Preparation of bio-based porous material with high oil adsorption capacity from bio-polyurethane and sugarcane bagasse

This work presents the fabrication of bio-based porous material for highly efficient removing of oil from oil/water system. The sunflower oil-based polyol was synthesized and then used to replace the petro-polyol in the simultaneous preparation of a sugarcane bagasse-polyurethane composite (SC-PU composite) by inserting sugarcane fiber filler into the PU matrix. The bio-polyol was obtained from sunflower oil with a hydroxyl number of 182 mg KOH g-1, and functionality of 3.5 OH groups per mol. The bio-polyol and the newly designed bio-based SC-PU composite were characterized by NMR, FT-IR and SEM analysis. The effect of several parameters such as bio-polyol/petro-polyol ratio, dosage of adding sugarcane fiber and size of filler particles on oil adsorption capacity of a new sorbent material were also investigated. Oil sorption capacity of the newly designed sorbent was relatively high, up to 15.2 g g-1 when 20% sugarcane bagasse with a particle size of 1 mm was added into the bio-polyurethane matrix. This is nearly four times higher than that of neat PU foam without the biomass filler and lignocellulosic materials. This finding demonstrated the importance of selecting the right components to fabricate a cost-effective, highly renewable and biodegradable sorbent with high oil-water separation efficiency, reducing the use of chemicals from fossil sources.

Improving electrochemical performance of hybrid electrode materials by a composite of nanocellulose, reduced oxide graphene and polyaniline

Novel ternary composites of polyaniline (PANI), reduced graphene oxide (RGO), and cellulose nanofibers (CNFs) are prepared by a chemical method for hybrid supercapacitors. CNFs were extracted from sugarcane bagasse waste in sugar production, by physicochemical processes. The composites were investigated as electrode-active materials for hybrid supercapacitors. The obtained results revealed that the presence of RGO and CNFs in the composites led to enhanced electrochemical performances, such as capacitance, rate capability, and long-term cyclability of the composite. The optimal composite of CNFs/RGO/PANI with a weight ratio of 4/16/80 can deliver the highest specific capacitance at 566.2 F g^-1 under an applied current of 1 A g^-1. After 1000 cycles of repetitive charge and discharge, the optimal composite retains 85.4% of its initial capacitance, whereas the PANI electrode obtained only 36.7% under the same conditions. Moreover, the supercapacitive performance is also strongly dependent on the component of the ternary composites. Overall, the composite is a promising material for hybrid supercapacitors; and the CNF component is a renewable material and a product of waste materials.

The prevalence of self-reported anxiety, depression, and associated factors among Hanoi Medical University’s students during the first wave of COVID-19 pandemic

Background

Medical students are known to have higher levels of these issues than the general population but in Vietnam the effects of the pandemic on medical student mental health was not documented.

Objectives

To estimate the prevalence and identify factors associated with self-reported anxiety disorder, depression, and perception of worsening mental health among Vietnamese medical students during the COVID-19 pandemic.

Method

A cross-sectional study was conducted from April 7^th to 29^th, 2020. All students in Doctor of General Medicine, Doctor of Preventive Medicine, and Bachelor of Nursing tracks at Hanoi Medical University (3672 students) were invited to participate. Data were collected using an online questionnaire including demographic characteristics, Generalized Anxiety Disorder 7 items, Patient Health Questionnaire 9 items, Fear of COVID-19 scale, and question about worsening mental health status. Robust Poisson regression was used to assess the association between mental health status and associated factors.

Results

Among 1583 students (43.1% response rate), the prevalence of students screened positive for anxiety disorder was 7.3%(95%C.I.:6.0–8.7), depression was 14.5%(95%C.I.:12.8–16.3), and perceiving worsening mental health was 6.9%(95%C.I.:5.7–8.3). In multivariable regression models, significant factors associated with self-reported anxiety disorder included being male (PR = 1.99,95%C.I.:1.35–2.92), difficulty in paying for healthcare services (PR = 2.05,95%C.I.:1.39–3.01), and high level of fear of COVID-19 (Q3:PR = 2.36,95%C.I.:1.38–4.02 and Q4:PR = 4.75,95%C.I.:2.65–8.49). Significant factors associated with self-reported depression were difficulty in paying for healthcare services (PR = 1.78,95%C.I.:1.37–2.30), and high level of fear of COVID-19 (Q3:PR = 1.41,95%C.I.:1.02–1.95 and Q4:PR = 2.23,95%C.I.:1.51–3.29). Significant factors associated with perceived worsening mental health status included having clinical experience (PR = 1.83,95%C.I.:1.17–2.88) and having atypical symptoms of COVID-19 (PR = 1.96,95%C.I.:1.31–2.94).

Conclusion

The prevalence of self-reported depression, anxiety disorder, and worsening mental health among Vietnamese students during the first wave of COVID-19 was lower than in medical students in other countries. Further investigation is needed to confirm this finding.

