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

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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.