Synthesis of Microporous Nano-Composite (Hollow Spheres) for Fast Detection and Removal of As(V) from Contaminated Water

Abstract A simple method has been designed for preparing a new material based on the interactions of cellulose acetate (mixed with an alkaline urea solution, CA/urea), cetyltrimethylammonium bromide (CTAB) with tetraethyl orthosilicate in alcohol (CTAB/TEOS). In a second step the material is loaded with molybdate. The nano-objects produced by this procedure are characterized as microporous hollow spheres with a morphology similar to hollow wagon-wheels. These materials were used not only for As(V) removal (specific affinity of As(V) for Mo(VI)), but also for naked-eye detection of As(V) in solution. The chemical and physical characteristics of these nano-objects have been analyzed through XRD, FTIR, HR-TEM, EDX, TGA/DTG and N2 sorption/desorption isotherms. The nano-sized sorbent/sensor has large surface-to-volume ratios (715.5 m2 g-1 and 0.295 cm3 g-1, respectively). Sorption capacity reaches 2 mmol As g-1 at optimum pH 1.8. Fast mass transfer properties allows reaching the equilibrium within 20-25 min (kinetics controlled by pseudo-first order rate equation). This structure allows ultra-fast, specific and pH-dependent visual detection of As(V): the limit of detection is evaluated to 0.3 µmol L-1 (limit of quantification: ≈1 µmol L-1). The nano-particles show remarkable long-term stability with good reproducibility after five regeneration cycles (loss in sorption and desorption efficiencies less than 5 %). The recovery of As(V) from dilute solutions reaches up to 93 %, when applied to water collected from Nile river.