A Comparative Study on Hexavalent Chromium Adsorption onto Chitosan and Chitosan-Based Composites

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.

Biosorption of Cr(VI) Using Cellulose Nanocrystals Isolated from the Waterless Pulping of Waste Cotton Cloths with Supercritical CO2: Isothermal, Kinetics, and Thermodynamics Studies

“…However, the percentage of Cr(VI) removal increased with increasing treatment time due to the obtaining of the required contact time between CNCs’ surface and Cr(VI) for adsorption. Moreover, the increase of the active functional group with increasing adsorbent doses for adsorbing Cr(VI) increased the Cr(VI) removal [ 27 , 48 ]. Meanwhile, the percentage of Cr(VI) removal became negligible over 30 min treatment time because of the saturation of the CNCs’ surface with the adsorbed Cr(VI) [ 13 ].…”

“…The increase of Cr(VI) removal with increasing temperature from 28 ± 1 °C to 60 °C increased the kinetic energy, which enhanced the Cr(VI) binding on the surface of the CNCs and therefore increased the Cr(VI) adsorption. Moreover, an increase of the temperature decreased the solution’s viscosity, which substantially increased interaction between CNCs particles and Cr(VI) and therefore increased Cr(VI) adsorption [ 27 , 49 ]. However, the decrease of Cr(VI) removal with increasing temperature over 60 °C was due to the degrading of the CNCs particles, which substantially weakened the intermolecular force of CNCs particles and therefore decreased Cr(VI) binding on the surface of CNCs particles [ 13 , 26 ].…”

“…Of these, ion exchange and membrane filtration are viewed as the most effective treatment methods for the removal of Cr(VI) from industrial effluent. However, these processes are not commercially applicable for the removal of Cr(VI) from the industrial effluent due to their high operating cost [ 27 , 28 ]. Conversely, adsorption is a simple, versatile, and commercially viable process for the removal of Cr(VI) from the industrial effluent [ 27 ].…”

“…However, these processes are not commercially applicable for the removal of Cr(VI) from the industrial effluent due to their high operating cost [ 27 , 28 ]. Conversely, adsorption is a simple, versatile, and commercially viable process for the removal of Cr(VI) from the industrial effluent [ 27 ]. Over the years, various biobased materials are being used as an adsorbent to remove Cr(VI) from industrial effluent [ 27 , 29 ].…”

“…Conversely, adsorption is a simple, versatile, and commercially viable process for the removal of Cr(VI) from the industrial effluent [ 27 ]. Over the years, various biobased materials are being used as an adsorbent to remove Cr(VI) from industrial effluent [ 27 , 29 ]. Studies reported that adsorption using CNCs is considered a promising method for Cr(VI) removal because of its easy handling, high efficiency, high adsorption rate, reusability, and economic feasibility [ 24 , 29 ].…”