Enhancing Cr(vi) removal performance of TiCT through structural modification by using a spray freezing method.

Structural modification is expected to be a facile way to enhance the adsorption performance of MXene. In this work, the structural modification of TiCT was carried out by a spray freezing method, and two kinds of nano-structure (spherical and flaky) of TiCT were prepared by adjusting the solution concentration of TiCT . Then the Cr(vi) adsorption capacity and removal efficiency of the spherical and flaky TiCT was investigated, respectively. It is found that flaky TiCT was produced with a TiCT concentration of 3 mg mL, while spherical TiCT was obtained with a concentration of 6 mg mL. The long diameter of flaky TiCT is about 8-10 μm, and the specific surface area is 17.81 m g. While spherical TiCT had a diameter of about 1-4 μm and a specific surface area of 17.07 m g. The optimized structure of flaky and spherical TiCT improves the maximum adsorption capacity by 97% and 33%, respectively, compared with the few-layer TiCT . The maximum adsorption capacity of flaky TiCT was 928 mg g, while that of spherical TiCT was 626 mg g. The adsorption capacity of both TiCT structures decreased with the increase of pH, and reached the maximum value at pH = 2; meanwhile, the adsorption capacity of both TiCT structures increased with the increase of Cr(vi) concentration. The adsorption of Cr(vi) on flaky TiCT was very fast, reaching equilibrium in 3 min, while spherical TiCT took 5 min. The adsorption of Cr(vi) on both TiCT structures belonged to the monolayers, heat-absorbing chemical adsorption, and the diffusion process of Cr(vi) was regulated by the external diffusion and internal diffusion of particles. Its adsorption mechanism was the combination of reductive adsorption and electrostatic adsorption.