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1764635 
Journal Article 
Effects of alternating and direct current in electrocoagulation process on the removal of fluoride from water 
Vasudevan, S; Kannan, BS; Lakshmi, J; Mohanraj, S; Sozhan, G 
2011 
1 
Journal of Chemical Technology and Biotechnology
ISSN: 0142-0356 
86 
3 
428-436 
WOS:000287259400014 
BACKGROUND: When direct current (DC) is used in
electrocoagulation processes, an impermeable oxide layer may form on the cathode and corrosion of
the anode may occur due to oxidation. This prevents effective current transfer between the anode
and cathode, so the efficiency of the electrocoagulation process declines. These disadvantages of
DC have been reduced by adopting alternating current (AC). The main objective of this study is to
investigate the effects of AC and DC on the removal of fluoride from water using an aluminum
alloy as anode and cathode. RESULTS: Results showed that removal efficiencies of 93 and 91.5%
with energy consumption of 1.883 and 2.541 kWh kL(-1) was achieved at a current density of 1.0 A
dm(-2) and pH 7.0 using an aluminum alloy as electrodes using AC and DC, respectively. For both
AC and DC, the adsorption of fluoride fitted the Langmuir adsorption isotherm. The adsorption
process follows second-order kinetics and temperature studies showed that adsorption was
exothermic and spontaneous in nature. CONCLUSIONS: The aluminum hydroxide generated in the cell
removed the fluoride present in the water and reduced it to a permissible level thus making it
drinkable. It is concluded that an alternating current prevents passivation of the aluminum anode
during electrocoagulation and avoids the additional energy wasted due to the resistance of the
aluminum oxide film formed on the anode surface. (C) 2010 Society of Chemical Industry 
electrocoagulation; alternating/direct current; fluoride removal; adsorption kinetics; isotherms