[Show abstract][Hide abstract] ABSTRACT: This work reports on the adsorption efficiency of two classes of adsorbents: nano-adsorbents including carbon nanotubes (CNTs) and carbon nanofibers (CNFs); and micro-adsorbents including activated carbon (AC) and fly ash (FA). The materials were characterized by thermogravimetric analysis, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area, zeta potential, field emission scanning electron microscopy, and UV spectroscopy. The adsorption experimental conditions such as pH of the solution, agitation speed, contact time, initial concentration of phenol, and adsorbent dosage were optimized for their influence on the phenol. The removal efficiency of the studied adsorbents has the following order: AC > CNTs > FA > CNFs. The capacity obtained from Langmuir isotherm was found to be 1.348, 1.098, 1.007, and 0.842 mg/g of AC, CNTs, FA, and CNFs, respectively, at 2 hours of contact time, pH 7, an adsorbent dosage of 50 mg, and a speed of 150 rpm. The higher adsorption of phenol on AC can be attributed to its high surface area and its dispersion in water. The optimum values of these variables for maximum removal of phenol were also determined. The experimental data were fitted well to Langmuir than Freundlich isotherm models.
[Show abstract][Hide abstract] ABSTRACT: The efficiency of Fe2O3, Al2O3 and TiO2 nanoparticles-loaded activated carbon (AC) for the adsorption of phenol from waters, was investigated. The raw and doped ACs were characterized by using Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Thermogravimetric analysis and Brunauer–Emmett–Teller surface analysis. Batch adsorption experiments were performed to evaluate the effects of solution pH, agitation speed, contact time, adsorbent dosage and ionic strength on the phenol removal efficiency. Activated carbon impregnated with Fe2O3, Al2O3 and TiO2 showed higher adsorption capacity compared to raw AC. The maximum removal of phenol was achieved by iron oxide, aluminum Oxide and titanium oxide doped AC under the optimum conditions of 200 mg dosage, at pH 7, 150 rpm agitation speed, 2 ppm initial phenol concentration and contact time of 2 h. While for raw AC, the maximum removal was achieved for an adsorbent dosage of 300 mg under the same treatment conditions. The Langmuir isotherm model best fitted the data of the adsorption of phenol using AC, AC–TiO2, AC–Fe2O3 and AC–Al2O3, with correlation coefficient of 0.971, 0.96, 0.976 and 0.972. Surface characterization of both the impregnated AC showed an improvement in its surface area of the doped AC. The adsorption capacities, as determined by the Langmuir isotherm model were 1.5106, 3.1530, 3.2875 and 3.5461 mg/g for raw AC, AC–TiO2, AC–Fe2O3 and AC–Al2O3.
Journal of Molecular Liquids 09/2015; DOI:10.1016/j.molliq.2015.08.044 · 2.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Silver hydroxide nanoparticles (AgOH-NPs) were efficiently festooned onto multiwalled carbon nanotubes (MWCNTs) and characterized by analytical techniques such as SEM, FT-IR and BET analysis. These were used for the removal of radioactive uranium(VI) followed by its complexation with eriochrome cyanine R in the presence of cetyl trimethyl ammonium bromide (CTAB). The adsorption process and its mass transfer were accelerated and assisted using ultrasound waves. The AgOH-NPs–MWCNTs has large surface area that was suitable for qualitative and quantitative removal of UO22+ ion. The effect of several parameters was optimized by central composite design (CCD) and the respective value was set as follows: adsorbent mass (5 mg), contact time (10 min), initial UO22+ ions concentration (2 mg L−1) and initial ECR concentration (8 mg L−1). It was found that UO22+ ion adsorption follow combination of the pseudo-second-order rate equation and intraparticle diffusion model. Equilibrium data well fitted with the Freundlich model and reveal that the small amount (5 mg) of AgOH-NPs–MWCNTs is sufficient for removal of high amount of UO22+ ion (R > 96% and adsorption capacity of 140 mg g−1) in a 10 min contact time.
