Insoluble Precipitate Research Articles

New insight into effects of waste scrap iron on sludge anaerobic digestion: Performances, microbial community, and potential metabolic functions

The low sludge degradation efficiency and hydrogen sulfide (H2S) generation impair the development of sludge anaerobic digestion. This study explored the effects of waste scrap iron (WSI) addition on methane (CH4) production and H2S control in sludge anaerobic digestion. The maximum cumulative CH4 yield of 205.02 mL/g VSS was obtained at the WSI dosage of 0.7 g/g VSS, which increased by 21.34 % compared to that of control without WSI addition. The increase in CH4 yield was attributed to the enhancement of sludge degradation and soluble organic conversion. Meanwhile, the cumulative H2S yield reduced by 62.00 % compared to that of control. The pH value and content of insoluble sulfide precipitate increased with the increase in WSI dosage, which were two main reasons for H2S control. Microbial community results indicated that relative abundance of unclassified_f_Clostridiaceae_1, Bacteroides, vadinBC27_wastewater-sludge_group, Clostridium_sensu-stricto-1, Macellibacteroides, and hydrogenotrophic methanogens increased with WSI addition, meaning that WSI addition promoted syntrophic interaction between key bacteria and hydrogenotrophic methanogens. Gene prediction analysis demonstrated that WSI addition promoted microbial proliferation and respiration, carbohydrate and amino acid metabolism, and activity of butyrate kinase, acetate kinase, pyruvate ferredoxin oxidoreductase, and coenzyme F420 hydrogenase. In view of the enhancement of ABC transporters, lipopolysaccharide biosynthesis, quorum sensing, two-component systems, and ribosome metabolic pathway, it could be considered that WSI addition promoted information recognition and substance exchange among microorganisms, increasing microbial metabolic activity of anaerobic system.

Formation of Hydrophobic-Hydrophilic Associates in the N-Vinylpyrrolidone and Vinyl Propyl Ether Copolymer Aqueous Solutions.

Utilizing turbidimetry data, an examination is conducted on the behavior of solutions containing N-vinylpyrrolidone and vinyl propyl ether copolymer within a temperature range coinciding with the occurrence of a phase transition. The investigation reveals that within specific conditions prevailing in this domain, the emergence of entities denoted as hydrophobic-hydrophilic associates is conceivable. These entities are characterized by the presence of a relatively dense core, upheld by hydrophobic interplays, and they are proficient in effectively dispersing irradiation within the optical spectrum. Encircling this core is a hydrophilic periphery that impedes the formation of insoluble precipitates. The development of such associates transpires when hydrophobic interactions have attained a discernible prominence, although they remain inadequate to counteract the forces that drive the expansion of macromolecular coils. Under these circumstances, the energetically favored course of action entails the constitution of a core for the aforementioned associates, involving discrete segments from diverse macromolecules. Notably, the introduction of an additional constituent (ethanol) to the solution, which selectively mitigates hydrophobic interactions, serves to stabilize the hydrophobic-hydrophilic associations.

Unraveling the potential health impact of the interactions between pea hydrolysates/peptides originating under gastric digestion and bile salts

Bile salts (BS) are biological surfactants that have important physiological functions mainly by participating in lipid digestion and intervening in the transport, absorption, and excretion of hydrophobic products. Bile salts have been shown to interact with the products of protein hydrolysis, being this interaction a key point to modulate several physiological processes.The type and size of peptides, released at different times of gastric digestion, could have different implications in these physiological processes modulated by the BS. In the present study we focused on understanding how the interactions of hydrolysates/peptides from native or commercial pea protein isolates with BS (formation of insoluble complexes or the modification of the BS micellar solubilization of poorly soluble molecules) evolve according to their residence time in a static gastric digestion model. The different residence times (10–60 min) would simulate different emptying points in which the partially hydrolyzed pea proteins by pepsin in the stomach are flushed into the duodenum and come into contact with the BS.It is observed that the longer residence times in the stomach the degree of hydrolysis of the pea isolates is greater, producing an increase in the soluble fraction. Both isolates showed a slight tendency to bind BS and form insoluble precipitates. The interaction of the soluble fraction of pea protein hydrolysates with the BS micelles, acted synergistically, increasing the solubilization capacity of oleic acid, taken as a model molecule.Likewise, it is shown that the structural changes of pea proteins due to processing have a profound influence on the interaction with BS and potentially affect the physiological reactions that they modulate.

