Immobilized Silica Gel Research Articles

Thermo‐Kinetic Study of Piperazine Immobilized Silica Surface

AbstractIn the present study, the degradation process of piperazine (PP) immobilized silica gel (SiPP) is investigated under dynamic conditions. The degradation of SiPP is studied with thermogravimetric analyzer (TGA). The kinetics of degradation process is analyzed by Kissinger method, Flynn–Wall–Ozawa's (FWO) method, and Deconvolution method. It is found that degradation of SiPP can be described by parallel independent two‐portion process model, which includes two processing state of the system (marked by processes 1 and 2), where process 1 and 2 can be attributed to decomposition processes of organic moiety attached on silica surface. The apparent activation energy (Ea) is calculated by Flynn–Wall–Ozawa's (FWO) method and deconvolution method.

The removal of chromium (VI) from tannery waste using Spirulina sp. immobilized silica gel.

The use of microalgae biomass is an alternative solution to the problem of environmental pollution due to heavy metals, one of which is Cr metal in leather tanning liquid waste. However, the ability of biomass to adsorb heavy metals has limitations. Therefore, the algal biomass is immobilized with silica gel in order to obtain a stable structure. This research aims to study the absorption efficiency of Cr (VI) metal by the biomass of Spirulina sp. which is immobilized with silica gel from the tannery liquid waste. The preparation stages in this study were adsorbent preparation, immobilization of biomass with silica gel, and preparation of tannery liquid waste. Furthermore, the research treatment was carried out to determine the effect of the independent variable on the adsorption of Cr (VI). Characteristics of functional groups using FTIR show the biomass constituent of Spirulina sp. immobilized containing amino, carboxylate, and hydroxyl groups. The results showed that the optimum contact time required for adsorption of Cr (VI) ions was 60 min of immersion and the optimum pH value was 3. Adsorption of Cr (VI) ions followed Freundlich adsorption isothermal and included in the pseudo second order adsorption kinetics.

New approach for removing co-extracted lipids before mass spectrometry measurement of persistent of organic pollutants (POPs) in foods

Persistent organic pollutants (POPs) methods for foods and animal feeds require sufficient sample intake followed by an extensive removal of interfering matrix components and concentration before a gas chromatographic mass spectrometry (GC-MS) method can be applied. The extraction dissolves associated lipids in animal foods or feeds. Methods must eliminate all co-extracted lipids before determination by GC-MS. A new approach for removing lipids is presented using basic silica gel or metal ion immobilized silica gel (Ag+) in a single step. Absorbent order, adsorbent amounts, and flow rates were found to be essential for consistent results. KOH/silica gel or Ag+ ion (AgNO3) silica gel were both shown to retain 75–85% of the co-extracted lipids without using sulfuric acid. KOH/silica gel method applied to butter fortified at 7.3 pg TEQ/g lipid with polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) produced accurate results for all fortified congeners with 20% of predicted (n = 6). Ag+ silica gel incorporated into the Miura GO-EHT automated system produced similar results fortified at 3 pg TEQ/g lipid. During PCDD/F fortifications of butter with PCDD/Fs (n = 6), labeled standard recoveries for PCDD/Fs and planar polychlorinated biphenyls (PCBs) were all acceptable (52–99%) averaging 77% using the Miura system. A reduction in the amounts of sulfuric acid silica gel needed was possible in the completion of co-extractant removal. PCDD/F spikes into butter and for a spiked sunflower oil (PCDD/Fs and coplanar PCBs) were within ± 20% of the predicted using the Miura system; suitable for current methods criteria for foods including criteria in EU legislation.

Selective extraction and detection of noble metal based on ionic liquid immobilized silica gel surface using ICP-OES

In this study, an efficiently employed ionic liquid combined with commercially available silica gel (SG–ClPrNTf2) was developed for selective detection of gold(III) by use of inductively coupled plasma–optical emission spectrometry (ICP-OES). The selectivity of SG–ClPrNTf2 was evaluated towards seven metal ions, including Y(III), Mn(II), Zr(IV), Pb(II), Mg(II), Pd(II) and Au(III). Based on pH study and distribution coefficient values, the SG–ClPrNTf2 phase was found to be the most selective towards Au(III) at pH 2 as compared to other metal ions. The adsorption isotherm of Au(III) on the SG–ClPrNTf2 phase followed the Langmuir model with adsorption capacity of 59.48 mg g−1, which was highly in agreement with experimental data of adsorption isotherm study. The kinetics study indicated that Au(III) adsorption kinetics data were well fit with the pseudo-second-order kinetic model on the basis of correlation coefficient fitting (0.996) and adsorption capacity agreement (62.26 mg g−1). Furthermore, SG–ClPrNTf2 phase was effectively performed for the determination of Au(III) in real water samples with satisfactory results.

