Understanding and application of an electroplating sludge-derived catalyst with an active texture for improved NO reduction

https://doi.org/10.1016/j.scitotenv.2018.02.290Get rights and content

Highlights

  • Electroplating sludge and organic wastewater were used to synthesize catalyst.

  • The catalyst contained an active texture for effective NO reduction.

  • The texture contained multi-metal-oxide core and graphene oxide-like shell.

  • The core-shell interface was quite active for NO reduction.

  • The hybrid also showed good resistance to both SO2 and O2.

Abstract

Industrial sludge has been shown to be a valuable source of transition metals and to be effective in NO reduction. This research has further revealed a characteristic texture (O-Me-C) that promotes effective NO reduction and supports its existence in a sludge-derived catalyst. HRTEM exhibited that the O-Me-C consisted of multi-metal-oxide core, carbon shell and their binding interfaces. Furthermore, pre-treatment of the sludge with aromatic containing wastewater produced a more active texture (O-Me-GOL), characterized by the presence of multi-metal-oxide core, graphene oxide-like carbon and highly active interfaces (EELS, Mössbauer and Raman). As a result, the hybrid with O-Me-GOL exhibited enhanced activity and was able to remove >45% of NO (1000 ppm) at 200 °C and >99% at 400 °C over a much longer period (from 25 to 180 min) with an hourly gas space velocity of 14,400 h−1. Besides, the hybrid showed excellent resistance to both SO2 and O2. Therefore, the present work promoted the high value-added utilization of environment waste, and produced efficient catalyst in favor of sustainable development.

Introduction

Electroplating sludge is produced after the treatment of electroplating wastewater, which is rich in various transition metals, such as Ni, Cu, Zn, and Fe, and organics, such as surfactants and brighteners (Du et al., 2015). Every year, there was 100,000 ton of electroplating sludge produced in China (Li et al., 2010). These sludges are precious resource of transition metals. In our previous report, electroplating sludge was successfully recycled as a hybrid of mixed-metal oxides and carbon (J. Zhang et al., 2014b). Generally speaking, metal‑carbon hybrids were reported to be effective in nitric oxide (NO) reduction, and their performances were closely related to their structures and components.

Firstly, the structure of our catalyst was similar to multi metal-supported carbon (J. Zhang et al., 2014b), and its temperature (300 °C) for 100% reduction of NO was 200 °C lower than that of activated carbon-supported metal (Illan-Gomez et al., 1995). A compact mixture of carbon and metals resulted in better NO removal than a loose contact (Castegnaro et al., 2013; Wang et al., 2008), i.e. binding manner of carbon-metal interface determined the temperature for effective NO reduction. Secondly, the chemically-mixed carbon inherent in the catalyst was more available (80%) for NO reduction than physically-mixed carbon (30%) (J. Zhang et al., 2014b). Different carbon had the order of activity as: activated carbon > charcoal > real soot > synthetic soot (Nejar et al., 2007; Xue et al., 2008), indicating that carbon species also controlled activity. Thirdly, the catalyst contained various transition metals (Fe, Ni, Cu and Zn), and multi-metal catalysts were more active than single-metal one (Li et al., 2009; Nejar et al., 2005; Nejar and Illán-Gómez, 2007). Therefore, the sludge-derived material should have special textural components and interface required for efficient NO reduction.

The texture has been well established as resulting from the geometry of particle inter-stacking, and the textural pattern is determined by particle performance and the manner of binding (Yun and Pinnavaia, 1995). Previous works showed that carbon and metal were the basic textural units of carbon-supported-metal catalyst for NO reduction (Singoredjo et al., 1993; L. Zhang et al., 2014a). However, the questions of what an active texture is and what its functions are for effective NO reduction have not yet been satisfactorily answered. Increasing the amount of active textural component and interface area was expected to result in a long-term NO removal at low temperatures. Therefore, it was quite necessary to identify a simple and effective method to produce catalyst with an enhanced amount of ideal texture.

The carbon component in carbon-supported catalyst can be obtained by pyrolyzing biomass, graphite and other organic-containing materials. It was reported that the porous structure of sludge adsorbed organics from wastewater (Devi and Saroha, 2016; Huang et al., 2017). Thus, organic wastewater can mediate the organic content in sludge. Furthermore, the pyrolysis of transition metals (such as Fe) with organics can produce a textural interface between the metal and the carbon (Williams and Horne, 1994; Zhang et al., 1999). Taken together, these properties indicate that the texture for effective NO reduction can be potentially modified by pyrolysis after immersing the sludge in organic wastewater.

