Facile Synthesis of Na₂Ti₆O₁₃ Nanorods by Ultrasonic Spray Pyrolysis Combined with Molten Salt Method and Their Radionuclide and Heavy Metal Sorption Capacity

One-dimensional (1D) sodium hexa-titanate (Na₂Ti₆O₁₃) nanorod has garnered considerable attention as a sorbent because of its intrinsic crystal structure and a large specific surface area. This unique characteristic enables it to irreversibly immobilize and entrap a great number of hazardous radionuclides and heavy metal cations and thus ensure permanently safe disposal. Although molten salt synthesis (MSS) has attracted much attention, it faces challenges in controlling the nanoscale, one-dimensional structure of Na₂Ti₆O₁₃ owing to large reactor size and long processing times, frequently leading to excessive overgrowth and reduced sorption efficacy. In this study, we propose a novel synthesis method—ultrasonic spray pyrolysis (USP) combined with molten salt synthesis (MSS)—designed for the cost-effective and scalable production of ultrafine Na₂Ti₆O₁₃ nanorods. This synthesis process yielded Na₂Ti₆O₁₃ nanorods with an average length of 246.15 nm and a diameter of 35.98 nm. The sorption and ion exchange capacities of Ba²⁺ were estimated to be 53.3 mg/g and 0.56 mmol/g, respectively, due to the ultrafine size of the particles and minimal aggregation. This study is expected to provide useful information for the cost-effective mass production of various alkaline titanate nanostructures with ultrafine size.