Processing of coal fly ash magnetic spheres for clay water flocculation

Abstract

The application of coal fly ash magnetic spheres (MSs) in water treatment is limited due to their complex mineral compositions, low magnetism, and large diameters. In this study, MSs were carefully ball milled and magnetically separated to improve their related properties. After the processing, the resultant magnetic ball-milled MSs (MBMSs) show a substantial change in composition, magnetism, and surface property in addition to a decrease in diameter. Compared with those of the original MSs, the Fe percentage, magnetism, and specific surface area of MBMSs are increased by 25.87%, 54.60%, and 810%, respectively. Dispersive spectrometer mapping investigation shows segregated high- and low-Fe areas with different structures in MS. These different structures enable purification. Highly turbid clay water flocculation experiments using MSs as flocculants indicate that MBMSs can cause fast flocculation whereas the compared samples exert less or slight flocculation effect. Zeta potential investigation suggests that the different flocculation effects are due to the change in the point of zero charge (pHPZC). The pHPZC increases from 3.91 for the original MS to 4.96 for MBMS. The reduction in the diameter, as well as the increase in magnetism, surface area, and pHPZC, makes MSs applicable to water treatment.