The kinetics and mechanisms of the oxidation of Cr(III) in soil contaminated by unsaturated oils were investigated. Batch experiments were performed with unsaturated oils, namely, fish oil, ...hydrogenated lard oil, rapeseed oil, and caster oil. Impacts of environmental parameters, including temperature, soil pH, UV irradiation, oil content, and soil moisture content were examined. Results showed that oxidation of Cr(III) in oil-treated soils was accompanied by the formation of Cr(VI), which first increased and then decreased. Changes in the peroxide values of oils and the production of hexanal in the soil indicated that hydroperoxide was closely related to the formation of Cr(VI). tert-Butylhydroperoxide, as a model molecule of hydroperoxide, significantly enhanced the oxidation of Cr(III) in water. This result further showed that hydroperoxides were responsible for the oxidation of Cr(III). Native soil substances, such as organic matter, Fe(II), and microbes, and the decomposition products of hydroperoxides, such as aldehydes, could reduce Cr(VI). The change in Cr(VI) content in the soil resulted from the competition between the oxidation of Cr(III) and the reduction of Cr(VI). High temperature, high soil pH, UV irradiation, and low soil moisture content could facilitate the oxidation of Cr(III), which is of environmental significance.
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•Cr(III) can be significantly oxidized to Cr(VI) in soils contaminated by unsaturated oil.•Hydroperoxides, which are the primary products of oil autoxidation, mainly caused the oxidation of Cr(III).•Native reducing substances in the soil and aldehydes decomposed from hydroperoxides led to the decrease in Cr(VI).•High temperature, high soil pH, and UV irradiation facilitated the oxidation of Cr(III) in the soils contaminated by oil.
Protease-assisted soaking has received increasing attention in recent years. However, few reports have elaborated on the effect of bactericides, which are used to protect raw hides from microbial ...damage in the soaking process, on the performance of protease-assisted soaking. Here we investigate the effects of three bactericides, namely, 2-methyl-4-isothiazolin-3-one (MIT), sodium propyl 4-hydroxybenzoate (SPHB) and cetyl trimethyl ammonium bromide (CTAB), on the catalytic activity of protease. MIT and SPHB have little effect on the proteolytic activity, whilst CTAB has a negative effect. Fluorescence spectroscopy, synchronous fluorescence spectroscopy, molecular docking and molecular dynamics simulation were used to analyse the bactericide–protease interaction. The data reveal that MIT and SPHB are bound to the non-catalytic sites of protease, whilst CTAB affects the catalytic triad of protease. Furthermore, the protease and bactericides were used alone, simultaneously and sequentially in the soaking process, and their soaking performances were evaluated. The evaluation shows that the use of protease increases the microorganisms in the soaking float, and MIT exhibits the best bactericidal effect. The simultaneous use of protease and MIT effectively inhibits bacteria and scarcely affects the removal of unstructured proteins from hides and the attack on epidermis by protease. These findings contribute to a better understanding of the scientific use of protease with other auxiliaries in soaking.
Graphical Abstract
Storage is essential in improving the quality of strong‐flavor baijiu (SFB). Here, we investigated the release behaviors of metals from containers into SFB and their effects on the evolution of aroma ...compounds during storage. Twenty‐six metals were identified in SFB samples. The concentrations of Na, K, Ca, Mg, Al, and Fe obviously increased after storing in pottery jar, whereas those of Fe and Cu greatly increased after storing in stainless‐steel vessel. The volatility of most esters, alcohols, ketone, furan, and aldehyde decreased, whereas that of most acids increased after adding the metal ions into fresh SFB. The fluorescence intensity of SFB decreased with increased aging time in pottery jar, whereas the fluorescence intensity of acids was quenched with adding Fe3+ and Cu2+. All these results suggested that some metals released from containers had binding affinities with acids, thereby reducing SFB organoleptic stimulation by forming metal‐aroma compound complexes during storage.
Some metals were dissolved out from containers such as pottery jar and stainless‐steel vessel into strong‐flavor baijiu (SFB) during storage. These metals had binding affinities with aroma compounds, thereby reducing SFB organoleptic stimulation by forming metal‐aroma compound complexes during storage.
