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To study the metal ion chelating agent (DL‐malic acid) inhibiting oxidation characteristics of residual coal in goaf, the microscopic thermal transformation characteristics of the treated coal samples were obtained using apparent morphology, infrared spectroscopy, free radical testing, and thermal analysis. The results demonstrate that after the addition of malic acid, the sphericity and roundness of the coal samples decrease, and the small fractured particles accumulate in the pores of the oxidized coal samples and, thereby, reduce the number of coal–oxygen contact sites. The addition of 10% malic acid promotes the conversion of functional groups (FG) and free radicals in pre‐oxidized coal, inhibits the catalytic effect of metal ions, generates more active sites, and increases the total heat release during the combustion process. There are strong endothermic points in the malic acid‐treated coal samples, and the free water evaporation blocked by small particles in the holes delays the initial heat release temperature of the coal samples. Pre‐oxidation can promote changes in the valence state of metal ions in coal, increase the adhesion between broken pre‐oxidized coal particles via malic acid chelation, and lose the catalytic effect of metal ions; this inhibits the process of oxidative re‐ignition of coal samples. [ABSTRACT FROM AUTHOR]

DL‐malic acid (DMA), as a recognized antioxidant inhibitor and chelating agent in the food and chemical industries, has good application prospects in coal fire prevention and control. This paper investigates the impact of a DMA solution on the surface properties and phase structure of coal through a range of analytical techniques, including electron microscope scanning, particle size analysis, and x‐ray diffraction. The thermal behavior characteristics of DMA‐treated coal were analyzed using thermogravimetric experiments. The results show that after adding malic acid, the particle size of coal sample is reduced, the sphericity and roundness are reduced, and the pore size is increased. The hydroxyapatite and calcite components in coal were dissolved and consumed, and the calcite components were gradually depleted with the increase of DMA concentration. The flocculent structure produced by the condensation of the crushing residue and broken small particles are attached to the internal pores of coal, which reduced the coal oxygen contact sites and increases the content of the sealed solution, resulting in the increase of the thermal characteristic temperature of the coal and the inhibition of the oxidation heat generation process. DMA has obvious inhibitory effect on fresh coal and oxidized coal, and the inhibitory effect is stronger on high‐temperature oxidized coal. Therefore, DMA can be effectively applied to the prevention and control of spontaneous combustion of residual coal in goaf. The research results provide a reference for the research of coal fire prevention technology and the preparation of environmentally friendly flame retardant materials. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of DL-malic acid supplementation in beef cattle rations containing high concentrated feed and dry forage (alfalfa hay and wheat straw) on fattening performance, carcass traits and rumen parameters. In present study, 47 male beef cattle (19 Simmental, 28 Limousine) at the age of 14-16 months were used. Cattle breeds were divided into two groups (0 and 30 g/day of DL-malic acid). In the present study, the differences in live weights, daily live weight gains and carcass weights of the control and DL-malic acid groups were found to be significant in Simmental breed (P<0.05), but insignificant in Limousine breed. The beef cattle body measurements (withers height, chest girth, rump height, body length) did not change with malic acid supplementation (P>0.05).The malic acid addition increased the molarities of acetic, butyric, propionic and total volatile fatty acids (TVFA) and acetic acid/ propionic acid ratio in the rumen fluid (P<0.05).The addition of malic acid had no significant effect on the number of ciliated protozoa (Entodinium, Diplodinium, Isotricha and Dasytricha) and total bacteria count in the rumen fluid (P>0.05). As a result, DL-malic acid supplementation to beef cattle ration varied with cattle breeds in terms of fattening performance, while such supplementations had positive effect on fattening in Simmental breed. Besides, the increase in TVFA and acetic, propionic and butyric acids, which are indicators of fiber and carbohydrate fermentation efficiency in the rumen, shows that malic acid has a positive effect on feed digestion in the rumen. [ABSTRACT FROM AUTHOR]

Lithium recovery is imperative to accommodate the increase in lithium demand. Salt lake brine contains a large amount of lithium and is one of the most important sources of lithium metal. In this study, Li2CO3, MnO2, and TiO2 particles were mixed, and the precursor of a manganese–titanium mixed ion sieve (M-T-LIS) was prepared by a high-temperature solid-phase method. M-T-LISs were obtained by DL-malic acid pickling. The adsorption experiment results noted single-layer chemical adsorption and maximum lithium adsorption of 32.32 mg/g. From the Brunauer–Emmett–Teller and scanning electron microscopy results, the M-T-LIS provided adsorption sites after DL-malic acid pickling. In addition, X-ray photoelectron spectroscopy and Fourier transform infrared results showed the ion exchange mechanism of the M-T-LIS adsorption. From the results of the Li+ desorption experiment and recoverability experiment, DL-malic acid was used to desorb Li+ from the M-T-LIS with a desorption rate of more than 90%. During the fifth cycle, the Li+ adsorption capacity of the M-T-LIS was more than 20 mg/g (25.90 mg/g), and the recovery efficiency was higher than 80% (81.42%). According to the selectivity experiment, the M-T-LIS had good selectivity for Li+ (adsorption capacity of 25.85 mg/g in the artificial salt lake brine), which indicates its good application potential. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are widely used as a power source for portable devices and electrical vehicles (EVs). After their useful life, they can provide a secondary source from which to obtain some materials which make them up, such as lithium and cobalt. However, the metallurgical route which will be used to recover them must be considered. Therefore, is crucial that many efforts to develop more environmentally favorable recovery processes be pursued. Due to this, the present work aimed to use 1.5 M DL-malic acid and compare it to 2 M sulfuric acid, employing heat pretreatment of 1 h and 3 h to remove the powder cathode binder polyvinylidene fluoride (PVDF); for all conditions, experiments were carried out with and without adding the oxidizing agent hydrogen peroxide. The PVDF temperature degradation occurred at 630 °C. The best yields occurred in the presence of H2O2 10% v/v and heat pretreatment. With sulfuric acid (1 h) it was possible to recover 33.49% Co and 4.63% Li, and (3 h) 36.36% Co and 4.64% Li. With DL-malic acid it was possible to recover (1 h) 29.78% Co and 3.44% Li, and (3 h) 32.73% Co and 3.99% Li. [ABSTRACT FROM AUTHOR]

