Thermal treatments are the most used methods to remediate contaminated solids. However, they may seriously damage the otherwise recoverable matrices, especially when mild operating conditions cannot be used. Microwaves recently raised as a powerful tool in industrial engineering for their ability, among other advantages, to offer a selected heating, thus allowing to treat and remove only the undesired components of a matrix. This work approaches the microwave assisted thermal treatments of waste from a physical-chemical point of view. Two recovering operations have been performed, respectively, on a soil contaminated by volatile organic compounds and on a ceramic filter spoiled by soot, using two specially designed prototypes, both realized on pre-pilot scale. The heat and mass transfer balances have then been analyzed in their more general form, and terms related to the use of microwaves outlined. Solutions of the differential equations have been applied to interpret the effects of microwaves on rate and efficiency of the remediation processes. (C) 2011 Elsevier B.V. All rights reserved.