Experimental and modeling study on production of activated carbon from pistachio shells in rotary reactor

In this study, activated carbons were prepared by physical activation from pistachio shell with steam in a rotary reactor. Experiments were performed based on the central composite design (CCD) in DX8 software. A quadratic model for prediction of iodine number and a quadratic model for burn-off were developed using CCD in the activation process. The optimum iodine number and burn-off for physical activation were, respectively, 1,478.17 mg/g and 22.09 wt%, which showed good agreement with the experimental values. The optimum values were achieved at the activation temperature of 816.5 °C, dwell time of 40 min, and gas flow rate of 47.4 l/min.     

Preparation of activated carbon from sawdust by zinc chloride activation

A series of activated carbons were prepared from sawdust by zinc chloride activation in different operation conditions. The effects of operation parameters such as impregnation ratio, activation temperature and time on the adsorption properties of activated carbons were measured and analyzed in order to optimize these operation conditions. The experimental results show that under the experimental circumstances studied, both the yield and the adsorption for iodine and methylene blue of activated carbon can reach a relatively higher value in the chemical activation process with the impregnation ratio of 100% ZnCl₂/sawdust in the activation temperature of 500 °C carbonized for 60–90 minutes which are the optimum activation conditions in making wood activated carbon. The most important operation parameter in chemical activation with zinc chloride was found to be the impregnation ratio.     

Preparation of activated carbon from organic fraction of municipal solid wastes by ZnCl2 activation method and use it for elimination of chromium(VI) from aqueous solutions

In this study, the use of the organic fraction of municipal solid waste as an abundant and low-cost raw material for producing activated carbon was investigated. For this purpose, ZnCl₂ was used as a chemical activation agent and the carbonization process took place at 800 °C in N₂ atmosphere. Seven sorbents were prepared by chemical activation (pyrolysis under N₂ atmosphere at temperature of 800 °C after impregnation with ZnCl₂) with different ratios of ZnCl₂. The optimum ratio of organic fraction of municipal solid waste to ZnCl₂ was inspected via methylene blue number and iodine number (ASTM Designation: D4607–94). The results showed that the adsorbent with 60 % ZnCl₂/raw material was the most appropriate one with a satisfactory adsorption capacity, 112.4 mg g^?1 for methylene blue and 134.0 mg g^?1 for iodine. In addition, the structural analysis of this sorbent was performed using FT-IR, BET surface area, SEM–EDX and thermal analysis. Application of this sorbent to remove Cr(VI) from wastewater was studied to find an adsorption capacity of 66.7 mg g^?1. The experimental adsorption equilibrium data were fitted to Langmuir adsorption model with an acceptable adsorption capacity of 66.7 mg g^?1.     

Optimization of preparation conditions for activated carbon from palm oil fronds using response surface methodology on removal of pesticides from aqueous solution

Palm oil fronds were used to prepare activated carbon using the physiochemical activation method, which consisted of potassium hydroxide (KOH) treatment and carbon dioxide (CO₂) gasification. The effects of variable parameters activation temperature, activation time and chemical impregnation ratios (KOH: char by weight) on the preparation of the activated carbon and for the removal of pesticides: bentazon, carbofuran and 2,4-Dichlorophenoxyacetic acid (2,4-D) were investigated. Based on the central composite design (CCD), two factor interaction (2FI) and quadratic models were respectively employed to correlate the effect of variable parameters on the preparation of activated carbon used for the removal of pesticides with carbon yield. From the analysis of variance (ANOVA), the most influential factor on each experimental design response was identified. The optimum conditions for preparing the activated carbon from oil palm fronds were found as follows: activation temperature of 750 °C, activation time of 2 h and chemical impregnation ratio of 2.38. The percentage error between predicted and experimental results for the removal of bentazon, carbofuran and 2,4-D were 8.2, 1.3 and 9.2%, respectively and for the yield of the palm oil frond activated carbon was 5.6.     

Preparation of activated carbon from waste Camellia oleifera shell for supercapacitor application

The cost-effective activated carbons derived from waste Camellia oleifera shell (COS) by ZnCl₂ activation method are investigated as the active electrode material in electric double-layer capacitors (EDLCs) for the first time. The activation temperature and ZnCl₂/COS impregnation ratio are two key factors affecting the surface area and pore structure of the prepared activated carbons, which accordingly affect their capacitive performances. Electrochemical investigations indicate that the activated carbon (AC-3-600) obtained at the activation temperature of 600 °C and impregnation ratio of 3 shows the maximum specific capacitance of 374 and 266 F?g^?1 in 1 mol L^?1 H₂SO₄ and 6 mol L^?1 KOH electrolytes at 0.2 A g^?1, respectively. The high capacitance of the AC-3-600 is attributed to its high surface area (1,935 m² g^?1), high total pore volume (1.02 cm³ g^?1), and especially the large percentage of micropores (735 m² g^?1). Meanwhile, the activated carbon presents good cycle stability in both acid and alkaline electrolytes during 5,000 cycles at a fair current density of 4 A g^?1. So, we had reasons to believe that the activated carbons from waste COS by ZnCl₂ activation might be one of the innovative carbon electrode materials for EDLCs application.     

