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

## TL;DR

A new kaolin-based adsorbent is developed to efficiently and selectively remove dyes from water.

## Contribution

A novel low-temperature synthesis method for polyhydroxy iron-modified kaolin with high adsorption capacity and reusability.

## Key findings

- PIK achieved a DB38 adsorption capacity of 76.1 mg g−1.
- PIK retained 82.0% adsorption efficiency after three reuse cycles.
- PIK outperformed traditional kaolin in adsorption selectivity and capacity.

## 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.

The adsorption mechanism of PIK for DB38 dyes (a), zeta potential (b), distribution of iron ion forms (c) and comparison of DB38 adsorption effects between KC and PIK (d).