Nanocrystalline Cellulose-Derived Doped Carbonaceous Material for Rapid Mineralization of Nitrophenols under Visible Light

Abstract

Nitrophenols (NPs) and related derivatives are industrially important chemicals, used notably to synthesize pharmaceuticals, insecticides, herbicides, and pesticides. However, NPs and their metabolites are highly toxic and mutagenic. They pose a serious threat to human health and ecosystem. Current work was undertaken to develop a suitable visible-light active catalyst for the sustainable and efficient mineralization of NPs in an aqueous environment. Nanocrystalline cellulose (NCs)-based nitrogen-doped titanium dioxide and carbonaceous material (N-TiO 2 /C) was synthesized by pyrolysis and sol–gel methods using NCs, polydopamine, and TiO 2 . The synthesized N-TiO 2 /C was characterized using different analytical techniques. Photocatalytic degradation of NPs under visible light indicated that acidic pH (3) was most suitable for the optimal degradation. 4-NP degradation followed both pseudo-first-order ( R 2 = 0.9985) and Langmuir–Hinshelwood adsorption kinetic models (adsorption constant, K LH = 1.13 L mg –1 ). Gas chromatography–mass spectrometry and ion chromatography analysis confirmed the total mineralization of 4-NP into smaller molecular fragments such as acids, alcohols, and nitrates. The total organic carbon showed that 67% of total carbon present in 4-NP was mineralized into CO 2 and CO. The catalyst was recycled for five consecutive cycles without losing its catalytic activities. The degradation mechanism of NPs with N-TiO 2 /C was also explored.

Recent Developments in Synthesis and Photocatalytic Applications of Carbon Dots

“…Nitrogen-doped CDs (N-CDs) exhibit improved photocatalytic activity, as the nitrogen atom has a size that is similar to that of the carbon atom and effectively binds with the latter atoms via five valence electrons [52,53]. Among the photocatalytic applications of N-CDs, one should note those that are related to water treatment and the degradation of organic acids and synthetic dyes [54,55]. N-CDs that are produced via one-pot hydrothermal treatment of cellulose in urea solution [41] exhibit blue-green fluorescence and excitation-dependent emission with QYs of up to 21%.…”

Nitrogen-Doped Reduced Graphene Oxide Covalently Coupled with Graphitic Carbon Nitride/Sulfur-Doped Graphitic Carbon Nitride Heterojunction Nanocatalysts for Photoreduction and Degradation of 4-Nitrophenol

“…This diminishes the interaction of 4-NP with the active oxygen species produced on the catalyst surface, thus suppressing the overall degradation rate of 4-NP. 62 Furthermore, under alkaline conditions, H 2 O 2 dissociates to form HO 2 − . As the reactivity of HO 2 − with • OH radicals is very high, it results in the decrease of concentration of • OH radicals in the solution.…”

“…In alkaline pH (pH > 7), the surface of the catalyst attains a negative charge due to which it repels the phenolate ions formed after the dissociation of 4-NP. This diminishes the interaction of 4-NP with the active oxygen species produced on the catalyst surface, thus suppressing the overall degradation rate of 4-NP . Furthermore, under alkaline conditions, H 2 O 2 dissociates to form HO 2 – .…”

A study of TiO2 nanocrystal growth and environmental remediation capability of TiO2/CNC nanocomposites

“…Therefore, the use of TiO 2 /CNC nanocomposites can greatly reduce the energy consumption and potential hazards brought by the need for short-wavelength UV light. Table 1 illustrates the comparison of photocatalytic activities among varying TiO 2 /nanocellulose composite systems, [77][78][79][80][81][82][83][84] including TiO 2 /CNC in this work. It was found that the demonstrated TiO 2 /CNC nanocomposite possessed the smallest TiO 2 nanoparticles with high efficiency.…”