Development of supercritical water oxidation technology for application to hazardous waste treatment: An extreme case study

Batch and continuous co-treatment of two typical hazardous wastes via supercritical water oxidation technology (SCWO) was investigated, that is, oil-based drill cuttings (OBDC) from a shale gas field and high-nickel-content electroplating sludge (Ni-EPS) from an electroplating factory. OBDC, an extreme representative of hazardous waste rich in organic materials, acts as an auxiliary fuel that provides heat from exothermic reactions during SCWO. The average reaction temperature in the continuous reactor increased from 378 degrees C to 495 degrees C. Ni-EPS, an extreme representative of hazardous waste rich in metals, acts as both a diluent and a catalyst. Metals in the NiEPS tend to form NiFe2O4, ZnFe2O4, and NiCr2O4 after SCWO treatment, and when OBDCs are present, they are transformed into metal oxides (MOx). All the metal oxides are in the form of nanoparticles and exhibit catalytic activity. Owing to the synergistic effect of high temperature and in-situ formation of nanocatalyst materials, the total organic carbon (TOC) in the effluents was as low as 8 mg L-1, and the TOC removal efficiency (CRE) reached as high as 99.96%. This study provides an alternative process for the efficient and complete treatment

Automated summary

This study investigated the batch and continuous co-treatment of oil-based drill cuttings and high-nickel-content electroplating sludge using supercritical water oxidation technology. The organic-rich waste acted as auxiliary fuel, while the metal-rich waste acted as a diluent and catalyst. After treatment, metal oxides in the form of nanoparticles showed catalytic activity, leading to efficient and complete removal of organic carbon.