Interfacial adsorption behavior of amine-functionalized MCM-41 for Mo(VI) capture from aqueous solution

Given the environmental and ecological risks posed by wastewater bearing molybdenum, the characteristics and microscopic interactions of existing silica-based adsorbents have not been thoroughly investigated, highlighting the need to enhance the porosity and chemical interactions of these materials. Considering the effectiveness of amino groups in binding metal oxyanions, this study investigates the adsorption performance and mechanism of amino-functionalized MCM-41 for Mo(VI), with the goal of efficiently remediating Mo-contaminated wastewater. MCM-41 modified by amino group retains its original structure and mesoporous characteristics while featuring a positively charged surface and chemically bonded amino groups. When employed to treat Mo(VI)-containing solutions, adsorption equilibrium is attained within 20 min, adhering to pseudo-second-order kinetics, characterized by a high R² value of 0.9999, indicating a predominantly chemisorptive method. Thermodynamic evaluation offers uniform single-layer adsorption of specific ions onto the adsorbent interface. It demonstrates the nature of the adsorption method being spontaneous and fits the Langmuir model. A maximum of 242.33 mg/g of adsorption capacity was achieved. Spectroscopic characterization confirms that charge attraction, hydrogen bonding, and coordination are the primary driving forces behind the method of adsorption. Density Functional Theory (DFT) results further support the advantageous role of two-tooth chelation between amino group and silanol groups in the Mo(VI) adsorption mechanism. This study provides information on adsorbent design and the control of Mo(VI)-containing aqueous solutions by confirming the substantial promise of amino modified mesoporous silica with suitable pore configurations for treating Mo(VI)-containing solutions.