200,000+ products from a single source!
sales@angenechem.com
Home > A stable and easily prepared copper oxide catalyst for degradation of organic pollutants by peroxymonosulfate activation
A stable and easily prepared copper oxide catalyst for degradation of organic pollutants by peroxymonosulfate activation
Songxue Wanga,b,1, Shanshan Gaoa,1, Jiayu Tiana,*, Qiao Wangc, Tianyu Wangb, Xiujuan Haob, Fuyi Cuid,*
School of Civil Engineering and Transportation, Hebei University of Technology, Tianjin, 300401, China
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, China
School of Civil and Transportation Engineering, Guangdong University of Technology, Guangzhou, 510006, China
College of Urban Construction and Environmental Engineering, Chongqing University, Chongqing, 400044, China
1. Introduction
With the economic development, rapid population growth and urbanization, frequent occurrences of organic pollutants including pharmaceuticals, pesticides and personal care products in surface water environment have raised concerns over their potential impacts on the aquatic lives even the human health (Adoamnei et al., 2018; Oulton et al., 2015). However, effective removal of some organic pollutants can be hardly achieved by conventional physical-chemical water treatment technologies because of their stable chemical structure (Wang et al., 2018a; Feng et al., 2016). During the past years, advanced oxidative processes (AOPs) has emerged as a promising strategy for the oxidation of organic contaminants, which based on highly reactive oxygen species (ROS) (Zhao et al., 2019; Wang et al., 2019). Peroxymonosulfate (PMS) has attracted increasing research interests as an alternative to hydrogen peroxide (H2O2) and peroxydisulfate (PDS) due to its asymmetric structure that can be more readily activated by various catalysts. Fur- thermore, PMS activation has many other advantages including su- perior oxidation ability, mild reaction conditions, and avoidance of secondary contamination (Zhu et al., 2017; Shao et al., 2017), which are recently considered to be an excellent candidate for degradation of refractory organic contaminates.
Metal ions has been recognized as an efficient homogeneous catalyst for PMS activation for organic pollutants degradation (Anipsitakis and Dionysiou, 2004). Although, some metal ions such as Co2+ Ru3+ and Fe2+ exhibit high catalytic activities, their applications in water treatment are quite limited because of the toxicity of these ions and difficult to recycle (Xu et al., 2018). Therefore, employment of het- erogeneous catalysts for PMS activation is a promising option (Kong et al., 2019; Shao et al., 2018). Copper oxide (CuO) is one of the most prominent catalysts and a powerful candidate to activate PMS due to its low-cost, availability and low toxicity compared with other transition metal oxides (Zhang et al., 2014a; Ghanbari and Jaafarzadeh, 2017; Hu et al., 2017; Chen et al., 2008). Ji et al. synthesized a well-crystallized CuO for PMS activation to degrade phenol in aqueous solution. The results indicated that the prepared CuO can effectively catalyze the decomposition of PMS into SO4%− and %OH, and thus exhibited good performance for phenol degradation (Ji et al., 2011). In their study, the SO4%− and %OH was assumed to directly generate from the reaction that ^Cu(Ⅱ) is firstly reduced to ^Cu(Ⅰ) by HSO5–, which is thermo- dynamically unfavorable (Zhang et al., 2013). Recently, more and more publications proposed novel mechanisms about the reaction between persulfate and metal oxides which is different from traditional SO4%– and %OH based oxidation processes. For example, Zhang et al. reported that CuO could effectively activate PS to degrade 2,4-dichlorophenol (2,4-DCP), which relied on the outer-sphere interaction between PDS and CuO instead of producing SO4%− (Zhang et al., 2014b). Zhu et al. reported that the 1O2 was elucidated as the main ROS for degradation of aqueous contaminants in the PDS/β-MnO2 system (Zhu et al., 2019). Li et al. proposed that PMS was first bound to the Fe(III)-N moieties to generate ^FeV]O, which reacted effectively with 4-CP via electron transfer (Li et al., 2018). In the study by Peng et al., CuO-Fe3O4 na- nocatalyst could efficiently activate PMS via a multipath process in- cluding radical and non-radical pathway to produce SO4%-, %OH and 1O2 (Peng et al., 2018). Therefore, the reaction mechanism of PMS activa- tion deserves further research in different systems.
In addition, many CuO or copper-based catalysts with high catalytic activity reported in previous studies were prepared using hydrothermal method (Oh et al., 2015; Lei et al., 2015; Wang et al., 2018b). As well known, the catalytic performance of nanocrystals is strongly related to crystallographic structure, orientations, dimensions and nanostructures (Zhou et al., 2011). With the hydrothermal techniques, the final di- mension, morphology, and characteristics of the nanocatalysts are de- termined by many critical synthesis parameters such as reactant con- centration, pH, growth temperature and growth time (Ansari et al., 2014). In order to obtain the catalyst with excellent performance, the complicated experimental parameters must be strictly controlled and any parameter changes may lead to the reduction of catalytic perfor- mance of catalyst, which makes it difficult to prepare stably. Moreover, high temperature, high pressure and long reaction time are also the significant disadvantages of hydrothermal method, because of the in- crease in preparation costs at large scale production (Wang et al., 2016). Consequently, it is still highly desirable to develop novel and efficient synthetic procedures for high performance catalysts.
