RESEARCH ARTICLE Methylene blue dye removal on silver nanoparticles reduced by Kyllinga brevifolia Norain Isa 1,2 & Zainovia Lockman 1 Received: 27 November 2018 /Accepted: 13 February 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Silver nanoparticles (AgNPs) were prepared by reacting Kyllinga brevifolia extract (KBE) with AgNO 3 aqueous solution at room temperature (22 ± 3 °C). The phytochemical constituents in KBE responsible for the reduction process were identified as carbohydrate, protein, and plant sterols (stigmasterol and campesterol). KBE was also found to function as a capping agent for stabilization of AgNPs. The AgNPs were stable at room temperature and had a quasi-spherical shape with an average particle size 22.3 nm. The use of KBE offers not only eco-friendly and non-pathogenic path for AgNPs formation, it also induced rapid formation of the AgNPs. Methylene blue (MB) removal was then done on the AgNPs in the presence of either KBE or NaBH 4 . Ninety-three percent removal of MB was achieved with a rate of reaction 0.2663 min -1 in the solution with KBE+AgNPs (pH 2). However, in NaBH 4 +AgNPs system, 100% MB removal was achieved at pH 8–10. The reaction rate was 2.5715 min -1 indicating a fast removal rate of MB dye. The process of reduction occurs via electron relay effect whereas in KBE+AgNPs system, sedimentation occurred along with the reduction process. Nevertheless, the use of KBE+AgNPs system is preferred as the reducing agent is more benign to the environment. Keywords Electron relay effect . Kyllinga brevifolia extract . Methylene blue dye . Silver nanoparticle . Sodium borohydride Introduction AgNPs have received increasingly scientific interest be- cause of their unique electronic, catalytic, and antibac- terial properties leading to applications as nanocatalyst, sensor, surface-enhanced spectroscopy, and active mate- rial in energy devices (Tran and Le 2013). Among all these applications, the use of AgNPs as nanocatalyst in the field of environment remediation is the most noteworthy. Catalytic performance of AgNPs is affected by their size (Celebioglu et al. 2014; Vidhu and Philip 2014a), oxidation state (Cuenya 2010), and interaction with their support (Yue et al. 2009). AgNPs can degrade harmful contaminants, for example, bacteria and fungi (Bindhu and Umadevi 2014; Zarpelon et al. 2016), heavy metal ions (Kumar et al. 2017), and pesticides (Li et al. 2014; Vasimalai and John 2013). AgNPs have also been used as catalyst for degradation of dyes; methylene blue (MB) (Bonigala et al. 2018; Nguyen et al. 2018; Suvith and Philip 2014), methyl orange (Francis et al. 2017; Vanaamudan et al. 2016; Vidhu and Philip 2014b), reactive red (Vanaamudan et al. 2016), 4-nitrophenol (Zhang et al. 2012), xanthene (Vanaamudan et al. 2016), malachite green oxalate (Devi and Ahmaruzzaman 2016), rhodamine B (Francis et al. 2017; Nguyen et al. 2018), and methyl red (Bonigala et al. 2018). In order to produce AgNPs, a bottom-up approach via the chemical reduction technique has been applied. Typical reduc- tants used for reducing Ag + ions to Ag 0 are ascorbic acid, sodium benzoate, ethylene glycol, polyvinylpyrrolidone, so- dium citrate, NaBH 4 , ethylene glycol, oleylamine, glucose, and ascorbate (Hong et al. 2016; Iravani et al. 2014; Tran Responsible editor: Philippe Garrigues * Norain Isa norainjsg@gmail.com Zainovia Lockman zainovia@usm.my 1 Green Electronics NanoMaterials Group (GEMs), School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Seri Ampangan, Nibong Tebal, Pulau Pinang, Malaysia 2 Sensor and Environmental Research Group (SERG), Department of Applied Sciences, Technology University MARA, Cawangan Pulau Pinang, Kampus Permatang Pauh, 13500, Permatang Pauh, Pulau Pinang, Malaysia Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-04583-7