Combination and precipitation mechanism of soy protein and tea polyphenols

Non-covalent interactions of plant proteins and polyphenols is often occurred in food production and processing. However, the combination of the two may form a precipitate to reduce the aesthetic value and taste. In this study, we prepared different proportions of soy protein isolate (SPI) and catechin/epigallocatechin-3-gallate (EGCG) non-covalent complexes. The structural and conformational changes of the complex in the non-covalent interaction system were explored by multi-spectral technology, and the transition mechanism from the solution-state to the precipitation-state was analyzed. As a “bridge”, polyphenols made more SPI cross-linked and aggregate, and reduce hydrophobicity. The enhancement of resonance Rayleigh scattering further confirmed the formation of macromolecular particles. SPI mainly combined with catechin/EGCG through hydrogen bonds, and more benzene rings and phenol hydroxyl structure of EGCG were conducive to the formation of a more stable complex with protein. In addition, the increase of polyphenol concentration promoted the conjugation effect (hydrophobic interaction and electrostatic interaction) with protein, resulting in insoluble high molecular weight aggregate precipitation.

Simplified silicon recovery from photovoltaic waste enables high performance, sustainable lithium-ion batteries

Conventional recycling methods to separate pure silicon from photovoltaic cells rely on complete dissolution of metals like silver and aluminium and the recovery of insoluble silicon by employing multiple leaching reagents. A common approach that eschews hydrofluoric acid (HF) treatment is the double reagent approach which utilizes nitric acid (HNO3) and potassium hydroxide (KOH) to separate the metals from silicon cell. However, the double reagent approach is unable to remove the anti-reflective coating and use of KOH leads to formation of insoluble precipitates, in turn affecting the purity of recovered silicon. Herein, we report a single reagent approach for a streamlined process for recovery of high purity silicon with unmatched recovery yield. Phosphoric acid, (H3PO4) identified as a reagent for this approach, directly targets the anti-reflective coating and separates the Ag and Al present on the Si wafer surfaces. This approach led to an impressive recovery rate of 98.9% with a high purity of 99.2%, as determined by X-ray fluorescence and Inductively-coupled plasma optical emission spectroscopy. Such high-purity of recovered silicon enables upcycling into anodes for lithium-ion battery, with the battery performance comparable to as-purchased silicon. Such recovered silicon lithium-ion battery anodes demonstrated a high specific capacity of 1086.6 mAh g−1 (62.3% of its initial specific capacity), even after 500 cycles at a high charging rate of 1.0C while maintaining high coulombic efficiency (>99%).

Tannic acid-based sustained-release system for protein drugs

In recent years, protein drug development has gained momentum, and simple and facile controlled-release systems without loss of activity are required. Herein, we developed a sustained-release system for protein drugs by exploiting the “astringency” mechanism, namely insoluble precipitate formation by interacting with tannic acid. Tannic acid formed insoluble precipitates with various protein drugs, such as nisin, insulin, lysozyme, ovalbumin, hyaluronidase, and human immunoglobulin G, through hydrophobic interactions and hydrogen bonds. The lysozyme/tannic acid complex retained in vitro lytic activity. Precipitates of the insulin/tannic acid complex prolonged hypoglycemic effects without loss of activity after subcutaneous administration. The ovalbumin/tannic acid complex enhanced anti-ovalbumin antibody production induced by ovalbumin, which may be attributed to its sustained-release profile. Accordingly, tannic acid is useful as a simple and user-friendly drug delivery system for protein drugs.

