Hydrothermal treatment of pearl millet grains:Effects on nutritional composition,antinutrients and flour properties

Pearl millet(Pennisetum glaucum)is one of the major millets with high nutritional properties.This crop exhibits exceptional resilience to drought and high temperatures.However,the processing of pearl millet poses a significant challenge due to its high lipid content,enzyme activity,and presence of antinutrients.Consequently,it becomes imperative to enhance the quality and prolong the shelf life of pearl millet flour by employing suitable technologies.Hydrothermal treatment in the food industry has long been seen as promising due to its potential to reduce microbial load,inactivate enzymes,and improve nutrient retention.This study aims to investigate the effects of hydrothermal treatment on the quality characteristics of pearl millet.The independent variables of the study were soaking temperature(35,45,55℃),soaking time(2,3,4 h),and steaming time(5,10,15 min).Treatment conditions had a statistically significant effect on nutrient retention.Major antinutrients like tannins and phytates were reduced by 0.99% to 5.94% and 0.36% to 6.00%,respectively,after the treatment.Lipase activity decreased significantly up to 10% with the treatment conditions.The findings of this study could potentially encourage the use of pearl millet flour in the production of various food items and promote the application of hydrothermal treatment in the field of food processing.

Multi-Component Resource Recycling from Waste Light-Emitting Diode Under Hydrothermal Condition:Plastic Package Degradation,Speciation of Nano-TiO_(2),and Environmental Impact Assessment

Light emitting diodes(LEDs)have accounted for most of the lighting market as the technology matures and costs continue to reduce.As a new type of e-waste,LED is a double-edged sword,as it contains not only precious and rare metals but also organic packaging materials.In previous studies,LED recycling focused on recovering precious and strategic metals while ignoring harmful substances such as organic packaging materials.Unlike crushing and other traditional methods,hydrothermal treatment can provide an environment-friendly process for decomposing packaging materials.This work developed a closed reaction vessel,where the degradation rate of plastic polyphthalamide(PPA)was close to 100%,with nano-TiO_(2)encapsulated in plastic PPA being efficiently recovered,while metals contained in LED were also recycled efficiently.Besides,the role of water in plastic PPA degradation that has been overlooked in current studies was explored and speculated in detail in this work.Environmental impact assessment revealed that the proposed recycling route for waste LED could significantly reduce the overall environmental impact compared to the currently published processes.Especially the developed method could reduce more than half the impact of global warming.Furthermore,this research provides a theoretical basis and a promising method for recycling other plastic-packaged e-waste devices,such as integrated circuits.

Breaking the temperature limit of hydrothermal carbonization of lignocellulosic biomass by decoupling temperature and pressure

Hydrothermal carbonization(HTC) of lignocellulosic biomass is a promising technology for the production of carbon materials with negative carbon emissions. However, the high reaction temperature and energy consumption have limited the development of HTC technology. In conventional batch reactors, the temperature and pressure are typically coupled at saturated states. In this study, a decoupled temperature and pressure hydrothermal(DTPH) reaction system was developed to decrease the temperature of the HTC reaction of lignocellulosic biomass(rice straw and poplar leaves). The properties of hydrochars were analyzed by scanning electron microscopy(SEM), Fourier transform infrared(FTIR) spectroscopy, X-ray photoelectron spectroscopy(XPS), Raman spectroscopy, X-ray diffraction(XRD), thermogravimetric analyzer(TGA), etc. to propose the reaction mechanism. The results showed that the HTC reaction of lignocellulosic biomass could be realized at a low temperature of 200℃ in the DTPH process, breaking the temperature limit(230℃) in the conventional process. The DTPH method could break the barrier of the crystalline structure of cellulose in the lignocellulosic biomass with high cellulose content, realizing the carbonization of cellulose and hemicellulose with the dehydration, unsaturated bond formation, and aromatization. The produced hydrochar had an appearance of carbon microspheres, with high calorific values, abundant oxygen-containing functional groups, a certain degree of graphitization, and good thermal stability. Cellulose acts not only as a barrier to protect itself and hemicellulose from decomposition, but also as a key precursor for the formation of carbon microspheres. This study shows a promising method for synthesizing carbon materials from lignocellulosic biomass with a carbon-negative effect.

