Optimization of Experimental Parameters for Retention of Pb(II) Ions From Aqueous Solution on Clay Adsorbent

The removal of Pb(II) ions is an important issue for the treatment of industrial wastewater, due to its serious consequences on environment and human health. In this study a local clay material was tested as adsorbent for the retention of Pb(II) ions from aqueous solution. The proposed method can be considered low-cost, mainly due to the high availability of clay material in this region, and the high removal percent of Pb(II) ions (> 99%) allows us to say that this method has a high efficiency. Therefore, the finding of the optimal values of the most important experimental parameters which affects the efficiency of Pb(II) ions adsorption on clay adsorbent, represent the next important step in highlighting the practical applicability of this process. The most important experimental parameters, including initial solution pH,adsorbent dose, initial Pb(II) ions concentration, contact time and temperature, were analyzed in batch systems. The obtained experimental results indicates that the efficiency of adsorptionprocess is highest at initial solution pH of 7.0, 4.0 g adsorbent/L, 5 min of contact time and high temperature (50 ?C). Under these conditions, the removal percent of Pb(II) ions is over 99 % over the initial concentration range between 20 and 310 mg Pb(II)/L. The results of this study suggest that this clay material is an excellent adsorbent for Pb(II) ions removal and broadens the potential applicability of these materials in environmental remediation

Studying electron transfer reaction at the Au/n-decanethiol/aqueous solution of NaNO3 interface by electrochemical impedance spectroscopy

The electrochemical behavior of the gold/electrolyte interface in aqueous 1 M NaNO3 solutions in the presence of an organic monolayer of n-decanethiol (CH3(CH2)9S) is studied by electrochemical impedance spectroscopy in the frequency range of 10-10 5 Hz and also by cyclic voltammetry. It is experimentally shown that in the potential interval from 0 to -0.5 V (vs. SCE), the dense monolayer film decreases the measured current density approximately 40-fold. The measured capacitance falls down to 1-2 \u3bcF/cm2. Based on the analysis of impedance characteristics acquired with the use of empirical equivalent circuits comprising ideal and nonideal analogues of electric circuits, the tentative estimates of the thickness of organic monolayers formed on Au electrodes with various roughness factors are obtained. Using the complex nonlinear regression (CNLS) method and a model of microarray electrode, the porous structure of adsorbed monolayers is revealed and the transition frequency of interfaces under study is determined. The degree of inhibition of the electron transfer across the Au/n-decanethiol/solution interface is determined by comparing the rate constants for the Ru[(NH3)6]3+/2+ redox process on clean and modified electrodes