Separation of polysaccharide and protein by ionic liquid-based extraction techniques

Biopolymers are natural macromolecules obtained from animal, plant and microbial sources, with the potential to be used in a wide range of applications. A key process step, which is still underdeveloped, is the downstream processing. In this work, water immiscible and water miscible ionic liquids (ILs) were investigated regarding their ability to fractionate a mixture of polysaccharide and proteins. Alginate and bovine serum albumin (BSA) were used as model compounds to mimic natural polymer crude extract. Phosphonium ILs composed of different anions (bromide, dicyanamide and phosphinate) were used as water immiscible ILs while imidazolium ILs, combined with phosphate salts to form biphasic system, were selected as water miscible ILs. In water immiscible IL systems, the partitioning behavior of biopolymers depended on IL's anions and there was formation of insoluble precipitate. The insolubility of precipitate in diverse aqueous and organic solvents hindered the processibility of water immiscible phosphonium IL for fractionation of biopolymers. The partitioning of biopolymers in water miscible ILs systems also depended on the IL's anion, as well the concentration of IL. Separation of alginate (yield = 90% and purity = 99%) from BSA (yield = 89% and purity = 99%) was best achieved by the [C4mim]Cl-based extraction system. After fractionation, regeneration of IL and salt used was carried out by ultrafiltration, with recovery yields up to 100%. The high extraction yields and recyclability of phase-forming compounds confirm the potential of water miscible ILs systems to fractionate polysaccharide and protein.

Anti-precipitation molecular metal chalcogenide complexes modification for efficient direct alkaline seawater splitting at the large current density

Hydrogen production from direct alkaline seawater electrolysis at large current density is a key technology for marine energy projects. However, catalyst poisoning due to insoluble precipitation is a key issue that should be addressed. In this work, we used Pt/CNT electrocatalysts modified with molecular metal chalcogenide complexes. During the direct electrolysis of alkaline seawater, the modified Pt/CNT electrocatalyst can effectively reduce the formation of insoluble precipitates on the cathode surface, which is conducive to the stable operation of the hydrogen evolution reaction. Theoretical simulations and in situ experiments both demonstrate that the modified Pt/CNT was affected by the coordination to form coordination compounds, which effectively prevented the formation of insoluble precipitates. The alkaline anion exchange membrane (AEM) electrolyzer with a modified Pt/CNT electrocatalyst exhibited an industrially required current density of 1.0 A cm−2 at 2.0 V and 60 °C, achieving long-term stability in excess of 600 h.

Structure of aqueous solutions of lignin treated by sub- and supercritical water: Experiment and simulation

Hydrolysis lignin was treated with sub- and supercritical water (523–723 K and 10 MPa). As a result, depolymerization of lignin to mono- and oligolignols occurs. SEC data show water-soluble particles up to 4 nm after treatment of lignin by subcritical water (523 K and 10 MPa). After further treatment with supercritical water (723 K and 10 MPa), the concentration of water-soluble particles decreases by 2–3 times; and their size increased up to 10 nm. Molecular dynamics simulation of a model lignin particle in aqueous medium under standard (298 K, ρ = 0.997 g/cm3) and supercritical (673 K, ρ = 0.133 g/cm3) conditions was performed. Based on modeling, lignol monomers surrounded by solvate shells and water-soluble particles of lignin oligomers with a gel-like structure were identified as the structural units of the solutions. Under supercritical conditions, it causes the different ways of transformation of the system: further destruction of individual lignol molecules or condensation of lignols with the formation of insoluble precipitate.

Chemical composition, particle size, and molecular weight distributions of chemically degraded guar gum solutions

AbstractChemical degradation of guar gum solutions via the addition of a strong oxidant is a common process step in hydraulic fracturing. Unfortunately, this degradation step leads to the formation of an insoluble precipitate which clogs the porous rock formation, reducing efficiency, reducing oil recovery potential, and increasing energy costs. The chemical composition, particle size, and molecular weight distributions of the oxidatively degraded guar (“broken guar”) are largely unknown, making it difficult to develop mitigation strategies. In this work, broken guar gum solutions are systematically analyzed to understand the origin of the observed residue. Our results indicate that cellulose fibers and proteins, rather than galactomannan oligomers, are the two major components (>50%) of the solid residue (the water‐insoluble fraction of broken guar). This finding suggests that removal of the cellulose fiber and proteins from the guar source material may be a potential residue mitigation strategy. Separately, we provide evidence for a potential second mitigation strategy employing chemical additives to reduce aggregation of the insoluble species, effectively reducing their potential to cause formation damage.

Multiple approaches to characterize and visualize the chemical composition of Sijunzi Decoction comprehensively.

