In this work, the stability of imidacloprid in fresh water and sludge was studied. The results
revealed that the pesticide is unstable in both media. In freshwater, it underwent hydrolysis
whereas a degradation to several metabolites has been observed in sludge. The rate constants for
the hydrolysis and degradation at 25°C were 0.0.0067 and 0.0.0099 d–1, respectively. Monitoring
the degradation of imidacloprid in sludge by high-pressure liquid chromatography-mass spectrometry
(HPLC-MS) revealed that five metabolites have emerged during the study. These metabolites
include imidacloprid urea, imidacloprid-guanidine, 6-hydroxynicotinic acid, an olefin, and
5-hydroxy, 1-(6-chloro-3-pyridylmethyl)-2-(nitroimino)-imidazolidin-5-ol. The efficiency of Al-Quds
University Wastewater Treatment Plant towards the removal of imidacloprid indicates that the
ultrafiltration-hollow fiber unit was insufficient, whereas the ultrafiltration-spiral wound, activated
carbon, and reverse osmosis units were efficient for complete removal of the pesticide. Adsorption
experiments of imidacloprid using either activated charcoal or micelle-clay complex were found to
fit Langmuir isotherms better than Freundlich isotherm. The data demonstrate a higher Langmuir
Qmax value for the activated charcoal (126.6 mg g–1) when compared to the micelle-clay complex
(11.76 mg g–1). Filtration column experiments, conducted with mixed micelle-clay complex and sand
(using a ratio of 1/50 by mass) at a flow rate of 2 mL min–1 and influent concentration of 50 mg L–1,
revealed that a sufficient removal of imidacloprid was achieved in the first fraction of 100 mL
elution. These findings indicate that the adsorption technology using the micelle-clay complex
provides efficient removal of imidacloprid in continuous flow mode
