Co/Fe and Co/Al layered double oxides ozone catalyst for the deep degradation of aniline: Preparation, characterization and kinetic model

https://doi.org/10.1016/j.scitotenv.2020.136982Get rights and content

Highlights

  • Co/Fe and Co/Al-LDO catalysts were obtained by coprecipitation-calcination methods.

  • Co/Fe and Co/Al-LDO catalysts have typical lamellar structures.

  • The aniline kinetics model by the bimetallic ozone catalysts was established.

Abstract

In this work, Co/Fe and Co/Al layered double oxides (Co/Fe-LDO and Co/Al- LDO)ozone catalysts were obtained from Co/Fe and Co/Al layered double hydroxides intermediates (Co/Fe-LDH and Co/Al-LDH). Firstly, the optimal preparation parameters of the two intermediates were determined, then the morphology and mineralogy microstructure of the derived Co/Fe-LDO and Co/Al- LDO ozone catalysts were systematically studied. Finally, the reaction kinetics of the two ozone catalysts for the deep degradation of aniline wastewater in catalysts/ozone systems were established. The results showed that the optimal preparation conditions were set as pH 12, temperature 60 °C, cobalt‑iron ratio 3:1 for Co/Fe-LDH intermediate, and pH 12, temperature 70 °C, cobalt‑aluminum ratio 3:1 for Co/Al-LDH intermediate. During calcination treatment, the dehydration and recrystallization effect impelled LDH intermediate to form LDO catalyst. The derived ozone catalysts Co/Fe-LDO and Co/Al-LDO possess layered structure, and Co species was mainly based on Co3O4 as the main mineral phase of the two ozone catalysts. The addition of catalyst can realize the deep ozonation catalysis of aniline wastewater. The kinetic models established on the aniline oxidized by ozone or catalyst/ozone systems were both fitted the first-order reactions, and the reaction activation energy for CODCr and TOC degradation were significantly reduced in catalyst/ozone system.

Introduction

As a typical and basic chemical benzene series compound, aniline is widely utilized in dye synthesis, pharmaceutical fabrication, rubber vulcanization manufacturing, military industrial production and other fields (Jiang et al., 2016; Koyuncu and Kul, 2019; Bombuwala Dewage et al., 2019; Dias et al., 2019). The residual aniline in wastewater has strong bio-toxicity with typical “carcinogenic, teratogenic and mutagenesis” properties to human body (Ferreiro et al., 2019; Gan et al., 2019; Xue et al., 2019). As a result, U.S. EPA and China EPA lists aniline as one of 129 kinds of pollutants to be controlled.

Currently, the treatment methods of aniline wastewater mainly include adsorption, biodegradation, membrane distillation, photocatalytic oxidation, ultrasonic degradation, etc. Ozonation (Bombuwala Dewage et al., 2019; Gan et al., 2019; Li et al., 2017; Pang et al., 2019; Dvořák et al., 2014; Gómeza et al., 2009), which has been evidenced an efficient option, is often employed as the direct treatment method to disposal the residual aniline. However, the pure ozone-oxidizing aniline method has a low ozone utilization rate, and extra ozone needs to be treated to prevent the secondary pollution of atmospheric environment (Wang et al., 2019; Jiao et al., 2019; Fu et al., 2019; Gao et al., 2019). On the other hand, because of the stringent discharged policy in china (Jiang et al., 2016; Li et al., 2017; Jiao et al., 2019), not only the aniline but also CODCr and TOC is required to be controlled under an extremely low level. Hence, the realization of deep ozonation of aniline is urgent for China's chemical industries. Catalytic ozone-oxidized aniline method is an effective method to improve the ozone utilization, increase the aniline removal rate and achieve the deep ozonation by using specific catalysts, e.g. platinum, cerium oxide, etc. (Pang et al., 2019; Zhu et al., 2019; Zhang et al., 2015). However, the high preparation costs hinder the commercial application of catalytic ozonation of aniline.