Fast and non–derivative method based on high–performance liquid chromatography–charged aerosol detection for the determination of fatty acids from Agastache rugosa (Fisch. et Mey.) O. Ktze. seeds

This study utilised response surface methodology to optimise the conditions for the extraction of A. rugosa seeds oil (ARO). Single–factor experiment and response surface methodology (RSM) were performed to identify the extraction time, liquid–solid ratio and extraction temperature that provided the highest yield of ARO. The optimal extraction time, liquid–solid ratio and extraction temperature were 8 h, 4:1 mL/g and 55 °C. The fatty acids (FAs) content and oil yield obtained through the optimised impregnation–extraction process were 19.67 mg/g and 32.1%. These values matched well with the predicted values. Linolenic acid was identified to be the main active ingredient of ARO. The high–performance liquid chromatography–charged aerosol detection method presented here is fast and does not require derivatisation. Therefore, it could be used to quantitatively analyse the FAs present in ARO and applied to detect compounds with low or no ultraviolet response.     

Mesoporous activated carbon from <Emphasis Type="Italic">Pentace</Emphasis> species sawdust via microwave-induced KOH activation: optimization and methylene blue adsorption

This work studied the optimization of preparation conditions of Pentace species sawdust activated carbon (PSAC) via microwave-induced KOH activation for the adsorption of methylene blue (MB) dye from aqueous solutions. The produced activated carbon was characterised through Brunauer–Emmett–Teller (BET) surface area and pore structural analysis, proximate and ultimate, scanning electron microscopy, and Fourier transform infrared spectroscopy. Response surface methodology technique was used to optimize the radiation power, radiation time and impregnation ratio for MB removal and PSAC yield through central composite design. The optimum preparation conditions for PSAC were obtained at a radiation power of 418 W, radiation time of 6.4 min, and an impregnation ratio of 0.5, which resulted in 27% PSAC yield and 93.74% MB removal. A mesoporous structure of PSAC was formed, with a BET surface area, total pore volume and average pore diameter of 914.15 m²/g, 0.52 cm³/g, and 3.19 nm, respectively. The experimental kinetic data were well described by a pseudo-second-order model and intraparticle diffusion. Adsorption data fitted the Redlich–Peterson equation better than the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich and Sips equations. However, the exponential value of Redlich–Peterson approached unity, hence, resulting in the original Langmuir equation, with adsorption capacity of 357.14 mg/g. The adsorption performance was effectively preserved even after four consecutive cycles, demonstrating good regeneration ability.     

Adsorption of methyl orange using activated carbon prepared from lignin by ZnCl2 treatment

Lignocellulosic materials are good and cheap precursors for the production of activated carbon. In this study, activated carbons were prepared from the lignin at different temperatures (200 to 500°C) by ZnCl₂. The effects influencing the surface area of the resulting activated carbon are activation temperature, activation time and impregnation ratio. The optimum condition, are found an impregnation ratio of 2, an activation temperature of 450°C, and an activation time of 2 h. The results showed that the surface area and micropores volume of activated carbon at the experimental conditions are achieved to 587 and 0.23 cm³ g^?1, respectively. The adsorption behavior of methyl orange dye from aqueous solution onto activated lignin was investigated as a function of equilibrium time, pH and concentration. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. A maximum adsorption capacity of 300 mg g^?1 of methyl orange by activated carbon was achieved.     

The use of microwave radiation for obtaining carbonaceous adsorbents from biomass and their use in elimination of inorganic pollutants

A new technology of obtaining activated carbons by physical and direct activation of biomass with the use of microwave radiation is described. The effect of activation temperature (700 and 800 °C) and two periods of time (15 and 30 min) on the textural parameters, acid–base character of the surface and sorption properties of activated carbons was tested. The resulting carbons were characterized by low-temperature nitrogen sorption and determination of pH as well as the number of surface oxygen groups. The sorption properties of the activated carbons obtained were characterized by determination of nitrogen dioxide and hydrogen sulphide adsorption in dry and wet conditions as well as by iodine removal from aqueous solution. The final products were adsorbents of surface area ranging from 291 to 368 m²/g and pore volume from 0.20 to 0.26 cm³/g, showing basic character of the surface. The results obtained in our study have proved that suitable choice of the pyrolysis and activation procedure for hay with the use of microwave radiation permit producing adsorbents with good capacity toward toxic gases of acidic character as well as inorganic pollutants of molecules of size similar to that of iodine molecules.     

