A novel and efficient method for synthesizing reduced charge montmorillonite

Layer charge (LC), a paramount physiochemical characteristic of montmorillonite (Mt), has been garnered considerable attention on its regulating and impact on modified Mt products. Incorporating small cations such as Li⁺ into the tetrahedral/octahedral sheets of Mt, or employing acid treatment, are feasible methods to reduce its LC. However, conventional techniques for producing reduced charge Mt (RC-Mt) often suffer from prolonged processing times, complex procedures, and high consumption of water and energy. Moreover, the formation mechanisms of RC-Mt remain inadequately understood. To address these challenges, this study proposes a novel and efficient method combining dry lithiation and microwave irradiation to prepare RC-Mt, and compares it with a conventional acid treatment. The research also explores the applications of RC-Mt, focusing on organic modification and the evaluation of adsorption performance. It was found that the cation exchange capacity (CEC) of RC-Mt diminished with increasing microwave power and time, LiCl dosage, HCl concentration, acidification duration and temperature. It has been demonstrated that the dry lithiation & microwave method significantly reduces the total preparation time of RC-Mt to 12 min while eliminating the generation of wastewater. The pivotal advantages of this approach include its efficiency, time-saving, and minimal environmental impact. Analytical techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance spectroscopy (SSNMR) revealed that microwave irradiation facilitates the migration of Li⁺ into the hexagonal cavities and octahedral vacancies of the Mt tetrahedral sheets. Additionally, acid treatment results in the dissolution of octahedral cations from Mt. The modified products of RC-Mt with lower CEC, exhibited enhanced adsorption of perchlorate ions (ClO₄⁻). These findings offer significant insights into the modification of Mt and its potential for advanced technological applications, presenting a promising avenue for future research.