EVALUATING SUITABLE CHELATING AGENTS FOR Q STAGE IN TCF BLEACHING OF WHEAT STRAW ALKALINE PULPS

Abstract

The aim of this study was to determine an appropriate chelating agent for Q stage in the TCF bleaching sequence of soda-oxygen, soda, soda-anthraquinone and alkaline-sulfite wheat straw pulps prior to P bleaching stage. In order to study the possible effect of chelating agents, three different chelating agents (EDTA, DTPA and DTMPA) were used. To evaluate the impact of transition metal ions on P stage, the residual Mn, Fe and Cu ion concentrations were determined with atomic absorption spectrometry. Ash and silica contents of pulps have been determined for each chelating agent, separately. FTIR-ATR spectroscopy was used to demonstrate the bleaching effect. The results showed that the most appropriate chelating agents varied depending on the type of pulp. The best chelating effect was achieved with DTMPA for soda-oxygen pulp, EDTA for both soda and alkaline-sulfite pulps, and DTPA for soda-anthraquinone pulp.