Maximizing Adsorption Involving Three Solutes on Enhanced Adsorbents Using the Mixture-Process Variable Design.

Area of Science:

• Environmental Chemistry
• Materials Science
• Adsorption Science

Background:

• Activated carbon is widely used for adsorbing organic pollutants from water.
• Optimizing adsorption processes is crucial for efficient pollutant removal.
• Existing methods often fail to account for complex interactions between mixture and process variables.

Purpose of the Study:

• To optimize the solute removal efficacy of unmodified (UN), acid-treated (AT), and microwave-acid-treated (MAT) activated carbons.
• To develop an improved method for simultaneously optimizing feed mixture compositions and process variables (pH, adsorbent dosage).
• To investigate the trade-offs between maximizing adsorbent loading (q_total) and total percentage removal (PR_total).

Main Methods:

• Experimental optimization of adsorption using acetaminophen, benzotriazole, and caffeine as model solutes.
• Application of response surface methodology, including a novel steepest ascent method for simultaneous optimization.
• Fitting experimental data to empirical models with high statistical validity (adjusted R² > 0.95, p > 0.22, predictive R² > 0.93).

Main Results:

• Significant interactions were observed between mixture compositions and process variables.
• The developed steepest ascent method successfully tracked optimal settings.
• Optimal conditions for maximum adsorbent utilization differed from those for maximum percentage removal, with compromise solutions identified for each adsorbent type.

Conclusions:

• Simultaneous optimization of mixture and process variables is essential for effective activated carbon-based pollutant removal.
• The novel steepest ascent method provides a robust approach for identifying globally optimal adsorption conditions.
• Microwave-acid-treated activated carbon demonstrated superior performance in terms of both adsorbent loading and percentage removal.