Bio-Based Ion Exchange Resin from Water Hyacinth for Efficient Groundwater Hardness Treatment

Abstract

This study aims to prepare cation exchange resin from the stems and leaves of water hyacinth via the sulfonation process and to evaluate their efficiency and capacity for water softening. The water hyacinth was separated into stems and leaves and was then ground to powder. The powders were subjected to sulfuric acid treatment (sulfonation) to introduce active sulfonic acid (-SO₃H) groups. Treated materials were classified as stem- and leaf-derived water hyacinth resin. The results revealed that sulfuric acid-treated water hyacinth enhanced the porosity of resin due to the incorporation of sulfonic acid groups. This improvement provided a larger surface area and more active sites for cation exchange compared to untreated samples. Sulfuric acid-treated water hyacinth leaves demonstrated greater hardness removal efficiency compared to stems, attributed to the higher cellulose content in the leaves. The optimal dosage of leaf-derived resin for complete hardness removal (414 mg·L^-1 as CaCO₃) was determined to be 22.5 g·L^-1, equivalent to an ion exchange capacity of 0.810 meq·g^-1. The resin exhibited selective affinity for ions in the order of Mg²⁺ > Ca²⁺ >> Na⁺. Additionally, the resin retained its efficiency after the first and second regeneration cycles using 0.01 M hydrochloric acid, maintaining 100% hardness removal, comparable to the performance of the new resin. These results highlight the potential of bio-based resins derived from water hyacinth leaves as a sustainable, cost-effective solution for water softening. Bio-based resins contribute to environmental conservation, promote eco-friendly materials, and support the circular economy and sustainable resource management principles.