Effect of chemical and thermal activations on the properties of rice husk ash-based solidified waste

Strength development,leachability and microstructure of heavy metals from the solidified waste using synthesis rice husk ash(Srha)and lime blended at the weight ratio of 1:1 were used as binders.The heavy metal-containing sludge was used at the level of 0 wt.%,30 wt.%,and 50 wt.% dry weight,respectively.The sample specimens with and without 1.5 wt.% of sodium silicate(SiO2/Na2O＝1.O) were cured under the ambient condition and elevated temperature curing at 50℃ for 24 hr.Experimental results showed that the introduction of sodium silicate solution and elevated temperature curing to Srha-based solidified waste containing 30 wt.% of heavy metal sludge gave one day strength of 20 kg/cm2 compared to 0.9kg/cm2 for the control sample.XRD patterns indicated that most metal-sulfides present in the sludge were appeared in the solidified waste and SEM coupled with EDX techniques reveal these metal-sulfide particles were trapped within the lime-Srha matrices.In addition,cumulative leaching behavior by tank test(EA NEN 7375:2004)showed that solidified waste containing up to 30 wt.% of heavy metal sludge was suitable to dispose in a secured landfill.