Blast furnace slag was also used by Oguz to remove phosphate from aqueous solutions. The mechanisms of phosphate removal were explained on the basis of the results of X-ray spectroscopy, measurements of zeta potential of particles, specific surface area, and images of scanning electron microscopy ( SEM ) of the particles before and after adsorption. It was proposed that the removal of phosphate predominantly occurred by a precipitation mechanism and weak physical interactions between the surface of adsorbent and the metallic salts of phosphate. Heated samples of acid-treated slag and mixtures of slag with kaolinite and Al(OH)3 were examined by Jha et al. to determine their uptake capacities for NH4+ and PO43− from aqueous solutions. The highest PO43− uptake capacity was obtained with the slag–Al(OH)3 mixture heated at 900 ◦C whereas the highest uptake of NH4+ was found in the slag–Al(OH)3 mixture heated at 800 ◦C. It was shown that heating slag composites prior to incorporation into wastewater treatment filters resulted in an increased degree of NH4+ and PO43− uptake.