Removal of Tetramethylammonium Hydroxide From Solution Using Ion Exchange

Ion exchange is used to remove tetramethylammonium hydroxide from an aqueous solution. Both strong acid cation (SAC) and weak acid cation (WAC) exchange resins show excellent uptake of the TMA⁺ ion. The pseudo-second-order kinetic model fits the data of uptake rate well. When using an SAC exchange resin, the pH does not affect the uptake efficiency, while that of the WAC exchange resin is strongly affected by the pH. Regeneration experiments show excellent performance of resins after five cycles. The selectivity coefficient of TMA⁺ over H⁺ for SAC is calculated as 5.16, while for WAC, in the bulk solution, the selectivity coefficient is notably lower (6.45×10^-4). The presence of competing ions interfere with the TMA⁺ uptake, of which Mg²⁺ has the most notable effect. The ion exchange model is applied to obtain resin selectivity over the TMA⁺ ion as well.