Synthesis of hydrochar supported zero-valent iron composites through hydrothermal carbonization of granatum and zero-valent iron: potential applications for Pb2+ removal.

Guangyin Jia,Jie Xu,Xiangchao Tang

doi:10.2166/wst.2021.366

Abstract

In the present investigation, a one-step synthesis of hydrochar (HC) supported zero-valent iron (ZVI) was performed through hydrothermal carbonization (HTC) of granatum and ZVI. According to XRD, XPS, and FTIR data, ZVI was evenly distributed on the surface of the hydrochar. In addition, the external ZVI oxide layer and the functional groups present in the hydrochar remained on the surface of the HC/ZVI composites after HTC treatment. The surface area of the HC/ZVI composites was between 31.11 and 44.16 m2/g. These numbers were higher than those obtained for hydrochar (20.36 m2/g) and ZVI (12.14 m2/g) separately. The Pb2+ adsorption capacity of hydrochar and ZVI was 28.64 and 192.44 mg/g, respectively (25 °C, pH = 6.05, Pb2+ concentration of 200 mg/L with 0.05 g HC and 0.01 g ZVI). In addition, the adsorption capacity of the composites was between 49.63 and 88.09 mg/g. The data obtained for Pb2+ removal by the samples used in this experiments fitted well the pseudo-second-order kinetics and Langmuir isotherm models. Therefore, hydrochar may represent a promising supporting material for the synthesis of ZVI composites.

Highlights

With rapid industrialization, large numbers of rivers and groundwater bodies have been polluted with heavy metals
In order to determine the potential use of HC/zero-valent iron (ZVI) composites as adsorbents for the removal of Pb2þ from wastewater, we investigated the characteristics of Pb2þ adsorption and the corresponding removal mechanisms
The peaks located at 711.9 eV and 725.4 eV corresponded to Fe 2p3/2 and Fe 2p1/2 of Fe3þ, and may be assigned to iron oxides like FeOOH and Fe2O3, respectively (Meng et al 2016). This is in good agreement with the results provided by the fourier transform infrared (FTIR) spectra and the core-shell structure of ZVI

Summary

Introduction

Large numbers of rivers and groundwater bodies have been polluted with heavy metals. Many methods including membrane filtration, ion exchange, redox reaction, precipitation, and adsorption have been developed for heavy metal elimination from industrial wastewater and contaminated groundwater. Among these methods, adsorption is widely used because of its convenience and high efficiency (Zhang et al 2021). Zero-valent iron (ZVI), especially nanoscale ZVI (nZVI), has been studied for its potential use in environmental remediation, including the removal of heavy metals from water (Li et al 2017; Yoshino et al 2018) This material presents abundant active sites, a strong reductive capability, and high surface area. It is important to develop new methods to optimize the synthesis of ZVI composites

Methods

Results

Conclusion