Kelechi E. Onwuka1*, Okechukwu C. Atasie2, Solomon E.O. Okereke1, Nnamdi E. Enenwa1 and Godwin I. Ogbuehi1

In this study, trimethyl phenyl ammonium cation (TMPA+) intercalated bentonite was used as an adsorbent for adsorptive removal of seven heavy metal ions namely: Pb (II), Zn (II), Cu (II), Hg (II), Cr (II), Co (II) and Cd (II) in aqueous solution via batch adsorption process. The developed adsorbent, ab initio has been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The operational parameters evaluated on the adsorption efficiency were solution pH, initial metal ions concentration, temperature, adsorbent dosage, and contact time. The adsorption of Pb (II), Zn (II), Cu (II), Hg (II), Cr (II), Co (II) and Cd (II) ions were found to have attained equilibrium positions in 120 min for the concentration range tested, respectively. Two generally applied linearized adsorption isotherm models; Langmuir and Freundlich tested, when compared, revealed that Langmuir isotherm fitted well to the experimental data judging from the higher correlation coefficient values (R2) and lower values of the error functions (chi-square (χ2), the sum of square error (ERRSQ/SSE) and the sum of absolute error (EABS)) with monolayer adsorption capacities of 17.66, 21.12, 14.64, 14.98, 16.60, 13.81 and 15.50 mg/g for Pb (II), Zn (II), Cu (II), Hg (II), Cr (II), Co (II) and Cd (II) ions, respectively. Adsorption kinetic models investigated by pseudo-first-order and pseudo-second-order showed the conformity of pseudo-second-order model to the process of adsorption as informed by the higher values R2 and Adj, R2, maximum log-likelihood and smaller ERRSQ/SSE, χ2, Akaike information criterion (AIC), Bayesian information criterion (BIC), and Hannan-Quinn information criterion (HQIC). Result from kinetic data revealed the adsorption mechanism of Pb (II), Zn (II), Cu (II), Hg (II), Cr (II), Co (II) and Cd (II) ions onto Bt-TMPA as a chemical adsorption.

Keywords: Adsorption, isotherm, heavy metals, kinetics, organoclay.

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