Adsorption of aqueous Pb(II) using non-devulcanized and devulcanized tyre rubber powder: a comparative study

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Used tyre rubber presents a significant waste management challenge.
• Tyre rubber's potential as a low-cost adsorbent for heavy metal remediation is of growing interest.
• Devulcanization processes can alter rubber's surface properties, potentially enhancing its adsorption capabilities.

Purpose of the Study:

• To compare the efficiency of non-devulcanized tyre rubber (NTR) and devulcanized tyre rubber (DTR) for lead (Pb(II)) ion adsorption from aqueous solutions.
• To investigate the effects of adsorbent dose, initial metal concentration, and contact time on Pb(II) adsorption.
• To elucidate the adsorption mechanisms using isotherm and kinetic models.

Main Methods:

• Preparation of NTR and DTR particles (100-200 µm) from used truck tyres.
• Mechano-chemical devulcanization process for DTR preparation.
• Adsorption experiments with varying adsorbent doses (5-15 g/L), initial Pb(II) concentrations, and contact times.
• Adsorbent characterization using SEM-EDS, FTIR, and XRD.
• Analysis of adsorption data using Langmuir isotherm and pseudo-second-order kinetic models.

Main Results:

• DTR exhibited significantly higher Pb(II) adsorption capacity (75.1 mg/g) compared to NTR (6.61 mg/g), as predicted by the Langmuir model.
• The pseudo-second-order kinetic model best described the adsorption process for both tyre rubber types.
• Optimal adsorption conditions were determined as 5 g/L adsorbent dose and 120 min contact time.
• Increased surface roughness of DTR post-devulcanization was identified as the reason for its superior performance.
• Leaching of zinc (Zn) during Pb(II) adsorption suggested a potential ion-exchange mechanism.

Conclusions:

• Devulcanization is an effective method to enhance the adsorption performance of waste tyre rubber for Pb(II) removal.
• DTR demonstrates considerable potential as a sustainable and cost-effective adsorbent for treating lead-contaminated water.
• Further research into the ion-exchange mechanism and optimization for industrial applications is warranted.