Schiff base immobilized silica gel framework as an efficient sorbent for preconcentration of Pb and Zn ions in aqueous media

A novel preconcentration method for Pb and Zn ions using a column packed with Schiff base modified silica gel is described. The method was based on the sorption of analytes on N,N'-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel and elution with HNO$_{3}$ prior to flame atomic absorption analysis. The parameters pH, flow rate, sample volume, eluent volume, and concentration were optimized using a central composite design. The detection limits were 10.0 $\mu $g L$^{-1}$ for Pb and 1.1 $\mu $g L$^{-1}$ for Zn. The suggested procedure was validated with Lake Ontario water as a certified reference material and recovery percentages were 101.8% for Pb and 98.2% for Zn. The application of the method was performed on snow, tap, bottled, mineral, and lake water samples and recovery percentages were in the range of 96.7%-101.6% and 96.4%-98.4% for Pb(II) and Zn(II), respectively.

Highly Selective Separation and Enrichment of Phosphopeptides by Uranyl-Salophen Immobilized Silica Gel Material

The characterization of phosphoproteins requires highly specific methods for the separation and enrichment of phosphopeptides. Here we report a novel metal ion-immobilized solid phase material for the separation and enrichment of phosphopeptides. The material is uranyl-salophen-silica gel (USSG) particles in which salophen is a tetradentate ligand of uranyl ion. In USSG salophen is connected on the surface of silica gel and uranyl is bound on the surface through its coordination with salophen. Phosphopeptides can be selectively retained by USSG because uranyl-salophen can bind phosphate moiety with strong affinity and high selectivity. The new material USSG has been successfully used for the separation of phosphopeptides from peptide mixtures with the separation efficiency of 97.0% to 97.4%.

Enantioselective Separation and Detection of D-Phenylalanine Based on Newly Developed Chiral Ionic Liquid Immobilized Silica Gel Surface

Enantioselective Separation and Detection of D-Phenylalanine Based on Newly Developed Chiral Ionic Liquid Immobilized Silica Gel Surface

Selective extraction of Cr3+ by aniline immobilized silica gel

Selective extraction of Cr3+ by aniline immobilized silica gel

The synthesis of cyclohexenone using l-proline immobilized on a silica gel catalyst by a continuous-flow approach

A facile and convenient method for the synthesis of cyclohexenone compounds was developed using an L-proline immobilized silica gel catalyst combined with a continuous-flow approach. Because of the mild reaction conditions, ease of catalyst recyclability, and product isolation, this reaction approach can potentially be used in a facile scale-up reaction or in industrial applications.

Synthesis of novel aniline immobilized silica gel for the selective extraction of Cr(III)

Aniline moiety was immobilized on the surface of silica gel (SG) through functionalizing the later by 3-chloropropyl trimethoxysilane (3-CPTS). The aniline immobilization was confirmed by chemical, Fourier transform infrared (FTIR), thermo gravimetric analysis (TGA), and scanning electron microscopy (SEM). Solid phase extraction (SPE) property of the synthesized product was studied in terms of Cr(III) uptake by batch and column methods. Metal ion adsorption and its isotherm, kinetic and thermodynamic parameters were evaluated. The mechanistic path involved in up taking metal ion has been suggested. The Cr(III) binding capacity was found to be 8.7 mg g−1 at trace level of chromium in aqueous medium. The presence of chloride ion improved the metal ion binding capacity as well as selectivity to a significant extent. The developed material and the selective extraction method were tested by applying it in real samples and the results were compared with the reported values.

Photocatalytic detoxification of aqueous organophosphorus by TiO2 immobilized silica gel

Photocatalytic degradation of organophosphorus compounds including organophosphonic and organophosphinic acids by TiO2 immobilized silica gel in a water phase was carried out. Photocatalytic degradation of parent organophosphorus compounds and formation of intermediates were observed and the photocatalytic degradation scheme for each pesticide is proposed. Overall, the photocatalytic degradation of organophosphorus compounds in aqueous phase was estimated to form organophosphoric (organophosphonic and organophosphinic) acids as intermediates of the reaction. These organophosphoric acid intermediates were selectively adsorbed onto TiO2 surface and as a result, elution of these compounds into the aqueous phase was not observed. Similarly, after photocatalytic degradation, H3PO4 was either not observed or slightly observed as the final product. Likewise, rapid adsorption of the studied parent organophosphoric acids on TiO2 surface resulted in significant reduction in the concentration of these compounds even under dark condition. Upon UV irradiation, total organic carbon (TOC) level increased, and this is indicating the elution of some organic intermediates into the aqueous phase. However, these organic intermediates were eventually degraded with the UV irradiation.

