Optimization of Dimethyl Phthalate Degradation Parameters Using Zero-valent Iron Nanoparticles by Response Surface Methodology: Determination of Degradation Intermediate Products and Process Pathway

Background and Phthalic acid esters (PAEs) are a group of organic compounds that are used as additives in plastic industry. Among PAEs, dimethyl phthalate (DMP), the simplest compound in phthalates, is an aromatic pollutant that disturbs endocrine function. The aim of this study was to assess the effect of zero-valent iron nanoparticles (NZVI) on the DMP degradation.
NZVI were prepared by reduction of ferric chloride using sodium borohydride. Physical properties of nanoparticles were determined using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Vibrating Sample Magnetometer (VSM). Then, the effect of pH, DMP concentrations, the amount of NZVI, and contact time were investigated on DMP removal efficiency. Response surface methodology based on Box-Behnken was used to study the interaction between variables.
Maximum efficiency (99%) of DMP removal by NZVI was achieved in optimum conditions (pH=3, NZVI dosage =0.6 g/l, DMP concentration = 2 mg/l, and contact time= 65 min). The Box-Behnken analysis confirmed that pH and NZVI dosage have had the highest and lowest effect in the process of DMP removal by NZVI, respectively.
According to findings, NZVI in small amounts have a proper efficiency in DMP removal. Also, DMP degradation efficiency did not change much, after being used in five consecutive cycles of degradation reactions. This shows a potential application prospect of the synthesized NZVI in real water treatment.