Synthesis and application of p-tert-butylcalix[8]arene immobilized material for the removal of azo dyes

The present study describes synthesis of a new resin through immobilization of p-tert-butylcalix[8]arene onto silica and its application for the removal of azo dyes from aqueous media as well as from textile effluents. The newly synthesized material 4 is characterized by FT-IR spectroscopy, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). Reactive Black-5 (RB-5) and Reactive Red-45 (RR-45) azo dyes were used as sorbate. Batch wise sorption experiments were conducted to optimize various experimental parameters such as the effect of sorbent dosage, electrolyte, pH, dye concentration, and contact time. The optimized pH for the effective removal of RB-5 and RR-45 dyes was 9 and 3, respectively. The increase in material 4 dosage increased the percent sorption. Both Langmuir and Freundlich isotherm models were applied to experimental data and Langmuir isotherm model found to be best fit. The results revealed that material 4 was potentially more effective sorbent for the sorption of selected azo dyes as compared to pure silica and p-tert-butylcalix[8]arene. The field studies also supported the effectiveness of material 4, which could be useful for the removal of both the dyes and also for the normalization of pH, TDS, conductivity and salinity near to the drinking water.     

Removal of chromium and toxic ions present in mine drainage by Ectodermis of Opuntia

This work presents conditions for hexavalent and trivalent chromium removal from aqueous solutions using natural, protonated and thermally treated Ectodermis of Opuntia. A removal of 77% of Cr(VI) and 99% of Cr(III) can be achieved. The sorbent material is characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, infrared spectroscopy, thermogravimetric analysis, before and after the contact with the chromium containing aqueous media. The results obtained from the characterization techniques indicate that the metal ion remains on the surface of the sorbent material. The percentage removal is found to depend on the initial chromium concentration and pH. The Cr(VI) and Cr(III) uptake process is maximum at pH 4, using 0.1g of sorbent per liter of aqueous solution. The natural Ectodermis of Opuntia showed a chromium adsorption capacity that was adequately described by the Langmuir adsorption isotherm. Finally, an actual mine drainage sample that contained Cd, Cr, Cu, Fe Zn, Ni and Pb was tested under optimal conditions for chromium removal and Ectodermis of Opuntia was found to be a suitable sorbent material. The use of this waste material for the treatment of metal-containing aqueous solutions as well as mine drainage is effective and economical.     

Adsorption and recognizing ability of molecular imprinted polymer MIP-PEI/SiO(2) towards phenol

Firstly, functional macromolecule polyethyleneimine (PEI) was grafted onto the surfaces of silica gel particles via the coupling grafting method, the adsorption material PEI/SiO(2) was formed. Secondly, the molecular imprinting was carried out towards the macromolecule PEI grafted on the surface of silica particles using phenol as a template and diepoxyalkyl (669) as a crosslinking agent. Finally, imprinted polymer MIP-PEI/SiO(2) with high affinity, specific recognition ability and excellent selectivity for phenol was prepared. The adsorption and recognition ability of MIP-PEI/SiO(2) for phenol were researched by static methods. The experimental results show that MIP-PEI/SiO(2) possesses very strong adsorption and recognition ability for phenol. The saturated adsorption capacity could reach to 46.6 mg g(-1). The selectivity coefficients relative to resorcin and p-nitrophenol are 35.41 and 37.40, respectively. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. pH and temperature have great influence on the adsorption capacity. Diluted hydrochloric acid solution is used as eluent, and the adsorbed phenol is eluted easily from MIP-PEI/SiO(2).     

Adsorption of Cr(VI) using silica-based adsorbent prepared by radiation-induced grafting

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved that DMAEMA was grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr(VI) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr(VI) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(VI) uptake (ca. 68 mg/g) as the pH was in the range of 2.5–5.0. Furthermore, even in strong acidic (4.0 mol/L HNO₃) or alkaline media (pH 11.0), the adsorbent had a sound Cr(VI) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(VI)) from waste waters.     

