Self-generated Atmosphere Research Articles

Removal of sulphur and nitrogen compounds from model fuel by adsorption of modified activated carbon

This study aimed to achieve the highest percentage removal of dibenzothiophene (DBT), quinoline (QUI), and indole (IND) adsorbed by double-impregnated modified activated carbon (MAC). Modification of commercial activated carbon (AC) by sulphuric acid (H2SO4) of 15%, 30%, 45%, 60%, and 75% w/v followed by subsequent 1 zinc chloride (ZnCl2): 1 AC impregnation ratio and activated at 500 oC in a muffle furnace under self-generated atmosphere for an hour. The determination of optimized MAC was identified through the highest removal rate of DBT, QUI, and IND from adsorption experiments which were analysed using an ultraviolet-visible (UV-Vis) spectrophotometer. It was found that DBT and IND showed a removal high percentage of up to 86.23% and 82.77% respectively by using 75% H2SO4 with ZnCl2 MAC. Meanwhile, QUI favoured 30% H2SO4 with ZnCl2 MAC with a removal percentage of 33.17% which was still higher than unmodified AC. Physical and chemical properties such as the morphological structure, elemental analysis, porosity, pore size, surface functional group, percentage yield, pH, bulk density, content, ash content, and iodine number were studied for the optimized MAC. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the MAC. Both MACs showed high percentage yields of 72.08% and 71.13% for 30% and 75% H2SO4 and ZnCl2 MAC respectively. Meanwhile, the pH was between the ranges of 5.36-5.53 for both MACs. Bulk densities were also favourable while the moisture and ash content were within acceptable limits. Iodine numbers for 30% and 75% H2SO4 and ZnCl2 MAC were 857 and 861 mg/g respectively, hence indicating that the MAC achieved high porosity and good adsorption performance. Langmuir, Freundlich, and Temkin adsorption isotherm models as well as pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models were considered for understanding the adsorption mechanisms. The study revealed that DBT, QUI, and IND removal processes, followed the Langmuir adsorption isotherm model with correlation coefficients, R2 of 0.9905, 0.9791, and 0.9964 respectively. Moreover, the adsorption kinetic data of DBT, QUI, and IND provided a better fitting to the PSO kinetic model with R2 of 0.9992, 0.9987, and 0.9998 respectively. According to the Langmuir isotherm model and PSO kinetic model, the adsorption mechanisms of DBT QUI and IND were chemisorbed under monolayer formations.

Activated carbon fibers derived from dryer lint via self-generated atmosphere for supercapacitor applications

Activated carbon fibers derived from dryer lint via self-generated atmosphere for supercapacitor applications

In-situ self-generated atmosphere synthesis and structure determination of MgSi(F,OH)6·2H2O

We have investigated the in-situ heating of MgSiF6.6H2O using self-generated atmosphere to attempt synthetizing new phases of general formula MgSi(OH,F)6.xH2O. We are presenting our results with the synthesis and structure determination of the new fluoride MgSi(OH,F)6.2H2O. Our results demonstrate that insitu diffraction experiment using self-generated atmosphere with quartz capillaries is a good technique for investigating new hydroxyfluoric hydrated phases.

Activated carbon adsorbent derived from waste biomass, “Croton caudatus” for efficient removal of 2-chlorophenol from aqueous solution: Kinetics, isotherm, thermodynamics and DFT simulation

