Chemical Impregnation Research Articles

Synthesis and Efficient Visible Light Photocatalytic Hydrogen Evolution of Polymeric g-C3N4 Coupled with CdS Quantum Dots

Novel CdS quantum dot (QD)-coupled graphitic carbon nitride (g-C3N4) photocatalysts were synthesized via a chemical impregnation method and characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy. The effect of CdS content on the rate of visible light photocatalytic hydrogen evolution was investigated for different CdS loadings using platinum as a cocatalyst in methanol aqueous solutions. The synergistic effect of g-C3N4 and CdS QDs leads to efficient separation of the photogenerated charge carriers and, consequently, enhances the visible light photocatalytic H2 production activity of the materials. The optimal CdS QD content is determined to be 30 wt %, and the corresponding H2 evolution rate was 17.27 μmol·h–1 under visible light irradiation, ∼9 times that of pure g-C3N4. A possible photocatalytic mechanism of the CdS/g-C3N4 comp...

Preparation of Mesoporous‐Activated Carbon from Branches of Pomegranate Trees: Optimization on Removal of Methylene Blue Using Response Surface Methodology

Mesoporous activated carbon prepared from branches of pomegranate trees (BP) using physiochemical activation (potassium hydroxide treatment and carbon dioxide gasification). Based on the central composite design (CCD), two factor interaction (2FI) and quadratic models were respectively employed to correlate the activated carbon preparation variables. The effects of the activation temperature, activation time, and chemical impregnation ratios on the carbon yield, methylene blue (MB) removal were investigated. From the analysis of variance (ANOVA), the most influential factor on each experimental design response was identified. The optimum conditions for preparing activated carbon from branches of pomegranate trees (BP) were found to be activation temperature of 620.5°C, activation time of 1.4 h, and chemical impregnation ratio of 1.5. The carbon yield was found to be 16% while the removal of methylene blue was found to be 92.5%.

Synthesis of Activated Carbon from Rice Husk Using Microwave Heating Induced KOH Activation

The production of functional activated carbon materials starting from inexpensive natural precursors using environmentally friendly and economically effective processes has attracted much attention in the areas of material science and technology. In particular, the use of plant biomass to produce functional carbonaceous materials has attracted a great deal of attention in various aspects. In this study the preparation of activated carbon has been attempted from rice husks via a chemical activation-assisted microwave system. The rice husks were milled via attrition milling with aluminum balls, and then carbonized under purified <TEX>$N_2$</TEX>. The operational parameters including the activation agents, chemical impregnation weight ratio of the calcined rice husk to KOH (1:1, 1:2 and 1:4), microwave power heating within irradiation time (3-5 min), and the second activation process on the adsorption capability were investigated. Experimental results were investigated using XRD, FT-IR, and SEM. It was found that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area. The activated carbons prepared by microwave heating with an activation process have higher surface area and larger average pore size than those prepared by activation without microwave heating when the ratio with KOH solution was the same. The activation time using microwave heating and the chemical impregnation ratio with KOH solution were varied to determine the optimal method for obtaining high surface area activated carbon (1505 <TEX>$m^2$</TEX>/g).

Activated carbon xerogels for the removal of the anionic azo dyes Orange II and Chromotrope 2R by adsorption and catalytic wet peroxide oxidation

