Pilomeena Arokiasamy, Mohd Mustafa Al Bakri Abdullah, Eva Arifi, Noorina Hidayu Jamil, Md Azree Othuman Mydin, Shayfull Zamree Abd Rahim, Andrei Victor Sandu, Shafiq Ishak
Biochar has great significance for controlling heavy metal pollution. Nevertheless, its application is impeded by certain shortcomings, such as a limited adsorption capacity, a slow adsorption rate, and poor reusability. Besides, the physical adsorption capacity of raw biochar to heavy metals is suboptimal. As a result, researchers prefer to use geopolymer-based adsorbents for the removal of heavy metals due to their excellent immobilization effect. However, no research has been done on the synthesis of geopolymer-based adsorbent using silica fume for heavy metal adsorption. Thus, the aim of this study is to partially replace metakaolin (MK) with silica fume (S1) (25, 50, 75 and 100 %) in geopolymer formulation at varied S:L ratio (0.4, 0.6, 0.8 and 1.0) to study the impact on the geopolymerization and its following properties in the removal efficiency of copper (Cu2 +). Characterization techniques such as Energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM) and Energy dispersive X-ray spectroscopy (EDX) were used to study the physicochemical properties of the developed geopolymer. The concentration of Cu2+ before and after adsorption was determined by Atomic absorption spectroscopy (AAS) and the removal efficiency was calculated. Based on the experimental result, the geopolymer prepared with 25 % MK and 75 % S1 at S:L of 0.6 maintained the high removal efficiency of Cu2+ (99.62 %) with 100 % MK geopolymer (98.56 %). The generation of N-A-S-H gel with the 75 % replacement level of S1 producing more reactive Si and Al binding sites for Cu2+ adsorption. In addition, S1 contains exchangeable cations such as Ca2+, Mg2+ and Na+ which further promote the adsorption of Cu2+ by ion exchange. Moreover, the mechanisms such as chemical bonding and precipitation were involved in the adsorption of Cu2+. Hence, this research could serve as a basis for the development of solid waste based geopolymers that could remove heavy metal ions from aqueous solution. © 2025 The Authors
Centre of Excellence Geopolymer & Green Technology (CEGeoGTech), Universiti Malaysia Perlis (UniMAP), Perlis, 01000, Malaysia; Faculty of Chemical Engineering & Technology, Universiti Malaysia Perlis (UniMAP), Perlis, 01000, Malaysia; Department of Civil Engineering, Universitas Brawijaya, Malang, 65145, Indonesia; Faculty of Mechanical Engineering & Technology, Universiti Malaysia Perlis (UniMAP), Perlis, 01000, Malaysia; School of Housing, Building and Planning, Universiti Sains Malaysia, Penang, 11800, Malaysia; Faculty of Material Science and Engineering, Gheorghe Asachi Technical University of Iasi, 41 D. 17 Mangeron St, Iasi, 700050, Romania; Faculty of Civil Engineering, University of Technology Malaysia (UTM), Johor, Johor Bahru, 81310, Malaysia