Effect of Hydrothermal Treatment on Suppressing Coking of ZSM-5 Zeolite during Methanol-to-Propylene Reaction

Fresh ZSM-5 zeolite catalysts were pretreated at 460 ℃and 500 ℃with various cumulative amount of water feed(CAWF) in a fixed bed reactor. The catalytic process was carried out under the following conditions: a temperature of 480 ℃; a methanol WHSV of 3 h-1; a methanol partial pressure of 30 k Pa; and a time on stream of 12 h, 24 h and 48 h, respectively. The BET parameters of catalysts and diffusion coefficients of toluene showed that there were two types of mesopores generated under different hydrothermal conditions. Mild temperature and moderate CAWF conditions led to external open mesopores which could be entered from the external surface of the zeolite, while a high temperature or a high CAWF condition resulted in the generation of macropores or internal isolated mesopores, which were occluded in the microporous matrix. The TGA results showed that catalyst with external open mesopores had good ability to resist coke accumulation and good performance on propylene selectivity, while the internal isolated mesopores did no contribute to the increased diffusivity of reactants and products.

Hydrothermal treatment of metallic-monolith catalyst support with self-growing porous anodic-alumina film

Metallic-monolith catalyst support with self-growing porous anodic alumina(PAA)film was prepared by anodizing Al plate.The effect of hydrothermal treatment(HTT)on the crystalline state and textural properties of PAA film was investigated by XRD,BET,SEM and TG.The HTT treatment above 50°C and the subsequent calcination above 300°C could convert the amorphous skeleton alumina intoγ-alumina and increase the specific surface area(SBET).However,SEM images showed the HTT modification was a non-uniform process along the thickness of PAA film.The promotion effect of HTT on SBETwas non-linear,and the slope of SBETgradually decreased with the HTT temperature or time increased.The limited HTT effect should be attributed to a changed pore structure caused by an unfavorable pore sealing limitation.Pore widening treatment(PWT)before HTT could break the pore sealing limitation,because of the reduced internal diffusion resistance of hydrothermal reaction.The synergistic combination of PWT and HTT developed a PAA support with a large SBETcomparable to commercialγ-alumina.In the catalytic combustion of toluene,the Pt-based catalyst prepared by using the PWT and HTT comodified PAA support gave higher Pt dispersion and more favorable catalytic activity than that treated by HTT alone.The presence of a bimodal pore structure was suggested to be a decisive reason.

The Impact of Hydrothermal Treatments on Technological Properties of Whole Grains and Soriz (<i>Sorghum oryzoidum</i>) Groats

Cereals and cereal products are the basic element in ensuring the food security of the population. Most cereal-based foods contain gluten. Nutritional therapy is the only treatment for people with gluten-related disorders. No gluten-free products are manufactured in the Republic of Moldova, and the imported ones are sold at very high prices. In this context, Moldova is an unexplored field and research is required. The paper investigated the impact of hydrothermal treatments on whole grains and sorghum groats. It was found that whole grains and sorghum groats have a cooking time of about 130 and 40 minutes, respectively, which can be reduced by about 2 times by prior hydration in water. Hydration media and their concentrations (NaCl solutions;sol. NaHCO3 and C6H8O7 concentrations 0.5%;1.0% and 2.0%) differently influence the cooking time, mass, volume and firmness of the grains.

