The soot-water dispersion that is produced by quenching and/or scrubbing the raw effluent gas stream from a partial oxidation gas generator in a gas quench cooling and/or scrubbing zone is resolved in a decanter using two different liquid organic extractants. Advantageously, liquid organic by-products from an oxo or oxyl process which may contain harmful water soluble constituents may be used as a major portion of the liquid organic extractant. The dispersion of soot and co-extractants that is produced may be safely disposed of as a portion of the feed to the gas generator without polluting the environment. A novel vertical decanter is provided comprising a vertical cylindrical vessel with separate inner and outer coaxial concentric conduits that pass down through the central axial flanged inlet in the upper head of the vessel. The mixture of soot-water dispersion and first liquid organic extractant i.e. naphtha is passed through the inner conduit and is discharged through a first horizontal radial nozzle located below the interface level. Simultaneously, the second liquid organic extractant i.e. liquid organic by-products from an oxo or oxyl process is passed through the annular passage between the inner and outer conduits and is discharged through a second horizontal radial nozzle located above the interface level. Adjusting means are provided to vary the discharge height of the second horizontal radial nozzle, up or down should there be a change in location of the interface level.