Leaching Performance and Zinc Ions Removal from Industrial Slag Leachate Using Natural and Biochar Walnut Shell

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Industrial zinc slag poses environmental risks due to heavy metal leaching.
• Effective methods for removing zinc ions from leachate are crucial for sustainable waste management.

Purpose of the Study:

• To investigate zinc slag leaching characteristics using various standard methods.
• To evaluate the adsorption potential of natural and biochar walnut shells for zinc ion removal.
• To optimize adsorption conditions and determine the zinc removal mechanism.

Main Methods:

• Leaching tests: Toxicity Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP), ASTM-D3987, TS EN-12457-4.
• Adsorption experiments using natural and biochar walnut shells with varying adsorbent dosages, pH, and contact times.
• Kinetic modeling (pseudo-second-order) to elucidate the adsorption mechanism.

Main Results:

• TCLP leachate exhibited the highest zinc concentration (38.575 mg/L).
• Natural and biochar walnut shells achieved 84% and 92% zinc removal efficiency, respectively, at optimal dosages.
• Adsorption efficiency increased under alkaline conditions and followed pseudo-second-order kinetics, indicating chemical adsorption.
• Up to 96% zinc removal was achieved under optimized conditions.

Conclusions:

• Walnut shell-based adsorbents are effective and economical for removing zinc ions from industrial slag leachate.
• The study presents a novel approach for zinc removal from industrial waste, achieving high efficiency.
• Chemical adsorption via pseudo-second-order kinetics is the primary mechanism for zinc removal by walnut shell adsorbents.