Biosorption of Fe (II) and Cd (II) ions from aqueous solution using a low cost adsorbent from orange peels

The peels from orange are less expensive biomaterials with excellent adsorption capacities. Orange peels were carbonized at 450 ºC, purified, activated with orthophosphoric acid and modified with citric acid to obtain Modified and Activated carbon which were used as low cost adsorbent to adsorb Cd(II) and Fe(II) metal ions. The effects of initial metal ions concentration; pH; temperature; contact time; and adsorbents dose on the removal of metal ions were investigated. The maximum adsorption occurs at 26 ºC and decreased with increase in temperature while optimum adsorption took place at pH of 6. Both the Fe-MOP and Fe-AOP system attained equilibrium in 60 minutes but Cd-MOP & Cd-AOP attained equilibrium at 45mins. The enthalpy 0f adsorption ranged from 2.48 KJ/mol to 14.418 KJ/mol and the entropy of adsorption ranged from -3.53 KJ/mol to 41.07 KJ/mol for both adsorbents (MOP and AOP). The kinetic studies showed that the adsorption process fitted well for pseudo-second order rate expression. Both MOP and AOP has much affinity for Fe(II) uptake than Cd(II) ion and the adsorption data fitted most into Freundlich but the highest adsorption capacity of 0.895 was obtained from Temkin. The presence of hydroxyl, alkyl, ether and aldehyde groups was confirmed by Infrared while the SEM shows porous surface characteristics suitable for adsorption.Keywords: Modified Orange peel, adsorbent dose, Isotherm, adsorption, Activated Orange pee