Herein, a direct one-step calcination preparation of CuO catalyst in the presence of polyethylene glycol (PEG) as nonionic polymeric structure directing agent was designed in this work. As we know, PEG is usually used as a structure directing reagent for the formation of CuO nanostructures in the hydrothermal method (Zhang et al., 2014a; Karunakaran et al., 2013). Combined with calcination, it can not only obtain the CuO particle with specific morphology and structure, but also simplifies the procedures to achieve stable preparation. The crys- talline structure, morphology and physicochemical properties of the prepared CuO were systematically characterized. The catalytic perfor- mance of the CuO catalyst prepared via the novel route for PMS acti- vation was evaluated in terms of removal of organic pollutants in water. The interaction mechanism for the PMS/CuO-involved degradation of water pollutants was investigated by performing experiments using different quenching agents and electron paramagnetic resonance (EPR) technique. The results indicated that the non-radical pathway was mainly responsible for the removal of organic pollutants in the system, which possesses the great potential in the field of water decontamination.
2.Material and methods
2.1.Chemicals
Copper oxide (CuO), polyethylene glycol (PEG, MW = 4000), copper nitrate trihydrate (Cu(NO3)2·3H2O), hydrochloric acid (HCl), sodium hydroxide (NaOH), methanol (MeOH) and butyl alcohol (TBA) were obtained from Sinopharm Chemical Reagent Co., Ltd. Potassium peroxymonosulfate (PMS, KHSO5·0.5KSHSO4·0.5K2SO4), 5,5-dimethyl- 1-pyrolin-Noxide (DMPO) and 2,2,6,6-tetramethyl-4-piperidinol (TEMP) were purchased from Sigma-Aldrich Co., Ltd. Bisphenol A (BPA), phenol, 4-chloride (4-CP), nitrobenzene (NB), benzoic acid (BA), furfuryl alcohol (FFA) and benzoquinone (BQ) were obtained from Aladdin Chemistry Co., Ltd. Deionized (DI) water was used throughout the experiments.
2.2.Catalyst preparation
Firstly, two kinds of copper oxides without participation of PEG were prepared for comparison. The first kind of CuO particle was pre- pared with direct calcination of Cu(NO3)2·3H2O under 450 °C for 2 h in air, denoted as CuO-1. The second kind of CuO particle was prepared by calcining the dried aqueous solution of Cu(NO3)2. In detail, 5 g Cu (NO3)2·3H2O was dissolved in 25 mL DI water then the solution was evaporated and dried at 60 ℃. Afterward, the precursor was calcined at 450 °C for 2 h in air to obtain the CuO particles, denoted as CuO-2. For the third kind of CuO particle, 0.5 g of PEG was first dissolved to 25 mL DI water under 70 ℃. Afterwards, 5 g of Cu(NO3)2·3H2O was dissolved to this solution to obtain a homogeneous blue solution. Finally, the solution was oven-dried at 60 °C and calcined at 450 °C for 2 h in air. The obtained CuO particle was denoted as CuO-3. All the heating rates of the three preparation processes are 2 °C/min.
2.3.Characterization
The crystal structures of the CuO particles were analyzed by X-ray diffractometry (XRD) (Bruker D8, Germany) with Cu-Kα radiation source (λ =0.15418 nm) at 40 kV and 30 mA over the 2θ scanning range of 10°–80°. The functional groups were characterized by Fourier transform infrared spectroscopy (FTIR, Bruker Tensor 27, Germany). Morphologies and crystal structures were analyzed with Field-emission scanning electron microscopy (FE-SEM, SIGMA500, Zeiss, Germany), transmission electron microscopy (TEM, JEM-1400, JEOL, Japan) and high-resolution transmission electron microscopy (HR-TEM, JEOL2100, Japan). Specific surface area was analyzed by Brunauer-Emmett-Teller (BET, Beckman Coulter SA 3100, U.S.A.) and Barrett-Joyner-Halenda (BJH) models based on nitrogen adsorption-desorption experiment. The chemical states of different elements in samples were detected by X-ray photoelectron spectroscopy (XPS, ESCALAB 250Xi, U.S.A.) with Al Kα X-ray (hν = 1486.6 eV) radiation and the binding energies were cali- brated by reference to the C 1s peak at 284.6 eV.
2.4.Catalytic degradation of contaminants
The catalytic degradation experiments were conducted in a 100 mL beaker at 25 °C water bath with magnetic stirring. The initial pH of solution was controlled with 1.0 M NaOH or H2SO4 solution. In a ty- pical reaction, 0.01 g of catalyst was added into 100 mL of organic pollutant solution (5 mg/L) to establish an adsorption-desorption equilibrium (15 min), and then predetermined amounts of PMS was added into the solution to initiate the reaction. At each time interval, 1 mL of reaction solution was withdrawn and immediately filtered through 0.22 μm filters, then quenched with excess pure methanol (0.5 mL). The concentrations of organic pollutants were detected by an ultrahigh performance liquid chromatography (UHPLC) equipped with a C18 column and a UV absorbance detector. The detailed conditions are listed in Table S1. PMS decomposition rate was determined using the colorimetric method (Zhang et al., 2014b) and the details was provided in Text S1. The metal ions leaching concentration was mea- sured by inductively coupled plasma optical emission spectrometry (ICP-OES, Perkin Elmer 7300, U.S.A.). The generated reactive species were measured using Electron paramagnetic resonance (EPR, Bruker A300 spectrometer, Germany) with DMPO and TEMP as the spin trapping agents. The measurement at the center of the field was 3355 G. The microwave frequency was 9.8 GHz and the microwave power was 19.5 mW.
Over 100,000 products now available from Angene:
© 2019 Angene International Limited. All rights Reserved.