Removal of sulfamethoxazole antibiotic from aqueous solutions by silver@reduced graphene oxide nanocomposite.

In the present study, the synthesizing of silver@reduced graphene oxide nanocomposite, through a facile precipitation method, is reported. In this method, in the synthesizing step, reduced graphene oxide was applied as a support, silver acetate as a precursor of Ag0, and sodium hydroxide as a medium for reducing procedure. Then synthesized particles were characterized by using transmission electron microscopy analysis, Fourier-transform infrared spectroscopy, field emission scanning microscopy/energy dispersive X-ray, and X-ray diffraction. Adsorbent potentials of the prepared nanocomposite were evaluated for sulfamethoxazole removal from polluted aqueous solutions via two different experimental methods, namely, "one-at-a-time" and "central composite design". The given results from the one-at-a-time method confirms that 0.007 g of silver@reduced graphene oxide nanocomposite can remove 88% (188.57 mg/g) of sulfamethoxazole from a 0.05 dm3 solution (initial concentration 30 mg/dm3) at pH = 5 after 3600 s' contact time. However, in the central composite design method, the optimum condition was 95% (79.17 mg/g) uptake of this drug from 0.05 dm3 of polluted solution with initial concentration of 30 mg/dm3 and pH = 7.5, using 0.018 g of the adsorbent in 3600 s. The main mechanism for sulfamethoxazole removal can be suggested as a suitable interaction between S atoms in functional groups in the drug and Ag atoms on the surface of nanoparticles. The pseudo-second-order patterns and Freundlich model described the empirical data isotherm and kinetics for the adsorption processes, respectively. The maximum adsorption capacity by experimental and theoretical isotherm methods (Langmuir) obtained 250 and 357 mg/g, respectively. Efficiency of the adsorbent in treatment of SMX from real samples displayed less hardness and electrical conductance samples have the maximum uptake percent while existence of nitrate ions in the solutions did not induce any negative effect on the removal of the SMX. All obtained results indicated loading of Ag nanoparticles on rGO nanosheets is an effective strategy for SMX uptake with high proficiency and shows great promise as pollutant adsorbent for environmental applications.

A new diclofenac molecularly imprinted electrochemical sensor based upon a polyaniline/reduced graphene oxide nano-composite.

A diclofenac (DCF)-imprinted polymer, composed of polyaniline, reduced graphene oxide (rGO) and triphenylamine, as cross linker, was synthetized. This composite was identified by using SEM and FT-IR techniques. The prepared DCF-imprinted polymer (MIP) was used for modification of carbon paste electrodes (CPEs) to fabricate a selective DCF electrochemical sensor. Electrochemical behavior of DCF on the investigated sensor and the optimization of the parameters affecting the DCF determination were screened by cyclic voltammetry (CV). The cyclic voltammogram of DCF showed an anodic peak current at about 0.5 V (vs. SCE). The calibration curve for DCF determination was obtained by applying the investigated sensor as working electrode in differential pulse voltammetry (DPV). A linear increase in the anodic peak current was observed in the range 5-80 mg L-1 of DCF. The corresponding limit of detection was calculated to be 1.1 mg L-1. The relative standard deviations of the inter- and intra-day analysis of DCF presented by the method were found to be as 2.43% and 2.47%, respectively. The selectivity of the investigated sensor was evaluated by its use for determination of DCF in the binary solutions containing DCF/glucose, DCF/urea and DCF/ascorbic acid. It was shown that the fabricated electrode can be successfully used for analysis of DCF in pharmaceutical and urine samples.

Silver@ graphene oxide nanocomposite: synthesize and application in removal of imidacloprid from contaminated waters.

Silver@graphene oxide nanocomposite was synthesized through an efficient approach, characterized by FTIR, EDX, and TEM instruments and then was used as adsorbent for imidacloprid removal from water in batch procedure. Effective variants such as contact time, pH, adsorbent dosage, and initial concentration of imidacloprid on procedure by two methods, one at a time and experimental design methods, were studied. Results in optimum conditions based on one at a time experiments is removal of 63% of the pesticide from 50 mL water containing 10 mg/L of imidacloprid by 0.03 g of the adsorbent at pH = 6.6 after 60 min while, experimental design method predict similarity results, 66% uptake of the poison by 0.06 g of the adsorbent in pH = 8. Kinetics and isotherm for adsorption processes follows Freundlich and pseudo-second-order models. Results confirm that Ag@graphene oxide nanocomposite can be applicable for removal of imidacloprid from real polluted water.

