Application of Preformed Floc Adsorbents in the Removal of Acid Dye from an Aqueous Solution

Abstract

Preformed flocs prepared by using coagulants, i.e. Fe₂(SO₄)₃, MnSO₄.4H₂O, and MnCl₂.4H₂O, were applied as adsorbents for the decolorization of an aqueous C.I. Acid Red 1 dye solution. In order to determine the decolorizing efficiency of different adsorbents, kinetic and equilibrium studies were carried out at the optimum pH. Excellent color removal of 87 % was obtained with Fe₂(SO₄)₃ at pH 4, good color removal of 65 % was achieved with manganese sulfate at pH 10, and moderate color removal of 58 % was obtained with manganese chloride at pH 10, at an optimum sorbent dose of 500 mg L⁻¹ and an equilibrium contact time of 15 min. The sorption data of the equilibrium studies fitted well to the Langmuir isotherm, stating the occurrence of monolayer formation in the adsorption process of dye color removal. The maximum adsorption capacities of ferric sulfate and manganese sulfate are 47.619 and 23.474 mg g⁻¹, respectively. The data of the kinetic studies fitted well to the pseudo‐second‐order equation, stating that chemisorption is the rate‐limiting step.