Thermal treatment of heavy metal in incinerator fly ashes

Stabilizing Cr species in incinerator fly ashes with/without kaolin addition through a firing process: a molecular study on heated Cr

Cr speciation in Cr-sorbing washed incinerator fly ash (IFA) after heating up to 1100°C is temperature dependent. Higher temperature leads to a greater level of chemical reduction of Cr(VI) that is considerably more toxic than Cr(III). Most Cr(VI) sorbed washed IFA is effectively transformed into Cr(III) after heating to 1100°C for 2 h, as indicated by the disappearance of hexavalent pre-edge peak of Cr K-edge X-ray absorption near edge structure (XANES) spectrum. After heating the Cr-sorbing IFA to 100°C and 500°C for 2 h, water-soluble CaCrO₄ is determined to be the principal Cr species due to the chemical reaction between the sorbed Cr(VI) and CaO components of washed fly ash, based on the comparison between sample and reference XANES spectra. Replacing half of the washed fly ash with kaolin could effectively reduce all Cr(VI) after heating to ≧ 900°C for 2 h.

Mechanical and Thermal Propertiesof Fly Ash/Reclaimed Rubber Powder Composites Improved by KH-550 Coupling Agent

Fly ash (FA) is utilized as a filler to reinforce reclaimed rubber powder (RP) composites by using a coupling agent. FA content is varied between 10 and 35 phr. The optimal formulation of FA/RP composites and experimental process variables were determined by measuring mechanical and thermal properties. A study of compatibility and cross-linking by SEM and IR shows that FA/RP composites offer superior mechanical and thermal properties when the accelerator (M) and stearic acid (SA) are added first, then mixed with sulfur and dicumyl peroxide (DCP), and finally r-Aminopropyltriethoxysilane (KH-550). The mass ratio of the FA/RP composites is 25/100, and the cure condition is 145°C for 40 min under 9 MPa. The results indicate that FA is an excellent filler and can be used as a silica replacement for reclaimed rubber powder composites.