Synthesis of surface imprinted nanospheres for selective removal of uranium from simulants of Sambhar salt lake and ground water

Imprinted polymer nanospheres for uranium were prepared by complexing uranyl ion on to quinoline-8-ol functionalized 3-aminopropyltrimethoxysilane modified silica nanoparticles followed by surface imprinting with 4-VP (4-vinyl pyridine), HEMA (2-hydroxy ethyl methacrylate) and EGDMA (ethylene glycol dimethacrylate) as the functional monomers and cross linking agent respectively with AIBN (2,2'-azo-bis-isobutyronitrile) as initiator and 2-methoxyethanol as the porogen. Non-imprinted polymer material was also prepared under similar conditions omitting uranyl ion. The above materials were used for solid phase extraction of uranium. Recent realization that its chemical toxicity is dominant than radiation hazards makes decontamination a relevant topic for environmental point of view, particularly in the light of projected global thrust for uranium fuel based atomic power plants. The material offers high retention capacity of 97.1 μmol g(-1) for 10 mg L(-1) of uranium that does not require tedious grinding and sieving steps, is water compatible and works in the pH range of 5-7, making it ideal for possible use in decontamination of polluted natural water samples or front end effluents of nuclear power reactors.     

Chelating adsorption properties of PEI/SiO(2) for plumbum ion

In this paper, a novel adsorption material PEI/SiO(2) with strong adsorption ability towards heavy-metal ions was prepared. In preparation of PEI/SiO(2), functional macromolecule polyethyleneimine (PEI) was grafted onto the surfaces of silica gel particles via the coupling effect of gamma-chloropropyl trimethoxysilane (CP). The adsorption properties of PEI/SiO(2) for Pb(2+) ion were studied by both static and dynamic methods. The experimental results show that PEI/SiO(2) possesses very strong adsorption ability for Pb(2+) ion, the saturated adsorption amount could reach to 17.5mgg(-1), and the empirical Langmuir isotherm was found to describe well the equilibrium adsorption data. The pH and grafting amount of PEI have great influence on the adsorption amount. The Pb(2+) ions adsorbed on PEI/SiO(2) are eluted easily by diluted hydrochloric acid solution.     

New polymer-supported ion-complexing agents: design, preparation and metal ion affinities of immobilized ligands

Polymer-supported reagents are comprised of crosslinked polymer networks that have been modified with ligands capable of selective metal ion complexation. Applications of these polymers are in environmental remediation, ion chromatography, sensor technology, and hydrometallurgy. Bifunctional polymers with diphosphonate/sulfonate ligands have a high selectivity for actinide ions. The distribution coefficient for the uranyl ion from 1 M nitric acid is 70,000, compared to 900 for the monophosphonate/sulfonate polymer and 200 for the sulfonic acid ion-exchange resin. A bifunctional trihexyl/triethylammonium polymer has a high affinity and selectivity for pertechnetate and perchlorate anions from groundwater. In one example, its distribution coefficient for perchlorate ions in the presence of competing anions is 3,300,000, compared to 203,180 for a commercially available anion-exchange resin. Polystyrene modified with N-methyl-D-glucamine ligands is capable of selectively complexing arsenate from groundwater. It complexes 99% of the arsenate present in a solution of 100 mg/L arsenate with 560 mg/L sulfate ions. Its selectivity is retained even in the presence of 400 mg/L phosphate. There is no affinity for arsenate above pH 9, allowing for the polymer to be regenerated with moderate alkali solution. In studies aimed at developing a Hg(II)-selective resin, simple amine resins were found to have a high Hg(II) affinity and that affinity is dependent upon the solution pH and the counterion.     

Sorption of Cd(II) and Se(IV) from aqueous solution using modified rice husk

A carbonaceous sorbent was prepared from rice husk via sulfuric acid treatment. Removal of Cd(II) and Se(IV) from aqueous solution was studied varying time, pH, metal concentration, temperature and sorbent status (wet and dry). Cd(II) sorption was found fast reaching equilibrium within approximately 2 h while Se(IV) sorption was slow reaching equilibrium within approximately 200 h with better performance for the wet sorbent than for the dry. Kinetics data for both metals were found to follow pseudo-second order model. Cd(II) sorption was low at low pH values and increased with pH increase, however, Se(IV) sorption was high at low pH values, and decreased with the rise in initial pH until pH 7. A fall in the final pH was noticed with Cd(II) sorption due to the release of protons indicating an ion exchange mechanism. However, for Se(IV) sorption, a rise in the final pH was observed due to protons consumption in the process. For both metals, sorption fit well the Langmuir equation with higher uptake by rising the temperature. Analysis by scanning electron microscope and X-ray powder diffraction for the sorbent after the reaction with acidified Se(IV) confirmed the availability of elemental selenium, Se(0), as particles on the sorbent surface. The reduction process of acidified Se(IV) to Se(0) is accompanied by surface oxidation. Physicochemical tests showed an increase in sorbent acidity, cation exchange capacity and surface functionality after the reaction with acidified Se(IV) indicating that oxidation processes took place on the sorbent surface. On the other hand, no changes in physicochemical tests were found after Cd(II) sorption indicating the absence of redox processes between Cd(II) and the sorbent.     

