垃圾焚化廠底渣重金屬脫附性之探討

The Desorption Behavior of Heavy Metals in Bottom Ashes of Incineration Plants

本計畫係選取產自中、南部各兩座垃圾焚化廠之底渣再利用產品做為實驗材料，先以王水消化法分析重金屬之含量，再以0.01N 氯化鈣進行脫附性試驗，藉以評析重金屬之安定性與釋出行為。重金屬全量之測值指出，各樣品中之重金屬含量以鋅最高，其次依序為銅、鉛、鎳、鉻、砷、鎘、汞，而超過土壤污染管制標準者主要為鋅、銅、鎳。重金屬之脫附試驗結果發現，脫附比例以鎘最高，鋅次之。而各元素之累積脫附量皆甚低，且皆遠低於土壤污染管制標準。此外，累積脫附曲線之型態多數呈現初期累積脫附量較大，其後釋出量趨緩之現象。由此可知，重金屬因高溫熔融而包埋於底渣中，不易在自然環境條件下釋出，故短期釋出量不致造成土壤污染。

Bottom ashes, collected from four incineration plants located in Southern and Central Taiwan, were used to study their heavy-metal contents and desorption behavior in order to evaluate the stability and release mechanism of heavy metals in the ashes. The results showed that zinc was the most abundant element in the ashes. In descending order, other heavy metal contents were Cu, Pb, Ni, Cr, As, Cd, and Hg. The concentrations of Zn, Cu, Ni were found to be higher than those of soil pollution control standards. Based on the results of desorption experiments, Cd and Zn were the most easily releasable elements. However, the accumulated desorption amounts of all heavy metals were found to be much lower than those of soil pollution control standards. In addition, the accumulated desorption curves indicated that most heavy metals were extracted easily in the beginning intervals and slowly afterwards. These results showed clearly that the heavy metals were buried in the ashes during combustion and thus were hardly to release in the soil environment.