Adsorption of Hexavalent Chromium from Aqueous Solution by a Chitosan/Bentonite Composite: Isotherm, Kinetics, and Thermodynamics Studies

Abstract

In this work, the chitosan/bentonite composite was favorably prepared and further used for Cr­(VI) removal from aqueous solutions via a batch adsorption process. The characteristics of the chitosan/bentonite composite were determined by using scanning electron microscopy, Brunner–Emmet–Teller measurement, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction, and the results reveal the evidence of the interaction between functional groups of chitosan with bentonite, which is helpful for the adsorption of Cr­(VI). The adsorption performance of the chitosan/bentonite composite is better than that of chitosan or bentonite, and the effects of adsorbent dosage, shaking speed, pH, and temperature were investigated. The results indicate that the percentage removal of Cr­(VI) increases with an increase in adsorbent dosage, the external diffusion resistance is maintained constant when the shaking speed exceeds 210 rpm, and the optimum pH is 3. The isotherm and kinetic experimental data of Cr­(VI) adsorption onto the chitosan/bentonite composite were best-fitted by Redlich–Peterson and Elovich models, respectively. The adsorption process is an exothermic and of the multilayer variety. The desorption rates of Cr­(VI) can be achieved at 60.1% with 0.1 M NaOH. The analysis FT-IR of adsorbents before and after adsorption, adsorption thermodynamics and kinetics, and desorption experiment reveal that the adsorption of Cr­(VI) on the chitosan/bentonite composite is predominantly a chemical interaction. The above results suggested that the chitosan/bentonite composite can be employed as a cost-effective and environmentally friendly adsorbent for Cr­(VI) removal from wastewater.

Adsorptive Removal of Manganese Ions From Polluted Aqueous Media by Glauconite Clay- Functionalized Chitosan Nanocomposites: Adsorption, Kinetic, Isotherm, and Thermodynamic Investigations

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“…Heavy metals are considered one of the main sources of industrial wastewater pollution, which seriously menace the human health and the biological environment. It is necessary to remove the inorganic pollutants from wastewater before being discharged into the environment due to their high stability and non-degradable nature (1,2). Although some heavy metals such as manganese, copper, iron, and zinc are essential for human health under particular concentrations, but above these concentrations they become toxic and cause various health problems (3).…”

Banana Peel Powder as an Effective Multilayer Adsorbent of Ammonium Ions

“…The pseudo-second-order kinetic models justify the adsorption of ions on the surface of the adsorbent through chemical adsorption (chemisorption) . This model, as described by Ho and Mckay, is represented by eq …”

Ultrahigh Adsorption Capacity of Acrylic Acid-Grafted Xanthan Gum Hydrogels for Rhodamine B from Aqueous Solution

“…Thermodynamics: Effect of Temperature on Adsorption. The three main thermodynamic parameters such as change in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) were determined at a temperature range from 293 to 323 K. The thermodynamic parameters were evaluated by thermodynamic van't Hoff eqs 11 and 12 39…”

“…The three main thermodynamic parameters such as change in free energy (Δ G ), enthalpy (Δ H ), and entropy (Δ S ) were determined at a temperature range from 293 to 323 K. The thermodynamic parameters were evaluated by thermodynamic van’t Hoff eqs and where K L is the equilibrium constant obtained from the proportion of adsorbate on the polymer ( Q e ) to that of the adsorbate in solution ( C e ) at equilibrium from the Langmuir model (L/g).…”