Adsorption of methylene blue using calcium oxide from chicken eggshell Woravarun Unkaew, Pinchaphat Poka, Weerawat Clowutimon and Pornsawan Assawasaengrat E3S Web Conf., 629 (2025) 04001 Published online: 05 June 2025 DOI: 10.1051/e3sconf/202562904001