Separation, preconcentration and determination of silver ion from water samples using silica gel modified with 2,4,6-trimorpholino-1,3,5-triazin

A new modified silica gel using 2,4,6-trimorpholino-1,3,5-triazin was used for separation, preconcentration and determination of silver ion in natural water by atomic absorption spectrometry (AAS). This new bonded silica gel was used as an effective sorbent for the solid-phase extraction (SPE) of silver ion from aqueous solutions. Experimental conditions for effective adsorption of trace levels of silver ion were optimized with respect to different experimental parameters in column process. Common coexisting ions did not interfere with the separation and determination of silver at pH 3.5 so that silver ion completely adsorbed on the column. The preconcentration factor is 130 (1 mL elution volume for a 130 mL sample volume). The relative standard deviation (R.S.D.) under optimum conditions is 3.03% (n=5). The accuracy of the method was estimated by using spring and tap water samples that were spiked with different amounts of silver ion. The adsorption isotherm of silver ion was obtained. The capacity of the sorbent at optimum conditions has been found to be 384 microg of silver per gram of sorbent.     

镉离子印迹硅胶的制备与吸附性能

采用表面印迹技术和溶胶-凝胶法,以Cd(Ⅱ)离子作为印迹离子,硫氰基丙基三甲氧基硅烷为功能分子,环氧氯丙烷为交联剂,在硅胶表面制备Cd(Ⅱ)离子印迹聚合物(IIP-TCPTS/SiO2),并利用平衡吸附法研究了聚合物吸附性能和选择识别能力。结果表明,最大吸附量为16.7 mg/g;20 min即可达到吸附平衡;当pH值在5.4~7.8范围内,印迹聚合物保持了较好的吸附容量;印迹聚合物对Cd(Ⅱ)离子具有较强的选择性识别能力;重复使用时性能稳定。     

表面引发聚合反应制备色谱固定相

巯丙基硅烷在硅胶表面组装形成潜在的自由基链转移点,向表面的自由基链转移及表面引发聚合反应可在硅胶表面形成化学键合的聚合物膜,反应过程用红外光谱(FT-IR)、X射线光电子能谱(XPS)、拉曼光谱(Raman)及热重分析(TGA)进行表征。随着巯丙基硅烷修饰硅胶用量的增加,溶液中形成的自由聚合物的分子量及聚合物在硅胶表面的接枝量减小,单体的接枝量随着聚合时间的逐渐增大,直至平衡值。用此方法得到的聚甲基丙烯酸甲酯修饰的硅胶呈现良好的反相色谱性能,对几种含氧芳烃衍生物的保留时间按下列顺序增加:对羟基苯甲酸<α-萘乙酸<β-苯乙醇<苯酚<对羟基苯甲酸甲酯<苯甲酸甲酯<苯甲酸乙酯<苯甲酸丁酯。     

Synthesis and characterization of nano-pore thallium (III) ion-imprinted polymer as a new sorbent for separation and preconcentration of thallium

Thallium (III) ion-imprinted polymer (IIP) particles were synthesized by preparing the ternary complex of thallium (III) ions with 5,7-dichloroquinoline-8-ol (DCQ) and 4-vinylpyridine (VP). Thermal copolymerization with methyl methacrylate (functional monomer, MMA) and ethyleneglycoldimethacrylate (cross-linking monomer, EGDMA) was then performed in the presence of acetonitrile (porogen) and 2,2- azobisisobutyronitrile(initiator, AIBN). The imprinted ion was removed from polymer by stirring of the above particles with 5M HNO(3) to obtain the leached IIP particles. Moreover, control polymer (CP) particles were similarly prepared without the thallium (III) ions. The unleached and leached IIP particles were characterized by surface area analysis (BET), X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM). The preconcentration of thallium (III) from aqueous solution was studied during rebinding with the leached IIP particles as a function of pH, the weight of the polymer material, the uptake and desorption times, the aqueous phase and the desorption volumes. Electrothermal atomic absorption spectrometry (ETAAS) was employed for determination of thallium in aqueous solution. The limit of detection for the method was 0.02 ng mL(-1), while the relative standard deviation for five replicates was 2.6%.     