Synthesis,characterization, optical,thermal and electrical properties of polybenzimidazoles

The variation of dielectric constant and dielectric loss of two novel polybenzimidazole (PBI) were studied at constant temperature with variable frequency. The polymers have shown maximum dielectric constant at low applied frequency 50 Hz at 393 K due to the space charge polarization. The AC conductivity and activation energy of polymers were arrived from dielectric constant and dielectric loss values. PBIs were synthesized by the oxidative polycondensation of benzimidazole monomers, 2-(1H-benzo [d] imidazole-2-yl)-4-bromophenol (BIBP), and 2-(1H-benzo [d] imidazole-2-yl)-6-methoxyphenol (BIMP) in an aqueous alkaline medium using NaOCl as oxidant. The monomers and polymers were characterized by various spectroscopic techniques. Fluorescence spectra of monomers and polymers showed their λ _max emission in the region of 472–479 and 463–472 nm respectively. The electrical conductivities of iodine doped polybenzimidazoles were measured by four-point probe technique and it increases with increase in iodine vapour contact time. The electrical conductivity values were correlated with the charge density on imidazole nitrogen obtained from Huckel calculation method. Both the PBI are having reasonably good thermal stability and are shown by high carbines residues of around 40% at 500°C in thermogravimetric analysis.     

The Selection of the Optimal Impregnation Conditions of Vegetable Matrices with Iodine

This study aimed to determine the use of selected vegetables (pumpkin, cauliflower, broccoli, carrot) as carriers of potassium iodide (KI) and potassium iodate (KIO₃) by determining changes in iodine content under various conditions of impregnation as the degree of hydration, impregnated sample temperature, and impregnation time. The influence of these conditions on iodine contents in vegetables after their fortification and storage (21 °C/230 days) was analyzed. The results showed that all selected vegetables could be efficient iodine carriers. However, the conditions of the impregnation process are crucial for fortification efficiency, particularly the degree of hydration and the temperature of the impregnated samples before drying. The results showed that the lowest iodine content was in samples fortified at 4 °C and 1:4 hydration. On the other hand, the highest reproducibility of iodine was for the following fortification conditions: temperature of −76 °C and hydration of 1:1. The studies confirmed the higher stability of iodine in KIO₃ form compared to KI. To increase recovery of the introduced iodine in the product after drying, using the conditioning step at 4 °C is not recommended. We recommend freezing vegetables immediately after the impregnation process     

Preparation and characterization of waste ion-exchange resin-based activated carbon for CO<Subscript>2</Subscript> capture

Waste ion-exchange resin was utilized as precursor to produce activated carbon by KOH chemical activation, on which the effects of different activation temperatures, activation times and impregnation ratios were studied in this paper. The CO₂ adsorption of the produced activated carbon was tested by TGA at 30 °C and environment pressure. Furthermore, the effects of preparation parameters on CO₂ adsorption were investigated. Experimental results show that the produced activated carbons are microporous carbons, which are suitable for CO₂ adsorption. The CO₂ adsorption capacity increases firstly and then decreases with the increase of activation temperature, activation time and impregnation rate. The maximum adsorption capacity is 81.24 mg/g under the condition of 30 °C and pure CO₂. The results also suggest that waste ion-exchange resin-based activated carbons possess great potential as adsorbents for post-combustion CO₂ capture.     

Green synthesis of benzimidazole derivatives catalyzed by ionic liquid under microwave irradiation

An efficient synthesis of benzimidazole derivatives from o-phenylene diamine and substituted aromatic aldehyde catalyzed by ionic liquid under microwave irradiation was reported. The synthesis conditions were first optimized by single factor experiments. Then, a central composite design combined with response surface methodology was used to study the most effective factors. Optimal conditions were synthesis time 1 h, the reactant/catalyst molar ratio 1:1:0.200, the temperature 50 °C and the microwave power 500 W. Under optimized conditions, the yields of benzimidazole derivatives were 78.55–97.66 %. This method offered the outstanding advantages, such as faster reaction rate, higher yields, recyclable catalyst, environmental friendliness, and simple workup procedure.     

