Acid-free Extracts Research Articles

Acid-free extraction of valuable metal elements from spent lithium-ion batteries using waste copperas

A large amount of hazardous spent lithium-ion batteries (LIBs) is produced every year. Recovery of valuable metals from spent LIBs is significant to achieve environmental protection and alleviate resource shortages. In this study, a green and facile process for recovery of valuable metals from spent LIBs by waste copperas was proposed. The effects of heat treatment parameters on recovery efficiency of valuable metals and the redox mechanism were studied systematically through phase transformation behavior and valence transition. At low temperature (≤460 °C), copperas reacted with lithium on the outer layer of LIBs preferentially, but the reduction of transition metals was limited. As the temperature rose to 460–700 °C, the extraction efficiency of valuable metals was greatly enhanced due to the generation of SO2, and the gas–solid reaction proceeded much fast than the solid–solid reaction. In the final stage (≥700 °C), the main reactions were the thermal decomposition of soluble sulfates and the combination of decomposed oxides with Fe2O3 to form insoluble spinel. Under the optimum roasting conditions, i.e., at a copperas/LIBs mass ratio of 4.5, and a roasting temperature of 650 °C and roasting time of 120 min, the leaching efficiencies of Li, Ni, Co and Mn were 99.94%, 99.2%, 99.5% and 99.65%, respectively. The results showed that valuable metals can be selectively and efficiently extracted from the complex cathode materials by water leaching. This study used waste copperas as an aid to recover metals and provided an alternative technical route for green recycling of spent LIBs.

A novel linear displacement isothermal amplification with strand displacement probes (LDIA-SD) in a pocket-size device for point-of-care testing of infectious diseases

Nucleic acid amplification is crucial for disease diagnosis, especially lethal infectious diseases such as COVID-19. Compared with PCR, isothermal amplification methods are advantageous for point-of-care testing (POCT). However, complicated primer design limits their application in detecting some short targets or sequences with abnormal GC content. Herein, we developed a novel linear displacement isothermal amplification (LDIA) method using two pairs of conventional primers and Bacillus stearothermophilus (Bst) DNA polymerase, and reactions could be accelerated by adding an extra primer. Pseudorabies virus gE (high GC content) and Salmonella fimW (low GC content) genes were used to evaluate the LDIA assay. Using strand displacement (SD) probes, a LDIA-SD method was developed to realize probe-based specific detection. Additionally, we incorporated a nucleic acid-free extraction step and a pocket-sized device to realize POCT applications of the LDIA-SD method. The LDIA-SD method has advantages including facile primer design, high sensitivity and specificity, and applicability for POCT, especially for amplification of complex sequences and detection of infectious diseases.

Acid-free extraction of manganese from pyrolusite tailings by in situ redox interaction with waste copperas

Pyrolusite tailings (PTs) is a solid waste discharged from the mining of high grade pyrolusite, and is also regraded as an important secondary resource of manganese. However, its extraction requires an expensive reductant used for the reduction of Mn(IV) to low valence. In this paper, an innovative process using in situ redox interaction of PTs with waste copperas (as reductant and sulfating agent) followed by water leaching for efficient manganese extraction was proposed. The in situ redox interaction mechanism was investigated systematically. At lower temperatures (＜500 °C), Fe(II) was the main reductant by direct solid-to-solid reaction. In the temperature range of 500–650 °C, the Mn(IV) in PTs was reduced to Mn(II) due to the synergistic effect of Fe(II) and SO2, and then Mn(II) was sulfated into water-soluble MnSO4. The reduction of Fe(III) into Fe(II) by SO2 occurred i.e. the Fe(II)⇌Fe(III) redox cycle. And the generated FeSO4 continued to react with PTs, indicating that the Fe(II)⇌Fe(III) redox cycle facilitated the extraction of manganese. Furthermore, high roasting temperatures caused MnSO4 to decompose into insoluble Mn2O3, inhibiting the extraction.

Hydrofluoric Acid-Free Extraction of Ta and Nb from a Coltan Ore (Lulingu, Drc) Through Alkaline Roasting, Water Leaching, Precipitation and Oxalic Acid Leaching

Hydrofluoric Acid-Free Extraction of Ta and Nb from a Coltan Ore (Lulingu, Drc) Through Alkaline Roasting, Water Leaching, Precipitation and Oxalic Acid Leaching

An investigation on hydrofluoric (HF) acid-free extraction for niobium oxide (Nb2O5) and tantalum oxide (Ta2O5) from columbite/tantalite concentrates using alkali reductive roasting

Tantalum, niobium, and their oxides are important precursor materials, essential for high-temperature alloys and electronic devices. The primary hydrometallurgical extraction technique to extract tantalum and niobium from minerals involves hydrofluoric acid (HF) digestion of the concentrates, followed by solvent extraction as an oxide separation and purification step. Solvent extraction, on the other hand, releases organic solvents which are lost irreversibly via natural evaporation during the process. This research demonstrates a novel chemical process for the extraction and refining of columbite and tantalite concentrates (29% Ta2O5 and 16% Nb2O5). In this process, the concentrates are reduced using carbon and alkali in the temperature range of 800–950 °C, which helps in reducing and magnetically separating the iron oxides present in the concentrates as metallic iron. The remaining residue is rich in alkali complex (e.g., sodium tantalates and niobates) formed during the roasting process which was reclaimed as a purified mixture of oxides of Nb2O5 and Ta2O5, by using oxalic acid leaching, followed by sodium bisulphate roasting.

