Separational purification of nitrate from inedible biomass leachate by electrodialysis: fouling effect

Abstract

The removal of nitrate and potassium from wheat leachate solution was studied using an electrolytic cell in batch recirculation mode for use in advance life support systems (ALSS). The ALSS or CELSS (Controlled Ecological Life Support System) are systems developed to provide all the required basic human needs for long-term space missions. High nitrate and potassium removals were obtained at 5, 6, 7, 8 and 9 volts. Anions removals over 90% were obtained after 200 minutes of operation at these constant applied voltages. A maximum nitrate and potassium removal of 100 % and 99.82%, respectively, was obtained at 9 volts. During the electrolytic cell operation, the removal of monovalent anions was found to be higher than divalent and trivalent ones. This is different to the selectivity of monovalent and divalent cations found when use cation-exchange membrane, the removal of monovalent and divalent cations was very similar. Electrical resistance measurements showed that under constant applied voltage, anion membrane fouling decreased with increasing voltage. This is due to the mobility of anion organic molecules at high voltages. It was also found that the cation membrane fouling increased with applied voltage and that, at low voltages, the fouling was absent. It is postulated that these results from a low concentration of cation organic molecules and to the high molecular weight of this organics that limits their mobility through of solution.