Preparation method for lignosulfonic acid iron and manganese salt

The invention provides a preparation method for lignosulfonic acid iron and manganese salt. The method comprises the following steps: (a) mixing lignosulfonic acid, iron oxide, dilute sulfuric acid and oxidizing agent to obtain lignosulfonic acid iron salt solution; (b) adding oxide containing manganese into the lignosulfonic acid iron salt solution to carry out oxidative condensation; (c) dryingthe resultant solution to obtain lignosulfonic acid iron and manganese salt. According to the preparation method for lignosulfonic acid iron and manganese salt provided in the invention, lignosulfonic acid is taken as raw material, calcium ion content is reduced, filtration and calcium removal are avoided, material loss is reduced, and the operation of preparing displacement liquid is omitted. Compared with traditional preparation method, the method provided in the invention has simple operation and is labour-saving and time-saving.