Application of Silica from Beach Sand in the Synthesis of Calcium-Alginate-Silica as Adsorbent of Na⁺ and Cl^- Ions

Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang (UM), Jl. Semarang 5, Malang, 65145, East Java, Indonesia

Abstract

The calcium-alginate-silica demonstrates the potential application of a membrane for clean water supply through the absorption of Cl^- and Na⁺ ions. Calcium originated from coral skeletons, while silica was extracted from the beach sands of The Gulf of Prigi. The produced membrane was characterized using XRF, FTIR, and SEM techniques, followed by NaCl solution adsorption studies. The results show that the coral skeletons as source of Ca consist mainly of calcium oxide based on XRF analysis, ranging from 90.86% to 93.41%. Similarly, Si in the beach sands primarily consist of SiO₂, ranging from 16.2% to 89.5%. FTIR analysis indicates the presence of functional groups (-OH, C=O, C-O, Si-O, and Si-OH) that facilitate the NaCl adsorption process. Additionally, SEM analysis was conducted using ImageJ, showing a particle size diameter of 16192.78 nm, which was characterized by a porous and relatively coarse structural morphology. The calcium-alginate-silica membrane showed the Na⁺ and Cl^- ion adsorptions of 55.4% and 49.4% at the optimal contact time of 20 and 40 minutes, respectively.