A new alkali-activated steel slag-based cementitious material for photocatalytic degradation of organic pollutant from waste water

► A novel Ni,Ca-cementitious material is synthesized by a two-step reaction. ► Ni,Ca-geopolymer is firstly used for the photocatalytic degradation of MB. ► Absorption bands in the UV and NIR regions are reported for the first time. ► A reaction mechanism of photocatalytic degradation was proposed.