Silica gel-immobilized-dithioacetal derivatives as potential solid phase extractors for mercury(II)

Dithioacetal derivatives with different para-substituents, XH, CH(3), OCH(3), Cl and NO(2) were synthesized and chemically immobilized on the surface of silica gel for the formation of five newly synthesized silica gel phases (I-V). Characterization of the silica gel surface modification by the organic compounds was accomplished by both the surface coverage determination as well as the infrared spectroscopic analysis. The metal sorption properties of the silica gel phases were studied to evaluate their performance toward metal-uptake, extraction and selective extraction processes of different metal ions from aqueous solutions based on examination of the various controlling factors. The studied and evaluated factors are the pH effect of metal ion solution on the metal capacity values (mmol g(-1)), equilibration shaking time on the percent extraction as well as the structure and substituent (X) effects on the determined mmol g(-1) values. The results of these studies revealed a general rule of excellent affinity of these silica gel phases-immobilized-dithioacetal derivatives for selective extraction of mercury(II) in presence of other interfering metal ions giving rise to a range of 94-100% extraction of the spiked mercury(II) in the metal ions mixture. The potential application of the newly synthesized silica gel phases (I-V) for selective extraction of mercury(II) from two different natural water samples, namely sea and drinking tap water, spiked with 1.0 and 10.0 ng ml(-1) mercury(II) were also studied by column technique followed by cold vapour atomic absorption analysis of the unretained mercury(II). The results indicated a good percent extraction and removal (90-100+/-3%) of the spiked mercury(II) by all the five silica gel phases. In addition, insignificant contribution by the matrix effect on the processes of selective solid phase extraction of mercury(II) from natural water samples was also evident.     

Study of the selective extraction of iron (III) by silica-immobilized 5-formyl-3-arylazo-salicylic acid derivatives

A method for immobilization of 5-formyl-3-arylazosalicylic acid derivatives on the surface of silica gel is described. The new silica gel phases were synthesized by a very simple and rapid route which can be defined as a one-step reaction. The phases were proved to show an excellent improvement in the iron (III) extraction and the determined mmol g(-1) values are in the range of 1.24 - 1.32. The metal-uptake properties of eleven metal ions were also evaluated at different pH values and shaking times. The process of selective extraction of iron (III), in presence of an interfering ion, by these phases was also studied by both column and batch equilibrium techniques in order to identify the possible type of interference of each metal ion in this process. Three divalent metal ions (Mg, Ca and Mn) exhibited a minimum interference in iron (III) extraction. A group of six divalent metal ions (Co, Ni, Cu, Zn, Cd and Pb) were found to be interfering in the selective extraction of iron (III) via the arylazo-moiety of the silica phase, while Cr(III) was found to show a specific interference type based on the affinity of Cr(III) for binding to the chelation centers of the salicylic acid moiety of the silica phase.     

Synthesis, characterization of silica gel phases-chemically immobilized-4-aminoantipyrene and applications in the solid phase extraction, preconcentration and potentiometric studies.

Two new 4-aminoantipyrene chemically-immobilized silica gel phases: ii (N,N-donor) and iii (N,O-donor), were synthesized and characterized by IR and surface coverage determination. The latter was accomplished by thermal desorption and metal probe methods, giving 0.300 and 0.312 mmol g(-1) for ii and 0.220 and 0.250 mmol g(-1) for iii. Moreover, potentiometric titration provided a surface coverage of 0.323 mmol g(-1) for ii. The metal capacity values in mmol g(-1) of ii, iii and the active silica gel phase i for a series of di- and trivalent metal ions were determined at pH 1.0 - 6.7. Phase i showed the lowest values, while ii and iii reflected higher affinity toward most of the metal ions. The highest values were 0.300 for Hg(II)-ii and 0.220 mmol g(-1) for Cd(II)-iii. Distribution coefficients (log Kd) were in the range of 3.57 - 4.76 for ii and 2.32 - 3.46 for iii, thus confirming certain selectivity characters of the solid extractors. The application of the phases as solid extractors and preconcentrators for some heavy metal ions is presented. Good percentage extraction and removal of 94 - 98 +/- 4 - 6% of the spiked 1.000 microg ml(-1) of Hg(II), Cd(II), Pb(II), Cu(II) and Zn(II) and good percentage recovery of 94 - 99 +/- 3 - 6% of 50 ng ml(-1) of these ions from tap water samples were obtained. Stability constants of H(I) and Cu(II) with ii for the two-phase mixture at 25 degrees C and I = 0.1 (KCI) were determined potentiometrically. The pKa of ii are 5.6 and 8.4, while the log K values for CuHL and CuL (L = ii) are 6.3 and 5.8, respectively, leading to the determination of several analytical data for Cu(II)-ii.     

