Clay honeycomb monoliths for water purification: Modulating methylene blue adsorption through controlled activation via natural coal templating

• Published in: Applied surface science 2013-07, Vol.277, p.242-248
• Main Authors: Gatica, José M., Gómez, Diana M., Harti, Sanae, Vidal, Hilario
• Format: Article
• Language: English
• Subjects: Adsorption; Clay; Coal; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Honeycomb monoliths; Methylene blue; Physics
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.04.034

•A “green-chemistry-type” alternative approach to activating clay honeycombs is proposed.•The control of the coal particle size used as a template allows modulating clay macroporosity.•The adsorption capacity is enhanced and the kinetics adjusted as function of texture. Texturally modified clay honeycomb monoliths were prepared for use as filters to remove pollutants from water solutions. An easy, economical, “green chemistry” activation route was employed during the preparation to enhance the adsorption capacity of the honeycombs. The method involves mixing the clay before its extrusion with a natural coal that is subsequently eliminated from the monolith by heating it under air at the lowest possible temperature (440°C according to a thermogravimetric study). The size of the coal particles used as a template was intentionally modified by adjusting the milling process (dry or wet) and its duration (1–120min) to modulate the porosity induced in the clay monoliths after their further burning. N2 physisorption, mercury porosimetry, granulometry and SEM were used to investigate the influence of the above preparative variables on the textural properties of the clay, significant effects being found in the macropore range. Methylene blue adsorption tests under dynamic conditions suggest that there is a correlation between pollutant removal and the macropore structure generated. FTIR spectroscopy indicates that the differences observed in cationic dye adsorption over the monoliths must be related to their different texture rather than to differences in the nature of their surface hydroxyl groups.