Microwave-assisted Hydrothermal Treatment Research Articles

Magnetic biochar generated from oil-mill wastewater by microwave-assisted hydrothermal treatment for sonocatalytic antibiotic degradation

Magnetic biochar generated from oil-mill wastewater by microwave-assisted hydrothermal treatment for sonocatalytic antibiotic degradation

Biomass-Derived Co/MPC Nanocomposites for Effective Sensing of Hydrogen Peroxide via Electrocatalysis Reduction

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H2O2. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm−2 mM−1. In addition, the effect this sensor had on H2O2 detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H2O2 in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively.

Pressurized microwave-assisted hydrothermal treatment with various salts for efficient production of monosaccharides from rice straw

This study proposed a two-stage pressurized microwave hydrothermal treatment with a catalyst, followed by enzymatic saccharification, as a pretreatment method for efficiently converting cellulose and hemicellulose from rice straw into glucose and xylose. The use of various inorganic salts and dilute sulfuric acid as catalysts enhances sugar production. Using 1wt% sulfuric acid as a catalyst at 150°C for 5min for the first-stage and then 180°C for 5min for the second-stage yielded the highest sugar production from rice straw compared with other inorganic salts tested. The filtrate and enzymatic saccharification solution contained a total sugar of 0.434g/g-untreated rice straw (i.e. 0.302g-glucose/g-untreated rice straw and 0.132g-xylose/g-untreated rice straw). When inorganic salts such as NaCl, MgCl2, CaCl2, and FeCl3 were used as catalysts, the highest sugar yield of 0.414g/g-untreated rice straw (i.e. 0.310g-glucose/g-untreated rice straw and 0.104g-xylose/g-untreated rice straw) was obtained when using 1wt% FeCl3 at 170°C for 5min in the first-stage and 190°C for 5min in the second-stage, with a value close to that of 1wt% sulfuric acid. These findings suggest that two-stage treatment with a catalyst is a suitable pretreatment method for the production of glucose and xylose from rice straw owing to the different hydrolysis temperatures of cellulose and hemicellulose.

Blue pigment based on Ni-doped Zn2GeO4: Addressing structure and electronic properties by combining experiment and theory

Blue pigment based on Ni-doped Zn2GeO4: Addressing structure and electronic properties by combining experiment and theory

The effect of microwave-assisted hydrothermal treatment on physicochemical and functional properties of wheat, barley, and rye flours

The effect of microwave-assisted hydrothermal treatment on physicochemical and functional properties of wheat, barley, and rye flours

Nitrogen-doped carbon dots for 3D printed smartphone-assisted cascade visual detection of morin and aluminium ion, solid fluorescence ink

Nitrogen-doped carbon dots for 3D printed smartphone-assisted cascade visual detection of morin and aluminium ion, solid fluorescence ink

Microwave-Assisted Hydrothermal Treatment of Multifunctional Substituted Hydroxyapatite with Prospective Applications in Bone Regeneration.

Orthopedic bone graft infections are major complications in today's medicine, and the demand for antibacterial treatments is expanding because of the spread of antibiotic resistance. Various compositions of hydroxyapatite (HAp) in which Calcium (Ca2+) ions are substituted with Cerium (Ce3+) and Magnesium (Mg2+) are herein proposed as biomaterials for hard tissue implants. This approach gained popularity in recent years and, in the pursuit of mimicking the natural bone mineral's composition, over 70 elements of the Periodic Table were already reported as substituents into HAp structure. The current study aimed to create materials based on HAp, Hap-Ce, and Hap-Mg using hydrothermal maturation in the microwave field. This route has been considered a novel, promising, and effective way to obtain monodisperse, fine nanoparticles while easily controlling the synthesis parameters. The synthesized HAp powders were characterized morphologically and structurally by XRD diffraction, Dynamic light scattering, zeta potential, FTIR spectrometry, and SEM analysis. Proliferation and morphological analysis on osteoblast cell cultures were used to demonstrate the cytocompatibility of the produced biomaterials. The antimicrobial effect was highlighted in the synthesized samples, especially for hydroxyapatite substituted with cerium. Therefore, the samples of HAp substituted with cerium or magnesium are proposed as biomaterials with enhanced osseointegration, also having the capacity to reduce device-associated infections.