The present study aims to prepare an activated carbon (AC) adsorbent developed from Croton caudatus biomass material for the adsorption of 2-chlorophenol (2CP) from wastewater. Activated carbon was prepared by KOH activation at 2:1 impregnation ratio and 700 °C temperature using a muffle furnace under self-generated atmosphere for 2 h. Several techniques and methodologies such as proximate analysis, ultimate (CHNS) analysis, BET, SEM, FT-IR, XRD and point of zero charge (pHpzc) have been used to determine physicochemical properties of the activated carbon. Batch adsorption studies were conducted for 2-chlorophenol adsorption and the optimum adsorbent dose, initial concentration, pH, reaction time and temperature were found to be 0.15 g/L, 80 mg/L, 4, 60 min and 298 K, respectively. The equilibrium isotherm study for 2-chlorophenol adsorption was fitted well to the Langmuir model with the adsorption capacity of 53.619 mg/g, while the adsorption kinetics was best described by pseudo-second order model. Thermodynamic parameters demonstrated a negative ΔH (exothermic) and negative ΔG (spontaneous) values. Studies on regeneration have shown that saturated carbon can be recycled up to five times with considerable removal efficiency. Besides, density functional theory (DFT) simulation revealed that the adsorption of 2-chlorophenol onto AC adsorbent is favorable. Among the oxygen-containing functional groups, the carboxyl group appeared to have a greater influence on the adsorption process than the hydroxyl and carbonyl groups with the highest negative Eadsorption of − 42.16 kJ/mol. Furthermore, the inclusion of three oxygen-containing functional groups improves the adsorption capacity of AC towards 2CP relative to a single functional group.

Preparation of FeCo/C-N and FeNi/C-N Nanocomposites from Acrylamide Co-Crystallizates and Their Use as Lubricant Additives.

FeCo and FeNi nanoalloy particles encapsulated in a nitrogen-doped carbonized shell (FeCo/C-N and FeNi/C-N) were synthesized by thermolysis at 400 °C of polyacrylamide complexes after frontal polymerization of co-crystallizate of Fe and Co or Ni nitrates and acrylamide. During the thermolysis of polyacrylamide complexes in a self-generated atmosphere, Co(II) or Ni(II) and Fe(III) cations are reduced to form FeCo and FeNi nanoalloy particles, while polyacrylamide simultaneously forms a nitrogen-doped carbon shell layer. This unique architecture provides high chemical and thermal stability of the resulting nanocomposites. The average crystallite size of FeCo and FeNi nanoparticles is 10 and 12 nm, respectively. The nanocomposites were studied by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The nanocomposites have been tested as antifriction and antiwear additives in lubricating oils. The optimal concentrations of nanoparticles were determined, at which the antifriction and antiwear properties of the lubricant manifest themselves in the best possible way.

Effect of sample mass on the apparent Arrhenius parameters observed for the thermal dehydration of sodium carbonate monohydrate

The dynamics of the thermal dehydration of sodium carbonate monohydrate was investigated using isothermal and non-isothermal thermogravimetric methods for sample masses between 1 and 10 mg in a 70 μl alumina cell. The apparent activation energy determined from isothermal measurements changed from 70 kJ mol−1 for 10 mg samples to 115 kJ mol−1 for 1 mg samples when the data was fit using the AE-2 mechanism. Fitting non-isothermal data using the Starink method produced apparent activation energies were constant within experimental error for 0.05 < α < 0.6 then decreased rapidly for α > 0.6 indicating there were at least two steps in the dehydration mechanism. The values found for 0.05 < α < 0.6 also depended on the sample mass and were 112, 105, and 100 kJ mol−1 for 1, 5 and 10 mg samples respectively. The experimental uncertainty in each of these measurements is ± 5 kJ mol−1. The Arrhenius parameters found for the dehydration reaction by extrapolating the isothermal reaction rates to zero mass where it was assumed that the rehydration reaction was not contributing to the dynamics were Ed = 116 ± 5 kJ mol−1 and Ad = 1.7 ± 0.9 * 1015 s−1. Since the activation energy determined is less than the value of 130 kJ mol−1 obtained using the thermochemical approach these values could still include a contribution from the rehydration reaction and represent a lower bound for these parameters. Using these values and other measured thermodynamic quantities gives Er = 57 ± 5 kJ mol−1 and Ar = 1.3 ± 0.9 * 107 s−1 for the rehydration reaction. This investigation clearly shows that self-generated atmospheres may affect the measured dynamics for a reversible reaction and should be considered when doing the analysis.

