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1.
Microb Cell Fact ; 23(1): 209, 2024 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-39054459

RESUMO

BACKGROUND: The presence of inorganic pollutants and heavy metals in industrial effluents has become a serious threat and environmental issues. Fungi have a remarkable ability to exclude heavy metals from wastewater through biosorption in eco-friendly way. Tannase plays an important role in bioconversion of tannin, a major constituent of tannery effluent, to gallic acid which has great pharmaceutical applications. Therefore, the aim of the current study was to exploit the potential of tannase from Aspergillus glaucus and fungal biomass waste for the bioremediation of heavy metals and tannin. RESULTS: Tannase from A. glaucus was partially purified 4.8-fold by ammonium sulfate precipitation (80%). The enzyme was optimally active at pH 5.0 and 40 °C and stable at this temperature for 1 h. Tannase showed high stability at different physiological conditions, displayed about 50% of its activity at 60 °C and pH range 5.0-6.0. Immobilization of tannase was carried out using methods such. as entrapment in Na-alginate and covalent binding to chitosan. The effects of Na-alginate concentrations on the beads formation and enzyme immobilization revealed that maximum immobilization efficiency (75%) was obtained with 3% Na-alginate. A potential reusability of the immobilized enzyme was showed through keeping 70% of its relative activity up to the fourth cycle. The best bioconversion efficiency of tannic acid to gallic acid by immobilized tannase was at 40 °C with tannic acid concentration up to 50 g/l. Moreover, bioremediation of heavy metal (Cr3+, Pb2+, Cu2+, Fe3+, and Mn2+) from aqueous solution using A. glaucus biomass waste was achieved with uptake percentage of (37.20, 60.30, 55.27, 79.03 and 21.13 respectively). The biomass was successfully used repeatedly for removing Cr3+ after using desorbing agent (0.1 N HCl) for three cycles. CONCLUSION: These results shed the light on the potential use of tannase from locally isolated A. glaucus in the bioremediation of industrial tanneries contained heavy metals and tannin.


Assuntos
Aspergillus , Biodegradação Ambiental , Biomassa , Hidrolases de Éster Carboxílico , Enzimas Imobilizadas , Metais Pesados , Taninos , Taninos/metabolismo , Taninos/química , Aspergillus/enzimologia , Aspergillus/metabolismo , Metais Pesados/metabolismo , Hidrolases de Éster Carboxílico/metabolismo , Enzimas Imobilizadas/metabolismo , Enzimas Imobilizadas/química , Concentração de Íons de Hidrogênio , Temperatura , Estabilidade Enzimática
2.
Molecules ; 28(1)2023 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-36615584

RESUMO

The separation of oil/water emulsions has attracted considerable attention for decades due to the negative environmental impacts brought by wastewater. Among the various membranes investigated for separation, polyvinylidene fluoride (PVDF) membranes have shown significant advantages of ease of fabrication, high selectivity, and fair pore distribution. However, PVDF membranes are hydrophobic and suffer from severe fouling resulting in substantial flux decline. Meanwhile, the incorporation of wettable substrates during fabrication has significantly impacted the membrane performance by lowering the fouling propensity. Herein, we report the fabrication of an iron-containing porphyrin (hemin)-modified multi-walled carbon nanotube incorporated PVDF membrane (HA-MWCNT) to enhance fouling resistance and the effective separation of oil-in-water emulsions. The fabricated membrane was thoroughly investigated using the FTIR, SEM, EDX, AFM, and contact angle (CA) analysis. The HA-MWCNT membrane exhibited a water CA of 62° ± 0.5 and excellent pure water permeance of 300.5 L/m2h at 3.0 bar (400% increment), in contrast to the pristine PVDF, which recorded a CA of 82° ± 0.8 and water permeance of 59.9 L/m2h. The hydrophilic HA-MWCNT membrane further showed an excellent oil rejection of >99% in the transmembrane pressure range of 0.5−2.5 bar and a superb flux recovery ratio (FRR) of 82%. Meanwhile, the classical molecular dynamics (MD) simulations revealed that the HA-MWCNT membrane had greater solvent-accessible pores, which enhanced water permeance while blocking the hydrocarbons. The incorporation of the hemin-modified MWCNT is thus an excellent strategy and could be adopted in the design of advanced membranes for oil/water separation.


