Optimization of Au(III) adsorption by the Taguchi method using pyrogallol functionalized silica nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Chemistry

Background:

• Gold recovery from aqueous solutions is crucial for economic and environmental reasons.
• Developing efficient adsorbents for precious metal recovery is an active area of research.
• Nanoporous materials offer high surface area for adsorption applications.

Purpose of the Study:

• To synthesize and characterize pyrogallol-functionalized MCM41 nanoparticles (APMCM41-Py) for gold(III) adsorption.
• To optimize adsorption conditions using the Taguchi statistical method.
• To investigate the adsorption mechanism and kinetics of gold(III) onto APMCM41-Py.

Main Methods:

• Immobilization of pyrogallol onto aminopropyl-functionalized MCM41 nanoparticles.
• Application of the Taguchi method (L25 orthogonal array) to optimize adsorption parameters (pH, stirring speed, adsorbent mass, temperature, initial Au(III) concentration, time).
• Characterization using FTIR, SEM, EDX, and XRD; kinetic and isotherm studies (pseudo-second-order, Langmuir).

Main Results:

• Optimal adsorption conditions identified: pH 5, 250 rpm, 0.025 g adsorbent, 40 °C, 600 mg L⁻¹ Au(III), 15 min.
• Maximum Langmuir monolayer adsorption capacity of 168.54 mg g⁻¹ at 303 K.
• Adsorption follows pseudo-second-order kinetics and Langmuir isotherm, indicating a spontaneous, endothermic chemisorption process.
• Phenolic -OH groups on APMCM41-Py facilitate Au(III) adsorption via reduction.

Conclusions:

• APMCM41-Py is a highly efficient adsorbent for rapid gold(III) recovery from weakly acidic solutions.
• The Taguchi method effectively optimized adsorption parameters.
• The study provides insights into the adsorption mechanism and potential for practical gold recovery applications.