Granite desalination using electromigration. Influence of type of granite and saline contaminant

Electro-desalination of Buildings Suffering from Salt Weathering

“…To investigate the influence from the porosity on the electrodesalination NaCl or KCl removal are relevant, as these chlorides are highly soluble and the process is thus not determined by solubility in these laboratory contaminated stones. The removal of chloride has approached 100 % in different natural stones with different porosities ranging from Albero granite 3.9 % and Rodas granite 5.9 % (Feijoo et al 2013), to Posta and Cotta sandstones ) with porosities of 22 % and 23 % (Sidel 2010) and no limitations from the porosity on the high removal percentage was seen.…”

“…Electro-desalination (with buffering poultice at the electrodes) of bricks and natural stones contaminated with chlorides and nitrates have been shown very successful with removal of 99-100 %, e.g., Cl removal from yellow and red bricks Skibsted et al 2013), posta and cotta sandstones , and granite (Feijoo et al 2013). Chlorides and nitrates are generally highly soluble, whereas sulfates are less soluble.…”

“…So this investigation did not show the unwanted changes when using poultice, but the topic should be investigated further to make sure that there will be no unacceptable and irreversible changes. Feijoo et al (2013) investigated possible color changes in two different granites caused by electro-desalination, and they identified slight changes, which tough were associated with traces of kaolin from the poultice rather than changes in color of the granite itself.…”

“…Wet sponges were replaced regularly (Kamran et al 2012a, b). Feijoo et al (2013) used a combination of wet sponges and CaCO 3 -rich poultice at the anode and kaolinite and sponge at the cathode. In Ottosen and R€ orig-Dalgaard (2007) a system with electrolyte solutions and ion exchange membranes were used to avoid pH changes in the brick and the brick pH was only slightly decreased, but the system was too difficult to operate, as from the compartment next to the brick the liquid was lost either from capillary suction into the brick or leaking between the brick and electrode unit.…”

Electrochemical desalination of historic Portuguese tiles – Removal of chlorides, nitrates and sulfates

“…Electrochemical desalination of other matrices has also recently been tested: baked clay bricks [6][7][8][9][10], sandstones [11][12][13] and granite [14]. These studies have mainly focused on electrochemical desalination of single stones representing somewhat homogeneous matrices, but in relation to tiles, the salt crystallization under the glaze is of major concern.…”