Unsaturated polyesters are of interest to scientists due to the presence of modifiable functional groups such as double and triple bonds. Active sites in the unsaturated polyesters are special options for drug delivery and biomedical applications. Click reaction is an attractive way to transfer drugs using unsaturated polyesters. In this study, low molecular weight unsaturated aliphatic polyesters containing internal triple and double bonds based on DL-malic acid have been synthesized. Oligoesters with different degrees of unsaturation have been synthesized by condensation polymerization of DL-malic acid and 1,4-butanediol, cis-2-butene-1,4-diol, 2-butyne-1,4-diol, and diol mixtures. Polymerization was performed in the absence of catalyst and at low temperature (130 °C) by bulk polymerization. FT-IR, 1H-NMR, 13C-NMR, and GPC analyses were used for the characterization of the synthesized structures. The thermal properties of the oligoesters were investigated using DSC analysis. The glass transition temperatures for unsaturated oligoesters containing single, double, and triple bonds were obtained -32 °C, -24 °C, and -38 °C, respectively. 1H-NMR spectra showed that DL-malic acid self-condensation reaction in the presence of 2-butyne-1,4-diol, cis-2-butene-1,4-diol, and 1,4-butanediol monomers occurs ~ 8%, ~ 5%, and ~ 4%, respectively. The HOMO–LUMO gap of DL-malic acid (7.0145 eV) and 2-butyne-1,4-diol (6.3905 eV) were calculated using DFT computational method at the base level of B3LYP/6-311G + (d,p). Oligoester containing internal triple bonds (2-butyne-1,4-diol (ByD50)) were crosslinked with 1,4-diazidobutane, and reaction progress was followed by FT-IR analysis. Unlike isocyanate curing, azide curing is not sensitive to moisture. It is hoped that unsaturated polyesters containing triple bonds can be used in click reactions and polyester modification. Oligoester contains a triple bond (ByD50) suitable for drug delivery. These oligoesters have a controllable degree of crosslinking and can be used to modify an oligoester with a controllable degree. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are widely used as a power source for portable devices and electrical vehicles (EVs). After their useful life, they can provide a secondary source from which to obtain some materials which make them up, such as lithium and cobalt. However, the metallurgical route which will be used to recover them must be considered. Therefore, is crucial that many efforts to develop more environmentally favorable recovery processes be pursued. Due to this, the present work aimed to use 1.5 M DL-malic acid and compare it to 2 M sulfuric acid, employing heat pretreatment of 1 h and 3 h to remove the powder cathode binder polyvinylidene fluoride (PVDF); for all conditions, experiments were carried out with and without adding the oxidizing agent hydrogen peroxide. The PVDF temperature degradation occurred at 630 °C. The best yields occurred in the presence of H2O2 10% v/v and heat pretreatment. With sulfuric acid (1 h) it was possible to recover 33.49% Co and 4.63% Li, and (3 h) 36.36% Co and 4.64% Li. With DL-malic acid it was possible to recover (1 h) 29.78% Co and 3.44% Li, and (3 h) 32.73% Co and 3.99% Li.

Lithium recovery is imperative to accommodate the increase in lithium demand. Salt lake brine contains a large amount of lithium and is one of the most important sources of lithium metal. In this study, Li2CO3, MnO2, and TiO2 particles were mixed, and the precursor of a manganese–titanium mixed ion sieve (M-T-LIS) was prepared by a high-temperature solid-phase method. M-T-LISs were obtained by DL-malic acid pickling. The adsorption experiment results noted single-layer chemical adsorption and maximum lithium adsorption of 32.32 mg/g. From the Brunauer–Emmett–Teller and scanning electron microscopy results, the M-T-LIS provided adsorption sites after DL-malic acid pickling. In addition, X-ray photoelectron spectroscopy and Fourier transform infrared results showed the ion exchange mechanism of the M-T-LIS adsorption. From the results of the Li+ desorption experiment and recoverability experiment, DL-malic acid was used to desorb Li+ from the M-T-LIS with a desorption rate of more than 90%. During the fifth cycle, the Li+ adsorption capacity of the M-T-LIS was more than 20 mg/g (25.90 mg/g), and the recovery efficiency was higher than 80% (81.42%). According to the selectivity experiment, the M-T-LIS had good selectivity for Li+ (adsorption capacity of 25.85 mg/g in the artificial salt lake brine), which indicates its good application potential.