Chemical Engineering Journal 08/2015; 273. DOI:10.1016/j.cej.2015.03.002 · 4.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Silica combined with 2 % multiwall carbon nanotubes (SiO2-CNT) was synthesized and characterized. Its sorption efficacy was investigated for the Hg(II) removal from an aqueous solution. The effect of pH on the percentage removal by the prepared material was examined in the range from 3 to 7. The adsorption kinetics were well fitted by using a pseudo-second-order model at various initial Hg(II) concentrations with R (2) of >0.99. The experimental data were plotted using the interparticle diffusion model, which indicated that the interparticle diffusion is not the only rate-limiting step. The data is well described by the Freundlich isotherm equation. The activation energy (Ea) for adsorption was 12.7 kJ mol(-1), indicating the process is to be physisorption. Consistent with an endothermic process, an increase in the temperature resulted in increasing mercury removal with a ∆H(o) of 13.3 kJ/mol and a ∆S(o) 67.5 J/mol K. The experimental results demonstrate that the combining of silica and nanotubes is a promising alternative material, which can be used to remove the mercury from wastewaters.
Environmental Science and Pollution Research 06/2015; DOI:10.1007/s11356-015-4866-z · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work, ferric Oxidenanoparticles decoratedcarbon fibers and carbon nanotubes (CNF/Fe2O3 and CNT/Fe2O3) were synthesized and characterizedby Scanning Electron Microscopy (SEM), thermogravimetricanalysis (TGA), Energy Dispersive X-ray Spectroscopy (EDS),Transmission electron microscopy (TEM), X-ray Diffraction (XRD), Zeta Potential and BET surface area analyzer. The prepared nanocomposites were evaluated or the removal of phenol ions from aqueous solution.The effects of experimental parameters, such as shaking speed, pH, contact time, adsorbent dosage and initial concentration,were evaluated for the phenol removal efficiency. The adsorption experimental data were
represented by both the Langmuir and Freundlich isotherm models. The Langmuir isotherm
model best fitted the data on the adsorption of phenol, with a high correlation coefficient.The
adsorption capacities, as determined by the Langmuir isotherm model were 0.842, 1.098,
1.684 and 2.778 mg/g for raw CNFs, raw CNTs, CNF-Fe2O3 and CNT-Fe2O3 respectively.
Journal of Saudi Chemical Society 06/2015; 19(5):511–520. DOI:10.1016/j.jscs.2015.06.002 · 2.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present work reports on the efficiency of activated carbon loaded with zinc oxide nanoparticles (AC/ZnO) for removing dichloromethane, trichloromethane and carbon tetrachloride from aqueous solutions. Waste tires were used as a raw material for the production of activated carbon (AC) by thermo-chemical process. Zinc oxide nanoparticles were loaded into AC by using Zn(NO3)2.6H2O. The AC/ZnO composite has been characterized by BET analyzer, scanning electron spectroscope, energy dispersive X-ray spectroscope, FTIR spectrophotometer, and X-ray diffraction. Batch experiments were conducted under various adsorbent dosages, initial concentrations and contact time. Rapid adsorption was observed with adsorption capacity of 6.67 mg/g for dichloromethane, 11.91 mg/g for chloroform and 16.10 mg/g for carbon tetrachloride. The equilibrium was obtained in 20 min of contact time. The adsorption of these pollutants onto AC/ZnO was described well by the pseudo second-order model, and the hydrophilic fraction adsorption fitted the intraparticle diffusion model. Freundlich and Langmuir models were used to evaluate the process, and the Langmuir adsorption isotherm model fitted the data better than other models. The reusability of the composite was proved when no significant decrease in its adsorption capacity was observed even after several times of regeneration.
