Effects of surface Fe(III) oxides in a steel slag on the formation of humic-like dark-colored polymers by the polycondensation of humic precursors

Abstract

Carbonated furnace steel slag is effective in enhancing polycondensation reactions of humic precursors such as quinones, amino acids and saccharides. To obtain more detailed information concerning the nature of the catalytic sites on the surface of slag, a pristine slag sample was treated with HNO 3 , HF and NH 2 OH to alter the surface states.The catalytic activities for the formation of humic-like dark-colored polymers were significantly decreased for the samples treated with HNO 3 or HF compared to untreated slag. Because substantial amounts of iron were eluted as the result of the HNO 3 and HF treatments, the minerals remaining on the surface of steel slag were characterized by XRD and SEM, and the results were compared with untreated slag. XRD patterns indicated the significant decrease in Fe(III) oxide content, including magnetite and hematite, as the result of the HNO 3 and HF treatment. In addition, when untreated slag 2 was reacted with humic precursors, the hematite and magnetite were largely eluted as a result of the reaction. These results support the conclusion that Fe(III)-oxides on the surface of steel slag, such as hematite and magnetite, serve as catalytic sites for enhancing catalytic activity for the formation of humic-like dark colored-polymers from humic precursors.

Biodegradation and Structural Modification of Humic Acids in a Compost Induced by Fertilization with Steelmaking Slag under Coastal Seawater, as Detected by TMAH-py-GC/MS, EEM and HPSEC Analyses

“…In marine sediment, the transformation of humic substances could have occurred through complex reactions, including bacterial degradation, bacterial synthesis, and abiotic reaction with mineral matter having catalytic properties. 35 Nishimoto et al 15 demonstrated that the catalytic activity of steelmaking slag for the formation of humiclike substances in the autoclaved solution from catechol, glycine, and glucose, which were compared to the observation interval in this study (3 months); thus, we could not detect the intermediate of FL2 in this study. Furthermore, in the catalytic experiment, iron oxide on the surface of the steelmaking slag was reductively eluted.…”

“…11 It has been reported that terrestrial humic substances were degraded rapidly in the coastal area by marine bacteria 3,12,13 ; however, some researchers have reported that steelmaking slag enhanced polycondensation when it is incubated with low molecular organic compounds. 14,15 There is a limit in the previously reported data to understanding what occurred in HAs when they mixed with steelmaking slag in coastal seawater. 11 Thus, a detailed structural characterization of HAs would be predicted to provide crucial information about the fate of terrestrial HAs with steelmaking slag under coastal seawater.…”

Evaluation of the Effect of Humic Acids on the Reductive Elution of Fe from Fe₂O₃ in a Saline, Seawater-like Medium

“…A variety of side reactions could also occur by electron accepted HA with a neighboring HA, as described by the equations below: 9) HAred + HA HA + HA where HA' represent a structurally altered HA by selfoxidation. These side-reactions could inhibit the reductive Fe elution when the concentration of HA was enlarged.…”

The stabilization of tannery sludge and the character of humic acid-like during low temperature pyrolysis

“…Low-molecular-weight products such as phenols, phenolic acids, sugars, and amino acids may be formed by the degradation of proteins, polysaccharides, lignins, and polyphenols. Humic substances commonly are considered to be formed via polycondensation of low-molecular-weight products (Haumaier and Zech, 1995;Nishimoto et al, 2013). Zhao et al (2014) sequentially extracted different organic matter fractions by neutral solutions and acid solutions from the original biomass and their derived biochars to tracking the evolution of carbon forms.…”