Recent progress in advanced functional materials for adsorption and removal of cobalt from industrial and radioactive effluents

Water pollution jeopardizes environmental ecosystems and human health. The presence of cobalt ions (Co2+) and radionuclides (60Co) in industrial and radioactive effluents pose serious threats to environmental ecosystems and human health. Thus, removing Co2+ and 60Co from wastewater is essential for environmental and health reasons. Many techniques have been used to remove heavy metal ions and radionuclides from wastewater, such as adsorption, ion exchange, co-precipitation, chemical reduction, and ultrafiltration, have been reported to remove heavy metal ions and radionuclides from wastewater. However, adsorption is widely used and one of the most efficient techniques for treating heavy metal or radionuclide-contaminated wastewater because it is more straightforward to manage. Furthermore, several types of adsorbents have been used for this purpose. This paper comprehensively reviews and systematically provides an up-to-date summary of research and developments on various advanced functional materials as adsorbents, such as carbon-based materials, metal-organic frameworks, zeolites, clays, metal oxides, silica, sulfides, phosphates, layered double hydroxides, and biosorbents, that have been investigated for the efficient adsorption of Co2+ or 60Co polluted water. In this study, adsorbents are assessed in terms of their removal efficiencies, unique features, operating conditions (adsorbent dosage, initial Co2+ concentration, solution pH, contact time, and temperature), and mechanisms of Co2+ removal, and their pros and cons are compared. In addition, the key findings of previous studies are summarized. Finally, we propose research opportunities and challenges in the hope of stimulating more research on adsorbents for environmental pollution management. The design and development of adsorbent materials are of central importance to guarantee the harvesting of cobalt from industrial and radioactive effluents. Thus, we hope this review encourages further developments of advanced materials capable of recovering Co2+ or 60Co from secondary sources such as wastewater.