Nitrate removal from aqueous solutions by ZnO nanoparticles and chitosan-polystyrene-Zn nanocomposite: Kinetic, isotherm, batch and fixed-bed studies.

Chitosan-polystyrene-Zn nanocomposite was synthesized through precipitation procedure and well characterized by analytical instruments such as Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. After characterizations, the nanocomposite was applied as an adsorbent for removal of nitrate ions from aqueous solutions. The study parameters influencing batch adsorption show that 0.5g of chitosan-polystyrene-Zn nanocomposite removed 90% of the nitrate ions (initial concentration 10mg/L) from 25mL of water at pH=3 after 30min while, in fixed-bed column technique, and at a similar condition, it removed 82.5% of nitrate. On the other hand, ZnO nanoparticles after activation by HCl solution applied for removal of nitrate contamination at the same condition which was used for chitosan-polystyrene-Zn nanocomposite. But ZnO nanoparticles removed all nitrate in the polluted solution in both techniques. The Elovich and the Langmuir models successfully exhibited the experimental data kinetic and isotherm for the adsorption processes.

Potential of polyaniline modified clay nanocomposite as a selective decontamination adsorbent for Pb(II) ions from contaminated waters; kinetics and thermodynamic study.

BACKGROUND: Nowadays significant attention is to nanocomposite compounds in water cleaning. In this article the synthesis and characterization of conductive polyaniline/clay (PANI/clay) as a hybrid nanocomposite with extended chain conformation and its application for water purification are presented. METHODS: Clay samples were obtained from the central plain of Abhar region, Abhar, Zanjan Province, Iran. Clay was dried and sieved before used as adsorbent. The conductive polyaniline was inflicted into the layers of clay to fabricate a hybrid material. The structural properties of the fabricated nanocomposite are studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). The elimination process of Pb(II) and Cd(II) ions from synthetics aqueous phase on the surface of PANI/clay as adsorbent were evaluated in batch experiments. Flame atomic absorption instrument spectrophotometer was used for determination of the studied ions concentration. Consequence change of the pH and initial metal amount in aqueous solution, the procedure time and the used adsorbent dose as the effective parameters on the removal efficiency was investigated. RESULTS: Surface characterization was exhibited that the clay layers were flaked in the hybrid nanocomposite. The results show that what happen when a nanocomposite polyaniline chain is inserted between the clay layers. The adsorption of ions confirmed a pH dependency procedure and a maximum removal value was seen at pH 5.0. The adsorption isotherm and the kinetics of the adsorption processes were described by Temkin model and pseudo-second-order equation. Time of procedure, pH and initial ion amount have a severe effect on adsorption efficiency of PANI/clay. CONCLUSIONS: By using suggested synthesise method, nano-composite as the adsorbent simply will be prepared. The prepared PANI/clay showed excellent adsorption capability for decontamination of Pb ions from contaminated water. Both of suggested synthesise and removal methods are affordable techniques.

Molecular imprinting method for fabricating novel glucose sensor: polyvinyl acetate electrode reinforced by MnO2/CuO loaded on graphene oxide nanoparticles.

An enzyme free glucose sensor was prepared by a molecular imprinting method (MIP). The procedure was developed by in situ preparation of a new polyvinyl acetate (PVA) electrode reinforced by MnO2/CuO loaded on graphene oxide (GO) nanoparticles (PVA/MnO2@GO/CuO). The nanocomposite was modified in the presence of glucose and then imprinted. A carbone paste method with voltammetry was used in the fabrication of the sensor from prepared MIP nanocomposite. PVA/MnO2@GO/CuO electrode was characterized by X-ray diffraction, FT-IR spectroscopy and scanning electron microscopy. Electrocatalytic activity of the electrode toward glucose oxidation was then investigated by cyclic voltammetry in alkaline medium. The results show that the response of PVA/MnO2@GO/CuO MIP is much higher than PVA/MnO2@GO/CuO non-imprinted electrode toward glucose oxidation. The detection limit was 53µM, and the sensor responses are linear for concentrations from 0.5 to 4.4mM. Relative standard deviations for intra- and inter-day determination were less than 6.0%. The relative recoveries for different samples were 96%.