A chemically modified polysulfone (SDC-PSF) containing N-methyl-N-carboxymethyl dithiocarbamate groups has been prepared by the reaction of chloromethylated polysulfone with sodium N-methyl-N-carboxymethyl dithiocarbamate (SDC) in dimethylformamide. Asymmetric SDC-PSF membranes prepared were brought to reverse osmosis tests at ∆P= 10 kg/cm2 and 25°C with 1000 ppm NaCl solution and feed solutions containing some low molecular organic solutes. Triethylammonium polysulfone, TEA-PSF, membranes were also prepared and tested. The SDC-PSF membranes showed higher water flux than the TEA-PSF membranes. This is attributed to the bulky hydrophilic group of the SDC. The SDC-PSF membranes were modified by copper chelation or by irradiation with ultraviolet light. These modified SDC-PSF membranes showed higher rejection for isopropanol, sucrose and β-eyclodextrin, while the water flux decreased only 10%compared with that the of original SDC-PSF membranes. An equation for salt rejection in reverse osmosis operation was derived from the assumption of the Donnan equilibrium. Experimental results of salt rejection were compared with theoretical values calculated with effective fixed charge densities obtained from membrane potential experiments and with thermodynamic partition coefficients from sorption-desorption experiments that were measured in homogeneous SDS-PSF membranes.
- Donnan Potential
- Membrane Potential
- N-Methyl-N-carboxymethyl Dithiocarbamate
- Partition Coefficient
- Reverse Osmosis