Metallopolymer hybrid nanocomposites: Preparation and structures

Several approaches for producing metallopolymer hybrid nanocomposites were developed and analyzed. Among of them one-stage synthesis of metal nanoparticles and stabilizing polymer matrix – conjugated thermal (co)polymerization of metal-containing monomers and following thermolysis of forming polymers; in situ reduction of metal ions either in epoxy resins by curing agents or in thermoplastics by thermal decomposition of metal-containing precursor; and post synthetic modification of coordination polymers are considered. Thermal transformations of metal-containing monomers possess the unique way for preparation of nanocomposite materials when metal (or their oxides and carbides) nanoparticles and a stabilizing polymer matrix are formed simultaneously in situ. Molecular and supramolecular organization of nanocomposites obtained can be controlled during the thermal transformation of such monomers in inert or self-generated atmosphere. The main advantage of the synthesis of composites by thermal transformation of metal-containing precursors is in the possibility of formation of nanocomposites with a relatively high concentration of metal phase. Another advantage deals with technological simplicity and the ease to control the processes and the properties of material obtained. The process includes three stages: dehydration, solid-phase polymerization, and pyrolysis of the polymer products formed. The approach makes it possible to adjust the mean particle size in a given range by just choosing the appropriate reaction conditions. The composition of metal nanoparticles, their size and distribution on the size as well as the type and thickness of polymer shell can be controlled on the stage of nanocomposite formation. The nanocomposites obtained reveal ferromagnetic behavior at room temperature with high coercive force and magnetic anisotropy. With aim to control the composition and structure (for example, core–shell type) of ferromagnetic nanomaterials obtained as well as their properties, the reaction conditions such as temperature, ratio of starting compounds, the type of polymer matrix can be varied.

Efficiency comparison of activated carbons prepared in inert and in self-generated atmospheres

ABSTRACT The present study intends to explore the role of the carbonization atmosphere nature on the textural, surface, and structural properties of a chemically activated carbon and hence on its adsorption efficiency in the gas phase. To attain this goal two activated carbons are prepared following the same activation procedure but using two different atmospheres. Thus, one of them is obtained in the presence of an inert gas while the other in a self-generated atmosphere. The pyrolysis is followed by thermogravimetric analysis and the so-obtained materials are characterized by means of nitrogen and water sorption, X-ray diffraction (XRD), Boehm titration, and Fourier transformed infrared spectroscopy (FTIR). Then, their performance toward cyclohexane adsorption is evaluated. The slight differences observed in the final properties of both materials are discussed herein and linked to the varied phenomena occurring during the activation in both conditions. However, and for the intended application, the results demonstrate that the presence of an inert atmosphere is not always required in order to obtain an efficient carbon, thus leading to a non-negligible saving in operational costs.

Effect of Gaseous Products on the Kinetics of Thermal Decomposition of Chloride-Containing Complex Ammonium Nitrate-Based Fertilizers

The results of studying the effect of gaseous products on the kinetics of thermal decomposition of chloride-containing complex ammonium nitrate-based fertilizers using the methods of thermogravimetry and differential scanning calorimetry are presented. The experimental data were analyzed with the Sestak–Berggren model fitting method and the isoconversion differential Friedman method. Based on the results of the studies, the dependences of the decomposition rate on the degree of decomposition are determined and a conclusion is drawn on the reasons of the influence of the self-generated atmosphere on the kinetics of exothermic decomposition.

Effect of Impurities on Thermal Decomposition Kinetics of Mineral Fertilizers Based on (NH4)2HPO4 in Self-Generated Atmosphere

The effect of impurities on the thermal decomposition kinetics of mineral fertilizers based on (NH4)2HPO4 in self-generated atmosphere was studied by the methods of thermogravimetry and differential thermal analysis. Results are presented of isothermal measurements made in the temperature range 100–110°C. An analysis of the experimental data made it possible to suggest reaction models of the decomposition and to reveal a dependence of the activation energy on the degree of decomposition. A strong deviation of the temperature dependence of rate constants from the Arrhenius law was observed. Conclusions were made on the basis of the study about the influence exerted by impurities on the thermal decomposition of mineral fertilizers based on (NH4)2HPO4 in the self-generated atmosphere and reasons for the deviation from the Arrhenius law.

