Large Volumes Of Aqueous Solutions Research Articles

Pb(II) sorption on molecular sieve analogues of MCM-41 synthesized from kaolinite and montmorillonite

Mesoporous molecular sieves were prepared with montmorillonite and kaolinite as silica sources, respectively, (denoted as P-M and P-K) by a hydrothermal method. The two prepared materials were characterized by XRD, FTIR and N2 adsorption–desorption. The results indicated that both P-M and P-K are typical mesoporous molecular sieves with high specific surface areas. Sorption of Pb(II) from aqueous solution to P-M and P-K was studied by using a batch technique. The effect of contact time, pH and temperature on the sorption of Pb(II) to P-M and P-K was investigated. A simplified surface complexation model was used to simulate the complexation of Pb(II) ions onto molecular sieves. The results suggested that sorption of Pb(II) was strongly dependent on pH values. Kinetics of sorption showed that the pseudo-second-order kinetic model held for the sorption process. Equilibrium modeling showed that the sorption of Pb(II) was fitted well by the Langmuir isotherm model. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated from the sorption of Pb(II) at three different temperatures of 283K, 303K and 333K. The sorption reaction was endothermic and the process was favored at high temperature. The results indicated that both P-M and P-K are suitable materials for removal of Pb(II) from large volumes of aqueous solutions.

Polyaniline Multiwalled Carbon Nanotube Magnetic Composite Prepared by Plasma-Induced Graft Technique and Its Application for Removal of Aniline and Phenol

Aniline molecules were grafted onto multiwalled carbon nanotubes (MWCNTs) by using a plasma-induced grafting technique. The polyaniline (PANI) grafted MWCNTs (PANI/MWCNTs) were characterized by using ultraviolet−visible spectrophotometry, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis−differential thermal analysis, and field-emission scanning electron microscopy. The results indicated that the magnetic composite consisting of PANI/MWCNTs was synthesized. The application of PANI/MWCNTs for the removal of aniline and phenol from aqueous solutions was investigated under ambient conditions. The grafted PANI on MWCNTs contributed to the enhancement of the adsorption capacity because of the strong conjugate effect between PANI and organic pollutants. PANI/MWCNTs can be separated and recovered from aqueous solution by magnetic separation. The results show that PANI/MWCNTs are a promising magnetic material for the preconcentration and separation of organic pollutants from large volumes of aqueous solutions in environmental pollution cleanup.

Effect of environmental conditions on the sorption of radiocobalt from aqueous solution to treated eggshell as biosorbent

Carbonate hydroxylapatite (CHAP), prepared from eggshell waste, was used to remove 60Co(II) from aqueous solutions. The sorption of 60Co(II) on CHAP as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of humic acid and fulvic acid under ambient conditions was studied. The sorption of 60Co(II) on CHAP was strongly dependent on pH and ionic strength. The thermodynamic parameters (ΔH 0, ΔS 0, ΔG 0) of 60Co(II) sorption on CHAP were calculated from the temperature-dependent sorption isotherms, and the results indicated that the sorption process of 60Co(II) on CHAP was endothermic and spontaneous. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on CHAP surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. Experimental results also indicated that CHAP was a suitable low-cost adsorbent for pre-concentration and solidification of 60Co(II) from large volumes of aqueous solutions.

Plasma Induced Grafting Multiwalled Carbon Nanotube with Chitosan and Its Application for Removal of UO, Cu2+, and Pb2+ from Aqueous Solutions

AbstractMultiwalled carbon nanotubes (MWCNTs) have attracted multidisciplinary interest because of their special physicochemical properties. Herein, chitosan (CS) was grafted onto the surfaces of MWCNTs by using plasma technique. The CS grafted MWCNTs (MWCNT‐g‐CS) were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, powder X‐ray diffraction (XRD), UV–Vis spectrophotometry, scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS) in detail. The prepared MWCNT‐g‐CS were used to remove ${\rm UO}_{{\rm 2}}^{{\rm 2 + }} $, Cu2+, and Pb2+ ions from large volumes of aqueous solutions under ambient conditions, and the results showed that MWCNT‐g‐CS has much higher adsorption capacity than MWCNTs in the removal of heavy metal ions. MWCNT‐g‐CS are suitable materials in the preconcentration and solidification of heavy metal ions from large volumes of aqueous solutions. magnified image

