# Efficient removal of Cs+ and Sr2+ from water using titanate nanotubes embedded in alginate macromolecules

## TL;DR

Researchers developed a new material using titanate nanotubes in an alginate matrix to efficiently remove radioactive cesium and strontium from water.

## Contribution

A novel composite material combining titanate nanotubes and alginate was created for rapid and reusable radionuclide removal.

## Key findings

- Titanate nanotubes achieved 90% Cs⁺ and 97% Sr²⁺ removal within 15–30 minutes.
- The T/G composite showed 45–70% Cs⁺ and 70–90% Sr²⁺ removal with good reusability.
- Adsorption mechanisms included electrostatic attraction, surface complexation, and ion exchange.

## Abstract

The presence of long-lived radionuclides such as Cs⁺ and Sr²⁺ in aquatic systems poses serious environmental and health risks, necessitating the development of highly efficient and practically applicable sorbents. Although various materials have been explored for radionuclide removal, most continue to suffer from slow kinetics, limited selectivity, and difficult recovery. In this study, titanate nanotubes (TNTs) were synthesized hydrothermally and further incorporated into a biodegradable alginate matrix (T/G composite) via ionic gelation to improve handling and solid–liquid separability. The physicochemical features of TNTs and T/G before and after adsorption were examined using XRD, FTIR, FESEM-EDX, zeta potential and N2 adsorption/desorption isotherm analyses to better elucidate structural behavior and adsorption mechanisms. Batch experiments evaluated the effects of pH, dosage, initial ion concentration, and contact time. TNTs exhibited rapid adsorption, reaching equilibrium within 15–30 min, with removal efficiencies of 90% for Cs⁺ and 97% for Sr²⁺ at pH 8 and 0.075 g dose. Isotherm fitting using eleven nonlinear models, supported by comprehensive error analysis revealed that both Cs⁺ and Sr²⁺ adsorption followed both Sips and Langmuir–Freundlich models, reflecting heterogeneous and multilayer adsorption behavior. Kinetic results indicated that chemisorption dominated the process, as suggested by the agreement of experimental data with PFO, PSO, MFSO, and Avrami models. The error analysis revealed that the initial concentration of Cs⁺ and Sr²⁺ play a significant role in the adsorption kinetics. The T/G beads achieved removal efficiencies 45–70% Cs⁺ and 70–90% Sr²⁺. Although embedding TNTs in alginate reduced adsorption capacity due to the lower active TNT ratio, it offers excellent mechanical stability and ease of separation. The adsorption mechanism combines electrostatic attraction, surface complexation, and partial ion exchange between Cs⁺/Sr²⁺ and Na⁺ in titanate layers. Regeneration studies demonstrated that TNTs retained over 90% of their initial performance after five cycles, while T/G maintained above 85%, confirming the materials’ reusability. The rapid kinetics, high capacity, and simple regeneration procedure highlight the potential scalability of TNT-based systems for radionuclide removal. However, practical deployment may still require optimization of TNT loading within the alginate matrix and evaluation under real wastewater conditions.

The online version contains supplementary material available at 10.1038/s41598-026-38030-8.