Nanotechnologies (NT) use particles in the range 1-100 nm, and these nanoparticles (NP) have distinctive characteristics compared with their bulk counterparts. For this reason, the use of NP has significantly expanded in a great diversity of industrial sectors and research groups in order to enhance their actual processes or to develop new applications. A description of the use of NT in environmental applications is presented in this review. Specifically, important advances focused on the development of new strategies to produce clean energy (electricity and hydrogen) and the development of analytical sensors using NP, are described. In addition, the review describes applications of NT during the removal of pollutants from water using physicochemical and/or biologicalmethods. (C) 2011 Society of Chemical Industry