Playsand is silica based...it has no silicone. Any silica based sand can/will release silicates into the water and they can cause a diatom bloom. Diatoms feed on silicates.
Your best bet is just buying dry aragonite (CaribSea brand) sand from your LFS
. You won't have to worry about silicates, but also keep in mind aragonite sand DOES NOT buffer anything....unless your pH is around 7.4 where the aragonite will start to dissolve and buffer the water. Then again, if your water has that low of pH, chances are nothing is alive in the tank.