Study on adsorption of herbicide onto functionalized cellulose extracted from Juncus acutus L. plant: Experimental results and theoretical modeling

Static equilibrium measurements were performed for the study of linuron adsorption on amine functionalized cellulose fiber extracted from Juncus acutus L. plant (Smar) at pH 7. We have noticed that the retention capacities of loaded aminated smar support were 64.8, 51.8, 38.9 and 32.3 mg/g at 20, 40, 60 and 80 °C, respectively. While for the non saturated support, these capacities were 31, 28.5, 26.4 and 23.5 mg/g at 20, 40, 60 and 80 °C, respectively. The obtained adsorption isotherms cannot be evaluated by using the Freundlich or Langmuir equations. New equation has been derived by making use of the grand canonical ensemble in statistical physics and some working hypotheses. The characteristic model parameters of the adsorption isotherm such as the number or fraction of adsorbed molecule(s) per site, n, the number of receptor sites per gram of adsorbent, NM, and the energetic parameter, w, were estimated for the studied systems by a non-linear least square regression. The calculated curves fit well to the experimentally obtained isotherms and the parameters of the model can be used for the characterization of the herbicide–adsorbent interactions. Thermodynamic parameters of adsorption process, i.e., entropy, Gibbs free energy and internal energy were computed and their negative values indicate that the adsorption was exothermic and favorable nature.