Rapid purification of spent pickling liquor into ferrite by microwave hydrothermal method

Abstracts

Spinel ferrite was synthesized from two kinds of spent pickling liquor (SPL) by microwave hydrothermal method. X-ray diffraction (XRD) and toxicity characteristic leaching procedure (TCLP) showed that the synthesized product (V_SPLA:V_SPLB = 1:1) was well crystallized as well as had relatively high saturation magnetization (48.57 emu/g) and BET surface area (76.67 m²/g). Scanning electron microscope (SEM) and transmission electron microscope (TEM) revealed ferrite nanoparticles in size of around 20 nm. An adsorption experiment indicated that the obtained product was a kind of efficient and powerful magnetic adsorbent for the removal of methylene blue (MB) from aqueous solution. The effect of contact time, solution pH, and initial concentration was investigated. Adsorption kinetics data followed the pseudo-second-order model and adsorption isotherm data were fitted well to the Langmuir model with a maximum MB adsorption capacity of 33.07 mg g⁻¹. Furthermore, higher reaction temperature was beneficial for larger grain size and better crystallinity of the particle. The activation energy of ferrite process was 5.54 kJ/mol, which was much lower than that of other methods. Thus, microwave hydrothermal method was an environmentally friendly and economic process to realize two kinds of spent pickling liquor co-treatment.

Keywords:

• Spent pickling liquor
• Spinel ferrite
• Grain growth
• Adsorption

Acknowledgments

This study was carried out under the key subject of Shanghai Municipality (S30109), as well as been supported by National Nature Science Foundation of China Nos. 50704023, 50974086, and 51274138 Shanghai University Excellence Youth Fund. This study was also funded by China Scholarship Council.