Dithizone immobilized silica gel on-line preconcentration of trace copper with detection by flame atomic absorption spectrometry

A novel adsorbent-silica gel bound dithizone (H2Dz-SG) was prepared and used as solid-phase extraction of copper from complex matrix. The H2Dz-SG is investigated by means of FT-IR spectra and the SEM images, demonstrating the bonding of dithizone. The H2Dz-SG quantitatively adsorb copper ions, and the retained copper is afterwards collected by elution of 10% (v/v) nitric acid. An on-line flow injection solid-phase extraction procedure was developed for trace copper separation and preconcentration with detection by flame atomic spectrometry. By loading 5.4mL of sample solution, a liner range of 0.5–120μgL−1, an enrichment factor of 42.6, a detection limit of 0.2μgL−1 and a precision of 1.7% RSD at the 40μgL−1 level (n=11) were obtained, along with a sampling frequency of 47h−1. The dynamic sorption capacity of H2Dz-SG to Cu2+ was 0.76mgg−1. The accuracy of the proposed procedure was evaluated by determination of copper in reference water sample. The potential applications of the procedure for extraction of trace copper were successfully accomplished in water samples (tap, rain, snow, sea and river). The spiking recoveries within 91–107% are achieved.

Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin–Raduskevich (D–R) isotherms. The mean sorption energy ( E) of copper sorption onto silica gel was calculated from D–R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.

Sorption and Desorption of Lead on 5-Amino-1,3,4-Thiadiazole-2-Thiol Immobilized Silica Gel by Flame Atomic Absorption Spectrometry (FAAS)

Silica gel was modified by 5-amino-1,3,4-thiadiazole-2-thiol via homogeneous routes to obtain immobilized silica gel sorbent (ATT-immobilized silica gel). This sorbent was characterized using a variety of physical chemical techniques including, high resolution solid state 13C CP/MAS NMR, X-ray photoelectron spectroscopy (XPS), thermal analysis (TGA and DTA), elemental analysis, and BET surface analysis, as well as infrared spectroscopy (FTIR). The support was used for sorption and desorption of leadions by silica gel modified with 5-amino-1,3,4-thiadiazole-2-thiol from aquatic samples and their determination with FAAS. Lead ions can be desorbed with 0.001 mol dm−3 EDTA. The sorption capacity for lead ions is found to be in the range of 48.20–49.50 µmol g−1(about 10.14 mg L−1) of chelating matrix. Tolerance limits for electrolytes in the sorption of lead are reported. Experimental data obtained from batch equilibrium tests have also been analyzed by Langmuir isotherm and the Freundlich equation. Theoretically, maximum monolayer adsorption capacity was obtained to be 14.28 for ATT-immobilized silica gel. Pb(II) sorption on ATT-immobilized silica gel was found favorable according to the Langmuir isotherm and the Freundlich equation.

Synthesis, characterization, and sorption properties of silica gel-immobilized Schiff base derivative

Silica gel was derivatized with benzophenone 4-aminobenzoylhydrazone (BAH), a Schiff base derivative, after silanization of silica by 3-chloropropyltrimethoxysilane (CPTS) by using a reported method. Characterization of the surface modification was confirmed through infrared spectroscopy, thermogravimetry, and elemental analysis. The immobilized surface was used for Cu(II), Ni(II), Zn(II), and Co(II) sorption from aqueous solutions. The influence of the amount of sorbent, ion concentration, pH, and temperature was investigated. The sorption data followed Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherms. The mean sorption energy ( E) of benzophenone 4-aminobenzoylhydrazone (BAH) immobilization onto silica gel was calculated from D–R isotherms, indicating a chemical sorption mode for four cations. Thermodynamic parameters, i.e., Δ G, Δ S, and Δ H, were also calculated for the system. From these parameters, Δ H values were found to be endothermic: 27.0, 22.7, 32.6, and 34.6 kJ mol −1 for Cu(II), Ni(II), Co(II), and Zn(II) metal ions, respectively. Δ S values were calculated to be positive for the sorption of the same sequence of divalent cations onto sorbent. Negative Δ G values indicated that the sorption process for these three metal ions onto immobilized silica gel is spontaneous.

