Key Factors for Activated Carbon Adsorption of Pharmaceutical Compounds from Wastewaters: A Multivariate Modelling Approach

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.

Preparation and Characterization of Pulp and Paper Mill Sludge-Activated Biochars Using Alkaline Activation: A Box–Behnken Design Approach

“…The hydrophobicity index of the biochars can substantially influence their performance as adsorbents because, in the adsorption process, hydrophilic and hydrophobic interactions between adsorbent and adsorbate play an essential role. , …”

Enhanced Adsorption of Tetracycline by Thermal Modification of Coconut Shell-Based Activated Carbon

“…The components often detected in water and wastewater are cations, such as Na + , K + , Ca 2+ , NH 4 + , and Mg 2+ , anions, such as NO 3 − , PO 4 3 − , SO 4 2 − , and HCO 3 − , and natural organic matter (NOM) [ 76 ]. It is thought that the inorganic ions would not significantly affect the TC adsorption by PAC800 because they are not readily adsorbed onto ACs [ 77 , 78 ], resulting in negligible competition. On the contrary, the effect of NOM must be evaluated before real applications.…”

“…On the contrary, the effect of NOM must be evaluated before real applications. NOM is slightly hydrophobic and can compete with TC for the adsorption sites on ACs [ 78 ], seriously affecting the adsorption. However, adsorption is not only affected by the water matrix but also by the property of the adsorbent significantly, such as functional groups, graphitic structures, and pore structures [ 28 , 37 , 78 ].…”

“…NOM is slightly hydrophobic and can compete with TC for the adsorption sites on ACs [ 78 ], seriously affecting the adsorption. However, adsorption is not only affected by the water matrix but also by the property of the adsorbent significantly, such as functional groups, graphitic structures, and pore structures [ 28 , 37 , 78 ]. Therefore, it is thought that the matrix effects would be suppressed via the proper modification of ACs.…”

Immobilization of Microcystin by the Hydrogel–Biochar Composite to Enhance Biodegradation during Drinking Water Treatment

“…A review of materials for potential immobilization of biotoxin indicates many natural adsorbents, such as activated carbon, graphene oxide, biochar (BC), silica, and clays, have been previously tested for MC-LR captivation. − They indiscriminately adsorb the toxin along with natural organic matter (NOM), inorganic ions, and other water constituents. − NOM is typically present at significantly higher concentrations than MC-LR in natural freshwater, leading to competition for adsorption sites. Due to the higher aromaticity compared to MC-LR, some NOM readily form bonds with the active sites of various adsorbents (e.g., activated carbon, graphene oxide, and BC) through π–π interactions.…”