Contents lists available at ScienceDirect Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe Synthesis and characterization of graphene shell composite from oil palm frond juice for the treatment of dye-containing wastewater Yeit Haan Teow a,b, *, Siti ‘Aisyah Tajudin b , Kah Chun Ho a,b , Abdul Wahab Mohammad a,b a Research Centre for Sustainable Process Technology (CESPRO), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia b Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia ARTICLE INFO Keywords: Oil palm frond Graphene shell composite Adsorption Sustainable practice Methylene blue ABSTRACT The discharges of dye-containing wastewater have predominantly been attributed to the textile industry, where methylene blue (MB) is the most commonly-used dye. The use of graphene-based adsorbents with sugar as the natural carbon source has been reported as a new milestone; however, the sustainability of entailing sugar in such engineering practices is questionable. Considering the generation of agricultural waste from palm oil mills in the context of Malaysia and the need of more sustainable carbon sources for the synthesis of graphene-based adsorbents, this study explored the synthesis of graphene shell composite (GSC), a new generation of graphene- based adsorbents, with oil palm frond (OPF) juice as the natural carbon source and with oil palm kernel shell as the base material. The synthesized GSC was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The adsorption performance was evaluated by studying the effect of synthetic MB solution concentration and the GSC mass. 75.45%–99.13% removal of MB ions from synthetic MB solution after 20 h of adsorption performance study suggested the applicability and effectiveness of the synthesized GSC in treating dye-containing wastewater. Further kinetics analysis revealed that the interactions between GSC and MB ions fitted the Freundlich isotherm (R 2 = 0.9631-0.9689) and pseudo-second order isotherm (R 2 = 0.9860-0.9980). Such findings reflect that the uptake of MB ions by GSC was mechanistically a multilayer adsorption, in which the MB ions approached the active sites on GSC surfaces and were continually adsorbed thereon through che- mical bonding. 1. Introduction Dyes are organic compounds used to impart colouration to materials such as textiles, papers, and leather. The production of dye-containing wastewater has predominantly been attributed to textile manu- facturing: during the dyeing process in producing colored fabric, the dye dissolved in water is imparted to the fabric whereas the remaining dye-containing water is discharged into various water bodies as was- tewater [1,2]. One of the common dyes in the textile industry is me- thylene blue (MB) due to its deep-blue appearance [3,4]. The presence of MB in water bodies has been known to be hazardous. The dark-co- lored MB restricts the direct penetration of light into the water body, hence prohibiting the growth of aquatic life [5,6]. Additionally, the exposure of humans to MB may cause vomiting, chest pain, hard breathing, and fast heartbeat [7]. Given such complications, it is im- perative to treat MB wastewater before its discharge into the water bodies. The treatment of wastewater can be categorized into three groups: biological treatment, chemical treatment, and physical treatment [8]. Biological treatment involving the use of microorganisms is the most economical. However, the method is time-consuming, given the in- evitably long retention time for microbial degradation. Moreover, its efficiency is lacking due to the complex molecular structure of MB [9,10]. As for chemical treatment, coagulation is widely used for was- tewater treatment [11]. Although its relative effectiveness and shorter operation time, chemical treatment suffers from drawbacks such as the need for costly chemicals and difficulty in handling the resultant sludge [12]. Lastly, physical treatment is the most feasible, effective, and simplest wastewater-treatment method [13,14]. Adsorption, a physical- treatment method with the use of activated carbon (AC), has been ap- plied for decades in wastewater treatment. Efforts have been under- taken to replace AC with a more sustainable adsorbent, such as one https://doi.org/10.1016/j.jwpe.2020.101185 Received 19 December 2019; Received in revised form 2 February 2020; Accepted 11 February 2020 ⁎ Corresponding author at: Research Centre for Sustainable Process Technology (CESPRO), Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. E-mail address: yh_teow@ukm.edu.my (Y.H. Teow). Journal of Water Process Engineering 35 (2020) 101185 2214-7144/ © 2020 Elsevier Ltd. All rights reserved. T