Removal and recovery of copper from wastewater by a complexation-ultrafiltration process

Carboxyl methyl cellulose (CMC) as a water-soluble metal-binding polymer in combination with ultrafiltration (UF) was used in a hybrid approach for selective removal and recovery of copper from water. In the complexation-UF process the cationic forms of heavy metals were first complexed by a macro ligand in order to increase their molecular weight to having a size larger than the pores of the selected membrane that can be retained and flow out in the retentate whereas permeate water was purified to a certain extent from heavy metals. The complexation of Cu2+, Pb2+ Fe2+ and Mn2+ by CMC from synthetic solutions and real wastewater followed by UF filtration used as a complex separation step was studied. The aim was to recover water-soluble polymers and to obtain a heavy metal concentrate; attempts were also made to destroy the Me:CMC complexes by a pH decrease. The decomplexation procedure was followed by a second step of UF. The results obtained show that a low mole Cu:CMC ratio favors both ultrafiltrate permeability during the first stage of the process and the separation following the next step of complex destruction at a lower pH. The comparative experiments with (1)synthetic water containing copper as a single heavy metal; (2)copper containing a solution with addition of ferrous iron, manganese and lead; and (3) drainage mine water contaminated with copper, ferrous iron, manganese and lead show a selectivity for Cu during the first stage of UF approaching 99% in these three cases. However, the destruction of complexes of heavy metals from the real wastewater was limited - up to 80%.