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Abstract  

Catalytic ozonation has recently been used as a new means of contaminant removal from water and wastewater. In this study, bone charcoal (BC), a new catalyst prepared under laboratory conditions, was used to catalyze the ozonation of humic substances (HS) in aqueous solutions. The catalytic effect of bone charcoal and the relevant parameters of this ozonation process (solution pH, temperature, scavenger effect, humic acids concentration and BC dosage) were investigated. In the catalytic ozonation experiments, the degradation kinetics was investigated. The reaction rate and the rate constant were determined. The results showed that using a BC catalyst in the ozonation of HS produced a 1.43- and 1.56-fold increase in reaction rates compared to the sole ozonation processes (SOP) under acidic and alkaline conditions, respectively. Furthermore, the applicability of heterogeneous catalytic ozonation with bone charcoal (HCOBC) to humic acid degradation was evaluated by performing comparisons with H2O2, O3, O3/H2O2 and O3/H2O2/BC processes. With the use of the Arrhenius equation, the activation energy (Ea) was calculated to be 10 kJ mol−1. The results also showed that under the different temperatures, the reaction of the catalytic ozonation of HS was defined as diffusion controlled in accordance with the activation energy. These findings suggest that the HCOBC can be applied as an efficient and feasible method for the removal of HS from water.

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Abstract  

This study of photodegradation of the antibiotic chloromycetin (Cm) in aqueous solution by direct and indirect photolysis included photolysis under UV-C light (λ = 254 nm) and photo-oxidation under UV–vis light (λ ≥ 365 nm) in the presence of iron and humic acid. The factors affecting Cm degradation were studied and are described in detail, including initial pH, ionic strength and initial concentrations of iron and humic acid. Results showed that a degradation efficiency up to 90% was achieved by direct photolysis of Cm at pH 5–7 and the calculated quantum yield was 0.084. Higher salt content (NaCl, 0.01–0.5 M) was found to benefit direct photolysis. Indirect photolysis of Cm in the presence of iron(III) formed OH radicals at pH ~ 3. Under UV–vis light, increased pH resulted in a significant decrease in the efficiency of indirect photolysis. Direct and indirect photolysis reactions both followed a pseudo first-order kinetic law. Humic acid tended to inhibit the photodegradation of Cm under the conditions of this work, implying that photosensitization of humic acid did not play any role in the photodegradation.

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. Mjengera and Mkongo [ 32 ] reported that BC prepared in 400 °C could be used to remove fluoride from water. This sorbent can also be used as a catalyst in ozonation systems for humic acid removal from water [ 33 ]. Analysis of surface

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.C. , Van Rensburg, C.E.J. , Van Ryssen, J.B.J., Casey, N.H. & Rottinghaus, G.E. (2006): In vitro and in vivo assessment of humic acid as an aflatoxin binder in broiler chickens. Biomin World Nutrition Forum . Vienna (Abstr. 12

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humic-acid and ligninsulfonate. Anal. Chem. , 55 , 643–648. Wold S. Partial least-squares methods for spectrofluorimetric analysis of mixtures of humic-acid and ligninsulfonate

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