Activated carbon from termite feces impregnated with silver: Preparation and evaluation of antimicrobial activity and ecotoxicity

Silver has a potent antimicrobial action, but its use is still restricted due to toxicity and aggregation problems. Impregnation with active carbon (AC) has been suggested as an alternative to solve this problem. In this study, termite feces were used to prepare composites containing silver nanoparticles and AC. Reducing agents and different amounts of H2 SO4 and silver were used. Antimicrobial activity was assessed using the minimum inhibitory concentration (MIC) and the kinetics of microbial growth of S. aureus, E. coli and C. albicans. Phytotoxicity and acute toxicity were assessed for Cucumis sativus and Artemia salina. The composites that presented MIC 500 μg/mL for S. aureus and E. coli were AC25Ag (6 μg/mL Ag) and AC25AgB (78 μg/mL Ag), respectively. AC6AgS showed antimicrobial activity in C. albicans with MIC of 500 μg/mL (23 μg/mL Ag). AC25AgB inhibited the growth of S. aureus and E. coli for 48 and 32 h, respectively. At a concentration of 10 g/L, the compounds showed deleterious effects on seedling germination and elongation and on the chlorophyll synthesis of C. sativus. The composites showed no toxicity to A. salina. Based on these results, AC25AgB has the potential to be used in water disinfection.