Once-used $CO_2$-silicate bonded sand from domestic foundry is mostly discarded in a reclaimed land because of its bad collapsibility and reproduction properties. So this causes serious environmental problem. We can get 82% recovery of silica from used sand by scrubbing reclamation process in this research. When we repeat the reclamation-recycling of the foundry sand, artificial silica sand is broken down below 2-cycles, but natural silica sand does not destroyed when used repeatedly more than 10-cycles and have a good property of recycling with little change of its size.