Wet regeneration treatment for the reclamation of waste foundry sands: a case study

The efficiency of a wet treatment process for the reclamation of exhaust sands coming out from different foundries and moulding procedures is evaluated in this technical note. The reclamation process foresees sequential phases of magnetic separation, wet attrition, screening. The produced sludges are thickened by means of chemical conditioners and mechanical dewatering. The process was tested on industrial scale on exhaust sands coming from different cast iron and steel foundries, considering both green sands and sands mixed with inorganic and organic binders. For each kind of sand, inflow and outflow in relation to the adopted reclamation treatment were characterized: the particle-size analysis and the determination of silica, loss on ignition, acid request, oolitic and some metals contents were performed. The characterization was also extended to a green sand sample coming from a thermal reclamation treatment, and to some bentonite and coal dust samples commonly employed in foundry processes. A final valuation of the process was performed keeping into account the obtained quality of recovered silica sands considering the foundry requirements and the economical end environmental aspects of the reclamation treatment.