Synthesis and Metal Collecting Properties of Mono,Di, Tri and Tetramine Based on Silica Gel Matrix

Abstract

Silica gels, chemically modified with mono, di, tri and tetramine (I - IV), were synthesized. The monoamine (I) was produced directly via the reaction of silica gel with 3-aminopropyltrimethoxysilane. The diamine (II), triamine (III) and tetramine (IV) were produced through the reaction of ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA) with 3-chloropropyltrichloromethane modified silica gel, respectively. The sorption properties of the phases (I - IV) toward Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) were investigated at different pH-values based on the batch equilibrium technique, The, metal uptake capacities (mmol/g) were determined and discussed in terms of the structure of the aliphatic amines and the increasing number of nitrogen donor atoms. The metal capacity values demonstrate the higher efficiency of phases III and IV than phases I and II for preconcentration of such metal ions. Moreover, the use of phases III and IV for selective extraction of Cu(II) and Ni(II) is promising.     

Silica-immobilized formylsalicylic acid as a selective phase for the extraction of iron(III)

The immobilization of formylsalicylic acid compounds on the surface of amino group-containing silica gel phases is described. The resulting phases were tested for the extraction of iron(III) and showed an exchange capacity of 0.95-0.96 mmol g(-1). The other metal ions tested showed lower metal capacity values than iron(III). The selectivity of the phases tested for the extraction of iron(III) from a mixture containing several other metal ions was evaluated using atomic absorption spectrometry. A method for the recycling of immobilized silica gel after metal extraction is described for practical applications.     

Silica gel-immobilized Eriochrome black-T as a potential solid phase extractor for zinc (II) and magnesium (II) from calcium (II)

The immobilization of silica gel surface with Eriochrome black-T indicator (ERT) for the formation of silica-ERT phase is described. The surface coverage of silica gel, based on carbon and nitrogen analysis of the modified silica gel phase, is 0.38 mmol g(-1). The stability towards hydrolysis of silica-ERT phase in different buffer solutions (pH 1-10) is studied and evaluated. The applicability of silica-ERT as a solid phase extractor for Zn(II), Mg(II) and Ca(II) is studied by the batch equilibrium technique and found to show an order similar to the formation constant values of these three metal ions with the indicator. The selectivity of silica-ERT phase towards the extraction of a certain metal ion from a mixture containing only two metal ions is studied by the batch equilibrium technique and exhibited good discrimination orders for Zn(II) and Mg(II) in presence of Ca(II). The results of the column separation and preconcentration studies are consistent with the selectivity behaviour of silica-ERT phase, thus affording reasonable separation of the three studied metal ions.     

Selective retention of basic compounds by metal aquo‐ion affinity chromatography

A novel metal aquo‐ion affinity chromatography has been developed for the analysis of basic compounds using heat‐treated silica gel containing hydrated metal cations (metal aquo‐ions) as the packing material. The packing materials of the metal aquo‐ion affinity chromatography were prepared by the immobilization of a single metal component such as Fe(III), Al(III), Ag(I), and Ni(II) on silica gel followed by extensive heat treatment. The immobilized metals form aquo‐ions to present cation‐exchange ability for basic analytes and the cation‐exchange ability for basic analytes depends on pK_a of the immobilized metal species. In the present study, to evaluate the retention characteristics of metal aquo‐ion affinity chromatography, the on‐line solid‐phase extraction of drugs was investigated. Obtained data clearly evidence the selective retention capability of metal aquo‐ion affinity chromatography for basic analytes with sufficient capacity.     

