Adsorption of diclofenac onto organoclays: Effects of surfactant and environmental (pH and temperature) conditions

Abstract

Among pharmaceutical products (PPs) recalcitrant to water treatments, diclofenac shows a high toxicity and remains at high concentration in natural aquatic environments. The aim of this study concerns the understanding of the adsorption mechanism of this anionic PP onto two organoclays prepared with two long-alkyl chains cationic surfactants showing different chemical nature for various experimental pH and temperature conditions. The experimental data obtained by a set of complementary techniques (X-ray diffraction, elemental analyses, gas chromatography coupled with mass spectrometry, and Fourier transform infrared spectroscopy) and the use of Langmuir, Freundlich and Dubinin-Radushkevish equation models, reveal that organoclays show a good affinity to diclofenac which is enhanced as the temperature is under 35°C and for pH above 4.5 (i.e. >pKa of diclofenac) while the chemical nature of surfactant appears to play a minor role. The thermodynamic parameters derived from the fitting procedure point out the strong electrostatic interaction with organic cations adsorbed within the interlayer space in the organoclays for the adsorption of diclofenac. This study stress out the application of organoclays for the adsorption of a recalcitrant PPs in numerous aquatic compartments that can be used as a complement with activated carbon for waste water treatment.

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

“…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).…”

Removal of Zinc Ions Using Hydroxyapatite and Study of Ultrasound Behavior of Aqueous Media

“…Materials such as zeolite [10], clay minerals [11,12] and other organo-derived clay materials [13,14,15] have been reported to be promising candidates in the treatment of wastewater due to their excellent surface characteristics. Recent studies have reported that phosphate minerals represent promising materials in the treatment of wastewaters for the removal of fluoride and heavy metals [16,17].…”

Confinement of a Nonionic Surfactant Membrane Within a Montmorillonite as a New Way to Prepare Organoclay Materials

“…Analysis of the supernatant (not shown here) revealed that no sodium were expelled pointing that intercalation of the surfactants preserve the compensating cations within the interlayer space of the clay mineral. Since these cations are kept and nonionic surfactants are intercalated in a normal bilayer or paraffin arrangement, the resulting organoclay displays a dual hydrophilic/hydrophobic behavior which enlarges the possibilities of adsorption for organic compounds 8,9 .…”

“…The resulting hybrid layered material exhibits a change of its chemical nature that switches from hydrophilic to hydrophobic. These modifications allow the adsorption of neutral organic compounds and offer numerous applications 1,[7][8][9] . The first is relied to environmental issue, where many authors suggested the use of organoclays as geochemical layers for the capture of hydrophobic pollutants which usually pass through the natural clay barrier implemented against pollution, or as sorbent materials for water remediation.…”