title: Mechanisms of removal of three widespread pharmaceuticals by two clay materials.
abstract: Pharmaceutical residues presence in the environment is among nowadays top emergent environmental issues. For removal of such pollutants, adsorption is a generally efficient process that can be complementary to conventional treatment. Research of cheap, widely available adsorbents may make this process economically attractive. The aim of the present work was to evaluate the capacity of two clay materials (exfoliated vermiculite, LECA) to adsorb gemfibrozil, mefenamic acid and naproxen in lab-scale batch assays. Results show that both adsorbents are able to remove the pharmaceuticals from aqueous medium. Although vermiculite exhibited higher adsorption capacities per unit mass of adsorbent, LECA yielded higher absolute removals of the pharmaceuticals due to the larger mass of adsorbent. Quantum chemistry calculations predicted that the forms of binding of the three molecules to the vermiculite surface are essentially identical, but the adsorption isotherm of naproxen differs substantially from the other two's. The linear forms of the latter impose limits at lower concentrations to the removal efficiencies of these pharmaceuticals by vermiculite, thereby electing LECA as more efficient. Notwithstanding, vermiculite's high specific adsorption capacity and also its much faster adsorption kinetics suggest that there may be some benefits in combining both materials as a composite adsorbent solution.
authors.affiliation: Chemistry Department, Sciences and Technology School, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal; MARE-Marine and Environmental Sciences Centre, Institute for Advanced Studies and Research, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal. Electronic address: avbd@uevora.pt.
authors.forename: A V
authors.initials: AV
authors.lastname: Dordio
authors.affiliation: Chemistry Department, Sciences and Technology School, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal.
authors.forename: S
authors.initials: S
authors.lastname: Miranda
authors.affiliation: Chemistry Department, Sciences and Technology School, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal; CQE-Évora Chemistry Centre, Institute for Advanced Studies and Research, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal; Hercules Centre, Institute for Advanced Studies and Research, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal.
authors.forename: J P
authors.initials: JP
authors.lastname: Prates Ramalho
authors.affiliation: Chemistry Department, Sciences and Technology School, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal; CQE-Évora Chemistry Centre, Institute for Advanced Studies and Research, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal; Hercules Centre, Institute for Advanced Studies and Research, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal.
authors.forename: A J Palace
authors.initials: AJP
authors.lastname: Carvalho
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D003198:Computer Simulation; D004350:Drug Residues / Q000302:isolation & purification; D015248:Gemfibrozil / Q000737:chemistry / Q000302:isolation & purification; D007700:Kinetics; D008528:Mefenamic Acid / Q000737:chemistry / Q000302:isolation & purification; D008958:Models, Molecular; D009288:Naproxen / Q000737:chemistry / Q000302:isolation & purification; D010316:Particle Size; D004364:Pharmaceutical Preparations / Q000302:isolation & purification*; D013816:Thermodynamics; D014865:Waste Disposal, Fluid
chemical_list: D000538:Aluminum Silicates; D004364:Pharmaceutical Preparations; C003760:vermiculite; D008528:Mefenamic Acid; D009288:Naproxen; D015248:Gemfibrozil; D000077215:Clay
keywords: Adsorption; Clay materials; Exfoliated vermiculite; LECA; Periodic DFT; Pharmaceuticals