Removal of heavy metals from water effluents using supermacroporous metal chelating cryogels

Applications of IDA in, for example, immobilized metal ion affinity chromatography for purification of His-tagged proteins are well recognized. The use of IDA as an efficient chelating adsorbent for environmental separations, that is, for the capture of heavy metals, is not studied. Adsorbents based on supermacroporous gels (cryogels) bearing metal chelating functionalities (IDA residues and ligand derived from derivatization of epoxy-cryogel with tris(2-aminoethyl)amine followed by the treatment with bromoacetic acid (defined as TBA ligand)) have been prepared and evaluated on capture of heavy metal ions. The cryogels were prepared in plastic carriers, resulting in desired mechanical stability and named as macroporous gel particles (MGPs). Sorption and desorption experiments for different metals (Cu²+, Zn²+, Cd²+, and Ni²+ with IDA adsorbent and Cu²+ and Zn²+ with TBA adsorbent) were carried out in batch and monolithic modes, respectively. Obtained capacities with Cu²+ were 74 μmol/mL (TBA) and 19 μmol/mL gel (IDA). The metal removal was higher for pH values between pH 3 and 5. Both adsorbents showed improved sorption at lower temperatures (10°C) than at higher (40°C) and the adsorption significantly dropped for the TBA adsorbent and Zn²+ at 40°C. Desorption of Cu²+ by using 1 M HCl and 0.1 M EDTA was successful for the IDA adsorbent whereas the desorption with the TBA adsorbent needs further attention. The result of this work has demonstrated that MGPs are potential treatment alternatives within the field of environmental separations and the removal of heavy metals from water effluents.