Leaching from fired brick discs with brick clay and sewage sludge ash

The concentrations of Cd, Cr, Cu, Ni, and Pb were measured by inductively coupled plasma atomic emission spectroscopy (ICP-OES; type Varian 720-ES ), after the material was first digested by Microwave Assisted Acid Digestion, using 0.5 g and 10 mL of concentrated nitric acid, according to the American Standard EPA 3051A. The content of Cl and SO4 was measured in a suspension with 10 g of sample and 25 mL of distilled water after 24 h of agitation, using ion chromatography (IC). The leaching of heavy metals was found by the leaching test, DS/EN 12457-2:2002, where 10 g of material and 100 mL of distilled water (L/S 10) were agitated for 24 h. The content of heavy metals in the leachate was measured with inductively coupled plasma mass spectrometry (ICP-MS). The leaching results were compared with the limiting level described in the Dutch Soil Quality Decree, 2015. All these analyses were made in triplicate.