Activated carbon xerogels (ACXs) were tested for the removal of azo dyes in aqueous solutions, either by adsorption or by catalytic wet peroxide oxidation (CWPO). Two azo dyes, Orange II (OII) and Chromotrope 2R (C2R), were chosen as model pollutants. The ACXs were produced by activation of an organic resorcinol–formaldehyde xerogel (RFX). Three different activation procedures were carried out producing five distinct ACXs: steam at 1073K (ACX-S), chemical impregnation with H3PO4 at 773K (ACX-P) and alkali activation with dry KOH at 973K (ACX-K), using three different mass ratios of KOH/RFX, namely 1:1 (ACX-K1), 2:1 (ACX-K2) and 4:1 (ACX-K4).The results obtained in the adsorption experiments carried out at pH=3, T=303K, adsorbent load of 0.1gL−1 and azo dye concentration of 100mgL−1 show that the interaction between the carbon materials and the anionic dyes is enhanced with the basicity of the carbon surfaces. ACX-K materials, the carbon materials with higher basicity amongst those prepared, exhibit high adsorption performances for the removal of both dyes, namely from over 215mgg−1 (for adsorption of C2R on ACX-K2 after 150min) up to 499mgg−1 (for adsorption of OII on ACX-K4 at the same period of time). Furthermore, with ACX-K materials in CWPO (i.e., using H2O2) increments in the removal of C2R as high as 33%, 24% and 20%, in comparison to the removals obtained by adsorption, where obtained when ACX-K1, ACX-K2 and ACX-K4 were respectively tested at 303K. Increasing the operating temperature (T=323K), the removal increments achieved by CWPO, compared to the removals obtained by adsorption at the same temperature, increase 67%, 59% and 49%, when ACX-K1, ACX-K2 and ACX-K4 were respectively tested. Recycling studies with ACX-K1 puts in evidence the high stability of this catalyst in CWPO, since it was observed, after a first reaction run, that the catalytic activity of this material is not affected by its successive reuse.Increasing the operating temperature (T=323K) and the adsorbent load (0.5gL−1), ACX-K4 is able to completely remove the C2R content by adsorption. In the case of ACX-K1 and ACX-K2, adsorption removals over 97% of the C2R content are attainable.

Interaction of Au with Thin ZrO2 Films: Influence of ZrO2 Morphology on the Adsorption and Thermal Stability of Au Nanoparticles

The model catalysts of ZrO(2)-supported Au nanoparticles have been prepared by deposition of Au atoms onto the surfaces of thin ZrO(2) films with different morphologies. The adsorption and thermal stability of Au nanoparticles on thin ZrO(2) films have been investigated using synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The thin ZrO(2) films were prepared by two different methods, giving rise to different morphologies. The first method utilized wet chemical impregnation to synthesize the thin ZrO(2) film through the procedure of first spin-coating a zirconium ethoxide (Zr(OC(2)H(5))(4)) precursor onto a SiO(2)/Si(100) substrate at room temperature followed by calcination at 773 K for 12 h. Scanning electron microscopy (SEM) investigations indicate that highly porous "sponge-like nanostructures" were obtained in this case. The second method was epitaxial growth of a ZrO(2)(111) film through vacuum evaporation of Zr metal onto Pt(111) in 1 × 10(-6) Torr of oxygen at 550 K followed by annealing at 1000 K. The structural analysis with low energy electron diffraction (LEED) of this film exhibits good long-range ordering. It has been found that Au forms smaller particles on the porous ZrO(2) film as compared to those on the ordered ZrO(2)(111) film at a given coverage. Thermal annealing experiments demonstrate that Au particles are more thermally stable on the porous ZrO(2) surface than on the ZrO(2)(111) surface, although on both surfaces, Au particles experience significant sintering at elevated temperatures. In addition, by annealing the surfaces to 1100 K, Au particles desorb completely from ZrO(2)(111) but not from porous ZrO(2). The enhanced thermal stability for Au on porous ZrO(2) can be attributed to the stronger interaction of the adsorbed Au with the defects and the hindered migration or coalescence resulting from the porous structures.

Adsorption characteristics of industrial solid waste derived activated carbon prepared by microwave heating for methylene blue

The main objective of this work is to prepare and characterize activated carbon form oil palm fiber (PFAC), an industrial solid waste abundantly available from the biodiesel manufacturing plants, via microwave assisted KOH activation. The influences of chemical impregnation ratio (0.25–2.00), microwave power (90–800W) and radiation time (2–8min) on the properties of activated carbon were investigated. The adsorptive behavior of PFAC was quantified using methylene blue (MB) as dye model compound, while the surface chemistry was characterized by determination of surface acidity/basicity, Fourier transform infrared spectroscopy and zeta potential measurement. Equilibrium data were examined using a comparison of linear and non-linear isotherm models. The optimum conditions resulted in PFAC with a monolayer adsorption capacity of 382.32mg/g for MB and carbon yield of 32.09%. The BET surface area, Langmuir surface area and total pore volume were determined to be 1223m2/g, 1827m2/g and 0.72cm3/g, respectively. The adsorption kinetic was well fitted to the pseudo-second-order model.