Assuntos
Nanotubos de Carbono , Purificação da Água , Emulsões , Hemina , Membranas Artificiais , Purificação da Água/métodos
3.
Chem Rec ; 22(7): e202100230, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34757694

RESUMO

The continuous carbon dioxide (CO2 ) gas emissions associated with fossil fuel production, valorization, and utilization are serious challenges to the global environment. Therefore, several developments of CO2 capture, separation, transportation, storage, and valorization have been explored. Consequently, we documented a comprehensive review of the most advanced strategies adopted in metal-organic frameworks (MOFs) for CO2 capture and separation. The enhancements in CO2 capture and separation are generally achieved due to the chemistry of MOFs by controlling pore window, pore size, open-metal sites, acidity, chemical doping, post or pre-synthetic modifications. The chemistry of defects engineering, breathing in MOFs, functionalization in MOFs, hydrophobicity, and topology are the salient advanced strategies, recently reported in MOFs for CO2 capture and separation. Therefore, this review summarizes MOF materials' advancement explaining different strategies and their role in the CO2 mitigations. The study also provided useful insights into key areas for further investigations.


Assuntos
Estruturas Metalorgânicas , Adsorção , Dióxido de Carbono , Metais
4.
Surg Endosc ; 36(1): 328-335, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-33479836

RESUMO

BACKGROUND: One-anastomosis gastric bypass (OAGB) is an effective bariatric procedure that confers satisfactory weight loss and improvement in comorbidities. The present study aimed to compare OAGB with fixed bypass of the proximal 200 cm of small bowel and tailored bypass of the proximal 1/3 of bowel. METHODS: Patients with class II/III obesity underwent OAGB with either fixed bypass of the proximal two meters or tailored bypass of the proximal 1/3 of bowel. The main outcomes of the study were weight loss, improvement in comorbidities, complications, and changes in nutritional parameters after each technique. RESULTS: The present study included 80 patients (62 female) of a mean age of 41 years and mean body mass index (BMI) of 50.9 kg/m2. The tailored bypass group was followed by a significantly lower BMI and significantly higher excess weight loss and total weight loss at 6 and 12 months postoperatively. There was no significant difference between the two groups in terms of improvement in comorbidities. The fixed bypass group was associated with a significantly higher complication rate than the tailored bypass group (22.5 vs. 5%, P = 0.04). Both groups were associated with similar changes in the nutritional parameters at 12 months postoperatively, except for the higher serum albumin levels after the tailored bypass than the fixed bypass. CONCLUSIONS: OAGB with tailored bypass of the proximal one-third of bowel was associated with greater weight loss and comparable improvement in comorbidities as compared to fixed bypass of the proximal two meters of intestine.


Assuntos
Derivação Gástrica , Obesidade Mórbida , Adulto , Feminino , Derivação Gástrica/métodos , Humanos , Intestino Delgado/cirurgia , Obesidade Mórbida/cirurgia , Estudos Retrospectivos , Redução de Peso
5.
BMC Surg ; 22(1): 346, 2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36127722

