Abstract
Emerging contaminants are chemical compounds present in the environment, particularly in aquatic systems, which are currently not subjected to regulatory measures. This problem occurs when pollutants are introduced into aquatic systems through multiple sources, including wastewater discharge, agricultural runoff, and atmospheric deposition. Products that contain emerging contaminants are classified into 3 categories: pharmaceuticals, personal care products, and endocrine-disrupting chemicals. Several organisms are affected by the accumulation of the chemicals in water bodies. These emerging contaminants have been found to alter the behaviour and development of fish and organisms that form the base of the aquatic food chain. Additionally, they interfere with the ability of organisms to reproduce and grow appropriately. In the present study, a series of experiments were performed using Stigeoclonium nanum microalgal biomass to determine the removal efficiency of one of these contaminants, that is, caffeine. Experiments were performed in duplicate using 20 mL tubes. A 500 mg L-1 caffeine solution was prepared and applied at different doses at the same time as a known amount of dry biomass. The tubes were maintained at a constant temperature of 24 ± 2 °C with a stirring speed of 400 rpm. Optical absorbance readings were recorded, and calculations were performed to determine the removal percentage for each caffeine dose. At concentrations of 50, 100, and 125 mg L-1, 100% removal was reached, while at 250 and 500 mg L-1, removal was reduced to 79.76 % and 49.66%, respectively. These data indicated a continual decrease in caffeine up to 125 mg L-1, suggesting a possible saturation point for the dry biomass used over this concentration range. Furthermore, these results emphasise the necessity of conducting adsorption isotherms to understand the relationship between caffeine concentration and its removal efficiency using microalgal biomass. This could lead to the optimisation of contaminant removal, especially at higher concentrations. Although the microalgal biomass of S. nanum appears to be effective in removing caffeine at moderate concentrations, more comprehensive experiments surrounding adsorption isotherms are required to enhance efficiency at higher concentrations.
