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

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.