Multi-ionic effects on energy production based on double layer expansion by salinity exchange
Abstract
The edited version of the manuscript can be obtained at: Delgado et al., J. Colloid Interface Science (2014); DOI http://dx.doi.org/10.1016/j.jcis.2014.08.009 ; It has been recently shown that the free energy change upon salinity mixing in river mouths can be harvested taking advantage of the fact that the capacitance of charged solid/liquid interfaces (electrical double layers, EDLs) depends strongly on the ionic composition of the liquid medium. This has led to a new generation of techniques called Capmix technologies, one of them (CDLE or Capacitive energy extraction based on DL Expansion) based precisely on such dependence. Despite the solution composition playing a crucial role on the whole process, most of the research carried out so far has mainly focused on pure sodium chloride solutions. However, the effect of other species usually present in river and sea waters should be considered both theoretically and experimentally in order to succeed in optimizing a future device. In this paper, we analyse solutions of a more realistic composition from two points of view. Firstly, we find both experimentally and theoretically that the presence of ions other than sodium and chloride, even at low concentrations, may lead to a lower energy extraction in the process. Secondly, we experimentally consider the possible effects of other materials usually dispersed in natural water (mineral particles, microbes, shells, pollutants) by checking their accumulation in the carbon films used, after being exposed for a long period to natural sea water during CDLE cycles. ; Universidad de Granada. Departamento de Física Aplicada ; The research leading to these results received funding from the European Union 7th Framework Programme (FP7/2007-2013) under agreement No. 256868. Financial support from Junta de Andalucia (Project PE2012-FQM 694) and MINECO (Project FIS2013-4766-C3-1-R) is also acknowledged. One of us, M.M.F., is grateful to the University of Granada for her FPU grant.
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