Kinetics of the thermal desorption of mercury from spent mercury chloride catalysts were investigated using non-isothermal thermal analysis technique. Complex mercury species absorbed on waste catalysts were revealed by sequential extraction procedure. A scheme of six reactions was applied to elucidate mercury desorption kinetics. Activation energy estimated by model-free isoconversional methods is a slightly increasing function of conversion, implying a variation in the mechanism controlling mercury desorption. Average value of apparent activation energy (116.32 kJ/mol calculated by isoconversional Starink method was used to determine reaction mechanism using model-fitting and z (alpha) master method. One dimensional diffusion appears to govern mercury desorption process in the conversion range of 10%-40%, and then the reaction kinetic is controlled by two and three dimensional diffusion at greater conversion. (C) 2016 Elsevier B.V. All rights reserved.