Methods of improving settling of industrial pigment slurries

Abstract An experimental study on improvement of settling of three industrial pigment slurries, with trade names chrome yellow, molybdate orange and semi‐blacktone iron blue is reported. Three methods for improvement were employed. Additions of common surfactants did not improve settling rate of any slurry. Additions of a flocculating agent with trade name Hercofloc 825.2, on the other hand, improved the settling rates of all three slurries very significantly. Settling of chrome yellow slurries was increased a phenomenally one hundred fold by additions of Hercofloc 825.2. The exposure of the slurries to low frequency (540 kHz and 765 kHz) ultrasonic radiation increased the settling rate as high as six to seven fold. The effects of ultrasonic radiation on the settling of iron blue slurry of various solids concentration, and initial slurry height were investigated. Exposure of the slurry to ultrasonic radiation appears to be a viable and practical method for improving settling of industrial pigment slurries.