Solid Phase Extraction and Determination of Lead in Water Samples Using Silica Gel Homogeneously Modified by Thiosalicylic Acid

Silica gel was modified by thiosalicylic acid via homogeneous routes to obtain immobilized silica gel sorbent (TSA‐immobilized silica gel). This new sorbent was characterized using variety of physical chemistry techniques including, high resolution solid state 13C and 29Si CP/MAS NMR, X‐ray photoelectron spectroscopy (XPS), thermal analysis (TGA and DTA), elemental analysis, and BET surface analysis as well as infrared spectroscopy (FTIR). New support was used for the selective extraction and concentration of lead ions by silica gel modified with thiosalicylic acid, as a highly selective and stable reagent, from aquatic samples and its determination with FAAS. Lead ions can be desorbed with 4 mol dm−3 HNO3. The sorption capacity for lead ions are found in the range of 64.40 to 69.90 µmol g−1 of chelating matrix. Tolerance limits for electrolytes and some trace metals in the sorption of lead is reported. Preconcentration factor was found as 150 for Pb(II). The lead in drinking water, mineral water, tap water, and fruit juice was quantitatively recovered with a relative standard deviation lower than 1.50%. A detection limit of the method for lead ions was found as 3.7 µg l−1.

Selective detection of trace lead in lead-free solder alloy by flow injection on-line solid-phase extraction using a macrocycle immobilized silica gel as sorbent coupled with hydride generation atomic fluorescence spectrometry

As lead-free solder is a tin-based alloy, and contains large amounts of tin, copper or other metals that can cause serious interferences with hydride generation, accurate determination of trace lead in lead-free solder by hydride generation atomic fluorescence spectrometry (HG-AFS) is challenging. In this work, a flow injection (FI) on-line solid phase extraction (SPE) technique was coupled to HG-AFS for selective determination of lead in lead-free solder. Macrocycle immobilized silica gel with high selectivity for lead was employed as the sorbent to eliminate interferences from other heavy metals and hydride-forming elements on HG-AFS determination of lead. At least 500 mg L−1of Cu(II), Fe(III), Ni(II), Zn(II), Cr(II), Ca(II), Al(III), Cd(II), Co(II) and Ag(I), 200 mg L−1 of Sn(II), 100 mg L−1 of As(III), Hg(II), Se(IV) and Sb(III), and 50 mg L−1 of Ba(II) had no interferences on the determination of 0.5 μg L−1 Pb(II). With a sample loading flow rate of 4.8 mL min−1 for 60 s on-line SPE, a detection limit (3s) of 3 ng L−1 and an enhancement factor of 61 was obtained. The precision (RSD, n = 11) was 1.8% at the 0.5 μg L−1 Pb(II) level. The developed method allows cost-effective, sensitive, accurate and interference-free determination of trace lead in lead-free solder samples.

Preparation of Poly(Propyleneimine) Dendrimer Immobilized Silica Gel and its Application as Novel Microcolumn Packing for the On‐Line FI Preconcentration and Separation of Platinum

A G4.0 poly(propyleneimine) dendrimer immobilized silica gel (PPID-SG) was prepared with a divergent approach from gamma-aminopropyl silica gel (APSG) by repeating the reactions: 1) cyanoethylation of -NH2 and 2) reduction of -CN. Then it was successfully applied as the microcolumn packing for the on-line flow-injection (FI) preconcentration and separation and flame atomic absorption spectrometry (FAAS) determination of Pt. A limit of detection (LOD) of 0.014 microg/mL was obtained when 0.5 microg/mL Pt in chloride acid of PH = 3 was preconcentrated with a sample flow rate of 4.6 mL/min for 60s and the relative standard deviation (RSD) was 2.65%. Coexisting metal ions with concentration of 5.0 mg/mL and anion ions of 20.0 mg/ml have no interference in the determination of Pt. The proposed method was successfully applied to the determination of Pt in nickel alloy and anode slime samples.

The Oxidation of Alcohols in N‐Oxyl‐Immobilized Silica Gel/Aqueous NaOCl Disperse Systems. A Prominent Access to a Column‐Flow System.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Oxidation of Alcohols in N-Oxyl-Immobilized Silica Gel/Aqueous NaOCl Disperse Systems. A Prominent Access to a Column-Flow System

Abstract The oxidation of alcohols was performed successfully in a disperse system with N-oxyl-adsorbed or immobilized silica gel as a disperse phase and aqueous NaOCl as a disperse medium. In the disperse system, the oxidation of sec-alcohols afforded the corresponding ketones, while prim-alcohols were oxidized to aldehydes and/or carboxylic acids depending on their structures and reaction conditions. The N-oxyl-immobilized silica gel was recovered and repeatedly used without a significant change in the product yields. A column-flow system was also investigated for the oxidation of alcohols by use of a newly devised column packed with the N-oxyl-immobilized silica gel.