Degradation of humic acids through heterogeneous catalytic ozonation with bone charcoal

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 H 2 O 2 , O 3 , O 3 /H 2 O 2 and O 3 /H 2 O 2 /BC processes. With the use of the Arrhenius equation, the activation energy (E a ) 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.

Efficient degradation of fulvic acids in water by catalytic ozonation with CeO2/AC

“…It can be observed that the addition of AC and CeO 2 /AC catalysts improves the degradation efficiency of FA. The enhanced degradation efficiency of FA must be mainly attributed to an increase in the ozone decomposition into · OH radicals . In contrast, the adsorption by AC and 5%‐Ce(III)/AC‐H 2 ‐450 only contributed to 3.6% and 4.1% removal of FA after 30 min.…”

“…In the presence of Fe/MgO catalyst, ozonation of humic acids induced a significant reduction in UV absorbance compared with ozonation alone . Addition of perfluorooctylalumina or bone charcoal in an ozonation process greatly accelerated the rate of HA degradation . Accordingly, catalysts can significantly improve the removal efficiency of HA from water in the ozonation process.…”

Adsorption kinetics and isotherm of methylene blue and its removal from aqueous solution using bone charcoal

“…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].…”

Kinetics and Mechanism of Humic Acids Degradation by Ozone in the Presence of CeO2/AC

“…The negative effect of a free radical scavenger t-BuOH suggested that the • OH radicals were involved in catalytic ozonation of HA (Chiang et al 2006;Mortazavi et al 2010).…”

“…And the contributions of direct oxidation by ozone molecules and indirect oxidation by hydroxyl radicals depended on the solution pH (Chiang et al 2006). Moreover, the addition of solid catalysts such as Fe/MgO, perfluorooctylalumina and bone charcoal promoted the decomposition of ozone into • OH radicals and, therefore, greatly accelerated the rate of HA degradation compared to sole ozonation (Lee et al 2005;Ma and Chang 2010;Mortazavi et al 2010).…”