Stabilization/solidification (S/S) of mercury-containing wastes using reactivated carbon and Portland cement

Stabilization/solidification (S/S) of mercury-containing solid wastes using activated carbon and cement was investigated in this study. The activated carbon used in the study was a powder reactivated carbon (PAC). The effect of sulfur-treatment of the PAC was also studied. It was found that PAC was effective in stabilizing Hg in the waste surrogate. Pretreatment of the PAC by soaking it in CS(2) significantly improved the mercury adsorption capacity of the PAC. The adsorption equilibrium was reached within 24h. The optimum pH for the reaction was within the range of 5.0-5.5. After mercury stabilization by adsorption on the reactivated carbon, the Hg waste surrogate was mixed with Portland cement for solidification. Surrogates with up to 1000 mg/kg Hg were stabilized and solidified well enough to pass the TCLP test. The adsorption of mercury by reactivated carbon was in accordance with the Freundlich isotherm. Cement solidification of reactivated carbon-stabilized surrogates, significantly reduced the often-reported interference by chloride ions, by forming a barrier outside of the carbon particles. The S/S process using reactivated carbon and cement is an effective and economical technology for treating and disposing mercury-containing solid wastes.