Adsorption of the emerging pollutants on Buena Vista landfill cover material and implications on regional aquatic pollution

Abstract

The occurrence of emerging pollutants in water represents a health risk for humans and the ecosystem. It has been shown that pollutant–soil interactions are determinants in preventing contamination of water sources by leachates from landfills. In this work, batch experiments were conducted to study the soil sorption process of amoxicillin (AMX), acetaminophen (ACP), levonorgestrel (LNG), and chlorothalonil (CTL) in four different soil layers used as cover material in Buena Vista landfill located in the municipality of La Union (Antioquia, Colombia). All soil layers were characterized using FT-IR, XRF and BET experimental techniques. In addition, pH and ionic strength effects on the adsorption process were also evaluated. The % of removal follows the order CTL > LNG > AMX > ACP in all soil layers. ACP y AMX adsorption was best described by pseudo-second-order kinetics, while LNG and CTL adsorption was best fitted by the pseudo-first-order kinetic model. Pollutant adsorptions were found to be favored at pH 6.3. Increasing the solution ionic strength decreases the adsorption of pollutants in all evaluated soil layers. The adsorption process was governed by hydrophilic and hydrophobic interactions. Polar molecules such as AMX and ACP remain in the aqueous phase while nonpolar LNG and CTL interact with clay minerals in the soil surface, presumably through van der Waals forces. Based on our findings, a cover material with both hydrophilic and lipophilic characteristics operating close to neutral, and with low ionic content, is advised for the Buena Vista landfill to improve its role as a barrier in decreasing potential pollutants contaminating groundwater sources.