Evaluation of the efficiency of three different mineral adsorbents in the removal of pollutants in samples from a tropical spring in Northeastern Brazil.

Abstract

Human water sources are increasingly threatened around the world due to various sources of pollution such as agriculture and industry. The objective of this study was to evaluate three new adsorbents as pollutant remedies for subsequent application in the Joanes River located in the State of Bahia in Brazil. The specific pollutants were nitrogen, phosphorus (P), aluminum (Al), iron (Fe), cyanobacteria, and saxitoxins. Initially, studies (pH 7 and 22°C) were performed with samples contaminated in the laboratory with phosphorus (P), nitrate ( ), and ammonia (NH3 ), to select the most efficient adsorbent and to determine the equilibrium time. Pumice bituminous coal was found to have the best efficiencies (≥70%) at 360min (equilibration time). The experimental data did not fit the Langmuir and Freundlich model. The bituminous coal with pumice stone was then applied to water samples from a designated capture point of the Joanes springs, a river system that is responsible for supplying the city of Salvador and the metropolitan region, located on the northern coast of Bahia. The removal efficiency analyses were performed on a DR6000 UV/VIS SPECTROPHOTOMETER, using the methodology defined in the Standard Methods 2017, after which this adsorbent was subjected to scanning electron microscopy. As a result, removal efficiencies (≥98%) were obtained for all contaminants (nitrogen, phosphorus (P), aluminum (Al), iron (Fe), cyanobacteria, and saxitoxins) as well as a highly heterogeneous layer pointed by SEM images, further demonstrating the adsorbent potential as a efficient alternative in environmental control after additional studies. PRACTITIONER POINTS: Pumice bituminous coal has proven to be an excellent adsorbent for a wide range of pollutants such as phosphorus, nitrogen, ammonia, toxins, cyanobacteria, and metals. The adsorbent promoted a high reduction in phosphorus concentrations (3.40mg/L to 0.01mg/L), about 98% and 81% for cyanobacteria (12,850Cel/ml to 2,560Cel/ml). The adsorbent promoted a high reduction in concentrations of 98% saxitoxins (4.32µg/L to 0.2µg/L).