RESUMO

BACKGROUND: Complex ventral hernias (VHs) represent a real challenge to both general and plastic surgeons. This study aims to compare Sublay Mesh-Only Repair to Posterior Component Separation "PCS" with Transversus Abdominis Release "TAR" in the treatment of complex ventral-wall hernias (VHs). METHODS: This a randomized, controlled, intervention, including two parallel groups: A; Sublay Mesh-Only Repair and Group B; "TAR". Consecutive patients of both genders aged between 18 and 65 years old with complex VHs presented at Mansoura University Hospitals including large-sized abdominal-wall hernia ≥ 10 cm in width, loss of domain ≥ 20%, multiple hernial defects, or recurrent hernias. Immuno-compromised patients, patients with liver impairment, or severe heart failure were considered an exclusion criterion. The primary outcome is the recurrence rate after 12-months following the procedure. RESULTS: Fifty-six patients were recruited in this study. There was no significant difference between both groups regarding recurrence. However, there was significant differences between both groups regarding seroma favoring mesh-only repair. CONCLUSIONS: Although TAR may be associated with longer operative times and more blood losses, these were not found to be statistically significant. Postoperative complication, except for seroma, and recurrence rates were comparable in both groups. Trail registration The study was registered on clicaltrials.gov "NCT04516031".


Assuntos
Hérnia Ventral , Músculos Abdominais/cirurgia , Adolescente , Adulto , Idoso , Feminino , Hérnia Ventral/cirurgia , Herniorrafia/métodos , Humanos , Masculino , Pessoa de Meia-Idade , Seroma , Telas Cirúrgicas , Adulto Jovem
6.
Chem Rec ; 21(7): 1771-1791, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33955166

RESUMO

Among thousands of known metal-organic frameworks (MOFs), the University of Oslo's MOF (UiO-66) exhibits unique structure topology, chemical and thermal stability, and intriguing tunable properties, that have gained incredible research interest. This paper summarizes the structural advancement of UiO-66 and its role in CO2 capture, separation, and transformation into chemicals. The first part of the review summarizes the fast-growing literature related to the CO2 capture reported by UiO-66 during the past ten years. The second part provides an overview of various advancements in UiO-66 membranes in CO2 purification. The third part describes the role of UiO-66 and its composites as catalysts for CO2 conversion into useful products. Despite many achievements, significant challenges associated with UiO-66 are addressed, and future perspectives are comprehensively presented to forecast how UiO-66 might be used further for CO2 management.

7.
Colorectal Dis ; 23(9): 2456-2465, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34042233

RESUMO

AIM: There is no standard method for the management of sacrococcygeal pilonidal disease (SPND); however, surgery remains the gold standard treatment. Wide surgical excision of the sinus is the traditional surgical treatment of SPND, yet it is associated with extended healing time and delayed recovery. This study aimed to compare the outcomes of sinus laser therapy (SiLaT) and sinus lay open in the management of SPND. METHODS: Patients with SPND who were treated with SiLaT or lay open were retrospectively reviewed. The main outcome measures were the success of surgery in terms of complete healing at 12 months postoperatively, time to complete healing, complications, operation time and quality of life (QoL). RESULTS: A total of 139 patients with a mean age of 25 years were included to the study. Sixty-two patients underwent SiLaT and 77 underwent lay open. Six patients experienced recurrence after SiLaT while there was no recorded recurrence after the lay open technique (P = 0.007). Sinus lay open had a shorter operation time than SiLaT (P < 0.0001). On the other hand, SiLaT was followed by a shorter healing time, lower incidence of delayed wound healing, better cosmetic outcome, and higher QoL scores compared to the lay open group. The complication rates were comparable between the two groups. CONCLUSION: Sinus lay open was associated with better success than SiLaT. On the other hand, SiLaT was associated with quicker healing, better cosmesis, better QoL and longer operation time. The complication rate of the two procedures was comparable.


Assuntos
Terapia a Laser , Seio Pilonidal , Adulto , Humanos , Recidiva Local de Neoplasia , Seio Pilonidal/cirurgia , Qualidade de Vida , Recidiva , Estudos Retrospectivos , Região Sacrococcígea , Resultado do Tratamento
8.
World J Surg ; 45(4): 1210-1221, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33481084

