laboratory and on an industrial scale, will depend on the achieving of good yields and the ease with which it can be applied. Selective irradiation of the photocatalyst with LED light has made it possible to activate the reactions easily, without the need for UV or heat filters. However, a common problem is the need to separate the photocatalyst from the reaction products through extraction and chromatography isolation processes. These procedures make it difficult to recover and reuse the catalyst, which is not compatible with scale-up applications. Photocatalysts attached to heterogeneous supports resulted in an alternative, which facilitates their removal and reuse. In this study, we use chromatographic silica gel as a low-cost heterogeneous support to bind photosensitizers such as Riboflavin or Eosin Y. The modified silica gel was analyzed by FTIR-ATR and diffuse reflectance UV-visible spectroscopy, thermogravimetric analysis, and optical microscopy. These hybrid materials have a suitable size for easy separation by decantation and were found to be photoactive against two photooxidation reactions. These easy-to-handle materials open the door to effective applications for photoinduced organic synthesis methods at medium to large scale.

Low-Temperature Combustion Synthesis and Characterization of Co-Containing Catalysts Based on Modified Silica Gel

Low-Temperature Combustion Synthesis and Characterization of Co-Containing Catalysts Based on Modified Silica Gel

Study on binding affinity profile, bioactivity, and lipophilicity of selected antipsychotic drugs

Schizophrenia is a complex mental illness that affects almost 1% of the population and has no curative treatment. Currently, available neuroleptic drugs have severe limitations and induce drug-related adverse effects. Receptor binding affinity parameters and lipophilicity are important characteristics that describe the bioactivity of these drugs. Lipophilicity is an important physicochemical property of a drug, which predicts distribution, binding to plasma protein, crossing the blood–brain barrier, and biological activity. Five antipsychotic drugs (Haloperidol, Risperidone, Aripiprazole, Olanzapine, and Quetiapine) were selected and the experimental determination of lipophilicity was carried out by reverse phase thin-layer chromatography (RP-TLC) using four types of stationary phases (RP-18, CN, Diol, and NH2 modified silica gel HPTLC plates) and acetonitrile-water with increasing percentage of acetonitrile and 0.2% formic acid in each case as mobile phase. Lipophilicity parameters (mRM and RM0) calculated from the experimental chromatographic retention data were discussed in terms of the correlation with different receptor binding affinity parameters determined by computational methods.

Dry-column Vacuum Chromatographic Removal of Hg2+ from Wastewater Based on an Acridino-crown Ether-modified Spherical Silica Gel Adsorbent

Dry-column vacuum chromatographic technique is introduced for remediation of wastewater for the first time. A previously prepared chemically modified silica gel containing covalently immobilized Hg2+-selective acridino-crown ether selector molecules was used as an adsorbent. Removal of Hg2+ from highly contaminated river water was carried out to study practical applicability. Adsorption capacity, preconcentration factor, pH-sensitivity and selectivity in separation were determined. The adsorbent proved to be outstanding in selectivity, only Ag+ and Cu2+ interfered among 29 cations, was inert toward organic contaminants, exhibited regenerability and pH-independency between 3.0 ≤ pH ≤ 7.0. The proposed method showed a moderate efficiency in both adsorption (32 mg Hg2+ / 1 g adsorbent) and preconcentration (preconcentration factor of 100). A maximum 10 L of wastewater / 1 g adsorbent ratio is recommended as an upper limit for applicability. The described method showed a unique robustness and simplicity compared to conventional ion-chromatographic methods and an improved selectivity over physical interaction- or simple functional group-based adsorptions.

Insight into the Mechanism of Cobalt-Nickel Separation Using DFT Calculations on Ethylenediamine-Modified Silica Gel.

