Adsorption of Phosphate and Ammonium on Waste Building Sludge

Abstract

Two selected waste building sludges (WBS) were used in this study: (i) sludge from the production and processing of prestressed concrete pillars (B) and (ii) sludge from the production of technical stone (TS). The materials were used in their original and Fe-modified forms (BFe/TSFe) for the adsorption of NH4+ and PO43− from contaminated waters. The experiments were performed on a model solution simulating real wastewater with a concentration of 1.7 mmol·L−1 (NH4+) and 0.2 mmol·L−1 (PO43−). The adsorption of PO43− had a high efficiency (>99%) on B, BFe and TSFe, while for TS, the adsorption of PO43− was futile due to the high content of available P in the raw TS. The adsorption of NH4+ on all sorbents (B/BFe, TS/TSFe) had a lower efficiency (<60%), while TS proved to be the most effective. Leaching tests were performed according to the CSN EN 12457 standard for B/BFe and TS/TSFe before and after NH4+ and PO43− sorption when the contents of these ions in the leachates were affected by adsorption experiments in the cases of B and TS. For BFe and TSFe, the ion content in the leachates before and after the adsorption experiments was similar.