Adsorption of ferrous iron on the lepidocrocite surface

Abstract

This study explored the ferrous iron adsorption capacity of three synthesized lepidocrocites as well as their morphology and surface area. Their morphologies were observed using scanning electron microscopy (SEM) and their surface areas were measured by BET isotherm techniques using nitrogen gas at the liquid nitrogen temperature. The adsorption capacities of the three distinctive lepidocrocites were measured and the data were processed by multiple regression technique to obtain the adsorption constants in the proposed model. The microphotographs of the lepidocrocites revealed that lepidocrocites could have an acicular shape as well as the shape of agglomerated flocs. The surface areas of the synthesized lepidocrocites in this study varied widely from 48.98 m(2) g(-1) to 150.28 m(2) g(-1). Adsorption capacities of three distinctive lepidocrocites for ferrous iron were investigated at four different pH levels. It was observed that there was no correlation between the BET surface area and adsorption capacity. The sites accessible to nitrogen gas might not be available to ferrous iron in water. An adsorption model based on the Freundlich equation was built to predict the effect of pH and the equilibrium concentration of ferrous iron in water. Multiple regression of data revealed that the amount of ferrous iron adsorbed on the unit weight of lepidocrocite,vas proportional to the 0.57 power of the ferrous iron concentration and inversely proportional to the 0.66 power of the hydrogen ion concentration.