Adsorption of Diuron from aqueous solution onto commercial organophilic clay: kinetic, equilibrium and thermodynamic study

Due to their abundance in nature, clays have been frequently studied in the adsorption of different emergent contaminants, since they have good efficiency and low cost. Therefore, the present study aimed to evaluate the performance of commercial organoclays as an adsorbent in the environmental remediation of wastewater containing the herbicide Diuron. The clay was characterized by the techniques of N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and point of zero charge. In the batch adsorption experiments it was verified that the adsorption kinetics is ruled by the pseudo-second-order model (R2 > 0.97), and the adsorption equilibrium study at different temperatures (298, 302 and 308 K) showed that the non-linear models of Langmuir (R2 > 0.99) and Freundlich (R2 > 0.98) were those that present better adjustments to the experimental data. In addition, the adsorption capacity in monolayer (qmax) was 44.24 mg g-1, being higher or comparable to several works reported in the literature. As for the thermodynamic adsorption study, it was possible to infer that the process is spontaneous (ΔG°ads < 0) and endothermic (ΔH°ads = 71.58 kJ mol-1) in the temperature range studied. As far as the regeneration study was concerned, the maximum desorption capacity, 26.59 mg g-1, was obtained from the use of ethanol as eluent at 298 K.