Structural Changes of Y Zeolites with Different Initial SiO_2/Al_2O_3 Ratios during Hydrothermal Treatment

The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are subjected to hydrothermal treatment at four different temperatures. For zeolite with a lower initial SiO2/Al2O3 ratio of 4.2, mesopores are easily formed because more framework aluminum is detached. Moreover, two kinds of mesopores are produced at a higher temperature due to the interconnection of vacancies and smaller mesopores. For zeolite with a higher initial SiO2/Al2O3 ratio of 6.0, there are less mesopores formed as compared with the lower initial SiO2/Al2O3 ratio sample, but there are some macropores formed. This may be attributed to the isolation of vacancies and the different distributions of aluminum in the crystal lattice of the zeolite. The experiment data show that NaY with the SiO2/Al2O3 ratio of 6.0 retains a high relative crystallinity during the hydrothermal treatment. This proves that a high framework SiO2/Al2O3 ratio benefits the stability of zeolite.

Effect of Dehulling and Hydrothermal Treatment on the Amino Acid Content of Soriz (<i>Sorghum oryzoidum</i>)

Cereals are the basic element in ensuring the food security of the population through the significant intake of carbohydrates, proteins, dietary fiber, vitamins and minerals. The processing of cereals leads to changes in their nutritional quality, which could lead to both reduced nutrients and anti-nutrients. Gluten-free cereal varieties attract attention as raw materials to improve the nutritional quality of food and to diversify the product range. Sorghum (Sorghum oryzoidum) is a hybrid of sorghum, obtained at the Institute for Scientific Research for Corn and Sorghum in the Republic of Moldova, by crossing Sudan grass (S. sudanense) and bicolor sorghum (S. bicolor). The research aimed to determine the impact of dehulling and hydrothermal treatment on the amino acid content of soriz. The obtained results reported that the dehulling and hydrothermal treatment led to the uneven modification of the amino acid content in the investigated samples. As a result of dehulling, the total amount of essential amino acids decreased by 19.8% compared to the native grain. Boiling whole grains without prior hydration led to 34% loss of essential amino acids compared to native grains, and pre-hydration of the grains and subsequent boiling reduced essential amino acid losses by 8% compared to cooked grains without hydration. Boiling grains with pre-hydration had a positive effect on the chemical index of lysine, methionine and cysteine, leucine and tryptophan. However, the nutritional quality of sorghum grain proteins and derivatives obtained, evaluated according to the chemical index, is low. The results obtained reported that dehulling and hydrothermal treatment unevenly altered the amino acid content, and the method of boiling grains with pre-hydration had a positive effect on the CSI of lysine, methionine and cysteine, leucine and tryptophan.

Monosaccharide Recovery from Peat and Peatified Wood by Ultrasonication Pretreatment and Hydrothermal Treatment

Peat and peatified wood are significant carbohydrate resources in tropical rainforests. The carbohydrates of cellulose and hemicellulose are important sources of monosaccharides for both vital activities and industrial applications, such as furan production of furfural and hydroxymethyl furfural. Hydrothermal treatment at 200°C and ultrasonic irradiation pretreatment were used to recover monosaccharides from the abovementioned resources. The monosaccharide recovery from peat was shown to be higher than that from peatified wood. The conversion to organic acids is considered to proceed rapidly because acids are always detected with monosaccharides. This conversion is outstripped by the organic acid-to-gas reaction for treatment times longer than 20 min. The monosaccharide recovery from peatified wood was improved by the ultrasonication pretreatment. It is considered that ultrasonic irradiation broke down lignin blockages, enabling water molecules to access the carbohydrates more easily in the subsequent hydrothermal treatment.

Optimization of hydrothermal pretreatment for co-utilization of xylose and glucose of cassava anaerobic residue for producing ethanol

