Phosphating sludge: properties and immobilization in ceramics

Abstract

Insertion of industrial waste into the ceramic matrix is one of the heavy metal binding technologies, allowing to obtain products fit for use or to reduce the volume of waste before final disposal at the same time. The properties of phosphating process waste and opportunities for its stabilization in the ceramic matrix are investigated in this study.
Before investigation of stabilization a thermogravimetric analysis of phosphating sludge has been performed. The sludge was heated at 400, 600 and 1000 °C, and SEM images of sludge were made. The SEM images show that re-crystallization processes occur during the heating of the sludge.
Ceramic samples for leaching tests were formed by adding 5 and 10% of phosphating sludge to the clay mass and by burning them at 900–1050 °C for 1–4 hours. The results of the leaching tests showed that the concentration of heavy metals from the burned ceramic samples containing 5 and 10% of phosphating sludge is less than the detection limit of the instrument, and at the same time it is below the allowable limits set out in the Wastewater Management Regulation. In this way, phosphating sludge stabilization in the ceramic proved as effective heavy metals immobilization and hazardous waste decontamination.