R ESEARCH ARTICLE doi: 10.2306/scienceasia1513-1874.2024.053 ScienceAsia 50 (2): 2024: ID 2024053: 1–7 Optimization of adsorption process by aluminum dross for treatment of cutting oil wastewater Warangkana Srimoke a,b,c , Vorapot Kanokkantapong d,e,∗ , Nuta Supakata d,e , Wanida Limmun f a International Postgraduate Program in Hazardous Substance and Environmental Management, Graduate School, Chulalongkorn University, Bangkok 10330 Thailand b Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok 10330 Thailand c Department of Environmental Health, School of Public Health, Walailak University, Nakhon Si Thammarat 80160 Thailand d Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok 10330 Thailand e Waste Utilization and Ecological Risk Assessment Research Unit, Chulalongkorn University, Bangkok 10330 Thailand f Department of Mathematics and Statistics, School of Science, Walailak University, Nakhon Si Thammarat 80160 Thailand ∗ Corresponding author, e-mail: vorapot.ka@chula.ac.th Received 12 Feb 2023, Accepted 18 Apr 2024 Available online 25 May 2024 ABSTRACT: This research employed untreated aluminum dross obtained from auto parts manufacturing waste as an adsorbent to meet the sustainable goals of waste utilization in readily available, inexpensive, and environmentally friendly materials to treat cutting oil wastewater in auto parts manufacturing. Aluminum dross, categorized as white dross with 37.13% aluminum and 7.77% silicon, is a source of silicon- and aluminum-containing wastes. Process optimization was conducted using a central composite rotary design (CCRD) coupled with response surface methodology (RSM). The results indicated that the adsorption of aluminum dross at optimum conditions was 15 g adsorbed from 1% v/v cutting oil wastewater at pH 2 in 60 minutes, achieving the removal efficiency at 93.30% of chemical oxygen demand (COD), 88.33% of turbidity, and only 40.47% of total organic carbon (TOC). The second-order equation demonstrated coefficients of determination (R 2 ) and adjusted R 2 values of 0.9738 and 0.9345, respectively, for COD removal. The COD adsorbed on aluminum dross could be adequately explained using the pseudo -second- order kinetic and Langmuir models. Aluminum dross adsorption for cutting oil treatment has a low operating cost of 0.5398 USD/m 3 . KEYWORDS: chemical oxygen demand removal, wastewater treatment, waste utilization, response surface methodol- ogy INTRODUCTION A significant amount of waste, known as aluminum dross, is a by-product in the production of alu- minum [1]; one of which is the result of melting alu- minum when producing auto parts. Aluminum dross is categorized as hazardous waste, and its disposal in landfills is a worldwide problem [2], due to its negative impact on the ecosystem, surface water, and groundwater [3, 4]. In general, aluminum dross is mainly composed of Al 2 O 3 , AlN, Al 4 C 3 , SiO 2 , MgO, Al, and trace amount of Si. It is classified into three types: black dross, white dross, and salt cake. White dross contains 15%–70% recoverable metallic aluminum, black dross contains 12%–18% recoverable aluminum, and salt cake contains 3%–5% residual metallic aluminum [5]. In addition, aluminum dross is a waste product with practical applications in nu- merous devices and products, such as composite fillers, refractories, coagulants, deoxidizers in steel-making, and adsorbents [6, 7] During machining, oil wastewater is generated by cutting fluids, which improves efficiency by reducing power consumption, controlling rust, and extending the life of tools [8]. As most metalworking oils and fluids must be diluted before use, excessive cutting oil wastewater is produced [9, 10]. Metalworking fluids (MWFs) with high biochemical and chemical oxygen demands result from repeated use of cutting fluids con- taminated with trash, small chips, bacteria, and met- als [11]. Cutting oil wastewater can be treated via ad- sorption, which is a simple, eco-friendly, and econom- ical process; through this process desirable adsorbent properties, such as excellent adsorption capacity, low cost, and abundance, should be obtained [12]. Sev- eral materials have been developed as adsorbents for treating oily wastewater, including agricultural waste, such as corncob [13] and straw [11]; synthesized materials, such as superhydrophobic MS/TiO 2 /PDMS sponge [14] and modified sepiolite [15]; and waste materials, such as cement waste [16] and aluminum dross. Aluminum dross comprises SiO 2 - and Al 2 O 3 - based wastes that have been prepared for use as ad- sorbent materials [5]. Hence, it was used as adsorbent www.scienceasia.org