Activated carbon derived from rice husk by NaOH activation and its application in supercapacitor

AbstractFour activated carbon (AC) samples prepared from rice husk under different activation temperatures have been characterized by N2 adsorption–desorption isotherms, thermogravimetric analysis (TGA–DTA), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The specific surface area of AC sample reached 2681m2g−1 under activation temperature of 800°C. The AC samples were then tested as electrode material; the specific capacitance of the as-prepared activated carbon electrode was found to be 172.3Fg−1 using cyclic voltammetry at a scan rate of 5mVs−1 and 198.4Fg−1 at current density 1000mAg−1 in the charge/discharge mode

SYNTHESIS, CHARACTERIZATION AND ELECTROCHEMICAL PERFORMANCE OF ACTIVATED CARBON SUPPORTED MnO2 FOR ELECTROCHEMICAL CAPACITOR

MnO2 was synthesized by adding activated carbon into KMnO4 solution and stirred in a magnetic or ultrasonic stirrer. The obtained MnAC samples were characterized by means of XRD, TGA, TPR-H2, SEM and BET. All samples are amorphous and have porous structure. MnAC-M prepared by magnetic stirring have higher manganese content, earlier reduction temperature, smoother surface area while MnAC-U prepared by ultrasonic stirring have larger specific surface area and pore volume

Preparation of Pore-Size Controllable Activated Carbon from Rice Husk Using Dual Activating Agent and Its Application in Supercapacitor

Activated carbons prepared from rice husk by chemical activation with dual activation agents, KOH and NaOH, have been studied and characterized by BET, SEM, EDX, FTIR, Boehm titration, Raman, and TGA. It was found that the KOH/NaOH impregnation ratio plays an important role on textural properties of AC. At the same amount of total alkali hydroxide, the KOH/NaOH ratio higher than 1.33 resulted in larger specific surface area (2990∼3043 m2·g−1), microporous surface area (2747∼2831 m2·g−1), and higher micropore volume (1.4250∼1.4316 cm3·g−1). The as-prepared samples exist in the form of spherical-shaped particles with the size ranging from 20 to 60 nm and contain numerous surface functional groups. The as-prepared activated carbons were then assessed as an electrode material of supercapacitor operating in the 0.5 M K2SO4 electrolyte in potential windows of −1.0∼0.0 V. The highest capacitance obtained was 205 F·g−1 at the scan rate of 2 mV·s−1 and 225 F·g−1 at a current density of 0.2 A·g−1. At the scan rate as high as 50 mV·s−1, all the as-prepared activated carbons in this study have the specific capacitance greater than 100 F·g−1

The Impact of Ce-Zr Addition on Nickel Dispersion and Catalytic Behavior for CO2 Methanation of Ni/AC Catalyst at Low Temperature

The CO2 methanation was studied over 7 wt.% nickel supported on Ce0.2Zr0.8O2/AC to evaluate the correlation of the structural properties with catalytic performance. The catalysts were investigated in more detail by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). A sample of 7 wt.% nickel loading supported on activated carbon (AC) was also prepared for comparison. The results demonstrated that the ceria-zirconia solid solution phase could disperse and stabilize the nickel species more effectively and resulted in stronger interaction with nickel than the parent activated carbon phase. Therefore, 7% Ni/Ce0.2Zr0.8O2/AC catalyst exhibited higher activity for CO2 reduction than 7% Ni//AC. It can attain 85% CO2 conversion at 350°C and have a CH4 selectivity of 100% at a pressure as low as 1 atm. The high activity of prepared catalysts is attributed to the good interaction between Ni and Ce0.2Zr0.8O2 and the high CO2 adsorption capacity of the activated carbon as well

Carbon Dioxide Methanation Over Nickel Catalysts Supported on Activated Carbon at Low Temperature

The methanation of carbon over nickel catalysts supported on activated carbon was investigated using a continuous flow microreactor. Catalysts with nickel loadings of 5, 7, and 10% were synthesised by incipient wetness impregnation methods and characterised using Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H₂-temperature-programmed reduction (TPR), BET, XRD, SEM, TEM and H₂-TPR. The methanation reaction was studied over the temperature range 200–500°C with a H₂ to CO₂ ratio of 4 : 1 in He and at 1 atm. With an increase in Ni content from 5 to 7 % both conversion of CO₂ and CH₄ selectivity increased. Increasing the nickel content to 10 %, however decreased conversion and selectivity due to the larger crystallite size and lower surface area of the catalyst. The most active catalyst with 7 % Ni does not deactivate during 15 h time on stream at 350°C. The high catalytic activity and stability of the studied catalysts is a consequence of the reducibility of Ni and a synergetic effect between the nickel active sites and the activated carbon surface

Effect of Electrical Injection of Corrosion Inhibitor on the Corrosion of Steel Rebar in Chloride-Contaminated Repair Mortar

