Innovative application for bauxite residue: Red mud-based inorganic polymer spheres as pH regulators
authors Novais, RM; Carvalheiras, J; Seabra, MP; Pullar, RC; Labrincha, JA
nationality International
journal JOURNAL OF HAZARDOUS MATERIALS
author keywords Bauxite residue; Biomass fly ash; Geopolymer; pH buffer capacity; Alkalis leaching
keywords CONTINUOUS ANAEROBIC-DIGESTION; ASH-BASED GEOPOLYMERS; FLY-ASH; BUFFER CAPACITY; WASTE; REMOVAL; MICROSTRUCTURE; WASTEWATERS; HYDROLYSIS; MONOLITHS
abstract In this study, and for the first time, red mud (RM)-based geopolymer spheres were synthesised, with varying porosity and RM content, and then their use as pH regulators was evaluated. The aluminosilicate sources of these inorganic polymers were 100% waste-based, consisting of a mixture of RM and fly ash wastes. Geopolymer spheres containing up to 60 wt.% RM were successfully produced, while higher RM contents distorted the specimens' spherical shape. Results showed that alkalis leaching from the spheres over time can be controlled by their porosity, while the RM content induces only minor changes to leaching. The RM-based spheres leached up to 0.0237 mol/dm(3)g of OH- ions from their structure, this being among the highest values ever reported for geopolymers. This allowed a continuous and prolonged pH buffer capacity with narrow pH decay over the 28 days (2.4 pH units), suggesting the use of the RM-based spheres as pH buffering materials in wastewater treatment and anaerobic digestion systems.
publisher ELSEVIER SCIENCE BV
issn 0304-3894
year published 2018
volume 358
beginning page 69
ending page 81
digital object identifier (doi) 10.1016/j.jhazmat.2018.06.047
web of science category Engineering, Environmental; Environmental Sciences
subject category Engineering; Environmental Sciences & Ecology
unique article identifier WOS:000442334400008
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journal impact factor (jcr 2016): 6.065
5 year journal impact factor (jcr 2016): 6.393
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