Co-pyrolysis of metal contaminated oily waste for oil recovery and heavy metal immobilization

• Published in: Journal of hazardous materials 2019-07, Vol.373, p.1-10
• Main Authors: Tian, Yuan, Li, Jianbing, Yan, Xiuyi, Whitcombe, Todd, Thring, Ron
• Format: Article
• Language: English
• Subjects: Co-pyrolysis; Heavy metal; Hog fuel; Oil recovery; Risk assessment
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.03.061

•Co-pyrolysis with wood waste was used to treat heavy metal-contaminated oily waste.•More than 50% of total petroleum hydrocarbon recovery was achieved by co-pyrolysis.•Wood waste addition had positive effect on heavy metal immobilization in solid char.•Regression models for oil recovery and risk index of char residue were established.•A low temperature co-pyrolysis by adding 20% wood waste was found most effective. The treatment of metal-contaminated oily waste was investigated by using an approach of co-pyrolysis with hog fuel in a fixed bed reactor. Both oil recovery and heavy metal immobilization were evaluated. Three experimental factors, including pyrolysis temperature, reaction time, and hog fuel addition in the feedstock, were examined to find their effects on the treatment performance. Metal immobilization in the solid char obtained from co-pyrolysis was examined from its speciation characteristics. A higher pyrolysis temperature led to a decreased oil recovery but more non-bioavailable metal species in the char residue. This is also evident from the calculated risk index (RI) for eco-toxicity assessment, with RI of 34.6 and 117.1 at 600 °C and 400 °C, respectively. The addition of hog fuel into oily waste for co-pyrolysis also led to increased metal immobilization but a decreased overall oil recovery. A low temperature co-pyrolysis (400 °C) by adding 20% of hog fuel was found as the most effective oily waste disposal strategy with satisfactory oil recovery and an acceptable risk index of 54.1.