Isolation and Fractionation of Humic Substances Present in Water With the Use of Anion-Exchange Resins and Ultrafiltration

Abstract

Natural water treatment requires emphasis on humic substances (HS) removal because of disinfection by-product formation possibilities. Thus, detailed research on HS structure and properties is necessary. Two model solutions of different origin were used in this study. A100, A200, A400, A870 and DEAE-cellulose anion exchange resins were used for the one-stage isolation of HS. Model solutions and eluates from the respective resins were subjected to filtration using regenerated cellulose 1, 5 and 10 kDa MWCO ultrafiltration membranes. The results allowed ranking of analyzed anionites according to the isolation capacity of HS: DEAE >> A870 > A100 > A400 > A200. Analysis of the HS molecular size distribution shows that hydrophilic compounds of low molecular weight (MW) are dominant in natural water, whereas in the Aldrich humic acid solution and in the eluates after each resin, large MW hydrophobic compounds are predominant.

Chemical Characteristics of Humic Substances in Nature

“…However, unique classes of residual biomolecules have been identified by selective extractions and chemical fractionation and are represented by alkanoic and hydroxy-alkanoic acids, resins, waxes, lignin residues, sugars, and peptides. Table 1 shows several methods that are used in the extraction of humic substances, such as lyophilization, co-precipitation, ultrafiltration, solvent extraction and resins [30,31]. The separation of humic substance in water by adsorption chromatography has been widely employed [14,32,33].…”

“…For this purpose, a standard absorbance vs. concentration line is constructed and thus it is possible to determine the concentration of humic substances based on the absorbance readings of the samples (aqueous solution of humic substances). The authors in [31] performed the isolation of humic substances from water and used this technique to determine the content of aromatic compounds and the color intensity of humic substances as well as the analysis of dissolved organic carbon for determine the total concentration of humic substances. Others authors, as cited in [36,37], also used these techniques in their studies of humic substances.…”

Ion-Exchange Technology for Lactic Acid Recovery in Downstream Processing: Equilibrium and Kinetic Parameters

“…To our knowledge, the resins tested in this work were not studied for lactic acid sorption/desorption previously. For instance, resins A100, MN100 and MP64 have been applied for the recovery of metals [48], halogenated compounds [49], aurocyanide extraction [50], natural organic matter [51,52], dissolved organic matter removal [53] and humic substances removal [54], but no for lactic acid recovery. The sorption capacity was 5.6 ± 0.3 mg/g (average) for all anion exchange resins tested at 1 g/L of lactic acid, whereas it increased up to from 34.3 mg/g, using the MN100 resin, to 57.5 mg/g for A100 resin.…”

“…To our knowledge, the resins tested in this work were not studied for lactic acid sorption/desorption previously. For instance, resins A100, MN100 and MP64 have been applied for the recovery of metals [48], halogenated compounds [49], aurocyanide extraction [50], natural organic matter [51,52], dissolved organic matter removal [53] and humic substances removal [54], but no for lactic acid recovery.…”