Population Genetics of the Nile tilapia ( Oreochromis niloticus) from East African Lakes and its Implications for Capture and Culture Fisheries in the Nile Basin Region

Abstract

This study describes an effective method for the removal of nickel ions (Ni2+) from the water by repetitive absorption and regeneration (desorption) cycles using immobilized adsorbents. Polyethyleneimine (PEI) based epoxy coated gauzes having the high density of active sites were prepared as immobilized adsorbents. The adsorption of Ni2+ by the PEI based epoxy coated gauze was confirmed by the analysis of the immobilized surface using X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The effects of type of the cross-linking agents and PEI/cross-linker molar ratio on the adsorption efficiency were studied. The surface wettability of the immobilized adsorbent was evaluated using dynamic contact angle measurements. The adsorption behaviors can be fitted with the Freundlich isotherm and the pseudo-second-order kinetic model. The adsorption of the Ni2+ was studied at various treatment time and pH. Because of the porous structure and large surface area of the gauze based adsorbent, together with the large amount of oxygen atoms and amine groups on the molecular chain of adsorbent, the optimized adsorption capacity for Ni2+ can reach 650 mg/g. More importantly, the adsorbent has retained its adsorption capability even after repeated adsorption-desorption cycles.