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Study on leaching kinetics of laterite ore using hydrochloric acid

Li Jinhui, Xu Zhifeng, Wang Ruixiang, Gao Yang, Yang Yang

Physicochemical Problems of Mineral Processing

2019

Vol. 55, iss. 3

711--720

The process of atmosphere-pressure acid leaching of laterites has attracted considerable attention in the nickel industry in recent years. However, the leaching kinetics of laterite using hydrochloride acid has not yet been fully researched. In this paper, the mineral analysis of the ore was carried out, and the leaching mechanism of different minerals at different time was studied comprehensively. The kinetics analysis of the leaching process of nickel, cobalt and manganese showed that the kinetics model of diffusion controlling was suitable and could be described by the linear equation, 1-3(1-a)2/3+2(1-a)=k2t. Based on the linear equation and the Arrhenius equation, the values of activation energy of metal leaching can be deduced (11.56 kJ/mol for nickel, 11.26 kJ/mol for cobalt and 10.77 kJ/mol for manganese). Study of leaching mechanism shows that the order of these minerals dissolution is: goethite, lizardite, magnetite and hematite. Due to the original or product of silica, magnetite, hematite and talc, they can form the solid film which hinders the leaching of valuable metals. Thus, the diffusion controlling step is inner diffusion, namely solid film diffusion controlling.

Isocoversional kinetic analysis of combustion and pyrolysis of municipal sewage sludge

Magdziarz A., Wilk M., Straka W.

Archivum Combustionis

2013

Vol. 33 nr 4

169--184

In this study, the thermal behaviours of sewage sludge were carried out by thermal analysis under air and argon atmospheres in the range from ambient temperature to 800 °C. The studied materials were characterized in terms of their chemical composition (C, N, H, S and trace elements) and calorific value. The important results focus on the temperature of maximum weight loss rate and the effect of atmosphere (air, argon) and heating rate (5, 10, 20 and 40 °C). TG and DTG curves were analysed. Non-isothermal kinetic analysis was used to evaluate the Arrhenius activation energy and the pre-exponential factor. The kinetic parameters were calculated using three isoconversional methods: Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa. The isoconversional methods were used to find dependency of the activation energy of studied processes on the conversion degree. The average values of activation energy for sewage sludge combustion e.g. S_A are Ea = 146.72; 151.87; 148.88 kJ/mol calculated by Friedman, FWO and KAS methods, respectively. For all studied sewage sludge samples the slight differences between the values of activation energies obtained by Friedman, FWO and KAS methods were obtained.