In this work, we modified texture of electroplating sludge with aromatic species in phenol wastewater by immersing and subsequent pyrolysis, and found that the obtained catalyst had an improved efficiency of NO reduction. Since this research was a primary investigation, no O2 was involved in most NO-reduction experiments. However, the catalyst still showed its potential to resist the effects of O2 and SO2 on NO reduction. Besides, the catalyst was made up of multi-metal-oxide (Me) core and graphene-oxide-like shell (GOL), which formed continuous texture of O-Me-GOL. This active texture was highly effective in oxygen and electron transfer during NO reduction.

Section snippets

Material preparations

The electroplating sludge was supplied by Shanghai Xinsheng Electroplating Co., Ltd., China. The phenol wastewater (COD = 5965 mg/L, pH = 8.7) was collected from Shanghai Baosteel Group. It mainly contained 610 mg/L of phenol and 350 mg/L of ammonia nitrogen. The dried sludge (ES, 6.0 g) was immersed in the phenol wastewater (600 mL) under vigorous stirring for 24 h, and then collected by filtration and dried at 105 °C. The obtained solid was denoted as ESc. Besides, Fe(OH)3 ((Fe)) was

Activity enhancement by pretreatment of phenol wastewater

Fig. 1A compares NO reduction by ES and ESc as a function of temperature. All hybrids showed similar temperature-dependent NO-reduction profiles. For example, the reduction increased from 4.0 to 92.8% as the temperature increased from 200 to 400 °C when ES was used. The temperature at which 50% of NO was removed (T50) was 320 °C for ES (Table 1). After modification with phenol wastewater, the activity was obviously enhanced, especially between 100 and 300 °C. Specifically, the performance of

Conclusions

The reveal of active textures for effective NO reduction suggested the following two valuable implications. Firstly, the texture theory indicated the reason why graphene oxide/graphene containing catalyst showed enhanced activity, since graphene structure facilitated electron transfers between catalyst and target molecule. Secondly, the identification of active texture suggested a novel strategy for the high-value-added utilization of waste, including transition metal waste (such as

Acknowledgments

This project was financially supported by National Nature Science Foundation of China, NO. 21707087, 21477071 and 91543123. Research grant from Science and Technology Commission of Shanghai Municipality, NO. 16DZX2260601. Program for Innovative Research Team in University No. IRT13078. We appreciate Instrumental Analysis & Research Center of Shanghai University for the help of sample characterizations.

References (56)

  • N. Nejar et al.

    Noble-free potassium-bimetallic catalysts supported on beta-zeolite for the simultaneous removal of NOx and soot from simulated diesel exhaust

    Catal. Today

    (2007)
  • N. Nejar et al.

    Bimetallic catalysts for the simultaneous removal of NOx and soot from diesel engine exhaust: a preliminary study using intrinsic catalysts

    Catal. Commun.

    (2005)
  • N. Nejar et al.

    Catalytic removal of NOx and soot from diesel exhaust: oxidation behaviour of carbon materials used as model soot

    Appl. Catal. B

    (2007)
  • M. Rajendran et al.

    Magnetic properties of nanocrystalline CoFe2O4 powders prepared at room temperature: variation with crystallite size

    J. Magn. Magn. Mater.

    (2001)
  • E. Sheremet et al.

    Nanoscale imaging and identification of a four-component carbon sample

    Carbon

    (2016)
  • L. Singoredjo et al.

    Modified activated carbons for the selective catalytic reduction of NO with NH3

    Carbon

    (1993)
  • Z. Struyk et al.

    Redox properties of standard humic acids

    Geoderma

    (2001)
  • H. Teng et al.

    Reduction of NO with NH3 over carbon catalysts: the effects of treating carbon with H2SO4 and HNO3

    Carbon

    (2001)
  • S. Verma et al.

    Structural, magnetic and Mössbauer spectral studies of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite powders

    J. Alloys Compd.

    (2011)
  • F. Wang et al.

