Abstract
ABSTRACT
Effects of polymer latex on properties of solidified wastes are presented in this paper. A mercury-containing sludge was selected and solidified by three cementitious binders with or without the addition of a polymer latex. Properties of the solidified waste were then investigated by scanning electron microscopy (SEM), freezing and thawing test, wetting and drying test, unconfined compressive strength measurements, and toxicity characteristic leaching procedure (TCLP).
As expected, no matter how the sludge was solidified, the unconfined compressive strength for the solidified specimen with an age of 28 days was found to be greater than those of with an age of 7 days or 3 days. Also, the addition of polymer latex would result in a greater unconfined compressive strength for solidified specimens than those of without polymer latex addition. An increase of polymer latex (up to 3 wt% in this study) would increase the strength of the solidified specimen. Another positive effect of polymer latex addition was evidenced from a much lower mercury concentration of the TCLP leachate for the specimen solidified by any of the polymer latex modified cementitious binders. The positive effects of polymer latex are due to the formation of a crosslinked structure in the monolith, observed by SEM, resulting from the polymer latex modified solidification.
For three binders tested, the sludge treatment agent(STA II) outperformed ASTM Type I and Type II portland cements in terms of the unconfined compressive strength and mercury concentration of the TCLP leachate, regardless of whether the solidified specimens were subjected to any of the aforementioned durability tests.
Results of the freezing and thawing test showed that all solidified specimens without polymer latex addition were cracked down during the test. Those specimens solidified with polymer latex addition, although not broken during the test, were found to be degraded as evidenced by the unconfined compressive strength and TCLP mercury concentration measurements. Similar findings were also observed for the wetting and drying test.
Economic feasibility of using each kind of binders with or without polymer latex modification for a solidification plant with a treatment capacity of 100 metric tons per day was also briefly discussed.
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