resumo
In this work, and for the first time, fly ash (FA)-based geopolymer (d = 2.6 mm) spheres were used to extract methylene blue from synthetic wastewaters. The influence of sorption time, dye initial concentration and adsorbent amount on the dye removal efficiency and uptake by the porous spheres was evaluated. The adsorbents' recyclability and their dye fixation efficiency were also considered. The initial dye concentration strongly affected the uptake and removal efficiency by the porous bodies, the former rising from 1.1 to 30.1 mg/g when the dye initial concentration jumped from 10 to 250 ppm, and the latter increasing from 82.3% to 94.3% when the dye initial concentration varied from 10 to 125 ppm. Results showed a much faster (24 h) and higher (30.1 mg/g) methylene blue uptake in comparison with the other bulk-type geopolymers reported to date (30 h; 15.4 mg/g). The cumulative methylene blue uptake shown by these innovative spheres (79.7 mg/g) surpasses all other powdered geopolymer adsorbents, being among the highest values ever reported for geopolymers. The adsorbent was successfully regenerated and reused eight times. Regeneration was found to negatively affect the MB uptake, but nevertheless, even after eight regeneration cycles a very high MB removal efficiency (83%) was maintained. The use of these bulk-type waste-based geopolymer adsorbents is a low-cost, more eco-friendly, safer and easier alternative to the use of powdered adsorbents in wastewater treatment systems, since these similar to 3 mm spheres may be used directly in packed beds, and were produced using significant amounts of waste material. (C) 2018 Elsevier Ltd. All rights reserved.
palavras-chave
BASIC DYE ADSORPTION; AQUEOUS-SOLUTION; COMPOSITES; ADSORBENTS; PHOTOCATALYST; EQUILIBRIUM; MONOLITHS; BEHAVIOR; ZEOLITE; SURFACE
categoria
Science & Technology - Other Topics; Engineering; Environmental Sciences & Ecology
autores
Novais, RM; Carvalheiras, J; Tobaldi, DM; Seabra, MP; Pullar, RC; Labrincha, JA
nossos autores
David Maria Tobaldi
Investigador
João António de Sousa Carvalheiras
Estudante de doutoramento
João António Labrincha Baptista
Professor Catedrático
Maria Paula Seabra
Professor Auxiliar
Rob Pullar
Colaborador
Rui Miguel Novais
Professor Auxiliaragradecimentos
This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. R.C. Pullar thanks the FCT for funding under grant IF/00681/2015.