Superior hydrogen production rate by catalytic hydrolysis of ammonia borane using Co-B nanoparticles supported over mesoporous silica particles

Catalyst in the form of Co-B nanoparticles supported on mesoporous silica particles (MSP) was synthesized by chemical impregnation–reduction method. This catalyst powder was used for hydrogen production by hydrolysis of Ammonia Borane (AB) and was compared with Co-B catalyst supported on non-porous silica particles (NSP) and unsupported Co-B powder. It was found that the MSPs synthesized in the present studies have average pore size of about 3.1 nm which were efficient to anchor the Co-B particles with average size of ~ 8 nm on the surface to provide high active surface area and improved degree of dispersion. MSP-supported Co-B catalyst was able to produce expected amount of H2 gas from hydrolysis of AB with significantly superior generation rate, about 3 times higher than that produced by unsupported and NSP-supported Co-B catalyst. Availability of a large number of under-coordinated Co active atoms owing to the size of nanoparticles, better dispersion, high surface area and good stability against agglomeration during the reaction are the main features acquired by the Co-B nanoparticles supported on MSP that exhibit high catalytic efficiency.

The cobalt content effect on the electrochemical behavior of nickel hydroxide electrodes

In this paper, the study of nickel hydroxide porous electrodes containing different concentrations of cobalt as additive (2–10%), polytetrafluoroethylene (PTFE) as binder material and prepared by chemical impregnation on nickel sintered substrate, are presented. The characterization of the different electrodes is performed using optical techniques such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and electrochemical techniques as cyclic voltammetry, charge-discharge curves and electrochemical impedance spectroscopy (EIS). The results indicate that the concentration of 5% metallic Co improves the electrochemical behavior of the active material.

Kinetics of 2-Chloro-6-Nitrotoluene Hydrogenation on Palladium/Carbon Catalyst without Inhibitors

Pd-only catalyst supported on activated carbon has been prepared by chemical impregnation and used to catalyze the hydrogenation of 2-chloro-6-nitrotoluene (2-CNT) to 3-chloro-2-methylaniline in solvent-free condition. The effects of reaction temperature，H2 pressure on the hydrogenation have been investigated. The reaction showed very high selectivity with the dehalogenation side product with a yield of less than 1.2 %. The most favorable conditions could be temperature= 353 K, stirring speed= 1200 rpm, H2 pressure= 1 MPa. The catalytic hydrogenation reaction was found to have a zero order with hydrogen and 1 order with 2-CNT. The apparent activation energy of the hydrogenation was 60.58 kJ/mol.

Balance the oxidation resistance and mechanical properties of C/Si–C–N composite by a Si–O–C interphase

Carbon fiber reinforced Si–C–N matrix composite with a Si–O–C interphase (C/Si–O–C/Si–C–N) was fabricated via chemical vapor infiltration and polymer impregnation and pyrolysis process. The mechanical properties and oxidation behaviors of C/Si–O–C/Si–C–N were investigated using three-point-bending test and thermogravimetry. The results indicated that the oxidation resistance of C/Si–O–C/Si–C–N was improved as compared to C/Si–C–N with pyrolytic carbon (PyC) interphase (C/PyC/Si–C–N). The higher oxidation resistance of C/Si–O–C/Si–C–N attributed to the high inoxidizability of Si–O–C interlayer and low thermal stress in matrix. The flexural strength of C/Si–O–C/Si–C–N rivaled that of C/PyC/Si–C–N and the modulus was higher than that of C/PyC/Si–C–N. The suitable interphase and the optimized interface bonding can get the high oxidation resistance of the composites with the mechanical properties maintained.

Potential of jackfruit peel as precursor for activated carbon prepared by microwave induced NaOH activation

The feasibility of preparing activated carbon (JPAC) from jackfruit peel, an industrial residue abundantly available from food manufacturing plants via microwave-assisted NaOH activation was explored. The influences of chemical impregnation ratio, microwave power and radiation time on the properties of activated carbon were investigated. JPAC was examined by pore structural analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, surface acidity/basicity and zeta potential measurements. The adsorptive behavior of JPAC was quantified using methylene blue as model dye compound. The best conditions resulted in JPAC with a monolayer adsorption capacity of 400.06mg/g and carbon yield of 80.82%. The adsorption data was best fitted to the pseudo-second-order equation, while the adsorption mechanism was well described by the intraparticle diffusion model. The findings revealed the versatility of jackfruit peels as good precursor for preparation of high quality activated carbon.