Adsorption and desorption of radionuclide europium(III) on multiwalled carbon nanotubes studied by batch techniques

The adsorption of Eu(III) on multiwalled carbon nanotubes (MWCNTs) as a function of pH, ionic strength and solid contents are studied by batch technique. The results indicate that the adsorption of Eu(III) on MWCNTs is strongly dependent on pH values, dependent on ionic strength at low pH values and independent of ionic strength at high pH values. Strong surface complexation and ion exchange contribute to the adsorption of Eu(III) on MWCNTs at low pH values, whereas surface complexation and surface precipitation are the main adsorption mechanism of Eu(III) on MWCNTs. The desorption of adsorbed Eu(III) from MWCNTs by adding HCl is also studied and the recycling use of MWCNTs in the removal of Eu(III) is investigated after the desorption of Eu(III) at low pH values. The results indicate that adsorbed Eu(III) can be easily desorbed from MWCNTs at low pH values, and MWCNTs can be repeatedly used to remove Eu(III) from aqueous solutions. MWCNTs are suitable material in the preconcentration and solidification of radionuclides from large volumes of aqueous solutions in nuclear waste management.

Plasma induced grafting multiwall carbon nanotubes with chitosan for 4,4′-dichlorobiphenyl removal from aqueous solution

Multiwall carbon nanotubes (MWCNTs) have attracted multidisciplinary interest because of their special physicochemical properties. Herein, plasma technique was applied to graft chitosan (CS) on MWCNTs to improve their dispersion property and sorption ability for polychlorinated biphenyls. The CS grafted oxidized MWCNTs (MWCNT- g-CS) was analyzed by using Fourier Transform Infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), UV–vis spectrophotometry, thermogravimetric analysis (TGA)–differential thermal analysis (DTA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the results indicated that CS was successfully grafted on the surfaces of MWCNTs. The prepared MWCNT- g-CS was applied to remove 4,4′-dichlorobiphenyl (4,4′-DCB) from aqueous solution under ambient conditions. The results showed that MWCNT- g-CS was a suitable material in the preconcentration and immobilization of 4,4′-DCB from large volumes of aqueous solutions in polychlorinated biphenyl pollution cleaning.

SDBS Modified XC‐72 Carbon for the Removal of Pb(II) from Aqueous Solutions

AbstractSodium dodecylbenzene sulfonate (SDBS) is grafted on Vulcan XC‐72 carbon (XC‐72 carbon) using a plasma technique. The SDBS grafted XC‐72 carbon (XC‐SDBS) is characterized using XPS, UV‐Vis spectrophotometry, XRD, TGA‐DTA, SEM, and potentiometric acid‐base titration, respectively. The application of XC‐SDBS and XC‐72 carbon for the removal of Pb(II) ions from large volumes of aqueous solution is investigated. The results indicate that XC‐SDBS has much higher adsorption capacity than that of XC‐72 carbon. XC‐SDBS is a suitable material for the immobilization of heavy metal from large volumes of aqueous solutions in environmental pollution cleaning.magnified image

Removal of polychlorinated biphenyls from aqueous solutions using β-cyclodextrin grafted multiwalled carbon nanotubes

Cyclodextrins have excellent ability in the preconcentration of organic pollutants from aqueous solutions by forming inclusion complexes. Multiwalled carbon nanotubes (MWCNTs) possess high adsorption capacity in the removal of organic pollutants through the formation of conjugated complexes. In this paper, β-cyclodextrin (β-CD) was grafted on the surfaces of MWCNTs by using plasma technique. The β-CD grafted MWCNTs (MWCNT- g-CD) were characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermo gravimetric analysis-differential thermal analysis, and scanning electron microscopy in detail. The prepared MWCNT- g-CD were used to remove polychlorinated biphenyls (PCBs) from aqueous solutions under ambient conditions. The results suggest that MWCNT- g-CD have much higher adsorption capacity than MWCNTs in the removal of PCBs from aqueous solutions. MWCNT- g-CD are suitable materials in the preconcentration and immobilization of PCBs from large volumes of aqueous solutions in environmental pollution cleanup.