Sijunzi Decoction is composed of Ginseng Radix et Rhizoma, Atractylodes Macrocephalae Rhizoma, Poria, and Glycyrrhizae Radix Et Rhizoma Praeparata Cum Melle, and it is a classic formula for treating spleen deficiency syndrome in Chinese medicine. Clarifying the active substances is an effective way to develop Traditional Chinese medicine and innovative medicines. Carbohydrates, proteins, amino acids, saponins, flavonoids, phenolic acids, and inorganic elements in the decoction were analyzed by multiple approaches. A molecular network was also used for visualizing the ingredients in Sijunzi Decoction, and representative components were also quantified. The detected components accounted for 74.544% of the Sijunzi Decoction freeze-dried powder, including 41.751% crude polysaccharides, 17.826% sugars (degree of polymerization 1-2), 8.181% total saponins, 2.427% insoluble precipitates, 2.154% free amino acids, 1.177% total flavonoids, 0.546% total phenolic acids, and 0.483% inorganic elements. Molecular network and quantitative analysis used to characterize the chemical composition of Sijunzi Decoction. The present study systematically characterized the constituents of Sijunzi Decoction, revealed the composition ratio of each type of constituent, and provided a reference for study on the substance basis of other Chinese medicine.

Matrix is everywhere: extracellular DNA is a link between biofilm and mineralization in Bacillus cereus planktonic lifestyle

To date, the mechanisms of biomineralization induced by bacterial cells in the context of biofilm formation remain the subject of intensive studies. In this study, we analyzed the influence of the medium components on the induction of CaCO3 precipitation by the Bacillus cereus cells and composition of the extracellular matrix (ECM) formed in the submerged culture. While the accumulation of extracellular polysaccharides and amyloids appeared to be independent of the presence of calcium and urea during the growth, the accumulation of extracellular DNA (eDNA), as well as precipitation of calcium carbonate, required the presence of both ingredients in the medium. Removal of eDNA, which was sensitive to treatment by DNase, did not affect other matrix components but resulted in disruption of cell network formation and a sixfold decrease in the precipitate yield. An experiment with a cell-free system confirmed the acceleration of mineral formation after the addition of exogenous salmon sperm DNA. The observed pathway for the formation of CaCO3 minerals in B. cereus planktonic culture included a production of exopolysaccharides and negatively charged eDNA lattice promoting local Ca2+ supersaturation, which, together with an increase in the concentration of carbonate ions due to pH rise, resulted in the formation of an insoluble precipitate of calcium carbonate. Precipitation of amorphous CaCO3 on eDNA matrix was followed by crystal formation via the ACC-vaterite-calcite/aragonite pathway and further formation of larger mineral aggregates in complex with extracellular polymeric substances. Taken together, our data showed that DNA in extracellular matrix is an essential factor for triggering the biomineralization in B. cereus planktonic culture.

Tailoring enzymatic loading capacity on CdS nanorods@ZnIn2S4 nanosheets 1D/2D heterojunctions: Toward ultrasensitive photoelectrochemical bioassay of tobramycin

Despite advances in the development of photoelectrochemical (PEC) sensor, modulating the PEC response of assembled heterostructure interface is still a great challenge. Here, an ultrasensitive PEC aptasensor for tobramycin (TOB) assay was conducted based on one-dimensional/two-dimensional CdS nanorods@ZnIn2S4 nanosheets (1D/2D CdS NRs@ZnIn2S4 NSs) heterojunctions by tailoring enzymatic loading capacity. Firstly, alkaline phosphatase modified TOB aptamer (ALP-Apt) was linked via specific base complementary pairing, and insoluble precipitations were then produced through the ALP-triggered catalytic reaction with the aid of Ag+, which prevented the charge transfer and resulted in the decrement of photocurrent. In the presence of TOB, partial ALP-Apt detached from the electrode surface due to the strong affinity between TOB and its aptamer, leading to a reduction in the amount of ALP and insoluble precipitate, in turn the PEC response partially recovered. The photocurrents exhibited a wider linear range towards the TOB concentration of 1.0–5.0 × 104 pg mL−1, with a low detection limit of 0.96 pg mL−1. The constructed PEC aptasensor gained satisfactory results for TOB assay in milk samples as well, which also offered significant promise for other pollutants in environmental analysis.

