Impact of De-Ashing Humic Acid and Humin on Organic Matter Structural Properties and Sorption Mechanisms of Phenanthrene

Abstract

Organic matter-mineral interactions greatly affect the fate of hydrophobic organic compounds (HOCs) in the environment. In the present study, the impact of organic matter-mineral interaction on sorption of phenanthrene (PHE) by the original and de-ashed humic acids (HAs) and humin (HM) was examined. After de-ashing treatment, the overall polarity of organic matter in HAs and HM consistently decreased. Differently, the surface polarity of HAs increased but that of HM decreased. No correlation between K(oc) values of PHE by all tested sorbents and their bulk polarity was observed due to inaccessibility of a portion of interior sorption domains. The inaccessibility of interior sorption domains in HAs and HM was partly due to the crystalline structure in organic matter as indicated by differential scanning calorimetric (DSC) and ¹³C NMR data and the interference from minerals. A good correlation between surface polarity of the original and de-ashed HAs and HMs and their K(oc) values for PHE indicated its importance in HOC sorption. Dissimilar changes in surface polarity of HAs and HM after de-ashing treatment can be ascribed to the distinct interactions between organic matter and minerals. The solid-state ¹³C NMR, XPS, and elemental composition data of all tested sorbents revealed that a larger fraction of O atoms in HAs were involved in organic matter-mineral interaction as compared to HM. Results of this work highlight the importance of soil organic matter (SOM)-mineral interactions, surface polarity, and microscaled domain arrangement of SOM in HOC sorption.

Properties of the plant- and manure-derived biochars and their sorption of dibutyl phthalate and phenanthrene

“…Ash content was determined by heating biochars at 750°C for 4 h. The microporosity and cumulative surface area (CO 2 -SA) of biochars were obtained by Autosorb-1 gas analyzer (Quantachrome Instrument Corp., Boynton Beach, FL) using CO 2 isotherm at 273 K49. Surface elemental composition (e.g., C, O, N, and Si) as well as the carbon-based functional group distribution of biochars were examined by using X-ray photoelectron spectroscopy (XPS) with a Kratos Axis Ultra electron spectrometer using monochromated Al K α source operated at 225 W, including an elemental survey scan and a high-resolution scan at the C 1s edge50. Fourier transform infrared (FTIR) spectroscopy spectra were recorded by a Nexus 670 FTIR spectrophotometer (Thermo Nicolet Corporation, US).…”

“…grass biochar that contains substantial silica in the form of phytoliths)7, the sorption properties of the ash component have not generally been considered. Especially, the recent studies demonstrated that the minerals within both biochars and soils have influence on the spatial arrangement or conformation of their organic matter (OM), in turn, which impacts on the sorption of phenanthrene (PHE) by the biochars or soils28293031. It is hypothesized that the minerals of biochars should play different role in the sorption between PAEs and PHE due to their different chemical properties, and also expected that the properties of ANIBs and PLABs should have different influence on sorption of PAEs.…”

Sorption of four hydrophobic organic contaminants by biochars derived from maize straw, wood dust and swine manure at different pyrolytic temperatures

“…Surface area (CO 2 -SA) using CO 2 isotherm at 273 K was detected by gas adsorption using an Autosorb-1 gas analyzer (Quantachorme Instrument Corp., Boynton Beach, FL) and calculated using nonlocal density functional theory (NLDFT) (Braida et al, 2003). The surface functionalities and domain spatial arrangement of samples were determined using X-ray photoelectron spectra (XPS) with a Kratos Axis Ultra electron spectrometer using monochromated Al Ka source operated at 225 W, and more detailed information of XPS characterization was described elsewhere (Yang et al, 2011;Sun et al, 2013). (The C 1s binding energy levels were assigned as following: 284.9 ev for CeC, 286.5 ev for CeO, 287.9 ev for C]O, and 289.4 ev for COO.…”

Impact of humic acid coating on sorption of naphthalene by biochars

“…Details for selecting this compound as sorbate are summarized in the Supporting Information (SI). The 14 C-labeled and non-labeled Naph were purchased from Sigma-Aldrich Chemical Co. Ltd. Humic acids were progressively extracted from a peat soil collected from Amherst, Massachusetts using 0.1 M Na 2 P 4 O 7 for the first to sixth fractions and 0.1 M NaOH for the seventh to ninth fractions [26]. As there was little difference between the composition of the first and second fractions, both fractions were pooled and labeled as HA1.…”