Preconcentration of Pb 2+ from aqueous solution using poly(acrylamide) and poly(N,N-dimethylacrylamide) grafted multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) were grafted with poly(acrylamide) (PAAM) and with poly(N,N-dimethylacrylamide) (PDMA) at same grafting percentage by using N 2 plasma technique. The PAAM grafted MWCNTs (MWCNT- g-PAAM) and PDMA grafted MWCNTs (MWCNT- g-PDMA) were characterized by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermo gravimetric analysis-differential thermal analysis (TGA–DTA), scanning electron microscopy (SEM), and potentiometric titration. The results indicated that the grafting processes occurred on the surfaces of MWCNTs without destroying the framework of MWCNTs. The application of MWCNTs, MWCNT- g-PAAM, and MWCNT- g-PDMA in the removal of Pb 2+ from aqueous solution was investigated under ambient conditions. The grafted PAAM and PDMA improved MWCNT adsorption capacity in the removal of Pb 2+ from large volumes of aqueous solutions. MWCNT- g-PAAM had much higher adsorption capacity than MWCNT- g-PDMA, which was attributed to higher amide group content in acrylamide than that in N,N-dimethylacrylamide.

Kinetics and thermodynamics of adsorption of ionizable aromatic compounds from aqueous solutions by as-prepared and oxidized multiwalled carbon nanotubes

The adsorption of 1-naphthylamine, 1-naphthol and phenol on as-prepared and oxidized multiwalled carbon nanotubes (MWCNTs) has been investigated. The results illustrated that both as-prepared and oxidized MWCNTs showed high adsorption capacity for the three ionizable aromatic compounds (IACs) studied. Oxidation of MWCNTs increased the surface area and the pore volume, and introduced oxygen-containing functional groups to the surfaces of MWCNTs, which depressed the adsorption of IACs on MWCNTs. Both Langmuir and Freundlich models described the adsorption isotherms very well and the adsorption thermodynamic parameters (DeltaG degrees, DeltaH degrees and DeltaS degrees) were measured. The adsorption for 1-naphthylamine, 1-naphthol and phenol is general spontaneous and thermodynamically favorable. The adsorption of phenol is an exothermic process, whereas the adsorption of 1-naphthylamine and 1-naphthol is an endothermic process. Results of this work are of great significance for the environmental application of MWCNTs for the removal of IACs from large volume of aqueous solutions.

Ionic Liquids Containing the Tris(pentafluoroethyl)trifluorophosphate Anion: a New Class of Highly Selective and Ultra Hydrophobic Solvents for the Extraction of Polycyclic Aromatic Hydrocarbons Using Single Drop Microextraction

A new class of ionic liquids (ILs) containing the tris(pentafluoroethyl)trifluorophosphate (FAP) anion are paired with imidazolium, phosphonium, and pyrrolidinium cations and used as extraction solvents in direct immersion single drop microextraction (SDME) studies coupled to high performance liquid chromatography (HPLC). The selectivity and sensitivity of the extraction method can be tuned and manipulated by varying the cationic component of the IL, thereby providing larger enrichment factors for a variety of analytes, including polycyclic aromatic hydrocarbons (PAHs). Compared to other hydrophobic ILs containing the hexafluorophosphate (PF(6)(-)) and bis[(trifluoromethyl)sulfonyl]imide (NTf(2)(-)) anions, FAP-based ILs are significantly more hydrophobic and hydrolytically stable permitting them to be used in the sampling of large volumes of aqueous solutions without dissolution or loss of the IL. The highest enrichment factors were obtained with the trihexyl(tetradecyl)phosphonium FAP ([PH(3)T] [FAP]) IL for compounds with high molecular weight and fused rings while high enrichment factors were obtained for smaller, more polar molecules using the 1-hexyl-3-methylimidazolium FAP ([HMIM] [FAP]) IL. The detection limits for nine studied PAHs ranged from 0.1 to 0.6, 0.03 to 0.4, 0.04 to 0.7 and 0.1 to 1.2 microg L(-1) for [HMIM] [FAP], [PH(3)T] [FAP], 1-butyl-1-methylpyrrolidinium FAP ([BMPL] [FAP]), and 1-(6-amino-hexyl)-1-methylpyrrolidinium FAP ([HNH(2)MPL] [FAP]), respectively. The reproducibility of the extraction method at 20 degrees C using the FAP-based ILs was in the range of 1.5-9.4%. Three real water samples including tap water, creek water, and river water were analyzed and yielded recoveries ranging from 79-114%.

