Enhanced Removal of Nickel from Aqueous Solutions Using Carbonated Moroccan Clay: Characterization, Adsorption and Thermodynamic Studies

Water pollution has become a major global environmental challenge, mainly due to human activities, industrialization and agricultural practices. Among pollutant, heavy metals accumulate in the environment, leading to contamination of valuable water resources. Exploitation mineral resources as clays in the removal of heavy metals from polluted water presents a promising concept for efficiently eliminating these harmful substances, offering an attractive low cost option for environmental remediation. For this reason, the present research aims to explore the adsorption capacity of Moroccan natural rich carbonate clay (RC) sampled from Fez region in North-East Morocco, as a naturally abundant and low environmental impact adsorbent for efficiently eliminating a highly toxic nickel (Ni) from water sources. The high carbonate content limits the valorization of this clay in other fields as a building material or in the ceramics industry. The clay underwent detailed characterization of its physical and chemical properties using different analytic techniques (XRF, TGA/DTG, FTIR, XRD, SEM, and EDX). To establish the optimal operating conditions for removing nickel using RC clay, a series of batch adsorption tests were conducted. These experiments explored the impact of the temperature, Ni initial concentration, contact duration, adsorbent dose, and initial ph. Additional investigations into kinetics, equilibrium, and thermodynamics were performed to enhance comprehension of the adsorption mechanism and to identify the optimal adsorption conditions. Considering error function and correlation coefficient values, the pseudo-second order model best described the kinetic data, implying a chemisorption-based process. Moreover, the examination of adsorption isotherm results demonstrated the isotherm of Sips as the most suitable fitting model, revealing a maximum adsorbed amount of 59.16 mg/g. Evaluation of thermodynamic factors revealed the endothermicity, favorability, and spontaneity of the adsorption process. The study clearly highlights the potential value of this clay in water treatment.