Efficient degradation of nonylphenol and 2,4-dinitrophenol by sunlight responsive hexacyanocobaltates nanostructures

Abstract

Nonylphenol (NP) and 2,4-dinitrophenol (2,4-DNP) are causing serious environmental concerns owing to their toxic, carcinogenic, persistentancy and bio-accumulating properties. It has been found that their concentrations are abundant near to industries and in many water bodies due to untreated release. Therefore, their complete removals using low-cost, efficient and environmental friendly techniques from water are required. Sunlight active metal hexacyanocobaltates nanoparticles have been reported beneficial heterogeneous and recoverable catalysts. Therefore, a green route based on utilization of natural material (Azadirachta indica leaf extract) and water was developed for the synthesis of cadmium hexacynocobaltate (CdHCC) and manganese hexacyanocobaltate (MnHCC) nanoparticles. Electron microscopic analysis revealed nanometer range (∼100 nm) for CdHCC and MnHCC particles. Synthesized nanomaterials were employed for the degradation of substituted phenols under direct Sunlight to follow the natural scenario. Maximum degradation of selected phenols (CdHCC- NP: 70 %; 2,4-DNP: 77 %, MnHCC- NP: 90 %; 2,4-DNP: 97 %) required 25 mg of catalyst per 50 mg L−1 of phenols at neutral pH under Sunlight irradiation. This excellent photocatalytic activity of the MnHCC might be due to high surface activity (surface areas of CdHCC and MnHCC were 95 m2 g-1 and 448 m2 g-1, respectively) and particles stability (as observed from zeta potential, CdHCF: -13.5 mV; MnHCF: -19.2 mV). The degradations followed first-order kinetics. Adsorption plots were best fitted with Langmuir isotherm. GC–MS analysis of the final reaction mixtures showed the formation of low molecular weight and safer compounds, which were finally mineralized. Degradation mechanism of NP and 2,4-DNP involved OH radicals based oxidation, hydroxylation, and ring-opening. These materials were found reusable up to ten times revealing sustainability. Overall, these Sunlight responsive novel metal hexacyanocobaltate nanomaterials might be promising and sustainable materials for remediation of environmental contaminants.