Influence of mesophilic and thermophilic on enrichment and chemical speciation of toxic and valuable elements in digestate

2021 ◽  
Author(s):  
Nazia Zaffar ◽  
Erik Ferchau ◽  
Hermann Heilmeier ◽  
Oliver Wiche
Keyword(s):  
Sequential Extraction ◽  
Ammonium Acetate ◽  
Extraction Procedure ◽  
Gas Production ◽  
Low Grade ◽  
Polluted Soils ◽  
Liquid Phases ◽  
Thermophilic Fermentation ◽  
Thermophilic Conditions ◽  
Higher Temperature

<p>Bioharvesting of toxic and valuable elements by growing high biomass crops in the regions with low-grade mining ores and metal-polluted soils is a new concept in the area of mining termed phytomining. The biomass is used in anaerobic digestion to produce biogas and digestate. To the best of our knowledge, there are limited studies on the enrichment and distribution of heavy metals and economically valuable elements in digestate, obtained from mesophilic and thermophilic fermentation conditions. This study conducted a laboratory experiment to recover and enrich toxic elements (Zn, Cd, Pb, As) and economically valuable elements (Ge and rare earth elements REEs) at mesophilic (37⁰C) and thermophilic (55⁰C) conditions. To analyze the distribution of these elements in the liquid and solid-state of digestate a three-step sequential extraction procedure was carried out. Microfiltration (0.2µm) was used to separate elements in the solid and liquid phases. The solid digestate was extracted with ammonium acetate (pH 7) and ammonium acetate (pH 5) to determine exchangeable and acid-soluble elements. As a result, we found that thermophilic conditions significantly enriched Zn (3%), Cd (48%), Pb (25%), As (21%), Ge (40%), and REEs (22%) compared to mesophilic conditions. The following elements were enriched in decreasing order Cd > Ge > Pb > REEs > As > Zn. This enrichment may be due to differences in availability of substrates to microorganisms and higher gas production with increased temperature. The sequential extraction revealed that the concentration of elements in dissolved form was significantly increased in thermophilic conditions. While the concentrations in exchangeable are decreased indicating that previous elements bound on exchangeable sites were removed and transferred in solution. Furthermore, the element concentration in the residue fraction was not affected by temperature. Possibly the release of secondary metabolites from microorganisms triggered by higher temperature improved the solubility of elements which is an important prerequisite for element separation and recovery.</p><p> </p>

Chemical fractionation of germanium (Ge) and rare earth elements (REEs) in biogas residue by a two-step sequential extraction procedure

2020 ◽  
Author(s):  
Nazia Zaffar ◽  
Erik Ferchau ◽  
Hermann Heilmeier ◽  
Oliver Wiche
Keyword(s):  
Rare Earth ◽  
Liquid Phase ◽  
Rare Earth Elements ◽  
Sequential Extraction ◽  
Ammonium Acetate ◽  
Extraction Procedure ◽  
Sequential Extraction Procedure ◽  
Chemical Fractionation ◽  
Technical University ◽  
Biogas Residue

<p><strong>Chemical fractionation of germanium (Ge) and rare earth elements (REEs) in biogas residue by a two-step sequential extraction procedure</strong></p><p><strong>Nazia Zaffar (1), Erik Ferchau (2), Hermann Heilmeier (1), and Oliver Wiche (1) </strong></p><p>(1) Technical University of Bergakademie, Freiberg, Institute for Biosciences, Biology/Ecology Group, Germany ([email protected]), (2) Technical University of Bergakademie, Institute for Thermal Engineering and Thermodynamics</p><p><strong> </strong></p><p>Ge and REEs are of increasing interest in phytoremediation and phytomining research. These elements are present in almost all soils and soil-grown plants contain considerable concentrations of these elements in their biomass. The process chain of phytomining involves i) the accumulation of target elements in harvestable plant biomass (phytoextraction), ii) production of bioenergy by burning or biogas production, and iii) the recovery of the elements from bioenergy residues.</p><p>Although literature on bulk concentrations of elements in fermentation residues is extensive until today there is only a little information on how the elements are bound/distributed in the solid/liquid phases of the fermentation residues, particularly for target elements in phytoremediation research such as Ge and REEs. Therefore, we conducted a laboratory experiment in which residues from anaerobic fermentation were separated into liquid/solid by microfiltration. Subsequently the solids were extracted by a two-step sequential extraction procedure. This procedure involved the extraction of solids with ammonium acetate (pH 7) and ammonium acetate (pH 5) to determine exchangeable as well as acid-soluble elements. As a result, we found that total concentrations in the residues were 0.5 µg/g for (Ge) and 8.7 µg/g for (REEs i.e sum of all lanthanides). In the liquid phase concentrations of Ge and REEs were very low ranging from 0.0001 µg/g Ge and 0.003 µg/g REEs respectively. Concentrations of elements in the liquid phase represented 0.01% Ge and 0.04% REEs of the total element concentrations of the material, indicating that most of the elements were bound to solids. Results from the sequential extraction revealed that percentage distribution of elements were 1.2% (exchangeable Ge) 0.5% (exchangeable REEs) and 0.8% (acid-soluble Ge) 3.8%  (acid-soluble REEs) from the total elements of the material. However, we found 99% Ge 98% REEs in residue fractions. We can conclude that most of the Ge and REEs in digestates are most probably bound into organic structures which were not attracted by extraction solutions. This has major implications for the development of methods for the recovery of the target elements were strong acids/or oxidation of organics prior to application of separation.</p><p> </p>

scholarly journals Sequential extraction procedure to obtain the composition of terrigenous detritus in marine sediments

