Removal of refractory organics in dinitrodiazophenol industrial wastewater by an ultraviolet-coupled Fenton process

Abstract

A significant amount of biorefractory organic wastewater is generated during the production of dinitrodiazophenol (DDNP). In this study, ultraviolet light (254 nm) that was coupled with the Fenton (UV-Fenton) process was applied to treat refractory organics in DDNP industrial wastewater. The effects of key parameters (i.e., H 2 O 2 dose, Fe 2+ dosage, and initial pH) on the treatment efficacy for DDNP industrial wastewater by the UV-Fenton process was investigated systematically. Alcohol quenching experiments were carried out to identify reactive oxygen species in the UV-Fenton process. The treatment efficacy and degradation characteristics of refractory organics were studied and compared by using control experiments. Increasing H 2 O 2 and Fe 2+ doses could lead to improved treatment results to a different extent. A more intense reaction and better treatment results were achieved by using the UV-Fenton process at lower pH conditions. Under optimal conditions of H 2 O 2 dose ¼ 7.5 mL L À1 , Fe 2+ dosage ¼ 0.05 mM, and initial pH ¼ 5.0, the pseudo-first order constants k for chemical oxygen demand removal and color number removal were 0.18 min À1 and 1.24 min À1 , and the chemical oxygen demand and color number removal efficiencies were 74.24% and 99.94%, respectively. The treatment results for the UV-Fenton process were better than other processes under the same conditions, and a significant synergetic effect was observed for the UV-Fenton process. Alcohol quenching experiments indicated that the predominant reactive oxygen species in the UV-Fenton process was the hydroxyl radical ($OH). Because more $OH was produced, the UV-Fenton process exhibited a much better treatment performance in degrading and destroying organic structures (i.e., benzene rings, -NO 2 , and -N]N-). Furthermore, the biodegradability indicated by the biological oxygen demand/chemical oxygen demand ratio was improved considerably to 0.48 from 0.054. The good treatment performance by UV-Fenton allowed for a more efficient electrical energy consumption compared with the UV and UV-H 2 O 2 . This study provides a theoretical reference for DDNP industrial wastewater treatment by using the UV-Fenton process.

Enhancement of photo-Fenton catalytic activity with the assistance of oxalic acid on the kaolin–FeOOH system for the degradation of organic dyes

“…Dyes, as the prevalent organic contaminant in wastewater, are widely used in coloring and printing activities in paper, textile, leather, and cosmetic industries. [1][2][3][4] Dyecontaining wastewater can directly destroy the ecological balance of a water body and negatively affect human health. 5,6 It has been found that dyes are difficult to degrade by traditional biological methods owing to their complex structure with high molecular weight and cytotoxicity.…”

An assessment of the UV/nFe0/H2O2 system for the removal of refractory organics in the effluent produced by the biological treatment of landfill leachate

“…UV–vis spectroscopy can characterize the aromaticity and relative contents of characteristic organics and is widely applied to analyze the changes in the typical structure of aromatic organics in leachate (Ran & Li, 2019). Figure 3 shows the UV–vis spectra of the MBR effluent before and after treatment with the UV, nFe 0 , H 2 O 2 , UV/nFe 0 , nFe 0 /H 2 O 2 , UV/H 2 O 2 , and UV/nFe 0 /H 2 O 2 systems.…”

Safe Reuse of Landfill Leachates for Irrigation Purposes

“…At the UV/Fenton process, H2O2 is catalysed by Fe 2+ producing more OH radicals. Simultaneously, Fe 3+ can be transformed to Fe 2+ by UV, to catalyse H2O2, [15]. The main advantages of Fenton and UV/Fenton processes are the high reaction rate, the high efficiency in degrading pollutants, and mineralizing landfill leachates, [1].…”