Red mud- and metakaolin-based geopolymers for adsorption and photocatalytic degradation of methylene blue: towards self-cleaning construction materials

Abstract

Here, we investigated the performance of red mud (RM)- and metakaolin (MK)-based geopolymers for the adsorption and photocatalytic degradation of methylene blue to demonstrate their potential as self-cleaning, environmentally friendly construction materials. Compressive strength measurements showed that the mechanical performances of the synthesized RM- and MK-based geopolymers vary between 37.7 and 43.2 MPa, indicating that these materials are promising for construction applications. Next, the materials were tested for methylene blue removal both under dark and UV-light conditions. Data showed that the RM- and MK-based geopolymer, without any anatase addition, works both as an adsorbent and a photocatalyst for the removal of methylene blue from wastewater. Systematic increase of anatase concentration resulted in an increase in the photocatalytic activity. For instance, the geopolymer with an anatase loading of 3.7 wt% provided more than three-times higher apparent photodegradation rate constant compared to that of pure anatase under identical conditions. These results demonstrate that a hazardous industrial waste, RM, globally produced in huge amounts, can be effectively utilized in the production of environmentally friendly construction materials with self-cleaning ability without sacrificing from mechanical performance.