Synthesis and application of cationised cellulose for removal of Cr(VI) from acid mine-drainage contaminated water

Anita Etale; Dineo S Nhlane; Alseno K Mosai; Jessica Mhlongo; Aaliyah Khan; Karl Rumbold; Yannick B Nuapia

doi:10.12688/aasopenres.13182.1

Synthesis and application of cationised cellulose for removal of Cr(VI) from acid mine-drainage contaminated water

AAS Open Res. 2021 Jan 21:4:4. doi: 10.12688/aasopenres.13182.1. eCollection 2021.

Authors

Anita Etale^{1

2}, Dineo S Nhlane², Alseno K Mosai², Jessica Mhlongo², Aaliyah Khan³, Karl Rumbold³, Yannick B Nuapia²

Affiliations

¹ Global Change Institute, University of the Witwatersrand, Johannesburg 2000, South Africa, Johannesburg, Gauteng, 2000, South Africa.
² Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2000, South Africa, Johannesburg, Gauteng, 2000, South Africa.
³ School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2000, South Africa, Johannesburg, Gauteng, 2000, South Africa.

Abstract

Background: Acid mine drainage (AMD) leads to contamination of surface and ground water by high levels of toxic metals including chromium. In many cases, these waters are sources of drinking water for communities, and treatment is therefore required before consumption to prevent negative health effects. Methods: Cationised hemp cellulose was prepared by etherification with two quaternary ammonium salts: 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) and glycidyltrimethylammonium chloride (GTMAC) and examined for (i) the efficiency of Cr(VI) removal under acid mine-drainage (AMD) conditions, and (ii) antibacterial activity. Adsorbents were characterised by electron microscopy, Fourier transform infrared (FTIR), CP-MAS ¹³C nuclear magnetic resonance (NMR) spectroscopy, elemental composition and surface charge. Results: FTIR and solid state ¹³C NMR confirmed the introduction of quaternary ammonium moieties on cellulose. ¹³C NMR also showed that cationisation decreased the degree of crystallisation and lateral dimensions of cellulose fibrils. Nevertheless, 47 % - 72 % of Cr(VI) ions were removed from solutions at pH 4, by 0.1 g of CHPTAC and GTMAC-cationised cellulose, respectively. Adsorption kinetics followed the pseudo-second order model and isotherms were best described by the Freundlich and Dubinin-Radushkevich models. When GTMAC-modified cellulose was applied to AMD contaminated water (pH 2.7); however, Cr(VI) removal decreased to 22% likely due to competition from Al and Fe ions. Cationised materials displayed considerable antibacterial effects, reducing the viability of Escherichia coli by up to 45 % after just 3 hours of exposure. Conclusions: Together, these results suggest that cationised cellulose can be applied in the treatment of Cr(VI)-contaminated mine water particularly if pre-treatments to reduce Fe and Al concentrations are applied.

Keywords: 3-chloro-2-hydroxypropyl trimethyl ammonium chloride; Cellulose cationisation; Chromium(VI); acid mine drainage; glycidyltrimethylammonium chloride; hemp cellulose; quaternary ammonium salts.

Associated data

figshare/10.6084/m9.figshare.13299128.v2

Grants and funding

This work was supported by the African Academy of Sciences (AAS) through a Future Leaders - African Independent Research (FLAIR) Fellowship to AE and JM (LR\R1\190087). The FLAIR Fellowship programme is a joint initiative between AAS and the Royal Society (UK), with support from the Global Challenges Research Fund (GCRF).