The development of a process that could recover biofuel from industrial cellulose waste can not only reduce the negative environmental impacts by using fossil fuels, but also bring a green idea for the waste’s disposing. In this study, hydrothermal pretreatment was optimized for cassava anaerobic residue, a cellulosic waste from cassava ethanol industry, to co-utilize xylose and glucose for producing bioethanol. The effect of the main pretreatment conditions, namely, temperature, solid content and time, was explored for the highest recovery of xylose in prehydrolysate and glucose in enzymatic hydrolysate. The single factor experiment results showed that the conditions for maximum xylose recovery in prehydrolysate and glucose recovery in enzymatic hydrolysate were 60℃, 75 min, 10% solids and 160℃, 75 min, 10% solids, respectively. Whereafter, response surface methodology(RSM) was applied to further optimize the pretreatment conditions for the maximum theoretical ethanol production through utilizing both xylose and glucose. A treatment at 163℃, for 59 min and with 9.5%solids was found optimal, with the highest ethanol production of 20.2 mg·g^-1 raw material. Furthermore, in order to assess the impacts of the pretreatment on cassava anaerobic residue, the changes in crystallinity and morphology for untreated and pretreated solids were investigated.

Influence of Yttria Stabilized Zirconia and Hydrothermal Treatment on Plasma Sprayed Hydroxyapatite Coatings

A post-treatment of hydrothermal process was conducted to evaluate its effects on the material characteristics and mechanical properties of plasma-sprayed pure HA and HA/20% YSZ coatings.Surface morphology and microstructural changes,relative element contents as well as phase transformations were analyzed by scanning electron microscopy,energy dispersive spectroscopy,and X-ray diffractometry.Both microhardness and Young’s modulus were measured.CaCO3 was found existing before and after the whole process of post-treatment.Peaks of impurity phases such as CaO,TCP,and TTCP of as-sprayed coatings were observed to disappear while HA peaks show a tendency of getting higher and wider over time.Surface morphology of SEM analysis presents a clear deposition behavior of ultrafine HA crystallized particles and cross-sectional analysis exhibits a dense and fine structure.Mechanical properties of HA/20%YSZ coatings are found to be significantly higher than those of pure HA coatings and both of which displayed an overall increase with the heating time,indicating enhanced performances.

High Osteoconductive Surface of Pure Titanium by Hydrothermal Treatment

Surface properties of Ti implants (especially surface hydrophilicity) influence biological responses at the interface between the bone tissue and the implant. However, only a little research reported the effect of surface hydrophilicity on osteoconductivity by in vivo test. We have investigated the surface characteristics and osteoconductivity of titanium implant produced by hydrothermal treatment using distilled water at temperature of 180°C for 3 h, and compared with as-polished and those of implants produced by anodizing in 0.1 M H2SO4 with applied voltage from 0 V to 100 V at 0.1 Vsˉ1 and anodizing followed by hydrothermal treatment. The relationship between hydrophilic surface and osteoconductivity in various surface modifications was examined by in vivo test. In order to maintain the hydrophilicity of the hydrothermal sample surface, it was kept in to the phosphate buffered saline solution (PBS) with 5 times concentration: 5PBS(-) in room temperature. The surface characteristics were evaluated by scanning electron microscopy, XRD, X-ray photoelectron spectroscopy, surface roughness and contact angle measurement using a 2 μL droplet of distilled water. In in vivo testing, the rod samples (Φ2 × 5 mm) were implanted in male rat’s tibiae for 14 days and the bone-implant contact ratio, RB-I, was used to evaluate the osteoconductivity in the cortical and cancellous bone parts, respectively. As a result, hydrothermal treatment without anodizing still produced a smooth surface like an initial surface roughness of as-polished samples, Ra/μm B-I = 50% in cortical bone part (about four times higher than as-polished Ti) were provided by only hydrothermal process without anodizing after immersing into 5PBS(-).

Effect of hydrothermal treatment on the carbon structure of Inner Mongolia lignite

