Characterizing the reactivity of metallic iron for water defluoridation in batch studies.

The suitability of metallic iron (Fe(0)) for water defluoridation is yet to be understood. Fluoride removal ([F-]0 = 20.0 mg L-1) and Orange II discoloration ([Orange II]0 = 10.0 mg L-1) by Fe(0)/H2O batch systems are compared herein. A steel wool (SW) and a granular iron (GI) are used as Fe(0) specimens. Each essay tube contains 0.5 g sand and 0.1 g of the used Fe(0). Investigated systems were: (i) SW/sand at pH 5.0, (ii) GI/sand at pH 5.0 and (iii) SW/sand at pH 8.0. Prior to contaminant addition, Fe(0) was allowed to pre-corrode within the systems for up to 46 days. The systems were then equilibrated for 30 days with a mixture of the two model contaminants. Result confirmed (i) the higher efficiency of SW over GI in removing both contaminants, (ii) the higher efficiency of Fe(0) for Orange II discoloration and (iii) the positive impact of initial low pH values on the efficiency of Fe(0)/H2O systems. The major output of this research is that conventional Fe(0)/H2O systems are not suitable for quantitative water defluoridation. It is suggested that ways to avoid defluoridation using Fe0 must be explored. One affordable opportunity is blending fluoride-polluted water with carefully harvested rainwater.

Voltammetric behavior of Mammeisin (MA) at a glassy carbon electrode and its interaction with Bovine Serum Albumin (BSA).

The electrochemical oxidation of Mammeisin (MA) was studied in a solution containing acetone and 0.1M phosphate buffer +0.1M KCl (pH=5.3) at a glassy carbon electrode (GCE), using cyclic (CV) and square wave voltammetry (SWV). MA showed a quasi-reversible process, which is pH dependent and that involves the exchange of two electrons and two protons. The oxidation product was adsorbed by the electrode surface to form a film that blocks active sites over repetitive cyclic. Moreover, the interaction of MA and bovine serum albumin (BSA) was studied by CV and SWV at different pHs (5.4, 7.2, 9.5). As a result of the affinity binding with BSA, electrochemically inactive complex was formed. In addition, the oxidation potential of MA in the presence of BSA depends on the pH. The diffusion coefficients of both free and bound MA were estimated from the cyclic voltammetry data using the method developed by Randles-Sevich (Df=9.85×10-5cm2s-1 and Db=1.27×10-9cm2s-1) and the binding constant of MA-BSA complex, K=3.47×102Lmol-1, was obtained.