Abstract
The parametric statistical adsorption of chemically unmodified coconut shell powder (CSP) to adsorb iron (II) ions from aqueous solutions was examined in this work. It was observed that the adsorption capacity increased with increasing adsorbent dose, reducing adsorbate dose, increasing contact time, decreasing temperature and reducing particle size. As observed about one gram of the adsorbent was sufficient enough to remove 98 % iron (II) ions. A total contact time of about 40 minutes was sufficient for almost complete adsorption of the ions, while a pH of about 6.0 exhibited the maximum adsorption capacity. The sorption data were fitted into Langmuir, Freundlich, Temkin and the Dubinin-Radushkevich isotherms, fitted most with the Freundlich Isotherm model. The energy values obtained from the Temkin and Dubinin-Radushkevich isotherm model indicated high chemisorption phenomenon with the adsorbents. Investigation of some kinetic models confirmed that the adsorption of iron (II) ions using CSP was a pseudo-second order kinetic process, which further corroborates that chemisorption dominates the adsorption. Fourier Transform Analysis (FTIR) further established and justified the outcome of the study. The adsorption was parametrically justified statistically with Analysis of Variance (ANOVA) and Bonferroni-Holm Posthoc significance test. Conclusively, coconut shell proved strongly to be an effective and suitable adsorbent for removing iron (II) ions from aqueous solutions.
Highlights
Iron is present in two major forms in water; the soluble ferrous iron (Fe2+), or the insoluble ferric iron (Fe3+)
Ferrous iron in water is a clear and colourless solution, but on exposure to air becomes oxidized to the insoluble reddish brown ferric iron known as rust
Oxidation rate of ferrous to ferric iron seems slow, allowing ferrous iron to remain in aerated water for some time
Summary
Iron is present in two major forms in water; the soluble ferrous iron (Fe2+), or the insoluble ferric iron (Fe3+). Thermodynamics revealed a negative Gibbs free energy, which indicated the adsorption of Fe2+ was spontaneous and studied the removal of copper (II), iron (III) and lead (II) In another effort, Agbozu and Emoruwa [15] investigated adsorption on coconut husk. Cd>Fe>Cr>Cu> Pb. A maximum contact time of about 20 be suitable for the Fe (III) adsorption and the process minutes was required to obtain about 84.9 – 97 % removal followed pseudo-second order kinetics. The kinetics of the batch followed the non-linear pseudo first order, and the adsorption of iron II ions in aqueous solution using CSP experimental data fitted with varying degrees into the with the fitting of the adsorption process to an isotherm. The adsorbent was filtered using a funnel and filter paper, the filtrate was put in a spectrophotometer and the concentration measured and recorded
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