A method of reducing trace metal contaminants and/or reducing cerium oxide particles having a particle size of less than 10 nm in a cerium oxide slurry, the method comprising one or more of the following steps to: (a) adding an ion exchange resin to the cerium oxide slurry; and (b) removing the ion exchange resin from the cerium oxide slurry through filtration to obtain treated cerium oxide slurry; wherein the ion exchange resin is a cationic ion exchange resin selected from a cationic ion exchange resin having protons or potassium ions or an anionic ion exchange resin having a hydroxyl group; (a) adding a chemical additive to the cerium oxide slurry to form a mixture, wherein the chemical additive reacts with trace metal ions in the trace metal contaminants to form water soluble chemical additive-metal ion complexes in the mixture; (b) centrifuging the mixture; (c) collecting cerium oxide particles from the precipitate of the centrifugation; and (d) mixing deionized water with the collected cerium oxide particles to obtain a treated cerium oxide slurry; and adding a chemical chelator to the cerium oxide slurry to obtain treated cerium oxide slurry; wherein the chemical additive is selected from the group consisting of (a) organic acids selected from the group consisting of oxalic acid, citric acid, malic acid, tartaric acid, maleic acid, itaconic acid, gluconic acid, lactic acid, ETDA, and combinations thereof; (b) amino acids selected from the group consisting of glycine, alanine, serine, proline, and combinations thereof; (c) organic compounds containing at least one carboxylic acid group; (d) amino acid derivatives containing at least one amine acid moiety or iminodiacetic acid; (e) organic amine compounds selected from the group consisting of ethylene diamine, propylene diamine, ethylenimine, organic compound containing primary or secondary amino groups, and combinations thereof; (f) organic sulfuric acids containing at least one sulfuric acid group; (g) organic phosphoric acids containing at least one phosphoric acid group; (h) pyridine and its derivatives selected from the group consisting of pyridine, 2-methyl pyridine, substituted pyridine at position 2, 3, 4, 5 or 6 respectively, and combinations thereof; (i) bipyridine and its derivatives selected from the group consisting of 2,2'- bipyrine, 4,4'-dimethyl bipyridine, 4,4'-bipyridine, and all other substituted 2,2'-bipyrine or 4,4'-bipyridine derivatives, and combinations thereof; U)terpyridine and its derivatives; (k) quinoline and its derivatives; hydroxyl quinoline and its derivatives; (m) ammonium hydroxide; and combinations thereof; and the chemical chelator is hydroxyl quinoline or its derivative having a chemical structure selected from the group consisting of: and combinations thereof; wherein R is selected from the group consisting of hydrogen, alkyl, alkoxy, organic group with one or more hydroxyl groups, substituted organic sulfonic acid, substituted organic sulfonic acid salt, substituted organic carboxylic acid, substituted organic carboxylic acid salt, organic carboxylic ester, organic amine groups, and combinations thereof; and R' and R" can be the same or different, and are independently selected from the group consisting of hydrogen, alkyl, alkoxy, organic group with one or more hydroxyl groups, substituted organic sulfonic acid, substituted organic sulfonic acid salt, substituted organic carboxylic acid, substituted organic carboxylic acid salt, organic carboxylic ester, organic amine, and combinations thereof; wherein the chemical chelator reacts with trace metal ions in trace metal contaminants to form metal ion-chelator complexes. (a) adding an ion exchange resin to the cerium oxide slurry; and (b) removing the ion exchange resin from the cerium oxide slurry through filtration to obtain treated cerium oxide slurry; wherein the ion exchange resin is a cationic ion exchange resin selected from a cationic ion exchange resin having protons or potassium ions or an anionic ion exchange resin having a hydroxyl group; (a) adding a chemical additive to the cerium oxide slurry to form a mixture, wherein the chemical additive reacts with trace metal ions in the trace metal contaminants to form water soluble chemical additive-metal ion complexes in the mixture; (b) centrifuging the mixture; (c) collecting cerium oxide particles from the precipitate of the centrifugation; and (d) mixing deionized water with the collected cerium oxide particles to obtain a treated cerium oxide slurry; and adding a chemical chelator to the cerium oxide slurry to obtain treated cerium oxide slurry; wherein R is selected from the group consisting of hydrogen, alkyl, alkoxy, organic group with one or more hydroxyl groups, substituted organic sulfonic acid, substituted organic sulfonic acid salt, substituted organic carboxylic acid, substituted organic carboxylic acid salt, organic carboxylic ester, organic amine groups, and combinations thereof; and R' and R" can be the same or different, and are independently selected from the group consisting of hydrogen, alkyl, alkoxy, organic group with one or more hydroxyl groups, substituted organic sulfonic acid, substituted organic sulfonic acid salt, substituted organic carboxylic acid, substituted organic carboxylic acid salt, organic carboxylic ester, organic amine, and combinations thereof; wherein the chemical chelator reacts with trace metal ions in trace metal contaminants to form metal ion-chelator complexes.