The separation of Co(II) and Ni(II) from leaching solution is gaining interest because Co(II) and Ni(II) are increasingly used in emerging strategic areas, such as power batteries. Herein, the surface of silica gel is functionalized with 1,2-ethylenediamine and used for the separation of Co(II) and Ni(II). The Co(II) removal efficiency of the modified silica is 80.2%, with a 4-fold improvement in the separation factor. The geometry, frequency, and electrostatic potential of the ethylenediamine modified silica gel (en/SG) are calculated. The corresponding properties of M2+ (M-Co, Ni) adsorbed on en/SG in an aqueous solution are simulated and analyzed. The results show that ethylenediamine tends to form [Men(H2O)4]2+ after binding to M2+, and the binding ability of Co(II) to ethylenediamine is stronger. Besides, the thermodynamic calculations show that en/SG has a more negative Gibbs free energy when absorbing Co(II) in aqueous solution, so en/SG is more inclined to bind with Co(II) preferentially. It is the difference in complexation ability between Ni, Co, and ethylenediamine that enlarges the difference in the original physical adsorption, thus strengthening the separation performance. This work will provide guidance for a rational design of high-performance nickel-cobalt adsorption materials.

Studying the Sorption of Carbon Dioxide by Modified Silica Gel with 2-Hydroxyethylcarbamate

Studying the Sorption of Carbon Dioxide by Modified Silica Gel with 2-Hydroxyethylcarbamate

Studying the Sorption of Carbon Dioxide by Modified Silica Gel with 2-Hydroxyethylcarbamate

The main cause of global warming is the steady increase in greenhouse gases in the atmosphere. The largest share of greenhouse gases is carbon dioxide CO2. Therefore, it is important to efficiently separate it in different gas systems. The article examines the sorption of carbon dioxide from polysilicic acid—silica gels modified with hydroxyethyl carbamate (HEC). It is shown that the modification is optimal in 30% HEC solutions. The fact of modification is confirmed by the presence of amino, hydroxyl, and carbonyl groups in the sorbents. Thermal stability is studied by the thermogravimetric method. Sorption at high pressures is studied by the gravimetric method and sorption at atmospheric pressure is studied by the thermogravimetric method. It is found that the presence of amino groups contributes to the sorption of carbon dioxide by silica gel more than doubling. The highest sorption rates are found to be 8.8% of the mass of the sorbent at 30°C. After five cycles of sorption/desorption processes in sorbents, the maximum sorption capacity decreased by 10%. The sorption rate increases at high pressures of up to 3 atm. Sorbents modified with a 30% HEC solution at 3 atm sorb up to 9.96 mol CO2/g. The relatively fast growth of the sorption rate at high pressures and its relatively slow growth at low pressures prove that the process corresponds to type-2 sorption. Such sorption systems are promising for use in various technological systems containing CO2.

Vacuum-assisted thermal bonding of β-cyclodextrin and its derivatives as chiral stationary phases for high-performance liquid chromatography

In this work, the vacuum-assisted thermal bonding method was proposed for the covalent coupling of β-cyclodextrin (β-CD) (CD-CSP), hexamethylene diisocyanate cross-linked β-CD (HDI-CSP) and 3, 5-dimethylphenyl isocyanate modified β-CD (DMPI-CSP) onto the isocyanate silane modified silica gel. Under vacuum conditions, the side reaction due to the water residue from the organic solvent, air, reaction vessels and silica gel could be avoided, and the optimal temperature and time of vacuum-assisted thermal bonding method were determined as 160°C and 3 h. These three CSPs were characterized by FT-IR, TGA, elemental analysis and the nitrogen adsorption-desorption isotherms. The surface coverage of CD-CSP and HDI-CSP on silica gel was determined as ∼0.2 μmol m−2, respectively. The chromatographic performances of these three CSPs were systematically evaluated by separating 7 flavanones, 9 triazoles and 6 chiral alcohols enantiomers under the reversed-phase condition. It was found that the chiral resolution ability of CD-CSP, HDI-CSP and DMPI-CSP was complementary to each other. Among them, CD-CSP could separate all 7 flavanones enantiomers with the resolution of 1.09–2.48. HDI-CSP had a good separation performance for triazoles enantiomers with one chiral center. DMPI-CSP showed excellent separation performance for chiral alcohol enantiomers, among which the resolution of trans-1, 3-diphenyl-2-propen-1-ol reached 12.01. Generally, the vacuum-assisted thermal bonding had been demonstrated as a direct and efficient method for the preparation of chiral stationary phases of β-CD and its derivatives.

