00000ctm a22000004i 4500 UP-99796217612829463 Buklod 20230215105418.0 m |o d | ta 180817s xx d r |||| u| (iLib)UPD-00366414354 DENGII rda eng DMLUC LG 995 2018 E68 V47 Verdijo, Michael Angelo O. author. Particle growth from the reduction of gold (III) chloride using sodium metabisulfite and ascorbic acid Michael Angelo O. Verdijo ; Herman D. Mendoza, thesis adviser. Quezon City College of Engineering, University of the Philippines Diliman 2018. xii, 70 leaves color illustrations 28 cm text rdacontent unmediated rdamedia volume rdacarrier Thesis (Master of Science in Metallurgical Engineering)--University of the Philippines Diliman May 2018. Available to the general public. The study aims to investigate the growth mechanism of precipitates formed from the reduction of gold (III) chloride complex to gold as a function of sodium metabisulfite (SMBS) and ascorbic acid (H2Asc) concentrations. A gold precursor was first prepared by dissolving 99.9% gold in aqua regia and diluted with 5% HCl to achieve a 100-ppm gold concentration. The precipitation study was conducted in two (2) stages: 1) varying concentration of SMBS (0.0002M, 0.0004M, 0.0006M, 0.0008M and 0.001M) at constant H2Asc concentration (0.1M); and, 2) varying concentration of H2Asc (0.02M, 0.04M, 0.06M, 0.08M, and 0.1M) at constant SMBS concentration (0.0001M). The addition of SMBS is the nucleating stage, and the addition of H2Asc involves the particle growth stage. Results showed that increasing H2Asc concentration increases the rate of formation. On the other hand, increasing the SMBS concentration beyond 0.0006M does not significantly increase the rate of formation, which indicates coalescences of the pre-formed nuclei and resulted in the decrease in the number of reduction sites. For the particle size analyses, increasing the SMBS concentration decreases the size of the particles due to the increase of number of reduction sites. Increasing H2Asc concentration also increases the particle size of gold precipitates. Two (2) values of Avrami constants were computed for each In[-In(1-x)] vs In(t) curve, n=3 which corresponds to a three (3)-dimensional growth, and n=1 which corresponds to a one (1)-dimensional growth of the particles. Therefore, the growth mechanism of gold formation involves two (2) stages, first is a spherical growth, followed by a second stage exhibited by the growth of spike-like particles. Gold Metallurgy. Chlorination. Mendoza, Herman D. adviser. Thesis FI UP UPD DENG-II LG 995 2018 E68 V47 Thesis