A superhydrophobic nanocrystalline MOF embedded starch@cotton composite for fast, selective and nanomolar sensing and adsorptive removal of a fluorinated herbicide from aqueous medium

Abstract

The tackling of environmental pollution associated with the excessive use of harmful, non-biodegradable agrochemicals is one of the alarming concerns of modern-day environmental science researchers. Various herbicides belong to the frontline agrochemicals. Trifluralin is one of them. Although the use of herbicides can drastically increase the production of foodstuffs, the widespread use of these organo-toxins increases the concern for food safety and human health security. Hence, it is imperative to detect their presence and accurately measure their concentrations in food products. To overcome these challenges, herein, for the first time, we have constructed a reusable and environment friendly nanoscale Hf(IV)–organic framework (1) which can act as a selective sensor and promising adsorbent for one of the most widely used herbicide, trifluralin. In addition to rapid response time (<5 s) and ultralow detection limit (LOD = 16.3 nM) for trifluralin, this innovative framework material is capable of detecting and quantifying the targeted herbicide across a diverse range of environmental soil and water samples and multiple pH media. Moreover, the current MOF also serves as an exceptionally effective adsorbent for trifluralin from aqueous media. Its distinctive features include a remarkably short equilibrium time (<5 min), an unprecedentedly high adsorption capacity (164 mg g⁻¹) and the ability to adsorb trifluralin efficiently even in the presence of various other contaminants such as metal ions, anions, and other herbicides. This remarkable adsorption capability remains preserved in a wide range of environmental water sources and diverse pH levels. Furthermore, for the first time, MOF@starch@cotton composites have been fabricated utilizing the biopolymer starch as a binding agent. These composites have been successfully employed for both visual nanomolar-level determination and efficient adsorption of trifluralin. The most possible reason behind selective sensing and adsorption was deeply investigated with the help of appropriate analytical tools and theoretical simulations.