    Enhanced phenol degradation in coking wastewater by immobilized laccase on magnetic mesoporous silica nanoparticles in a magnetically stabilized fluidized bed

    Bioresour. Technol.

    (2012)
  • P.T. Williams et al.

    The role of metal salts in the pyrolysis of biomass

    Renew. Energy

    (1994)
  • Y. Xue et al.

    Effect of pretreatment method of activated carbon on the catalytic reduction of NO by carbon over CuO

    Appl. Catal. B

    (2008)
  • A. Zhang et al.

    A novel method of varying the diameter of carbon nanotubes formed on an Fe-supported Y zeolite catalyst

    Microporous Mesoporous Mater.

    (1999)
  • X. Zhu et al.

    Advanced treatment of biologically pretreated coking wastewater by electrochemical oxidation using boron-doped diamond electrodes

    Water Res.

    (2009)
  • M.P. Araujo et al.

    Tuning the surface chemistry of graphene flakes: new strategies for selective oxidation

    RSC Adv.

    (2017)
  • M.V. Castegnaro et al.

    On the reactivity of carbon supported Pd nanoparticles during NO reduction: unraveling a metal-support redox interaction

    Langmuir

    (2013)
  • X. Chen et al.

    Macroscopic and spectroscopic investigations of the adsorption of nitroaromatic compounds on graphene oxide, reduced graphene oxide, and graphene nanosheets

    Environ. Sci. Technol.

    (2015)
  • C. Colliex et al.

    Electron-energy-loss-spectroscopy near-edge fine structures in the iron-oxygen system

    Phys. Rev. B

    (1991)
  • Cited by (20)

    • Treating waste with waste: Metals recovery from electroplating sludge using spent cathode carbon combustion dust and copper refining slag

      2022, Science of the Total Environment
      Citation Excerpt :

      The contents of Cu, Ni, and Cr in this sludge are 6.51 wt%, 7.27 wt% and 4.22 wt% respectively as presented in Table S1, while their phase compositions could not be identified by XRD analysis because of the poor crystalline structure as shown in Fig. S1(a). Previous studies have reported that Ni, Cu, and Cr mainly exist in the form of oxides (CuO, NiO, and Cr2O3) and hydroxides (Cu(OH)2, Ni(OH)2, and Cr(OH)3) (Chen et al., 2021; Hosseini et al., 2016; Zhang et al., 2018). Copper refining slag, which we used as an additive, was supplied by a copper smelter located in the Guangxi province of China.

    • Ball milling transformed electroplating sludges with different components to spinels for stable electrocatalytic ammonia production under ambient conditions

      2022, Chemosphere
      Citation Excerpt :

      Electrode plays an important role in NRR (Suryanto et al., 2018), and oxide is an effective NRR electrode. Coincidentally, electroplating sludge is easily transformed into oxides, including multi-metal oxide (Zhang et al., 2018a,b, Cui et al., 2018), perovskite (Bai et al., 2021), and spinel (Mao et al., 2018). In fact, electroplating sludge-derived electrodes have already been applied in capacitor (Hou et al., 2021), lithium storage (Lin et al., 2020), and reduction of CO2 (Yuan et al., 2016).

    • Calcined electroplating sludge as a novel bifunctional material for removing Ni(II)-citrate in electroplating wastewater

      2020, Journal of Cleaner Production
      Citation Excerpt :

      Electroplating sludge (ES) is produced via the alkaline precipitation of heavy metals in electroplating wastewater treatment plants, and it has to be treated as hazardous waste. The ES consists of a large quantity of metal hydroxides (e.g., Fe, Cu, Cr and Zn hydroxides) as well as organic matters (surfactants etc.) (Zhang et al., 2018). In recent years, ferrite inclusions have become more and more popular as a novel treatment to reuse electroplating sludge (Cao et al., 2017; Chen et al., 2017).

    • Regulating coordination state for production of effective denitrification catalyst

      2020, Journal of Cleaner Production
      Citation Excerpt :

      All these methods increased NO catalytic activities. What’s more, after a catalyst was modified by organic, the obtained material showed better activity, since the organic chelated catalytic center (Zhang et al., 2018). In order to further increase the coordination degree, a catalyst was obtained by pyrolyzing a chelated Fe-ligand precursor (Song et al., 2017), resulting a better activity.

    View all citing articles on Scopus
    View full text