Recycling waste Ni–Cd batteries has received much attention recently because of the serious environmental pollution they cause and to avoid the dissipation of valuable metals. Despite significant research, it is still difficult to efficiently recycle valuable and hazardous metals from waste Ni–Cd batteries in an economical and environmentally friendly manner. This study employed a novel process utilizing ultrasound-assisted leaching to recover Ni, Cd, and Co from waste nickel-cadmium (Ni–Cd) batteries. Organic DL-malic acid served as the leaching agent and H 2 O 2 was employed as an oxidizing agent. The effects of various factors on the recovery efficiency of Ni, Cd, and Co, such as leaching temperature, time, DL-malic acid concentration, pulp density, H 2 O 2 concentration, and ultrasound frequency, were also examined. To predict the chemical compounds present before and after the recycling experiments, the solid residues from the metal extraction were analyzed using XRD, XPS, FE-SEM, and EDS element mapping. Concurrently, ICP-OES was utilized to determine the metal content in the leachate. Under optimized conditions of 90 °C, 90 min, 2M DL-malic acid, 160 mL/g pulp density, and 20% ultrasound frequency, over 83% of Ni, 94% of Cd, and 98% of Co were effectively leached from the waste Ni–Cd battery powder. The leaching kinetics of Ni, Cd, and Co followed the surface chemical reaction control model. The activation energies (Ea) for Ni, Cd, and Co leaching were 21.34, 20.47, and 18.38 kJ/mol, respectively. The findings suggest that ultrasound-assisted leaching is an efficient, cost-effective, environmentally friendly, and sustainable alternative for extracting precious and hazardous metals from waste Ni–Cd batteries. Additionally, it reduces industrial chemical usage and enhances waste management sustainability. [Display omitted] • Organic DL-Malic acid was used to leach metals from waste Ni–Cd battery. • Recovery of Ni, Cd and Co from the Ni–Cd batteries was assisted with the ultrasound and H 2 O 2. • More than 83% of Ni, 94% of Cd, and 98% of Co were satisfactorily leached from waste Ni–Cd powder under the optimized conditions. • The applied method is environment-friendly, cost-effective and sustainable. [ABSTRACT FROM AUTHOR]

• Various reductants were examined in the leaching of pyrolusite, focusing on the detailed investigation of DL-malic acid as a green reductant. • Investigation and optimization of parameters such as particle size, DL-malic acid and sulfuric acid concentration, leaching time and temperature. • Kinetic modeling was performed for reductive leaching of manganese in the presence of DL-malic acid. • Mn 3 O 4 nanoparticles were produced. Securing critical metals is crucial for the transition from fossil fuels to renewable energies. In this regard, extracting metals from various sources and low-grade ores can lead to the sustainable production of metals. Manganese, as a strategic metal, can play a significant role in achieving this goal. In this study, various reductants such as oxalic acid, citric acid, ascorbic acid, acetic acid, tannic acid, hydrogen peroxide, iron (II) sulfate, sodium thiosulfate, and DL-malic acid were used to evaluate the feasibility and comparison on the manganiferous iron ore leaching. DL-malic acid was chosen as the main reductant to investigate other factors because it is novel (as a reductant), eco-friendly, cost-effective, accessible, and easily storable. Therefore, more detailed studies on the dissolution of manganiferous iron ore in the presence of DL-malic acid as the reductant were carried out considering different levels of temperature, particle size, acid concentrations, and leaching time. Increasing the temperature from 298 K to 348 K notably boosted the leaching recovery from 27.00 % to 70.11 %. It was observed that decreasing the ore particle size from -212 μm to -38 μm resulted in an enhancement of leaching recovery from 57.74 % to 70.11 %. Also, adding only 250 % stoichiometry of DL-malic acid notably increased the leaching recovery to 70.11 %, compared to just 5.32 % in a reductant-free medium. It should be noted that the concentration of sulfuric acid had a direct impact on leaching recovery, increasing by 28.28 % with a concentration of 0.5 M and by 93.08 % with a concentration of 4 M. In this research work, the kinetic of the leaching process was modeled using the modified shrinking core model (MSCM). The calculated activation energy was about 33 kJ/mole, which confirmed that the mixed mechanism controlled the reaction. Mn 3 O 4 nanoparticles were synthesized using a pregnant leach solution (PLS) and through a multi-stage co-precipitation method. In this method, hydrogen peroxide was used to modify the manganese hydroxide phase as a more eco-friendly method than other heat treatment methods. The SEM and EDX analyses revealed an average particle size of 80 nm with spherical shapes and no impurities. The XRD pattern of the synthesized nanoparticles confirmed the Mn 3 O 4 phase composition. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering the increasing price of raw materials and environmental pollution, the recycling of used lithium battery cathode materials has very important economic and environmental value. In this experiment, a green recycling method is used to recover valuable metals from spent LiNi0.6Co0.2Mn0.2O2 batteries using DL‐malic acid and H2O2 as a leaching system. The effects of reaction temperature, acid concentration, H2O2 volume concentration, reaction time, and solid–liquid ratio on the leaching efficiency are investigated by orthogonal and single variable condition experiments. Under the optimum conditions, the leaching efficiencies of Ni, Co, Mn, and Li are 96.2%, 97.1%, 97.6%, and 98.1%, respectively, while the leaching efficiency of Al is only 3.5%. The effect of H2O2 on the leaching process is further investigated by macroscopic characterization and kinetic analysis. The study indicates that the leaching process is controlled by a chemical reaction in the absence of H2O2, and the leaching process after the addition of H2O2 is controlled by the chemical reaction process and the diffusion process. [ABSTRACT FROM AUTHOR]

