Functionalization of kaolinite for removal of phosphate from urban sewage

The PO(4)(3−) widespread in urban sewages promotes eutrophication of water sources, with harmful effects to natural life and endanger human health. The removal of PO(4)(3−) from urban sewage requires treatment at tertiary level, with high costs and low efficiency in most cases. Thus, a functionalization method for surface modification of kaolinite was proposed to improve the removal of PO(4)(3−) from urban sewage. The kaolinite commercial did not remove PO(4)(3-) from aqueous solution. However, the functionalized kaolinite (FK) was efficient, with a maximum removal capacity of 8.4 ± 0.1 mg PO(4)(3−)/L, within less than 1 min of reaction. The removal of PO(4)(3-) is associated with precipitation of pyromorphite, a mineral with low solubility (K(sp) < 10(−79,6)). Finally, real urban sewage samples (raw and treated) were also tested for removal of PO(4)(3-) • Functionalized kaolinite (FK), with Pb(II), for removal of PO(4)(3−) from urban sewage was studied. • The FK was efficient for removal of up to 8.4 mg PO(4)(3−)/L from aqueous solution, within a short reaction time. • The precipitation of pyromorphite was the mechanism responsible for removal of PO(4)(3-) and FK efficiency have been confirmed for real urban sewage samples.