Selective Pre-concentration and Solid Phase Extraction of Mercury（Ⅱ） from Natural Water by Silica Gel-loaded （E）-N-（1-Thien-2＇-ylethylidene）-1,2-phenylenediamine Phase

Silica gel-loaded （E）-N-（1-thien-2＇-ylethylidene）-1,2-phenylenediamine （TEPDA） phase was synthesized based on physical adsorption approaches. The stability of a chemically modified TEPDA especially in concentrated hydrochloric acid that was then used as a recycling and preconcentration reagent allowed the further uses of silica gel-loaded immobilized TEPDA phase. The application of this silica gel-loaded phase to sorption of a series of metal ions was performed by using different controlling factors such as the pH of the metal ion solution and the equilibration shaking time by the static technique. This difference was interpreted on the basis of selectivity incorporated in these sulfur containing silica gel-loaded TEPDA phases. Hg（Ⅱ） was found to exhibit the highest affinity towards extraction by these silica gel-loaded TEPDA phases. The pronounced selectivity was also confirmed by the determined distribution coefficients （Kd） of all the metal ions, showing the highest value reported for mercury（Ⅱ） extraction by the silica gel immobilized TEPDA phase. The potential applications of the silica gel immobilized TEPDA phase to selective extraction of mercury（Ⅱ） from aqueous solution were successfully accomplished and preconcentration of low concentration of Hg（Ⅱ） （30 pg·mL^-1） from natural tap water with a preconcentration factor of 200 for Hg（Ⅱ） off-line analysis was conducted by cold vapor atomic absorption analysis.     

Selective solid phase extraction and preconcentration of iron(III) based on silica gel-chemically immobilized purpurogallin

The immobilization of purpurogallin on the surface of amino group containing silica gel phase for the formation of a newly synthesized silica gel-bound purpurogallin (SGBP) is described. The surface modification was studied and evaluated by determination of the surface coverage value by both the elemental analysis and metal probe testing method, which was found to be 0.485 and 0.460 mmol g⁻¹, respectively. The metal sorption properties of SGBP were examined by a series of di- and tri-valent metal ions. The metal capacity values (mmol g⁻¹) for this series of metal ions were also determined under different buffer solutions (pH 1.0–6.0) as well as shaking times by the batch equilibrium technique. The results of this study confirmed the strong affinity and selectivity as well as the fast equilibration and interaction processes of SGBP and Fe(III) compared to the other tested metal ions. The reduction–oxidation process of iron(II)/iron(III) by SGBP was also studied and the results indicated only 2.1% reduction of iron(III) into iron(II). The selectivity incorporated into silica gel phase via the immobilization of purpurogallin was intensively studied for a several binary mixtures containing iron(III)—another interfering metal ion. The determined percentage extraction values of iron(III) from these mixtures were found to be in the range of 94–100%. The potential applications of SGBP as a selective solid extractor for iron(III) from natural tap water samples and real matrices were also studied and the results revealed good percentage extraction values of iron(III) (93.5−94.9±4.6−5.3%) of the spiked iron(III) in the acidified tap water samples as well as a high preconcentration factor of 500 was also established when SGBP was used as a selective solid phase extractor and preconcentration of iron(III) from acidified soft drink samples with percentage recovery values of (98.0−97.4±4.7−5.3%) of the spiked iron(III).     

Synthesis, characterization and structure effects on selectivity properties of silica gel covalently bonded diethylenetriamine mono- and bis-salicyaldehyde and naphthaldehyde Schiff(,)s bases towards some heavy metal ions

Four silica gel-immobilized new metal chelate Schiff(,)s bases were synthesized (I-IV). Silica gel chemically bonded diethylenetriamine mono-naphthaldehyde and mono-salicyaldehyde Schiff's bases (phases I and III) were produced via the interaction of silica gel-modified diethylenetriamine with naphthaldehyde and salicylaldehyde, respectively. However, phases II and IV arose through the interaction of bis-naphthaldehyde and bis-salicylaldehyde Schiff(,)s bases of diethylenetriamine with 3-chloropropyltrimethoxysilane modified silica gel. The characterization of such new phases, their capabilities towards selective extraction or separation of Fe(III), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions were studied and evaluated by both batch and column techniques as a function of pH and time of contact. Phases III and I showed high performance towards Cu(II) extraction, where their Cu(II) sorption determined to be 0.957 and 0.940 mmol g(-1), respectively. However, for phases IV and II, the great affinity was devoted to Fe(III) extraction followed by Cu(II) ions. The reactivity of metal ion sorption was discussed in the light of effects of bulkiness as well as orientation of immobilized chelate on sorbent reactivity. Donor sites of phases III and I (diethylenetriamine and azomethene nitrogens along with phenolic hydroxyl group oxygen) are fully active, whereas phases IV and II are partially active with only participation of oxygen and azomethene nitrogen. The order of increasing thermal stability (IV相似文献   

