*Article* **Alkali-Activated Materials as Catalysts for Water Purification**

**Anne Heponiemi \* , Janne Pesonen , Tao Hu and Ulla Lassi**

Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland; janne.pesonen@oulu.fi (J.P.); tao.hu@oulu.fi (T.H.); ulla.lassi@oulu.fi (U.L.) **\*** Correspondence: anne.heponiemi@oulu.fi

**Abstract:** In this study, novel and cost-effective alkali-activated materials (AAMs) for catalytic applications were developed by using an industrial side stream, i.e., blast furnace slag (BFS). AAMs can be prepared from aluminosilicate precursors under mild conditions (room temperature using non-hazardous chemicals). AAMs were synthesized by mixing BFS and a 50 wt % sodium hydroxide (NaOH) solution at different BFS/NaOH ratios. The pastes were poured into molds, followed by consolidation at 20 or 60 ◦C. As the active metal, Fe was impregnated into the prepared AAMs by ion exchange. The prepared materials were examined as catalysts for the catalytic wet peroxide oxidation (CWPO) of a bisphenol A (BPA) aqueous solution. As-prepared AAMs exhibited a moderate surface area and mesoporous structure, and they exhibited moderate activity for the CWPO of BPA, while the iron ion-exchanged, BFS-based catalyst (Fe/BFS30-60) exhibited the maximum removal of BPA (50%) during 3 h of oxidation at pH 3.5 at 70 ◦C. Therefore, these new, inexpensive, AAM-based catalysts could be interesting alternatives for catalytic wastewater treatment applications.

**Keywords:** alkali-activated material; geopolymer; blast furnace slag; catalytic wet peroxide oxidation; Fe-catalyst; bisphenol A
