Wet Reclamation for Improving Properties of Waste Silica Sand from Foundry

Dewi Idamayanti, Ari Siswanto, R. Widodo, Aldy Budhi Iskandar

Metal casting commonly uses silica sand with water glass as a binder for mold and core. Water glass binder that overlays grain sand was harden by CO2 gas to form silicate bonding.  The   waste silica sand was not able to be  reused as mold and core because its properties changed due to high temperature exposure during casting process that converted silicate bonding become refractory compound. Recently, several methods were developed to recycle  waste silica sand. The methods recommended were mechanical, thermal and wet methods. In this research, wet method has been selected to reclaime  waste  silica sand due to good properties result.  The research methodology involved several processes. Lumps of  waste  silica sand was crushed mechanically then mixed with water at the ratio of 1  : 1 by weight and  stirred at the speed of 1400 RPM. The mixing and washing steps have been done gradually until five times. The properties of reclaimed silica sand resulted sintering point over 1300oC, loss on ignition 0.5%, grain fineness number 76.6, and dust content 0.42. Its physical properties comply standard specification of silica sand. The reclaimed sand after fifth washing was observed under SEM and showed that most of sand grain could be separated and it had the angular shape with medium sphericity.