Batch study for Pb²⁺ removal by polyvinyl alcohol-biochar macroporous hydrogel bead

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment

Background:

• Lead (Pb II) contamination in aqueous solutions poses significant environmental and health risks.
• Development of efficient and cost-effective adsorbents is crucial for lead remediation.
• Polyvinyl alcohol (PVA), alginate, and biochar offer promising properties for adsorbent materials.

Purpose of the Study:

• To synthesize and characterize a novel PVA-alginate-biochar composite adsorbent.
• To evaluate the adsorption performance of the composite for lead (Pb II) removal from aqueous solutions.
• To investigate the adsorption mechanism and thermodynamic properties.

Main Methods:

• Batch adsorption experiments were conducted to assess Pb (II) removal.
• Adsorption data were analyzed using Langmuir and Freundlich isotherm models.
• Adsorption kinetics were determined using pseudo-first-order (PFO) and pseudo-second-order (PSO) models.
• Thermodynamic parameters (Gibbs free energy, enthalpy, entropy) were calculated.
• Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used for material characterization.

Main Results:

• The PVA-alginate-biochar composite demonstrated effective Pb (II) adsorption.
• Adsorption behavior was best described by the Langmuir isotherm model and PSO kinetic model.
• The maximum adsorption capacity for Pb (II) was found to be 176.40 mg/g.
• Adsorption process was spontaneous and exothermic.
• Optimal pH range for adsorption was determined to be 2-6, with minimal impact from sodium ion concentration.

Conclusions:

• The synthesized PVA-alginate-biochar composite is a highly efficient adsorbent for lead removal.
• The adsorption mechanism involves Langmuir-type binding and follows pseudo-second-order kinetics.
• The adsorbent exhibits excellent capacity and favorable thermodynamic properties for lead remediation.