Abstract
M.Tech. (Extraction Metallurgy)
Various activities of mining, mineral processing and extraction releases arsenic into the environment. The reported presence of high concentration of arsenic in lakes surrounding a selected silver, cobalt and copper mines has gained serious attention of the scientific community. This research encompasses the characterization of a low-grade copper oxide ore using atomic absorption spectrometer, x-ray fluorescence (XRF), x-ray diffractometer (XRD), SEM-EDS and Induced Coupled Plasma Mass Spectroscopy (ICP-MS). Leaching and adsorption of the copper ore sample was carried out using sulphuric acid of varying molarity -3M, 2M, 1.5M, 1M and 0.5M – and two Lanthanum and Cerium nanoparticles adsorbents were prepared for the adsorption of arsenic from the ore sample during the hydrometallurgical extraction of copper -leaching- process. This study revealed that there is a direct relationship between the concentration of acid and arsenic dissolution. The %As adsorption on Lanthanum nanoparticles adsorbent is lower at higher acid molarity and higher at lower sulphuric acid molarity. While in the case of Cerium adsorbent, there is a deviation. The Cerium ions were able to actively react with arsenic at higher acid molarity hence causing higher adsorption at higher molarity of acid than lower molar mass. Arsenate removal efficiency increases sharply with increasing adsorbent dosage, though there were some anomalies which were observed to be because of competing ions on the adsorption. The increase in temperature was found to reduce the adsorption efficiency of both the Cerium and Lanthanum nanoparticles adsorbents. The effect of acid molarity, adsorbent dosage and temperature were also studied on copper and iron dissolution in the extraction process. Low copper dissolution rate was achieved due to the activation of active binding sites by the Cerium and Lanthanum adsorbents which might have attracted some copper ions. The copper dissolution rate obtained when Cerium impregnated adsorbent was used gave better copper recovery than when Lanthanum adsorbents were applied. The values of RL obtained for each of the adsorption carried out shows that the nature of Langmuir model is unfavourable for Lanthanum nanoparticles, but the linear value obtained for RL in the case of Cerium nanoparticles makes it fit into the model. It is important to note that Cerium nanoparticles adsorbent performs better with increasing acid molarity while Lanthanum nanoparticles adsorbent performs better with increasing adsorbent dosage. Considering the findings obtained from studying different parameters such as acid molarity, temperature and adsorbent dosage, it can be concluded that Cerium nano adsorbent is a better adsorbent than Lanthanum nano adsorbent.