Electrochemical dissolution of aluminium in electrocoagulation experiments

Six experiments are presented to highlight important features of aluminium dissolution when used in electrocoagulation procedure employed to remove oily contaminations from water. First, using a common oil-in-water emulsion: diluted milk, we show that the electrochemically generated coagulant ions are active only in the first few seconds following their generation-hence, the electrocoagulation cells' construction should promote the mixing of the nascent Al colloid with the water phase. For this reason, the use of the narrow-gap cells is suggested. Second, in experiments with Al-Al electrode pairs and dilute, neutral, unbuffered, aqueous solutions we (i) estimate the maximum amount of Al dissolution on the cathode and (ii) show how the rate of Al dissolution changes with frequency if the cell voltage polarity is alternating.