Clinoptilolite and palygorskite as sorbents of neutral emerging organic contaminants in treated wastewater: Sorption-desorption studies

- Sorption-desorption of EOCs to reactive materials was quantified.
- Neutral EOCs showed, in general, limited sorption.
- EOCs sorption onto clinoptilolite and palygorskite is irreversible and hysteretic.
- Sorption takes place mainly onto inorganic surfaces.
- CBZ (carbamazepine) and 4-AAA present the larger potential to infiltrate.

Water reuse for aquifer recharge could be an important route for the introduction of emerging organic contaminants (EOCs) into the environment. The installation of a Horizontal Permeable Reactive Barrier (H-PRB) could constitute a tertiary treatment process to remove EOCs from treated domestic wastewater prior to recharge activities. The sorption-desorption behaviour of six neutral EOCs present in treated domestic wastewater (acetaminophen, caffeine, carbamazepine, cotinine, 4-acetamidoantipyrine (4-AAA) and 4-formylaminoantipyrine (4-FAA)) has been evaluated. Clinoptilolite and palygorskite have been studied as sorbents to be installed in the H-PRB. Batch tests were carried out using an EOC initial concentration ranging from 5 to 100 μg L−1. Apart from acetaminophen and caffeine, both materials showed a limited sorption capacity of neutral EOCs (Kd = 0.63-5.42 L kg−1). In general, the experimental results show that EOCs exhibit a higher sorption affinity for clinoptilolite than for palygorskite. With the exception of carbamazepine, the sorption of the compounds occurs mainly by interactions with mineral surfaces as indicated by the comparison of the partition coefficients into organic matter and into mineral surfaces. According to the molecular geometry of the compounds and the sorption sequences observed, it appears that the dimensions of the organic molecules play a key role in the sorption process. All the studied EOCs exhibit irreversible sorption and sorption-desorption hysteresis.