Adsorption of cationic polyacrylamide onto sepiolite

Area of Science:

• Materials Science
• Environmental Chemistry
• Surface Chemistry

Background:

• Polyacrylamide (PAM) is widely used but its removal from aqueous solutions is crucial.
• Sepiolite, a natural clay mineral, is explored as a cost-effective adsorbent.
• Understanding adsorption mechanisms is key for effective water treatment.

Purpose of the Study:

• To investigate the adsorption of cationic polyacrylamide (PAM) onto sepiolite from aqueous solutions.
• To determine the influence of various parameters on PAM adsorption capacity.
• To evaluate the adsorption mechanism using isotherm models and thermodynamic analysis.

Main Methods:

• Systematic adsorption experiments varying calcination temperature, pH, ionic strength, and temperature.
• Adsorption isotherm studies fitted to Langmuir and Freundlich models.
• Zeta potential measurements to understand surface charge interactions.
• Thermodynamic parameter calculations (Gibbs free energy, enthalpy, entropy).

Main Results:

• Adsorption capacity increased with pH (5.50-11.00), temperature (25-55°C), and ionic strength (0-0.1molL⁻¹).
• Sepiolite calcined at 200°C exhibited superior adsorption.
• Langmuir model best described the adsorption data, indicating monolayer adsorption.
• Zeta potential studies revealed pH-dependent surface charge and PAM's influence on sepiolite's isoelectric point.

Conclusions:

• Sepiolite is a promising adsorbent for removing cationic polyacrylamide from wastewater.
• Adsorption is influenced by solution chemistry and sepiolite's surface properties.
• The Langmuir model and thermodynamic data provide insights into the adsorption mechanism.