Photo-controllability of fluoride remediation by spiropyran-functionalized mesoporous silica powder

Spiropyran was successfully conjugated onto mesoporous silica surface, realizing conformational freedom of SP↔MC transformation and corresponding adsorption and desorption fluoride under photo-controllable manner. [Display omitted] •Spiropyran was successfully grafted on the surface of the mesoporous nano-silica.•SP moiety was conformational freedom due to SiO2 support providing large spaces.•Fluoride adsorption followed pseudo-first order and Freundlich, Langmuir models.•Fluoride could be desorbed, thus SP@SiO2 regenerated, by Vis-light irradiation. Fluoride contamination in water continues to be a great challenge to the sustainable development of global fluorine-containing industries. It is still a challenge to avoid the use of chemical desorbents induced secondary contamination in regenerating fluoride adsorbents. In this work, we aim to design a nanoadsorbent (SP@SiO2) specifically applicable for fluoride (F−) adsorption and desorption without using chemical desorbents, but via the approach of light-induction. The SP@SiO2 was fabricated by conjugating a rationally synthesised light-sensitive compound, spiropyran (SP), onto engineered mesoporous silica (SiO2) nanoparticles. Results showed that there was ∼0.14-0.15 mmol of SP conjugated onto per g of nanocomposite surface, forming a core-shell structure, which can realize conformational freedom of SP ↔ MC (merocyanine) transformation and corresponding adsorption and desorption fluoride under photo-controllable manner. Based on these, we intend to engineer a nanoadsorbent for F− remediation that may be potential guidance for those poisonous anions adsorption and light-induced desorption based on spiropyran-functionalized materials.