An effort to improve the solubility of albendazole (ABZ), an anthelmintic drug has been successfully carried out through the formation of multicomponent crystal with dl-malic acid (MAL). Construction of phase solubility curve of ABZ in MAL solution and crystal morphological observations after recrystallization in the acetone-ethanol (9:1) mixture were performed for initial prediction of multicomponent crystal formation. ABZ-MAL multicomponent crystal was prepared by wet grinding or also known as solvent-drop grinding (SDG) with acetone-ethanol (9:1) mixture as a solvent followed by characterization of the multicomponent crystal formation by powder X-ray diffraction and Fourier transform infrared (FTIR) methods. The solubility of ABZ-MAL multicomponent crystal was tested in water at ambient temperature and in pH 1.2, 4.5 and 6.8 of buffered solutions at 37°C. The phase solubility curve of the ABZ in the MAL solution showed type Bs. The ABZ-MAL mixture has a different crystalline morphology than pure ABZ and MAL after recrystallization in the acetone-ethanol mixture (9:1). The powder X-ray diffraction pattern and the FTIR spectrum of ABZ-MAL from SDG different from intact ABZ and MAL powder X-ray diffraction patterns and these results can indicate the ABZ-MAL multicomponent crystal formation. The ABZ-MAL multicomponent crystal has better solubility than pure ABZ in all media used. These results can be concluded that ABZ-MAL multicomponent crystal can be prepared by solvent-drop grinding method with acetone-ethanol (9:1) mixture as a solvent and can increase the solubility of albendazole.

The present investigation involves rapid and efficient synthesis of a series of some novel derivatives for 1,2-bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)-ethan-1-ol 5–21 using dl-malic acid under microwave (MW) irradiation. Reaction with several alkylating agents such as epichlorohydrin, 3-chloropropanol, (2-acetoxyethoxy) methyl bromide, propargyl bromide and chloroacetamide was studied. Not only higher yields but also shorter reaction times were observed in comparison with thermal procedure. Structures of the realized products have been established on the basis of their 1H/13C NMR, IR, elemental analysis and correlation experiments. It is well known that 1,2,4-triazole ring systems are famous for their antifungal activities, so the synthesized compounds were screened for their antifungal activities. The minimal inhibitory concentration (MIC) of the screened compounds exhibited prominent results against Gram (+ ve) and Gram (− ve) and antifungal activities comparing with the standard drugs. [ABSTRACT FROM AUTHOR]

• Ultrasound enhancement is novely applied for leaching process. • A closed-loop process is developed to recycle spent cathode materials. • The mechanism of ultrasound-assisted leaching is explained. Herein, a novel process involving ultrasound-assisted leaching developed for recovering Ni, Li, Co, and Mn from spent lithium-ion batteries (LIBs) is reported. Carbonate coprecipitation was utilized to regenerate LiNi 0.6 Co 0.2 Mn 0.2 O 2 from the leachate. Spent cathode materials were leached in DL-malic acid and hydrogen peroxide (H 2 O 2). The leaching efficiency was investigated by determining the contents of metal elements such as Li, Ni, Co, and Mn in the leachate using atomic absorption spectrometry (AAS). The filter residue and the spent cathode materials were examined using Fourier transform infrared (FTIR) and scanning electronic microscopy. The leaching efficiencies were 97.8% for Ni, 97.6% for Co, 97.3% for Mn, and 98% for Li under the optimized conditions (90 W ultrasound power, 1.0 mol/L DL-malic acid, 5 g/L pulp density, 80 °C, 4 vol% H 2 O 2 , and 30 min). The leaching kinetics of the cathode in DL-malic acid are in accordance with the log rate law model. The electrochemical analysis indicates that the LiNi 0.6 Co 0.2 Mn 0.2 O 2 regenerated at pH 8.5 has good electrochemical performance. The specific capacity of the first discharge at 0.1 C is 168.32 mA h g−1 at 1 C after 50 cycles with a capacity retention of 85.0%. A novel closed-loop process to recycle spent cathode materials was developed, and it has potential value for practical application and for contributing to resource recycling and environmental protection. [ABSTRACT FROM AUTHOR]

Background: dl-Malic acid (dl-M) is used widely in cosmetic formulations as a pH-adjuster or as a preservative. dl-M is used as an exfoliator in the form of α-hydroxy acids. However, the role of dl-M in skin diseases (including atopic dermatitis (AD)) has not been studied deeply. We wished to reveal the effect of dl-M on AD induced by 2,4-dinitrochlorobenzene (DNCB) in Balb/c mice. Methods: The thickness and immune-cell infiltration into the dermis and epidermis were evaluated. Moreover, serum levels of cytokines, as well as expression of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) in tissue were measured in AD mice. We also studied the effect of dl-M on inflammatory mediators in a human keratinocyte (HaCaT) cell line. Results: The dl-M (high) group improved skin condition compared with the DNCB-treated group. The dl-M (high) group inhibited phosphorylation of MAPK and NF-κB in skin tissue. dl-M reduced serum levels of interleukin-4 and IgE. Finally, dl-M decreased the expression of thymus and activation-regulated chemokine, monocyte chemoattractant protein-1 and intercellular cell adhesion molecule induced by interferon-gamma/tumor necrosis factor-α in HaCaT cells. Discussion: These results suggest that dl-M can improve the skin conditions of AD mice. [ABSTRACT FROM AUTHOR]