Activated carbon fibers with a high heteroatom content by chemical activation of PBO with phosphoric acid

The preparation of activated carbon fibers (ACFs) by phosphoric acid activation of poly(p-phenylene benzobisoxazole) (PBO) fibers was studied, with particular attention to the effects of impregnation ratio and carbonization temperature on porous texture. Phosphoric acid has a strong effect on PBO degradation, lowering the temperature range at which the decomposition takes place and changing the number of mass loss steps. Chemical analysis results indicated that activation with phosphoric acid increases the concentration of oxygenated surface groups; the resulting materials also exhibiting high nitrogen content. ACFs are obtained with extremely high yields; they have well-developed porosity restricted to the micropore and narrow mesopore range and with a significant concentration of phosphorus incorporated homogeneously in the form of functional groups. An increase in the impregnation ratio leads to increases in both pore volume and pore size, maximum values of surface area (1250 m(2)/g) and total pore volume (0.67 cm(3)/g) being attained at the highest impregnation ratio (210 wt % H(3)PO(4)) and lowest activation temperature (650 °C) used; the corresponding yield was as large as 83 wt %. The obtained surface areas and pore volumes were higher than those achieved in previous works by physical activation with CO(2) of PBO chars.     

Kinetic study of oxalic acid pretreatment of moso bamboo for textile fiber

In this study, samples of moso bamboo were hydrolyzed for textile fiber with oxalic acid under various process conditions. Saeman hydrolysis models were applied to predict the percentage of xylan remained in the substrate after pretreatment and the net xylose yield in the liquid stream. Kinetic constants for Saeman hydrolysis models were analyzed by an Arrhenius-type expansion which include activation energy and catalyst concentration factors. The result showed that the degradation activation energies of xylan and xylose were 97.27 and 136.38 kJ/mol, respectively. Then the kinetic of mathematical models were obtained. Furthermore, the reaction parameters of oxalic acid concentration (1–4 % w/w), reaction temperature (150–180 °C), and reaction time (5–60 min) were handled as a single parameter, combined severity, which ranged in the present study from 0.86 to 1.62. Using combined severity parameters, an optimal condition was achieved which was as the followings: oxalic acid 2.0 % w/w, 170 °C, and 20 min. Under these conditions, 2.3 g glucose/L and 13.65 g xylose/L were produced in the hydrolysate fraction, 54.1 % glucan and 10.8 % xylan were produced in the residue fraction.     

Studies of total, organic and inorganic iodine in Canadian bovine milk samples with varying milk fat content using ion-exchange chromatography and neutron activation analysis

Chemical separation methods in conjunction with instrumental neutron activation analysis (INAA) were developed for measuring iodine levels in commercially available bovine milk with varying milk fat (MF) content. Samples of homogenized (3.25 % MF), partly skimmed (2 % MF), partly skimmed (1 % MF), partly skimmed calcium enriched (1 % MF + Ca), and skim (<0.05 %) milk were purchased from local supermarkets. Ion exchange chromatography, solvent extraction, and ammonium sulfate precipitation methods were applied to the separation of the inorganic, lipidic and proteic fractions of iodine in milk. The levels of iodine were measured by INAA in total reactor and epi-cadmium (EINAA) neutron flux in conjunction with conventional gamma-ray and Compton suppression spectrometry (CSS). A pseudo-cyclic INAA method coupled with CSS (PC-INAA-CSS) was also explored as an instrumental option to further lower the detection limit of iodine. The detection limits of 0.06, 0.06 and 0.02 μg mL^?1 for iodine were obtained using INAA-CSS, EINAA-CSS, and PC-INAA-CSS methods, respectively. Although the PC-INAA-CSS method provided the lowest detection limit, the INAA-CSS method was sufficient for the determination of total iodine in almost all samples analyzed in this work. The total iodine concentrations (μg mL^?1) were: 0.40 ± 0.01 (in 3.25 % MF), 0.40 ± 0.01 (2 % MF), 0.42 ± 0.01 (1 % MF), 0.42 ± 0.01 (<0.05 %), and 0.96 ± 0.01 (1 % MF + Ca) milk samples. Iodine bound to various fractions of the milk samples analyzed, in percent of total iodine content, ranged: (0.05–1.8), (1.9–4.8), (90–95) for the lipidic, proteic and anionic inorganic fractions respectively. Iodine recovery in all cases was higher than 96 %.     