Journal of the Taiwan Institute of Chemical Engineers 05/2015; DOI:10.1016/j.jtice.2015.04.004 · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work, a unique cross-linked polyzwitterion/anion having aspartic acid residue was synthesized via butler’s cyclopolymerization protocol involving N,N-diallylaspartic acid hydrochloride, 1,1,4,4-tetraallylpiperazinium dichloride and sulfur dioxide in the presence of azoisobutyronitrile. The structure and morphology of the polymer were characterized by using FTIR, TGA, EDX and SEM. The adsorption performance of the resin was evaluated using lead Pb(II) as model. The effect of various parameters such as contact time, pH, initial concentration and temperature were investigated to arrive at optimum conditions. Optimum pH of 6.0 and dosage of 1.5g L-1 were obtained. The mechanism of adsorption was investigated using kinetic, diffusion, isotherm and thermodynamic models. The adsorption kinetic data were described well by the pseudo-second order model with R2 of 0.999. The activation energy (Ea) of the adsorption process was calculated as 39.29 kJ mol−1. The negative ∆Go values indicate a spontaneous adsorption process while the negative ∆Ho (-43.87 KJ/mol) suggests an exothermic reaction. Adsorption data were described well by the Langmuir and Temkin models. EDX analysis confirmed the adsorption of Pb2+on the polymer. The overall results suggest that the polymer could be employed as an efficient adsorbent for the adsorption of toxic Pb2+ from polluted aqueous solutions.
[Show abstract][Hide abstract] ABSTRACT: A film-shear reactor was used to significantly enhance the oxidative desulfurization (ODS) of model fuels using hydrogen peroxide as the oxidant. Significant increases in the amount of sulfur removed were seen in comparison to conventionally stirred ODS reactions. For example, up to 50% desulfurization occurred in a single pass of the model fuel through the film-shear reactor at 10 °C. The desulfurization reactions were very fast in the reactor, occurring on the time scale of seconds to minutes. Desulfurization was studied under a variety of conditions, and a statistical design of experiment (DOE) showed that the fuel to oxidant ratio was the only statistically significant parameter to impact the extent of desulfurization: a larger amount of oxidant led to higher desulfurization. A variety of benzothiophene contaminants (benzothiophene, 2-methylbenzothiophene, 5-methylbenzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene) were examined, and the film-shear reactor was effective in removing all of these contaminants. The film-shear reactor was effective at both low (0.5-2.0 mL/min) and high (100-300 mL/min) flow rates. Experiments showed that oxygen in air was not an effective oxidant for ODS in the film-shear reactor. Experiments using Mo(CO)6 as a molecular thermometer showed that “hot spots” are not forming in the film-shear reactor, and thus the increase in the ODS rate cannot be attributed to intense thermal activation occurring within the film-shear reactor. It is suggested that superb mixing of the aqueous and fuel phases is responsible for the increased rate of ODS in the reactor.
[Show abstract][Hide abstract] ABSTRACT: In the present work, alumina/carbon nanotube nanocomposite was synthesized and characterized using field
emission scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface analyzer. The nanocomposite was evaluated for the 4-chlorophenol and phenol removal from aqueous solution with comparison to the pristine carbon nanotubes. Batch adsorption experiments were carried out to evaluate the effect of pH, agitation speed, contact time, adsorbent dosage, and initial concentration on the 4-chlorophenol and phenol removal efficiency. Experimental result showed the adsorption of 4-chlorophenol and phenol by nanocomposite to be pH dependent with the highest removal achieved at pH 6. CNTs showed better adsorption efficiency than CNT–Al2O3 which could be assigned to the increase in the surface area from 155.5 m2/g of CNT to 227.5 m2/g of CNT–Al2O3. Langmuir and Freundlich isotherm models were applied for analyzing adsorption equilibrium data of 4-chlorophenol removal on the as-prepared nanocomposite and pristine carbon nanotubes, which suggested that the Langmuir model provides better correlation of the experimental data with R2 of 0.994 and 0.999 respectively. While for phenol, correlation coefficients of Langmuir adsorption isotherm model were 95% and 99.4% for CNT and CNT–Al2O3 respectively.
