Adsorption and recovery of nonylphenol ethoxylate on a crosslinked β-cyclodextrin-carboxymethylcellulose polymer
A study of adsorption/recovery of nonylphenol 9 mole ethoxylate (NP9EO) on a crosslinked β-cyclodextrin-carboxymethylcellulose (β-CD-CMC) polymer was carried out by ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopies. The adsorption was performed in mixtures containing 500 mg of the β-CD-CMC polymer and aqueous NP9EO solutions at concentrations 12–82 mg/L, whereas the recovery of NP9EO was effectuated by shaking the β-CD-CMC polymer loaded with methanol. The assays were made at 25°C and atmospheric pressure under agitation. The results have shown that the adsorption is a rapid process and the β-CD-CMC polymer exhibits a high NP9EO adsorption capacity of 83–92 w% (1.1–6.8 mg NP9EO/g β-CD-CMC polymer) dependent of the initial NP9EO concentration in liquid phase. This adsorption may involve the formation of an inclusion complex β-CD-NP9EO and a physical adsorption in the polymer network. The adsorption equilibrium measurements, which were analyzed using the Langmuir isotherm, have indicated a monolayer coverage and the homogeneous distribution of active sites at the surface of the β-CD-CMC polymer. Moreover, the negative value obtained for the free energy change (−13.2 kJ/mol) has indicated that the adsorption process is spontaneous. In parallel, the β-CD-CMC polymer exhibited a high NP9EO recovery efficiency of 97 w% that may occur through a decrease of binding strength between β-CD-CMC polymer and NP9EO. Together, these results suggest that the β-CD-CMC polymer could constitute a good adsorbent for removing nonylphenol ethoxylates from wastewater due to its high adsorption capacity and non-toxic character of β-CD and CMC to environment.
Keywords: adsorption, crosslinked β-cyclodextrin-carboxymethylcellulose polymer, FTIR spectroscopy, Langmuir isotherm, nonylphenol ethoxylate, recovery, UV-VIS spectroscopy