Leaching of Low- Grade Nickel Ores by Fungi Metabolic Acids

This study was designed to investigate the nature of nickel and cobalt dissolution from limonite and weathered saprolite ores. Chemical leaching was conducted using 1 to 3M of citric, lactic and malic acids. These tests aimed to mimic metal dissolution achieved using heterotrophic or fungi organism and their corresponding metabolic products. The results in this study was able to demonstrate the effect of secondary reaction or adsorption, pulp density and the potential hampering effect of acid neutralizing minerals and acid activity or strength on metal dissolution. Nickel and cobalt dissolution were also found to be dependent on the nature of the host minerals and amenability of these gangue minerals to dehydroxylate as a result of acid attack

Adsorption of Metals from Metal-Organic Complexes Derived from Bioleaching of Nickel Laterite Ores

This study aims to establish the potential of an iminodiacetic-based chelating resin (Purolite S930) in recovering Ni and Co from the biological leachate. The adsorption tests were carried out to compare the hydrogen (H) and sodium (Na) forms of resin. The equilibrium adsorption isotherms were determined using metal citrate complexes with concentrations from 15 to 2000 mg/L. Adsorption tests were carried out for a period of 24 hours to attain adsorption equilibrium. The pH of the solution was varied using citric acid with concentrations of 0.01-1.0 M. The adsorption equilibrium data were interpreted using the Langmuir and Freundlich models. Metal elution was carried out using 2M HNO3 solution. The adsorption behaviors of nickel and cobalt citrate complexes were found to follow both Langmuir and Freundlich models. The results suggested that metal uptake were influenced by the hydrolysis of the resin and competition of metal complexes with the citrate anion and hydronium ion (H+). Metal elution was influenced by the interaction or reaction of metal complexes with the resin which included surface complexation

Different strategies for recovering metals from CARON process residue

http://dx.doi.org/10.1016/j.jhazmat.2011.03.048The capacity of Acidithiobacillus thiooxidans DMS 11478 to recover the heavy metals contained in the residue obtained from the CARON process has been evaluated. Different bioreactor configurations were studied: a two-stage batch system and two semi-continuous systems (stirred-tank reactor leaching and column leaching). In the two-stage system, 46.8% Co, 36.0% Mg, 26.3% Mn and 22.3% Ni were solubilised after 6 h of contact between the residue and the bacteria-free bioacid. The results obtained with the stirred-tank reactor and the column were similar: 50% of the Mg and Co and 40% of the Mn and Ni were solubilised after thirty one days. The operation in the column reactor allowed the solid–liquid ratio to be increased and the pH to be kept at low values (<1.0). Recirculation of the leachate in the column had a positive effect on metal removal; at sixty five days (optimum time) the solubilisation levels were as follows: 86% Co, 83% Mg, 72% Mn and Ni, 62% Fe and 23% Cr. The results corroborate the feasibility of the systems studied for the leaching of metals from CARON process residue and these methodologies can be considered viable for the recovery of valuable metals

Experimental and theoretical studies of Rhodamine B direct dye sorption onto clay-cellulose composite

Dyes are one of the main water pollutants and many biological and environmental problems are associated with them. Rhodamine B (RhB) is one of the most commonly used dye in the textile, printing, paints, and paper industry. The present work reports the sorptive removal of Rhodamine B direct dye from wastewater onto developed cellulose and clay composites. Sorbent material cellulose (48 g) was extracted from 80 g of bagasse. Then cellulose and two types of acid-activated clays were used to make efficient sorbent namely, composite I and II. Various characterization techniques were used to study the physiochemical properties of the synthesized composites. Different sorption affecting parameters were optimized such as initial dye concentration, time, temperature, pH, and composite dose for the efficient sorption of RhB onto composites. Equilibrium time was 60 min for composite-I and 80 min for composite-II Non-linear equilibrium isotherm and kinetic models demonstrated the fitness of Pseudo-second order and Redlich-Peterson isotherm. Composite-I and II removed 85.9% and 95.6% of RhB at pH 2 in 120 min, respectively. The sorption efficiency was checked, and sorbents were applied to real textile effluent which showed promising removal efficiency of over 90%. To confirm the experimental results, computational optimization and vibrational calculations were carried out using the Gaussian 09 program package with 3–21 G, 6–311 G, and 6–311+G basic sets. Geometric parameters showed the planar geometry. In the case of FTIR spectra, fundamental ring vibrations were observed with C-H and C-C. This study suggests that the developed composites have exceptional sorption ability to remove the dye contents from aqueous media

Potential applications of wastes from energy generation particularly biochar in Malaysia.

