Advantages of bimetallic nitric oxide reduction catalysts consisting of heavy metals rich in hazardous wastes Yirui Wang a , Jinyang Li b , Jia Zhang b, c, * , Jingyi Zhang b , Dong Zhai c , Guangren Qian b, ** , Yi Liu c, d , Chuncheng Zuo a a School of Mechanical and Aerospace Engineering, Jilin University, Changchun, 130022, PR China b SHU Center of Green Urban Mining & Industry Ecology, School of Environmental and Chemical Engineering, Shanghai University, 381 Nanchen Road, Shanghai, 200444, PR China c Materials Genome Institute, Shanghai University, 333 Nanchen Road, Shanghai, 200444, PR China d Department of Physics and International Centre for Quantum and Molecular Structures, Shanghai University, 99 Shangda Road, Shanghai, 200444, PR China article info Article history: Received 19 April 2019 Received in revised form 8 July 2019 Accepted 29 July 2019 Available online 29 July 2019 Handling Editor: Panos Seferlis Keywords: Waste minimisation Heavy metal waste Bimetallic catalyst Nitric oxide Density functional theory abstract High-value-added recycling of hazardous waste is a key problem in environmental science and engi- neering. In previous reports, a hazardous-waste-derived catalyst showed better activity than a catalyst synthesised from pure reagents for the reduction of nitric oxide. The multimetallic nature of hazardous waste was speculated to increase the catalytic activity. In this work, a further investigation was con- ducted to confirm this speculation. It was found that bimetallic catalysts showed better activity than monometallic ones at 50e200  C. A bimetallic catalyst removed 75.05% of nitric oxide (990 ppm) at 150  C, whereas monometallic ones removed only 19.50%. Moreover, the bimetallic catalyst removed 11.46 mmol/g of nitric oxide after 1200 min at 300  C, which was a much higher concentration than that removed by the monometallic catalyst (2.72 mmol/g). Experimental and simulated Raman spectroscopy revealed that enhanced activity was accompanied by a larger blue shift of the metal band (indicating catalytic centre activity) and a smaller blue shift of the carbon band (indicating reductant stability). In a theoretical calculation, a second metal changed the electron density difference of the catalytic centre and activated the distant reductant, increasing both the low-temperature activity and activity stability. The main result of this study explained the reason bimetallic catalysts outperformed the monometallic ones. Because hazardous waste usually contains bimetallic species, it can be used as a suitable resource for producing effective catalysts. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction More than 50 million tons of hazardous waste is produced every year in China. Hazardous waste usually contains large amounts of heavy metals and toxic organics. Thus, although general solid waste (such as sewage sludge) can be treated by various technologies, including membrane bioreaction and anaerobic and aerobic digestion (Kelessidis and Stasinakis, 2012; Sepehri and Sarrafzadeh, 2018), these methods are not applicable to treatment of hazardous waste, which must be disposed of in a safe landfill directly or after incineration to protect humans and the environment (Yilmaz et al., 2017). Unfortunately, disposal by landfill occupies land and potentially allows leaching out of toxic materials. Therefore, high-value-added recycling of hazardous waste has become an urgent topic. To realise zero discharge, many attempts have been made to produce a functional material from hazardous waste, for example, by metal extraction (Wang et al., 2015b). Moreover, two types of hazardous waste (slag and elec- troplating sludge) were successfully used to synthesise effective catalysts for selective catalytic reduction of nitric oxide (Wang et al., 2018; Zhang et al., 2018a). * Corresponding author. SHU Center of Green Urban Mining & Industry Ecology, School of Environmental and Chemical Engineering, Shanghai University, 381 Nanchen Road, Shanghai, 200444, PR China. ** Corresponding author. E-mail addresses: 496670643@qq.com (Y. Wang), 1774940969@qq.com (J. Li), irujam@t.shu.edu.cn (J. Zhang), 595769313@qq.com (J. Zhang), zhaidongplus@ gmail.com (D. Zhai), grqian@shu.edu.cn (G. Qian), yiliu@t.shu.edu.cn (Y. Liu), zuocc@jlu.edu.cn (C. Zuo). Contents lists available at ScienceDirect Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro https://doi.org/10.1016/j.jclepro.2019.117834 0959-6526/© 2019 Elsevier Ltd. All rights reserved. Journal of Cleaner Production 237 (2019) 117834