Adsorption of Copper and Lead Ions onto Regenerated Sludge from a Water Treatment Plant

Abstract

In this study, water treatment sludges were sintered under various experimental conditions to generate Al-containing adsorbents. The adsorption of Cu²⁺ and Pb²⁺ onto sintered oxide was examined and sorption results were further modeled using a surface complex model. The specific surface area of the sintered adsorbent was substantially reduced from 30 m²/g (dried sludge) to 2 m²/g (sinter sludge). The pH-adsorption-edges of both Cu²⁺ and Pb²⁺ were shifted towards a higher pH than the edges of the unsintered adsorbent, revealing reduced affinity of the sintered adsorbent for metal ions. Metal leaching was measured by the TCLP procedure, and the results indicated that the amount of metal leaching by the sintered adsorbent was negligible. The effect of background electrolytes on Cu²⁺ and Pb²⁺ sorption was negligible. Triple-layer model (TLM) simulation revealed that Cu²⁺ and Pb²⁺ sorption on sintered adsorbent involves inner-sphere interactions and the dominant surface metal species are monodentates of Me²⁺ and MeOH⁺. The intrinsic adsorption constants of Cu²⁺ and Pb²⁺ on dried sludge, adsorbent sintered at 1000°C, and adsorbent sintered at 1100°C were also examined.

Keywords:

• Cu²⁺
• Pb²⁺
• Water treatment sludge
• Sinter
• Adsorption
• Surface complex model
• TLM

Acknowledgments

The authors would like to thank the National Science Council of the Republic of China for financially supporting this research under Contract No. NSC 90-2211-E-002-038.