Adsorption Mechanism Of Organic Compounds Research Articles

Prediction of polydimethylsiloxane-water partition coefficients based on the pp-LFER and QSAR models

Obtaining accurate measurements of the partition coefficients between sorbent materials and water is of major importance for the analysis of the adsorption behavior and dissolved concentrations of organic compounds in the environment. In the passive-sampling approach, polydimethylsiloxane (PDMS) has a wide range of applications. Therefore, we established a poly-parameter linear-free energy relationship (pp-LFER) and a quantitative structure-activity relationship (QSAR) model to predict the log KPDMS-w values for a large dataset of 290 organic chemicals from 11 diverse classes. For the pp-LFER model, E (excess molar refractivity), A (molecular H-bond donor ability), V (McGowan volume), and B (the H-bond acceptor properties) were introduced as the main correlated variables. However, the obtained model is much limited in terms of acquiring available descriptors. For this reason, we developed a QSAR model, and CrippenLogP (Crippen octanol-water partition coefficient), RNCG (Relative negative charge-most negative charge/total negative charge), ATSC4e (Centered Broto-Moreau autocorrelation-lag4/weighted by Sanderson electronegativities) and GATS6p (Geary autocorrelation-lag6/weighted by polarizabilities) were selected as the significant parameters. The predictive power and functional reliability of the presented models were confirmed with validation methods as described in previous studies. The adjusted determination coefficients (R2adj) of 0.851 and 0.922 and leave-one-out cross-validated (Q2LOO) of 0.841 and 0.907 revealed that the models have good predictive power and generalizability. Thus, the proposed models are simple yet accurate tools for predicting the log KPDMS-w values and providing new insights to further understand the adsorption mechanism of organic compounds.

Adsorption and correlations of selected aromatic compounds on a KOH-activated carbon with large surface area

Knowledge of adsorption mechanism and behavior of organic compounds by KOH-activated carbons (KOH-ACs) from wastewater is crucial to its environmental application in wastewater treatment as adsorbent. A superior adsorbent, KOH-activated carbon (KOH-AC), with large surface area (3143m2/g), total pore volume of 2.03cm3/g, relatively low micropore fraction of 53.2%, and having adsorption capacities of organic compounds up to >1000mg/g, was prepared. It is an adsorbent significantly different with common ACs because the molecular sieving effect, widely observed for common ACs, is insignificant for KOH-AC. This difference could be attributed to the lower micropore fraction of KOH-AC than common ACs. A negative relationship of adsorption capacity of 25 aromatic compounds (including phenols, anilines, nitrobenzenes and polycyclic aromatic hydrocarbons) with chemical melting point was observed, suggesting that adsorption is dependent on the packing efficiency and stacking density of molecules on KOH-AC. A linear solvation energy relationships of adsorption affinity of 25 aromatic compounds with solute solvatochromic parameters was also observed, that can be used to quantify the contributions of π-π interaction, hydrogen-bonding interaction and hydrophobic effect to adsorption on KOH-AC. Combined with the reported results of adsorption of organic compounds on carbon nanotubes and biochars, it was also observed that external surface area of adsorbents is controlling the packing efficiency and stacking density of molecules on adsorbents and thus affecting adsorption capacity of organic compounds. Moreover, micropore surface area and the fraction of micropores are the adsorbent properties mainly affecting adsorption affinity of organic compounds. The observations and the developed correlations in this study would be helpful in the application of KOH-AC as superior adsorbent by enhancing the understanding of adsorption mechanisms of organic compounds on KOH-AC and by giving a method to predict the adsorption behaviors.

Negative effect of dissolved organic compounds on settling behavior of synthetic monominerals in red mud

Hydration grossular and hematite monominerals were synthesized. The effects of dissolved organic compounds (including sodium formate, sodium acetate, sodium oxalate, sodium salicylate or disodium phthalate) on the settling performance of hydration grossular or hematite slurries were studied. The settling of the slurries was also investigated with the addition of sodium polyacrylate (PAAS) or hydroxamated polyacrylamide flocculant (HCPAM). The adsorption mechanism of organic compounds on monominerals surfaces was studied by FT-IR and XPS, respectively. A deterioration in settling is observed in order of disodium phthalate>sodium salicylate>sodium oxalate>sodium formate (or sodium acetate). Moreover, PAAS can efficiently eliminate the negative effects of organic compounds on the settling performance of the hydration grossular slurry. HCPAM can efficiently eliminate the negative effects of sodium formate, sodium acetate and sodium oxalate on the settling performance of the hematite slurry, but it only partially improves the settling performance of hematite slurry containing sodium salicylate or disodium phthalate. FT-IR and XPS results show that organic compounds are physically adsorbed on hydration grossular surface, and chemisorptions of organic compounds occur on hematite surface with a bidentate chelating complex.

クリーンルーム中の有機物質のウェハ表面吸着機構

In this study, organic compounds in a cleanroom air and on silicon (Si) wafer surfaces were investigated by using thermal desorption-atmospheric pressure ionization mass spectroscopy (TD-APIMS). Si wafers with hydrogen terminate and with native oxygen exposed in a cleanroom were analyzed. As a result, chained hydrocarbons such as C2-C5 alkanes were detected with higher concentrations than phthalates such as DOP and DBF from both Si wafers. And the relationship between the concentration of organic gas species in the cleanroom and organic compounds on Si wafer surfaces was discussed on the tendency of the organic compound adsorption on Si wafer surface. The adsorption mechanisms of organic compounds on Si wafers were discussed by thermal desorption spectra. Based on these results, the adsorption hierarchy model of organic compounds on Si wafer surfaces was proposed.

Adsorption Mechanisms of Organic Compounds on Si Wafer Surfaces

Adsorption Mechanisms of Organic Compounds on Si Wafer Surfaces

Retention of organic compounds on carbon adsorbents

Liquid adsorption chromatography of organic compounds (aromatic hydrocarbons, acids, phenol, anisole, benzaldehyde and acetophenone) was studied at 293 K on two carbon stationary phases. Acetonitrile, acetonitrile—water (2:3) and n-heptane were used as mobile phases. Capacity factors and Henry's constants of adsorption equilibrium of aromatic compounds were calculated from the values of their retention volumes. The influence of the chemical structure of organic compounds, the surface structure of the stationary phases and the nature of the mobile phases on retention parameters was established. The differences in adsorption mechanism of organic compounds on hydroxylated and modified silica and carbon stationary phases are discussed.