A new process for nickel ammonium disulfate production from ash of the hyperaccumulating plant Alyssum murale
Highlights
► Ni accumulated by phytomining is solubilized by H2SO4 leaching at 95 °C. ► Ni solubilized is recovered after iron precipitation and cold crystallization. ► Ni ammonium disulfate salt (Ni(NH4)2(SO4)2·6H2O) produced contains 13.2% Ni.
Introduction
Phytomining uses metal accumulating plants as miners to extract commercially valuable metals, these metals being initially present in mineralized soils that cannot be exploited by traditional mining methods (Chaney et al., 2007, Barbaroux et al., 2009). The application of phytoextraction principles for phytoremediation or phytomining proposes the use of plants that can annually accumulate sufficient quantities of metals like Ni, Zn, Cd, Se, Co, As or Ti (Baker and Brooks, 1989).
More than 400 species of plants, representing about 45 families, have been identified as hyperaccumulators and two thirds of these accumulate Ni (Brooks, 1998, Chaney et al., 2007).
Nickel is present at trace concentrations in all compartments of terrestrial environments, except in serpentine minerals and soils, where concentrations are higher. Serpentine soils stem from the alteration of ultramafic rocks and are widely distributed around the world (Brooks, 1987, Ghaderian et al., 2007). These soils are characterized by a pH between 6 and 8 and abnormally high concentrations of metals like Ni, Cr and Co, as well as high concentrations of Fe and Mg and low concentrations of Ca. Other elements K, P and S are present at trace concentrations (Shallari et al., 1998). The concentration of Ni in these soils varies from 0.5 to 8 g Ni kg− 1 of soil (Bani et al., 2007).
Nickel based chemicals are used for electrolytic plating, fabrication of batteries (nickel hydroxide is used in Ni-Cd batteries), paint pigment fabrication and as catalysts for a number of chemical reactions (Kerfoot et al., 1995). Ni being a transition metal, Ni compounds are numerous and not all of them are interesting. However, chemicals like Ni ammonium disulfate salts used for electrolytic plating are more valuable than, for example, nickel destined for the production of alloys (Kerfoot et al., 1995). The precipitation of Ni ammonium disulfate salts is possible through the addition of ammonium sulfate to a concentrated nickel sulfate solution. The physical properties of nickel sulfate and ammonium in solution have been studied and quantified (Linke, 1965, Mullin and Osman, 1967, Mullin and Osman, 1976).
The hyperaccumulating plant Alyssum murale can accumulate up to 20,000 mg Ni kg− 1 dry weight and a biomass of 10,000 kg ha− 1 can be harvested per year (Chaney et al., 2007). Serpentine soils contain Ni at concentrations between 1000 and 7000 mg kg− 1. These concentrations are well below the exploitation threshold required by traditional mining (30,000 mg kg− 1), but sufficient to allow the extraction and accumulation of Ni by hyperaccumulating plants (Baker and Brooks, 1989, Shallari et al., 1998, Broadhurst et al., 2004).
Once harvested and dried, A. murale can be treated by pyrometallurgy in a smelter (Chaney et al., 2007) to produce metallic nickel or by leaching to produce a concentrated nickel leachate (Wood et al., 2006). It would therefore be plausible to produce a pure and commercializable Ni from harvested and chemically treated A. murale grown on serpentine soils.
It has been demonstrated that the leaching of A. murale seeds in sulphuric acid (0.5 M at 90 °C) for 120 min with a 15% solids fraction, followed by two washing steps, allowed the extraction of 97% of the available Ni (Barbaroux et al., 2009). However, a previous study demonstrated that the recovery of Ni in this type of leachate using selective precipitation or electrodeposition was not economically feasible (Barbaroux et al., 2011). In effect, Ghorbani et al. (2002) demonstrated the influence of organic complexes during metal electrolysis. Only a process using the solvent Cyanex 272, a phosphonic acid known for its ability to separate nickel from other metals (e.g. Co), allowed the selective extraction of Ni to an aqueous solution (Barbaroux et al., 2011). Despite the selectivity and high yield of the selective extraction using solvents, a difficult optimization procedure would be required given the prohibitive cost of Cyanex 272 (Barbaroux et al., 2011).
Koppolu et al. (2004) demonstrated that the incineration of hyperaccumulating plants concentrated in Ni, Cu and Zn at 600 °C allowed the recovery of 99% of the total metals as an ash concentrate. The concentrations increased by a ratio of 3.2 to 6 compared to concentrations found in the dry plant matter. This approach appears to be the most feasible from both an economic and environmental standpoint (Harris et al., 2009).
