<![CDATA[Batik wastewater contains synthetic dyes that may contaminate aquatic environments due to their intense coloration, complex molecular structures, and potential toxicity. Methylene blue (MB) and methyl orange (MO) are commonly used as model dyes to evaluate textile wastewater treatment performance because they differ in charge and molecular structure. This study aimed to synthesize nano-calcium oxide (n-CaO) from chicken eggshell waste and evaluate its adsorption performance toward MB and MO. Eggshells were washed, dried, ground, and sieved, followed by dissolution in 2N HCl, precipitation with 3N NaOH, neutralization, drying, and calcination to obtain n-CaO. Adsorption experiments were conducted using adsorbent dosages of 0.001, 0.003, 0.005, 0.007, and 0.009 g. The synthesized material was characterized by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), while dye removal was evaluated by UV-Vis spectrophotometry. The results showed that eggshell-derived n-CaO removed both dyes, with the highest removal efficiencies obtained at an adsorbent dosage of 0.005 g: 84.2% for MB and 39.5% for MO. Beyond this dosage, removal efficiency decreased, which may be associated with particle aggregation and reduced effective dispersion of adsorption sites. MB removal was consistently higher than MO removal, indicating different affinities of the two dyes toward the n-CaO surface. These findings demonstrate the potential of eggshell waste as a calcium precursor for producing CaO-based nano-adsorbents for dye-contaminated water, although validation using real batik wastewater and more complete adsorption analyses is still required. ]]>
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