Predictions of Gibbs free energies for the adsorption of polyaromatic and nitroaromatic environmental contaminants on carbonaceous materials: efficient computational approach

Single and Competitive Adsorption of Naphthalene, Phenanthrene, and Pyrene on Polystyrene Nanofibers

In this investigation, polystyrene (PS) nanofibers were prepared by electrospinning for the adsorption of naphthalene (Nap), phenanthrene (Phe), and pyrene (Pyr) from an aqueous solution. Surface morphology and physicochemical characteristics of PS nanofibers were analyzed using Fourier transform infrared spectroscopy (FT-IR) and point-of-zero-charge calorimetry (pHpzc). The effects of pH, ion concentration, and temperature on the adsorption were also investigated. The adsorption mechanism of target pollutants on PS nanofibers was investigated by a batch adsorption method. The adsorption kinetic studies showed that the adsorption of the three polycyclic aromatic hydrocarbons (PAHs) on PS nanofibers conformed to the pseudo-second-order kinetic model in both single and ternary systems. Meanwhile, in a single system, the three PAHs adsorbed on nanofibers were controlled by both intraparticle diffusion and liquid film diffusion, whereas the adsorption of Nap in a ternary system was controlled mainly by intraparticle diffusion, and the adsorption of Phe and Pyr was controlled mainly by liquid film diffusion. The isotherm data indicated that the Freundlich model performed better than the Langmuir model for the adsorptions of Nap, Phe, and Pyr on PS nanofibers in both the single system and the ternary system. Due to competitive adsorption, the adsorption capacities of Nap and Pyr on PS nanofibers decreased from 105.816 and 19.098 mg g-1 in the single system to 23.626 and 12.126 mg g-1 in the ternary system, but the adsorption of Phe was not affected. π-π interactions and pore filling may be jointly involved in the adsorption of PAHs on PS nanofibers.

Comparative Study of Quinolines and Tetrahydroquinolines Sorption on Various Sorbents from Water-Acetonitrile Solutions

The retention of 16 quinoline and tetrahydroquinoline derivatives was investigated under liquid chromatography conditions using porous graphitized carbon (PGC), octadecyl silica (ODS) and hypercrosslinked polystyrene (HCLP) stationary phases. For most of the analytes, retention on PGC was greater than on ODS, while retention on HCLP was even greater than on both ODS and PGC. The non-linearity of retention dependencies on acetonitrile content in the eluent was observed for compounds containing carboxy, hydrazo and methoxy groups. The relationships between quinolines structure and their retention factors were investigated. It was found that sorption on different sorbents correlated with different descriptors. Retention on ODS was found to be highly correlated with lipophilicity only while on HCLP it depended on both lipophilicity and polarizability of the sorbates. The feature of PGC was a good correlation of retention factors with topological and geometrical parameters. Additionally, ability of PGC to form OH…π bonds with hydroxymethylquinolines was found. The observed regularities allow one to rationally optimize the chromatographic analysis of structurally similar compounds, which is very important for bioactive substances.

Adsorption of nitrogen-containing compounds on hydroxylated α-quartz surfaces

Adsorption energies of various nitrogen-containing compounds (specifically, 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAn), and 3-nitro-1,2,4-triazole-5-one (NTO)) on the hydroxylated (001) and (100) α-quartz surfaces are computed. Different density functionals are utilized and both periodic as well as cluster approaches are applied. From the adsorption energies, partition coefficients on the considered α-quartz surfaces are derived. While TNT and DNT are preferably adsorbed on the (001) surface of α-quartz, NTO is rather located on both α-quartz surfaces.

Adsorption energies of different nitrogen-containing compounds on two hydroxylated (001) and (100) quartz surfaces are computed.

Unveiling Adsorption Mechanisms of Organic Pollutants onto Carbon Nanomaterials by Density Functional Theory Computations and Linear Free Energy Relationship Modeling

Predicting adsorption of organic pollutants onto carbon nanomaterials (CNMs) and understanding the adsorption mechanisms are of great importance to assess the environmental behavior and ecological risks of organic pollutants and CNMs. By means of density functional theory (DFT) computations, we investigated the adsorption of 38 organic molecules (aliphatic hydrocarbons, benzene and its derivatives, and polycyclic aromatic hydrocarbons) onto pristine graphene in both gaseous and aqueous phases. Polyparameter linear free energy relationships (pp-LFERs) were developed, which can be employed to predict adsorption energies of aliphatic and aromatic hydrocarbons on graphene. Based on the pp-LFERs, contributions of different interactions to the overall adsorption were estimated. As suggested by the pp-LFERs, the gaseous adsorption energies are mainly governed by dispersion and electrostatic interactions, while the aqueous adsorption energies are mainly determined by dispersion and hydrophobic interactions. It was also revealed that curvature of single-walled carbon nanotubes (SWNTs) exhibits more significant effects than the electronic properties (metallic or semiconducting) on gaseous adsorption energies, and graphene has stronger adsorption abilities than SWNTs. The developed models may pave a promising way for predicting adsorption of environmental chemicals onto CNMs with in silico techniques.

Modeling adsorption of brominated, chlorinated and mixed bromo/chloro-dibenzo-p-dioxins on C60 fullerene using Nano-QSPR

Many technological implementations in the field of nanotechnology have involved carbon nanomaterials, including fullerenes such as the buckminsterfullerene, C60. The unprecedented properties of such organic nanomaterials (in particular their large surface area) gained extensive attention for their potential use as organic pollutant sorbents. Sorption interactions can be very hazardous and useful at the same time. This work investigates the influence of halogenation by bromine and/or chlorine in dibenzo-p-dioxins on their sorption ability on the C60 fullerene surface. Halogenated dibenzo-p-dioxins (PXDDs, where X = Br or Cl) are ever-present in the environment and accidently produced in many technological processes in only approximately known quantities. If all combinatorial Br and/or Cl dioxin substitution possibilities are present in the environment, the experimental characterization and investigation of sorbent effectiveness is more than difficult. In this work, we have developed a quantitative structure-property relationship (QSPR) model (R2 = 0.998), predicting the adsorption energy [kcal/mol] for 1,701 PXDDs adsorbed on C60 (PXDD@C60). Based on the QSPR model reported herein, we concluded that the lowest energy PXDD@C60 complexes are those that the World Health Organization (WHO) considers to be less dangerous with respect to the aryl hydrocarbon receptor (AhR) toxicity mechanism. Therefore, the effectiveness of fullerenes as sorbent agents may be underestimated as sorption could be less effective for toxic congeners than previously believed.

First principles calculations of phenol adsorption on pristine and group III (B, Al, Ga) doped graphene layers

We studied the doping effects on the electronic and structural properties of graphene upon interaction with phenol. Calculations were performed within the periodic density functional theory as implemented in PWscf code of the Quantum Espresso package. Graphene layers were modeled using 3 × 3 and 4 × 4 periodic supercells. Doping was explored considering boron (B), aluminum (Al) and gallium (Ga) atoms. The results showed that pristine graphene and graphene doped with B atoms interacting with phenol display similar structural and electronic properties, exhibiting weak physical interactions. However, when the doping is with Al or Ga , the results are quite different. Al and Ga doping induces a stronger interaction between the phenol molecule and the doped layer, yielding chemical adsorption. In all cases, the zero gap energy characteristic is unchanged. The Dirac lineal dispersion relation is preserved in both pristine graphene and B-doped graphene.

PEI@Mg2SiO4: an efficient carbon dioxide and nitrophenol compounds adsorbing material

PEI@Mg₂SiO₄: an efficient carbon dioxide and nitrophenol compounds adsorbing material.