[Show abstract][Hide abstract] ABSTRACT: In this work, the potential of fly ash impregnated with aluminum oxide (FA-Al2O3) for adsorption of phenol from aqueous solution was studied. Batch adsorption experiments were carried out to evaluate the effects of the experimental parameters pH, agitation speed, contact time, adsorbent dosage, and initial concentration on the phenol removal efficiency. The adsorption of phenol by FA-Al2O3 was found to be pH dependent with the best removal achieved at pH 7. The optimum set of parameters for the removal were, 200 rpm agitation speed, 200 mg adsorbent dosage, 2 h contact time, and 2 ppm initial phenol concentration. Both the Langmuir and Freundlich isotherm models represented the adsorption experimental data. However, the Langmuir isotherm model best fitted the data on the adsorption of phenol using FA and FA-Al2O3, with correlation coefficient of 97.7 and 97.9, respectively. The improvement in the adsorption efficiency of FA-Al2O3 over FA could be attributed to the increase in the surface area, which was found to be 11.889 m2/g and 7.1 m2/g for FA-Al2O3 and FA, respectively.
Desalination and water treatment 02/2015; DOI:10.1080/19443994.2015.1010238 · 1.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The cross-linked tetrapolymeric anionic polyelectrolyte (CAPE) was synthesized. The sorption activity of CAPE was evaluated for the adsorption of chromium (III). Adsorption process fitted the pseudo-second order kinetic model well. The CAPE is of fast uptake with high capacity and reusability. g r a p h i c a l a b s t r a c t a b s t r a c t A novel cross-linked acidic tetrapolymer (CPZA) was synthesized via the cyclopolymerization of different zwitterionic monomers bearing amino, carboxylate, phosphonate and sulfonate motifs and a cross-linker using ammonium persulfate as the initiator. The cross-linked tetrapolymeric anionic polyelectrolyte (CAPE) was obtained by the treatment of CPZA with NaOH. The sorption activity of CAPE was evaluated for the adsorption of chromium (III) using batch equilibrium technique. The experimental data fitted Langmuir, Freundlich and Temkin isotherm models. The maximum adsorption capacity was found to be 48.5 mg/g at pH 5.5 and temperature of 296 K. The adsorption process fitted pseudo-second order kinetic model well and the mechanism was studied by intraparticle diffusion model. Thermodynamic parameters reveal that the adsorption process was endothermic in nature. The resin has not only the advantages of fast uptake with high capacity but also the ease of reusability and good stability. The resin demonstrates an excellent ability to remove chromium (III) ions even from real wastewater samples, suggesting that the resin could be a good candidate for real sorption applications.
Chemical Engineering Journal 02/2015; 269:9. DOI:10.1016/j.cej.2015.01.083 · 4.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This work reports a comprehensive study of the adsorption characteristics of cadmium(II) on modified structures of carbon nanotubes (CNTs), carbon nanofibres (CNFs), activated carbon (AC), and fly ash (FA). The characterization was performed using field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface analysis. Several experimental parameters; adsorbent dosage, pH, and agitation speed and contact time, were investigated for their effects on the adsorption of cadmium(II) from water. The optimum conditions of 2 h of contact time, pH 7, 50 mg adsorbent dosage and 150 rpm rotational speed were observed. Models of first-order, second-order and pseudo-second-order were fitted to the experimental data, and pseudo-second-order kinetics were observed to describe the adsorption of cadmium(II) on these adsorbents. The adsorption behaviours of cadmium(II) were evaluated using the Freundlich and Langmuir isotherm models. The maximum adsorption capacities of the modified adsorbents were observed to be 2.02 mg/g, 1.98 mg/g, 1.22 mg/g and 1.58 mg/g, for CNTs, AC, CNFs and FA, as obtained from Langmuir isotherm models. It was determined that surface modification of the CNTs, CNFs, and AC enhanced their adsorption efficiency. The results obtained are promising for the use of these modified materials with respect to water purification applications.