This work was conducted to study the effect of soil pH (4.0, 6.0, and 8.0) on the transport, fractionation, and oxidation of trivalent chromium Cr(III). Variation in pH altered soil chemical and ...mineralogical properties such as zeta potential, cation exchange capacity and redox potential of natural soil. Breakthrough curves and batch sorption experiments coupled with fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses demonstrated that the easy mobility of Cr(III) in pH 4.0 soil was dominated by the limited coordination effect. The high retention of Cr(III) in pH 8.0 soil was mainly ascribed to the hydrolysis. Incubation experiments indicated that the proportions of Cr in exchangeable fraction decreased with increasing of soil pH and incubation time, and kinetics analysis revealed that the time dependent transformation was controlled by mass transfer and chemical processes (e.g., hydrolysis, ion association). The XPS confirmed the oxidation of Cr(III) in pH 8.0 soil during the incubation period. Furthermore, the content of toxic hexavalent chromium Cr(VI) was positively associated with time and initial concentration of Cr(III) released. These results revealed the hazardousness of Cr(III) in soil contaminated simultaneously by inorganic acid and alkali.
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•Retardation ability of Cr(III) was low in acidity soil.•Proportions of exchangeable Cr were high in acidity soil, and decreased with prolonged incubation time in all soil types.•Potential oxidation of Cr(III) to toxic Cr(VI) occurred in the alkaline soil with prolonged incubation time.•These help to assess the hazardousness of Cr(III) in soils contaminated simultaneously by inorganic acid and alkali.
Conventional methods of enhancing the creep resistance of polyvinyl chloride (PVC) often compromise its resilience. This study proposes a novel strategy to achieve a balance between creep resistance ...and resilience in PVC-matrix composites by incorporating epoxidised soybean oil-modified collagen fibres (MCFs). A comparative analysis of creep and recovery behaviour was conducted among MCF/PVC, pure PVC, and other conventional modified systems. Results revealed that MCF/PVC exhibited a lower total creep strain (12.82%) than pure PVC and a higher recoverable deformation (10.80%) than the other conventional modified systems. Moreover, MCF/PVC had the longest predicted creep lifetime among all the modification systems, which was 103 times longer than that of pure PVC. These improvements were attributed to the natural multidirectional and hierarchical structure of MCF, which hindered the movement of PVC chains and provided sufficient gaps for recoverable deformation. This work provides a new perspective on developing resilient creep-resistant modifications of polymers by leveraging the structural advantages of natural products.
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•The balance between creep resistance and resilience in composites was achieved.•Collagen fibres (CFs) with a multidirectional and hierarchical structure were prepared.•MCF/PVC was successfully prepared by blending PVC with modified CF (MCF).•The mechanism of resilient creep-resistant modification of PVC was revealed.•MCF/PVC exhibited good comprehensive performance and promising application prospects.
The Cr(III)-organic complexes formed between Cr(III) and multifunctional group ligands, such as polyacrylate, are highly water soluble and difficult to be removed from wastewater by common ...treatments. A novel strategy for efficiently removing Cr(III)-poly (acrylic acid) complex (Cr(III)-PAA) from wastewater without introducing secondary pollution is proposed using a coprecipitation method with polyvalent metal ions. Al(III), Fe(III), Zr(IV), and Ti(IV) were combined with the carboxyl of Cr(III)-PAA to decrease hydrophilia and achieve fast and efficient coprecipitation. Cr(III)-PAA was efficiently removed from wastewater by using these polyvalent metal ions, especially at low pH, where the ions exist as monomer. The residual concentration of Cr(III) in treated wastewater under the optimized experimental condition was less than 1.0 mg/L. No Cr(VI) and negligible amount of polyvalent metal ions were detected in the treated wastewater, indicating that almost all of the ions coprecipitated with Cr(III)-PAA. No secondary pollution also occurred. The high reactivity between the polyvalent metal ions and Cr(III)-PAA and the sharp decrease in the hydrophilia of the complex contributed to its highly efficient removal from wastewater. Actual tannery wastewater containing Cr(III)-organic complexes with high solubility and stability was treated through coprecipitation with Al(III). A high Cr(III) removal efficiency of 99.0% was obtained. This work provides new insights into the removal of soluble Cr(III)-organic complexes from wastewater by using an environment-friendly and cost-effective method.
