In the present study, facile and competent homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) method combined with flow injection flame atomic absorption spectrometry (FI-FAAS) was proposed for simultaneous separation/ preconcentration and determination of trace amounts of cadmium and copper in water samples. The efficient 2-(3,4-dihydroxyphenyl)-1,3-dithiolane (DHPDTO) with thiol groups was used as chelating reagent. The predominant parameters influencing the HLLME-FA, such as solution pH, concentration of DHPDTO, extraction and homogeneous solvent types and volumes, ionic strength, and extraction time were studied. Applying all the optimum conditions in the process, the detection limits of 0.008 and 0.01 μg L −1 , linear ranges of 0.08-40 and 0.1-45 μg L −1 , and the precision (RSD%, n=7) of 3.4 and 3.9 % were obtained, respectively, for cadmium and copper. The proposed procedure showed satisfactory results for analysis of tap water, river water, well water, and seawater.
In this study, carboxylic multiwall carbon nanotubes (CMNTs) were used as an adsorbent for removing fenvalerate as a toxic insecticide from solution through batch experiments. The influence of four independent parameters of HCl, initial fenvalerate concentration, CMNTs dosage, and contact time on the fenvalerate adsorption process was investigated. Raman spectroscopy and thermogravimetric analysis confirmed that the adsorption and maximum adsorption capacity (40.0 mg g -1 ) showed high adsorption potential of the proposed sorbent. The kinetic, isothermic, and thermodynamic of fenvalerate adsorptionon CMNTs were evaluated to better understand this environmental friendly adsorption strategy. A pseudo-first-order kinetic described very well the experimental data of the adsorption kinetics. The experimental data found to be properly fitted to Freundlich model, which indicates that the sorption takes place on a heterogeneous material. The thermodynamic results showed the negative value of the standard free energy (DG 0 ) and standard enthalpy change (DH 0 ) showing an exothermic and spontaneous system. Repeated availability of adsorbent investigated and SEM and HRTEM of reused adsorbent showed stability and non-aggregatable attributes of CMNTs.
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