Degradation of bis-p-nitrophenyl phosphate using zero-valent iron nanoparticles

Abstract

Abstract. Phosphate esters are employed in some agrochemical formulations and have long life time in the Environment. They are neurotoxic to mammals and it is very difficult to hydrolyze them. It is easy to find papers in the literature dealing with transition metal complexes used in the hydrolysis processes of organophosphorous compounds. However, there are few reports related with degradation of phosphate esters with inorganic nanoparticles. In this work bis-4-nitrophenyl phosphate (BNPP) was used as an agrochemical agent model. The BNPP interaction with zero-valent iron nanoparticles (ZVI NPs), in aqueous media, was searched. The concentration of BNPP was 1000 times higher than the ZVI NPs concentration. The average size of the used iron nanoparticles was 10.2 ± 3.2 nm. The BNPP degradation process was monitored by means of UV-visible method. Initially, the BNPP hydrolysis happens through the P-O bonds breaking-off under the action of the ZVI NPs. Subsequently, the nitro groups were reduced to amine groups. The overall process takes place in 10 minutes. The reaction products were identified employing standard substances in adequate concentrations. The iron by-products were isolated and characterized by X-RD. These iron derivatives were identified as magnetite (Fe 3 O 4 ) and/or maghemite (-Fe 2 O 3 ) and lepidocrocite (γ-FeOOH). A suggested BNPP degradation mechanism will be discussed. IntroductionHydrolysis of phosphoester bonds is involved in many biological processes. They have close relation to information store and conduction, energy transfer and protein phosphoacylation [1]. Phosphoesters have also been the most widely used as pesticides for many decades. They are a large source of potential hazard to humans [2,3]. These compounds are extremely stable and are highly resistant toward hydrolytic processes [4]. Bis-p-nitrophenyl phosphate (BNPP) is a phosphodiester compound that can be used as a model to study the hydrolysis of P-O bonds by catalytic interaction with metal nanoparticles. The stability of this molecule is relatively high; its t 1/2 is 2000 years in water at 20 °C and 53 years in water at 50 °C [5]. The hydrolytic cleavage of this molecule assisted by transition metal complexes is well-known [6][7][8][9]. However, there are few reports related with degradation of phosphate esters with inorganic nanoparticles.

Synthesis, Structures and Various Biological Applications of New Zn(II) Complexes Having Different Coordination Modes Controlled by the Drug Furosemide in Presence of Bioactive Nitrogen Based Ligands

“…Phosphate esters play different important roles in biological processes, such as information storage and utilization of (DNA/RNA), cellular signaling communication and energy transduction (ATP). In addition, phosphate esters have been used as pesticides for many decades …”

“…Bis(4‐nitrophenyl phosphate (BNPP) is a type of phosphodiester compound that can be used as an example to study the cleavage or the formation of P‐O bonds, but the hydrolysis of this compound and other types of phosphate esters is difficult and complicated due to the high stability of these compounds and high resistance to hydrolytic cleavage. The BNPP molecule has half life time (t 1/2 ) of 2000 years in water at 20 °C and 53 years in water at 50 °C …”