The ability of non-toxic and biodegradable deep eutectic solvent (DES) choline chloride + DL-malic acid in mole ratio 1:1, for the breaking of the azeotropes heptane + methanol and toluene + methanol by means of liquid– –liquid extraction was evaluated. Ternary liquid–liquid equilibrium experiments were performed at 298.15 K and at atmospheric pressure. Densities, viscosities and refractive indices of DES + methanol and water + DES systems were experimentally determined over a wide temperature range and at atmospheric pressure. Additionally, the viscosities of DES + glycerol mixture were - determined at temperatures up to 363.15 K to check how much the addition of glycerol decreases high viscosities of DES. The results indicate that the addition of small amounts of water or glycerol as a third component significantly decreases the viscosity of the investigated deep eutectic solvent. Based on the selectivity and distribution ratio values, the extraction ability of the investigated deep eutectic solvent, in comparison with the conventionally used solvents, yields promising results. Non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models were satisfactorily applied for correlation of experimental phase equilibrium data for two ternary mixtures. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172063]

By using the inverse Kirkwood-Buff integrals (IKBI) method, the differences between the local, around the solute and the bulk mole fractions of both solvents in saturated solutions of L-arabinose (compound 3) and DL-malic acid (compound 3) in ethanol (compound 1) + water (compound 2) binary mixtures were derived from their thermodynamic properties. Accordingly, it is found that these compounds are sensitive to preferential solvation effects; in this way, the preferential solvation parameter (dx1,3) for L-arabinose is slightly positive in water-rich mixtures but negative in those beyond 0.25 in ethanol mole fraction. In different way, the dx1,3 values of DL-malic acid are negative in almost all the compositions. The highest solvation by ethanol observed in water-rich mixtures for L-arabinose could be due mainly to polarity effects. Otherwise, the preference of these compounds for water in ethanol-rich mixtures could be explained in terms of the higher acidic behavior of water interacting with hydrogen-acceptor hydroxyl groups in L-arabinose and DL-malic acid.

Abstract: The solubility of DL-malic acid in methanol, ethanol, propanol, butanol, ethyl acetate and acetonitrile in the temperature range 283-318 K was measured by acid-base titration method. The solubility of DL-malic acid increased with elevating temperature. The solubility data were correlated by the modified Apelblat, Buchowski-Książczak, Van't Hoff, Wilson, and non-random two-liquid equations. The calculation results showed that these equations provide good prediction with the acceptable ARD values and RMSD values among all the satisfactory fitting results given by each equation. The mixing Gibbs energy, enthalpy and entropy of real solution were derived based on the Wilson equation and the measured solubility data. [ABSTRACT FROM AUTHOR]

An eco-friendly and benign process has been investigated for the dissolution of Li, Co, Ni, and Mn from the cathode materials of spent LiNi1/3Co1/3Mn1/3O2 batteries, using DL-malic acid as the leaching agent in this study. The leaching efficiencies of Li, Co, Ni, and Mn can reach about 98.9%, 94.3%, 95.1%, and 96.4%, respectively, under the leaching conditions of DL-malic acid concentration of 1.2 M, hydrogen peroxide content of 1.5 vol.%, solid-to-liquid ratio of 40 g l-1, leaching temperature of 80°C, and leaching time of 30 min. In addition, the leaching kinetic was investigated based on the shrinking model and the results reveal that the leaching reaction is controlled by chemical reactions within 10 min with activation energies (Ea) of 21.3 kJ·mol-1, 30.4 kJ·mol-1, 27.9 kJ·mol-1, and 26.2 kJ·mol-1 for Li, Co, Ni, and Mn, respectively. Diffusion process becomes the controlled step with a prolonged leaching time from 15 to 30 min, and the activation energies (Ea) are 20.2 kJ·mol-1, 28.9 kJ·mol-1, 26.3 kJ·mol-1, and 25.0 kJ·mol-1 for Li, Co, Ni, and Mn, respectively. This hydrometallurgical route was found to be effective and environmentally friendly for leaching metals from spent lithium batteries. [ABSTRACT FROM AUTHOR]

In this study, dl-malic acid and hydrogen peroxide were used as leaching agents to remove metals from e-waste (printed-circuit boards) and itaconic acid-grafted poly(vinyl alcohol)-encapsulated wood pulp (IA-g-PVA-en-WP) to uptake metals from leachate with high proficiency [11.63 mg g; 93.03 % for Cd(II), 11.90 mg g; 95.18 % for Pb(II), and 12.14 mg g; 97.08 % for Ni(II)]. Metals were recovered from the loaded biosorbent by desorption studies. The standard analytical techniques, such as elemental analysis, Fourier-transform-infrared spectroscopy, scanning electron microscopy, atomic force microscopy, and thermogravimetric analysis, were used to characterize the recovering agent (biosorbent). At equilibrium, the metal uptake data were fitted to Langmuir and D-R isotherms ( R > 0.99) significantly, revealing, the homogeneous distribution of active sites on biosorbent's backbone. The possible mechanism appeared to be ion exchanges of metal ions with H together with binding over functionalities (COO). Dimensionless equilibrium parameter ( R ) showed the favourability of metal uptake at lower concentration, while mean adsorption energy ( E) certified the physical binding of metal on functionalities which was further confirmed by sticking probability and activation energy parameters. Reusability studies were also conducted to state the performance of biosorbent. [ABSTRACT FROM AUTHOR]

