Effective adsorption of bisphenol A from water using cationic surfactant-modified natural kaolin minerals

Abstract

The utilization of natural clay minerals for the adsorption of endocrine-disrupting chemicals (EDCs) presents a cost-effective and environmentally friendly approach. However, the hydrophilic nature of clay minerals' surface limits their efficacy in removing these hydrophobic pollutants. To overcome these limitations, this study employed two cationic surfactants, cetylpyridinium chloride (CPC) and cetyltrimethylammonium chloride (CTAC), to modify kaolin minerals to enhance their capacity to adsorb a specific type of EDCs, bisphenol A (BPA), and its analogs. The experimental results validated that the surfactant-modified kaolin exhibited remarkable efficiency in removing BPA from water. The equilibrium adsorption capacities of CPC-K and CTAC-K for BPA were determined to be 11.4 mg/g (pH = 2.0–8.0) and 13.4 mg/g (pH = 2.0–6.5), respectively. Kinetic analysis revealed that the BPA adsorption followed a pseudo-second-order kinetic process, while isotherm analysis suggested that the BPA adsorption was better described by the Freundlich model (R² = 0.993–0.998). The surfactant-modified kaolin demonstrated a retention of over 70% of its initial adsorption capacity after five cycles of desorption and regeneration, further confirming its potential for recycling. Additionally, these modified adsorbents exhibited excellent compatibility in removing bisphenol analogs. These findings provide valuable insights into the practical application of surfactant-modified clay minerals for the elimination of hydrophobic organic pollutants from water.