Mineralization of Calcium Carbonates in Cellulose Gel Membranes

A diffusion‐driven mineralization approach for the fabrication of calcium carbonate on and in regenerated and functionalized cellulose membranes was investigated. Calcium dichloride was used as the cation source. Ammonium carbonate was applied in a gas‐phase diffusion and sodium carbonate in a liquid continuous‐flow setup. Calcium carbonate was obtained solely on the membrane surfaces from the gas‐diffusion approach, whereas by applying continuous‐flow diffusion, crystals were obtained throughout the membranes. The main polymorph was calcite with minor fractions of aragonite. The crystals were assembled from nanometer‐sized building blocks and showed a strong interaction with the cellulose matrix under continuous liquid flow conditions. The cellulose membranes acted as an insoluble template matrix with a rigid and fine mesh of cellulose fibers as superstructure, thereby resulting in a structure‐directing microenvironment for the calcium carbonate mineralization in a confined space.