An integrated valorization of industrial waste of eggplant: Simultaneous recovery of pectin, phenolics and sequential production of pullulan

Based on a bio-refinery concept, the valorization of eggplant peel wastes (EPW) in the production of multiple value-added products was aimed. The acid-free extraction process was applied in the simultaneous recovery of pectin and phenolic compounds. The extraction variables were optimized by response surface methodology using a Box-Behnken design and the maximum yield of pectin (26.1%) and phenolic compounds (20.2%) was obtained in the extraction temperature of 90 °C, time of 90 min and liquid/solid ratio of 40 mL/g. After recovery of pectin and phenolic compounds from EPW, the solid leftovers were enzymatic hydrolyzed and the hydrolysates were used as a carbon source in the microbial production of pullulan by Aureobasidium pullulans. The produced pectin and pullulan were characterized through the chemical and structural features. The results of FT-IR and H-NMR analysis approved the predominant presence of these two polysaccharides in the isolated samples. On the other hand, the antioxidant activity of the recovered phenolic compounds extract was evaluated by DPPH and ABTS radical scavenging activity and reducing power assay.

The Bio-Functional Properties of Pigmented Cereals may Involve Synergies among Different Bioactive Species.

This study was aimed at characterizing the anthocyanins and phenolics profile in different varieties of pigmented corn and wheat and in some of their milling fractions. Acid/ethanol extracts were used to assess total anthocyanins, overall antioxidant activity, the overall polyphenol profile, and for evaluating the inhibition of pancreatic α-amylase and of intestinal α-glucosidase. Both enzymes were inhibited in a dose-dependent manner by all extracts, but individual extracts had specific effects on each enzyme. Anti-inflammatory response was evaluated by using acid-free extracts and Caco-2 cells transiently transfected with a luciferase reporter gene responding to cytokine stimulation. The immune response of interleukin-stimulated cells decreased significantly in a dose-dependent manner in the presence of 20-50 μM/l anthocyanins from all grains extracts, again with a different efficiency. The inhibitory ability and the anti-inflammatory capability of these extracts are in most cases higher than in similar extracts from other sources, suggesting that activities in each extract may imply specific synergies between anthocyanins and other phenolics.

Broad range chemical profiling of natural deep eutectic solvent extracts using a high performance thin layer chromatography–based method

Natural deep eutectic solvents (NADES) made mainly with abundant primary metabolites are being increasingly applied in green chemistry. The advantages of NADES as green solvents have led to their use in novel green products for the food, cosmetics and pharma markets. However, one of the main difficulties encountered in the development of novel products and their quality control arises from their low vapour pressure and high viscosity. These features create the need for the development of new analytical methods suited to this type of sample. In this study, such a method was developed and applied to analyse the efficiency of a diverse set of NADES for the extraction of compounds of interest from two model plants, Ginkgo biloba and Panax ginseng. The method uses high-performance thin-layer chromatography (HPTLC) coupled with multivariate data analysis (MVDA). It was successfully applied to the comparative quali- and quantitative analysis of very chemically diverse metabolites (e.g., phenolics, terpenoids, phenolic acids and saponins) that are present in the extracts obtained from the plants using six different NADES. The composition of each NADES was a combination of two or three compounds mixed in defined molar ratios; malic acid-choline chloride (1:1), malic acid-glucose (1:1), choline chloride-glucose (5:2), malic acid-proline (1:1), glucose-fructose-sucrose (1:1:1) and glycerol-proline-sucrose (9:4:1). Of these mixtures, malic acid-choline chloride (1:1) and glycerol-proline-sucrose (1:1:1) for G. biloba leaves, and malic acid-choline chloride (1:1) and malic acid-glucose (1:1) for P. ginseng leaves and stems showed the highest yields of the target compounds. Interestingly, none of the NADES extracted ginkgolic acids as much as the conventional organic solvents. As these compounds are considered to be toxic, the fact that these NADES produce virtually ginkgolic acid-free extracts is extremely useful. The effect of adding different volumes of water to the most efficient NADES was also evaluated and the results revealed that there is a great influence exerted by the water content, with maximum yields of ginkgolides, phenolics and ginsenosides being obtained with approximately 20% water (w/w).

Effects of lipooligosaccharide inner core truncation on bile resistance and chick colonization by Campylobacter jejuni.