Plasma Induced Grafting Carboxymethyl Cellulose on Multiwalled Carbon Nanotubes for the Removal of UO22+ from Aqueous Solution

Carboxymethyl cellulose (CMC) is grafted on multiwalled carbon nanotubes (MWCNT) by using plasma techniques. The CMC grafted MWCNT (MWCNT-g-CMC) is characterized by using Fourier transform infrared spectra (FT-IR), Raman spectra, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA)-differential thermal analysis (DTA), scanning electron microscopy (SEM), and N(2)-BET methods in detail. The application of MWCNT-g-CMC in the removal of UO(2)(2+) from aqueous solution is investigated. MWCNT-g-CMC has much higher sorption ability in the removal of UO(2)(2+) than raw MWCNT. The MWCNT-g-CMC is a suitable material in the preconcentration and solidification of heavy metal ions from large volume of aqueous solutions.

Membrane optode for mercury(II) determination in aqueous samples

A color changeable optode for Hg(II) was prepared by the immobilization of a dye 4-(2-pyridylazo)resorcinol (PAR) and a liquid ion-exchanger trioctylmethylammonium chloride (Aliquat-336) in the tri-(2-ethylhexyl) phosphate plasticized cellulose triacetate matrix. Hg(II) and CH 3Hg + from aqueous samples could be quantitatively preconcentrated in this transparent optode producing a distinct color change ( λ max = 520 nm) within 5 min equilibration time in bicarbonate aqueous medium or 30 min in natural water. Whereas optode sample without Aliquat-336 did not change its color corresponding to Hg–PAR complex on equilibrium with the same aqueous solution containing Hg(II) ions. The uptake of Hg(II) was found to be pH dependant with a maximum (>90%) at a pH 7.5. The uptake of ions like Cu(II), Fe(II), Zn(II) and Pb(II) was negligible in the optode where as the uptake of Cd(II) and Zn(II) ions was 10–15% at pH 7.5. The optode developed in the present work was studied for its analytical application for Hg(II) in the aqueous samples by spectrophotometry, radiotracer ( 203Hg), Energy Dispersive X-ray Fluorescence (EDXRF) analyses and Instrumental Neutron Activation Analysis (INAA). The minimum amount of Hg(II) required to produce detectable response by spectrophotometry, INAA and EDXRF were found to be 5.5, 1 and 12 μg, respectively. This optode showed a linear increase in the absorbance at λ max = 520 nm over a concentration range of 0.22–1.32 μg/mL of Hg(II) ions in aqueous solution for 5 min. The preconcentration of Hg(II) from large volume of aqueous solution was used to extend the lower limit of concentration range that can be quantified by the spectrophotometry of optode. It was observed that preconcentration of 11 μg Hg(II) in 100 mL (0.11 μg/mL) in aqueous samples gives a distinct color change and absorbance above 3 σ of the blank absorbance. The optode developed in the present work was found to be reusable.

