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

Abstract A new type of Ni,Ca-cementitious material was firstly synthesized via a two-step reaction of alkali-activated steel slag polymerization and ion exchange. The XRF results showed that almost all the Na + ions in the matrix of Na,Ca-cementitious material were replaced by Ni 2+ ions at room temperature. The new hydrated products of metahalloysite (Si 2 Al 2 O 5 (OH) 4 ) and calcium silicate hydrate (CSH) were formed in the Na,Ca-cementitious material. The diffuse reflectance UV–vis near infrared ray spectrum was blue-shifted due to the strong interaction between Ni 2+ and negative charge of [AlO 4 ] 5− tetrahedron in the framework of cementitious material. The Ni,Ca-cementitious material was used as a catalyst for the photocatalytic degradation of methylene blue dye and showed a degradation rate of 94.39% under UV irradiation. The high photocatalytic degradation activity was suggested to be the synergistic effect of the cementitious matrix, Ni 2+ ions and the iron oxides of wustite (FeO) and calcium iron oxide (Ca 2 Fe 2 O 5 ) from the steel slag. A probable mechanism of photocatalytic oxidative degradation was proposed.