Mesoporous activated carbon from wood sawdust by K2CO3 activation using microwave heating

Wood sawdust was converted into a high-quality activated carbon (WSAC) via microwave-induced K2CO3 activation. The operational variables including chemical impregnation ratio, microwave power and irradiation time on the carbon yield and adsorption capability were identified. The surface physical characteristics of WSAC were examined by pore structural analysis, scanning electron microscopy and nitrogen adsorption isotherms. The adsorptive behavior of WSAC was quantified using methylene blue as model dye compound. The best conditions resulted in activated carbon with a monolayer adsorption capacity of 423.17mg/g and carbon yield of 80.75%. The BET surface area, Langmuir surface area and total pore volume were corresponded to 1496.05m2/g, 2245.53m2/g and 0.864cm3/g, respectively. The findings support the potential to prepare high surface area and mesoporous activated carbon from wood sawdust by microwave assisted chemical activation.

Textural porosity, surface chemistry and adsorptive properties of durian shell derived activated carbon prepared by microwave assisted NaOH activation

This study reports the preparation of activated carbon from durian shell (DSAC) by microwave assisted NaOH activation. The operational parameters including chemical impregnation ratio (0.25–2.00), microwave power (90–800W) and irradiation time (4–8min) on the carbon yield and adsorption capability were investigated. The virgin characteristics of DSAC were examined by pore structural analysis, Scanning Electron Microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, and surface acidity/basicity. The adsorptive property of DSAC was quantified using methylene blue as model dye compound. Equilibrium data were simulated using the Freundlich, Langmuir, Temkin and Redlich–Peterson isotherm models. Kinetic modeling was fitted to the pseudo-first-order, pseudo-second-order and Elovich equations, while adsorption mechanism was determined using the intraparticle diffusion and Boyd models. The best conditions resulted in DSAC with a monolayer adsorption capacity for MB of 410.85mg/g, while the BET surface area and total pore volume were identified to be 1475.48m2/g and 0.841m3/g, respectively. The findings revealed the potential of durian shell as a viable biomass for preparation of activated carbon.

A solid oxide cell yielding high power density below 600 °C

Here we report solid oxide cells with thin strontium- and magnesium-doped lanthanum gallate electrolytes that yield power densities of 1.06 W cm−2 at 550 °C and 0.81 W cm−2 at 500 °C when operated on humidified hydrogen and ambient air. Cost-effective ceramic processing and chemical solution impregnation methods were utilized, yielding a dual micron- and nano-scale architecture that is essential for achieving good low-temperature performance.

Coconut husk derived activated carbon via microwave induced activation: Effects of activation agents, preparation parameters and adsorption performance

Preparation of activated carbon has been attempted from coconut husk (CHAC) via microwave assisted chemical activation. The operational parameters including the effects of activation agents, chemical impregnation ratio (0.25–2.00), microwave power (90–800W) and irradiation time (4–8min) on the carbon yield and adsorption capability were investigated. CHAC was examined by pore structural analysis, Scanning Electron Microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, and zeta potential measurement, while the adsorptive property was quantified using methylene blue (MB) as dye model compound. The best conditions (KOH as activating agent, IR of 1.25, microwave power of 600W and radiation time of 6min) resulted in CHAC with a monolayer adsorption capacity of 418.15mg/g for MB and carbon yield of 80.75%. The BET surface area, Langmuir surface area and total pore volume were identified to be 1356.25m2/g, 2040.01m2/g and 0.780m3/g, respectively. Equilibrium data were favorably described by the Langmuir isotherm, while the adsorption kinetic was satisfactory fitted to the pseudo-second-order model.