RESUMO

BACKGROUND: Treatment of anismus usually starts with biofeedback therapy and injection of botulinum toxin in the puborectalis muscle (PRM). Patients refractory to conservative treatment may require surgery. The present cohort study aimed to assess a combined technique of partial division of PRM and tailored lateral internal sphincterotomy (LIS) in treatment of anismus. METHODS: Patients with anismus who failed conservative treatments were assessed clinically and with high-resolution anal manometry (HRAM), EMG, defecography, and underwent combined partial division of PRM on one side and tailored LIS on the contralateral side. Main outcome measures were improvement in symptoms and quality of life, changes in HRAM and defecography postoperatively, complications, and patient satisfaction. RESULTS: A total of 73 patients (61 male) of a mean age of 37 years were included to the study. In total, 89% of patients showed a significant improvement in symptoms at 12 months postoperatively. The mean modified Altomare score decreased significantly (p < 0.0001) from 16.4 ± 1.7 to 6.6 ± 1 at 12 months postoperatively. There was a significant increase in the mental and physical components of quality of life at 12 months postoperatively. The numbers of patients with positive findings of anismus in postoperative defecography, EMG, and balloon expulsion test were significantly less than before surgery. The mean total satisfaction score was 86.5 ± 8.7. Five (6.5%) patients developed minor complications. CONCLUSION: Partial division of puborectalis muscle combined with LIS is an effective technique in the management of anal hypertonia-associated anismus with satisfactory results and low incidence of complications.


Assuntos
Esfincterotomia Lateral Interna , Adulto , Canal Anal/diagnóstico por imagem , Canal Anal/cirurgia , Estudos de Coortes , Constipação Intestinal , Defecação , Humanos , Masculino , Manometria , Hipertonia Muscular/etiologia , Diafragma da Pelve , Qualidade de Vida , Resultado do Tratamento
9.
Dis Colon Rectum ; 62(8): 980-987, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31162376

RESUMO

BACKGROUND: Complex anal fistula is one of the challenging anorectal conditions. Several treatments have been proposed for complex anal fistula, yet none proved to be ideal. OBJECTIVE: This randomized trial aimed to assess the efficacy of external anal sphincter-sparing seton in comparison with the conventional drainage seton in the treatment of complex anal fistula. DESIGN: This was a prospective, randomized, single-blind controlled study. SETTINGS: The study was conducted at the Colorectal Surgery Unit of Mansoura University Hospitals. PATIENTS: Adult patients of both sexes with complex anal fistula were recruited and evaluated with MRI before surgery. INTERVENTIONS: Patients were randomly divided into 2 groups; group 1 was treated with conventional drainage seton and group 2 was treated with external anal sphincter-sparing seton using a rerouting technique. MAIN OUTCOME MEASURES: The duration of healing, incidence of recurrence or persistence, postoperative pain, and complications including fecal incontinence were measured. RESULTS: Sixty patients (56 men) with a mean age of 43 years were included. Mean operation time in group 1 was significantly shorter than group 2 (29.8 ± 4.3 vs 43.8 ± 4.5 min; p < 0.0001). The mean pain score at 24 hours in group 1 was 8.1 ± 1.6 versus 5.3 ± 1.3 in group 2 (p < 0.0001). Five patients (17%) in group 1 experienced complications versus 2 (7%) in group 2. All of the patients in group 1 required a second-stage fistulotomy versus 2 patients (7%) in group 2 (p < 0.0001). Time to complete healing in group 1 was significantly (p < 0.0001) longer than group 2 (103 ± 47 vs 46 ± 18 d). Four patients (13%) in group 1 and 1 patient (3%) in group 2 experienced persistence or recurrence of anal fistula (p = 0.35). LIMITATIONS: This was a single-center study with relatively small numbers in each group. CONCLUSIONS: Patients treated with external anal sphincter-sparing seton after rerouting of the fistula tract achieved quicker healing and less postoperative pain than those with conventional drainage seton. Postoperative complication and recurrence rates were comparable in both groups. See Video Abstract at http://links.lww.com/DCR/A963. TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT03636997 (https://clinicaltrials.gov/ct2/show/NCT03636997).


