Removal of Cu2+ from wastewater using eco-hydroxyapatite synthesized from marble sludge

Abstract

Rapid development brings environmental problems such as the discharge of industrial and agricultural wastewater. This study demonstrates the synthesis of eco–hydroxyapatite (eco–HAp) through the hydrothermal processing of marble sludge for the removal of Cu2+ from wastewater. FTIR analysis confirmed the existence of O–H and PO43− groups in eco–HAp samples. TEM analysis revealed the importance of Ca/P ratio on the shape and size of particles. Solid–state nuclear magnetic resonance (NMR) spectra revealed NMR 1H representing a single crystal site of (OH) and 31P representing the single crystal position of inorganic phosphorus (PO4). Eco–HAp samples presented Type IV N2 adsorption–desorption isotherms with H3 hysteresis loops, typical of HAp samples with a well–defined capillary step, which is indicative of mesoporous materials. Eco–HAp fabricated at a hydrothermal temperature of 120 °C and Ca/P molar ratio of 1 presented high adsorption capacity of 256.25 mg/g. The correlation between the eco–HAp and the Langmuir adsorption isotherm model was 0.96–0.99. Eco–HAp with a large surface area is thus an excellent adsorbent for the treatment of wastewater containing Cu2+.