Weak Affinity Chromatography Using Organic Solvents on Cyanopropyl- and Arene-Modified Silica-Gel Columns—Structural Demands for Host and Guest Moieties and Effect of Solvents

Abstract Weak affinity chromatography (WAC) is effective for isolating target compounds from analogous compounds with similar functional groups. Previously, a few chromatographic behaviors based on WAC using organic solvents were observed in a series of cyclic multiporphyrin systems on cyanopropyl-modified silica gel (CN-MS). Here, three cyclic porphyrin trimers with various rigidity were examined on CN-MS to understand the mechanism of the specific interactions between porphyrin derivatives and functional groups on modified silica gel. In addition to CN-MS, six modified silica-gel columns were tested to compare their retention abilities for a cyclic nickel porphyrin dimer (C4Ni2MsCP2). We examined the cosolvent effects of the pyridine eluents for C4Ni2MsCP2. Apparent dissociation constants of C4Ni2MsCP2 with functional groups on the MS columns and effective amounts of the functional groups were estimated by frontal affinity chromatography (FAC). 1H NMR titrations of acetonitrile and nitrobenzene to C4Ni2MsCP2 were conducted to compare their association constants with movable guest molecules to the dissociation constants with immobilized functional groups obtained in FAC. We found rigidity of cyclic porphyrin derivatives and immobilization of functional groups on silica gel is necessary for significant retentions using WAC. The affinity interaction does not occur at the center of C4Ni2MsCP2, but probably occurs on the surface composed of a bipyridyl moiety and the adjacent edges of the two porphyrins. Polar solvents, such as nitrobenzene, acetonitrile, and methanol, weakened the interaction. Although C4Ni2MsCP2 dissolves well in chloroform, the interactions between C4Ni2MsCP2 and the MS columns are considerably strengthened in the presence of chloroform. The competitiveness of solvents and cosolvents with the interaction of the porphyrin on WAC is independent of the solubility of the analyte.

Metalloporphyrins: their multitalented nature as observed in multi-metal complex systems.

Five topics pertaining to the unique chemistry of metalloporphyrins as observed in multi-metal complex systems are introduced. The topics include the following: (i) the unique chromatographic separation of cyclic porphyrins on modified silica gel; (ii) room temperature phosphorescence from the zinc porphyrin part in a zinc porphyrin/rhenium complex hetero dyad; (iii) the substituent effect, in the preparation of a readily soluble special-pair-type zinc porphyrin dimer/rhenium complex having efficient photocatalytic CO2 reduction ability; (iv) assessment of the excited triplet state of a special-pair-type zinc porphyrin dimer in macrocyclic multiporphyrin rings; and (v) solvation/desolvation indicators based on exclusive transformation between the head-head type and head-tail type of supramolecular co-ordination polymers composed of bis(zinc porphyrin)s.

Adsorption removal of styrene on C–Cl grafted silica gel adsorbents

The heat desorption of styrene from adsorbents is impracticable owing to its spontaneous polymerization under heating conditions. However, the feature also brings a potential promoting effect on styrene adsorption. Therefore, it is expected to develop the non-regenerative adsorbents with large adsorption capacity by strengthening the polymerization effect. In this work, C–Cl grafted silica gel adsorbents were prepared by introducing (Chloromethyl)dimethylchlorosilane (CMDMCS) and FeCl2 into silica gel. The C–Cl grafted silica gel exhibited excellent styrene adsorption performance, its adsorption amounts for styrene were 4.67 times and 9 times of unmodified silica gel under dry air condition and high humidity condition (RH = 80%), respectively. In addition, the adsorption of styrene on C–Cl grafted silica gel was almost unaffected by the presence of toluene. The characterization of adsorbents after styrene adsorption indicated that the improvement of adsorption capacity of C–Cl grafted silica gel for styrene can be attributed to atom transfer radical polymerization (ATRP) of styrene molecules on modified silica gel during adsorption process.