Metal dopant infused superhydrophobic aluminum surface through sustainable processing

Metal dopant infused superhydrophobic aluminum surface through sustainable processing

Mineral phase transition characteristics and its effects on the stabilization of heavy metals in industrial hazardous wastes incineration (IHWI) fly ash via microwave-assisted hydrothermal treatment

Toxic heavy metals in industrial hazardous waste incineration (IHWI) fly ash can be effectively stabilized by using microwave-assisted hydrothermal technology. However, few works have focused on the relationship between mineralogical conversion and stability of heavy metals of fly ash during hydrothermal process. This study investigated the effect of mineral phase transition process on the stabilization and migration behavior of heavy metals in IHWI fly ash using coal fly ash as silicon‑aluminum additive. Mineral composition analysis reveals that after microwave-assisted hydrothermal treatment (MAHT) of IHWI fly ash, zeolite-like minerals (e.g., tobermorite, katoite and sodalite), secondary aluminosilicate minerals (e.g., prehnite and anorthite) and other newly-formed minerals (e.g., wollastonite, pectolite and larnite) were found. The leaching concentrations of heavy metals (Cr, Ni, Cu, Zn, Cd and Pb) in IHWI fly ash decrease sharply after MAHT with the most obvious decreases in Cu, Pb and Zn. Spearman correlation analysis show significantly negative correlation between the content of zeolite-like minerals and the leaching concentrations of most heavy metals (e.g., Ni, Cu, Zn, Cd and Pb). These results suggest that the immobilization effects of heavy metals in IHWI fly ash can be effectively enhanced by promoting the formation of zeolite-like minerals during the MAHT. This study is expected to further promote the development of IHWI fly ash harmless treatment technology.

Carbon Dots-Based Fluorescence Assay for the Facile and Reliable Detection of Ag+ in Natural Water and Serum Samples.

In this report, red-emissive carbon dots (C-dots) were facilely prepared from o-phenylenediamine via microwave-assisted hydrothermal treatment. The C-dots demonstrated excitation wavelength-independent emission with maximums at 621 nm that could be effectively quenched by Ag+ via static quenching. This phenomenon was exploited to establish a sensitive fluorescence assay with a low detection limit (0.37 μM) and wide linear range (0-50 μM). In addition, this assay demonstrated excellent selectivity toward Ag+, free from the interference of 16 commonly seen metal ions. Most importantly, the assay demonstrated high reliability toward samples in deionized water, mineral water, lake water, and serum, which could indicate potential applications for Ag+ monitoring in complicated natural and biological environments.

Microwave-Assisted Extraction of Carrageenan from Sarcopeltis skottsbergii.

The development of greener processes for the sustainable utilization of raw materials is increasingly demanded for environmental and economic reasons. A rapid and chemical-free technique was proposed for the extraction of hybrid kappa/iota (6/4) carrageenan from Sarcopeltis (ex Gigartina) skottsbergii. After separation, carrageenans were analyzed by Fourier transform infrared attenuated total reflectance, high-performance size-exclusion chromatography, and rheology. Maximum carrageenan extraction yields up to 63-64% were obtained operating at 110 or at 160 °C, for 5-7 min considering the sum of the heating and cooling periods, but the extraction of the phenolic fraction was favored at 220 °C. The recovered carrageenan showed apparent viscous values around 103 mPa at the lowest tested shear rates (0.1 1/s) and could be suitable to formulate films. Furthermore, those carrageenans obtained under 140 °C showed gel characteristics without previous separation from the liquid extract, avoiding ethanolic precipitation and energy consumption. The antiradical properties correlated with the phenolic content in the liquid phase, but no influence of temperature on the reducing properties was observed. The microwave-assisted hydrothermal treatment could be an efficient tool without needing chemicals for the extraction of carrageenans, which showed adequate rheological properties for commercial uses.