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Insufficient wine acidity can affect wine quality and stability. To overcome this problem, DL-malic acid can be added to the grape juice prior to fermentation. We have investigated the effect of DL-malic acid on wine fermentations and its influence on the final concentration of L-malic acid, naturally present in grape juice. To this end yeast strains that metabolise L-malic acid in different ways were tested and compared; namely, Schizosaccharomyces pombe (efficient L-malic acid degrader), Saccharomyces cerevisiae (non-degrader), hybrid strain S. cerevisiae x S. uvarum (intermediate degrader) and Saccharomyces uvarum (promoting L-malic acid synthesis). In all cases, D-malic acid passively entered the yeast cells and did not undergo malo-alcoholic fermentation. However, its presence in the juice, as a component of the mixture of D- and L- malic acid (DL-malic acid), reduced the amount of L-malic acid that can be degraded or synthesised by yeasts during malo-alcoholic fermentation.

• A green acid-leaching process is developed to recover valuable metals. • The application of the reagent regime can greatly reduce environmental pollution. • The acid-leaching mechanism has been preliminarily studied. • Kinetic analysis is performed to better understand the leaching process. The traditional inorganic acid leaching method for recycling spent ternary lithium-ion batteries (NCM) materials presents serious environmental pollution and unsafe problems. In this study, a green leaching process for recovering valuable metals from the spent NCM materials using dl -malic acid as the leaching agent and glucose as the reductant is developed, and systematicalsly investigates the leaching kinetics and interface reaction. The results suggest that the leaching efficiencies of Ni, Co, Mn, and Li reach 90.14 %, 90.58 %, 98.66 %, and 98.53 %, respectively, under the optimal conditions of 1 mol/L dl -malic acid, 0.5 g/g glucose, 90℃ leaching temperature, and 25 g/L pulp density for 120 min. The apparent activation energies for leaching of Ni, Co, Mn, and Li are determined as 55.45, 76.08, 39.42, and 42.09 kJ/mol, respectively, indicating that the surface chemical reaction is the rate-controlling step during this leaching process. This process can be an environmentally friendly alternative method to recover valuable metals from spent NCM. [ABSTRACT FROM AUTHOR]

A study of metastable zone width (MSZW) and nucleation parameters for a cooling crystallization of DL-malic acid-water system is described in this paper. Experimental determination of the MSZW was performed using a laser method in order to carry out the estimation of nucleation parameters. Measured MSZWs can be affected by a variety of parameters, such as cooling rate, saturation temperature, agitation rate, and so on. In this work, the MSZWs were found to decrease with an increase of saturation temperature, and levels of agitation, while it increased with an increase of cooling rate. Two classical theoretical approaches, Nyvlt's approach and self-consistent Nyvlt-like approach were used to analyze the experimental data on MSZWs. [ABSTRACT FROM AUTHOR]

The solubility of dl-malic acid in water, ethanol and ethanol + water mixtures was investigated by a static analytical technique using the acid-base titration method at temperatures ranging from 298.15 to 333.15 K. The experimental results indicated that the solubility of dl-malic acid in the binary solvent mixtures increases with increasing temperature and decreases with increasing mass fraction of ethanol. The measured solid-liquid equilibrium (SLE) data were correlated by the modified Apelblat, λh and van't Hoff equations. The calculated solubility demonstrated good agreement with the experimental data. It was found that the modified Apelblat equation could give the best correlation results, and subsequently used to derive the standard enthalpy, entropy and Gibbs energy change of solution of dl-malic acid in ethanol + water binary mixtures. [ABSTRACT FROM AUTHOR]

