Modular Chitosan-Based Adsorbents for Tunable Uptake of Sulfate from Water.

Bernd G K Steiger,Lee D Wilson

doi:10.3390/ijms21197130

Bernd G K Steiger, Lee D Wilson

Open Access

https://doi.org/10.3390/ijms21197130

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Abstract

The context of this study responds to the need for sorbent technology development to address the controlled removal of inorganic sulfate (SO42−) from saline water and the promising potential of chitosan as a carrier system for organosulfates in pharmaceutical and nutraceutical applications. This study aims to address the controlled removal of sulfate using chitosan as a sustainable biopolymer platform, where a modular synthetic approach was used for chitosan bead preparation that displays tunable sulfate uptake. The beads were prepared via phase-inversion synthesis, followed by cross-linking with glutaraldehyde, and impregnation of Ca2+ ions. The sulfate adsorption properties of the beads were studied at pH 5 and variable sulfate levels (50–1000 ppm), where beads with low cross-linking showed moderate sulfate uptake (35 mg/g), while cross-linked beads imbibed with Ca2+ had greater sulfate adsorption (140 mg/g). Bead stability, adsorption properties, and the point-of-zero charge (PZC) from 6.5 to 6.8 were found to depend on the cross-linking ratio and the presence of Ca2+. The beads were regenerated over multiple adsorption-desorption cycles to demonstrate the favorable uptake properties and bead stability. This study contributes to the development of chitosan-based adsorbent technology via a modular materials design strategy for the controlled removal of sulfate. The results of this study are relevant to diverse pharmaceutical and nutraceutical applications that range from the controlled removal of dextran sulfate from water to the controlled release of chondroitin sulfate.

Highlights

Saline ground and surface water deposits pose a significant concern to global water and food security, especially in developing countries
Sulfate from geochemical sources have been related to elevated sulfate levels that can range from 6500 mg/L to 20,000 mg/L in dug-outs of Saskatchewan, Canada’s agricultural bread basket [7,8]
Figure 1) that involves phase-inversion synthesis along with glutaraldehyde cross-linking at variable levels with sequential surface modification via bead doping with Ca2+ in aqueous calcium chloride

Summary

Introduction

Saline ground and surface water deposits pose a significant concern to global water and food security, especially in developing countries. Climate change and increased irrigation for food production may exacerbate the detrimental effects of water salinity [4,5], where projections forecast negative impacts on global water security [6]. In countries such as the USA and Canada, sulfate contamination is attributed to the erosion of naturally abundant magnesium sulfate and gypsum deposits. Sulfate from geochemical sources have been related to elevated sulfate levels that can range from 6500 mg/L to 20,000 mg/L in dug-outs of Saskatchewan, Canada’s agricultural bread basket [7,8]

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