Co3O4 anchored on sepiolite surface grooves for superior adsorption of tetracycline from wastewater

Abstract

Due to the low valence band maximum value, Co3O4 is an outstanding catalyst, but its utilization in adsorption needs to be addressed. In this study, we proposed a novel method for loading aggregation-prone Co3O4 onto sepiolite (Sep) to facilitate tetracycline (TC) adsorption. The XRD, TEM, and FTIR analyses demonstrated that the highly dispersed Co3O4 was successfully anchored on the sepiolite grooves via the Si-OH on the sepiolite surface’s grooves to the cobalt site in Co3O4. We firstly proposed a view of how metal oxide aggregates are confined to the grooves on the surface of sepiolite (via Si-OH at the edges of the grooves on the sepiolite surface). The ultra-high sorption capacity of Co3O4-Sep is 219.53 mg/g for TC, which is three times that of Sep (70.75 mg/g) and Co3O4 (85.29 mg/g). The kinetic and isotherm results fitting suggested that the adsorption of TC on Co3O4-Sep mainly contributed to the multilayer chemisorption adsorption process. Thermodynamic investigations revealed the spontaneous endothermic reaction of TC adsorption on Co3O4-Sep. Co3O4 strengthened the complexation between the composite and functional groups of TC, significantly increasing TC adsorption capacity. In addition, the Co3O4-Sep retained an extraordinary adsorption capacity with the presence of competing ions, at strongly acidic and alkaline pH values and after three cycles. Therefore, this study offers new perspectives on applying cobalt-based materials and demonstrates the potential for antibiotic adsorption in the prepared composites.