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 Ni2+ ions at room temperature. The new hydrated products of metahalloysite (Si2Al2O5(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 Ni2+ and negative charge of [AlO4]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, Ni2+ ions and the iron oxides of wustite (FeO) and calcium iron oxide (Ca2Fe2O5) from the steel slag. A probable mechanism of photocatalytic oxidative degradation was proposed.
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