Dithizone-Modified Magnetic Core-Shell of Fe3O4@SiO2 Derived from Beach Iron Sand and Volcanic Ash and Its Application as Cu(II) Adsorbent

Beach sand and volcanic ash contain large amounts of magnetite and metal oxides, making it suitable as adsorbent base materials for pollutant removal. In this study, the preparation and modification of a core-shell Fe 3 O 4 @SiO 2 with dithizone for Cu(II) adsorption was investigated. The study included synthesis of magnetite (Fe 3 O 4 ) from iron beach sand, silica (SiO 2 ) from volcanic ash, magnetic core-shell Fe 3 O 4 @SiO 2 (CS) and dithizone immobilization on the surface Fe 3 O 4 @SiO 2 (CS-DTZ) to enhance its adsorption selectivity and capacity towards potentially toxic elements. The successful synthesis of CS and CS-DTZ was confirmed by XRF, FT-IR, XRD, SEM, TEM, and VSM. The optimum adsorption of Cu(II) using CS and CS-DTZ were found at pH 4 with adsorbent dosage of 1.75 and 1.5 g L -1 , respectively, a contact time of 90 min, and a Cu(II) initial concentration of 60 mg L -1 . The Cu(II) adsorption using two adsorbents followed pseudo-second-order kinetic and Langmuir isotherm models with adsorption capacity (q m ) of 27.78 and 34.36 mg g -1 , respectively. Sequential desorption revealed that the adsorption mechanism involves electrostatic interactions, hydrogen bond, and complexation. This new developed adsorbent is promising because it can be prepared from naturally abundant sources and easily separated using external magnet after application. • Core-shell material of Fe 3 O 4 @SiO 2 was successfully synthesized from beach iron sand and volcanic ash. • Dithizone-modified Fe 3 O 4 @SiO 2 was prepared in eco-friendly alkaline aqueous medium. • Dithizone functionalization of core shell significantly enhanced the Cu(II) adsorption capacity. • Cu(II) adsorption followed pseudo-second-order kinetic and Langmuir isotherm models, indicating a chemisorption. • The magnetic core shell was easily separable using an external magnet and potential for wastewater treatments.