• There is a maximum corrosion resistance of Sn-58Bi alloy with the concentration increase of DL-malic acid. • A p-type semiconductor oxide film consisting of SnO 2 and SnO x formed on the surface of Sn-58Bi alloy. • The thickness of the film and proportion of SnO x in the film decide the corrosion resistance of Sn-58Bi alloy. The corrosion behavior of Sn-58Bi alloy in DL-malic acid solutions with different concentrations has been explored via electrochemistry and physical methods. Results indicate films formed on the surface of Sn-58Bi alloy are p-type semiconductors, consisting of SnO 2 and nonstoichiometric SnO x (1 < x < 2). With the increasing of DL-malic acid concentration, the corrosion resistance increases first then decreases, and the maximum appears at 7 wt%, where the thickest film and the minimum proportion of SnO x emerge. The SnO x with massive electron holes as charge carriers makes the film less protective. Both the thickness of the film and the proportion of SnO x are responsible for the corrosion behavior of Sn-58Bi alloy in DL-malic solutions. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of dietary dl-malic acid (MA) supplementation on feed intake, methane (CH4) emissions, and performance of mid lactation Holstein-Friesian cows at pasture. Twenty-four (6 primiparous and 18 multiparous) midto late-lactation cows (206 ± 65 d in milk) grazing a mixed-species grass sward were blocked on parity, days in milk, and pretrial milk yield, and randomly allocated within block to 1 of 2 dietary treatments offered twice daily at milking in 2 equal portions (6 kg/d in total): a control concentrate (0 g/d of MA) and a concentrate supplemented with MA (480 g/d of MA) over a 6-wk period. Cows were allowed a 3-wk acclimation period followed by a 5-d CH4 measurement period. Enteric CH4 emissions were estimated using the sulfur hexafluoride tracer gas technique, and herbage intake was measured using the n-alkane technique. Dietary supplementation with MA did not affect voluntary intake of herbage or total dry matter intake, body weight gain, milk yield, fat-corrected milk yield, or daily CH4 production. These results suggest that there is little benefit to be gained from the dietary supplementation of dairy cows at pasture with MA at least within the inclusion rates used in this study. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of dietary concentration of DL-malic acid (MA) on DM1, CH4 emission, and rumen fermentation in beef cattle. Two Latin square experiments were conducted. In Exp. 1, six beef heifers (19 ± 1 mo old) were assigned in a duplicated Latin square to 1 of 3 dietary concentrations of MA on a DM1 basis (0%, MA-0; 3.75%, MA-3.75; or 7.5%, MA-7.5) over 3 periods. In Exp. 2, four rumen-fistulated steers (48 ± 1 mo old) were assigned to 1 of 4 dietary concentrations of MA (0%, MA-0; 2.5%, MA-2.5; 5.0%, MA-5.0; or 7.5%, MA-7.5) on a DM1 basis, over 4 periods. Both experimental diets consisted of grass silage and pelleted concentrate (containing MA). Silage was fed ad libitum once daily (a.m.), whereas concentrate was fed twice daily (am. and p.m.) with the aim of achieving a total DM1 of 40:60 silage:concentrate. In both Exp. 1 and 2, experimental periods consisted of 28 d, incorporating a 13-d acclimatization, a 5-d measurement period, and a 10-d washout period. In Exp. 1, enteric CH4, feed apparent digestibility, and feed intake were measured over the 5-d measurement period. In Exp. 2, rumen fluid was collected on d 16 to 18, immediately before (a.m.) feeding and 2, 4, 6, and 8 h thereafter. Rurnen pH was determined and samples were taken for protozoa count, VFA, and ammonia analysis. Enteric CH4 emissions were estimated by using the sulfur hexafluoride tracer technique and feed apparent digestibility was estimated by using chromic oxide as an external marker for fecal output. In Exp. 1, increasing dietary MA led to a linear decrease in total DM1 (P < 0.001) and total daily CH4 emissions (P < 0.001). Compared with the control diet, the greatest concentration of MA decreased total daily CH4 emissions by 16%, which corresponded to a 9% reduction per unit of DM1. Similarly, in Exp. 2, inclusion of MA reduced DM1 in a linear (P = 0.002) and quadratic (P < 0.001) fashion. Increasing dietary MA led to a linear decrease in molar proportion of ace- tic (P 0.004) and butyric acids (P < 0.001) and an increase in propionic acid (P < 0.001). Ruminal pH tended to increase (P = 0.10) with increasing dietary MA. Dietary inclusion of MA led to a linear (P = 0.01) decrease in protozoa numbers. Increasing supplementation with MA decreased CH4 emissions, but DM1 was also decreased, which could have potentially negative effects on animal performance. [ABSTRACT FROM AUTHOR]

• The effects of DL-malic acid solutions with different concentrations on CSC were studied. • The inhibitory effects of malic acid on coal samples with different water-soaking times were revealed. • The inhibition mechanism of DL-malic acid was discussed both macroscopically and microscopically. Inhibitors play an important role in preventing and controlling coal spontaneous combustion (CSC). In this study, the effect of DL-malic acid, an environment-friendly inhibitor, on the CSC characteristics of lignite and bituminous coal was studied. A contrastive analysis was conducted on the inhibitory effects of malic acid solution with different concentrations on CSC. Moreover, the inhibition characteristics of malic acid on coal samples with different soaking times were analyzed. In so doing, the inhibition mechanism of malic acid on CSC was revealed. It was found that malic acid can obviously inhibit CSC of lignite and bituminous coal. After the treatment of malic acid, the concentrations of CO released by coal samples during oxidation fall, and the crossing-point temperatures increase. Compared with the raw coal, the acid-treated coal corresponds to lower concentrations of free radicals and functional groups –CH 2 - and –CH 3 and boasts better thermal stability before 150 °C. A contrastive analysis on the inhibitory effects on coal samples with different soaking times disclose that the water-soaked coal sample is inhibited better in CSC by malic acid than the unsoaked coal sample. The malic acid solution can effectively weaken the catalytic effect of metal ions in coal and inhibit the generation of free radicals, thus inhibiting CSC well. [ABSTRACT FROM AUTHOR]

The effects of various cooling modes such as natural cooling mode, linear cooling mode, and controlled cooling modes type A and B in a batch cooling crystallizer on crystal size distribution (CSD) as well as the mean crystal size have been studied for DL-malic acid. The natural cooling mode was found to yield crystals in the range of 250 to 1000 µm, whereas the linear cooling mode was found to yield larger crystals, in the range of 800 to 1600 µm. The mean crystal size was found to increase in the order of natural cooling mode, controlled cooling mode A, controlled cooling mode B, and linear cooling mode. Since linear cooling mode was found to yield larger mean crystal size, the effect of operating parameters such as the seed concentration and agitation rates on CSD was assessed using the linear cooling mode. The increase in seed concentration from 0.5 to 1% resulted in a larger mean crystal size; while an increase from 1 to 2% reduced the mean crystal size. An agitator rate of 90 rpm was found to yield larger mean crystal size than agitation rates of 60 and 120 rpm. [ABSTRACT FROM AUTHOR]

