▎ 摘　　要

NOVELTY - A composite catalyst comprises catalyst carrier and catalytic active component in mass ratio of 24:1-11.5:1. The carrier comprises modified diatomite having specific surface area of 325 m2/g, and graphene in a mass ratio of 2:1 or 3:1. The catalytic active component comprises 5 %mass main catalyst palladium and co-catalyst copper in a mass ratio of 3:1 or 4:1. The modified diatomite is obtained by modifying diatomite in 0.5 mol/L hydrochloric acid for 1 hour. The diatomite has round sieve shape and comprises amorphous silicon dioxide, aluminum oxide, magnesium oxide, ferric oxide, calcium oxide and sodium oxide. USE - Composite catalyst used for removing nitrate nitrogen in water (claimed). ADVANTAGE - The composite catalyst uses graphene and modified diatomite which have high chemical stability, excellent adsorption performance and large specific surface area. Under catalysis of catalyst, the nitrate in water reacts with reducing iron element (Fe0) to convert into nitrogen, and ensures effective denitrification. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of composite catalyst, which involves (S1) adding metal precursor palladium (II) chloride and copper (II) chloride dihydrate, dissolving oxygen in water to obtain mixed solution having volume slightly larger than that of carrier, (s2) placing the pretreated composite carrier and mixed solution in rotary evaporator, and evaporating until no water exists to obtain sample, (s3) adding sample into muffle furnace, calcining at 400℃ for 2 hours, introducing nitrogen into muffle furnace during calcinations, and wrapping crucible containing sample using tin foil paper, and (s4) naturally cooling sample to room temperature, adding excessive 1 mol/L sodium borohydride solution, stirring for 12 hours, repeatedly washing with deionized water, centrifugally dehydrating, drying in vacuum, and placing solution in dryer for drying at stirring intensity of 400 rpm.