ADSORPTIVE REMOVAL OF Pb2+, Cd2+, AND Cr6+ FROM AQUEOUS SOLUTION USING CACTUS OPUNTIA

Abstract

Industrial processes regularly discharge harmful metal compounds into the environment. Even in low quantities, hazardous metals in the environment can affect humans and other creatures. Toxic metals cannot breakdown into innocuous end products, thus they can collect in living bodies and become concentrated throughout the food chain.The main objective of this study is to investigatesorption behavior of Cactus Opuntiaficus-indicus (OFI) powder in the removal of selected metal ions (Cd2+, Cr6+and Pb2+) from aqueous solution using adsorption techniques. Characterization of the prepared adsorbent was performed using only Fourier Transform Infrared spectroscopy (FTIR) to identify the functional groups of the adsorbent before and after the adsorption and the metal contents were analyzed by Flame Atomic Absorption Spectroscopy (FAAS). Batch experiments were carried out to determine the effect of pH, initial metal ions concentration, adsorbent dose, adsorbent particle size, contact time,andagitation speed on the adsorptive removal of the selected metals by the prepared adsorbent.The FTIR assessment revealed that the hydroxyl (-OH),carboxyl(-COOH),Ester group –COO- and carbonyl (C=O), functional group intensities shifted following the adsorption of the selected metal ions, demonstrating that Opuntiaficus-indica successfully adsorbs metal ions.After optimization, both the Langmuir and Freundlich isotherm models were used; nevertheless, the Langmuir isotherm model R2valueis equal to 0.999,0.999and 0.998 ,for Pb2+,Cd2+and Cr6+respectively .Soit fits the experimental data better. On the other hand, pseudo-first and pseudo-second-order kinetic models were also evaluated. The experimental data fitted with the pseudo-second-order kinetics modelwith R2values0.9997,0.9997and 0.9999 for the adsorption of the selected heavy metal ions byOFI.The percentage removal was found to be99, 98.1, and 99.1% for Pb2+, Cd2+, and Cr6+, respectively,by OFI, at pH = 10 (for Pb2+and Cd2+) and 2 for Cr6+),initial concentration of 25 mg/L, dose 0.5 g, contact time 120 minutes,and particle size 300 μm. The batch adsorption experiments showed that the adsorbent could remove the majority of the Pb2+, Cd2+, and Cr6+ from the aqueous solution under optimal conditions.Based on the results observed in the present study, OFI can be taken as a promising adsorbent for the removal of heavy metals from aqueous solution.The adsorption of Pb2+, Cd2+ and Cr6+.using OFI from rale sample or waste water was conducted and the percent of adsorption result obtained were 97.1,92.68 and 97.3 for Pb2+,Cd2+ and Cr6+ respectively.The result confirming Cactus Opuntia’s effectiveness in waste water sample selected heavy metal ions removal .