thiourea and sodium-sulfide

This work compares the performance of stabilizing Pb by Sodium sulfide (Na2S), Sodium phosphate (Na3PO4), thiourea (H2NCSNH2), and mercapto functionalized dendrimer (TEPA-SNa) in MSWI fly ash, including leaching toxicity analysis and leaching behavior analysis, as a function of pH. The leaching toxicity in fly ash indicated that leaching value of Pb stabilized by Na2S, Na3PO4, and H2NCSNH2 has remained higher than the limit value (0.25mg/L) with a dosage of 10%. However, the leaching value associated with TEPA-SNa approaches zero at a dosage of 3%. The effective leaching test results showed the leaching amount of Pb stabilized by TEPA-SNa with a dosage of 3% to be 3.58 mg/kg less than the maximum allowable amount of leaching (5mg/kg), but the amount of Pb leached by Na2S, Na3PO4, and H2NCSNH2 was much higher than 5mg/kg. The leaching behavior of Pb as a function of pH showed that the leaching concentration of Pb stabilized by TEPA-SNa can approach zero at a dosage of 5% no matter how the pH changes. In summary, TEPA-SNa can interact with Pb(2+) in the acid-base environment and effectively immobilize Pb(2+) in fly ash in the long term.

Topics: Chelating Agents; Coal Ash; Dendrimers; Incineration; Lead; Phosphates; Sulfhydryl Compounds; Sulfides; Thiourea