The electrical rehabilitation treatments of repair mortar were performed with tetrabutylammonium bromide salt (TBAB) at an electrical current density of 5 A/m2, using two electrolytes (0.1 M NaOH and 0.1 M Na3BO3solutions), and for two time periods (1 and 4 weeks), respectively. The average organic cation-based inhibitor’s concentration in cement mortars before and after this treatment was quantified using the UV-Vis spectroscopy. The experimental results reveal that the EICI treatment with 0.1 M Na3BO3was more effective in injecting the inhibitor and in improving the chloride penetration resistance and compressive strength of the mortar, relative to using 0.1 M NaOH as electrolyte. In this case, after the 4-week EICI treatment, [TBA+] contents were 2.3 % and 2.4% by mass of cement mortar for uncontaminated and salt-contaminated mortars, respectively. After the 4-week EICI treatment, the apparent diffusion coefficients of chloride anion in cement mortar were decreased by 40% from 1.52 × 10−10 m2/s. The EICI treatment was able to halt the chloride-induced corrosion of the steel rebar by promoting its passivation. The 2-week EICI treatment using sodium hydroxide and sodium borate solutions decreased the corrosion current density of the rebar by 77.8% and 78.5%, respectively, approximately two months after the treatment

Effect of Electrical Injection of Corrosion Inhibitor on the Corrosion of Steel Rebar in Chloride-Contaminated Repair Mortar

The electrical rehabilitation treatments of repair mortar were performed with tetrabutylammonium bromide salt (TBAB) at an electrical current density of 5 A/m2, using two electrolytes (0.1 M NaOH and 0.1 M Na3BO3 solutions), and for two time periods (1 and 4 weeks), respectively. The average organic cation-based inhibitor’s concentration in cement mortars before and after this treatment was quantified using the UV-Vis spectroscopy. The experimental results reveal that the EICI treatment with 0.1 M Na3BO3 was more effective in injecting the inhibitor and in improving the chloride penetration resistance and compressive strength of the mortar, relative to using 0.1 M NaOH as electrolyte. In this case, after the 4-week EICI treatment, [TBA+] contents were 2.3 % and 2.4% by mass of cement mortar for uncontaminated and salt-contaminated mortars, respectively. After the 4-week EICI treatment, the apparent diffusion coefficients of chloride anion in cement mortar were decreased by 40% from 1.52 × 10−10 m2/s. The EICI treatment was able to halt the chloride-induced corrosion of the steel rebar by promoting its passivation. The 2-week EICI treatment using sodium hydroxide and sodium borate solutions decreased the corrosion current density of the rebar by 77.8% and 78.5%, respectively, approximately two months after the treatment

High CO Adsorption Performance of CuCl-Modified Diatomites by Using the Novel Method “Atomic Implantation”

An atomic implantation method was used to modify diatomite with CuCl. The CuCl/diatomite samples were characterized by different techniques, including FTIR, XRD, BET, SEM-TEM, EDX, and CO-TPR. Characterization results revealed the formation of CuCl particles of 50–60 nm highly dispersed on diatomite surface. CO adsorption measurements showed that 2CuCl/diatomite exhibits the highest CO adsorption capacity among all CuCl-modified samples with diatomite. Its CO adsorption capacity of 2.96 mmol/g at 30°C is 10 times higher than that of unmodified diatomite (0.29 mmol/g). The CO adsorption on CuCl-modified diatomites was found to fit well with the Langmuir–Freundlich model

High prevalence of hospital-acquired infections caused by gram-negative carbapenem resistant strains in Vietnamese pediatric ICUs A multi-centre point prevalence survey

There is scarce information regarding hospital-acquired infections (HAIs) among children in resource-constrained settings. This study aims to measure prevalence of HAIs in Vietnamese pediatric hospitals. Monthly point prevalence surveys (PPSs) in 6 pediatric intensive care units (ICUs) in 3 referral hospitals during 1 year. A total of 1363 cases (1143 children) were surveyed, 59.9% male, average age 11 months. Admission sources were: other hospital 49.3%, current hospital 36.5%, and community 15.3%. Reasons for admission were: infectious disease (66%), noninfectious (20.8%), and surgery/trauma (11.3%). Intubation rate was 47.8%, central venous catheter 29.4%, peripheral venous catheter 86.2%, urinary catheter 14.6%, and hemodialysis/filtration 1.7%. HAI was diagnosed in 33.1% of the cases: pneumonia (52.2%), septicemia (26.4%), surgical site infection (2%), and necrotizing enterocolitis (2%). Significant risk factors for HAI included age under 7 months, intubation and infection at admission. Microbiological findings were reported in 212 cases (43%) with 276 isolates: 50 Klebsiella pneumoniae, 46 Pseudomonas aeruginosa, and 39 Acinetobacter baumannii, with carbapenem resistance detected in 55%, 71%, and 65%, respectively. Staphylococcus aureus was cultured in 18 cases, with 81% methicillin-resistant Staphylococcus aureus. Most children (87.6%) received antibiotics, with an average of 1.6 antibiotics per case. Colistin was administered to 96 patients, 93% with HAI and 49% with culture confirmed carbapenem resistance. The high prevalence of HAI with carbapenem resistant gram-negative strains and common treatment with broad-spectrum antibiotics and colistin suggests that interventions are needed to prevent HAI and to optimize antibiotic use.Funding Agencies|Swedish International Development Agency (Sida); Wellcome Trust (UK); Global Antibiotic Resistance Partnership (GARP)</p