Ethidium bromide adsorption on pyrophyllite nanoclay: Insights from batch, thermodynamic, kinetic, and recyclability studies and optimization through response surface methodology

Abstract

The efficient removal of Ethidium Bromide (EB), a toxic yet widely used chemical in biochemical industries and laboratories, is crucial to avoid its detrimental effect on human health, aquatic life, and the environment. One effective method is adsorption onto inert surfaces, but the choice of adsorbents is critical for the success of the removal protocols, primarily because of the limitations such as low adsorption capacity, high cost, limited availability, and a lack of understanding of the adsorption mechanism. In this work, Pyrophyllite Nanoclay (PNC), a naturally abundant aluminosilicate is explored as a promising adsorbent for EB. The adsorption process follows the Freundlich isotherm and displays pseudo-second-order kinetics. Under the optimized condition, PNC demonstrates nearly quantitative adsorption of EB and the maximum adsorption efficiency obtained from experiment was 6.53 mg/g (0.017 mmol/g) at room temperature under optimized condition. Through thermodynamic, kinetic analysis coupled with characterization techniques, the mechanism of adsorption is proposed. The adsorbent proves to be reusable, maintaining its performance over three cycles. The utility of the process is further validated and optimized using Response Surface Methodology (RSM). The present work focuses on the performance of PNC as adsorbent and elucidates distinctive surface adsorption mechanism (in comparison to other nanoclays), thus emphasizing the significance of structural, experimental, mechanistic and validation studies in choosing the right adsorbent for the removal toxic chemicals.