Synergistic functions of copper-based nanomaterials modified granular activated carbon: antibacterial activity, antibiotics adsorption, and impact of preceding chlorination on antibiotic resistance genes removal in tertiary treated hospital effluents

The synergistic efficacy and mechanisms of antibacterial activity and adsorption of antibiotics/intermediates using copper-based nanomaterials modified granular activated carbon (GAC) were evaluated, including the impact of preceding chlorination on the reduction of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in effluents treated by fixed-bed column. Copper-based MOFs coated on GACs (GAC-CuBDC and GAC-CuNH₂BDC) exhibited higher antibacterial efficacy than the functionalized GACs (–COOH and –NH₂) and copper oxide (CuO and Cu₂O)–coated GACs, which 100% eliminated both Gram-negative E. coli and Gram-positive S. aureus bacteria (5.5 and 5.1 log reduction, respectively). Notably, GAC-CuBDC can inhibit the growth of total bacteria and presumptive Pseudomonas sp. in the matrix of hospital effluents to non-detectable levels; however, interference from dissolved organic matter in the effluents can reduce antibacterial efficacy, requiring an increased solid-to-liquid ratio from 4 to 8 g/L to achieve 100% inhibition. Hydrophilic GAC-CuBDC exhibited high performance in adsorbing intermediates derived from penicillin G, ampicillin, ceftazidime, and ciprofloxacin. The intermediates found in chlorinated effluent could be more easily eliminated by functionalized GACs than those in non-chlorinated effluent. The adsorption capacities of penicillin G, ceftazidime, and ciprofloxacin onto GAC-CuBDC were comparable to those of pristine GAC, whereas ampicillin showed a two-fold higher adsorption on GAC-CuBDC than on pristine GAC. Adsorption mechanisms of antibiotics onto GAC-CuBDC may include hydrogen bonding and π-π interactions (involving -NH and nitroaromatic ring of the antibiotic) with the acidic functional groups of GAC, combined with hydrogen bonding at the terminal -OH groups of the CuBDC copper nodes. Passage through the fixed-bed column of GAC-CuBDC could reduce the intracellular ARGs and ARB from hospital effluents. However, the coexistence of chlorination may promote the growth of P. aeruginosa and interfere with the reduction of some ARGs and ARB after tertiary treatment by the GAC-CuBDC column.

Graphical abstract