Investigation of adsorption behavior of eriochrome black T on mesoporous silica aerogel: experimental and molecular modeling studies

Remediating organic dye pollution remains a concern in contemporary water management practices. Developing low-cost and high-surface-area adsorbents synthesised by nanotechnology to eliminate organic dyes is an essential issue in water treatment. Recently, silica aerogels, a kind of nanomaterials, have been investigated as adsorbents due to their high porosity, high surface area, and low cost. This study aimed to synthesize and characterize tetraethoxysilane (TEOS)-based silica aerogel (SA) to assess its efficacy in removing eriochrome black T (EBT), which is a potentially hazardous dye. Based on adsorption studies, the optimal adsorption conditions were found to be 0.2 g adsorbent dosage, pH 2, 120 min contact time, 10 mg L⁻¹ initial EBT concentration, and a temperature of 40 °C. The adsorption data were best fitted with a remarkably high correlation coefficient of R² = 0.999 in the pseudo-second-order model. According to the results of the adsorption isotherm model analysis, the R² values for the Temkin, Freundlich, and Langmuir models were determined to be 0.971, 0.935, and 0.954, respectively, particularly at the optimally determined temperature of 40 °C. Thermodynamically, the process is exothermic and spontaneous. In addition to experimental studies, the WB97x-D level of the Density Functional Theory was used to elucidate the detailed adsorption mechanism between SA and EBT in the water phase. The experimental results are consistent with the computational parameters describing the primary adsorption mechanism, including physisorption processes via electrostatic attraction, van der Waals interactions, and hydrogen bonding.

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