Photocatalytic nanocomposite materials based on inorganic polymers (Geopolymers): A review

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Geopolymers are ecologically-friendly inorganic materials which can be produced at low temperatures from industrial wastes such as fly ash, blast furnace slags or mining residues. Although to date their principal applications have been seen as alternatives to Portland cement building materials, their properties make them suitable for a number of more advanced applications, including as photocatalytic nanocomposites for removal of hazardous pollutants from waste water or the atmosphere. For this purpose, they can be combined with photocatalytic moieties such as metal oxides with suitable bandgaps to couple with UV or visible radiation, or with carbon nanotubes or graphene. In these composites the geopolymers act as supports for the photoactive components, but geopolymers formed from wastes containing oxides such as Fe2O3 show intrinsic photoactive behaviour. This review discusses the structure and formation chemistry of geopolymers and the principles required for their utilisation as photocatalysts. The literature on existing photocatalytic geopolymers is reviewed, suggesting that these materials have a promising potential as inexpensive, efficient and ecologically-friendly candidates for the remediation of toxic environmental pollutants and would repay further development

Comparative study on the preparation of belite cement from nano-silicas extracted from different agricultural wastes with calcium carbide residue

Belite cement was prepared using nano-silicas extracted from three different agricultural wastes–black rice husk ash (BRHA), bagasse ash (BA), and palm oil fuel ash (POFA)–which were reacted at 1200 − 1400 °C with CaC2 residue as calcium source. The product was compared with that from CaCO3. Nano-silica extracted from BRHA was of very fine particle size (surface area 312.4 m2/g and V/S ratio 0.35 × 106 cm) and being highly reactive, forms β-C2S at lower firing temperatures; however, at higher temperatures, less-desirable γ-polymorphs are formed. Nano-silica extracted from POFA contains Na2O, Al2O3, and K2O impurities, which stabilize the β and α-forms and delay the transformation to γ-phase. This is reflected in relatively high compressive strength at firing temperature above 1200 °C, compared to other mixtures. Thus, these results indicate that the best combination of these waste materials for the preparation of belite cement phases is POFA ash and CaC2 residue

Corrigendum to “The effect of nanoparticle and mesoporous TiO2 additions on the electronic characteristics of reduced graphene oxide nanocomposites with zinc oxide under UV irradiation” [Mater. Sci. Eng. B 246 (2019) 89–95] (Materials Science & Engineering B (2019) 246 (89–95), (S0921510719301679), (10.1016/j.mseb.2019.06.003))

© 2019 Elsevier B.V. The authors regret that due to insufficient accuracy when approving the final version, the required changes in affiliations are updated as above. The authors would like to apologise for any inconvenience caused