One approach would be some kind of membrane process like ultra- or nanofiltration.The questions to answer first are:* How much water do you want to process?* Do you want the soap or the water?* What...
soaps are soluble in water because the are bases and most of the bases are alkalis, which are soluble in water. That is why, only some soaps like bathing soaps are soluble in water and not all soaps...