Abstract
Paraquat is the most important herbicide of the bipyridyl group. The aim of the present study was to compare the removal of paraquat herbicide from aqueous solutions using nanoscale zero-valent iron-pumice/diatomite composites. In this study, nZVI was supported with diatomite and pumice. Scanning electron microscopy (SEM) analysis, X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectrometry (FTIR), and specific surface area tests (BET) were used to evaluate the properties of nanoadsorbents. The residual concentration of paraquat in aqueous solution was detected by high-performance liquid chromatography (HPLC). Then, the effects of different variables including the pollutant concentration, contact time, temperature, adsorbents (D-nZVI and P-nZVI) dose, and pH, were investigated in a lab scale batch system. The results showed that the optimal pH for both processes was 3.74. In optimal conditions, the efficiencies of D-nZVI and P-nZVI were 92.76% and 85.28%, respectively. In addition, isotherm and adsorption kinetics studies indicated that P-nZVI follows the Langmuir and Freundlich isotherm models, and D-nZVI follows the Langmuir isotherm model, and both processes follow pseudo-second-order kinetics. The results indicated that the synthesized nanoparticles were suitable for removing paraquat from aqueous solutions. Both adsorbents were found to be very effective in removing similar compounds at ambient temperature in a short time.
Highlights
In many countries, it is observed that the use of pesticides for agriculture causes problems such as water, soil, and air pollution [1]
It is known that the structure of this material is relatively dense and has fewer pores than the P-nZVI sample
About 40% of the visible particles in the D-nZVI sample have a size in the range of 80 to 100 nm and about 65% of the visible particles in the P-nZVI sample have a size in the range of 60 to 90 nm, which indicates a smaller particle size than the first sample
Summary
In many countries, it is observed that the use of pesticides for agriculture causes problems such as water, soil, and air pollution [1]. Eir excessive persistence can state serious risks to human health, aquatic life, and animals [2]. Paraquat is one of the most common herbicides, especially in developing countries. E use of this compound may present potential environmental hazards such as respiratory poisoning, hypersensitivity, gastrointestinal obstruction, neurological problems, pulmonary fibrosis, and Parkinson’s disease for humans and animals [4,5,6]. To protect human health and the environment from the harmful effects of paraquat herbicide, advanced and practical treatment processes are necessary to remove it from the water [8]. Common purification processes for removing paraquat generally include reductive processes such as adsorption on porous
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