KOH Direct Activation for Preparing Activated Carbon Fiber from Polyacrylonitrile-based Pre-oxidized Fiber

The activated carbon fiber（ACF） was prepared from polyacrylonitrile-based pre-oxidized fiber（PANOF） by KOH direct activation. The influence of activation conditions including impregnation ratio（the mass ratio of PANOF to KOH）, activation temperature and activation time on the pore structure and electrochemical properties of ACF was investigated, and the corresponding activation mechanism was proposed. The ACF prepared at an activation temperature of 800℃ and an impregnation ratio（the mass ratio of PANOF to KOH） of 1：2 for an activation time of 1 b in 6 mol/L KOH solution exhibits a specific surface area of 3029 m^2/g, a mesoporosity of 84.2% and a specific capacitance of 288 F/g, and shows a good capacitive performance. The prepared ACF can be used as the electrode material for supercapacitors.     

Fabrication and Characterization of Diatomite-supported Activated Carbon Functional Ceramic

Using porous diatomite ceramic as carrier and phenolic resin as carbon precursor, the activated carbon functional ceramic with the activated carbon fixed into porous ceramic was prepared by the impregnation load phenolic resin, carbonization and activation isolated air. The influences of impregnation, curing, carbonization, activation etc. on the material property were discussed. The iodine value, SEM, elemental analyzer, BET and spectrum analysis chart were used to characterize the microstructures and performance of material at different conditions. The results showed that the excellent comprehensive property of activated carbon functional ceramic was gained when it adsorbed phenolic resin in 4 h under vacuum condition at curing temperature of 150 ℃ for 0.5 h and carbonization temperature of 600 ℃ for 1.0 h, and then put into 25wt% KOH for 4.0 h at activation temperature of 700 ℃ for 1.5 h. The iodine value is 176.9 mg/g, the specific surface area can reach 86.3 m2/g and the yield of carbonization is 50.48%.     

Kinetics of thiophene hydrodesulfurization over a supported Mo–Co–Ni catalyst

In this study, the kinetics of thiophene (TH) hydrodesulfurization (HDS) over the Mo–Co–Ni-supported catalyst was investigated. Trimetallic catalyst was synthesized by pore volume impregnation and the metal loadings were 11.5 wt % Mo, 2 wt % Co, and 2 wt % Ni. A large surface area of 243 m²/g and a relatively large pore volume of 0.34 cm³/g for the fresh Mo–Co–Ni-supported catalyst indicate a good accessibility to the catalytic centers for the HDS reaction. The acid strength distribution of the fresh and spent catalysts, as well as for the support, was determined by thermal desorption of diethylamine (DEA) with increase in temperature from 20 to 600 °C. The weak acid centers are obtained within a temperature range between 160 and 300 °C, followed by medium acid sites up to 440 °C. The strong acid centers are revealed above 440 °C. We found a higher content of weak acid centers for fresh and spent catalysts as well as alumina as compared to medium and strong acid sites. The catalyst stability in terms of conversion as a function of time on stream in a fixed bed flow reactor was examined and almost no loss in the catalyst activity was observed. Consequently, this fact demonstrated superior activity of the Mo–Co–Ni-based catalyst for TH HDS. The activity tests by varying the temperature from 200 to 275 °C and pressure from 30 to 60 bar with various space velocities of 1–4 h^?1 were investigated. A Langmuir–Hinshelwood model was used to analyze the kinetic data and to derive activation energy and adsorption parameters for TH HDS. The effect of temperature, pressure, and liquid hourly space velocity on the TH HDS activity was studied.     

Non-linear Compensated Dwell Time for Efficient Fused Silica Surface Figuring Using Inductively Coupled Plasma

Atmospheric plasma etching has been increasingly applied in the fabrication of optical elements for high efficiency and near-zero damage to optical surfaces. However, the non-linearity of material removal rate is inevitable because of the thermal effect of inductively coupled plasma (ICP) etching for fused silica. To apply ICP to figure fused silica surface, the time-varying non-linearity between material removal rate and dwell time is analyzed. An experimental model of removal function is established considering the time-varying non-linearity. According to this model, an algorithm based on nested pulsed iterative method is proposed for calculating and compensating this time-varying non-linearity by varying the dwell time. Simulation results show that this algorithm can calculate and adjust the dwell time accurately and remove surface errors with rapid convergence. Surface figuring experiments were set up on the fused silica planar work-pieces with a size of 100 mm (width) × 100 mm (length) × 10 mm (thickness). With the compensated dwell time, the surface error converges rapidly from 4.556 λ PV (peak-to-valley) to 0.839 λ PV within 13.2 min in one iterative figuring. The power spectral density analysis indicates that the spatial frequency errors between 0.01 and 0.04 mm^?1 are smoothed efficiently, and the spatial frequency errors between 0.04 and 0.972 mm^?1 are also corrected. Experimental results demonstrate that the ICP surface figuring can achieve high convergence for surface error reduction using the compensated dwell time. Therefore, the ICP surface figuring can greatly improve surface quality and machining efficiency for fused silica optical elements.