The influence of water-soluble impurities on thermal dehydration kinetics of phosphogypsum in self-generated atmosphere

The paper presents the results of studies of the effect of water-soluble impurities on the thermal dehydration of phosphogypsum in a self-generated atmosphere, which are obtained by thermogravimetry and differential scanning calorimetry. For comparison, the results of the thermal dehydration of gypsum are given. The information about the change in activation energy depending on the extent of the dehydration and the effect of temperature on the mechanism of the dehydration is obtained by the use of integral isoconversional and model-fitting methods. It has been established that water-soluble impurities have a significant influence on the kinetics of the dehydration. It has been shown that in the thermal dehydration of gypsum an abnormal change in the reaction rate and activation energy is observed. In the dehydration of phosphogypsum, this phenomenon is not observed. This is due to the impact of the water-soluble impurities on the recrystallization of an intermediate amorphous phase during the thermal decomposition.

Adsorption Performance and Evaluation of Activated Carbon from Coconut Shell for the Removal of Chlorinated Phenols in Aqueous Medium

In this study, the removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solutions was performed using coconut shell activated carbon prepared by a two-stage self-generated atmosphere method. Coconut shell was first semi-carbonized at 300 °C for an hour followed by chemical activation with zinc chloride (ZnCl2) as activating agent at 500 °C for 2 h. The effect of impregnation ratio on the physical and chemical properties of activated carbons (ACs) was studied. The morphology and surface chemistry of the prepared carbons were characterized using Scanning Electron Microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR) respectively. The percentage of yield for the prepared AC was found to be in the range of 26.40-38.82 %. AC registered the highest adsorption capacity and was used in subsequent batch adsorption studies consisting of parameters such as initial concentration, adsorbent dosage and solution pH. The maximum surface area of the best produced AC was recorded as 1482 m2 g-1. The adsorption capacity was found to increase in proportional to the initial concentration and adsorbent dosage, while acidic solution pH was more favourable for the adsorption of 2,4-DCP by the prepared AC. The equilibrium time for the adsorption of 20 mg L-1 of 2,4-DCP on 0.5 g of AC was achieved in 180 min. Adsorption isotherms such as Langmuir, Freundlich and Temkin isotherm models were employed to examine the experimental isotherms while the reaction kinetic data was analysed using pseudo-first-order, pseudo-second-order and intraparticle diffusion model. The 2,4-DCP adsorption results fitted best in the Freundlich isotherm as indicated by the high correlation coefficient value (R2 > 0.9949) while the adsorption kinetic fitted to the pseudo second-order model (R2 > 0.9621).

Chlorinated phenol removal from aqueous media by tea (Camellia sinensis) leaf waste tailored activated carbon

In this study, activated carbons (ACs) wereprepared from tea leaves by using a two-stage self-generated atmosphere method. The process was done by semi-carbonizing the precursor at 300 °C for 1 h, followed by the impregnation of the resulting char at 85 °C for 4 h and finally activation at 500 °C for 2 h. The semi-carbonised samples were impregnated with different ratios of zinc chloride (ZnCl2) and their physicochemical effect was studied. The prepared ACs underwent several aspects of both, chemical and physical characterizations, such as the percentage of yield, moisture content, ash content, pH, porosity, adsorption capacity of 2,4-dichlorophenol (2,4-DCP), surface area, porosity, morphology and surface chemistry studies. It was found that sample AC2, with an impregnation ratio of 2:1 was the best AC produced in this study. The maximum Brunauer, Emmett and Teller surface area of AC2 was found to be 695 m2/g. Langmuir, Freundlich and Temkin isotherm models were used to examine the experimental isotherms while the kinetic data was analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. The 2,4-DCP adsorption isotherm results complied well to the Langmuir isotherm for the equilibrium data while the adsorption kinetic data fitted well to the pseudo-second order model, indicating that chemisorption by valency forces via the sharing (covalent bond) or exchanging of electrons between the AC and the 2,4-DCP molecules were mainly responsible for the adsorption process. From these findings, it is concluded that tea leaves can be used as a low cost precursor for the removal of 2,4-DCP in aqueous medium.

