Dispersion of FeOOH on Chitosan Matrix for Simultaneous Removal of As(III) and As(V) from Drinking Water

Abstract

Bio-inorganic chitosan based spherical shaped beads were prepared by dispersing rod-shaped FeOOH nanoparticles into a chitosan matrix for the removal of pure As(III) and As(V) from aqueous media, such as drinking water. A homogeneous mixture of chitosan and ferric nitrate, ferric chloride was prepared respectively with or without oxalic acid. The mixture was added dropwise in to a NaOH bath, where iron salts reacted with NaOH to form FeOOH particles. The scanning electron microscopy (SEM) showed that rod shaped FeOOH particles were distributed homogenously in the chitosan matrix. Diffuse reflective UV-vis (DRUV) spectra revealed that hydrated iron oxide formed a complex with functional groups in chitosan. Adsorption of As(III) and As(V) on different iron salt based bead was found to be pH dependent. The bead prepared from iron nitrate showed better performance for arsenic removal from aqueous solution over the bead that was prepared using iron chloride salt. The bead prepared using chitosan and iron-FeOOH is known as a chitosan-iron oxyhydroxide (CFOH) bead. The CFOH beads were found to be more efficient in removing As(III) from the solution compared to As(V). The adsorption of As(III) and As(V) from aqueous solution on CFOH beads was studied under equilibrium conditions in the concentration range of 1 mg/L to 50 mg/L in the presence of 0.05 M NaNO₃ at pH 6.5 and 298 K temperature. The maximum adsorption capacity of the CFOH bead was found to be 5.4 mg/g for As(V) and 7.2 mg/g for As(III) using the Langmuir equation. The presence of sulphate, phosphate, and silicate in aqueous solution had no effects on adsorption of either As(III) or As(V) on CFOH beads but decreased significantly at pH> 8.

Keywords:

• chitosan
• iron
• arsenic
• adsorption