Factors affecting the carbon yield and adsorption capability of the mangosteen peel activated carbon prepared by microwave assisted K 2CO 3 activation

This study presents the preparation of activated carbon from mangosteen peel via microwave assisted K 2CO 3 activation. The operational parameters including chemical impregnation ratio, microwave power and irradiation time on the carbon yield and adsorption capability of the mangosteen peel derived activated carbon (MPAC) were investigated. The virgin characteristics of the prepared MPAC were examined by pore structural analysis, Scanning Electron Microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, surface acidity/basicity and zeta potential measurement. The adsorptive property of MPAC was tested using methylene blue as dye model compound. The best conditions resulted in MPAC with a maximum monolayer adsorption capacity of 379.63 mg/g and carbon yield of 80.95%, respectively. Equilibrium data were favorably described by Langmuir isotherm, while adsorption kinetics was best fitted to the pseudo-second-order model. The findings support the feasibility of mangosteen peel derived activated carbon as a promising and economic adsorbent.

Adsorption Studies for the Removal of Nitrate Using Modified Lignite Granular Activated Carbon

The removal of nitrate on ZnCl2 modified lignite granular activated carbon (LGAC) was investigated. The LGAC was modified with varying chemical impregnation ratios (ZnCl2: LGAC) and activation temperatures. Modified LGAC (LGAC5), with a 2:1 chemical impregnation ratio and a 500°C activation temperature had the optimum adsorption capacity for , at a 200 mg/L initial concentration. The initial pH of the testing solutions significantly influenced the adsorption capacity of LGAC5. The contact time studies showed the effectiveness of LGAC5, up to 50 mg/L initial concentration with 30 min of equilibration time. Isotherm studies revealed the highest values of the Langmuir constant (b), confirming strong affinity of LGAC5 for ions. Thermodynamics studies verified the endothermic nature of the adsorption process with randomness at the solid/solution interface. Competitive ion testing demonstrated that interfering anions, such as Cl−, , significantly reduced adsorption on LGAC5.

Production of microporous palm shell based activated carbon for methane adsorption: Modeling and optimization using response surface methodology

In this study, the optimization of the palm shell based activated carbon production using combination of chemical and physical activation for methane adsorption is investigated. response surface methodology (RSM) in combination with central composite design (CCD) was used to optimize the operating parameters of the production process. Physical activation temperature, chemical impregnation ratio and physical activation time were chosen as the main process variables and the amount of methane adsorption was selected as the investigated response. Phosphoric acid and carbon dioxide were used as chemical and physical agents, respectively. The optimum reaction conditions were found to be a physical activation temperature of 855°C, H3PO4 impregnation ratio of 9.42g of phosphorous per gram palm shell and physical activation time of 135min. The results exhibited significant increase in methane adsorption after physio-chemical activation.

Preparation, characterization and evaluation of adsorptive properties of orange peel based activated carbon via microwave induced K2CO3 activation

This work explores the feasibility of orange peel, a citrus processing biomass as an alternative precursor for preparation of activated carbon (OPAC) via microwave assisted K2CO3 activation. The operational parameters, chemical impregnation ratio, microwave power and irradiation time on the carbon yield and adsorption capability were investigated. The virgin characteristics of OPAC were examined by pore structural analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen adsorption isotherm, elemental analysis, surface acidity/basicity and zeta potential measurement. The optimum conditions resulted in OPAC with a monolayer adsorption capacity of 382.75mg/g for methylene blue and carbon yield of 80.99%. The BET surface area, Langmuir surface area and total pore volume were identified to be 1104.45m2/g, 1661.04m2/g and 0.615m3/g, respectively. Equilibrium data were simulated using the Langmuir, Freundlich, Dubinin–Radushkevich, Redlich–Peterson, and Toth isotherms, and kinetic data were fitted to the pseudo-first-order, pseudo-second-order and Elovich kinetic models.

Microwave-assisted preparation and adsorption performance of activated carbon from biodiesel industry solid reside: Influence of operational parameters

Preparation of activated carbon has been attempted using KOH as activating agent by microwave heating from biodiesel industry solid residue, oil palm empty fruit bunch (EFBAC). The significance of chemical impregnation ratio (IR), microwave power and activation time on the properties of activated carbon were investigated. The optimum condition has been identified at the IR of 1.0, microwave power of 600W and activation time of 7min. EFBAC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement, determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue as dye model compound. The optimum conditions resulted in activated carbon with a monolayer adsorption capacity of 395.30mg/g and carbon yield of 73.78%, while the BET surface area and total pore volume were corresponding to 1372m2/g and 0.76cm3/g, respectively.