Assuntos
Canal Anal/cirurgia , Procedimentos Cirúrgicos do Sistema Digestório/métodos , Drenagem/métodos , Tratamentos com Preservação do Órgão/métodos , Fístula Retal/cirurgia , Técnicas de Sutura/instrumentação , Suturas , Adulto , Egito/epidemiologia , Feminino , Seguimentos , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/epidemiologia , Estudos Prospectivos , Recidiva , Método Simples-Cego , Resultado do Tratamento , Adulto Jovem
10.
J Surg Res ; 223: 174-182, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29433871

RESUMO

BACKGROUND: Sacrococcygeal pilonidal disease (SPND) is a common surgical condition with a multitude of surgical treatments. The aim of this study was to compare the outcome of modified Limberg flap (MLF) and that of rotational gluteal flap (RGF) in treatment of SPND. MATERIALS AND METHODS: This was a retrospective case-controlled study involving adult patients of both genders who were treated with either MLF or RGF for SPND. The main outcomes of the study were the recurrence of SPND, complications, operation time, hospital stay, time of healing, time to return to daily activities, and cosmetic outcomes. RESULTS: A total of 189 (143 males) patients with a mean age of 23.5 y were included. Ninety-five patients were treated with RGF (cases), and 94 were treated with MLF (controls). Both the groups were matched regarding age, gender, body mass index, and disease severity. The operation time of RGF was longer than that of MLF (P < 0.0001). No significant difference in recurrence was noted between RGF and MLF (3.1% versus 7.4%, P = 0.21). RGF had lower complication rate than MLF (17.9% versus 40.4%; P = 0.001). Time to return to work was similar in both the groups. RGF conferred significantly better cosmetic outcomes than MLF. CONCLUSIONS: Both RGF and MLF achieved comparable, low recurrence rates. Although the operation time of RGF was significantly longer than that of MLF, the RGF had shorter healing time; lower complication rate, particularly seroma formation; and better cosmetic appearance.


Assuntos
Seio Pilonidal/cirurgia , Retalhos Cirúrgicos , Adolescente , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Duração da Cirurgia , Satisfação do Paciente , Estudos Retrospectivos , Rotação , Região Sacrococcígea , Retalhos Cirúrgicos/efeitos adversos , Cicatrização , Adulto Jovem
11.
Int J Colorectal Dis ; 33(10): 1461-1467, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29779044

RESUMO

BACKGROUND: Lateral internal anal sphincterotomy (LIS) is considered the treatment of choice for chronic anal fissure. This study aimed to compare the outcome of standard LIS and posterolateral internal sphincterotomy (PLIS) at 5 o'clock position as regards healing of anal fissure, improvement in symptoms, and complications. METHODS: Patients with chronic anal fissure were randomly allocated to one of two groups; group I underwent PLIS and group II underwent LIS. Patients were compared regarding the duration of healing of anal fissure, improvement in anal pain as recorded by visual analogue scale (VAS), complications, particularly fecal incontinence (FI) and changes in the anal pressures. RESULTS: Eighty (49 females) patients were included to this trial. The mean age of patients was 35.5 years. The duration of healing was significantly shorter in group I than in group II (4.1 ± 1.7 vs 5.8 ± 1.4 weeks; p < 0.0001). Group I achieved significantly lower pain score at 1 month postoperatively than group II (1.1 ± 0.9 vs 1.7 ± 0.98; p = 0.005). Two (2.5%) of group I patients and six (10%) of group II patients experienced minor FI postoperatively. The postoperative reduction in the mean resting anal pressure in group I was significantly higher than that in group II. CONCLUSION: Time to complete healing was significantly shorter and pain score was significantly lower after PLIS than after LIS which can be due to more reduction in the resting anal pressure after PLIS. Continence disturbances occurred after PLIS less frequently than after LIS; however, no significant differences between the two techniques were noted. TRIAL REGISTRATION: www.clinicaltrials.gov NCT03426449.


