Question:
Existing water purification technology, such as reverse osmosis , ion exchange, and electrodialysis, all generate wastewater. Any wastewater is of course undesirable.

Experiment described below was to generate a solid waste product from a solute/solventmixture, in this case an aqueous solution of calcium sulfate

Gypsum, or calcium sulfate, is slightly soluble in water. A recently allowed patent USS.N. 08/541,880 , titled non- fouling through capacitor demonstrates how slightlysoluble salts, such as gypsum, can be purified from solution as a solid. To do this,first purify an amount of a feed gypsum solution with a flow through capacitor, the sameas with any other s When you are ready to discharge the capacitor and therebyrelease the absorbed salts, discharge the capacitor into another volume of saturatedgypsum solution that has been pumped back into the capacitor. This supersaturates thesolution. Remove and save the supersaturated waste solution . Purify another amount ofthe gypsum containing feed solution. When ready to discharge again, reuse the savedsupersaturated waste by pumping this back into the capacitor. Repeat the process ofdischarging to capacitor into the supersaturated solution. This supersaturates thesolution even more. You will notice that the conductive of the supersaturated solutionno longer rises linearly, but rises less steeply. It is possible to supersaturate thegypsum solution over ten percent, perhaps over 25%. When you have finished purifyingthe feed gypsum solution, take the supersaturated waste that you have saved and triggerprecipitation of solid crystals. This can be done by apply a temperature change,agitation, sound, or ant other means. Crystals of gypsum come out of solution and can beremoved from the now simply saturated solution by decanting or filtration. The saturatedwaste solution can now be re-used in subsequent discharge cycles.

Answer: Problem;It would be useful if this same technique could be applied to salts normally highlysoluble in aqueous solutions as well as slightly soluble salts. Such highly solublesalts would include, but not be limited to , Chlorides, such as sodium, potassium ,lithium, calcium, magnesium, Nitrates, such as ammonium, sodium, calcium, and any otherhighly soluble s

It is difficult to apply this technique in purely aqueous solutions of highly solublesalts , because the high concentration required to supersaturate such a highly solublesalt solution would be so high as to contaminate the capacitor with residual deadvolume waste that wets the capacitor. This would lead to inefficiency due tore-purification of this residual waste during subsequent charge cycles.

Solution to this problem;

For the supersaturated waste solution, select any solvent whereby the salts to be purified are only slightly soluble. These might include but not be limited toalcohols, ketones, acetone, ammonia,acids, bases, dimethyl formamide, aliphatichydrocarbons,and aromatic hydrocarbons. These would also include but not be limited tomixtures of the above with themselves and with water. Such mixtures andaqueous mixturescould be selectred such that the salts to be purified are only slightly soluble. Mixtures were the salts are insoluble, decompose, or react chemically can also be used.

The solvents used to recover the solid percipitate are of course saved andreused in subsequent discharge cycles, by being pumped back into thecapacitor, exactly as in the aqeuous calcium sulfate (gypsum) example.

The procedures and methods as the same as in the above mentioned allowedpatent. The only difference is, non aqueous solvents are used to adjust thesolubility of the waste solute solution to a desired level of slight solubility.Slight solubility would preferably be anything under 100grams/cc