Adsorption of nitrogen heterocyclic compounds (NHC) on soil minerals: Quinoline as an example

Understanding the adsorption behavior of nitrogen heterocyclic compounds (NHCs) on soil minerals underlies more effective design wastewater treatment and soil/groundwater remediation. We investigated quinoline, a representative NHC, quartz sand (using Berea sandstone as model), at 3 < pH 9, in low (0.05 M) high (0.7 ionic strength solutions where NaCl was background electrolyte. Minor clay (kaolinite) contributed significantly to quinoline uptake. Adsorption peaked pH∼6. It decreased from 2 equivalent monolayers monolayer activity approaching that seawater. A triple layer surface complexation model fits data well, kaolinite sites for three types (Q) complexes: 1) innersphere ≡SiOHQ; 2) outersphere ≡SiO-QH+ 3) ≡AlOHQ2. Aluminol promote multilayer adsorption, whereas only form silanol sites. Site density calculations molecular dynamics (MD) confirmed adsorbs upright, edge, follows formation initial monolayer. Our results confirm effectiveness sand(stones) clays removing NHCs waste groundwaters.