Ferric sludge derived from the process of water purification as an efficient catalyst and/or support for the removal of volatile organic compounds

Abstract

Ferric chloride solutions are used as coagulants or flocculants in water treatment operations for human consumption. This treatment produces large amounts of clay-type solids formed mainly of montmorillonite with iron oxides and humic substances. This ferric sludge can be used as an efficient catalyst for the removal of volatile organic compounds (VOCs) by total oxidation. This waste isolated in the purification process has been activated by calcinations in air, characterized by several physicochemical techniques and employed as a catalyst for the removal by total oxidation of representative VOCs: toluene, propane and mixtures of toluene/propane with or without water. This ferric sludge has shown a catalytic activity one order of magnitude higher than that of a commercial iron oxide. This high activity has been related to the composition of the sludge (as it contains active metal oxides such as oxides of iron and manganese) and to the porous structure (leading to a reasonably high surface area). Moreover, it can be also used as a support for platinum, showing comparable (or even higher) catalytic activity than a similar platinum catalyst supported on conventional γ-alumina. This work presents a double environmental perspective since the material employed as a catalyst is a waste sludge and the catalytic reaction studied deals about the elimination of pollutants.

Keywords: Platinum; Purification of water; Sludge; Support; VOCs.