Chemical reclamation of waste green foundry sand and its application in core production

The disposal of Waste Foundry Sand (WFS) poses a significant challenge for the foundry industry today, primarily due to its composition of metal oxides (Al₂O₃, Fe₂O₃, MgO, CaO, and Na₂O) and sand. These metal oxides, categorized as loosely and strongly bound clays, are considered impurities in core production. This study proposes a chemical reclamation technique for WFS using fresh acid solutions or acidic industrial effluent. Experiments were conducted to remove the loosely and strongly bound clays from the WFS, optimizing parameters such as acid concentration, sand to acid loading, temperature, stirring speed, and reaction time to achieve optimal performance. The quality of the reclaimed sand was evaluated using various foundry standard tests, including determination of clay contents, compressive strength, Grain Fineness Number (GFN), Loss on Ignition (LOI), Acid Demand Value (ADV), and scanning electron microscopy. The reclaimed sand exhibited a loosely bound clay content of 1.5 %, oolitic content of 5.5 %, a grain fineness number of 55, a loss on ignition of 1.92 %, and an acid demand value of 1.5 ml/100 g of sand. Field trials demonstrated that the reclaimed sand can be effectively used for core production at an economical rate.