Elsevier

Hydrometallurgy

Volume 195, August 2020, 105387
Hydrometallurgy

Kinetics of two-step bioleaching of Ni and Co from iron rich-laterite using supernatant metabolites produced by Salinivibrio kushneri as halophilic bacterium

https://doi.org/10.1016/j.hydromet.2020.105387Get rights and content

Highlights

  • Indirect bioleaching of Ni and Co bearing laterite was investigated using Salinivibrio kushneri as halophilic bacterium.

  • NaCl addition resulted in the increase of Ni and Co recoveries and the decrease of Fe dissolution by sulfuric acid.

  • Gluconic, lactic and citric acids were main acids in supernatant metabolite of Salinivibrio kushneri.

  • Ni and Co recoveries by supernatant metabolite of Salinivibrio kushneri reached to 58.4 and 60.6%, after 3 h at 90 °C.

  • Chemical control was effective on dissolution rate of the laterite using supernatant metabolites of Salinivibrio kushneri.

Abstract

In the laterite leaching process using sulfuric acid, the addition of NaCl, for example at amount of 10% of solid weight, at 70 °C resulted the increase of nickel and cobalt recoveries up to 18.13 and 25.07%, respectively, and significant decrease in iron dissolution to 39.94% in leaching solution. Due to the role of salts in increasing the dissolutions of nickel and cobalt and decreasing iron dissolution, in this study, the possibility of using salt-friendly bacteria to extract nickel and cobalt from iron-rich laterite was investigated. The halophilic bacterium was isolated from Shorgaz Hamoon soil and grown in the medium with 10% NaCl. Results of HPLC analysis showed that gluconic acid (14.84 g/l), lactic acid (4.58 g/l) and citric acid (1.56 g/l) were the main organic acids in the supernatant metabolite of Salinivibrio kushneri as halophilic bacterium. Leaching experiments were performed at temperatures of 45 °C, 75 °C and 90 °C at pH of 0.5, stirring speed of 370 rpm, solid percentage of 6.67% w/v for 3 h. The results showed that recoveries of nickel and cobalt could reach to 58.40% and 60.6%, respectively after 3 h at 90 °C using supernatant metabolites of halophilic bacterium. Activation energies (Ea) for the chemical control model were 41.32 kJ/mol for nickel, and 40.24 kJ/mol for cobalt that these values indicated chemical control had more effect on the iron-rich laterite dissolution rate using supernatant metabolites produced by Salinivibrio kushneri than diffusion control.

Introduction

Nickel is a strategic metal and has new industrial and metallurgical applications (Sadat et al., 2016). This metal is used in various applications such as alloying elements in steel making, physical and chemical applications, magnets and rechargeable batteries (Buyukakinci, 2008). As the limited production of nickel from sulfide sources, extraction from oxide ores (laterite) is taking into consideration. In addition, more than 70% of the world's known nickel reserves have been found in laterite deposits (Dalvi et al., 2004; Kim et al., 2010; Sahu et al., 2011; Pawlowska and Sadowski, 2017; Petrus et al., 2018). Recent advances have diminished the superiority of sulfide ores and provided the way for the use of laterites for new research (Krstev et al., 2012). Therefore, laterites will be more important in the future production of nickel and cobalt, and in the future, they are expected to make up 80% of nickel and 90–95% of cobalt deposits (Valix et al., 2009). On the other hand, the majority of cobalt sources appear in laterite ores. The use of cobalt as a strategically important metal in rechargeable batteries, alloys, chemical industries and a wide range of catalytic processes have increased the demand for cobalt worldwide. With increasing the demand for cobalt, the extraction of laterite ores is becoming more important (Li et al., 2010).

The methods of nickel extraction from laterites are divided into two categories: pyrometallurgical and hydrometallurgical methods. Laterites are not suitable for the pyrometallurgical process because of their high iron content. Significant heat should be provided for laterites due to high humidity. As pyrometallurgical processes consume a lot of energy, production costs per ton of nickel increase. Acid leaching of laterites at atmospheric pressure is a hydrometallurgical technology that includes heap or agitator leaching by dilute sulfuric acid, purification of leach solution by chemical precipitation at atmospheric pressure, and nickel recovery from purified leachate by chemical precipitation or solvent extraction (Buyukakinci, 2008). Based on the research on chemical dissolution of laterites, it can be deduced that laterite leaching by sulfuric acid will yield higher recovery than other mineral and organic acids (Alibhai et al., 1993; Tang and Valix, 2004; Doshi and Mishra, 2007; Büyükakinci and Topkaya, 2009; Li et al., 2010; Fatahi et al., 2014; MacCarthy et al., 2014; Önal and Topkaya, 2014; Chang et al., 2016; Astuti et al., 2016; Kursunoglu and Kaya, 2016; Pawlowska and Sadowski, 2017; Li et al., 2018).