In Malaysia, abundant agricultural wastes are generated yearly. Therefore it is beneficial to discover new ways to utilize the wastes and employ the carbon source in different industries. Biochar are produced through many heat treatments such as combustion, gasification and pyrolysis for energy generation. The characteristics of these stable carbons such as the physical properties, chemical composition, surface area and surface chemistry determine the effectiveness of the cabon in different applications. Biochar has the ability to retain carbon and this condition is advantageous to prevent the release of carbon back to the atmosphere in the form of carbon dioxide. Application of biochar to soil helps to improve soil fertility and raise agricultural productivity. Biochar also has the ability to reduce carbon dioxide in the flue gas system. There have only been a few studies that discuss on the potential applications of this agriculture waste. The biochar's potential application as carbon sequester for soil application, energy production and dye sorption is being explored in this paper

Torrefied biomass fuels as a renewable alternative to coal in co-firing for power generation

This study aims to assess the torrefaction of biomass as alternative renewable energy fuel to coal during co-firing. It was evaluated that torrefaction improves biomass grindability to such an extent that it can be used in coal mills with coal in co-firing without capital intensive modification. Torrefaction of beech wood was performed on a batch scale reactor at three different temperatures (200, 250 and 300 °C) with 30 min of residence time. The chemical structural changes in torrefied biomass were investigated with binding energies and FTIR (Fourier transform infrared) analysis. Monocombustion and co-combustion tests were performed to examine the combustion behaviour regarding flue gas emissions (CO, NOx and SO2) at 0.5, 1.5 and 2.5 m distance from the burner opening along with fly ash analysis. The FTIR and binding energies showed that lignin hardly affected during light torrefaction while hemicellulosic material was significantly depleted. The Hardgrove grindability index (HGI) was calculated with three methods (DIN51742, IFK and ISO). The medium temperature torrefied biomass (MTTB) yields HGI value in the range of 32–37 that was comparable with HGI of El Cerrejon coal (36–41). A slight change in temperature enabled the torrefied beech wood to be co-milled with coal without capital intensive modification and improved grindability. Comparing the combustion behaviour of single fuels, low temperature torrefied biomass (LTTB) produces less amount of NOx (426 mg/m3), CO (0.002 mg/m3) and SO2 (2 mg/m3) as compared MTTB and raw beech wood. In the case of co-combustion, it was found that blending of coal with raw biomass does not show a stable behaviour. However, premixing of 50% of coal with 50% of torrefied biomasses (MTTB and LTTB) gives most stable behaviour and reduces NOx almost 30% and SOx up to almost 50% compared to coal. The fly ash contents analysis proved that K2O contents much decreased during co-firing of coal and torrefied fuels that could cause ash related issues during combustion of raw biomass

Closed-Loop Recycling of Copper from Waste Printed Circuit Boards Using Bioleaching and Electrowinning Processes

International audienceIn the present study, a model of closed-loop recycling of copper from PCBs is demonstrated, which involves the sequential application of bioleaching and electrowinning to selectively extract copper. This approach is proposed as part of the solution to resolve the challenging ever-increasing accumulation of electronic waste, e-waste, in the environment. This work is targeting copper, the most abundant metal in e-waste that represents up to 20% by weight of printed circuit boards (PCBs). In the first stage, bioleaching was tested for different pulp densities (0.25–1.00% w/v) and successfully used to extract multiple metals from PCBs using the acidophilic bacterium, Acidithiobacillus ferrooxidans. In the second stage, the method focused on the recovery of copper from the bioleachate by electrowinning. Metallic copper foils were formed, and the results demonstrated that 75.8% of copper available in PCBs had been recovered as a high quality copper foil, with 99 + % purity, as determined by energy dispersive X-ray analysis and Inductively-Coupled Plasma Optical Emission Spectrometry. This model of copper extraction, combining bioleaching and electrowinning, demonstrates a closed-loop method of recycling that illustrates the application of bioleaching in the circular economy. The copper foils have the potential to be reused, to form new, high value copper clad laminate for the production of complex printed circuit boards for the electronics manufacturing industry. Graphic Abstract: [Figure not available: see fulltext.] © 2020, The Author(s)

