Chromatographic method for pre-concentration and separation of Zn( ii ) with microalgae and density functional optimization of the extracted species

A novel wild strain of microalgae, Phormidium luridum containing Gloeothece rupestris and Chlorococcum infusionum (99 : 0.08 : 0.02), was studied for its ability to remove and retrieve Zn(ii) from aqueous solutions in the presence of some commonly occurring ions (Na super(+), K super(+), Cl super(-), SO sub(4) super(2-), ClO sub(4) super(-), NO sub(3) super(-)) in their natural contamination concentration range (50-300 mg L super(-1)). The algae, which were previously collected from the river basin (Ajay), were grown on naturally occurring gravels in a glass column of nutrient enriched raw water media. Systematic studies of the sorption of Zn(ii) (0.02 mg mL super(-1)) over a pH range of 4.5-7.5 identified a maximum removal extent of 104 mu M g super(-1) at neutral pH, mainly by adsorption at the surface layer. Zn(ii) was retrieved by selective elution with 5 10 super(-3) M HNO sub(3) solution. Initially, [Zn(H sub(2)O)(OH)] super(+) ( eta sub([Zn(OH)(H) sub(2)O)] super(+) = 1.25 eV) is adsorbed at the surface of the algae, which is built up of polysaccharides ( eta sub([glucose]) = 6.34 eV), before moving inside by the formation of a more stable complex with Phycocyanobilin2, which has similar hardness ( eta sub([Phycocyanobilin]) = 2.37 eV). The complex is stabilized by -52 195.48 eV mol super(-1) through the formation of two strong intramolecular hydrogen bonds (-OH...O = 163.54 pm; HOH...O = 129.71 pm). Density functional theory optimization corroborates a stable [Zn(H sub(2)O)(OH)] super(+)-Phycocyanobilin2 tetrahedral complex.