Transformation characteristics of nitrogen, sulfur and chlorine during microwave-assisted hydrothermal treatment of excavated waste

Transformation characteristics of nitrogen, sulfur and chlorine during microwave-assisted hydrothermal treatment of excavated waste

Buckwheat grains treated with microwave radiation: Impact on the techno-functional, thermal, structural, and rheological properties of flour

The physical modification of buckwheat grain, a pseudocereal with great interest in gluten-free (GF) product development, using microwave-assisted hydrothermal treatment (MWT), was evaluated. Buckwheat grains were microwaved (8 min at 18W/g) at four moisture contents (MC): 13%, 20%, 25%, and 30%, maintained constant throughout the treatment using a hermetic container. The impact of MWT on the techno-functional and rheological properties of flour was significantly affected by the MC of the grains. The flour obtained from grains treated with 30% MC (MW-30) was the most modified, showing the highest water absorption capacity (+43%) and a dramatic reduction in its emulsifying activity to almost zero, indicating the loss of its protein functionality during treatment. Differential scanning calorimetry (DSC) revealed a delay in the gelatinisation temperature (+3.7 °C) with a significant reduction in the gelatinization enthalpy (−27%), which is compatible with a partial pre-gelatinization of the flour. In contrast, the lowest grain MC led to opposite effects on most of the flour properties measured. The most significant difference was its improved ability to form stable emulsions (ES) (+188%) and a significant, albeit moderate, increase in gel structural stability and tolerance to stress. Based on these results, MWT combined with the MC of grain during treatment may be a viable and effective alternative to modulate the techno-functional properties of buckwheat flour and improve its applicability in GF food formulations.

Fast and selective production of quercetin and saccharides from rutin using microwave-assisted hydrothermal treatment in the presence of graphene oxide

Rutin is a flavonoid glycoside, well-known for its antioxidant, anticarcinogenic, and cardioprotective properties. However, it exhibits lower bio absorptivity and bioactivity than its aglycon form, quercetin. Although liquid acid catalysts are conventionally utilized to obtain quercetin via rutin hydrolysis, the neutralization procedure is a major disadvantage owing to the added cost. In this study, graphene oxide (GO) was used as an alternative catalyst under microwave (MW) irradiation, owing to its easy separation from the reaction solution and high MW absorptivity, resulting in improved thermal efficiency. Two types of GOs were prepared (GO-HU using Hummer's method and GO-TO using Tour's method), and their catalytic performance for rutin hydrolysis was evaluated and compared. The highest rutin conversion (98.8%) and quercetin yield (81.9%) were obtained at 180°C when the reaction was conducted for 15min using 3mg of GO-TO and 2400ppm of initial rutin concentration in 50mL of water.

Removal mechanisms of phosphate from water by calcium silicate hydrate supported on hydrochar derived from microwave-assisted hydrothermal treatment

The discharge of phosphorus in water has led to the problems of eutrophication and waste of phosphorus resources. Here, calcium silicate hydrate supported on hydrochar derived from microwave-assisted hydrothermal treatment (w-CH/CSH) was developed for phosphate removal. The characterizations of w-CH/CSH were examined through scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, and specific surface area analyzer. Batch adsorption experiments were conducted to identify the adsorption characteristics of phosphate onto w-HC/CSH. Results showed that the best w-HC/CSH adsorbent was successfully prepared. The CSH was uniformly distributed on the hydrochar surface and the specific surface area (SSA BET ) of w-HC/CSH increased to 98.76 m 2 /g. The phosphate adsorption was governed by chemisorption on heterogeneous surfaces and could be better fitted by the pseudo-second-order and Freundlich model. The film diffusion and intraparticle diffusion were the rate-limiting process of phosphate adsorption. The underlying mechanisms were mainly attributable to the surface microprecipitation including Ca 3 (PO 4 ) 2 , Ca 8 H 2 (PO 4 ) 6 , Ca( H 2 PO 4 ) 2 , CaHPO 4 and Ca 5 (PO 4 ) 3 Cl, and the ligand exchange with the CaCO 3 and oxygen-containing functional groups. • Porous w-HC/CSH was prepared by microwave-assisted hydrothermal treatment. • Adsorption was better fitted by pseudo second order and Freundlich model. • Film diffusion and intraparticle diffusion governed the phosphate adsorption process. • Surface microprecipitation and ligand exchange were the main mechanisms of phosphate removal.

