ABSTRACT
Li-ion batteries (LIBs) should be recycled because of the environmental reasons and this type of waste represents an important secondary source of metals. This work aimed to evaluate the recovery of Co and Li from LIBs by hydrometallurgy. The efficiency of different leachants was tested: H2SO4 (2 M), fermentation effluent with supplementation of organic acids (lactic, acetic, butyric and propionic acids) (3.4 M) and a combination of fermentation effluent (0.75 M) and H2SO4 (1.25 M). In addition, the effect of H2O2, glucose P.A., lactose P.A. and from milk whey permeate (MWP) as reducing agent was tested. The leaching solution composed of H2SO4 and fermentation effluent showed high potential of metals recovery in addition to being an alternative of reducing the volume of inorganic acid and the cost by using a fermentation effluent since its use may be integrated with a waste treatment process. Based on Central Composite Designs, optimum conditions of leaching were established, as temperature of 86°C, solid-liquid ratio of 18.5 g/L, leaching time 2.5 h, agitation of 300 rpm and concentration of 0.09 M of lactose from MWP and recovery level achieved was 93.35% of Co and 90.50% of Li. In order to evaluate the influence of each organic acid present on the fermentation effluent, testes were carried out using pure organic acid with H2SO4 (0.75 M:1.25 M) or isolated (3.4 M) and inferior recoveries were detected proving that mixture of organic acids and further compounds as phenolic groups characteristic of fermentation effluent improves the leaching process.
Subject(s)
Cobalt , Lithium , Electric Power Supplies , Hydrogen Peroxide , Recycling , Sulfuric AcidsABSTRACT
Hydrogen production by biological route is a potentially sustainable alternative. Nowadays, energy production from sustainable sources has become urgent for several countries as well as for international policies. In this perspective, hydrogen has gained substantial global attention as clean, sustainable, and versatile energy carrier. In the current work, the resulting effluent from dark fermentation, rich in organic acids, was used as substrate for the purple non-sulfur bacteria (PNS) Rhodobacter capsulatus. In the first stage, experiments were carried out in bioreactors of 50 mL to check the influence of the composition of the effluent dark fermentation. The results proved that the provision of a sugar source improved bio-H2 production. The lactose and lactic acid concentrations exceeding 4.4 and 12 g/L, respectively, resulted in a productivity of up to 37.14 mmol H2/L days. Based on initial conditions obtained on the previous assays, in the second stage, a photo-fermentation in enlarged scale (1.5 L) was performed with the purpose to monitor the production of hydrogen and metabolites, sugar consumption and growth cells during the process. It was observed that the maximum productivity obtained was 98.23 mmol H2/L days in 26 h of process.
ABSTRACT
Hydrogen is a promising alternative for the increased global energy demand since it has high energy density and is a clean fuel. The aim of this work was to evaluate the photo-fermentation by Rhodobacter capsulatus, using the dark fermentation effluent as substrate. Different systems were tested by changing the type of sugar in the dark fermentation, investigating the influence of supplementing DFE with sugar and adding alternate and periodically lactose and glucose throughout the process. The supplementation of the DFE with sugar resulted in higher H2 productivity and the replacement of the sugars repeatedly during the photo-fermentation process was important to maintain the cell culture active. By controlling the residual amount of sugar, bacteria inhibition was avoided; lactic acid, that was toxic to the biomass, was consumed and the metabolic route of butyric acid production was predominant. Under optimum conditions, the H2 productivity reached 208.40mmolH2/Ld in 52h.
