Abstract
Chitosan (Cs)-based composites were developed by incorporating silica (Cs–Si), and both silica and hydroxyapatite (Cs–Si–Hap), comparatively tested to sequester hexavalent (Cr(VI)) ions from water. XRD and FT-IR data affirmed the formation of Cs–Si and Cs–Si–Hap composite. Morphological images exhibits homogeneous Cs–Si surface, decorated with SiO2 nanoparticles, while the Cs–Si–Hap surface was non-homogeneous with microstructures, having SiO2 and Hap nanoparticles. Thermal analysis data revealed excellent thermal stability of the developed composites. Significant influence of pH, adsorbent dose, contact time, temperature, and coexisting anions on Cr(VI) adsorption onto composites was observed. Maximum Cr(VI) uptakes on Cs and developed composites were observed at pH 3. The equilibration time for Cr(VI) adsorption on Cs–Si–Hap was 10 min, comparatively better than Cs and Cs–Si. The adsorption data was fitted to pseudo-second-order kinetic and Langmuir isotherm models with respective maximum monolayer adsorption capacities (qm) of 55.5, 64.4, and 212.8 mg/g for Cs, Cs–Si, and Cs–Si–Hap. Regeneration studies showed that composites could be used for three consecutive cycles without losing their adsorption potential.
Highlights
Water contamination is one of the most important global environmental concerns and is currently a subject of international attention [1]
The surfacemodified Si composites are cost-effective and easy to synthesize with minimal organic solvents requirement
The chemicals and reagents used during the research were of analytical reagent (A.R) grade or as itemized
Summary
Water contamination is one of the most important global environmental concerns and is currently a subject of international attention [1]. Water molecules in variable amounts are chemically bound to Si gels surfaces, and are widely incorporated into organic and inorganic materials to consolidate and improve their structures [18,19]. Due to their porosity, higher specific surface area, and better mechanical and thermal stabilities, the Si gel-based adsorbents are commonly used for the removal of organic and inorganic pollutions from wastewater [20,21]. The surfacemodified Si composites are cost-effective and easy to synthesize with minimal organic solvents requirement These solid silicon oxide particles can be bonded to watersoluble polymers that have an affinity to chemically chelate heavy metal ions. The effect of co-existing ions on Cr(VI) adsorption and regeneration potential of composite were tested
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