Removal of Diclofenac Potassium from Wastewater Using Clay-Micelle Complex

In countries where fresh water is abundant treatment of wastewater is performed to sustain and protect the environment from pollution but in dry regions treatment of wastewater is essential to find alternative sources for fresh water thus overcoming in part the increased scarcity of this precious supply. Removing contaminants from wastewater can be performed using physical and chemical methods for primary treatment while, secondary wastewater treatment is accomplished by biological activity, which is designed to remove the biodegradable portion of organic constituents. Removal of recalcitrant substances often needs advanced treatments, such as ultrafiltration, ion exchange, adsorption and reverse osmosis. In this work we reported how a filter based on a micelle-clay complex can be incorporated in a multi-stage procedure of wastewater cleaning to remove organic persistent pollutants. Al-Quds University plant for wastewater treatment includes biological decontamination, two ultra-filtration (UF) hollow fibre modules with cut-off of 100 and 20 kDa, respectively, an activated carbon filter, and finally a reverse osmosis membrane (RO) [1]. The treated water is suitable for non-restricted irrigation. In this paper we report a relatively novel method for the removal diclofenac potassium (2-[(2,6-dichlorophenyl) amino]benzeneacetic acid) a polar acidic pharmaceuticals compound presents in river waters and wastewater plants, by using filters which include micelle-clay complexes. The micelle-clay composites, which we used, are positively charged, have large surface area and include large hydrophobic domains. It was shown by X-ray diffraction, electron microscopy and adsorption experiments that the characteristics of the micelle-clay complexes are different from those of organo-clay complexes, which are formed by adsorption of the same organic cation ODTMA (Octadecyl-trimethylammonium) as monomers [2]. The current study investigated the purification capability of two filters (20 x 5 cm) prepared mixing a clay-micelle complex (CMC) with different excess of quartz sand (1:100, or 1:50, w/w). The filtration capacity of 1:100 and 1:50 CMC-sand columns was tested using water passed through the first UF filter (cut-off 100 kDa) forgoing the 20 kDa membrane, the activated carbon filter, and the RO stage. The micelle-clay complex was prepared as suggested by Polubesova et al. (2005; 2006) using SWY-2 Wyoming Na-montmorillonite and octadecyltrimetylammonium bromide (ODTMA). Diclofenac potassium was obtained as a gift from Beit Jalah Pharmaceutical Company (Palestine). The CMC-sand columns were saturated with the solution permeated from the UF filter and spiked with varying concentration of diclofenac. Fractions were collected for assay of diclofenac potassium content and analyzed by LC/MS. Analysis of the Langmuir isotherms revealed that GAC had a somewhat larger number of adsorption sites than the composite, but the latter had a significantly stronger binding affinity for diclofenac. Filtration experiments of a solution that included 300 ppm diclofenac demonstrated a very efficient removal by clay-micelle filters. Filtration of diclofenac solutions at concentrations of 8 or 80 ppb yielded almost complete removal at flow rates of 30 and 60 mL/min. The estimate is that one kg of ODTMA in clay-micelle filter can remove more than 99% of diclofenac during a passage of more than 100 m3 of a solution having a concentration of 100 ppb of diclofena