Biological leaching of low-grade ores due to their relative simplicity, average operating costs, low investment costs, low input energy, relatively unskilled labor and no environmental damage, has many advantages over other traditional methods (Li et al., 2010; Li et al., 2014; Simate et al., 2010; Ahmadi et al., 2015). Bioleaching is the usage of microorganisms and their metabolic products to dissolve metals from low-grade reserves (Sahu et al., 2011). Microorganisms such as bacteria and fungi convert metal compounds into water-soluble forms and are the biocatalysts for these leaching processes (Krstev et al., 2012).

Studies on the effect of pH, density, particle size, specific surface area, type of microorganism, type of present acids in the produced metabolites, impact of water quality (hyper saline, sub-potable, sea water, and tap water), addition of NaCl and sodium sulfate were applied by researchers for laterite leaching. In 1974, Weston showed that the addition of NaCl up to 45 kg per ton ore (24 g/l NaCl) to the leaching process improved nickel recovery (Weston, 1974). In a study by Cornell et al. (1976), the effect of sodium chloride on limonitic laterite leaching was investigated. Iron complexation with chloride ion was reported in this research. Whittington et al. (2003) investigated the effect of water quality on acid leaching of nickel laterite ore under pressure in the areas with dry climates. They stated that water salinity affects the reactions that occur during leaching. Waste mineralogy, waste volume and mass, total acid consumption, and nickel extraction rate are affected by water salinity. The 95% recovery of nickel in acid leaching under pressure for limonite-type laterite ore in the presence of 2 g/l sodium ion in water (of sodium sulfate origin) was the achievement of Johnson et al. (2005). They noted that based on the acid concentration, the optimal amount of sodium ion would increase and improve recovery. In 2006, Le et al. used Aspergillus foetidus to extract nickel and cobalt from new Caledonian weathered saprolitic ores. Extractions of nickel and cobalt within 12 days of shaking using 1095 ppm of Aspergillus foetidus under weak acidic conditions (pH from 3.8 to 5.7) were 28 and 31%, respectively and associated with 16% iron dissolution. Thangavelu et al. (2006) optimized the study by Le et al. (2006) by adding NaCl during the bioleaching process using the same fungus, and it increased nickel extraction to 45%. Valix et al. (2009) stated that the salinity of the soil and water surrounding the laterite ores affects the fungal performance in in-situ bioleaching processes. Aspergillus foetidus was gradually adapted to salty environments to increase its tolerance to salinity.

Halophilic microorganisms live in hypersaline environments and are known as extremophiles. These salt-friendly and salt-tolerant microorganisms exist in all three groups of archaea, bacteria and eukaryotes (Ventosa and Nieto, 1995; Oren, 2002). They produce various bioactive compounds such as enzymes, pigments, solutes, metabolites and exopolysaccharides that are capable of being present in such salt environments (Yadav et al., 2015). Salt-tolerant acidophilic microorganisms are able to withstand higher concentrations of salts and metals. Microorganisms that can survive in NaCl concentrations above 300 g/l are highly diverse and can be detected by the naked eye because of their pigments (Oren, 2002). Sulfur and iron oxidizers that are salt tolerant have been reported in the mesophilic, moderate thermophilic and thermophilic temperature ranges (Rea et al., 2015). A species of Acidihalobacter prosperus can withstand 50 g/l of NaCl. A combination of acidophilus, most of which was composed of Leptospirillum ferriphilum, was able to withstand 20 g/l NaCl (12 g/l chloride) (Gahan et al., 2010). Most acidophilic and salt-tolerant microorganisms are T. prosperus species that can oxidize both ferrous and sulfur ions at pH 2.5 (Huber and Stetter, 1989). Very low concentrations of NaCl in thermophilic and mesophilic bioleaching experiments play little role in microbial growth (0.6–1.2%), but are very effective in modifying dissolution and precipitation products (Rea et al., 2015). pH is an important factor affecting the bio-sorption process. The pH changes the adsorption of metal ions and changes with the type of adsorbent (biomass) and adsorbed (metal ions) (Ray et al., 2005). In recent years, resistance to heavy metals has been studied in halophilic microorganisms, especially in the Halomonas genus (Nieto et al., 1989; Ventosa et al., 1998; Amoozegar et al., 2007). Sodium and potassium are key elements for enzyme activity in halophiles, and thus enhance bacterial tolerance to heavy metals (Margesin and Schinner, 2001). Halophilic bacteria, having anionic properties at their surface, extracellular polymer production and enzymatic uptake, have great industrial potential for biological condensation and recycling of metals (Benyehuda et al., 2003). Salt-friendly microorganisms naturally require high concentrations of anion and cation for growth (Amoozegar et al., 2007; Amoozegar et al., 2008; du Plessis et al., 2011), whereas ordinary microorganisms do not have this ability, and not only the toxic effect of these compounds is on ordinary microorganisms, even increasing the salt concentration of these toxic compounds also has an inhibitory effect on the growth of ordinary microorganisms, whereas it is not in salt-tolerant bacteria (Amoozegar et al., 2008; du Plessis et al., 2011). Various investigations have been carried out on the variation of halophilic species, amount of inoculated biomass, pH, contact time, amount of NaCl and other compounds of culture medium, temperature, etc. The results of this research are summarized as: Halophilic bacteria have better growth at the temperature of 28–37 °C and at pH 7–8 in the medium with 5–20% of NaCl. Different halophilic species are very capable to remove heavy metals in different culture mediums; for example Nesterenkonia sp. strain MF2 and Salinicoccus sp. strain QW6, which are a part of moderately halophile group, respectively, removed chromate and tellurite. Biosorption of Pb(II) on washed biomass in an optimal amount equal to 1.8 g/l)dry basis) of the Bacillus cereus M116 strain and fermentation time of 30 h was determined (Ray et al., 2005; Amoozegar et al., 2007; Amoozegar et al., 2008; Azhar et al., 2014; Rezaeeyan et al., 2017; Safarpour et al., 2019).

