2.2. Preparationofsodiumsilicate
First, ricehuskwastreatedwithdilutedHClinawater
bath at75 1C for4htoremovemetallicimpurities.The
suspensionwasfilteredandthesolidresiduewasrepeat-
edly washedwithdistilledwateruntilthefiltratewasfree
of theacid(pHoffiltrate 7). Theresiduewasthendried
at 110 1C for12hinanoven.Aknownamountofdried
rice huskwasaddedtoaTeflonflaskcontaining10wt%
NaOHandboiledat90 1C for1hwithconstantstirring.
Then, themixturewassubsequentlycooledatroom
temperatureandfilteredtoobtainsodiumsilicate(SS)
with aspecificgravityof1.13.