BRITA have been asked about filtering alcohol before and our understanding (although we do not run tests on this) is that there may be a very slight reduction in alcohol content if filtered through a BRITA cartridge but the ion exchange resin will not have an effect on alcohol.
The ion exchange resin selectively removes certain metal ions such as copper, lead, calcium and aluminium from the water and as a weak acid cation exchanger ions removed are replaced with hydrogen ions, which combine with other ions and eventually form H20 and C02.
I hope this answers your query.
Yours sincerely
Rachel Laycock
BRITACare Manager
Brita Water Filter Systems Ltd
http://www.stillsmart.co.uk/general-info/filtering-spirits-using-brita-type-filters/
Please see previous post on this thread.