Effect of Chitosan's Degree of Deacetylation on the Performance of PES Membrane Infused with Chitosan during AMD Treatment

Machodi Mathaba; Michael Olawale Daramola

doi:10.3390/membranes10030052

Effect of Chitosan's Degree of Deacetylation on the Performance of PES Membrane Infused with Chitosan during AMD Treatment

Membranes (Basel). 2020 Mar 24;10(3):52. doi: 10.3390/membranes10030052.

Authors

Machodi Mathaba¹, Michael Olawale Daramola²

Affiliations

¹ School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Private Bag X3, Wits 2050, Johannesburg, South Africa.
² Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Private bag X20 Hatfield, Pretoria 0028, South Africa.

Abstract

Acid mine drainage is an environmental problem associated with mining operations and activities. Its treatment is essential to achieving environmental sustainability. In this study, a polyethersulphone (PES) membrane infused with chitosan is proposed as a point-of-use material for treating acid mine drainage (AMD). The composite material explored the synergetic effect between chitosan and polymer, particularly considering the effect of the degree of deacetylation (DD) of chitosan on the performance of membrane. Chitosan was produced from chitin under various synthesis process conditions and infused within polyethersulphone membrane. The results obtained show that chitosan with the highest degree of deacetylation was achieved with a temperature of 100 °C and NaOH concentration of 40 wt%. Increasing the temperature above 100 °C started degrading already formed or exposed amine groups, thus, reducing the DD of the chitosan sample. The contact angle and porosity analysis indicated that the hydrophilic nature of the membrane was enhanced with increasing DD of the chitosan. The performance of the membranes was conducted on a Dead-end filtration cell using synthetic acid mine drainage. The results showed that the flux and rejection of the membrane was enhanced with increasing degree of deacetylation. PES 5 and PES 1 were blended with chitosan having the highest (95.97%) and lowest (33.93%) degree of deacetylation, respectively. PES 5 reported pure water flux of 123 L/m²·h and PES 1 was recorded as 104 L/m²·h. Similarly, the rejection of the membrane was improved with increasing chitosan's degree of deacetylation. PES 5 had higher rejection and PES 1 had the least rejection. Maximum rejection for the contaminants was determined as 98.05, 97.39, 96.25, 95.24 and 80.34% for Mn²⁺, Fe²⁺, Mg²⁺ and Ca²⁺ and SO₄^2-, respectively. The results obtained show that chitosan's degree of deacetylation has a positive effect on the performance of polyethersulphone membrane during the treatment of acid mine drainage.

Keywords: acid mine drainage; chitosan; degree of deacetylation; hydrophilicity; polyethersulphone membrane.

Grants and funding

126578/National Research Foundation (NRF) South Africa