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 SO42−, 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.
Highlights
Membrane technology has gained significant attention for application in wastewater treatment due to high quality water requirements and environmental concerns
Chitosan used in this study was synthesized from chitin which was obtained by processing seashells collected from Durban South Beach, Rutherford in KwaZulu Natal, South Africa
The FTIR spectra of the chitosan samples exhibited characteristic amino peaks at around 3300 to 3500 cm−1 overlapping with the N–H stretching with a minimum intensity of the amine functional group
Summary
Membrane technology has gained significant attention for application in wastewater treatment due to high quality water requirements and environmental concerns. Hydrophilic modification of membranes during wastewater treatment is essential in membrane science and technology [4]. The main disadvantage characterizing PES and PES based membranes is related to its hydrophobic character generated by the sulfonyl group linking the two phenylene rings [7]. Several alterations such as chemical, physical and surface modification and blending have been research to improve the hydrophilic property of PES membranes [8]. The ultimate aim of membrane modification with hydrophilic agents is to localize the hydrophilic material on the membrane surface and within the pores to positively influence membrane permselectivity and reduce fouling [4]
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