Kinetic and equilibrium study for the sorption of cadmium(II) ions from aqueous phase by eucalyptus bark

The efficiency of eucalyptus bark as a low cost sorbent for removing cadmium ions from aqueous solution has been investigated in batch mode. The equilibrium data could be well described by the Langmuir isotherm but a worse fit was obtained by the Freundlich model. The five linearized forms of the Langmuir equation as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Maximum cadmium uptake obtained at a temperature of 20 degrees C was 14.53mgg(-1). The influence of temperature on the sorption isotherms of cadmium has been also studied. The monolayer sorption capacity increased from 14.53 to 16.47 when the temperature was raised from 20 to 50 degrees C. The DeltaG degrees values were negative, which indicates that the sorption was spontaneous in nature. The effect of experimental parameters such as contact time, cadmium initial concentration, sorbent dose, temperature, solution initial pH, agitation speed, and ionic strength on the sorption kinetics of cadmium was investigated. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The pseudo-second-order model parameters were function of the initial concentration, the sorbent dose, the solution pH, the agitation speed, the temperature, and the ionic strength.     

Sorption characteristics of Cu(II) ions onto silica gel-immobilized calix[4]arene polymer in aqueous solutions: batch and column studies

In the present study, Cu(II) removal from aqueous solutions by sorption was investigated. Aminopropyl silica gel-immobilized calix[4]arene polymer (APSIC[4]P) was used in sorption as sorbent. During the experimental part of this study, the effect of parameters, such as pH, initial Cu(II) concentration, temperature on Cu(II) removal was observed. In addition, sorption isotherm studies and column studies were made. Maximum Cu(II) removal was obtained at pH 6 and 25 degrees C. In the isotherm studies, Langmuir and Freundlich isotherm models were applied and it was determined that the experimental data confirmed to Langmuir isotherm model. Batch sorption capacity (q0) was calculated as 5.08 mg/g. The capacity value for column study was obtained by graphical integration as 1.14 mg/g. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristics parameters of the column useful for process design.     

高pH值的硝酸铀酰溶液中碳钢腐蚀与沉积膜的特性

用均匀腐蚀法和电化学法研究了碳钢(A3)在pH值5.0的硝酸铀酰溶液中的腐蚀行为。均匀腐蚀试验结果表明，碳钢在PH值5．0硝酸铀酰溶液中发生非电化学腐蚀，使溶液酸度降低，导致铀酰离子水解，在碳钢表面形成了水合氧化铀沉积膜。动电位阳极极化试验结果显示，碳钢的腐蚀电位随扫描电位速率的增加向阴极方向移动，UO2^2 的沉积对碳钢的阴极反应有抑制作用。均匀腐蚀后的样品，经XRD、XPS分析证实，沉积膜主要为铀酰离子的氧化物沉淀。     

New polyamide-containing sorbents for one-step isolation of DNA

A composite sorbent modified with fluorinated aromatic polyamide, for single-step isolation of DNA from biological mixtures is developed. The sorbent is prepared by the polymer deposition from solution onto the surface of porous silica. It is shown that the polymer coating with a thickness of 4 nm is formed not only on the outer surface of the carrier particles but also on the inner pore surfaces. It is found that the material produced largely retained porosity of the pristine support and the material is selective in a one-step separation of nucleic acids and proteins by passing the bacterial lysate through a sorbent. The degree of purification of the isolated preparations of DNA is sufficient to be used directly in PCR analysis.     

Adsorption of phenol on a novel adsorption material PEI/SiO2

In this paper, functional macromolecule polyethyleneimine (PEI) was grafted onto the surfaces of silica gel particles via the coupling effect of gamma-chloropropyl trimethoxysilane (CP), and the novel adsorption material PEI/SiO2 with strong adsorption ability for phenol was prepared. The adsorption properties of PEI/SiO2 for phenol were researched by both static and dynamic methods. The experimental results show that PEI/SiO2 possesses very strong adsorption ability for phenol, and the saturated adsorption amount could reach to 160 mg g(-1). The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. pH and grafting amount of PEI have great influence on the adsorption amount. Diluted sodium hydroxide solution is used as eluent, and the adsorbed phenol is eluted easily from PEI/SiO2.     

