Effect and mechanism of steel slag composition on CO2 fixation rate under microbial and non-microbial

In this study, we used microorganisms and steel slag to reduce CO2 emissions. The main objective is to investigate the influence and mechanisms of CO2 fixation rate based on the composition of steel slag. In the absence of microorganisms, steel slag powders with higher C2S content exhibit higher CO2 fixation rate. The absolute content of C2S decreases by 2.16–5.86 % and 3.43–14.21 % at 2 h and 48 h of carbon sequestration reaction, respectively. Under the action of microorganisms, the CO2 fixation rate of different steel slags increases by more than two-fold, with increases in amount of CO2 fixation at 2 h and 48 h of reaction being 142–169 % and 166–191 %, respectively. Microorganisms can enhance the reaction degree of C2S, C3S, and C2F phases in different steel slags. The increase in amount of CO2 fixation is particularly significant for steel slag powders with high C2S and C2F content. Enzymes secreted by microorganisms in the early stage of carbon sequestration can also increase the concentration of HCO3- and CO32- in the liquid phase, but this is influenced by the pH value and Ca2+ concentration of different steel slag leachates. Steel slag powders with lower leachate pH values and containing small amounts of Ca2+ will be more conducive to microorganisms enhancing the early-stage CO2 fixation rate. •The carbon fixation effect of different steel slag powders was tested.•Phase affecting CO2 fixation rate of steel slag without/with microbial.•Effect of leaching characteristics of steel slag on microbial enzymatic hydration.