Environmentally-friendly activated carbon for the removal of antibiotic-resistant bacteria removal from hospital wastewater

Abstract

The rise of antibiotic-resistant bacteria has driven research into natural antimicrobial alternatives. Allicin, a compound formed in freshly crushed garlic cloves, exhibits antibacterial properties but suffers from poor stability in aqueous environments. That is why this study aimed to explore the synthesis and characterization of allicin-modified activated carbon (AMAC) and evaluate its potential application removing Escherichia coli from synthetic hospital wastewater (HWW). Sugarcane bagasse (SB) provided by a local Brazilian alcohol mill was transformed into activated carbon (SBAC) through a hydrothermal process (heating at 200 °C for 24 h followed by activation at 450 °C for 10 min). Allicin extract was obtained from fresh garlic and impregnated onto the SBAC surface, resulting in AMAC with 105 µm mean diameter. The materials were characterized (FT-IR, Raman and N₂-physisorption), revealing significant structural and surface modifications. The antibacterial activity of allicin against E. coli was assessed through minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) trials and disk diffusion, demonstrating effective bacterial growth inhibition, as expected. Adsorption assays showed that AMAC enhanced E. coli removal efficiency in synthetic HWW by 3 %, compared to the AMAC in deionized and sterile water. This improvement was attributed to the positive interactions and synergistic effects between AMAC and the wastewater constituents. In other words, it means that AMAC can be used in the E. coli removal even in presence of organic and inorganic molecules without any loss of efficiency. The study also highlights the environmentally friendly synthesis process of AMAC and its potential as a sustainable solution for treating HWWs without the use of antibiotics, thus avoiding the potential release of pharmaceutical compounds into the environment. The results suggest that AMAC could be a viable alternative for enhancing the removal of antibiotic-resistant bacteria from contaminated water sources, contributing to public health and environmental protection.