Aspects of surface modification, structure characterization, thermal stability and metal selectivity properties of silica gel phases-immobilized-amine derivatives

Four silica gel phases-bound-amine derivatives (I-IV) were prepared based on chemical immobilization technique. The surface modification was identified by determination of the coverage values in mmol g⁻¹ via thermal desorption method (1.463-1.807) and elemental analysis of nitrogen and carbon contents (1.089-2.456). Structure characterization related to immobilization of the amine derivatives was accomplished and evaluated by means of infrared (IR) and secondary ion mass spectrometric (SIMS) technique. The modified silica gel phases (I-IV) along with their interaction products with copper(II) were also examined by electron impact mass spectrometric analysis (EI-MS) as a method for evaluation of their thermal stability and structure elucidation. Potentiometric titration as a method of characterization was applied for the modified silica gel phases (II-IV) and their copper(II)-adduct. A series of bi- and trivalent metal ions were selected to focus more aspects of the selectivity properties incorporated into the modified silica gel phases for binding and interaction with these metals based on determination of the distribution coefficient and separation factor. The results of these evaluation processes were found to prove higher selectivity and preference of these four phases for binding with lead(II) and cadmium(II) compared to other metal ions.     

Selective separation of silver(I) and mercury(II) ions in natural water samples using alumina modified thiouracil derivatives as new solid phase extractors

A simple and reliable solid-phase extraction (SPE) method has been developed to synthesise two new sorbents: 6-propyl-2-thiouracil and 5,6-diamino-2-thiouracil physically loaded onto alumina surface, phases I and II, respectively. The synthesis of these new phases has been confirmed by IR-spectroscopy. The surface concentrations of the organic moieties were determined to be 0.182 and 0.562 mmol g^?1 for phases I and II, respectively. The evaluation of the selectivity and metal uptake properties incorporated in these two alumina phases were also studied and discussed for 10 different metal ions: Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pb(II) and Ag(I) under different controlling factors. The data obtained clearly indicated that the new SP-extractors have the highest affinity for retention of Hg(II) ions. Selective separation of Hg(II) from Ag(I) as one of the most interfering ion, in addition to the other eight coexisting metal ions under investigation, was achieved successfully using the new sorbents at pH = 9.0 under static conditions. Therefore, Hg(II) exhibits major retention percentage (100.0%) using phase I or II. However, Ag(I) exhibits minor retention percentage equal to 1.33% using phase I and 0.67% using phase II. On the other hand, the retention percentage of the other eight metal ions ranged (0.0–3.08%) using phase I and (0.0–1.54%) using phase II at the same pH. The new phases were applied for separation and determination of trace amounts of Hg(II) and Ag(I) spiked natural water samples using cold vapour atomic absorption spectroscopy and atomic absorption spectroscopy with no matrix interference. The high recovery values of Hg(II) and Ag(I) obtained using phases I and II were ranged 98.9 ± 0.1–99.2 ± 0.05% along with a good precision (RSD% 0.01–0.502%, N = 3) demonstrate the accuracy and validity of the new sorbents for separation and determination of Hg(II) and Ag(I).     

