Parametric Studies, Kinetic and Isotherm Modeling of Methyl Orange Adsorption by Chitosan - MIL-101 (Fe) - Polyethyleneimine Beads

Adsorbent beads composed of Chitosan (CS), MIL-101 (Fe), and Polyethyleneimine (PEI) were synthesized for Methyl Orange (MO) adsorption. Parametric studies testing the effects of pH and number of adsorption and desorption cycles on percent MO removal showed the beads’ good performance across a wide range of conditions. A percent MO removal of at least 93% was maintained from pH 2 to pH 9 with a maximum percent removal of 98.6% obtained at pH 3. In addition, the beads remained functional for at least 5 cycles of adsorption and desorption with a percent MO removal of 98% across the cycles. Kinetic modeling was performed and a pseudo-second order kinetic model with an R 2 of 0.981 was obtained implying chemisorption as the rate limiting step. Adsorption equilibrium data for MO were best fitted into the Sips isotherm model which suggests that adsorption occurs on a heterogeneous surface. From the Sips isotherm model, the maximum adsorption capacity was determined to be 1253.44 mg/g, highlighting the viability of CS – MIL-101 (Fe) – PEI beads as an adsorbent for wastewater treatment.