Remediation of chromium(VI) at polypyrrole-coated titanium

Abstract

The application of conducting polypyrrole (PPy) and polyaniline (PAni) coated substrates in remediation of chromium, Cr(VI), is an area of considerable interest. Here, we discuss the implementation of PPy-coated titanium as a new material for the reduction of Cr(VI) to the less toxic trivalent state, Cr(III). An alkaline-peroxide based etching process was used to ensure the adhesion of the PPy coatings to the underlying titanium. The PPy films showed excellent resistance to acidic Cr(VI) solutions and remained adherent after continuous exposure to the solutions. In order to optimise the remediation process a number of experimental parameters were investigated, including the thickness of the PPy coating, the reduction potential used in pre-treatment of the PPy and the degree of solution agitation. The durability of the materials on exposure to the Cr(VI) test solutions made them suitable for repeated remediation experiments. Following several test-runs, the cleanup efficiency of the material was found to decrease slightly, however, increasing the exposure/experiment time resulted in significantly improved cleanup ability.

Polyacrylonitrile/manganese acetate composite nanofibers and their catalysis performance on chromium (VI) reduction by oxalic acid

“…The composite nanofibers have performed excellent capability for catalyzing Cr(VI) reduction by oxalic acid from a Cr 2 O 7 2− containing solution and the larger the content of Mn(CH 3 COO) 2 was, the faster the reduction reaction became. After 180 min, 1.2 mM initial Cr(VI) solution was reduced by 90% in the presence of PAN/Mn(CH 3 COO) 2 composite nanofibers containing 22.0 wt.% Mn(CH 3 COO) 2 by 0.3 mL 0.5 M oxalic acid, which was much higher than the previously reported values of the other reduction methods [17,[31][32][33]. The catalyst dosage, oxalic acid content, chromium concentration and the pH value of the reaction solution had significant impact on the reduction process.…”