Imidazolium-Modified Silica Gel for Highly Selective Preconcentration of Ag(I) from the Nitric Acid Medium

The ion-exchange behavior of an organomineral material with an imidazolium (1-methyl-3-(prop-2-yn-1-yl)-1H-imidazol-3-ium bromide)-modified silica gel was studied for the extraction of Ag(I) from nitric acid media. The extraction from multicomponent systems containing Fe(III), Co(II), Ni(II), Cu(II), Pb(II), and Mn(II) in 100- and 1000-fold molar excesses with respect to Ag(I) was shown to occur with high selectivity. Based on the data of X-ray diffraction and X-ray fluorescence spectroscopy for samples of modified silica gel, a mixed ion exchange–adsorption mechanism for the extraction of Ag(I) was proposed. The effect of the phase contact time and the concentration of nitric acid on the distribution coefficient of Ag(I) was studied. The selectivity factors of the extraction of Ag(I) from multicomponent systems containing foreign cations in 100- and 1000-fold molar excesses under steady-state and dynamic concentration conditions were calculated.

Effect of spacer alkyl chain length on retention among three imidazolium stationary phases under various modes in high performance liquid chromatography

The properties of ionic liquids (ILs) greatly influenced the retention of solutes on IL-functionalized stationary phases. In this work, three IL-functionalized stationary phases (Sil-C4Im, Sil-C7Im, and Sil-C10Im) were prepared by modifying silica gel with three ionic liquid silane reagents differing in spacer alkyl chain lengths, which refers to the alkyl chain between the imidazolium and the sulfur atom. The preparation was proved through a range of characterization techniques, including elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The effects of chromatographic conditions, such as acetonitrile content, salt concentration, pH, and column temperature, were studied to explore the retention mechanism of three stationary phases, which indicates that three IL-stationary phases provide interactions with solutes in reverse-phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC), and ion exchange chromatography (IEC). The column efficiency is 83,686 plates/m for aminobenzoic acid, and the column also has excellent repeatability of retention time with relative standard deviations (RSDs) between 0.24% and 0.34% (n = 12). A variety of analytes, including five nucleosides and nucleobases, six alkylbenzenes, two polycyclic aromatic hydrocarbons (PAHs), and four inorganic anions, were separated well on three IL-functionalized stationary phases. It was found that the spacer alkyl chain length influenced selectivity by comparing the retention of the three IL-functionalized stationary phases.

Efficient and Economic Heparin Recovery from Porcine Intestinal Mucosa Using Quaternary Ammonium-Functionalized Silica Gel

Heparin, usually isolated from porcine intestinal mucosa, is an active pharmaceutical ingredient of great material value. Traditionally, diverse types of commercial resins were employed as an adsorbent for heparin retrieval from biological samples. However, more recent years have encouraged the advent of new cost-effective adsorbents to achieve enhanced heparin retrieval. Inexpensive cationic ammonium-functionalized silica gels, monodispersed with larger surface area, porosity, and higher thermal stability, were chosen to evaluate the heparin recovery yield from porcine intestinal mucosa. We demonstrated that higher positively charged and less bulky quaternary modified silica gel (e.g., QDASi) could adsorb ~28% (14.7 mg g-1) heparin from the real samples. In addition, we also determined suitable surface conditions for the heparin molecule adsorption by mechanistic studies and optimized different variables, such as pH, temperature, etc., to improve the heparin adsorption. This is going to be the first reported study on the usage of quaternary amine-functionalized silica gel for HEP uptake.

Adsorption of Iodine from Aqueous Solution on Modified Silica Gel with Cyclodextrin Derivatives

Adsorption of Iodine from Aqueous Solution on Modified Silica Gel with Cyclodextrin Derivatives

Evolution of Microstructural Characteristics of Carbonated Cement Pastes Subjected to High Temperatures Evaluated by MIP and SEM.

