Adsorption of phenol by a Moroccan clay/ Hematite composite: Experimental studies and statistical physical modeling

Water pollution by phenolic compounds is considered a primary environmental concern. The adsorption of phenol on iron-modified clay and its mechanism were evaluated in this study. A new hybrid material, "Clay-Iron oxide," has been synthesized for its possible use in phenol removal from wastewater. Textural and chemical properties of this new composite have also been assessed using a variety of techniques such as XRD, XRF, SEMEDX, FTIR, and BET. On the other hand, phenol adsorption performance has been studied in terms of pH, temperature, and initial concentration. Theoretically, the phenol adsorption onto modified clay was satisfactorily modeled with pseudo-second-order kinetics and the Langmuir isotherm; the maximum phenol adsorption capacities, obtained with the Langmuir model, are 15.24, 17.55, 20.24, and 20.10 mg/g at 303, 313, 323, and 333 K, respectively. Furthermore, five advanced statistical physics models were adopted to understand the adsorption mechanism better. The combination of experimental and modeling approaches revealed that: i) the present material is competitive compared to other adsorbents, ii) phenol molecules interact with clay/iron oxide functional groups via several mechanisms, iii) the number of phenol molecules adsorbed per site increases with temperature, iv) phenol adsorption process is spontaneous, physisorption and endothermic, and v) Iron increases the phenol removal efficiency. Thus, the novelty of this research paper lies in the phenol adsorption mechanism study based on the spatial and energetic properties, the determination of the adsorption process effect on the adsorbent, and finally, the assessment of the iron-modified clay's efficiency in removing phenol from wastewater.