The adsorption of Cr (III) ion from aqueous solution using orange peels as adsorbent was investigated using batch equilibrium technique. The research is significant as it's aimed at investigating the suitability of orange peel, a waste product as adsorbent for the adsorption of Cr (III) ions from aqueous solution. Orange peel as an adsorbent is resource-saving and has an environmental friendly behavior. Adsorption envelope experiment was conducted using a constant Cr (III) ion concentration of 0.1 M, adsorbent dose of 2.5 g and a temperature of 30˚C at varying solution pH of 2, 4, 7, 9 and 12 respectively with pH of 2 having the highest adsorption and therefore it was selected for use in the adsorption isotherm experiment. Adsorption isotherm experiment was conducted at varying temperatures (30˚C, 40˚C, 50˚C, 60˚C), concentration (0.1 M, 0.2 M and 0.3 M) Cr(NO3)3. Thermodynamic parameters such as ∆G, ∆H, ∆Hr, ∆A, and ∆S were calculated from the experimental data which showed that the adsorption process is feasible, spontaneous and followed physisorption mechanism 9H 2 O and adsorbent dosage (1 g, 1.5 g and 2 g) respectively. The experimental results were tested using Langmuir, Freundlich, Linear and Temkin adsorption isotherm models. The experimental data best fitted the Freundlich isotherm model. The experimental results revealed the suitability of orange peel which is a waste product as effective adsorbent for the sorption of chromium (III) ions from aqueous solution.

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In this present work, a novel method for synthesis of palm kernel shell activated carbon was established using DES (choline chloride/urea)/H3PO4 as the activating agent. The pore characterization, morphology, and adsorption properties of the activated carbons were investigated. The activated carbon samples made from the same feedstock at two pyrolysis temperatures (500 and 600 °C) were compared for their ability to adsorb Pb(II) in aqueous solution. The results demonstrated that the production of the activated carbon and adsorptive properties were significantly influenced by the pyrolysis temperature and the ratio of precursor to activating agent. DES/H3PO4 activated carbon (having surface area 1413 m2/g and total pore volume 0.6181 cm3/g) demonstrated good Pb(II) removal. Although all the tested activated carbon samples adsorbed Pb(II) from aqueous solution, they demonstrated different adsorption capabilities according to their various properties. The pyrolysis temperature, however, showed little influence on the activated carbon adsorption of Pb(II) when compared to the impregnation ratio. Their good desorption performance perhaps resulted from the porous structure.

Heavy metal contents of some crops and farm soil irrigated along the Bindare stream in Chikaji Zaria were investigated. The results of the analysis indicate that the crops contained substantial amount of heavy metals (Pb, Cr, Zn and Fe) compared to similar crops irrigated far distance from the stream. The concentration of the heavy metals (Zn, Cr and Fe) in the crops and the farm soil were found to be below the FAO/WHO safe limit, while the concentration of Pb was higher than the FAO/WHO safe limit. This suggest that the crops and the farm soil along the stream were contaminated by these heavy metals as the stream receives industrial waste discharges. Contamination factors and Geoaccumulation index for Pb, Cr, Zn and Fe in the areas under investigation were carried out. The results revealed that the soils are currently polluted with Pb and Zn.

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