• Solubility of DL-malic acid + fumaric acid + water ternary system was determined. • Isothermal ternary solid–liquid equilibrium phase diagrams were established. • Experimental solubility was correlated by Wilson, NRTL, and Margules models. • Interaction energy and hydrogen bond length were obtained by molecular simulation. Solubility of DL-malic acid and fumaric acid in water for binary and ternary systems was determined through high-performance liquid chromatography (HPLC) at atmospheric pressure in this study. Six isothermal ternary phase diagrams were established at temperatures of 283.15, 293.15, 303.15, 313.15, 323.15, and 333.15 K. Every isothermal ternary phase diagram contains three crystalline regions (pure DL-malic acid, pure fumaric acid, and mixture of DL-malic acid and fumaric acid), two co-saturated boundary curves, and one invariant co-saturated point. All diagrams show that the crystalline region of fumaric acid (III) is significantly larger than that of DL-malic acid (II) at six temperatures. Wilson, NRTL, and Margules models were used to correlate and predict binary and ternary system data and the corresponding calculation precision was assessed using relative average deviation (RAD) and root-mean-square deviation (RMSD). The calculated results of Wilson and NRTL models were consistent with experimental data, and maximum values of RAD and RMSD were 2.93 × 10−2 and 3.67 × 10−3, respectively. Margules model can be used to fit solubility data of DL-malic acid unlike those of fumaric acid. Interaction energy and hydrogen bond length of DL-malic acid and fumaric acid with water were calculated via molecular simulation, and the results can be used to explain solubility behavior of DL-malic acid and fumaric acid in water. [ABSTRACT FROM AUTHOR]

• Solubility of (DL-malic acid + maleic acid + water) was measured. • Ternary phase diagrams were established and crystallization regions were obtained. • Solubility was correlated by Wilson and NRTL models with interaction parameters. The solid–liquid phase equilibrium data of (DL-malic acid + maleic acid + water) in binary and ternary systems were measured by high performance liquid chromatography (HPLC) method at 283.15 K, 293.15 K, 303.15 K, 313.15 K, 323.15 K and 333.15 K under atmospheric pressure, and then six isothermal ternary phase diagrams were established. Each isothermal ternary phase diagram included one co-saturated point (invariant), two saturated boundary curves, and three crystallization regions (DL-malic acid, maleic acid, and mixture of both). For extending the application of measured solid–liquid phase equilibrium data, the Wilson model and NRTL model were used for correlation and prediction, and the relative average deviation (RAD) and root-mean-square deviation (RMSD) were applied to assess the calculation precision. The maximum values of RAD and RMSD were 2.61 × 10−2 and 1.87 × 10−3 with Wilson model, 3.31 × 10−2 and 1.86 × 10−3 with NRTL model, respectively, which demonstrated that the calculated data were close to the experimental data, and accurate theoretical data under other experimental conditions were able to acquire through the two models in DL-malic acid + maleic acid + water system. The study provided reliable and accurate data for separating the mixture of DL-malic acid and maleic acid in water. [ABSTRACT FROM AUTHOR]

A series of biodegradable copolyester of poly (butylene succinate-co-butylene malate) (P (BS-co-BM)) bearing hydroxyl groups were prepared by one-pot synthetic strategy without hydroxy-protection. The structure and properties of the P (BS-co-BM) were characterized by nuclear magnetic resonance (1H NMR), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), polarized optical microscope (POM), contact angle tester and enzymatic degradation. The results showed that the P (BS-co-BM) manifested excellent thermal properties. The glass transition temperature (T g) of the P (BS-co-BM) increased with malic acid units added, the crystallizability temperature (T c) decreased from 72.6 °C to 21.7 °C, and the melting point temperature (T m) decreased from 117.9 °C to 82.4 °C. The crystallization rate of poly(butylene succinate) (PBS) segment within P (BS-co-BM) was improved by the introduction of malic acid. The enzymatic degradation rate increased with hydrophilicity of the copolyester improving. [Display omitted] • P (BS-co-BM) were prepared by one-pot synthetic strategy without hydroxy-protection. • T g of the P (BS-co-BM) increased with malic acid added, the crystallizability temperature and the T m decreased. • The crystallization rate of PBS segment within P (BS-co-BM) was improved by the introduction of malic acid. • The enzymatic degradation rate increased with hydrophilicity of the copolyester improving. [ABSTRACT FROM AUTHOR]

In order to develop an efficient and sustainable plasticizer, the waste cooking oil and malic acid were used as the main raw materials in this study to synthesize a bio-based plasticizer (acetylated-fatty acid methyl ester-malic acid ester, AC-FAME-MAE) by environment-friendly methods, and the structure was characterized by FTIR and 1H NMR. The properties of the poly (vinyl chloride) (PVC) with AC-FAME-MAE were tested and compared with those of the PVC plasticized with DOP (di-2-ethylhexyl phthalate) and EFAME (epoxy fatty acid methyl ester), respectively. The results of tensile test, TGA and leaching test showed that the mechanical properties, thermal stability and overall solvent resistance of PVC films with AC-FAME-MAE were significantly better than those of PVC films plasticized by DOP or EFAME. From the results of DMA, the plasticized efficiency of AC-FAME-MAE was as good as DOP. The application of AC-FAME-MAE has higher safety in the food industry based on the results of food simulation fluids experiment. • The raw material of bio-based plasticizer is waste oil. • The reaction process is environmentally friendly. • This plasticizer has excellent plasticizing properties. • This plasticizer can be safely used in food packaging. [ABSTRACT FROM AUTHOR]