Journal of Molecular Liquids 01/2015; DOI:10.1016/j.molliq.2015.01.033 · 2.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Exfoliated polystyrene/layered double hydroxide (PS/LDH) nanocomposites were prepared by direct intercalation of PS into MgAl LDH at 60 C. The MgAl LDH as the nanofiller was modified via the precipitation of the salt mixture of magnesium and aluminum metals by sodium dodecyl sulfate (SDS). Various techniques, Fourier Transformed Infrared Spectroscopy (FTIR), X-Ray-diffraction (XRD), Filed Emission Transmission Electron Microscopy (FETE) and thermo gravimetric analyses (TGA) were employed for structural properties and thermal stability of the nanocomposites. FTIR spectra indicated the presence of both functional groups of SDS–LDH and PS. XRD patterns and TEM images indicated the formation of amorphous dispersed and exfoliated nanocomposites. Increase in thermal stability with SDS–MgAl LDH content was observed by TGA and DTG through the T 0.5 (T 0.5 the degradation temperature at 50%) and T max (T max the maximum rate of change) with a maximum obtained for a loading of 2 and 4 wt%.
[Show abstract][Hide abstract] ABSTRACT: In this study the electrochemistry of carbidopa (CD) was studied by electrochemical methods at a carbon paste electrode modified by ZnO/CNTs nanocomposite and room-temperature ionic liquid, n-hexyl-3-methylimidazolium hexafluoro phosphate (ZnO/CNTs/ILs/CPE). The oxidation peak potential of the CD at a surface of ZnO/CNTs/ILs/CPE appeared at 570 mV that was about 90 mV lower than the oxidation peak potential at the surface of the unmodified carbon paste electrode (CPE) under similar condition. Under the optimized conditions, the oxidation peak current of CD showed two linear dynamic ranges (in 0.09–450 μmol L−1) with a detection limit of 0.05 μmol L−1, using square wave voltammetry (SWV). The proposed sensor was successfully applied for the determination of CD in real samples such as pharmaceutical serum, water and urine.
International journal of electrochemical science 12/2014; 10(2). · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The remarkable increase in the number of vehicles worldwide; and the lack of both technical and economical mechanisms of disposal make waste tires to be a serious source of pollution. One potential recycling process is pyrolysis followed by chemical activation process to produce porous activated carbons. Many researchers have recently proved the capability of such carbons as adsorbents to remove various types of pollutants including organic and inorganic species. This review attempts to compile relevant knowledge about the production methods of carbon from waste rubber tires. The effects of various process parameters including temperature and heating rate, on the pyrolysis stage; activation temperature and time, activation agent and activating gas are reviewed. This review highlights the use of waste-tires derived carbon to remove various types of pollutants like heavy metals, dye, pesticides and others from aqueous media.
Advances in Colloid and Interface Science 09/2014; 211. DOI:10.1016/j.cis.2014.06.006 · 7.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This work reports the recycling of waste rubber tires (WRT) to produce a carbonaceous material as adsorbent of an environmental value. The produced material was activated by thermal–chemical process. The WRT-derived carbonaceous adsorbent (CA) was characterized by means of scanning electron microscope, energy-dispersive X-ray spectroscopy and infrared and Raman spectroscopic techniques. The developed CA was tested and evaluated as potential adsorbent for methyl orange (MO) removal. A series of MO stock solutions whose concentrations range from 1 × 10− 6 to 1 × 10− 4 M was prepared to investigate the possible activity of CA. Experimental parameters such as dosage amount, initial concentration and temperature were optimized. A rapid and fast equilibrium has been observed. The maximum adsorption took place in the pH range of 3–5. The temperature-effect study revealed that the process is exothermic. A possible adsorption mechanism has been suggested on the view of calculated frontier molecular orbitals of the methyl orange molecule.