Filter aid for decomposing phosphorite acidolysis solution with nitric acid and filtering method

The invention relates to the field of filter aids, in particular to a filter aid for decomposing phosphorite acidolysis liquid with nitric acid and a filtering method. The filter aid is a magnetic carbon filter aid, and a preparation method of the magnetic carbon filter aid comprises the following steps: fully mixing the coal gasification coarse slag with an electrolyte solution containing calcium ions, and then adding the mixture into a ball mill for grinding; then transferring into a tubular reaction furnace; then soaking the reaction product in an alginic acid and amino acid iron solution, carrying out ultrasonic oscillation, and centrifuging to obtain a solid product; and putting the solid product into the tubular reaction furnace for treatment. Adding humic acid into the acidolysis solution during filtering, stirring, standing, settling, and carrying out primary filter pressing to obtain primary filter residues and primary filtrate; adding a magnetic carbon filter aid into the primary filtrate, stirring,