Selective Removal of Monovalent Ions from Artificial Urine by Electrodialysis 2005-01-3110
The intent of this study was to investigate whether monovalent ions can be selectively removed from synthetic urine and real urine using electrodialysis with monovalent ion selective membranes.
All experiments were performed in batch mode, at constant voltage. On-line data acquisition was performed using Mefias® software, developed by Vito. To investigate the effect of voltage, synthetic urine was desalinated at 9V, 16V, 26V and 40V. The results show that monovalent ions can be removed almost completely from synthetic urine by the selected membranes at all voltages tested. In all experiments the unwanted removal of the multivalent ions is low but shows a ‘breakthrough’ when the removal of monovalent ions approaches 100%. Therefore it is important to stop desalination before this ‘breakthrough’ occurs. The unwanted removal of multivalent ions from synthetic urine is higher at 26 and 40V than at the lower voltages, therefore the lower voltages are preferred.
Experiments with real urine were performed to compare the results with synthetic urine. The desalination of real urine was much slower than for synthetic urine. This might be due to the presence of organic compounds in urine that can block the membranes. Real urine was pretreated with activated carbon to remove the organic compounds and was then desalinated. After activated carbon pretreatment, desalination was much faster, supporting the hypothesis that organic compounds block the membranes.