Polyurethane foams containing residues of petroleum industry catalysts as recoverable pH-sensitive sorbents for aqueous pesticides.

To investigate ways of mitigating the contamination of water with herbicides, which is a well-recognized global problem, we prepared natural resource-based polyurethane foams containing different amounts of petroleum industry catalyst residue (RC) and tested them as atrazine (ATZ, a common herbicide) sorbents in aqueous solutions. The above sorbents were characterized by infrared spectroscopy, electron microscopy, microtomography, thermogravimetric analysis, and X-ray diffraction. The adsorption/desorption of ATZ thereon was investigated as a function of foam composition, pH, initial ATZ concentration, and time. The obtained results showed that the porosity, pore size, and pore interconnectivity of the prepared sorbents were well suited for optimal ATZ removal. At pH 2, foams with high RC contents achieved higher ATZ removal efficiencies (e.g., 25%) than the pristine foam (12%). Conversely, ATZ removal was disfavored at high pH, which was attributed to restricted ATZ-sorbent interactions due to changes in the sorbent surface charge. The presence of other species (such as pectin, which is usually found in fruits) did not interfere with ATZ removal. ATZ desorption was most effective at high pH, enabling the regeneration and re-use of sorbents and thus reducing large-scale application costs.