I mean basically you're describing a solar pond (https://en.wikipedia.org/wiki/Solar_pond) or salt evaporation pond (https://en.wikipedia.org/wiki/Salt_evaporation_pond). There isn't an easy way to recover the evaporated water from that process; you would effectively have to build an artificial enclosed environment and it wouldn't work as fast as exposure to the elements. Basically you would need a still (as in for alcohol) the size of 20 football fields. But sun power wouldn't be enough to power it fast enough to be practical. Maybe if you moved it into outer space...