Microalgal-biochar immobilized complex: A novel efficient biosorbent for cadmium removal from aqueous solution

Area of Science:

• Environmental Science
• Bioremediation Technologies
• Materials Science

Background:

• Cadmium (Cd) is a toxic heavy metal posing significant environmental and health risks.
• Bioremediation offers a sustainable approach for removing heavy metal contaminants from water.
• Microalgae and biochar are recognized for their potential as low-cost biosorbents.

Purpose of the Study:

• To investigate the feasibility of using a microalgal-biochar immobilized complex (MBIC) for cadmium bioremediation.
• To compare the cadmium removal efficiency of MBIC with its individual components (microalgae and biochar).
• To determine the optimal operating parameters and adsorption mechanisms for MBIC-based cadmium removal.

Main Methods:

• Biosorption experiments were conducted by varying parameters like pH, biosorbent dosage, initial Cd(II) concentration, and microalgal-biochar ratio.
• Adsorption isotherm models (Langmuir, Sips) and kinetic models (pseudo-second-order) were applied to analyze the data.
• Surface characterization techniques including zeta potential, Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR) were employed.

Main Results:

• The MBIC demonstrated a maximum Cd(II) adsorption capacity of 217.41 mg/g, significantly higher than Chlorella sp. (169.92 mg/g) or biochar (95.82 mg/g) alone.
• The Sips model best described the adsorption isotherm for MBIC, while the pseudo-second-order model accurately fitted the biosorption kinetics (R² > 0.999).
• Electrostatic attraction, ion exchange, and surface complexation were identified as the primary mechanisms for Cd removal by MBIC.

Conclusions:

• The microalgal-biochar immobilized complex (MBIC) is a highly effective material for cadmium bioremediation.
• MBIC offers enhanced adsorption capacity and efficiency for cadmium removal compared to using microalgae or biochar independently.
• The study elucidates the key mechanisms driving cadmium adsorption, providing insights for optimizing bioremediation strategies.