Functionalization of kaolinite for removal of phosphate from urban sewage

The PO43− widespread in urban sewages promotes eutrophication of water sources, with harmful effects to natural life and endanger human health. The removal of PO43− 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 PO43− from urban sewage. The kaolinite commercial did not remove PO43- from aqueous solution. However, the functionalized kaolinite (FK) was efficient, with a maximum removal capacity of 8.4 ± 0.1 mg PO43−/L, within less than 1 min of reaction. The removal of PO43- is associated with precipitation of pyromorphite, a mineral with low solubility (Ksp < 10−79,6). Finally, real urban sewage samples (raw and treated) were also tested for removal of PO43- using FK, confirming its effectiveness. The central aspects of this development are: • Functionalized kaolinite (FK), with Pb(II), for removal of PO43− from urban sewage was studied. • The FK was efficient for removal of up to 8.4 mg PO43−/L from aqueous solution, within a short reaction time. • The precipitation of pyromorphite was the mechanism responsible for removal of PO43- and FK efficiency have been confirmed for real urban sewage samples.

Palavras-chave

Clay minerals, Functionalization of kaolinite for removal of phosphate from urban sewage, Mineral precipitation, Phosphate removal, Surface functionalization