Preparation of Metal-Loaded ZSM-5 Zeolite Catalyst and Its Catalytic Effect on HMF Production from Biomass

This research work presented the preparation of metal-loading ZSM-5 zeolite catalyst by loading Cu and Cr ions into the ZSM-5 zeolite particles using ion exchange method. Technical conditions of ion exchange processes were investigated to find suitable process for preparation of modified zeolite. The as-obtained zeolite catalyst was then applied for the transformation reaction of biomass-derived glucose into 5-hydroxymethyl furfural (HMF). Glucose hydrolysate that achieved from enzymatic hydrolysis of rice straw was used as feedstock for transformation reaction using Cu-Cr/ZSM-5 catalyst. This metal-loading zeolite exhibited good catalytic activity for lignocellulosic conversion to HMF, a valuable renewable green chemical. The content of loading metals in the zeolite catalyst affected significantly on the HMF yield. Moreover, the influence of transformation conditions such as solvent, temperature, catalyst dosage, and reaction time was investigated. According to the results, the optimum condition leading to the highest yield of HMF of 49.5 ± 0.5% was established. The as-prepared Cu-Cr/ZSM-5 zeolite catalyst showed impressive performance and can be considered a promising catalyst for the transformation of biomass-derived glucose to HMF.

Pretreatment of coir lignocellulose for preparation of a porous coir-polyurethane composite with high oil adsorption capacity

In this present work, different treatment methods of coir biomass were investigated to improve the oil sorption capacity. The treated coir material was then used to fabricate an efficient porous coir–polyurethane composite sorbent by incorporating coir into a polyurethane matrix. The new composite possessed an open cell structure with high porosity and high oil sorption efficiency. The suitable technical parameters of the coir treatment process were selected as: hot water treatment at 170 °C for 120 minutes. After treatment under this suitable condition, treated coconut fiber exhibited an oil adsorption capacity of 4.1 g g⁻¹, with an increase of 78.3% compared to that of the original coconut fiber. Furthermore, the application of the as-fabricated porous composite sorbent for oil treatment was examined under various conditions. It was observed that the oil uptake capacity of the new composite sorbent was high, up to 15.2 g g⁻¹ when 20% treated coir material with a particle size of 1 mm was added into the polyurethane matrix. Several advantages of the new porous composite sorbent obtained from coir biomass and polyurethane such as low cost, being eco-friendly, ready availability and high buoyancy make it an efficient sorbent material for oil spill treatment.

An efficient porous coir–polyurethane composite with high porosity and high oil sorption efficiency has been successfully prepared by incorporating coir into a polyurethane matrix.

Dry gel synthesis of hierarchical ZSM-5 zeolite using hydroxyl propyl methyl cellulose (HPMC) as a mesoporogen and its catalytic activity in alkylation reactions

In this work, a “green” and facile method for synthesis of hierarchical ZSM-5 zeolite was presented by combination of a bio-mesoporogen and a dry gel conversion (DGC) process. ZSM-5 zeolite with high hierarchy factors and excellent mesoporosity was synthesized by adding hydroxypropylmethylcellulose (HPMC), which originated from cellulose biomass, to a zeolitic synthetic gel. The obtained zeolite samples were analyzed by X-ray diffraction (XRD), nitrogen adsorption–desorption (BET) and scanning electron microscopy (SEM) to determine their properties. The influence of crystallization time on the crystallinity of ZSM-5 zeolite was investigated. Moreover, the results showed that HPMC as a pore directing agent is an important factor for the formation of hierarchical zeolite with high mesoporosity. The as-prepared ZSM-5 sample with high pore volume, large surface area and abundant accessible acid sites, which seriously improves diffusion efficiency and catalytic activity, exhibited high catalytic performance in the benzylation reaction.

A “green” and facile method for synthesis of hierarchical ZSM-5 zeolite was presented using a combination of a bio-mesoporogen and a dry gel conversion (DGC) process.

Production of 5-hydroxymethylfurfural (HMF) from rice-straw biomass using a HSO3–ZSM-5 zeolite catalyst under assistance of sonication

This work studied the application of sulfonated ZSM-5 zeolite, a bi-functional catalyst for conversion of biomass-derived glucose to HMF. Glucose hydrolysate was obtained by enzymatic hydrolysis of rice straw, that was pretreated by sodium hydroxide. Glucose hydrolysate was then subjected to a transformation reaction to achieve HMF using HSO₃–ZSM-5 zeolite under the assistance of sonication. The reaction conditions including solvent, temperature, catalyst dosage and reaction time were studied. Suitable conditions, which gave the highest yield of HMF of 54.1% have been found. The HSO₃–ZSM-5 zeolite presented a high catalytic efficiency for conversion of glucose to HMF, an important and useful intermediate in the chemical industry.

A porous HSO₃–ZSM-5 zeolite was successfully synthesized and applied for conversion of biomass-derived glucose to HMF.