Computational Identification and Analysis of the Key Biosorbent Characteristics for the Biosorption Process of Reactive Black 5 onto Fungal Biomass

The performances of nine biosorbents derived from dead fungal biomass were investigated for their ability to remove Reactive Black 5 from aqueous solution. The biosorption data for removal of Reactive Black 5 were readily modeled using the Langmuir adsorption isotherm. Kinetic analysis based on both pseudo-second-order and Weber-Morris models indicated intraparticle diffusion was the rate limiting step for biosorption of Reactive Black 5 on to the biosorbents. Sorption capacities of the biosorbents were not correlated with the initial biosorption rates. Sensitivity analysis of the factors affecting biosorption examined by an artificial neural network model showed that pH was the most important parameter, explaining 22%, followed by nitrogen content of biosorbents (16%), initial dye concentration (15%) and carbon content of biosorbents (10%). The biosorption capacities were not proportional to surface areas of the sorbents, but were instead influenced by their chemical element composition. The main functional groups contributing to dye sorption were amine, carboxylic, and alcohol moieties. The data further suggest that differences in carbon and nitrogen contents of biosorbents may be used as a selection index for identifying effective biosorbents from dead fungal biomass

Manganese and cobalt redox cycling in laterites; Biogeochemical and bioprocessing implications

This research was developed during the PhD studies of Agustín Solano Arguedas in the University of Manchester, United Kingdom. PhD scholarship was funded by the Ministerio de Ciencia, Tecnología y Telecomunicaciones (MICITT) of the Government of Costa Rica and the Universidad de Costa Rica (UCR). Agustín Solano Arguedas is a researcher at the Unidad de Recursos Forestales (Reforesta, Unit of Forest Resources) of the Instituto de Investigaciones en Ingeniería (INII, Engineering Research Institute), UCR.Cobalt is essential for the modern technology that underpins the decarbonisation of our economies, but its supply is limited leading to its designation as a critical metal. Cobalt biogeochemistry is poorly understood, yet knowledge of how biogeochemical cycling impacts cobalt behaviour could assist the development of new techniques to recover cobalt from ores, and so improve the security of supply. Laterites are an important source of cobalt, they are primarily processed for nickel using energy or chemical intensive processes, with cobalt recovered as a by-product. Metal-reducing conditions were stimulated in laterite sediment microcosms by the addition of simple and cheaply available organic substrates (acetate or glucose). At the end of the experiment the amount of easily recoverable cobalt (aqueous or extractable with acetic acid) increased from < 1% to up to 64%, which closely mirrored the behaviour of manganese, while only a small proportion of iron was transformed into an easily recoverable phase. Sequencing of the microbial community showed that the addition of organic substrates stimulated the growth of indigenous prokaryotes closely related to known manganese(IV)/iron(III)-reducers, particularly from the Clostridiales, and that fungi assigned to Penicillium, known to produce organic acids beneficial for leaching cobalt and nickel from laterites, were identified. Overall, the results indicate that the environmental behaviour of cobalt in laterites is likely to be controlled by manganese biogeochemical cycling by microorganisms. These results are compelling given that similar behaviour was observed in four laterites (Acoje, Çaldağ, Piauí and Shevchenko) from different continents. A new bioprocessing strategy is proposed whereby laterites are treated with an organic substrate to generate metal-reducing conditions, then rinsed with acetic acid to remove the cobalt. Not only are organic substrates environmentally-friendly and potentially sourced from waste carbon substrates, a minimal amount of iron oxides was mobilised and consequently less waste generated.Natural Environment Research Council/[CoG3 NE/M011518/1]/NERC/Reino UnidoDiamond Light Source/[SP16735]//Reino UnidoDiamond Light Source/[SP17313]//Reino UnidoOffice of Science User Facility/[DE-AC02-05CH11231]//Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII