International Journal of Technology (2018) 2: 307-316 ISSN 2086-9614 © IJTech 2018 SYNTHESIS OF ZnO NANOPARTICLES AND THEIR NANOFLUID STABILITY IN THE PRESENCE OF A PALM OIL-BASED PRIMARY ALKYL SULPHATE SURFACTANT FOR DETERGENT APPLICATION Muhammad Triyogo Adiwibowo 1 , Muhammad Ibadurrohman 1 , Slamet 1* 1 Department of Chemical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia (Received: December 2017 / Revised: January 2018 / Accepted: February 2018) ABSTRACT ZnO nanoparticles were successfully synthesized by a solochemical method using zinc chloride as the precursor in a sodium hydroxide solution with ZnCl2:NaOH ratios of 1:2 and 1:3. The effects of the thermal treatment on the functionalities of the nanoparticles were investigated by comparing calcined ZnO with uncalcined ZnO. Calcined ZnO underwent a drying process at 120°C, followed by calcination at 500°C, while uncalcined ZnO underwent the drying process only. The synthesized nanoparticles were characterized by XRD and FESEM-EDX analysis. The photoactivity of synthesized ZnO was evaluated through methylene blue degradation. In addition, ZnO nanofluids were synthesized by dispersing nanoparticles into the base fluid. The nanofluidic stability in the presence of a Palm Oil-Based Primary Alkyl Sulphate (palmPAS) surfactant were investigated using a spectrophotometer UV-vis with varied PalmPAS concentrations. XRD and FESEM analysis showed that the nanoparticles exhibited a hexagonal wurtzite structure, and confirmed that the particle size increased on calcination. All the synthesized ZnO nanoparticles exhibited good photoactivity under UV light irradiation due, to some extent, to their good crystallinity. The calcined ZnO from the ZnCl 2:NaOH ratio of 1:3 offered the best photocatalytic performance compared to its ZnO counterparts. It was also found that the nanofluids of uncalcined ZnO from the ZnCl2:NaOH ratio of 1:3, at a ZnO:palmPAS ratio of 1:9, offered the best stability. Keywords: Detergent; Nanofluid stability; PalmPAS surfactant; Solochemical method; ZnO 1. INTRODUCTION Conventional detergents are generally derived from fossil-based petroleum and are difficult to decompose, causing major problems to the environment. Bio-based surfactants are expected to be able to serve as substitutes for petroleum-based ones. Many advantages can be claimed for the use of bio-based surfactants, including biodegradability, low toxicity, and compatibility with people and the environment (Sekhon, 2013). In terms of detergency, the ability of surfactants/detergents can be improved by introducing additives, such as semiconducting photocatalysts. A series of metal oxides such as TiO2, MgO, and ZnO have been developed for the degradation of organic pollutants in the presence of light illumination (Guo et al., 2011). Another study has used a doped metal oxide such as C-N-titania (Slamet et al., 2017). In fact, its composites, such as CNTs-titania have also been utilized for such applications (Wibowo et al., 2015). *Corresponding author’s email: slamet@che.ui.ac.id, Tel: +62-21-7863516, Fax: +62-21-7863515 Permalink/DOI: https://doi.org/10.14716/ijtech.v9i2.1065