Metals involved in fly ash
Fly ash (FA2), taken from industrial waste incinerator, contains higher dioxins than FA1, taken from a municipal waste incinerator, but much better hydrodechlorination/detoxification for FA2 com- pared to FA1 under same conditions (Method A) for decomposi- tion: Dechlorination percentages of FA1 and FA2 were 54% and 62%, respectively. This phenomenon might be due to reason that FA2 has higher concentration of metals as compared to FA1. In our previous studies (Ghaffar and Tabata, 2009–2010) we have proved that metals contents of fly ash had adverse effects on dechlorination of organic chlorides at high temperature but at low temperature metals enhanced catalytic potential of fly ash for dechlorination by stabilizing the free chloride ions. We deter- mined eluted toxic metals by treating fly ash based on Japanese Environmental Standard Method (JIS K0102), using 1.0 M HCl. The results are given in Table 3. FA2 contains high concentrations of metals. Especially Cu, Fe and Pb are involved in FA2 at high con- centration compared to FA1. The toxic metal concentrations are less than values defined by the environmental standard of Japan. Copper and iron have the catalytic potential of metals in fly ash to decompose the dioxins and PCBs and ultimately reduced the toxicity. Table 2 supports the enhanced hydrodechlorination of PCDDs, PCDFs and PCBs in FA2. Interestingly the elution of toxic metals of lead and chromium from aqueous solution of pH 5.8– 6.3 (JIS K0102-55.2) was completely suppressed after the present treatment using the mixture of sulfur and calcium hydroxide.