Abstract
Projection to Latent Structures (PLS) regression, a generalization of multiple linear regression, is used to model two datasets (40 observed data points each) of adsorption removal of three pharmaceutical compounds (PhCs), of different therapeutic classes and physical–chemical properties (carbamazepine, diclofenac, and sulfamethoxazole), from six real secondary effluents collected from wastewater treatment plants onto different powdered activated carbons (PACs). For the PLS regression, 25 descriptors were considered: 7 descriptors related to the PhCs properties, 10 descriptors related to the wastewaters properties (8 related to the organic matrix and 2 to the inorganic matrix), and 8 descriptors related to the PACs properties. This modelling approach showed good descriptive capability, showing that hydrophobic PhC-PAC interactions play the major role in the adsorption process, with the solvation energy and log Kow being the most suitable descriptors. The results also stress the importance of the competition effects of water dissolved organic matter (DOM), namely of its slightly hydrophobic compounds impacting the adsorption capacity or its charged hydrophilic compounds impacting the short-term adsorption, while the water inorganic matrix only appears to impact PAC adsorption capacity and not the short-term adsorption. For the pool of PACs tested, the results point to the BET area as a good descriptor of the PAC capacity, while the short-term adsorption kinetics appears to be better related to its supermicropore volume and density. The improvement in these PAC properties should be regarded as a way of refining their performance. The correlations obtained, involving the impact of water, PhC and PAC-related descriptors, show the existence of complex interactions that a univariate analysis is not sufficient to describe.
Highlights
Water is a critical transport system for the dissemination of contaminants of emerging concern (CECs) into the environment
The panoply of pharmaceutical compounds (PhCs) nowadays detected in wastewater and recipient water bodies is a challenge for wastewater treatment plants (WWTPs) that may need to improve their barriers against this class of organic compounds to comply with future legislation
For the Projection to Latent Structures (PLS) regression, 25 descriptors were considered: 7 descriptors related to the PhCs properties, 10 descriptors related to the wastewaters properties (8 related to the organic matrix and 2 to the inorganic matrix) and 8 descriptors related to the powdered activated carbons (PACs) properties
Summary
Water is a critical transport system for the dissemination of contaminants of emerging concern (CECs) into the environment. The European Union is aware of these problems as can be seen from the seven directives published in the last two decades, including pharmaceuticals from distinct therapeutic classes, pesticides and fungicides [1]. This issue is being addressed by the US Environmental Protection Agency that, in 2009 and 2016, added hormones to the drinking water contaminant candidate list. Studies reporting data on real wastewater perform univariate analysis, focusing mostly on activated carbon’s properties [3,4,5] or microcontaminants’ properties [6] When focusing on both domains, they are explored independently [7,8], and combined effects are not assessed
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