Understanding the structural properties of lignite during hydrothermal treatment would aid in predicting the subsequent behavior of coal during the pyrolysis,liquefaction,and gasification processes.Here,hydrothermal treatment of Inner Mongolia lignite(IM)was carried out in a lab autoclave.The distribution of carbon in the lignite was monitored via solid 13C nuclear magnetic resonance spectroscopy,and the functional groups of oxygen in lignite were determined by Fourier transform infrared spectroscopy.The curve-fitting method was used to calculate the content of the functional groups quantitatively.The results show that hydrothermal treatment is an effective method for upgrading the lignite.The side chains of the aromatic ring in lignite are altered,while the main macromolecular structure remains nearly the same.The hydrothermal treatment of IM could be divided into three temperature-dependent stages.The first stage(<493 K)is the decomposition reaction of oxygen functional groups,where the O/C ratio decreases from 0.203 in raw IM to 0.185 for the IM treated at 493 K.In the second stage(493–533 K),hydrolysis of functional groups and hydrogen transfer between water and lignite occur.Here,the ratio of methylene to methyl increases from 0.871 in IM-493 to 1.241 for IM-533,and the content of quinone generates from the condensation of free phenol increased.The third stage(>533 K)involves breakage of the covalent bond,and the content of CH4 and CO in the emission gas clearly increase.

Influence of Hydrothermal Pre-Treatment of Coal Fly on the Synthesis of Belite Phase

In this paper, the results of an extensive investigation of hydrothermal pre-treatment for synthesizing belite phase from reactive mixtures （CaO/SiO2 molar ratio of 2） consisting of one waste kinds （bottom ash-BA or fly ash-FA） from fluidised brown coal combustion in Slovakian power plant and CaO （analytical grade reagent） addition are summarized. Changes in structure and phase composition of hydrothermally synthesized belite precursors and subsequent calcinated products were compared with those of starting mixtures. Based on XRD diffraction patterns, the formation of the new profiles corresponding to CSH phases with low degree of ordering as belite precursors after hydrothermal treatment was confirmed. Calcination of hydrotermally treated products at 900℃ led to transformation of CSH phases to wollastonite, belite and gehlenite phase. Differences in phase composition of products before and after calcination depend upon waste quality and precursor＇s synthesis conditions. Bottom ash isn＇t suitable as raw material for synthesizing belite phase because of high CaO content fixed in anhydrite form （44.1%）. Coal fly ash with low CaO content in anhydrite form （4.2%） and its hydrothermal treatment in combination with subsequent heating offer opportunities for the utilization of coal fly ash as raw material for belite production.

Optimization of Hydrothermal Treatment Parameters to Produce Chlorine-Free Alternative Solid Fuel from Plastic-Contained Municipal Solid Waste

An experimental study of the treatment of plastic-contained Japanese MSW （municipal solid waste） employing 1 ton capacity hydrothermal reactor to produce chlorine-free solid fuel has been performed. The system applies medium-pressure saturated steam at about 2 MPa in a stirred reactor for certain holding period. It was shown that the products exhibited organic chlorine conversion into inorganic chlorine, which can then be water washed. To obtain an optimal operating condition, the temperature and holding period was integrated into one parameter called RS （reaction severity）. It was found that to convert 75% organic chlorine in the MSW, the optimum RS number correlates to an operating temperature of about 225℃ and holding period of 90 min, or 235 ℃ for 60 min. Since hydrothermal treatment is a batch process, a shorter holding period is preferable to increase the number of batches and indirectly increase its processing capacity.

Reaction behaviour of Al_2O_3 and SiO_2 in high alumina coal fly ash during alkali hydrothermal process

The reaction behaviours of A1203 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to A1203 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 ~C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of A1203/SIO2 up to 2.19：1.

Facile hydrothermal synthesis of TiO_2-Ca P nano-films on Ti6Al4V alloy

Ti6Al4V alloy was subjected to hydrothermal treatment in the concentrated Ca3(PO4)2, Ca HPO4 and Ca(H2PO4)2 solutions for bioactive surface modification. The treated samples are covered by films composed of nano-particles with the size of 60-240 nm. Such film can also be grown on the strut surface of a Ti6Al4 V scaffold prepared by electron beam melting(EBM) technology. XPS analysis indicates that Ti element on the surface presents as TiO2, and Ca and P elements are in the form of calcium phosphate. XRD and Raman analyses show that the surface layer is composed of anatase TiO2 and hydroxyapatite. Potentiodynamic polarization test in a Ca-free Hank's balanced solution demonstrates that the treated sample has markedly improved corrosion resistance compared with the polished sample. The present work provides a bioactive surface modification method that is easily-operated, low-temperature, less corrosion, and applicable to porous Ti6Al4 V alloy for biomedical applications.

