New nano-biocatalyst for 4-chlorophenols removal from wastewater Maria Sarno a,b,⇑ , Mariagrazia Iuliano a a Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano (SA), Italy b Centre NANO_MATES, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano (SA), Italy article info Article history: Received 30 July 2019 Received in revised form 4 September 2019 Accepted 5 September 2019 Available online xxxx Keywords: 4-Chlorophenol removal Immobilized HRP Enzymatic degradation Graphene supported nanoparticles Reusability abstract In this paper, we report an eco-friendly approach for the removal of 4-chlorophenols from wastewater, through the use of horseradish peroxidase (HRP) immobilized on GO_Fe 3 O 4 /Au@CA nanoparticles. The effects of coupling time and enzyme concentration on the immobilization efficiency were investigated. The effects of reaction time and the reusability on the removal of 4-chlorophenols were also evaluated. In the first 30 min, the degradation process promoted by immobilized HRP was fast and increases up to 67%. The degradation of 4-CP in the presence of immobilized HRP was as high as 98% after 180 min. It is worth noticing that, after 180 min the TOC% removal was 85%. The immobilized HRP retains 95% of the initial activity for the first three cycles. These very high performances were promoted by gold, which con- tributes significantly to the excellent catalytic activity of our nano-catalyst. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Fabrication, Properties and Applications of Nano-Materials and Nano-Devices. 1. Introduction Aromatic compounds, such as phenol-based compounds, aro- matic amines, etc.., constitute one of the major classes of pollu- tants. Indeed, they are dangerous and persistent organic pollutants, highly toxic and with carcinogenic, teratogenic and mutagenic effects. They are found in the wastewaters of a wide variety of industries, including plastics, pharmaceuticals, wood preservatives, pesticides, petrochemicals, of printing, and dyeing materials [1]. Given the great number of industrial wastewaters containing chlorophenols, they are continuously monitored. Environmental legislation defines the maximum discharge limit in rivers as about 0.1 mg/L. On the other hand, the concentrations of chlorophenols found in the effluents may vary from 100 to 1000 mg/L, and their degradation is usually difficult [2]. Chlorophenols (CPs) can be mono-, di-, tri, tetra and penta-chlorinated phenols, with 19 possi- ble congeners. In particular, 4-chlorophenols are environmental pollutants which are widely produced as intermediates in the manufacture of insecticides, also found in tannery wastewater [3]. For these reasons, different techniques, such as physical adsorp- tion, catalytic oxidation, and biodegradation, have been used for chlorophenols removal. The enzymatic treatment has been pro- posed by many researchers as a potential alternative to conven- tional methods, to be applied as a secondary treatment to enhance the efficiency of biological units or as primary itself. Enzy- matic biodegradation presents high specificity, selectivity and cat- alytic activity, mild reaction conditions and few by-products formation [4]. Moreover, enzymes are less likely to be inhibited by substances which may be toxic for living organisms. Peroxidases (E.C. 1.11.1.7), such as horseradish peroxidase (HRP), lignin peroxidase (LiP), manganese peroxidase (MnP), etc... have been used for the treatment of aqueous aromatic compounds. In particular, HRP can degrade chlorophenols [5]. This enzyme cat- alyzed the oxidation of the phenol in presence of hydrogen perox- ide, to generate phenoxy radicals, which react with other substrate molecules to give oligomers or polymers that are much more insol- uble in water compared to the original monomers [4,6]. The reactions can be simply summarized in the following equation: 2RH þ H 2 O 2 ! 2R  þ 2H 2 O ð1Þ On the other hand, the use of HRP is limited due to poor stabil- ity and process costs. During phenol degradation, peroxidases can suffer from three know suicide pathways that must be minimized to improve the process economy [7]. These disadvantages can be overcome through the use of a highly active immobilized enzyme [8,9]. Enzyme immobilization can enhance the reusability and https://doi.org/10.1016/j.matpr.2019.09.016 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Fabrication, Properties and Applications of Nano-Materials and Nano-Devices. ⇑ Corresponding author at: Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II, 132 – 84084 Fisciano, SA, Italy. E-mail address: msarno@unisa.it (M. Sarno). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: M. Sarno and M. Iuliano, New nano-biocatalyst for 4-chlorophenols removal from wastewater, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.016