Wire electrochemical finishing of wire electrical discharge machined surface of highly alloyed materials with insoluble precipitates

Wire electrochemical machining (WECM) using bipolar pulse current with scanning wire electrode can be effectively applied to mirror-finish the wire electrical discharge machined surfaces of stainless steel. However, highly alloyed materials with insoluble precipitates such as cold tool steel and nickel-based superalloy are hard to finish, due to their non-uniform phase. This study aimed to finish these highly alloyed materials, by optimizing the duty factor. The machined depth, surface roughness, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) observation, bending strength, and edge roundness of WECMed surface of these materials were investigated. As a result, the duty ratio of 30% for cold tool steel and 40% for Inconel 718 were most effective to smoothen the surface uniformly. Furthermore, the shape accuracy of WECMed surfaces of small holes and thicker workpieces was also reviewed. The inner surface of small holes made in stainless steel with 0.5 mm in diameter was finished to surface roughness of Ra 0.088 µm, which is almost the same roughness as obtained with plane surfaces. Even a workpiece of 120 mm thickness was finished successfully with a straightness smaller than 2 µm.

Role of Smart-Release Pigments in Preventing Corrosion Driven Cathodic Disbondment of Organically Coated Hot Dip Galvanised Steel

The role of smart-release corrosion inhibitive pigments in preventing cathodic delamination of organically coated hot-dip galvanized steel (HDG) is investigated. The pigments consisted of hydrotalcite (HT) exchanged with a range of inorganic and organic anionic species and were dispersed in a model PVB coating. A scanning Kelvin probe (SKP) technique was used to determine cathodic delamination rates, and the inhibition efficiencies obtained for inorganic ions increased in the order < < < < < < The inhibition efficiencies for organic-based pigments increased in the order triazole <phenylphosphonate <trans-cinnamate <benzoate <salicylate <benzotriazole. The inhibition efficiency afforded by the best performing organic inhibitor, benzotriazole (BTA), rivalled that of HT containing stored chromate anions. Findings are consistent with HT-BTA acting to sequester anions from the underfilm electrolyte, releasing BTA− which subsequently strongly adsorbs on the underfilm metal surface but can also form an insoluble Zn-BTA precipitate at the coating-defect boundary.

A digital multimeter-based portable photoelectrochemical immunoassay for the detection of cardiac troponin I with enzymatic biocatalytic precipitation.

Early diagnosis of acute myocardial infarction (AMI) can significantly reduce mortality, which can be achieved by the highly sensitive detection of AMI-specific cardiac troponin I (cTnI) biomarkers. Herein a highly sensitive and portable photoelectrochemical (PEC) immunoassay for the detection of cTnI was innovatively fabricated based on an efficient photocurrent response of Cu2O coupling with a split-type enzymatic biocatalytic precipitation reaction with a digital multimeter readout. Initially, Cu2O cubic nanomaterials with a good photocurrent response were obtained by facile green room temperature synthesis and dropped on fluorine-doped tin oxide (FTO) plates as photoactive materials (Cu2O/FTO). In the presence of target cTnI, horseradish peroxidase (HRP) on the detection antibody catalyzes the substrate 4-chloro1-naphthol (4-CN) to produce insoluble precipitates of benzo-4-chlorohexadienone (4-CD) on Cu2O/FTO with the assistance of H2O2, resulting in a decrease in the photocurrent of the Cu2O/FTO electrode. To make the whole inspection process more concise and efficient, we used a flashlight and a digital multimeter as the excitation light source and reading device for the PEC sensing system, respectively. Under the optimal conditions of immunoreaction time, pH, and loading, the photocurrent of Cu2O/FTO decreased with increasing target cTnI concentration with a limit of detection (LOD) of 4.7 pg mL-1 in the operating range of 0.01-10 ng mL-1. It is of interest that the developed portable PEC immunoassay is also capable of detecting cTnI in human serum samples with acceptable accuracy compared to the reference cTnI enzyme-linked immunosorbent assay (ELISA) method while maintaining portability and sensitivity.