The microstructural evolutions of both uncarbonated and carbonated cement pastes subjected to various high temperatures (30 °C, 200 °C, 400 °C, 500 °C, 600 °C, 720 °C, and 950 °C) are presented in this study by the means of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). It was found that the thermal stabilities of uncarbonated cement pastes were significantly changed from 400 to 500 °C due to the decomposition of portlandite at this temperature range. More large pores and microcracks were generated from 600 to 720 °C, with the depolymerization of C-S-H. After carbonation, the microstructures of carbonated cement pastes remained unchanged below 500 °C and started to degrade at 600 °C, due to the decompositions of calcium carbonates and calcium modified silica gel. At 950 °C, both uncarbonated and carbonated cement pastes showed a loosely honeycombed microstructure, composed mainly of β-C2S and lime. It can be concluded that carbonation improves the high-temperature resistance of cement pastes up to 500 °C, but this advantage is lost at temperatures over 600 °C.

Preparation of new modified silica gel terminated with phenylphosphonic acid-amide moieties for adsorption of uranium(VI) from aqueous solutions

PAMAM dendrimers modified silica gel terminated phenylphosphonic acid-amide moieties (Si-6G PAMAM-PPAAM) was prepared for uranium(VI) adsorption from aqueous solutions by batch and fixed-bed column methods. The experimental results showed that the maximum capacity was 434.78 mg g−1. Equilibrium isotherm data obeyed Langmuir isotherm model. Kinetic adsorption followed pseudo-second order model and thermodynamic parameters implied the adsorption was spontaneous, endothermic. The adsorption performance of the new adsorbent toward uranium using fixed-bed column method was also investigated. The investigated adsorbent (Si-6G PAMAM-PPAAM) was successfully used to extract uranium from leach liquor of granitic rock sample.

MODIFIKASI SILIKA GEL DARI ABU LIMBAH HASIL PROSES PEMBAKARAN INDUSTRI BATU BATA DENGAN DIFENILKARBAZON SEBAGAI ADSORBEN SERTA UJI DAYA SERAP TERHADAP ION LOGAM Cr(III) DAN Cu(II)

The modification of silica gel, from the waste of the bricks burning process, with diphenylcarbazone has been done. The silica gel modified by diphenylcarbazone (Si-DPZon) was obtained by boiling the ash with NaOH solution to create sodium silicate and neutralized with HCl to get the silica gel, then physically modified with diphenylcarbazone ligand. The study included the determination of the adsorbent functional groups by spectrophotometer IR, surface acidity by acid-base titration method, specific surface area by absorption of methylene blue method, the optimum conditions (pH, contact time) of the adsorption of Cr(III) and Cu(II). FTIR analysis showed that the Si-DPZon contained amide (N-H), carbonyl (C=O), silanol (Si-OH), siloxane (Si-O-Si) and aromatic (C-H) functional groups. The results showed that Si-DPZon had a surface acidity (Kal) of 5.8384 ± 0.2466 mmol/g with the number of active sites of 12.3945x1020 atom/g with a specific surface area of 12.6886 m2/g. Si-ABB had a surface acidity (Kal) of 4.5568±0,2453 mmol/g with the number of active sites of 27.4410x1020 atom/g and with a specific surface area of 11.6712 m2/g. The optimum conditions for adsorption of chromium (III), both Si-DPZon and Si-ABB occurred at pH 5 and 15 minutes. The adsorption ability of Cr(III) by Si-DPZon at the pH and contact time optimum conditions was 34.6927 mg/g with an adsorption percentage of 86.7317% and Si-ABB was obtained at 34.5445 mg/g with the adsorption percentage of 86.3611%. Adsorption ability of Cu(II) by Si-DPZon at the pH and contact time optimum conditions was 26.49672 mg/g with the adsorption percentage of 66.2418% and Si- ABB was obtained at 24.93210 mg/g with the adsorption percentage of 62.3302%.
 Keywords: adsorptions, chromium (III), copper (II), diphenilcarbazone ligand, synthesis of silica gel.