Neutralization dialysis is a deionization method based on a Donnan dialysis. Weak acids and bases, even urea and alcohols, were also removed by this method, and their transport rates increased with the decrease of their dissociation constants and with the increase of the concentrations of acid and base solutions in the neutralization system. Aqueous silica, which is a typical inorganic weak acid and abundant in surface water, was also effectively removed by this method. Therefore, tap water was effectively deionized to be pure water with a resistivity of 15 M Omega cm and a silica concentration ofless than 10 ppb as SiO2 and the neutralization dialysis was proven to be an effective deionization method.