Comparison of Activated Carbons Norit-RB4W and Filtrasorb 500 for the Removal of Vancomycin in Water

1. Introduction – The consumption of antibiotics for human use has increased drastically in recent years, causing antimicrobial resistance to be recognised as “one of the worst global health issues” [1,2]. The release of antibiotics into the environment from household, hospital and industrial wastewaters leads to serious effects on human and animal health [3]. Misuse of antibiotics and their presence in wastewater has led to the emergence of antibiotic-resistant bacteria (ARB). Vancomycin residues in wastewater from hospital use is linked with the appearance of vancomycin-resistant bacteria [4]. Adsorbent materials such as activated carbon (AC), have proven to be effective at removing antibiotics from water [5]. The aim of this study was to investigate two ACs for the removal of vancomycin from water.
2. Experimental - The physicochemical properties of two ACs were compared and linked to their vancomycin adsorptive performance. The characterization of the AC Norit-RB4W and Filtrasorb 400 comprised of measuring their zeta-potential using a Malvern Zetasizer, particle size with a Retch AS200 sieve shaker, and point of zero charge pH with a JENWAY 3510 pH Meter. Vancomycin solution samples of 50μg/ml with the two ACs were prepared, shaken in an orbital shaker under various conditions and analysed with a Varian Cary Bio UV/Visible Spectrophotometer. The influence of contact time (0-168 hours), pH (3-11), adsorbent dosage (100-1000mg), temperature (15-45°C), and initial vancomycin concentration in solution (5-100 μg/ml) were investigated for 4 and 24 hours of contact time.
3. Results and Discussion - The equilibrium of vancomycin adsorption was reached at 120 hours of contact time for both Filtrasorb 400 and Norit-RB4W. The sorbents exhibited peak performance at a solution pH of 5. The highest vancomycin removal efficiency was attained with 0.6g of Filtrasorb 400 at 24 hours, which achieved an almost complete removal of vancomycin from solution. With 1.0g of Norit-RB4W, vancomycin concentrations were reduced from 48.9 to 25.6μg/ml. Temperature modification showed no statistically significant effect on vancomycin concentration of Norit-RB4W and control samples after 24 hours. However, Filtrasorb 400 showed a notable increase in removal efficiency with increasing temperature. Removal efficiency was found to be inversely proportional and uptake directly proportional to initial vancomycin concentration. Filtrasorb 400 demonstrated superior performance in removing vancomycin from water. This was attributed to its particles consisting of more mesopores and macropores and it’s larger BET surface area.

Table I. Specific surface area and pore characteristics of the studied GACs
Characteristics Granular activated carbon
Filtrasorb-400 Norit-RB4W
BET surface area, m2/g 1105 930.0
Total pore volume, cm3/g 0.489 0.395
Mean Mesopore width, nm 4.144 3.650

4. Conclusions – Norit-RB4W and Filtrasorb 400 are both effective for the removal of vancomycin in water. Filtrasorb 400 had a much higher removal efficiency than Norit-RB4W which was attributed to it’s higher surface area and increased number of mesopores and macropores within its structure.
5. References
[1] World Health Organisation (2014). Antimicrobial Resistance, Global Report on Surveillance.
[2] Berendonk TU et al., (2015) Nature Rev. Microbiol. 13, 310–317.
[3] Bush, K. et al. (2011) Tackling antibiotic resistance. Nature Rev. Microbiol. 9, 894–896.
[4] Shengcen Z. et al. (2020) Hospital Wastewater as a Reservoir for Antibiotic Resistance Genes, Frontiers, 8, p.1-2.
[5] Rasouli Sadabad, H. et al. (2023) Effect of activated carbon characteristics on its ability to remove vancomycin and rifampicin from water. N. I. Bioeng. Conf., Queen’s University Belfast.