抄録
Hydrogen peroxide is one of the most important chemicals used in deinking of waste paper and bleaching of mechanical pulp. Environmental restrictions on the use of chlorine-based bleaching techniques are forcing the use of hydrogen peroxide in chemical-pulp bleaching. Therefore a demand for the on-site production of hydrogen peroxide is increasing in the pulp and paper industry. The trickle-bed electrolyzer was developed with a cation-exchange membrane, which could prevent the loss of current efficiency (back-migration of the perhydroxy ion through separator), for the electrochemical production of the hydrogen peroxide. And in order to verify the long-term performance of the electrolyzer, the operational condition of the electrolyzer was investigated. Although the cation-exchange membrane was fouled during continuous operation, we found that an addition of an ethylenediaminetetra-acetic acid (EDTA) salt into the anolyte improved the current efficiency and prevent fouling of the ion-exchange membrane. Anolyte recycling was carried out for a practical usage of the anolyte. The cation-exchange membrane was fouled with metallic compounds from make-up NaOH solution when anolyte was recycled 47 times. These metallic compounds were effectively eliminated from the make-up solution by filtration treatment after mixing with magnesium sulfate. It was also clarified that 10% anolyte purge was effective to keep the lower metal concentration from the critical level. The possibility of the trickle-bed electrolyzer is discussed for the on-site electrochemical production of the hydrogen peroxide.
