Synthesis and characterization of L-tryptophan containing microbeads for removal of dimethyl phthalate from aqueous phase

Poly(ethylene glycol dimethacrylate-N-methacryloyl-L-tryptophan methyl ester) [poly(EGDMA-MATrp)] beads (average diameter = 106–300 μm) were synthesized by copolymerizing of N-methacryloyl-L-tryptophan methyl ester (MATrp) with ethylene glycol dimethacrylate (EGDMA). The usability of newly synthesized material for the removal of dimethyl phthalate (DMP) from aqueous phase was investigated. The poly (EGDMA-MATrp) beads were characterized by N2 adsorption/desorption isotherms (BET), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and swelling studies. Initial concentration, pH, contact time and temperature effects on the adsorption of DMP from aqueous solutions were analyzed. An optimum adsorption capacity of 237.3 mg g−1 for DMP was obtained at 25 °C. The present adsorption process obeyed pseudo-second-order kinetic model. All the isotherm data can be fitted with both the Langmuir, and the Dubinin–Radushkevich isotherm models with high correlation coefficients. Thermodynamic parameters ΔH = 2.398 kJ mol−1, ΔS = 65.76 J K−1 mol−1, and ΔG = −17.20 kJ mol−1 to −18.57 kJ mol−1 with the rise in temperature from 25 °C to 45 °C indicated the adsorption process was endothermic and spontaneous. The DMP adsorption capacity did not change after 10 batch successive reactions, demonstrating the usefulness of the beads in applications.

► L-Tryptophan containing beads were prepared for dimethyl phthalate (DMP) removal. ► The beads showed a high adsorption capacity (up to 237.3 mg/g) to remove DMP. ► Adsorption occurred with π–π interactions. Isotherm data fitted with the Langmuir and the Dubinin–Radushkevich isotherm models. ► The beads were regenerated easily and reused for DMP adsorption.