MethodsX ◽  
2020 ◽  
Vol 7 ◽  
pp. 100888
Author(s):  
Margit H. Simon ◽  
Daniel P. Babin ◽  
Steven L. Goldstein ◽  
Merry Yue Cai ◽  
Tanzhuo Liu ◽  
...  
Keyword(s):  
Sequential Extraction ◽  
Marine Sediments ◽  
Extraction Procedure ◽  
Sequential Extraction Procedure

Environmental Availability of Potentially Toxic Elements in an Agricultural Mediterranean Site

2019 ◽  
Vol 25 (2) ◽  
pp. 169-178 ◽  
Author(s):  
Dimitrios Alexakis ◽  
Dimitra Gamvroula ◽  
Eleni Theofili
Keyword(s):  
Sequential Extraction ◽  
Toxic Elements ◽  
Soil Depth ◽  
Extraction Procedure ◽  
Potential Ecological Risk ◽  
Potentially Toxic Elements ◽  
Geochemical Partitioning ◽  
Exchangeable Fraction ◽  
High Bioavailability

ABSTRACT Total contents of 36 potentially toxic elements are summarized for agricultural topsoil (n = 12; soil depth = 0–20 cm), subsoil (n = 12; soil depth = 20–40 cm), and representative rock samples collected from a Mediterranean site (Megara Plain, Greece). The five-stage sequential extraction procedure for the geochemical partitioning of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), and nickel (Ni), proposed by Tessier, was applied to topsoil and subsoil collected from the study area. Soil Cd was highly associated with exchangeable fraction, illustrating high bioavailability of this element. The order of mobility of the elements was as follows: Cd > Cu > Co > Zn > Ni > Cr > Mn. Results from sequential extraction experiments illustrated that the bioavailability of Cu, Co, and Zn is moderate, while Ni, Cr, and Mn presented low bioavailability, indicating that these elements could pose a limited threat to the quality of crops. Cadmium is the chief contamination controlling factor posing moderate potential ecological risk. The contamination sources of the examined elements are discussed.

Insights into Heap Bioleaching at the Agglomerate-Scale

2017 ◽  
Vol 262 ◽  
pp. 185-188 ◽  
Author(s):  
Alison Cox ◽  
Christopher G. Bryan
Keyword(s):  
Interstitial Cell ◽  
Cell Concentration ◽  
Low Grade ◽  
Dissolved Metals ◽  
Copper Ore ◽  
Cell Numbers ◽  
Liquid Phases ◽  
Heap Bioleaching ◽  
Cell Concentrations ◽  
The Difference

Previous agglomerate-scale heap bioleaching studies have outlined the variations in cell numbers of the liquid and attached phases during colonisation of sterilised ore by a pure culture. In this study, a mixed mesophilic culture was used in agglomerate-scale columns containing non-sterilised low-grade copper ore. Over a six - month period, columns were harvested at various intervals to provide snapshots of the metal distribution and the quantity, location, and ecological variations of mineral-oxidizing microbes within the ore bed. The initial colonisation period in this experiment was dissimilar to previous work, as the indigenous community was retained within the ore-bed throughout acid agglomeration. The overall colonisation phase lasted for approximately 1,000 hours until cell concentrations stabilised. In each column, less than 0.05% of the total cells were found in the leachate, 15-20% in the interstitial phase and the remaining ~80% were attached to the mineral surface. Once cell numbers had stabilised, interstitial cell concentrations were approximately 2,000× greater than those in the leachate. This difference persisted for the duration of the experiment. Copper concentrations in the two liquid phases generally decreased over time, but were on average 50× higher in the interstitial phase. Iron concentrations were more stable, but again were 30× higher in the interstitial phase. This demonstrates that that the difference in cell concentration between the leachate and interstitial phases cannot be explained through diffusion gradients within the system as it is much greater than those observed for the dissolved metals. It also shows that the specific environmental conditions of the interstitial and attached cells are very different to those inferred through analysis of leachates alone.

Study of Low-Grade Nickel Laterite Processing Using Palm Shell Charcoal as Reductant

2020 ◽  
Vol 1000 ◽  
pp. 436-446
Author(s):  
Bambang Suharno ◽  
Nolzha Primadha Ilman ◽  
Achmad Shofi ◽  
Deni Ferdian ◽  
Fajar Nurjaman
Keyword(s):  
Sodium Sulfate ◽  
Selective Reduction ◽  
Reduction Process ◽  
Low Grade ◽  
X Ray Diffraction ◽  
X Ray ◽  
Palm Shell ◽  
Higher Temperature ◽  
Nickel Grade

This study was conducted to investigate the effect of palm shell charcoal reductant in the selective reduction of nickel ore with the addition of additive at various temperatures and times. In this present work, 10 wt. % of sodium sulfate as additive and 5, 10, 15 wt. % of palm shell charcoal as reductants were used. The reduction of nickel ore was performed at 950oC, 1050oC, and 1150oC for 60, 90, and 120 minutes. A wet magnetic separation method was then carried out to separate the concentrates and tailings. Characterization of reduced ore was performed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), while the composition of ferronickel in concentrate was identified by X-Ray Fluorescence (XRF). The result showed that the higher temperature reduction, the higher of nickel grade, and its recovery at the concentrate. Nevertheless, the longer reduction time and the more reductant in nickel ore lowering the nickel grade and its recovery in the concentrate. The optimum condition in this selective reduction process was obtained with the addition of 5 wt. % of reductant and 10 wt. % of sodium sulfate in nickel ore, which was reduced at 1150oC for 60 minutes. It resulted in 4.60% and 73.23% for nickel grade and its recovery, respectively.

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