Removal of Ni2+ and Pb2+ IONS from Aqueous Medium Using Unmodified and 4-Aminophenol Modified Red Onion Skin Extract

The extraction of Ni2+ and Pb2+ ions from aqueous medium using unmodified (ROSE) and the 4-aminophenol modified red onion skin extract (ROSEDS) has been successfully achieved. Cold solvent extraction technique using a 50:50 acetone/water ratio was used for extraction of the red onion skin at 125 µm mesh size. The metal concentrations were determined using Atomic Absorption Spectrometry technique. Optimum percentage removal of the metal ions was achieved at pH 6.26 for Ni2+ (89.40 % for ROSE and 97.60 % for ROSEDS) and pH 7.57 for Pb2+ (80.10 % for ROSE and 82.56 % for ROSEDS). Optimum adsorption capacities of ROSE and ROSEDS for Ni2+ were 6.30 mg/g and 7.10 mg/g respectively; while for Pb2+ ions, values obtained for ROSE and ROSEDS were 5.87 mg/g and 6.34 mg/g respectively. Varying adsorbents dosage at fixed metals ion concentration yielded optimum percentage removal of 89.90 % and 97.90 % for Ni2+, while 86.85 % and 90.80 % for Pb2+, using ROSE and ROSEDS, respectively. Adsorption capacities of the adsorbents varied inversely with adsorbent dosages. In general, 4-aminophenol modified red onion skin extract (ROSEDS) gave comparatively, better results for the extraction of Ni2+ and Pb2+ ions from aqueous medium; relative to the unmodified red onion skin extract (ROSE). Additionally, extraction of Ni2+ ions gave higher percentage removal values in both adsorbents when compared to extraction of Pb2+ ion under similar conditions. This result has been attributed to differences in their ionic radii. REVIEW ARTICLE | April 4, 2023