Technically exploitable mineral carbonation potential of four alkaline waste materials and effects on contaminant mobility
Kevin Schnabel, Felix Brück, Sven Pohl, Tim Mansfeldt, Harald Weigand
Abstract
Abstract Mineral carbonation of alkaline wastes can contribute to the sequestration of carbon dioxide (CO 2 ). In this study we examined the CO 2 sequestration potential of four dry‐discharged waste materials using theoretical and experimental approaches. The materials encompassed biomass bottom ash, biomass fly ash, refuse‐derived fuel fly ash, and stainless‐steel slag. Their CO 2 sequestration potential was determined from the acid neutralization capacity (ANC) and alternatively from the elemental composition using the Steinour equation (StE). Results were compared to experimental data from batch carbonation tests performed with pure CO 2 at near atmospheric pressure over 7 days. Influence of water content on the CO 2 uptake was determined in short‐term carbonation tests over 2 hr. Effects related to the hydration and the subsequent carbonation were investigated by thermogravimetric analysis and leaching tests. Depending on the material the experimental CO 2 uptakes ranged from 0.99 to 2.54 mol kg −1 . The ANC‐based approach either under‐ or overestimated the experimental CO 2 uptake and the StE strongly overestimated the experimental CO 2 uptake throughout. Except for biomass fly ash the experimental CO 2 uptake within a test period of 2 hr depended on the moisture content. Upon carbonation the leachate pH decreased and amphoteric trace elements tended to be immobilized. In contrast to this, the mobility of oxyanions increased by two orders of magnitude. Our results suggest that for the design of CO 2 sequestration strategies experimental investigations of the CO 2 uptake are preferable to indirect estimates. When using waste materials for CO 2 sequestration, effects on contaminant mobility must be considered since these determine disposal costs. © 2021 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons, Ltd.