Removal of Phthalate Esters from Aqueous Solution by Molybdate Impregnated Chitosan Beads

Abstract

The removal of phthalate esters (PAEs) by molybdate impregnated chitosan beads (MICB) in an aqueous solution was studied. The adsorption isotherms of PAEs by MICB were well described by Freundlich isotherm equations. The results of kinetic experiments indicated that of the six PAEs studied diheptyl phthalate (DHpP) was the most efficiently adsorbed (3.01 mg/g). PAEs were well adsorbed by MICB in both the batch and continuous systems. In terms of recovery efficiency, 92.5% DHpP was recovered from MICB following shaking in a mixture of methanol and water (v/v = 4/6). The recovered MICB was reusable as an adsorbent for a minimum of 15 cycles in the batch tests. Different water environments were simulated by varying the temperature, pH, Ca²⁺, and NaCl of the aqueous solutions and the effects on PAE absorption evaluated. The amount of PAE adsorbed by MICB decreased as the temperature increased, indicating an exothermic reaction, but coexisting pH, NaCl, and Ca²⁺ did not affect the adsorption efficiency. The efficiency of an MICB-packed column in treating industrial wastewater containing di-(2-ethylhexyl) phthalate (DEHP) was comparable to that obtained in the laboratory continuous system, indicating the potential of this system for the treatment of industrial wastewater. This is the first report to propose MICB as an efficient sorbent for PAE removal.