Kinetic studies of adsorption of Fe(III) from aqueous solution by untreated and alkali-treated rice straw

Abstract

Modifications of rice straws surfaces by sodium hydroxide (NaOH) were carried out in order to study the effects of this on the surface functional groups properties. Comparison was made between untreated and alkali-treated rice straws on the removal of Fe(III) from aqueous solution. In this study, four characterizations of raw rice straw have been conducted. The morphological characteristics by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Analysis (EDXA)the functional group present in the rice straw by Fourier Transform Infrared (FTIR) spectroscopy and the X-ray Diffraction (XRD). The result of Scanning Electron Microscopy (SEM) also shows that rice straw is a porous material. Rice straw contains on –OH functional group that can bind with metal ions. To be able to enhance the sorption capacity of rice straw in metals, removing from waste water, alkali treatment should be done. This shows that rice straw can be used as adsorbent for ferric ions removing from wastewater.The effect of pH, sorption kinetics and isotherms were studied in batch experiments. The good correlation coefficient was obtained from pseudo second-order kinetic model, which agreed with conception as the rate-limiting mechanism. Sorption isotherm test showed that equilibrium sorption data were better represented by Temkin model. The highly efficient, low cost and the rapid uptake of Fe(III) by untreated (RS) in comparison with alkali-treated (MRS) rice straws, indicated that it could be an excellent alternative for the removal of ferric ions by sorption process.