A non-doped microporous titanosilicate for bimodal adsorption-photocatalysis based removal of organic water pollutants

Access to clean drinking water is limited for millions around the world and lead to dire health and economic ramifications, particularly in developing nations. This study explores a recyclable, low-cost, non-doped, microporous titanosilicate for effective removal of organic water pollutants. Rhodamine B was utilized as a modal pollutant to explore and optimize the activity of the titanosilicate, which evidently occurred via an adsorption and subsequent photocatalytic degradation based bimodal mechanism. The novel titanosilicate has high surface area (S-BET of 468 m(2)/g), is microporous (similar to 1.3 nm pore diameter), achieved via a surfactant templating technique. Its' physicochemical properties were characterised using FTIR, Raman, BET, SEM, PXRD and XPS. The photocatalytic activity of the material was studied under a solar simulator via time dependent UV-vis absorption measurements. The material showed 97% removal of Rhodamine B (5 mg/L) within 3 h, and outperformed nanosized titanium dioxide (anatase:rutile 4:1), the most conventionally used photocatalyst in tertiary water treatment. Interestingly, the titanosilicate displayed a dual mechanism of pollutant removal: an initial rapid removal of 59% due to adsorption during a 30 min equilibrating step in the dark, followed by near complete removal within 3 h. Additionally, a >90% efficiency of Rhodamine B removal by the titanosilicate catalyst was achieved consistently throughout 4 cycles, demonstrating its ability for regeneration and reusability. Such activity has not been previously reported in non-doped or non-composite titanosilicates, and opens up pathways to efficient, low-cost water treatment materials, consisting only of environmentally benign raw materials and synthetic procedures.