▎ 摘　　要

NOVELTY - The removal of calcium hardness ions in water involves ultrasonically dispersing oxidized graphene in de-ionized water, ultrasonically processing to disperse uniformly, adding L-cysteine, stirring, heating the mixed solution, immersing the reaction product in distilled water, and freeze-drying to obtain nitrogen-sulfur co-doped graphene aerogel material, mixing with polyvinyl alcohol solution to form paste-like dispersion liquid, removing dispersion liquid, and freeze-drying to obtain nitrogen-sulfur co-doped graphene aerogel paper electrode, and preparing calcium ion solution. USE - Removal of calcium hardness ions in water using nitrogen-sulfur modified graphene electrode (claimed). ADVANTAGE - The method enables removal of calcium hardness ions in water with high adsorption efficiency of calcium ion in water, by simple and environmentally-friendly process. DETAILED DESCRIPTION - The removal of calcium hardness ions in water involves (A) ultrasonically dispersing oxidized graphene in de-ionized water, ultrasonically processing for 10-30 minutes to disperse uniformly, adding L-cysteine, stirring to scatter evenly, heating the mixed solution in water bath at 95 degrees C for 2 hours, immersing the reaction product in the distilled water for 2-3 days, and freeze-drying to obtain nitrogen-sulfur co-doped graphene aerogel material, (B) mixing nitrogen-sulfur co-doped graphene aerogel material prepared in step (A) with polyvinyl alcohol solution to form paste-like dispersion liquid, removing 0.1-0.4 ml dispersion liquid uniformly coated on a hard paper, and freeze-drying to obtain nitrogen-sulfur co-doped graphene aerogel paper electrode, (C) preparing calcium ion solution, placing the calcium ion solution in an electric adsorption container, adsorbing calcium ion on the carbon nanotubes co-doped graphene aerogel paper electrode prepared in step (B), where the paper electrode is used as working electrode, the platinum electrode is used as electrode and the calomel electrode is used as reference electrode, using conductivity meter to monitor the change of solution conductivity, when the conductivity remains constant, where the absorption of the paper electrode reaches balance, and (D) removing the electrode voltage for adsorption of saturated nitrogen and sulfur co-doped graphene aerogel paper electrode, and recovering the electrical conductivity of the solution to the initial value.