Adsorption behavior of Cr(VI) by biomass-based adsorbent functionalized with deep eutectic solvents (DESs)

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment

Background:

• Hexavalent chromium (Cr(VI)) poses significant environmental and health risks.
• Developing efficient and sustainable adsorbents for Cr(VI) removal is crucial.
• Peanut shells, an agricultural waste, offer potential as a low-cost biosorbent material.

Purpose of the Study:

• To evaluate deep eutectic solvents (DESs) functionalized peanut shell (PSD) as a biosorbent for Cr(VI) removal.
• To investigate the effects of various parameters on Cr(VI) adsorption performance.
• To characterize the modified biosorbent and understand the adsorption mechanism.

Main Methods:

• Peanut shells were modified using DESs.
• Scanning electron microscopy (SEM) and Point of Zero Charge (pHpzc) were used for characterization.
• Adsorption experiments were conducted to study kinetics, isotherms, and thermodynamics.

Main Results:

• DESs modification altered the peanut shell structure and its point of zero charge to 6.84.
• The pseudo-second-order kinetic model best described the adsorption process.
• Langmuir isotherm model fitted the data well, with a maximum adsorption capacity of 5.36 mg/g.
• Cr(VI) adsorption was spontaneous and endothermic.
• Desorption efficiency using NaOH was low (8.77%).

Conclusions:

• DESs-modified peanut shell is a promising biosorbent for Cr(VI) removal from water.
• The adsorption process is governed by pseudo-second-order kinetics and Langmuir isotherm.
• The low desorption efficiency suggests strong binding, requiring further investigation for regeneration.