Abstract
In this work, a surface cationized inorganic–organic hybrid foam was produced from porous geopolymer (GP) and cellulose nanocrystals (CNCs). GPs were synthesized from alkali-activated metakaolin using H2O2 as a blowing agent and hexadecyltrimethylammonium bromide (CTAB) as a surfactant. These highly porous GPs were combined at pH 7.5 with cationic CNCs that had been synthesized from dissolving pulp through periodate oxidation followed by cationization in a deep eutectic solvent. The GP-CNC hybrid foams were employed as reactive filters in the removal of the anionic dye, methyl orange (MO; 5–10 mg/L, pH 7). The effects of a mild acid wash and thermal treatments on the structure, properties, and adsorption capacity of the GPs with CNCs and MO were investigated. The CNCs aligned as films and filaments on the surfaces of the neutralized GPs and the addition of CNCs improved MO removal by up to 84% compared with the reference sample. In addition, CTAB was found to disrupt the attachment of CNCs on the pores and improve adsorption of MO in the GPs with and without CNCs.
Highlights
Inorganic foams composed of ceramic materials,[1] metals,[2,3] carbon,[4] or boron nitride,[5] referred to as cellular solids or cellular solid materials,[6] are by definition ensembles of packed cells in a space with solid edges and faces.[7]
We report the surface modification of a porous metakaolin geopolymer foam with cationic cellulose nanocrystals (CNCs) produced from wood cellulose through periodate oxidation and a DESmediated imination reaction
CTAB was used as a surfactant because, based on the preliminary tests, it was found to produce a highly porous and water permeable structure with homogeneous pore-size distribution when combined with H2O2
Summary
Inorganic foams composed of ceramic materials,[1] metals,[2,3] carbon,[4] or boron nitride,[5] referred to as cellular solids or cellular solid materials,[6] are by definition ensembles of packed cells in a space with solid edges and faces.[7]. Geopolymers have been extensively studied as replacements for Portland cement,[19] but, due to the high intrinsic cation exchange capacity, they have been used (typically in powdered form) as adsorbents for the removal of cationic dyes (e.g., methylene blue) and heavy metals (e.g., Cu2+, Ni2+, Pb2+).[20,21] The introduction of large open pores (μm scale) to the geopolymer structure widens their prospects in adsorption applications[9] because of the increased water permeability and available surface area. These porous spheres[22,23] and monoliths[24,25] can be used instead of powders as adsorption media, which simplifies the separation of adsorbent and regeneration
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