Carbon spheres (CSs) were synthesized from sucrose by hydrothermal reaction. The synthesized materials were further
activated with potassium hydroxide (KOH) at different concentrations. The effects of KOH concentration on the surface area
and morphology were investigated. The route for pore formation and structural deformation in carbon spheres during
activation has been proposed and discussed based on micrographs and porosity trends. It was suggested that the pore
formation and structural deformation phenomena were due to the intercalating power of energized K+ into the carbon.
This work provides an insight of the pore formation in carbon spheres for the development of adsorbents as well as for
the understanding of the structural deformation of such materials at higher KOH concentrations.
A simple and rapid sample preparation method based on dispersive liquid-liquid microextraction-solidification of floating organic drop (DLLME-SFO) combined with gas chromatography-mass spectrometry (GC-MS) method was developed for the analysis of antidepressant drugs in water samples. This method uses organic solvent with low density and less toxicity. In the method, the disperser solvent (0.5 mL acetonitrile) containing 30 μL of n-hexadecane was rapidly injected using a syringe into 5.0 mL of water sample in a glass tube. After centrifugation for 7 min at 3500 rpm, the mixture was cooled in ice bath for 5 min. The solidified n-hexadecane was transferred into a conical vial, where it melted rapidly at room temperature and 2 μL of it was injected into a gas chromatograph for analysis. Under optimized conditions, the method showed good linearity in the range of 0.04 - 0.12 μg mL-1 for amitriptyline and chlorpromazine with correlation of determination (r2) in the range of 0.992 - 0.995. The limits of detections (LODs) were in the range 0.0085 - 0.0285 μg mL-1. The extraction recoveries of amitriptyline and chlorpromazine from water samples at spiking level of 0.08 μg mL-1 were 71.34 - 73.52% and 73.83 - 91.09%, respectively, with relative standard deviations (RSDs) in the range of 4.97 - 6.85% for amitriptyline and 4.84 - 7.49% for chlorpromazine. The method was successfully applied to the determination of the analytes in drinking water, lake water and tap water samples.
A method has been developed for the determination of epoxidized soybean oil (ESBO) in oily foods stored in glass jars with metal lids using gas chromatography-mass spectrometry (GC-MS). ESBO and its internal standard (cis,cis-11,12;14,15- diepoxyeicosanoate) were isolated from the matrix by transesterification process. The developed method showed good linear dynamic range between 0.7-20 μg mL-1 with coefficients of determination (R2) > 0.9968 and acceptable limit of detection and limit of quantitation of 7 and 23 mg kg-1, respectively, based on linearity calculations. Analyte recoveries were 90.84±27.24% for low concentration, 78.05±11.59% for medium concentration and 99.23±10.20% for high concentration. This first fully validated GC-MS method was successfully applied for the determination of ESBO in foods stored in glass jar with metal lid. Among the 31 food samples studied, 6 samples were found to exceed the specific migration limit of 60 mg kg-1 (based on EU Directive 2002/72/EC). The developed method is thus potentially useful for routine analysis for the determination of ESBO.
Ammonium persulfate (APS)-initiated grafting of methacrylamide (MAM) onto chitosan was successfully prepared for the first time by free radical mechanism. Both chitosan and chitosan-graft-poly(methacrylamide) (chitosan-g-PMAM) were characterized using Fourier transform infrared spectroscopy (FTIR), solid state 13C NMR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Important factors affecting graft copolymerization such as reaction time, temperature and concentrations of APS, MAM and chitosan were investigated and optimized to obtain maximum grafting parameters. The optimum values for grafting percentage and yield of graft copolymerization were achieved under the following conditions: chitosan (1 g), MAM (4 g), APS (0.6 g), time reaction (4 h) and temperature (70ºC).
The presence of heavy metal and radionuclides in water bodies has been a long-lasting environmental problem which results in many undesirable consequences. In this framework, the biosorption process, which uses inexpensive and naturally produced material such as alginate, is an alternative technology in the environmental remediation. This review provides relevant and recent literature regarding the application of alginate and its derivatives on removal of various heavy metal ions and radionuclides. The effects of process variables such as solution pH, adsorbent dosage, metal ion concentration, contact time, temperature and co-existing ions used in batch studies in addition to kinetic, isothermal models as well as thermodynamic that fit the adsorption experimental data are critically discussed. This review also includes mechanisms involved during adsorption process. Furthermore, future research needs for the removal of contaminants by alginate-based materials with the aims of improving their adsorption performance and their practical applications are commented.