Removal of COD in Wastewater By Magnetic Coagulant Prepared From Modified Fly Ash

Abstract In order to investigate the effective method of COD removal from desulfurization wastewater, acid-modified fly ash (AFA) and base-modified fly ash (BFA) were prepared by impregnation method. Then, magnetic coagulants (Fe-AFA, Fe-BFA) were prepared by mixing the modified fly ash with magnetic components. The structural characterization results showed that the specific surface area and the porosity of fly ash were obviously increased after modification. Fe-AFA magnetic coagulant has the best performance and superparamagnetism. Under the same experimental conditions, the maximum COD removal amounts of FA, BFA, AFA, Fe-BFA and Fe-AFA were 2.180, 3.209, 4.631, 3.710 and 5.687 mg/g, respectively. The COD removal amount of Fe-AFA was increased by 112.43% compared with the raw FA. The quasi-second-order kinetic and Langmuir equation could well fit the COD coagulation process of five coagulants. After five cycles, the COD removal amount of Fe-AFA was 2.735 mg/g, and the removal rate still reached 67.53%. These findings provide a feasible method for the treatment of fly ash from coal-fired power plants and the preparation of highly efficient COD trapping magnetic coagulants.