The presence of an ionized carboxyl group in the widely used non-steroidal anti-inflammatory (NSAID) drug diclofenac
potassium results in a high mobility of diclofenac and in its low sorption under conditions of slow sand filtration or subsoil
passage. No diclofenac degradation was detected in pure water or sludge during one month. Tertiary treatments of wastewater
indicated that the effective removal of diclofenac was by reverse osmosis, but the removal by activated carbon was less
satisfactory. This study presents an efficient method for the removal of diclofenac from water by micelle–clay composites
that are positively charged, have a large surface area and include large hydrophobic domains. Adsorption of diclofenac
in dispersion by charcoal and a composite micelle (otadecyltrimethylammonium [ODTMA] and clay [montmorillonite])
was investigated. Analysis by the Langmuir isotherm revealed that charcoal had a somewhat larger number of adsorption
sites than the composite, but the latter had a significantly larger binding affinity for diclofenac. Filtration experiments on a
solution containing 300 ppm diclofenac demonstrated poor removal by activated carbon, in contrast to very efficient removal
by micelle–clay filters. In the latter case the weight of removed diclofenac exceeded half that of ODTMA in the filter.
Filtration of diclofenac solutions at concentrations of 8 and 80 ppb yielded almost complete removal at flow rates of 30 and
60mLmin−1. One kilogram of ODTMA in the micelle–clay filter has been estimated to remove more than 99% of diclofenac
from a solution of 100 ppb during passage of more than 100m3.