Layered double hydroxides (LDH), also known as hydrotalcite, is a kind of synthetic clay-like materials (Sikander et al., 2017; Napruszewska et al., 2019; Lin et al., 2019). The special layered structure and the variability of metal ions in sheet endow great catalytic potential for contaminants removal (Fang et al., 2019; Olszówka et al., 2019). Cu-Co/Fe-LDH catalyst was considered as an effective heterogeneous catalyst for degradation of nitrobenzene based on hydroxyl radicals (Lu et al., 2019). Gong (Gong et al., 2017) reported heterogeneous activation of peroxymonosulfate by Fe/Co-LDH for efficient catalytic degradation of Rhoadmine B. After been calcined, the LDHs could be converted as Layered double oxides (LDO) which possessed higher catalytic activity (Teixeira et al., 2018; Zou et al., 2016). However, it is very rare to report on catalytic ozonation of aniline by Co/Fe-LDO (or Co/Al-LDO) manufactured from Co/Fe-LDH (or Co/Al-LDH) intermediates.

In this work, a new type of ozone catalyst-layered double oxides(LDO) catalyst was derived from layered double hydroxides intermediate(LDH) via co-precipitation -calcination methods from Co2+ and Fe3+(or Al3+) species, which realize the deep ozonation of aniline. Effect of preparation factors for Co/Fe-LDH and Co/Al-LDH intermediates (e.g. pH, co-precipitation temperature and composition ratio of Co:Fe or Co:Al) was investigated systematically. Morphology and mineralogy properties of the as-prepared ozone catalysts were evaluated. Degradation kinetics model of aniline in different catalytic systems were also established.

Section snippets

Agents

Ferric nitrate (Fe(NO3)3·9H2O), cobalt nitrate (Co(NO3)2·6H2O), aluminum nitrate (Al(NO3)3·9H2O), sodium hydroxide (NaOH), anhydrous sodium carbonate (Na2CO3), aniline (C6H7N), potassium iodide (KI), hydrochloric acid (HCl) and other agents used in the preparation process were all analytical pure and purchased from Shanghai McLean biochemical technology Co., LTD.

Aniline concentration in simulated aniline wastewater is 400 mg/L, and the initial pH of aniline wastewater is 8.0 ± 0.1 by using

Effect of preparation conditions on catalyst performance

Influence of multiple preparation conditions (e.g. pH, co-precipitation temperature and Co:Fe (or Co:Al) of mixed LDH intermediate solution) of LDH intermediates on catalyst performance and the thermal analysis(TG/DTG) of LDH intermediates were illustrated in Fig. 1. Simulated aniline wastewater with an aniline concentration of 400 mg/L was measured by CODCr, and the CODCr concentration of the simulated aniline wastewater was 960 mg/L. Catalytic performances of LDO catalysts prepared at

Conclusions

Co/Fe-LDO and Co/Al-LDO ozone catalysts were synthesized by ways of coprecipitation-calcination and they were used for the deep oxidation of aniline. The TG/DTG analysis revealed that the dehydration and recrystallization effect impelled LDH intermediate to form LDO catalyst. SEM and HRTEM images of the Co/Fe-LDO and Co/Al-LDO catalysts indicated that both catalysts have typical lamellar structure of layered double oxides and rough surface. XRD, HRTEM-mapping and XPS tests revealed that the Co

Declaration of competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This study was supported by National Science and Technology Major Project-Water pollution control and treatment (No. 2018ZX07208-009-06), the Open Fund project of Qingdao University of Technology (No. QUTSEME201924), Technology Development Project of Weifang City (No. 2019ZJ1300), and Zhejiang Heze Environmental Tech Shares Co., LTD Technological Foundation (No. B220170264). Furthermore, all the authors would like to thank Mr. Ding Zhinong, the CEO of Zhejiang Heze environmental Tech Shares

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