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•Coprecipitation was first used to remove Cr(III)-organic complexes from wastewater.•Highly efficient removal of Cr(III)-organic complexes was obtained.•No Cr(VI) and negligible polyvalent metal ions were detected in wastewater.•Blocking the hydrophilic groups of Cr(III)-organic complexes led to rapid removal.•This work provides new insights into the treatment of Cr(III)-organic complexes.
•Structure-property relation of oxidized sodium alginate (OSA) was investigated.•Molecular weight of OSA is a key factor in improving properties of collagen fiber.•Effect of aldehyde group content ...was less obvious than that of molecular weight.
A series of periodate oxidized sodium alginate (OSA) were prepared as green polysaccharide-based crosslinkers. The molecular weight of OSA decreased, while their aldehyde group content increased with increasing dosage of sodium periodate. A typical OSA was further fractionated to four fractions by ethanol with a narrower molecular weight distribution. Then the crosslinking performances of OSAs/fractions on collagen fiber (CF) were investigated. DSC and SEM analyses showed that the thermal stability and dispersion degree of crosslinked CF was considerably enhanced with decreasing molecular weight of OSA. The effect of aldehyde group content of OSA on its crosslinking performance was less obvious than that of molecular weight, probably because the aldehyde group content in each OSA sample was higher than the amino group content of CF involved in the crosslinking reaction. In general, molecular weight of OSA plays a decisive role in improving properties of the crosslinked CF.
Feather waste is produced in millions of tons globally every year, resulting in a waste of biomass resources and even environmental pollution. A sustainable strategy for utilizing feather waste was ...proposed by preparing a clean deliming agent for ammonia-nitrogen (NH3–N) reduction in leather manufacture and biological treatment efficiency improvement of tannery wastewater. Briefly, chicken feather wastes were deeply hydrolyzed with sulfuric acid, and the optimized keratin hydrolysate (KHopt) that contained 53.6% crude protein and 41.2% amino acids, such as glutamic acid, serine, proline, leucine, phenylalanine, glycine, valine, and arginine, was obtained and used to delime limed cattle hides. The appropriate ratio of amino acids in KHopt gave KHopt a great pH-buffering capacity and maintained a stable float pH of approximately 9 throughout the deliming process. The isoelectric points of KHopt (3.8) and the limed hide (6.3) were both lower than the float pH, thereby bringing about an electrostatic repulsion between the KHopt and the hide surface, which is helpful for KHopt to penetrate and deswell the limed hide rapidly. Moreover, the KHopt deliming effectively removed calcium from the limed hide and achieved leather comparable to conventional leather for commercial applications. KHopt reduced the NH3–N concentrations of deliming effluent and tannery wastewater by 91.1% and 80.6%, respectively, compared with the conventional deliming agent (ammonium sulfate), and dramatically increased the biological treatment efficiency of tannery wastewater. The results showed that efficient and high-value use of feather waste was made by preparing KHopt for sustainable leather manufacturing.
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•A novel resource utilization of feather waste was developed.•Keratin hydrolysate (KH) was obtained by deeply hydrolyzing feather waste.•KH had efficient and environment-friendly leather deliming performance.•KH deliming greatly reduced ammonia-nitrogen pollution in tannery wastewater.•KH deliming improved the biological treatment efficiency of tannery wastewater.
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•Ester alkyl-oxygen protonation has lower Ea than acid hydroxyl-oxygen protonation.•DFT results explained why acids increased and esters decreased during SFB storage.•Electrostatic ...interaction was a major contributor to the flavor compound changes.•Ethanol–water system containing acids had more H-bonds than that containing esters.•MD simulation results proved that the acids can strengthen associative structures.
The aging procedure/storage is essential to enhance the organoleptic quality of strong flavor baijiu (SFB). How the storage affects flavor changes in SFB, that is, the aging mechanisms remains unclear. Herein, the physical and chemical effects on the main flavor compounds of SFB during storage were investigated using the density functional theory (DFT) and molecular dynamics (MD) simulation. DFT calculation results showed that the activation energy of ester alkyl-oxygen protonation was lower than that of acid hydroxyl-oxygen protonation, which explained the reason why the concentrations of acids increased and those of esters decreased during SFB storage. MD simulation results showed that electrostatic interaction was a major contributor to SFB and that the ethanol–water system containing acids had a stronger electrostatic energy and more hydrogen bonds than the ethanol–water system containing esters. These findings revealed that acids are prone to generating and strengthening associative structures in SFB during storage.
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