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The study of the adsorption of polycyclic aromatic hydrocarbons on microplastics (MPs) has attracted much attention as to how microplastics can act as carriers of these pollutants. Polyurethane (PU) is one of the MPs found in aquatic environments, containing different functional groups it can interact with polar and nonpolar molecules. PAH derivatives (dPAHs) present different properties and thus can be adsorbed by different interactions; thus, this study investigated the adsorption of fluorene (FLN), dibenzothiophene (DBT), dibenzofuran (DBF), and carbazole (CBZ) onto PU MP. The Langmuir, Freundlich, and BET isotherm models were examined, and the BET model best fitted. The adsorption was a nonspontaneous process, exothermic for mono- and multilayer formation for FLN, DBT, and CBZ, and endothermic for DBF monolayer formation. The adsorption monolayer was formed by van der Waals forces, H─bonding, and π─π interactions, while the formation of the multilayer can be explained by π─π and hydrophobic interactions. The pseudo-second-order model proved to be more consistent for the adsorption of dPAHs. The adsorption in artificial seawater shows no significant differences for the monolayer but favored the adsorption multilayer due to the salting-out effect. Due to the existence of several adsorption mechanisms, PU MP interacts with dPAHs in greater quantities when compared to a MP with a simpler structure., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Removal of Cr(VI) from the aqueous phase using numerous activated carbons (AC) has been broadly studied in the last decades. Nevertheless, the diversity of activation methods, AC properties, and adsorption conditions precludes the standardization of specific characteristics required to achieve better adsorption results. This work reviewed the pertinent literature on Cr(VI) adsorption onto AC published over the past four decades. Pearson's correlation matrix and principal component analysis (PCA) assisted in identifying the parameters and AC characteristics that have the greatest influence on the maximum adsorption capacity (q m ). Two hundred thirty-six adsorption assays were found reporting data on 110 ACs and different parameters. Of these, 39.8% of the studies contemplated the variables q m , pH, temperature (T), surface area (S BET ), micropore volume (V micro ), and mesopore volume (V meso ), and only 19.5% reported the point of zero charge (pH PZC ). Statistical analysis disclosed that S BET and V micro have a strong positive correlation with q m , while V meso , T, and pH show little or no correlation. The difference between pH and pH PZC (PZC diff ) indicated a significant anticorrelation with q m , thus evidencing that lower PZC diff values enhance adsorption. The findings are useful for all researchers that work with Cr(VI) adsorption on AC since they provide a start point concerning the required adsorbent characteristics and process conditions to be employed., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Naphthalene (NAP) is found as a pollutant in water, soil, and air, and adsorption is the most prominent removal process of this compound, among the methods studied. A study concerning the types of adsorbents and the parameters with the greatest influence on the adsorption process is interesting to direct future works on new adsorbents. The use of multivariate data analysis tools becomes an appealing way to compile data obtained from bibliographic reviews and to establish a behavior in NAP adsorption. This work aims to evaluate the parameters with greater influence on NAP adsorption process regarding adsorption capacity (qe exp ) with the principal component analysis (PCA), and to group common NAP adsorbents by chemical characteristics through hierarchical cluster analysis (HCA). The variables qe exp , S, [NAP] 0 , T, CT, and [Ads] were used to perform PCA with correlation matrix. For the HCA, the variables S, [NAP] 0 , T, CT, and [Ads] with average linkage method (UPGMA) and Euclidean distance were used. Through PCA, it is possible to infer that S and [NAP] 0 are the factors with greater influence in qe exp of NAP, while T, CT, and [Ads] have little correlation. PCA also shows that activated charcoal is the adsorbent with higher qe exp . HCA grouped the adsorbents into four groups by their chemical classes, except group A. Both PCA and HCA methods show themselves as potential tools to evaluate a data set of NAP adsorption processes.