Degradation of PCDD/Fs in MSWI fly ash using a microwave-assisted hydrothermal process

In this work,microwave treatment was introduced to a hydrothermal treatment process to degrade PCDD/Fs(Polychlorinated dibenzo-p-dioxins and dibenzofurans)in municipal solid waste incineration(MSWI)fly ash.Three process additives(NaOH,Na2 HPO4,H2 O),temperatures(150℃,185℃,220℃)and reaction times(1 h,2 h,3 h)were investigated to identify their effect on the disposal of fly ash samples through orthogonal experiments.High-resolution gas chromatography–mass spectrometry(HRGC/MS)was applied to determine the PCDD/F concentrations in MSWI fly ash.The experimental results revealed that 83.7%of total PCDD/Fs was degraded.Reaction temperature was the most important factor for the degradation of the total PCDD/Fs.Both direct destruction and chlorination reactions(the chlorination degree of PCDFs increased)took part in the degradation of PCDD/Fs in fly ash,which was a new discovery.Several PCDD/F indexes determined by the concentration of indicative congeners were found to quantitatively characterize the dioxin toxicity of the fly ash.Furthermore,heavy metals in the fly ash sample were solidified using microwave-assisted hydrothermal treatment,which provided an experimental basis for the simultaneous disposal of dioxins and heavy metals.Thus,the microwave-assisted hydrothermal process should be considered for the future disposal of MSWI fly ash.

Luminescence properties of ZnS:Cu, Eu semiconductor nanocrystals synthesized by a hydrothermal process

ZnS：Cu, Eu nanocrystals with an average diameter of 80 nm are synthesized using a hydrothermal approach at 200 ℃. The photoluminescence （PL） properties of the ZnS：Cu, Eu nanocrystals before and after annealing, as well as the doping form of Eu, are studied. The as-synthesized samples are characterized by X-ray diffraction, scanning electron microscopy, inductively coupled plasma-atomic emission spectrometry, and the excitation and emission spectra （PL）. The results show that both Cu and Eu are indeed incorporated into the ZnS matrix. Compared with the PL spectrum of the Cu mono-doped sample, the PL emission intensity of the Cu and Eu-codoped sample increases and a peak appears at 516 nm, indicating that Eu3＋ ions, which act as an impurity compensator and activator, are incorporated into the ZnS matrix, forming a donor level. Compared with the unannealed sample, the annealed one has an increased PL emission intensity and the peak position has a blue shift of 56 nm from 516 nm to 460 nm, which means that Eu3＋ ions reduce to Eu2＋ ions, thereby leading to the appearance of Eu2＋ characteristic emission and generating effective host-to-Eu2＋ energy transfer. The results indicate the potential applications of ZnS：Cu, Eu nanoparticles in optoelectronic devices.

Characterization of Pr-CeO_2 Nano-crystallites Prepared by Low-temperature Combustion&Hydrothermal Synthesis

Pr-CeO2 Nano-crystalline red pigments were prepared by low-temperature combustion with a later hydrothermal treatment using Ce（NO3）3·6H2O and Pr6O11 as raw materials. The phase composition, coloring mechanism and morphology of pigments were analyzed by XRD, SEM, EDS and XPS. Results showed that Pr-CeO2 solid solution with a fluorite structure was obtained by the diffusion of Pr^＋3 into CeO2 crystal lattice during the synthesis process. XPS analysis indicated that Pr^＋3 substitutes Ce^＋4 in CeO2 and is compensated by oxygen vacancies. Compared with low-temperature combustion synthesis, the Pr-CeO2 pigments prepared with a subsequent hydrothermal treatment have an average grain size of about 16.70 nm, and the crystallinity and red tonality are improved.