Optimization of an anode for arsenic(V) extraction

Abstract

Electrochemical methods has led to the preparation of a poly(pyrrole)-modified steel electrode (SS/PPy) for testing and optimizing the polymer doping/undoping process for arsenic(V) removal. Potentiodynamic (cyclic voltammetry) electropolymerization optimal range was between −0.200 and 0.980 V vs SCE. On the other hand, the potentiostatic optimal working potential was 0.980 V. SS/PPy-modified electrode prepared under either of these optimum conditions displayed a doping/undoping process occurring at 0.700 and −0.200 V, respectively. Hence, As(V) extraction or removal was performed by incorporating the cation to SS/PPy applying a 0.700 V constant potential. Then, As(V) doped SS/PPy was transferred to another cell, in which the undoping potential (−0.200 V) was applied to remove the ion from the polymer matrix, completing thus the extraction cycle (EC). This way, for instance, with a SS of 10 cm² geometric area and potentiostatic deposition carried out for 10 min, arsenic removal rates over 77 % were attained for 10 EC of 60 s each. This outcome allows predicting a promising future for the method as As(V) extractor from aqueous solutions. Furthermore, the modified electrode exhibited acceptable conditions for developing a likely arsenic sensor, since a linear current vs As(V) concentration relationship exits, at least in the order of concentrations used herein (50–500 ppm).