Scalable synthesis of polyhydroxy iron-modified kaolin via low-temperature hydrolysis-polymerization for efficient adsorption of direct black 38

Abstract

Kaolin (KC) has highly promising prospects in the purification of the water environment and treatment of organic pollutants. However, its low adsorption capacity, poor selectivity and low reusability significantly constrain its further application as an agent for treating water pollution. Herein, a novel kaolin adsorbent, namely polyhydroxy iron-modified kaolin (PIK), has been devised through low-temperature liquid-phase synthesis and impregnation approaches, surmounting the limitations of non-selectivity and low adsorption capacity. The adsorbent accomplished selective adsorption of Direct Black 38 (DB38) with an adsorption capacity of 76.1 mg g⁻¹ and could maintain an adsorption efficiency of 82.0% even after being reused three times. This work demonstrates the remarkable adsorption performance of PIK and provides a promising strategy for the large-scale preparation and practical application of high-capacity kaolin adsorbents at low temperatures.