Adsorption of Phosphate and Ammonium on Waste Building Sludge

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 (B_Fe/TS_Fe) for the adsorption of NH₄⁺ and PO₄^3- 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 (PO₄^3-). The adsorption of PO₄^3- had a high efficiency (>99%) on B, B_Fe and TS_Fe, while for TS, the adsorption of PO₄^3- was futile due to the high content of available P in the raw TS. The adsorption of NH₄⁺ on all sorbents (B/B_Fe, TS/TS_Fe) 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/B_Fe and TS/TS_Fe before and after NH₄⁺ and PO₄^3- sorption when the contents of these ions in the leachates were affected by adsorption experiments in the cases of B and TS. For B_Fe and TS_Fe, the ion content in the leachates before and after the adsorption experiments was similar.