Controlled Fabrication of K₂Ti₈O₁₇ Nanowires for Highly Efficient and Ultrafast Adsorption toward Methylene Blue

Advanced adsorbents need high adsorption rate and superior adsorption capability to clean up organic methylene blue (MB) from wastewater. We prepared K₂Ti₈O₁₇ nanowires grown along the [0 1 0] direction with a one-step hydrothermal method. The K₂Ti₈O₁₇ nanowires with tens of nanometers in diameter and tens of micrometers in length were achieved with smooth surfaces and twisted wire-like morphology. The K₂Ti₈O₁₇ nanowires exhibit high uptake capacity of ∼208.8 mg·g^-1 in the MB removal under equilibrium pH = 7. The adsorption equilibrium of MB onto the K₂Ti₈O₁₇ adsorbent is achieved with a 97% removal rate of MB within only ∼21 min, which is the shortest adsorption time among the recently reported inorganic adsorbents toward MB. The adsorption process has a good agreement with the well-known pseudo-second-order kinetic model (k₂ = 0.2) and the Langmuir isotherm model. Fourier transform infrared measurements suggest that the adsorption can be assigned to the hydrogen bonding and electrostatic attraction between MB and K₂Ti₈O₁₇. This ultrafast removal ability is due to the larger (0 2 0) interplanar spacing and zigzag surface structure of the nanowires, which provide abundant active adsorption sites. Thermodynamic parameters reflect the spontaneous, exothermic, and feasible uptake of MB. Besides, K₂Ti₈O₁₇ nanowires enjoy high adsorptive ability for chromium(VI) ions and photocatalytic removal toward NO. This work highlights the great significance of K₂Ti₈O₁₇ nanowires as a low-cost promising material used for the adsorptive elimination of organic contaminations in fast water purification on a large scale.