Selectivity of Electrochemical Ion Insertion into Manganese Dioxide Polymorphs

The ion insertion redox chemistry of manganese dioxide has diverse applications in energy storage, catalysis, and chemical separations. Unique properties derive from the assembly of Mn-O octahedra into polymorphic structures that can host protons and nonprotonic cations in interstitial sites. Despite many reports on individual ion-polymorph couples, much less is known about the selectivity of electrochemical ion insertion in MnO2. In this work, we use density functional theory to holistically compare the electrochemistry of AxMnO2 (where A = H+, Li+, Na+, K+, Mg2+, Ca2+, Zn2+, Al3+) in aqueous and nonaqueous electrolytes. We develop an efficient computational scheme demonstrating that Hubbard-U correction has a greater impact on calculating accurate redox energetics than choice of exchange-correlation functional. Using PBE+U, we find that for nonprotonic cations, ion selectivity depends on the oxygen coordination environments inside a polymorph. When H+ is present, however, the driving force to form hydroxyl bonds is usually stronger. In aqueous electrolytes, only three ion-polymorph pairs are thermodynamically stable within water's voltage stability window (Na+ and K+ in α-MnO2, and Li+ in λ-MnO2), with all other ion insertion being metastable. We find Al3+ may insert into the δ, R, and λ polymorphs across the full 2-electron redox of MnO2 at high voltage; however, electrolytes for multivalent ions must be designed to impede the formation of insoluble precipitates and facilitate cation desolvation. We also show that small ions coinsert with water in α-MnO2 to achieve greater coordination by oxygen, while solvation energies and kinetic effects dictate water coinsertion in δ-MnO2. Taken together, these findings explain reports of mixed ion insertion mechanisms in aqueous electrolytes and highlight promising design strategies for safe, high energy density electrochemical energy storage, desalination batteries, and electrocatalysts.

Nitrogen Reduction to Ammonia by a Phosphorus-Nitrogen PN 3 P-Mo(V) Nitride Complex: Significant Enhancement via Ligand Postmodification

Nitrogen Reduction to Ammonia by a Phosphorus-Nitrogen PN ³ P-Mo(V) Nitride Complex: Significant Enhancement via Ligand Postmodification

In-situ passivation mechanism of modified silicate composite biochar on soil cadmium

Original biochar has the characteristic of fragile texture, which is easy to cause difficulties in application and environmental pollution during soil remediation. Moreover, it is difficult to be separated from the soil, the heavy metals passivated in-situ have the risk of being reactivated when the environment changes. Through the steps of "magnetization" and "granulation", modified silicate composite biochar was prepared and the fixation mechanism of the materials on cadmium was also explored. The results showed that: (1) The dry weight of wheat in the blank was only 0.062 g, as well as the dry weights treated by biochars were more than 0.117 g. The content of cadmium in wheat cultured with KM6 was 0.22 μg, only 39.64 % of the blank. (2) The biochar addition increased the soil’s pH. The pH value of soil treated by silicate composite biochar reached 7.64–7.94, which promoted the transformation of cadmium ions to insoluble precipitation. (3) The content of available cadmium in untreated soil was 54.6 %, while which decreased to 22.9 %− 29.9 % after adding silicate composite biochar. (4) Magnetic biochar contained the special iron-containing structures and iron oxides, which can react with cadmium to form stable complexes (such as (FeO)2Cd and (Fe-R-O)2Cd) to promote the removal of heavy metals.

Catalytic selective separation of chloride ions from acidic wastewater

A new two-step technique was developed for selective separation of chloride ions from acidic aqueous solutions. The process is operated at ambient temperature and pressure, and it is powered by H2 gas and atmospheric oxygen. The Pt-Ag-AC catalyst comprises activated carbon (AC) loaded with platinum (Pt) nano size crystals and metallic silver (Ag) particles. The aeration of acidic chloride solution results in the oxidation of Ag0 to Ag+, which in turn reacts with chloride ions to form an insoluble AgCl precipitate on the catalyst. The regeneration of the Pt-AgCl-AC is performed by hydrogenation, that leads to reduction of AgCl into Ag0, followed by the release of Cl− ions. The process was studied in a batch mode system using acidic NaCl-H2SO4 solutions (500 mgCl/L, [H2SO4]0 = 0.5 M) and Pt-Ag-AC made of granular activated charcoal. The carbon was loaded with 0.5 %Pt and 3.22, 6.25 or 9.09 % of metallic silver. A maximal chloride adsorption capacity of 16.31 mgCl/g was recorded. Full (100 %) separation of Cl− ions from NaCl solutions with [Cl−]0 = 200 mg/L and [H2SO4]0 = 0.5 M was demonstrated.