As mentioned earlier, nickel and cobalt are important and strategic metals, and despite their potential applications, little researches have been done to extract them. Chemical dissolutions of nickel and cobalt from iron-rich laterites were carried out using sulfuric acid and organic acids in the presence of NaCl by adding 0, 10, 25 and 40% NaCl. The addition of NaCl in the iron-rich laterite leaching process using sulfuric acid had significant results. These results later encouraged the authors of this study to use halophilic microorganisms to dissolve the iron-rich laterite sample, which used in this study. Therefore, for the first time, the feasibility of improving the leaching process using halophilic bacterium to recover nickel and cobalt from laterite ore was investigated. This bacterium was a part of moderate halophiles. It was able to grow in environments containing about 10% salt and was isolated from Shurgaz-e Hamun soil. Mechanisms for dissolutions of nickel and cobalt elements from iron-rich laterite ore using Salinivibrio kushneri as halophilic bacterium by optimizing the parameters temperature and time, and investigating the kinetics of dissolution process (kinetic model type and activation energy) have been discussed in this study.

Section snippets

Sample and characterization studies

The sample used in this study was a laterite type sample which was prepared from eastern Sarbisheh deposit in South Khorasan Province (Iran), with approved reserves of 3,700,000 tons with grades of 1.1% nickel and 0.14% cobalt. It is rich in nickel and cobalt as precious metals and has high iron content.

Elemental analysis of the laterite sample after pre-calcination in the furnace at 500 °C for 2 h (to extract higher nickel and cobalt from the laterite) showed that the average grade of nickel,

Effect of NaCl on the nickel and cobalt dissolutions using sulfuric and organic acids

In this study, as above mentioned, to investigate the effect of NaCl on the nickel and cobalt recoveries from the laterite sample, leaching experiments were performed using 5 M sulfuric acid, 10% solid, stirring speed of 370 rpm at 30 °C, 50 °C and 70 °C by adding 10, 25 and 40% of NaCl for 2 h. Table 2 shows the changes in dissolutions of nickel, cobalt and iron with the above conditions. As it can be seen in Table 2, the recoveries of nickel and cobalt generally increase with increasing

Conclusions

In this research work, the recoveries of nickel and cobalt from iron-rich laterite sample was investigated using sulfuric acid and organic acids in the presence of NaCl, and using supernatant metabolite of Salinivibrio kushneri, and the relevant results were then compared. In the leaching process using sulfuric acid, the addition of NaCl at amount of 10% w/v at 70 °C increased the recoveries of nickel and cobalt by 18.13% and 25.07%, respectively, and decreased the iron dissolution in the

Author contributions

Hadi abdollahi conceived and designed the experiments; Marzieh Hosseini Nasab performed the experiments; Marzieh Hosseini Nasab, Hadi Abdollahi, Mohammad Noaparast and Mohammad Ali Amoozegar analyzed the data; Marzieh Hosseini Nasab and Hadi Abdollahi wrote the paper. Mohammad Noaparast is responsible for ensuring that the descriptions are accurate and agreed by all authors.

Declaration of Competing Interest

The authors claim that they have no conflict of interest.

Acknowledgements

The authors would like to express their gratitudes to Mr. Mehdi Nejad for providing the representative laterite sample from Kanshargh Company. Authors also thank Mr. Hosseini and Mr. Rezai for their assistance in the mineral processing laboratory of the University of Tehran.

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