Influence of the acidity of solid catalyst HSO3-ZSM-5 on the hydrolysis of pretreated corncob

This work aimed to investigate the application of a solid acid catalyst, a replacement for mineral acids or enzymes, to biomass conversion for further applications. Sulfonated zeolite, HSO₃-ZSM-5, was successfully synthesized and characterized by several analysis techniques. The obtained catalyst showed high activity and efficiency in the hydrolysis of pretreated corn cob. Moreover, the acidity of the zeolite product positively influenced the biomass conversion. The influences of reaction parameters such as catalyst loading, reaction time and temperature on the hydrolysis were also established. Under suitable conditions, a hydrolysis yield of ∼54% was achieved. This recyclable solid acid catalyst provided a promising potential for applications in many industrially important hydrolysis processes of biomass.

The influence of acidity of HSO₃-ZSM-5 zeolite on biomass hydrolysis was investigated.

Selective isomerization of epoxides using magnetically recyclable ZSM-5 zeolite catalyst

The magnetically recyclable ZSM-5 zeolite (MZZ) with high catalytic activity, high efficiency in separation, recycling and long lifetime for epoxide isomerization reaction was presented.

Efficient and continuous monoacylation with superior selectivity of symmetrical diamines in microreactors

Efficient and continuous monoacylation of symmetrical diamines performed in microreactors yielded superior selectivity to that predicted by statistical considerations. It is highly valuable that the kinetically controlled product in high yields was achieved without any special catalyst at ambient temperature.

An inorganic-organic diblock copolymer photoresist for direct mesoporous SiCN ceramic patterns via photolithography

A high resolution negative-tone-type of inorganic-organic diblock copolymer photoresist was synthesized as a novel precursor for simple and direct fabrication of SiCN ceramic mesoporous patterns with ordered nanoscale pores by using a "top-down" photolithographic technique and the subsequent sacrificial processes of a "bottom-up" self-assembled nanostructure.

Droplet synthesis of well-defined block copolymers using solvent-resistant microfluidic device

Well-defined diblock copolymers were synthesized via an exothermic RAFT route by a droplet microfluidic process using a solvent-resistant and thermally stable fluoropolymer microreactor fabricated by a non-lithographic embedded template method. The resulting polymers were compared to products obtained from continuous flow capillary reactor and conventional bulk synthesis. The droplet based microreactor demonstrated superior molecular weight distribution control by synthesizing a higher molecular weight product with higher conversion and narrow polydispersity in a much shorter reaction time. The high quality of the as-synthesized block copolymer PMMA-b-PS led to a generation of micelles with a narrow size distribution that could be used as a template for well-ordered mesoporous silica with regular frameworks and high surface areas.

[Hyperoxia test during attempts to withdraw artificial ventilation]

A 30 minute test of hyperoxia (10 l.min-1) was conducted in patients (n = 21) with chronic obstructive lung disease during the weaning trials from mechanical ventilation. Two groups were formed according to whether the occlusion pressure at 100 ms (PO.1), index of central stimulation, decreased or not during the test. The first group lowered PO.1 and increased PaCO2 by decreasing VE (minute-ventilation), VA (alveolar ventilation) and increasing the VD/VT ratio; the others had a lower PO.1 and did not modify it after administration of 02 despite a lowered PaO2 initially identical to that in the first group. They held PaCO2 constant by increasing VE and by maintaining VA in relationship with an improvement in diaphragm contractility and/or a better response to hypercapnia stimulus. All the patients is this group were successfully weaned eight days after the study period.

Triceps to biceps transfer for established brachial plexus palsy

We have reviewed seven patients who had triceps transfer after an old brachial plexus injury. All patients had a useful functional improvement with a good range of powerful elbow flexion; five patients could manage to bring their hand to their mouth. The basis of patient selection and the relative advantages of triceps transfer are discussed.

Diaphragmatic fatigue and breathing pattern during weaning from mechanical ventilation in COPD patients

The medium-term outcome of weaning from mechanical ventilation in COPD patients is not easy to anticipate because a respiratory fatigue may eventually develop. We evaluated the diaphragmatic function and the breathing pattern during 40 weaning trials on 15 patients ventilated after acute respiratory failure. We formed two groups according to the success (group B, n = 18) or failure (group A, n = 19) of the medium-term attempt (group A/less than 10 hours; group B/more than 12 hours). Provided the patients showed the classic weaning criteria (tidal volume greater than 5 ml/kg, respiratory frequency less than 30 breaths per minute, PaO2 greater than 50 mm Hg), the study of the breathing pattern did not allow differentiation between the groups. However, the transdiaphragmatic pressure (Pdi) and the Pdimax, which gave an indication of the power of diaphragm contraction, dropped early in the group that could not stand weaning, with an increase in the Pdi/Pdimax ratio. In addition, this same group showed a diaphragmatic dysfunction attested for by a frequent negative gastric pressure associated with or shortly preceded by an abdominal paradoxic motion.