Solidification and leaching behaviours of Cr6+ in sludge ceramsite.
Making lightweight ceramsite with sewage sludge is a new effective approach for disposal of sludge. However, there is a concern as to whether the heavy metals such as Cr6+ in sewage sludge can be solidified in ceramsite after sintering. The configuration of Cr6+ in ceramsite was analyzed by X-ray diffraction (XRD) and leaching tests were conducted to determine the effects of sintering temperature, pH and H2O2 concentration on the stabilization of Cr6+ in ceramsite. The results show that leaching of Cr6+ changes little at temperatures above 900 degrees C, and both pH and H2O2 concentration have some effects on the leaching of Cr6+. Leaching test results indicate that Cr6+ is stabilized in ceramsite and cannot be easily released to the environment again as secondary pollution, which eliminates the concern for its application. XRD analysis of ceramsite sintered at 1000 degrees C reveals that the main compounds of Cr6+ in ceramsite are Cr2O3 and FeCrO4. The test results provides a better understanding of the factors that affect the mobility of Cr6+, and show it is a safe way to make ceramsite with sludge as an additive.
Xu
G R
GR
School of Municipal and Environmental Engineering, Harbin Institute of Technology, PO Box 2602, Harbin, Heilongjiang Province, China. xgr@hit.edu.cn <xgr@hit.edu.cn>
Zou
J L
JL
Li
G B
GB
D000538:Aluminum Silicates; D002857:Chromium / Q000032:analysis*; D000077215:Clay; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D016877:Oxidants / Q000737:chemistry; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage; D017640:Silicates; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014961:X-Ray Diffraction
D000538:Aluminum Silicates; D016877:Oxidants; D012722:Sewage; D017640:Silicates; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D006861:Hydrogen Peroxide; C005691:sodium silicate; D000077215:Clay