Synthesis of high-quality Na[sbnd]P1 zeolite from municipal solid waste incineration fly ash by microwave-assisted hydrothermal method and its adsorption capacity

The Si and Al in municipal solid waste incineration fly ash (MSWI FA) can be utilized for zeolite fabrication, which can improve the application value of the products. This study focuses on the fabrication of zeolite from MSWI FA by microwave-assisted hydrothermal (MH) treatment. The effects of magnetic stirring time, Na2SiO3 dosage, MH time, and NaOH solution concentration on the crystallization of zeolite NaP1 from MSWI FA are systematically analyzed. The synthetic products are analyzed through spectroscopic and mineralogical methods. The results show that zeolite NaP1 with high crystallinity (51.68 %) can be fabricated by magnetic stirring and MH treatment, and the cation exchange capacity (CEC) of the product can reach a value of 2.58 meq/g, which is approximately 133 times that of the CEC of MSWI FA. The Si/Al ratio plays a decisive role in the zeolite NaP1 synthesis, and a Na2SiO3 dosage of 30 wt% is adopted for zeolite NaP1 fabrication. A NaOH concentration of 1 M is sufficient for zeolite NaP1 synthesis. Additionally, the zeolite NaP1 content is found to obviously increase with increasing MH time from 0.5 h to 2 h. To demonstrate the feasibility of the method provided in this study, the optimal experimental condition is employed for various MSWI FAs, and zeolite NaP1 and analcime are fabricated successfully. The leachability of heavy metals for the synthetic products was evaluated, which met the requirements for pollution control. The BET surface area and total pore volume of zeolite NaP1 fabricated at optimal condition are 61.42 m2/g and 0.44 cm3/g, respectively. The adsorption capacity of zeolite NaP1 for Cu2+ ion and methylene blue are determined to be 84.65 mg/g and 84.55 mg/g, respectively, indicating zeolite NaP1 is a potential adsorbent for cation ion and dyes. This study provides an environmentally friendly scheme for the utilization of MSWI FA.

Synthesis and in situ sulfidation of molybdenum carbide MXene using fluorine-free etchant for electrocatalytic hydrogen evolution reactions

Synthesizing MXenes from Mn+1AXn (MAX) phases using hazardous hydrogen fluoride is a common and effective method. However, fluorine termination on the basal planes and edges of the resulting MXenes is undesirable for the electrocatalytic hydrogen evolution reaction (HER), while oxygen (O), hydroxyl (OH), and sulfur (S) termination favors this reaction. Herein, we unveil a simple fluorine-free exfoliation and two-step vulcanization method for synthesizing molybdenum sulfide-modified molybdenum carbide (MoS2/Mo2CTx MXene, T=OH, O, S) for the HER in alkaline medium. Microwave-assisted hydrothermal treatment of the MAX phase (Mo3AlC2) with sodium hydroxide-sodium sulfide as an etching solution and thioacetamide as a source of sulfide ions enabled the selective dissolution of the aluminum (Al) layer and sulfidation of the surface Mo atoms to form amorphous MoS2. Thus, the vulcanization of Mo2CTx MXene resulted in the formation of MoS2/Mo2CTx MXene. The MoS2 formed on the surface of Mo2CTx provided enhanced stability by preventing oxidation. MoS2/Mo2CTx exhibited enhanced electrocatalytic activity toward the HER, mainly due to the O, OH, and amorphous MoS2 functionalities. The MoS2 sites on the surface exhibited an overpotential of 110±7mV at a current density of 10mAcm-2 as a result of enhanced charge transfer and mass transfer. Thus, the sulfidation method demonstrated herein is capable of producing amorphous MoS2 structures on Mo2CTx MXene, which could be applied for the surface modification of other molybdenum-based nanomaterials or electrocatalysts to improve stability and enhance electrocatalytic activity.