Selective Solid Phase Extraction and Pre-Concentration of Heavy Metals from Seawater by Physically and Chemically Immobilized 4-Amino-3-Hydroxy-2-(2-Chlorobenzene)-Azo-1-Naphthalene Sulfonic Acid Silica Gel

4-Amino-3-hydroxy-2-(2-chlorobenzene)-azo-1-naphthalene sulfonic acid (AHCANSA) was used as a chelating modifier to improve the reactivity of the silica gel surface in terms of selective binding and extraction of heavy metal ions. The surface coverage values were found to be 0.488 and 0.473mmolg^–1 for the newly modified physically adsorbed silica gel phase (I) and chemically immobilized-AHCANSA phase (II), respectively. The modified silica gel phases (I, II) were tested for stability in different acidic buffer solutions (pH 1–6) and found to be highly resistant to hydrolysis and leaching by buffer solutions above pH 2. The application of these two phases as solid extractors for a series of mono-, di-, and tri-valent metal ions from aqueous solutions was also performed with different controlling factors such as the pH value of metal ion solutions and equilibrium shaking time. The mmolg^–1 metal capacity values determined by silica gel phases (I, II) were found to confirm high affinity and selectivity characters for binding with heavy metal ions such as Cr³⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ in a range of 0.250–0.483. The tested alkali and alkaline earth metals, Na⁺, K⁺, Mg²⁺ and Ca²⁺, were found to exhibit little interaction and binding ability with the modified silica gel phases. The selectivity characters incorporated into the modified silica gel phases were further utilized and applied in solid phase extraction and pre-concentration of trace concentration levels (1.0µgmL^–1 and 2.00–2.50ngmL^–1) from real seawater samples. The percentage recovery values determined for Cr³⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were found to be in the range of 95.2–98.1±2.0–5.0%, and the pre-concentration recovery values for the same tested heavy metal ions were found to be in the range of 92.5–97.1±3.0–6.0% for the two newly modified silica gel phases with a pre-concentration factor of 500.Received December 20, 2002; accepted May 14, 2003 published online September 1, 2003     

Solid phase extractors derived by functionalising sub-micro silica gel with chelating agents and their pH-tunable adsorbing capability towards Pb(II) and Ag(I)

Three novel solid phase extraction agents were developed by functionalising sub-micron sized silica gel with organic functional moieties possessing {SN}-ligating atoms. The extractors were characterised by FTIR and TGA. Their capability of adsorbing the ions Fe(III), Cu(II), Zn(II), Cd(II), Cr(VI), Hg(II), Pb(II), Co(II), Ni(II), and Ag(I) is described. The extractors show pH-tunable selectivity for Ag(I) and/or Pb(II). By adjusting the pH to 5 or 6, high affinity is found for both Ag(I) and Pb(II), with little or no interference by the other metal ions. At pH values of <2, the extractors become highly selective for Ag(I), with an adsorption capacity of 35 mg g^?1. Little mechanical stirring is required due to the size of the particles. The recovery rates for both Ag(I) and Pb(II) were better 90% even after five repetitive adsorption-desorption cycles.     

Solid-phase extraction for the decontamination of alkali metal, alkaline Earth metal, and ammonium salts from heavy metal ions

Salicylaldoxime-immobilized silica gel was characterized and used as a potential sorbent for heavy metal ions, viz. Cu(II), Ni(II), Co(II), and Zn(II). The experimental conditions were optimized both in batch and column processes to achieve the maximum efficiency. Kinetic and thermodynamic parameters as well as isotherm constants were evaluated to test the feasibility of the process. The role of various metal ions and different anions were tested in order to monitor the process in case of real samples. The alkali metal, alkaline earth metal, and ammonium salts do not have any effect on the said process. This differential behavior can be effectively used for the decontamination of alkali metal, alkaline earth metal, and ammonium salts from Cu(II), Ni(II), Co(II), and Zn(II) ions via solid phase extraction following AAS measurement. The purification of the salts was confirmed by voltammetric experiment.     

Preparation of sinapinaldehyde modified mesoporous silica materials and their application in selective extraction of trace Pb(II)

A new solid phase extractant, sinapinaldehyde (SA) modified SBA-15 mesoporous silica, was developed for selective extraction and preconcentration of trace Pb(II) from aqueous solutions. The successful immobilization of SA on SBA-15 and the strong interaction between SA-SBA-15 and Pb(II) were characterized and confirmed by FTIR spectroscopy and scanning electron microscopy. Parameters such as solution pH, shaking time, eluent condition and sample volume were optimized so that the maximum removal of Pb(II) from solution could be achieved. At pH 4.0, the maximum adsorption capacity of the sorbent for Pb(II) was found to be 33.6?mg?g^?1 and the adsorbed Pb(II) could be completely eluted using a mixed solution of 2?M HCl and 5% CS(NH₂)₂. Some common metal ions such as K(I), Na(I), Mg(II), Ca(II), Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) did not interfere with the adsorption of trace Pb(II). The detection limit of the present method was found to be 1.3?ng?mL^?1 and the relative standard deviation was less than 2.0% (n?=?8). These results suggested that this new sorbent is very efficient and selective for the removal of trace Pb(II) in water samples.     

