Fe₃O₄@C particles synthesized with iron‐containing water treatment residuals and its potential for methylene blue removal

Abstract

BACKGROUND Iron (Fe)‐containing groundwater treatment residual is a kind of waste from groundwater treatment plants, showing good potential to be reused. Attention has been paid to Fe‐based magnetic water treatment materials for their easy magnetic separation, and in the meantime, kinds of adsorbents were developed to address the severe global dyes pollution. RESULTS Black magnetic material was obtained with using the iron‐containing wastes as iron source without adding other iron chemical reagents by hydrothermal reaction. The X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared (FTIR) results show that the product is comprised of crystalline iron(II,III) oxide (Fe3O4) core and amorphous carbon shell (Fe3O4@C), and the core‐shell structure can also been seen clearly in transmission electron microscopy (TEM) images. Vibrating sample magnetometer (VSM) result shows its saturation magnetization is 33.56 emu/g. This sample's sorption experiments for methylene blue (MB) removal were conducted, and the experiment results indicated that this sample could be used in a wide range of pH (5–12) and the adsorption might be a complex chemical diffusion process consisting of boundary layer effect due to kinetic modeling fitting analysis. The maximum sorption amount of MB was 16.33 and 19.13 mg/g, respectively at 298 K and 308 K. This sample after five regeneration cycles still had 72.1% MB removal rate. CONCLUSION The Fe3O4@C particles with good magnetism were synthesized successfully with Fe‐containing water treatment residuals, water treatment waste sludge, via a one‐step hydrothermal reaction, which could be of reasonable analogy for treating other Fe‐containing industrial waste. Furthermore, this sample could be used as adsorbent for MB molecules removal from dyed water with good reusability and easy magnetic separation. © 2019 Society of Chemical Industry

Preparation and Characterization of Sludge-Based Magnetic Biochar by Pyrolysis for Methylene Blue Removal

“…The structure and phase purity of SMB were investigated by XRD ( Figure 2 a). As can be seen, the diffraction peaks marked with round shape in Figure 2 a are well indexed to (111), (220), (311), (400), and (440) planes of Fe 3 O 4 [ 34 ]. According to these strong and sharp diffraction peaks, it can be inferred that Fe 3 O 4 with good crystallinity had been prepared.…”

“…According to these strong and sharp diffraction peaks, it can be inferred that Fe 3 O 4 with good crystallinity had been prepared. In addition, biochar is one of the main components of SMB, but no specific diffraction peaks of carbon crystal structure were found, indicating that the carbon in SMB was amorphous carbon [ 34 ]. It is not negligible that there is a strong peak belonging to SiO 2 (square mark in Figure 2 a) and some slight peaks belonging to other substances in the XRD pattern.…”

“…In the last stage, the slope was the smallest and the intercept was the largest. At this stage, the adsorption site was gradually completely occupied by MB molecules, and the reaction reached the final equilibrium stage [ 34 ]. The adsorption of TC on magnetic biochar studied by Lin et al also went through a similar process [ 41 ].…”

“…In the regeneration experiment, SMB after adsorption was treated with 0.01 mol·L −1 , 0.05 mol·L −1 , 0.1 mol·L −1 , and 0.5 mol·L −1 hydrochloric acid respectively. The regeneration time was set at 9 h [ 34 ]. The regenerated product was washed several times, and the adsorption effect of the product on MB was detected respectively.…”

“…However, along the operation of the water plants, a large amount of iron mud would be produced, and the subsequent treatment of iron mud costs a lot [ 32 , 33 ]. This iron mud is cheap, easy to obtain, and contains no toxic substances [ 34 ]. This study creatively proposed to use the waterworks sludge of iron as the magnetic source, which does not contain the risk of heavy metal pollution, and provides a good method for the final disposal of waterworks sludge.…”