The Influence of Pluronic F-127 Modification on Nano Zero-Valent Iron (NZVI): Sedimentation and Reactivity with 2,4-Dichlorophenol in Water Using Response Surface Methodology

Yajun Li,Qi Jing,Yongxiang Zhang,Yuhui Lin

doi:10.3390/catal10040412

Abstract

Nano zero-valent iron (NZVI) is widely used for reducing chlorinated organic pollutants in water. However, the stability of the particles will affect the removal rate of the contaminant. In order to enhance the stability of nano zero-valent iron (NZVI), the particles were modified with F-127 as an environmentally friendly organic stabilizer. The study investigated the effect of the F-127 mass ratio on the colloidal stability of NZVI. Results show that the sedimentation behavior of F-NZVI varied at different mass ratios. A biphasic model was used to describe the two time-dependent settling processes (rapid sedimentation followed by slower settling), and the settling rates were calculated. The surface morphology of the synthesized F-NZVI was observed with a scanning electron microscope (SEM), and the functional groups of the samples were analyzed with Fourier Transform Infrared Spectroscopy (FTIR). Results show that the F-127 was successfully coated on the surface of the NZVI, and that significantly improved the stability of NZVI. Finally, in order to optimize the removal rate of 2,4-dichlorophenol (2,4-DCP) by F-NZVI, three variables were tested: the initial concentration 2,4-DCP, the pH, and the F-NZVI dosage. These were evaluated with a Box-Behnken Design (BBD) of response surface methodology (RSM). The experiments were designed by Design Expert software, and the regression model of fitting quadratic model was established. The following optimum removal conditions were determined: pH = 5, 3.5 g·L−1 F-NZVI for 22.5 mg·L−1 of 2,4-DCP.

Highlights

Chlorophenols (CPs) are widely used in wood preservatives, pesticides, lubricants, dyestuffs, and the synthesis of other chemicals [1,2,3]
The spherical form of F-nano zero-valent iron (NZVI) suggests that numerous reactive sites could be provided with a chain-like structure, due to the magnetic interactions between the F-NZVI particles, which could be maintained in a stable state [30]
F-127 was developed to modify the NZVI, and it was found that F-127 significantly increased the stability of NZVI

Summary

Introduction

Chlorophenols (CPs) are widely used in wood preservatives, pesticides, lubricants, dyestuffs, and the synthesis of other chemicals [1,2,3]. 2,4-dichlorophenol (2,4-DCP), as a long-lived pollutant, is one of the representative phenolic compounds and a key intermediate in the synthesis of chloride-based herbicides. CPs have raised great concern in the protection of human health, due to their high toxicity and long persistence in the environment [4,5]. It has been listed as a priority pollutant by the U.S Environmental Protection Agency (EPA) (2003) [6,7]. The NZVI is applied for the removal of various pollutants in water, Catalysts 2020, 10, 412; doi:10.3390/catal10040412 www.mdpi.com/journal/catalysts

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