Competitive Association of Antibiotics with a Clay Mineral and Organoclay Derivatives as a Control of Their Lifetimes in the Environment

Abstract

A Na-smectite clay mineral (Na-Mt) was exchanged with two concentrations of benzyldimethyltetradecyl ammonium chloride cationic surfactant up to one time the cation exchange capacity. Nonionic organoclay was prepared with polyoxyethylene (20) oleyl ether (Brij-O20) nonionic surfactant at one concentration. The resulting organoclays displayed lateral layer organization of the surfactants within their interlayer space.. The adsorption properties of these organoclays and the starting raw clay mineral were evaluated for three extensively used antibiotic pharmaceutical products: the amoxicillin (AMX), the sulfamethoxazole (SMX), and the trimethoprim (TRI), recognized as recalcitrant compounds to conventional water treatments and to display a complex behavior for different pH and temperature experimental conditions. Besides showing short half-life time with possible degradation by UV radiation, these antibiotics associated with mineral phases cause serious environmental issues of which the toxic effect can be exacerbated in the presence of other chemical compounds. From the set of data obtained by complementary techniques: UV and Fourier transform infrared spectroscopy, high-performance liquid chromatography coupled with mass spectrometry, and X-ray diffraction, it appears that the nonionic organoclay shows its versatility for the adsorption of individual molecules as well as a pool of antibiotics. The mixing of the three antibiotics showing different electric charged species (cations, anions, and zwitterions) mimics the natural context drives to a deep modification of the adsorption behavior onto the different materials that can act as possible carrier mineral phases in aquatic environment. These competition effects can be measured through the significant decrease of the KF Freundlich constants for AMX in the presence of other molecules (or electrolytes), whereas TRI and SMX, by their possible association, create a synergistic effect that favors their adsorption on the whole layered materials.

Tuning down the environmental interests of organoclays for emerging pollutants: Pharmaceuticals in presence of electrolytes

“…These isotherms represent the adsorbed amounts of the pharmaceuticals onto the layered materials after being in contact for 24 hours under stirring (batch experiments), as a function of the equilibrium concentration of pharmaceuticals. As expected for cationic compounds that can be ion-exchanged with the inorganic cations located within the interlayer space of untreated or raw swelling clay minerals, the adsorption isotherms onto Na-Mt reveal a Langmuir or L-type line shape, which is well known for adsorption cases ( Figure 2) (Bekçi et al 2006, Thiebault et al 2015, De Oliveira et al 2018. Interestingly similar behavior can be observed onto both nonionic and cationic organoclays, which thus confirms the proper adsorption of the two cationic pharmaceuticals (metoprolol and trimethoprim) on the three adsorbents.…”

“…Interestingly similar behavior can be observed onto both nonionic and cationic organoclays, which thus confirms the proper adsorption of the two cationic pharmaceuticals (metoprolol and trimethoprim) on the three adsorbents. Interestingly, with a similar water solubility value as TRI, the adsorption of metoprolol (MTP) displays a different behavior without any notable saturation for both Na-Mt and Brij 0.4 -Mt, whereas it appears rather limited onto BDTA-Mt as it could be expected for cationic species (Guégan et al 2015, De Oliveira et al 2018. In the latter case, the adsorbed amount reaches a maximum value of about 1.26 x 10 -4 mol g -1 , in contrast to those of 5.08 x 10 -4 and 5.62 x 10 -4 mol g -1 for Brij 0.4 -Mt rand Na-Mt respectively.…”

“…As expected, the proper intercalation of the surfactants within the interlayer space of the starting Na Since the adsorption properties of the organoclays mainly depend on the kind of surfactants used, two different surfactants of different nature (nonionic and cationic) and saturated and unsaturated were used. Thus, the prepared materials display complementary properties: from cation exchange capacity, and hydrophilicity for untreated Na-Mt, dual hydrophilicity/phobicity for Brij 0.4 -Mt; to hydrophobicity or organophilicity and even possible anion adsorption ability for BDTA-Mt (Guégan et al 2015, De Oliveira and Guégan 2016, De Oliveira et al 2017, De Oliveira et al 2018. In addition, the difference…”

“…The chemical modification of swelling-type clay minerals, by using surfactants of different nature: cationic, nonionic, zwitterionic to get organoclays, enhances the adsorption efficiency but also extents the range of adsorbed organic molecules (Stockmeyer 1991, Stapleton et al 1994, Liu and Gonzalez 1999, El-Nahhal and Safi 2004, Groisman et al 2004, Shen 2004, Gao and Pedersen 2005, Polubesova et al 2005, Bekçi et al 2006, Deng et al 2006, Polubesova et al 2006, Guégan et al 2009, Guégan 2010, Sarkar et al 2010, Zhang et al 2010, Guégan 2011, Lee et al 2011, Guegan 2013, Zha et al 2013, Thiebault et al 2015, De Oliveira and Guégan 2016, De Oliveira et al 2017, De Oliveira et al 2018. Thus, numerous studies pointed out the interests of organoclays as adsorbents, going as far as to suggest these materials as perennial and realistic solutions for the remediation of wastewater or as tertiary treatment for drinking water (Stockmeyer 1991, Polubesova et al 2005, Polubesova et al 2006, Undabeytia et al 2008).…”

“…The efficient adsorption of diverse organic pollutants: pharmaceuticals, and other phytosanitary products in batch experimental conditions illustrates the interests of cationic organoclays (Alther 2002). Due to their dual hydrophilic-hydrophobic behaviors and possible cation exchange capacity, nonionic organoclays represent polyvalent adsorbents towards many organic products (Deng 2003, De Oliveira et al 2018). The previous batch adsorption experiments were conducted under unrealistic conditions (i.e.…”