Magnetic heterogeneous catalytic ozonation: a new removal method for phenol in industrial wastewater

Abstract

In this study, a new strategy in catalytic ozonation removal method for degradation of phenol from industrial wastewater was investigated. Magnetic carbon nano composite as a novel catalyst was synthesized, characterized and then used in the catalytic ozonation process (COP) and compared with the single ozonation process (SOP). The influential parameters were all investigated. The results showed that the removal efficiency of phenol and COD (chemical oxygen demand) in COP (98.5%, 69.8%) was higher than those of SOP (78.7%, 50.5%) and the highest catalytic potential was achieved at optimal neutral pH. First order modeling demonstrated that the reactions were dependent on the concentration of catalyst, with kinetic constants varying from 0.023 1/min (catalyst = 0 g/L) to 0.071 1/min (catalyst = 4 g/L), whereby the optimum dosage of catalyst was found to be 2 g/L. Furthermore, the catalytic properties of the catalyst remained almost unchanged after 5-time reuse. The results regarding the biodegradability of the effluent showed that a 5-min reaction time in COP reduced the concentrations of phenol and COD to the acceptable levels for the efficient post-treatment in the SBR in a 4-h cycle period. Finally, this combined system is proven to be a technically effective method for treating phenolic contaminants.

Figure 1

Results of catalyst analysis. (a) XRD pattern of the AC/nano-Fe₃O₄ composites; (b) Energy dispersive X-ray analysis spectrum of the nano-composite; (c and d) Typical SEM micrographs of sample (×500 and × 50000, respectively).

Figure 2

The pH change for determination of pHzpc of the catalyst.

Figure 3

Effect of initial pH on removal efficiency of phenol. [Phenol]₀: 100 mg/L; Catalyst concentration of 0.5 g/L; reaction time: 5 min.

Figure 4

Effect of catalyst concentration on phenol degradation efficiency in SOP and COP. [Phenol]₀: 500 mg/L; initial pH of 8.0.

Figure 5

Effect of t-buanol radical scavenger on phenol degradation in the SOP and COP. [Phenol]₀: 500 mg/L; Catalyst concentration of 2 g/L; initial pH of 8.0.

Figure 6

Synergistic effect of catalyst on ozonation process.

Figure 7

The degree of degradation and mineralization of phenol in the COP under optimal condition.

Figure 8

Biodegradability of COP effluent under optimal condition.

Figure 9

Effect of catalyst reuse on phenol degradation in the COP.