Metal extraction technologies using hyperaccumulating plants and their valorization present difficulties and uncertainties that put into question the cost effectiveness of phytomining. Therefore, there exists a need to remove some of the disadvantages associated with these metal production technologies that would lead to a reliable and profitable production of metals, and their derivatives, extracted by plants. This study describes the steps required to produce a Ni ammonium disulfate salt from the ashes of the plant A. murale.
Section snippets
Sampling and preparation of the plants
Samples of A. murale were harvested in July 2009, while the plants were flowering, near the village of Pojske in the region of Pogradec in Albania (latitude: 40°59′55.28″N; longitude: 20°38′0.92″E). The soils in this region are ultramafic with Ni concentrations on the order of 3.0 g Ni kg− 1 soil. The Ni concentration in the superficial soil layer in Pojske (0 to 25 cm depth) was measured at 3440 mg Ni kg− 1. Plants were collected by hand, sun dried, and kept at ambient temperatures (20 ± 2 °C) until
Preparation of the plant A. murale
Metal distributions in the aerial tissues and stems of the plant A. murale are given in Table 1. Results show an elevated overall Ni concentration of 9.7 g Ni kg− 1 dw, in accordance with literature values for A. murale that range between 8.4 and 9.1 g Ni kg− 1 dw (Shallari et al., 1998, Bani et al., 2007). Previous studies had already observed high Ni concentrations in the aerial, harvestable, parts of A. murale (Shallari et al., 1998, Broadhurst et al., 2004, Bani et al., 2007, Chaney et al., 2007
Conclusions
The present study describes a novel process for the valorization of the Ni from the ashes of hyperaccumulating plants through the production of a chemical compound containing Ni. The selective recovery of Ni ammonium disulfate salts in aqueous solutions produced from hyperaccumulating plants appears as an effective method to extract Ni. The process comprises the following steps: 1) leaching of the ashes using acid solution, producing a leachate rich in Ni and Fe; 2) the selective precipitation
Acknowledgments
The authors would like to thank Dr Bani for plant harvesting. Sincere thanks are extended to the Ministère du Développement Économique, de l'Innovation et de l'Exportation (MDEIE), the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs, and the Institut National Polytechnique de Lorraine for their financial contributions.
References (21)
- et al.
A new method for obtaining nickel metal from the hyperaccumulator plant Alyssum murale
Sep Purif Technol
(2011) - et al.
Chemical leaching of nickel from the seeds of the metal hyperaccumulator plant Alyssum murale
Hydrometallurgy
(2009) - et al.
Indicative assessment of the feasibility of Ni and Au phytomining in Australia
J Cleaner Prod
(2009) - et al.
Comparison of organic compounds removal by coagulation–flocculation and by adsorption onto preformed hydroxide flocs
Water Res
(1994) - et al.
Pyrolysis as a technique for separating heavy metals from hyperaccumulators.Part III: pilot-scale pyrolysis of synthetic hyperaccumulator biomass
Biomass Bioenergy
(2004) - et al.
Heavy metals in soils and plants of serpentine and industrial sites of Albania
Sci Total Environ
(1998) - et al.
Crystallization and agglomeration kinetics of nickel ammonium sulfate in an MSMPR crystallizer
Powder Technol
(1985) Standard methods for the examination of water and wastewater
(1999)- et al.
Terrestrial higher plants which hyperaccumulate metallic elements — a review of their distribution, ecology and phytochemistry
Biorecovery
(1989) - et al.
In-situ phytoextraction of Ni by a native population of A. murale on an ultramafic site (Albania)
Plant Soil
(2007)
Cited by (74)
Valorization of heavy metal contaminated biomass: Recycling and expanding to functional materials
2022, Journal of Cleaner ProductionRecovery of nickel from strongly acidic bio-ore leachate using a bispicolylamine-based chelating resin
2022, Separation and Purification TechnologyFarming for battery metals
2022, Science of the Total EnvironmentCitation Excerpt :Sustainable alternative sources need to be explored to meet the growing demand for metals. One such approach is agromining, which produces metal products from harvested biomass of a ‘metal crop’ (Barbaroux et al., 2012; van der Ent et al., 2015). For instance, battery-grade nickel sulfate can be made in one step from nickel-rich bio-ore obtained from nickel ‘metal crops’.
Thermochemical conversion of heavy metal contaminated biomass: Fate of the metals and their impact on products
2022, Science of the Total Environment