Extraction of metal ions using chemically modified silica gel: a PIXE analysis

Organic ligand with carboxyhydrazide functional group was immobilised on the surface of silica gel and the metal binding capacity of the ligand-embedded silica was investigated. The functional group was covalently bonded to the silica matrix through a spacer of methylene groups by sequential reactions of silica gel with dibromobutane, malonic ester and hydrazine in different media. Surface area value of the modified silica was determined. The changes in surface area were correlated with the structural change of the silica surface due to chemical modifications. A mixture solution of metal ions [K(I),Cr(III),Co(II),Ni(II),Cu(II),Zn(II),Hg(II) and U(VI)] was treated with the ligand-embedded silica in 10(-3) M aqueous solution. The measurement of metal extraction capacity of the silica based ligand was done by multielemental analysis of the metal complexes thus formed by using Proton Induced X-ray Emission (PIXE) technique.     

Dynamic Adsorption and Desorption Behaviors of Cu(II), Ag(I), and Au(III) on Silica Gel Microspheres Encapsulated by Salicylic Acid–Functionalized Polystyrene

Composite material silica gel microspheres encapsulated by salicylic acid functionalized polystyrene(SG–PS–azo–SA) have been synthesized, and the dynamic adsorption and desorption properties of this silica gel matrix inorganic–organic composite material for Cu(II), Ag(I), and Au(III) have been investigated. The results displayed that SG–PS–azo–SA had excellent adsorption for Cu(II), and the film diffusion dominated the adsorption process of SG–PS–azo–SA for Cu(II), Ag(I), and Au(III). These metal ions could be desorbed with the eluent solution of 2.5 mol/L HCl, 3% thiourea in 0.5 mol/L HCl, and 0.5% thiourea in 1 mol/L HCl, respectively. When the elution was carried out for 30 min, 30 min, and 132 min, the desorption ratio ω could reach 91.1%, 99.4%, and 60.84%, respectively. Thus, silica gel encapsulated by polystyrene coupled with salicylic acid (SG–PS–azo–SA) is favorable and useful for the removal of metal ions Cu(II), Ag(I), and Au(III), and the high adsorption capacity make it a promising candidate material for the metal ions removal.     

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., DeltaG, DeltaS, and DeltaH, were also calculated for the system. From these parameters, DeltaH 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. DeltaS values were calculated to be positive for the sorption of the same sequence of divalent cations onto sorbent. Negative DeltaG values indicated that the sorption process for these three metal ions onto immobilized silica gel is spontaneous.     

Synthesis and characterization of silica gel microspheres encapsulated by salicyclic acid functionalized polystyrene and its adsorption of transition metal ions from aqueous solutions

The present study was undertaken to develop a novel adsorbent for heavy metal ions, and this paper presents the synthesis and characterization of a composite material-silica gel microspheres encapsulated by salicyclic acid functionalized polystyrene (SG-PS-azo-SA) with a core-shell structure. SG-PS-azo-SA was used to investigate the adsorption of Mn(II), Co(II), Ni(II), Fe(III), Hg(II), Zn(II), Cd(II), Cr(VI), Pd(II), Cu(II), Ag(I), and Au(III) from aqueous solutions. The results revealed that SG-PS-azo-SA has better adsorption capacity for Cu(II), Ag(I) and Au(III). Langmuir and Freundlich isotherm models were applied to analyze the experimental data, the best interpretation for the experimental data was given by the Langmuir isotherm equation with the maximum adsorption capacity for Cu(II), Ag(I), and Au(III) at 1.288 mmol g⁻¹, 1.850 mmol g⁻¹ and 1.613 mmol g^t-1, respectively. Thus, silica gel encapsulated by salicyclic acid functionalized polystyrene (SG-PS-azo-SA) is favorable and useful for the removal of Cu(II), Ag(I) and Au(III) metal ions.