Adsorption behavior of multiwall carbon nanotube/iron oxide magnetic composites for Ni(II) and Sr(II)

Multiwall carbon nanotube (MWCNT)/iron oxide magnetic composites were prepared, and were characterized by scan electron microscopy using a field emission scanning electron microscope, X-ray diffraction and vibrating sample magnetometer. The adsorptions of Ni(II) and Sr(II) onto MWCNT/iron oxide magnetic composites were studied as a function of pH and ionic strength. The results show that the adsorptions of Ni(II) and Sr(II) on the magnetic composites is strongly dependent on pH and ionic strength. The adsorption capacity of the magnetic composites is much higher than that of MWCNTs and iron oxides. The solid magnetic composites can be separated from the solution by a magnetic process. The Langmuir model fits the adsorption isotherm data of Ni(II) better than the Freundlich model. Results of desorption study shows that Ni(II) adsorbed onto the magnetic composites can be easily desorbed at pH < 2.0. MWCNT/iron oxide magnetic composites may be a promising candidate for pre-concentration and solidification of heavy metal ions and radionuclides from large volumes of aqueous solution, as required for remediation purposes.

Solid-phase extraction of sulfonylurea herbicides from water samples with single-walled carbon nanotubes disk

This study presents a new, easily made and practical solid-phase extraction disk, a single-walled carbon nanotubes (SWCNTs) disk. The properties of the disk were evaluated by extracting large volumes of aqueous solution (500–3,000 mL) spiked with trace levels of sulfonylurea herbicides, metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl, pyrazosulfuron-ethyl, and chlorimuron-ethyl. The adsorption of analytes on the SWCNTs disk was more favorable at pH 3.0, and the adsorbed sulfonylurea herbicides could be eluted completely with acetonitrile (1% acetic acid) solvent. The disks were stacked to enhance their extraction ability to analytes. The triple layered SWCNTs disks system showed excellent extraction efficiency when the sample volume was up to 3,000 mL. A comparative study was conducted with a commercial C18 disk and an activated carbon disk. The SWCNTs disks showed an adsorption capacity comparable to sulfonylurea herbicides to the C18 disk and activated carbon disk, but the analytes retained on the activated carbon disk were hardly desorbed. Finally, the triple layered SWCNTs disks system was used to pretreat 1,000 mL of several environmental water samples spiked with the analytes, and satisfactory recoveries (79–102%) were obtained. Detection limits of 1.1–7.2 ng L−1 for analytes were achieved under the optimized conditions.

FAAS DETERMINATION OF THALLIUM AFTER PRECONCENTRATION USING NITROSO-S AND TDBA ONTO BENZOPHENONE

Thallium is quantitatively retained by 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S) and tetradecyldimethylbenzylammonium chloride (TDBA) onto benzophenone in the pH range 10.0-11.5 from large volumes of aqueous solutions of various samples. After filtration, each solid mass consisting of thallium complex and benzophenone is dissolved with 5 mL of dimethylformamide and the metal was determined by flame atomic absorption spectrophotometry (FAAS). Eight replicate determinations of 10.0 mg/mL of thallium in final dimethylformamide (DMF) solution gave a mean absorbance of 0.150 with a relative standard deviation of 1.9%. The sensitivity for 1% absorption was 0.293 mg/mL. The method of extraction and preconcentration is economical, rapid, sensitive, highly selective and satisfactory. The interference of a number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of thallium in various samples. KEY WORDS : Flame atomic absorption spectrophotometry, Thallium determination, Nitroso-S, Tetradecyldimethylbenzylammonium chloride (TDBA), Benzophenone Bull. Chem. Soc. Ethiop. 2005, 19(1), 17-22.

Application of 1,2-Dihydroxybenzene-3,5-disulfonic Acid for the Separation and Preconcentration of Trace Molybdenum and Its Determination by Third Derivative Spectrophotometry

Molybdenum was quantitatively extracted form large volumes of aqueous solutions of various samples by 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) and tetradecyldimethylbenzylammonium chloride (TDBA) on microcrystalline naphthalene in the pH range 6.5–8.5. After filtration, the solid residue consisting of molybdenum complex and naphthalene was dissolved in 5 mL of chloroform and molybdenum was determined by third derivative spectrophotometry. Alternatively, molybdenum can be quantitatively adsorbed on Tiron-TDBA-naphthalene adsorbent packed in a column and determined in a similar manner. About 0.02 µg of molybdenum can be concentrated in a column from 500 mL of aqueous sample, where its concentration is as low as 0.04 ng/mL. Various parameters such as the effect of pH, the volume of the aqueous phase, and the interference of a number of metal ions with the determination of molybdenum have been studied in detail to optimize the analysis of standard alloys and biological samples.

