Copper (II) adsorption capacity of a novel hydroxytyrosol-based polyacrylate

A novel hydroxytyrosol-based polyacrylate polymer material (pAcHTy) endowed with metal ion adsorption ability was obtained by free radical polymerization of a monomer containing a hydroxytyrosol precursor (tyrosol). Hydroxytyrosol (HTy) is the main natural polyphenolic compound with antioxidant activity occurring in virgin olive oil and in olive oil wastewaters. pAcHTy showed a good chelating activity with respect to Cu²⁺ ions, especially at pH 6 where short equilibrium times and high adsorption capacity were observed (146 mg/g). From thermodynamic parameters, it has been found that the sorption process was spontaneous at low temperature and exothermic in nature. The adsorption process has been studied by employing three simplified kinetic models, including a pseudo-first-order equation, pseudo-second-order equation, and intraparticle diffusion equation. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients, for each kinetic model, were calculated and discussed. It was shown that the adsorption of Cu²⁺ ions could be described by the pseudo-second-order equation, suggesting that the adsorption process is presumable a chemisorption. The pAcHTy polymer could find an important application in the medical field, particularly in chelation therapy as well as in the wastewater and drinking water treatment plants.