Microwave-assisted hydrothermal treatment of soybean residue and chitosan: Characterization of hydrochars and role of N and P transformation for Pb(II) removal

• SB, CS, and different mass ratios (SB:CS) were treated to obtain HCs via Mw-HTT. • HCs were analyzed nd characterized to study N and P transformation. • Examined combined SB and CS effect on Pb(II) removal by isotherm and kinetic models. • N of CS and P of SB were transformed during Mw-HTT, assisting in Pb(II) adsorption. The beneficial utilization of biomass wastes and residues for environmental remediation is the focus of many research efforts towards environmental sustainability. In this study, agricultural residue (soybean, (SB)) and a biopolymer (chitosan, (CS)) were examined for enhanced heavy metals (HMs) removal. Specifically, SB, CS, and mixtures of SB and CS at different mass ratios (SB:CS) were treated to obtain hydrochars (HCs) via microwave-assisted hydrothermal treatment (Mw-HTT). Synthesized HCs were subsequently characterized by elemental analysis (EA), SEM/EDX, XRD, FT-IR, XPS, and sequential extraction to estimate nitrogen (N) and phosphorus (P) transformation during Mw-HTT. The N remained same in CS HCs and decreased in SB HCs based on EA results, and sequential extraction indicated that P decreased after Mw-HTT in SB and CS HCs. Lead (Pb(II)) adsorption was carried out using as-synthesized HCs, and experimental results were examined using standard adsorption isotherm and kinetic models. The R 2 value (≥ 0.960) with acceptable n and K f confirmed that Freundlich isotherm was suitable. For adsorption kinetics, pseudo-2nd-order model showed R 2 ≥0.94 and good agreement between calculated and actual adsorption capacities, providing insights into adsorption mechanisms for CS, SB, and SB:CS HCs. It was found that N and P transformed during Mw-HTT, which played a role in Pb(II) removal from solutions.

PVDF-TiO2 core-shell fibrous membranes by microwave-hydrothermal method: Preparation, characterization, and photocatalytic activity

A polyvinylidene fluoride (PVDF) - titanium dioxide (TiO2) core-shell composite nanofibrous membrane (CNM) with photocatalytic activity was obtained from the microwave-assisted hydrothermal treatment of an electrospun PVDF membrane. The effects of the precursor solution acidity, the heating temperature, and the treatment time on the structure and the photocatalytic performance were investigated. The CNM obtained from a 2 M precursor acidic solution showed the presence of nanofibers (NFs) with a proper core-shell structure, wherein a TiO2 smooth shell was uniformly covering the electrospun PVDF NFs core. The TiO2 crystallographic phase was found to be temperature-dependent, with the highest anatase content observed at 120 °C. The mean PVDF-TiO2 NFs diameter measured from SEM images and the TiO2 fraction of CNM calculated from TGA results showed an accumulation of TiO2 on the PVDF NFs surface as heating temperature and treatment time increased. The photo-oxidation capability of the as-prepared CNMs was evaluated by the photocatalytic decomposition of aqueous methyl orange solution at room temperature under UV-C irradiation. PVDF-TiO2 CNM exhibited a stable performance after five cycles of the MO degradation due to a strong connection between the TiO2 layer and the PVDF substrate. The implemented approach has been demonstrated to be a feasible method for the synthesis of core-shell PVDF-TiO2 fibrous membrane. The influence of hydrothermal process parameters on the structure and final properties of PVDF-TiO2 CNM was revealed through a detailed mechanism investigation.

Magnetic porous biochar with high specific surface area derived from microwave-assisted hydrothermal and pyrolysis treatments of water hyacinth for Cr(Ⅵ) and tetracycline adsorption from water

Magnetic porous water hyacinth-derived biochar (MPBCMW3) was synthesized via two-step Microwave (MW)-assisted processes. Characterization results not only testified high specific surface area (2097.50m2/g) of the MPBCMW3 assisted by MW-assisted pyrolysis, but also revealed its favorable magnetism derived from MW-assisted hydrothermal process. The MPBCMW3 possessed pH-dependent monolayer adsorption capacities of 202.61 and 202.62mg/g for Cr(VI) and TC with quick attainments of uptake equilibrium within 150 and 200min. Moreover, the Cr(VI) and TC uptake were substantially steady under the interference from multifarious co-existing ions with slight decline after three adsorption-desorption cycles. Furthermore, the MPBCMW3 was demonstrated to achieve excellent Cr(VI) binding primarily through complexation, electrostatic interaction, reduction and ion exchange, while presenting outstanding TC removal via pore filling, π-π stacking, hydrogen bonding force, electrostatic interaction and complexation. All these findings suggested the MPBCMW3 synthesized by MW-assisted processes as an excellent adsorbent for purification of Cr(VI) and TC-contaminated water.