Development of new adsorbent chitin for column preconcentration and spectrophotometric trace determination of Ziram and Zineb in synthetic, commercial samples and food-stuffs

A procedure has been developed for the determination of zinc(II) bis(dimethyldithiocarbamate) (Ziram) or zinc(II) ethylenebisdithiocarbamate (Zineb) present in a large volume of aqueous solution after preconcentration on a column using chitin–1-(2′pyridylazo)-2-naphthol (PAN) as adsorbent. Ziram/Zineb are quantitatively retained on the column as Zn–PAN complex in the pH range 9.0–11.0 and at a flow rate of 1–8 ml/min. Complex adsorbed on chitin was eluted from the column with dimethylformamide (DMF) and absorbance of the eluate was measured at 550 nm against a reagent blank. Beer's law is obeyed over the concentration range 5.3–55.8 μg of Ziram and 6.8–49.0 μg of Zineb in 25 ml of the final DMF solution. Ten replicate determinations on a sample solution containing 45.22 μg of Ziram or 40.86 μg of Zineb gave a mean absorbance of 0.30 with a relative standard deviation 1.6 and 1.8%, respectively. The interference of various ions has been studied. Many alkali metals and metal salts do not interfere. The method has been employed to the determination of Ziram and Zineb in commercial samples and in various foodstuffs and the results were compared with the earlier reported methods.

Sorption of 243Am(III) to Multiwall Carbon Nanotubes

Carbon nanotubes have attracted great interest in multidisciplinary study since their discovery. Herein, radionuclide 243Am(III) sorption to uncapped multiwall carbon nanotubes (MWCNTs) was carried out at 20+/-2 degrees C in 0.01 and 0.1 M NaClO4 solutions. Effects of 243Am(III) solution concentration, ionic strength, and pH on 243Am(III) sorption to MWCNTs were also investigated. The sorption is strongly dependent on pH values and weakly dependent on the ionic strength in the experimental conditions. The results show that MWCNTs can adsorb 243Am(III) with extraordinarily high efficiency by forming very stable complexes. Chemisorption or chemicomplexation is the main mechanism of 243Am(III) sorption on the surface of MWCNTs. MWCNTs can be a promising candidate for the preconcentration and solidification of 243Am(III) or its analogue lanthanides and actinides from large volumes of aqueous solution, as required for remediation purposes, and perhaps also as a sorbent for the removal of heavy metal ions from the industry wastewater.

Determination of Trace Cadmium in Waters by Flame Atomic Absorption Spectrophotometry After Preconcentration with 1‐Nitroso‐2‐Naphthol‐3, 6‐Disulfonic Acid on Ambersorb 572

A procedure for the determination of trace amount of cadmium after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been proposed. This chelate is adsorbed on the adsorbent in the pH range 3-8 from large volumes of aqueous solution of water samples with a preconcentration factor of 200. After being sorbed, cadmium was eluted by 5 mL of 2.0 mol L(-1) nitric acid solution and determined directly by flame atomic absorption spectrophotometery (FAAS). The detection limit (3sigma) of cadmium was 0.32 microg L(-1). The precision of the proposed procedure, calculated as the relative standard deviation of recovery in sample solution (100 mL) containing 5 microg of cadmium was satisfactory (1.9%). The adsorption of cadmium onto adsorbent can formally be described by a Langmuir equation with a maximum adsorption capacity of 19.6 mg g(-1) and a binding constant of 6.5 x 10(-3) L mg(-1). Various parameters, such as the effect of pH and the interference of a number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for the preconcentration and determination of cadmium in water samples. This procedure was applied to the determination of cadmium in tap and river water samples.