abstract
Porous inorganic polymer (IP) monoliths were synthesised using a modified bauxite residue (BR) as the reactive fraction with the objective of using them as adsorbents for methylene blue (MB) from synthetic wastewater. First, unreactive, as-produced BR was transformed into a suitable glassy precursor material for IPs by blending BR with minor quantities of C and CaSiO3, thermally treating it at 1200 degrees C for 2 h, and quenching in water. The alkaline activation of this slag in combination with a pore foaming agent led to the formation of a highly porous microstructure with up to 85% in total porosity. The synthesised porous monoliths demonstrated high MB uptake (up to 17 mg of MB/g of IP with an initial MB concentration of 75 mg/L). A higher porosity of the monoliths, a higher pH, an increasing initial MB concentration as well as stirring of the testing solution have a positive effect on the adsorption capacity, while an optimum solution volume for adsorption was identified. Furthermore, the reuse of these novel monolithic adsorbents was demonstrated by repeating adsorption tests up to five cycles (adsorption-desorption), with a decrease in adsorption capacity of approximately 30%, but a promising cumulative uptake of about 40 mg of MB per g IP. (C) 2019 Elsevier Ltd. All rights reserved.
keywords
WASTE-WATER TREATMENT; ASH-BASED GEOPOLYMER; LOW-COST ADSORBENTS; FLY-ASH; ACTIVATED CARBON; DYE REMOVAL; AQUEOUS-SOLUTION; RED MUD; ADSORPTION; COMPOSITES
subject category
Science & Technology - Other Topics; Engineering; Environmental Sciences & Ecology
authors
Hertel, T; Novais, RM; Alarcon, RM; Labrincha, JA; Pontikes, Y
our authors
João António Labrincha Baptista
Full professor
Rui Miguel Novais
Assistant Professoracknowledgements
The research leading to these results has received funding from the European Community's Horizon 2020 Programme ([H2020/2014-2019]) under Grant Agreement no. 636876 (MSCA-ETN REDMUD). This publication reflects only the authors' views, exempting the Community from any liability. Project website: http://www.etn.redmud.org.The authors want to thank Dr. David Tobaldi for the discussions concerning the adsorption isotherms and Pithchai Pandian Sivakumar for the synthesis of the slag.