Assuntos
Fissura Anal/cirurgia , Esfincterotomia Lateral Interna , Adulto , Canal Anal/cirurgia , Doença Crônica , Feminino , Humanos , Masculino , Estudos Prospectivos , Resultado do Tratamento
13.
Prenat Diagn ; 37(8): 793-801, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28623846

RESUMO

OBJECTIVE: The aim of this work is to develop an efficient, user-friendly, time-saving computer software program specified with prenatal diagnosis, based solely on ultrasound findings provided by the sonographer. MATERIALS AND METHOD: Sonographyic computer-assisted diagnosis (SonoCAD) program was developed in four phases. Phase I: data gathering phase. Phase II: the software development phase in which the source code of the software was developed. Phase III: system testing phase that was divided into two steps: alpha testing phase, in which 20 syndromic scenarios were supplied to the software and the beta testing phase, in which the performance of SonoCAD was compared with the performance of the already established web site phenotip.com launched in 2014. Phase IV: the refining phase. RESULTS: In 92% of the syndromes provided, SonoCAD was capable of providing the correct diagnosis, while only in 53.3% of the syndromes phenotip.com was capable of providing the correct diagnosis. DISCUSSION AND CONCLUSION: Sonographyic computer-assisted diagnosis is an efficient, properly functioning, time-saving software that could be utilized by all who are involved in prenatal diagnosis. SonoCAD was found to be more efficient and more accurate in generating a correct diagnosis when compared with the already available website phenotip.com having the same functionality. © 2017 John Wiley & Sons, Ltd.


Assuntos
Doenças Fetais/diagnóstico por imagem , Processamento de Imagem Assistida por Computador , Ultrassonografia Pré-Natal , Diagnóstico Diferencial , Feminino , Humanos , Gravidez , Software
16.
Chem Asian J ; 19(16): e202301129, 2024 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-38403850

RESUMO

In this study, we employed a rapid and efficient microwave method to synthesize Metal-Organic Framework (MOF-303), which was subsequently embedded onto Palladium/Carbon (Pd/C) electrodes. The resulting hybrid material, Pd/C@MOF-303, was thoroughly characterized, and its performance in the Hydrogen Evolution Reaction (HER) was systematically investigated. The Pd/C@MOF-303 composite exhibited remarkable improvements in HER performance compared to the unmodified Pd/C electrode. At a benchmark current density of 10 mA cm-2, the overpotentials for Pd/C and Pd/C@MOF-303 were measured at 185 mV and 175 mV, respectively. This reduction in overpotential highlights the superior catalytic activity of the Pd/C@MOF-303 hybrid material in facilitating the HER. Furthermore, the Pd/C@MOF-303 electrode demonstrated enhanced HER activity, increased mass activity, and excellent charge transfer rates compared to its unmodified counterpart, Pd/C. The findings underscore the significance of the hydrophilic MOF-303 in tailoring the surface characteristics of electrocatalysts, thereby offering insights into the design principles for advanced materials with superior performance in electrochemical applications.

17.
ACS Omega ; 9(19): 21580-21586, 2024 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-38764626

RESUMO

Efficient hydrogen storage is essential for its use as a sustainable energy carrier. Diatomaceous earth, a high-surface-area siliceous geomaterial, shows potential as a physisorption material for hydrogen storage. This study analyzes diatomaceous earth's long-term characteristics when subjected to high-pressure hydrogen injection. The diatomaceous earth was subjected to a hydrogen pressure of 1200 psi for a period of 80 days at room temperature. Neither notable morphological or mineralogical changes were observed. Nevertheless, there was a slight reduction in fine particles and a slight increase in larger particles. The Brunauer-Emmett-Teller (BET) surface area decreased slightly with a significant decrease in pore width. However, the hydrogen adsorption at 77 K temperature was increased significantly (45.5%) after the hydrogen storage test. Moreover, there was a delayed release of molecular water as the temperature increased. These changes suggest that a condensation reaction has occurred involving some of the opal-A silanol groups (Si-O-H), producing molecular water. Bonding through siloxane bridges (Si-O-Si) results in a significant decrease in pore width and increased hydrophobicity (i.e., the interaction between diatomaceous surface and H2 was increased), thereby enhancing hydrogen adsorption capacity. These findings indicate that diatomaceous earth holds promise as a material for hydrogen storage, with the potential for its hydrogen adsorption capacity to improve over time.

