Removal of Cr(VI) from wastewater by M-HAFAC based on modified fly ash

ABSTRACT

Magnetic coagulants (M-HAFAC), using fly ash modified by hydrochloric acid, sulfuric acid, sodium hydroxide and ferric chloride as raw materials and nano Fe₃O₄ as magnetic seed, were prepared as an adsorbent for Cr(Ⅵ) in wastewater. Experiments and characterization analysis were performed on the prepared magnetic coagulant. The coagulation experimental results showed that the coagulant prepared on the basis of hydrochloric acid modified-fly ash (HAFAC) had the best adsorption properties, and the removal rate of Cr⁶⁺ could reach 97.53%. Zeta potential, BET, SEM, XRD, XPS characterization results showed that the mechanism of Cr(Ⅵ) removal by the modified fly ash-based magnetic coagulant was the synergistic effect of electro-neutralization and chemical precipitation. Kinetic and thermodynamic analyses showed that the adsorption behavior of Cr⁶⁺ adsorption by magnetic coagulants is dominated by monolayer adsorption and chemisorption, and the adsorption process heat absorption can proceed spontaneously.

KEYWORDS:

• Modified fly ash
• Fe₃O₄
• Magnetic coagulation
• Cr⁶⁺
• electrostatic charge neutralization

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Lemeng WANG: Methodology, Xu WANG: Experiment and Software, Wen WANG: Data curation and Writing- Original draft preparation, Fang ZENG: Investigation, Liqiang QI: Writing- Reviewing and Editing.

Statement of Novelty

Cr(VI) is considered to be one of the most carcinogenic and hazardous elements in wastewater. Removal of Cr(VI) from wastewater is beneficial for the environment.

The magnetic coagulant was synthesized by nano-Fe₃O₄ iron and modified-fly ash to remove Cr(VI) from wastewater.

This method is expected to contribute to the scale up of magnetic coagulation technology based modified-fly ash and recycling of waste.

Additional information

Funding

This work was supported by the Natural Science Foundation of Hebei Province [grant numbers B2019502067]; and the Fundamental Research Funds for the Central Universities [grant numbers 2020MS152].