Enhancing Cr (VI) Adsorption of Chestnut Shell Biochar through H₃PO₄ Activation and Nickel Doping

Area of Science:

• Environmental Chemistry
• Materials Science
• Waste Management

Background:

• Hexavalent chromium (Cr (VI)) poses significant environmental and health risks.
• Developing efficient and sustainable methods for Cr (VI) removal from water is crucial.
• Chestnut shell waste presents an underutilized resource for creating functional materials.

Purpose of the Study:

• To synthesize and characterize a high-efficiency nickel-doped porous biochar (PCNi3) from chestnut shell waste.
• To investigate the adsorption mechanisms and efficiency of PCNi3 for Cr (VI) removal from aqueous solutions.
• To evaluate the influence of various parameters on the remediation process.

Main Methods:

• Two-step chemical activation using phosphoric acid (H3PO4) and nickel doping.
• Characterization using XRD, FESEM, FTIR, Raman, BET, N2 adsorption, and XPS.
• Batch adsorption experiments to study the effects of pH, concentration, time, and temperature.

Main Results:

• PCNi3 exhibited enhanced microstructure and porosity, significantly improving Cr (VI) adsorption.
• Adsorption followed the Freundlich, pseudo-second-order kinetic, and Elovich models.
• The process was spontaneous, endothermic, and diffusion-limited.
• Effective Cr (VI) removal was achieved through ion exchange, complexation, electrostatic adsorption, and coprecipitation.

Conclusions:

• Nickel-doped porous biochar (PCNi3) is a highly effective adsorbent for Cr (VI) removal.
• The material demonstrates a dual function of adsorption and reduction of Cr (VI) to Cr (III).
• This study offers a sustainable approach to waste valorization for environmental remediation.