Treatment method of wastewater containing oxalic acid and method for preparing sodium battery positive electrode precursor by adopting oxalic acid method

The invention belongs to the technical field of sodium batteries, and relates to a method for treating wastewater containing oxalic acid and a method for preparing a sodium battery positive electrode precursor by adopting an oxalic acid method. The treatment method of the oxalic acid-containing wastewater comprises the following steps: carrying out nanofiltration treatment on the oxalic acid-containing wastewater, and adding water to an interception side in the nanofiltration treatment process, so that the purity of a sodium sulfate solution on the interception side reaches 90% or above, and a sodium hydrogen oxalate-containing solution is formed on a permeation side; the sodium hydrogen oxalate-containing solution is subjected to reverse osmosis treatment, and a high-concentration sodium hydrogen oxalate-containing solution with the concentration of 0.2-0.3 mol/L is obtained on the interception side; the method comprises the following steps: respectively introducing a high-concentration sodium hydrogen oxala