10The effects of reducing agents on the degradation of 2,4,6-tribromophennol (TrBP) 11 were investigated in a heterogeneous Fenton-like system using an iron-loaded natural 12 zeolite (Fe-Z). The catalytic activity for TrBP oxidation in the presence of the Fe-Z and

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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.

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Polycondensation reactions between amino acids and phenols are one of the pathways for the formation of humic substances, and clay minerals are able to catalyse these reactions. To investigate the catalytic power of allophane, an allophane fraction (ALF) was separated from weathered pumice (WP) that contained imogolite as an impurity by taking advantage of differences in sedimentation velocity. The iron content in the separated ALF was increased by up to 3.0% compared to that in the starting WP (1.3%), and the ALF was further treated with sodium dithionate and citric acid (ALF-DC) to remove the iron. The catalytic powers of WP, ALF and ALF-DC were evaluated, based on the degree of darkening of reaction mixtures from polycondensation reactions between catechol and tryptophan, model compounds for precursors of humic substances. The catalytic power for ALF was significantly higher than the corresponding values for WP and ALF-DC. This can be attributed to the high iron content of the ALF, which serves as a Lewis acid that can enhance nucleophilic reactions which occur during the polycondensation reactions.

> HuLS-bentonite complex was prepared via polycondensation of humic precursors. > HuLS had more aliphatic character than HaLS that was a water-soluble fraction. > XRD patterns demonstrated the intercalation of HuLS into the bentonite. > The prepared HuLS-bentonite complex had a strong affinity to pentachlorophenol. > *Highlights (for review)