Removal of phenol from wastewater by high-gravity intensified heterogeneous catalytic ozonation with activated carbon.

Jingwen Zhang,Jiaxin Jing,Xin Ding,Shengjuan Shao,Zhixing Li,Weizhou Jiao,Youzhi Liu

doi:10.1007/s11356-021-18093-y

Jingwen Zhang, Jiaxin Jing + Show 5 more

Open Access

https://doi.org/10.1007/s11356-021-18093-y

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Abstract

In this study, the high-gravity technique is used to intensify the heterogeneous catalytic ozonation with activated carbon (AC) as the catalyst for removal of phenol from wastewater in a rotating packed bed (RPB), and the effects of high-gravity factor, inlet O3 concentration, liquid-gas ratio, and initial pH on the degradation and mineralization of phenol at room temperature are investigated. It is revealed that the degradation rate of phenol reaches 100% at 10min and the removal rate of total organic carbon (TOC) reaches 91% at 40min under the conditions of high-gravity factor β = 40, inlet O3 concentration = 90mg·L-1, liquid flow rate = 80 L·h-1, and initial pH = 11. Compared with the bubbling reactor (BR)/O3/AC and RPB/O3 systems, the mineralization rate of phenol by the RPB/O3/AC system is increased by 24.78% and 34.77%, respectively. Free radical quenching experiments are performed using tertiary butanol (TBA) and benzoquinone (BQ) as scavengers of ·OH and O2-, respectively. It is shown that the degradation and mineralization of phenol are attributed to the direct ozonation and the indirect oxidation by ·OH generated from the decomposition of O3 adsorbed on AC surface, respectively. ·OH and O2·- are also detected by electron paramagnetic resonance (EPR). Thus, it is concluded that AC-catalyzed ozonation and high-gravity technique have a synergistic effect on ·OH initiation, which in turn can significantly improve the degradation and mineralization of organic wastewater.

Highlights

Phenol is a toxic organic compound with numerous applications in coal chemical, petrochemical, papermaking, dyeing and pharmaceutical industries (Yang et al 2019a)
It is shown that the degradation and mineralization of phenol are respectively attributed to the direct ozonation and the indirect oxidation by ·OH generated from the decomposition of O3 adsorbed on activated carbon (AC) surface. OH and O2− are detected by electron paramagnetic resonance (EPR)
O3 molecules can react with oxygen-containing groups on the AC surface to form a five-membered ring structure via hydrogen bonds, which in turn is decomposed into free radicals via electron transfer

Summary

Introduction

Phenol is a toxic organic compound with numerous applications in coal chemical, petrochemical, papermaking, dyeing and pharmaceutical industries (Yang et al 2019a). It is highly carcinogenic, teratogenic and mutagenic in nature that may cause severe damage to both humans and animals even in a low amount (Naguib and Badawy 2019). Catalytic ozonation has gained considerable attention as an efficient wastewater treatment method, whereby ·OH can be produced from catalytic decomposition of O3, which has strong oxidative capacity (E0 = 2.8eV) and reacts non-selectively with organic pollutants present in wastewater(Jaafarzadeh et al 2017). Most catalysts used in heterogeneous catalytic ozonation have the advantages of high catalytic activity(Ahmed et al 2010), easy separation from the liquid phase, reusable, and no secondary pollution to the environment (Nawrocki et al 2013; Wang et al 2020)

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