Agromining of hyperaccumulator biomass: Study of leaching kinetics of extraction of nickel, magnesium, potassium, phosphorus, iron, and manganese from Alyssum murale ashes by sulfuric acid

In the present study, a thorough investigation of the extraction rates and the extraction yields of 6 chemical elements (Ni, Mg, P, K, Fe and Mn) from Alyssum murale ashes is proposed. In this purpose, the impact of several parameters (temperature, stirring speed, acid concentration) on the extraction rates and on the extraction yields of each element was studied. Our first results showed that the acid leaching kinetics were neither limited nor controlled by external film diffusion. Depending on the chemical element, the impact of temperature and acid concentration were significant since the extraction yields and rates increased by increasing either the temperature or the acid concentration. All the data collected were of great consequence since it allows us to investigate and estimate the optimum conditions of selective leaching of nickel by using a Box-Behnken design of experiments. We also found that the nickel extraction rate can be perfectly estimated by the shrinking core model where only internal diffusion occurred; in this model, the apparent activation energy was estimated to be 60 kJ/mol and the nickel extraction rate is expressed by the following equation: 1 - 3(1 - X-Ni)(2/3) + 2 (1 - X-Ni) = k(d,s)t = 630.10(3) exp(-60.10(3)/RT) t. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.