论文部分内容阅读
The solidification / stabilization (S/S) of Cr(Ⅵ) by alkali-activated slag binder (AAS) with water glass as activator was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) in the present study.X-ray diffraction analysis and the determination of reduction rate of Cr(Ⅵ) to Cr(Ⅲ) were done to investigate the S/S mechanism.The experimental results showed that the leachability of Cr(Ⅵ) was dependent on the dosage and modulus of water glass and the pH of extracted medium.In the TCLP procedure, the Cr(Ⅵ) (concentration up to 1% by mass of slag) was well solidified/stabilized in AAS with the leachability below the regulatory limit.Part of Cr(Ⅵ) was reduced to Cr(Ⅲ) in the leaching process with decreased pH, Whereas, the Cr(Ⅲ) was severely leached when the pH was lower than 7 that is too low to precipitation for Cr(Ⅲ).It was revealed the reduction of Cr(Ⅵ) to Cr(Ⅲ) in AAS was crucial for S/S of Cr(Ⅵ).XRD analysis indicated that Cr contained phases in AAS solidified waste were amorphous rather than crystalline.The hydrotalcite-like phase formed in AAS hydration maybe another mechanism for fixation of Cr(Ⅵ) by anion exchange.In addition,compacted structure also played an important role in Cr retention by physical encapsulation.Overall, AAS provided a bright prospect as an effective binder in the S/S of Cr(Ⅵ).