Adsorption characteristics of trivalent chromium on palm oil fuel ash

The metal uptake characteristics of ash particles obtained from the combustion of oil palm solid waste (referred to as palm oil fuel ash) are evaluated using trivalent chromium as a model adsorbate. The equilibrium and kinetic properties of Cr(III) are studied in batch stirred-tank experiments. The extent of Cr(III) removal increases with an increase in solution pH. The maximum equilibrium uptake capacity at pH 6 is 0.31 mmol/g of sorbent. A Langmuir isotherm model with pH-dependent parameters accounts very well for the measured equilibrium data. Modeling studies using a second order irreversible reaction model and a pseudo-first order kinetic model indicate that transient profiles obtained experimentally for a range of initial metal concentrations and sorbent dosages are in good agreement with calculated curves of both models. The two kinetic models can be employed for a useful summary of the experimental data so long as their rate coefficients are empirically correlated with the two system variables: initial metal concentration and sorbent dosage. Electronic Publication     

Biosorption of nickel from protonated rice bran

In the present study biosorption technique, the accumulation of metals by biomass was used for the removal of nickel from aqueous medium. The rice bran in its acid treated (H(3)PO(4)) form was used as a low cost sorbent. The adsorption characteristics of nickel on protonated rice bran were evaluated as a function of pH, biosorbent size, biosorbent dosage, initial concentration of nickel and time. Within the tested pH range (pH 1-7), the protonated rice bran displayed more resistance to pH variation, retaining up to 102 mg/g of the nickel binding capacity at pH 6. Meanwhile, at lower pH values the uptake capacity decreased. The % age removal of nickel was maximum at 0.25 g of biosorbent dose and 0.25 mm biosorbent size. At the optimal conditions, metal ion uptake was increased as the initial metal ion concentration increased up to 100mg/L. Kinetic and isotherm experiments were carried out at the optimal pH 6.0 for nickel. The metal removal rate was rapid, with 57% of the total adsorption taking place within 15-30 min. The Freundlich and Langmuir models were used to describe the uptake of nickel on protonated rice bran. The Langmuir and Freundlich model parameters were evaluated. The equilibrium adsorption data was better fitted to Langmuir adsorption isotherm model. The adsorption followed pseudo second-order kinetic model. The thermodynamic assessment of the metal ion-rice bran biomass system indicated the feasibility and spontaneous nature of the process and DeltaG degrees values were evaluated as ranging from -22.82 to -24.04 kJ/mol for nickel sorption. The order of magnitude of the DeltaG degrees values indicated an ion-exchange physiochemical sorption process.     

Acid-base equilibria inside amine-functionalized mesoporous silica

Acid-base equilibria and effective proton concentration inside a silica mesopore modified with a trimethyl ammonium (TMAP) layer were studied by steady-state fluorescence experiments. The mesoporous silica with a dense TMAP layer (1.4 molecules/nm(2)) was prepared by a post grafting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium at surfactant-templated mesoporous silica (diameter of silica framework =3.1 nm). The resulting TMAP-modified mesoporous silica strongly adsorbed of anionic fluorescence indicator dyes (8-hydroxypyrene-1,3,6-trisulfonate (pyranine), 8-aminopyrene-1,3,6-trisulfonate (APTS), 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid disulfuric acid (TPPS), 2-naphthol-3,6-disulfonate (2NT)) and fluorescence excitation spectra of these dyes within TMAP-modified mesoporous silica were measured by varying the solution pH. The fluorescence experiments revealed that the acid-base equilibrium reactions of all pH indicator dyes within the TMAP-modified silica mesopore were quite different from those in bulk water. From the analysis of the acid-base equilibrium of pyranine, the following relationships between solution pH (pH(bulk)) and the effective proton concentration inside the pore (pH(pore)) were obtained: (1) shift of pH(pore) was 1.8 (ΔpH(pore)=1.8) for the pH(bulk) change from 2.1 to 9.1 (ΔpH(bulk)=7.0); (2) pH(pore) was not simply proportional to pH(bulk); (3) the inside of the TMAP-modified silica mesopore was suggested to be in a weak acidic or neutral condition when pH(bulk) was changed from 2.0 to 9.1. Since these relationships between pH(bulk) and pH(pore) could explain the acid-base equilibria of other pH indicator dyes (APTS, TPPS, 2NT), these relationships were inferred to describe the effective proton concentration inside the TMAP-modified silica mesopore.