18.
ACS Omega ; 8(39): 36228-36236, 2023 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-37810635

RESUMO

CO2 capture is a useful strategy for controlling the risks associated with global warming. The design of an adsorbent is essential for clean and potentially energy-efficient adsorption-based carbon capture processes. This study reports a facile and moderately temperature single-stage combined pyrolysis and activation strategy for the synthesis of nitrogen-doped carbons for high-performance CO2 capture. Using nitrogen-rich Albizia procera leaves as the precursor and carrying out single-stage pyrolysis and activation at temperatures of 500, 600, and 700 °C in the presence NaHCO3 as an activating agent, carbons with different surface characteristics and ultrahigh weight percentage (22-25%) of nitrogen were obtained. The subtle differences in surface characteristics and nitrogen content had a bearing on the CO2 adsorption performance of the resultant adsorbents. Outstanding results were achieved, with a CO2 adsorption capacity of up to 2.5 mmol/g and a CO2 over N2 selectivities reaching 54. The isotherm results were utilized to determine the performance indicators for a practical vacuum swing adsorption process. This study provides a practical strategy for the efficient synthesis of nitrogen-doped carbons for various adsorption applications.

19.
Front Chem ; 11: 1265324, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37744064

RESUMO

In this article, newly designed 3D porous polymers with tuned porosity were synthesized by the polycondensation of tetrakis (4-aminophenyl) methane with pyrrole to form M1 polymer and with phenazine to form M2 polymer. The polymerization reaction used p-formaldehyde as a linker and nitric acid as a catalyst. The newly designed 3D porous polymers showed permanent porosity with a BET surface area of 575 m2/g for M1 and 389 m2/g for M2. The structure and thermal stability were investigated by solid 13C-NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA). The performance of the synthesized polymers toward CO2 and H2 was evaluated, demonstrating adsorption capacities of 1.85 mmol/g and 2.10 mmol/g for CO2 by M1 and M2, respectively. The importance of the synthesized polymers lies in their selectivity for CO2 capture, with CO2/N2 selectivity of 43 and 51 for M1 and M2, respectively. M1 and M2 polymers showed their capability for hydrogen storage with a capacity of 66 cm3/g (0.6 wt%) and 87 cm3/g (0.8 wt%), respectively, at 1 bar and 77 K. Molecular dynamics (MD) simulations using the grand canonical Monte Carlo (GCMC) method revealed the presence of considerable microporosity on M2, making it highly selective to CO2. The exceptional removal capabilities, combined with the high thermal stability and microporosity, enable M2 to be a potential material for flue gas purification and hydrogen storage.

20.
Polymers (Basel) ; 15(11)2023 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-37299274

RESUMO

The design of novel porous solid sorbents for carbon dioxide capture is critical in developing carbon capture and storage technology (CCS). We have synthesized a series of nitrogen-rich porous organic polymers (POPs) from crosslinking melamine and pyrrole monomers. The final polymer's nitrogen content was tuned by varying the melamine ratio compared to pyrrole. The resulting polymers were then pyrolyzed at 700 °C and 900 °C to produce high surface area nitrogen-doped porous carbons (NPCs) with different N/C ratios. The resulting NPCs showed good BET surface areas reaching 900 m2 g-1. Owing to the nitrogen-enriched skeleton and the micropore nature of the prepared NPCs, they exhibited CO2 uptake capacities as high as 60 cm3 g-1 at 273 K and 1 bar with significant CO2/N2 selectivity. The materials showed excellent and stable performance over five adsorption/desorption cycles in the dynamic separation of the ternary mixture of N2/CO2/H2O. The method developed in this work and the synthesized NPCs' performance towards CO2 capture highlight the unique properties of POPs as precursors for synthesizing nitrogen-doped porous carbons with a high nitrogen content and high yield.

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