In-vitro Antimicrobial Activity and Adsorption Adequacy of Natural Clay against Some Air and Water Pollutants

Clay is a natural outcome product of many environmental processes and has a wide diversity in its origins and end-uses in industrial and medical fields. The in-vitro antimicrobial activity of clay against E. coli O157: H7 and Salmonella typhimurium, as well as the adsorption capacity against air gaseous impurities like ammonia and water impurities including heavy metal, hardness, and organic matter salts were investigated. Three weights of clay (0.5, 1.0, and 2.0 g) were evaluated inside the laboratory against E. coli O157: H7 (1.5 x 108 CFU/ml), Salmonella typhimurium (3.5 × 105 CFU/ml), ammonia (80 ppm), lead nitrate (3.5 mg/L), magnesium sulfate (2160 mg/L CaCO3 ), and ammonium chloride (31.5 mg/L) using minimal inhibitory concentration (MIC) test at specified exposure intervals (5, 10, 20, 30, and 60 minutes). A total of 270 pollutant/contaminant-clay-air/water samples were collected (45 samples for each pollutant, 3 replicate × 3 clay weights × 5 interval times) and examined. The results revealed highly significant antimicrobial activities (P < 0.01) against E. coli O157: H7 and Salmonella typhimurium with reductions of the counts up to 84.7% and 47.6%, respectively when exposed to 0.5 g of clay for 60 minutes. Highly significant reductions (P < 0.01) were recorded in aerial ammonia concentrations, as well as, lead, hardness, and total organic matter water concentrations after exposure to 0.5, 2.0, 2.0, and 0.5 g of natural clay for 60 minutes with reduction percentages up to 4.5%, 41.7%, 41.6%, and 21.8%, respectively. The study concluded the highly efficient antimicrobial activities and adsorptive actions of natural clay concerning 0.5 and 2.0 g after an exposure time of 60 minutes.