Campylobacter jejuni is the most common bacterium that causes diarrhea worldwide, and chickens are considered the main reservoir of this pathogen. This study investigated the effects of serial truncation of lipooligosaccharide (LOS), a major component of the outer membrane of C. jejuni, on its bile resistance and intestinal colonization ability in chickens. Genes encoding manno-heptose synthetases or glycosyltransferases were inactivated to generate isogenic mutants. Serial truncation of the LOS core oligosaccharide caused a stepwise increase in susceptibilities of two C. jejuni strains, NCTC 11168 and 81-176, to bile acids. Inactivation of hldE, hldD, or waaC caused severe truncation of the core oligosaccharide, which greatly increased the susceptibility to bile acids. Both wild-type strains grew normally in chicken intestinal extracts, whereas the mutants with severe oligosaccharide truncation were not detected 12 h after inoculation. These mutants attained viable bacterial counts in the bile acid-free extracts 24 h after inoculation. The wild-type strain 11-164 was present in the cecal contents at >107 CFU/g on 5 days after challenge infection and after this time period, whereas its hldD mutant was present at <103 CFU/g throughout the experimental period. Trans-complementation of the hldD mutant with the wild-type hldD allele completely restored the in vivo colonization level to that of the wild-type strain. Mutants with a shorter LOS had higher hydrophobicities. Thus, the length of the LOS core oligosaccharide affected the surface hydrophobicity and bile resistance of C. jejuni as well as its ability to colonize chicken intestines.

Role of Conserved Salt Bridges in Homeodomain Stability and DNA Binding

The sequence information available for homeodomains reveals that salt bridges connecting pairs 19/30, 31/42, and 17/52 are frequent, whereas aliphatic residues at these sites are rare and mainly restricted to proteins from homeotherms. We have analyzed the influence of salt and hydrophobic bridges at these sites on the stability and DNA binding properties of human Hesx-1 homeodomain. Regarding the protein stability, our analysis shows that hydrophobic side chains are clearly preferred at positions 19/30 and 31/42. This stabilizing influence results from the more favorable packing of the aliphatic side chains with the protein core, as illustrated by the three-dimensional solution structure of a thermostable variant, herein reported. In contrast only polar side chains seem to be tolerated at positions 17/52. Interestingly, despite the significant influence of pairs 19/30 and 31/42 on the stability of the homeodomain, their effect on DNA binding ranges from modest to negligible. The observed lack of correlation between binding strength and conformational stability in the analyzed variants suggests that salt/hydrophobic bridges at these specific positions might have been employed by evolution to independently modulate both properties.

Rapid micromethod for the purification of Escherichia coli ribonucleic acid polymerase and the preparation of bacterial extracts active in ribonucleic acid synthesis.

A rapid micromethod is described for the preparation of nucleic acid-free extracts from Escherichia coli that involves precipitation with polyethylene glycol. Extracts can be prepared from growing cells in 75 min by three short, low-speed centrifugations. The extract did not inhibit added purified ribonucleic acid (RNA) polymerase, suggesting that major inhibitors of RNA synthesis had been removed. This extract should be ideal for assessing the properties of mutant RNA polymerases. The rapid chromatography of the extracts with step elution from deoxyribonucleic acid- and diethylaminoethyl-cellulose columns resulted in high yields of substantially pure RNA polymerase. We used this technique to purify 35S-labeled RNA polymerase. This system should find application for the purification of small quantities of other bacterial RNA polymerases that share the general chromatographic properties of E. coli RNA polymerase.

Isolation of bacterial and phage proteins by homopolymer RNA-cellulose chromatography.

Nucleic acid-free extracts of Escherichia coli have been analyzed by chromatography on columns of cellulose, to which poly(A), poly(U), or poly(C) have been attached by ultraviolet irradiation. Proteins are released from the columns by stepwise elution with increasingly higher concentrations of salt, followed by washing with urea to remove very tightly bound molecules. The pattern of protein elution is reproducibly different for each of the homopolymer RNA-cellulose columns used: some proteins bind very tightly to one column, but poorly to others. Analysis by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis, by immunological cross-reactivity in double diffusion tests, and by enzymological assays, has allowed the identification of a number of these proteins. The RNA polymerase core enzyme binds to poly(C)- and to poly(U)-cellulose columns, and can be purified to 20 to 30 percent homogeneity in a single step. Ribosomal protein S1 and the termination factor rho bind very tightly to poly(C)-cellulose, and both can be purified to homogeneity rapidly, in much higher yields than previously reported. Poly(A)-cellulose chromatography allows the isolation of large amounts of an 80,000 molecular weight protein having an as yet unassigned cellular function. The host factor required for RNA phage Qbeta RNA replication in vitro can also be obtained from poly(A)-cellulose, and chromatography of extracts of phage Qbeta-infected E. coli on RNA-cellulose columns results in very rapid isolation of the Qbeta replicase enzyme. Homopolymer RNA-cellulose chromatography thus appears to be a simple, general technique, useful for the efficient isolation of a variety of RNA-binding proteins.

Mutagenic DNA polymerase in human leukemic cells.

Evidence is presented that DNA polymerases from human leukemic cells are mutagenic. Nucleic acid-free extracts of acute lymphoblastic leukemic cells polymerized about 10-times more dCTP using poly(dA-dT).poly(dA-dT) as a template than did extracts from normal lymphocytes. Mutagenic DNA polymerases could perhaps play an important role in tumor progression.