# Tunable Fly Ash-Based Geopolymer Fibers for Multivariate Heavy-Metal Adsorption: Optimization and Mechanistic Insights

## TL;DR

Researchers developed geopolymer fibers that efficiently remove heavy metals from water, offering a sustainable and scalable solution for wastewater treatment.

## Contribution

The study introduces tunable fly ash-based geopolymer composite fibers with optimized performance for multivariate heavy-metal adsorption.

## Key findings

- Fibers with 60 wt% FAGP showed the highest adsorption efficiency, especially for Pb2+.
- Adsorption mechanisms involved both chemisorption and physisorption, depending on the metal ion.
- The composite fibers outperformed conventional adsorbents in capacity and scalability.

## Abstract

This study presents the fabrication and performance optimization of porous fly ash-based geopolymer (FAGP)–polyethersulfone (PES) composite fibers with tunable FAGP loading for the multivariate adsorption of heavy-metal ions from aqueous solutions. Fibers containing 20 wt%, 40 wt%, and 60 wt% FAGP were prepared using phase inversion method and were characterized using X-ray computed tomography and mechanical testing. Adsorption experiments were conducted to assess the removal efficiencies of Pb2+, Cd2+, Cu2+, and Ni2+ at different pH values, temperatures, contact times, adsorbent dosage and initial metal-ion concentrations. The composite containing 60 wt% FAGP exhibited the high performance for all ions, and its performance was especially high for Pb2+. The isotherm and kinetic modeling revealed that the adsorption process followed Freundlich and Redlich–Peterson models, with mixed chemisorption–physisorption mechanisms depending on the metal-ion type. Compared with conventional adsorbents, the optimized composite fibers exhibited high adsorption capacity, enhanced handling suitability, and scalability in addition to their sustainability owing to the use of industrial by-products as precursors. These findings provide new insights into the structure–function relationships of FAGP composite fiber adsorbents and their potential for wastewater treatment applications.