ORIGINAL PAPER Removal of lead from aqueous solutions by electrocoagulation: isotherm, kinetics and thermodynamic studies R. Kamaraj • P. Ganesan • S. Vasudevan Received: 7 September 2012 / Revised: 27 August 2013 / Accepted: 24 November 2013 / Published online: 10 December 2013 Ó Islamic Azad University (IAU) 2013 Abstract The present study provides an electrocoagula- tion process for the removal of lead from water using magnesium and galvanized iron as anode and cathode, respectively. The various operating parameters such as the effect of initial pH, current density, electrode configuration, inter-electrode distance, co-existing ions and temperature on the removal efficiency of lead were studied. The results showed that the maximum removal efficiency of 99.3 % at a pH of 7.0 was achieved at a current density 0.8 A/dm 2 with an energy consumption of 0.72 kWh/m 3 . The exper- imental data were fitted with several adsorption isotherm models to describe the electrocoagulation process. The adsorption of lead preferably fitting the Langmuir adsorp- tion isotherm suggests monolayer coverage of adsorbed molecules. In addition, the adsorption kinetic studies showed that the electrocoagulation process was best described using the second-order kinetic model at various current densities. Thermodynamic parameters, including the Gibbs free energy, enthalpy and entropy, indicated that the lead adsorption of water on magnesium hydroxides was feasible, spontaneous and endothermic. Keywords Electrocoagulation  Heavy metal  Adsorption  Kinetics  Thermodynamics Introduction Heavy metal pollution is an important environmental problem in the aqueous system originated from different sources. Mainly this heavy metal pollution exists in many industrial wastewaters, such as mining operations, metal finishing and production industries such as fertilizer, paints, pigments, battery, tannery, household plumbing materials, water service lines, atomic energy installation, leather- working, photography and salvages yards (Argun et al. 2007; Sing et al. 2006; Heil et al. 1999). Various metals associated with these activities are lead, cadmium, mer- cury, copper, chromium, etc. Heavy metals are not biode- gradable and tend to accumulate into living organisms, causing various diseases and other problems. This heavy metal is also known carcinogen. Lead is an enzyme inhibitor, and human intake of lead causes disruption of the biosynthesis of hemoglobin, rise in blood pressure, kidney damage, miscarriages and abortions, brain damage and diminished learning abilities of children. According to the WHO, the maximum permissible limit (MPL) of lead in drinking water is 0.05 mg/L (WHO 2009). Hence, proper treatment of industrial wastewaters that are releasing lead into the aquatic and land systems is very important. The common methods for removing lead from water includes chemical precipitation (Matlock et al. 2001), ion exchange (Inglezakis et al. 2007), membrane separation, flotation, biosorption (Nurbas Nourbakhsh et al. 2002; Gupta and Ali 2004) and adsorption (Mohan and Chander 2006; Gupta and Sharma 2002). At present, chemical treatments are not used due to disadvantages such as high costs of maintenance, problems of sludge handling and its disposal, and neutralization of effluent. Recent research has demonstrated that electrocoagula- tion offers an attractive alternative to aforementioned Electronic supplementary material The online version of this article (doi:10.1007/s13762-013-0457-z) contains supplementary material, which is available to authorized users. R. Kamaraj  P. Ganesan  S. Vasudevan (&) CSIR, Central Electrochemical Research Institute, Karaikudi 630 006, India e-mail: vasudevan65@gmail.com 123 Int. J. Environ. Sci. Technol. (2015) 12:683–692 DOI 10.1007/s13762-013-0457-z