Enhancement of phosphonomethylated PEI–Cu²⁺complex flocculation by Ca²⁺ ions: A new approach for heavy metal removal from aqueous solutions

Abstract

Removal of Cu ²⁺ ions from aqueous solutions by induced flocculation of PPEI with Ca ²⁺ ions was studied. Considerable floc formation accompanying Cu ²⁺ sequestration was demonstrated even at low initial metal concentration of 5 mg L^{− 1}. Flocculation capacity as high as 4.7 mmol Cu ²⁺/g PPEI at pH 6 was obtained. Ca ²⁺ showed minimal competition with Cu ²⁺ ions for adsorption sites in the polymer. The PPEI–Ca ²⁺ flocculant system was effective over a wide range of pH so that at an equilibrium pH of 1.5, more than 50% Cu ²⁺ removal was possible. The [CaCl₂]/[PPEI] ratio is a significant parameter with regards to achieving complete Cu ²⁺ removal. At optimized condition, the process is capable of scavenging Cu ²⁺ ions to background levels.

Keywords:

• Phosphonomethylated-polyethyethyneimine
• Flocculation
• Copper removal
• Calcium
• Chelation
• Wastewater treatment

Acknowledgments