A new process for nickel ammonium disulfate production from ash of the hyperaccumulating plant Alyssum murale
Résumé
The extraction of nickel (Ni) from ultramafic soils by phytomining can be achieved using Alyssummurale cultures. This study presents anewprocess for the valorization of Ni accumulated by this plant through the production of a Ni ammoniumdisulfate salt (Ni(NH4)2(SO4)2.6H2O). The process comprises an initial leaching of the ashes of A. murale with a sulphuric acid solution (1.9 M H2SO4, T = 95 °C, t = 240 min, TS = 150 g ash L− 1), producing a leachate rich in Ni (10.2 g Ni L− 1; 96% Ni solubilisation), Mg, P, K, Fe, Ca and Al. The pH of the acid leachate is increased to 5.0 with NaOH (5 M), followed by an evaporation step which produced a purified solution rich in Ni (21.3 g Ni L− 1) and an iron hydroxide precipitate. The cold crystallization (T = 2 °C, t = 6 h) of this solution by the stoichiometric addition (× 1.2) of ammonium sulfate generates a Ni ammoniumdisulfate salt, containing 13.2% Ni, that is potentially valuable to industry.