Mn2+ ions retention onto agriculture waste: a statistical design analysis, estimation of equilibrium and kinetic parameters

This paper describes the adsorption of Mn2+ ions from aqueous solution by the Iranian oak-fruit shell as low-cost adsorbent. The effect of various parameters such as pH of solution, contact time, initial Mn2+ concentration and adsorbent weight for the adsorptive retention process were investigated. SPSS software was employed for prediction and investigation of factor importance in determining of removal ratio of Mn2+. According to Beta-value the importance order of factors is: pH of solution, adsorbent weight, initial Mn2+ concentration and time, respectively. In process optimization, removal ratio of Mn2+ was achieved as 73.59% with a pH of 5.0, contact time of 210 min, initial Mn2+ concentration of 10 mg/L, and adsorbent weight of 2.5 g. Also, the obtained results from this study show the good adaptation between experimental and prediction values of removal ratio of Mn2+.Equilib- rium studies show that Mn2+ adsorption data follow Freundlich model. Pseudo-second-order kinetic model agrees very well with the experimental data. The desorption and regeneration studies have proven that adsorbent can be potentially reused for further adsorption process. Fourier transform infrared spectroscopy (FTIR spectra) and scanning electron microscope (SEM) were used to characterize the biosorbent.