Removal of chlorinated phenol from aqueous solution utilizing activated carbon derived from papaya (Carica Papaya) seeds

Activated carbons (ACs) were prepared from papaya seeds with different dry weight impregnation ratios of zinc chloride (ZnCl2) to papaya seeds by using a two-stage self-generated atmosphere method. The papaya seeds were first semi-carbonized in a muffle furnace at 300 °C for 1 h and then impregnated with ZnCl2 before activation at 500 °C for 2 h. Several physical and chemical characteristics such as moisture, ash, pH, functional groups, morphological structure and porosity of prepared ACs were studied and presented here. AC2, with the impregnation ration of 1: 2 (papaya seeds: ZnCl2), yielded a product that had the highest adsorption capacity, 91.75%, achieved after 180min contact time. The maximum Brunauer, Emmett and Teller (BET) surface area of AC2 was 546m2/g. Adsorption studies indicated that AC2 complied well with the Langmuir isotherm (qm=39.683mg g−1) and the pseudo-second-order (qe=29.36mg g−1). This indicated that chemisorption was the primary adsorption method for AC2. The intraparticle diffusion model proved that the mechanism of adsorption was separated into two stages: the instantaneous stage and the gradual adsorption stage. Overall, this work demonstrated the suitability of using papaya seeds as a precursor to manufacture activated carbon.

A novel gas separation integrated membrane bioreactor to evaluate the impact of self-generated biogas recycling on continuous hydrogen fermentation

A Gas Separation Membrane Bioreactor (GSMBR) by integrating membrane technology with a continuous biohydrogen fermenter was designed. The feasibility of this novel configuration for the improvement of hydrogen production capacity was tested by stripping the fermentation liquor with CO2- and H2-enriched gases, obtained directly from the bioreactor headspace. The results indicated that sparging the bioreactor with the CO2-concentrated fraction of the membrane separation unit (consisting of two PDMS modules) enhanced the steady-state H2 productivity (8.9–9.2 L H2/L-d) compared to the membrane-less control CSTR to be characterized with 6.96–7.35 L H2/L-d values. On the other hand, purging with the H2-rich gas strongly depressed the achievable productivity (2.7–3.03 L H2/L-d). Microbial community structure and soluble metabolic products were monitored to assess the GSMBR behavior. The study demonstrated that stripping the bioH2 fermenter with its own, self-generated atmosphere after adjusting its composition (to higher CO2-content) can be a promising way to intensify dark fermentative H2 evolution.

Fabrication and characterization of metal-core carbon-shell nanoparticles filling an aeronautical composite matrix

Metal nanoparticles (NPs) were prepared from acrylamide complex of iron and nickel nitrates by controlled thermolysis at constant temperature in a self-generated atmosphere and used to fabricate epoxy resin nanocomposites. X-ray diffraction performed on the nanoparticles revealed a metal core/polymeric shell structure for the nanoparticles thermolysed at higher temperature as also confirmed by cross analysis of thermo-gravimetrical and vibrating magnetometer data. Optical microscopy was used to investigate the achieved dispersion of the nanoparticles within the uncured resin and transmission electronic microscopy was used to analyse the morphology and the average dimensions of the nanoparticles. Thermal stability of manufactured nanocomposites was studied by thermo-gravimetric analysis in inert and oxidative conditions, reporting that negligible variations are induced by the presence of nanofillers. A complete thermo-mechanical and fracture characterization was carried out to assess the effect of nanoparticles on final nanocomposite system. A slight increase of the modulus is recorded at room temperature whereas a significant variation is induced for higher temperature. The presence of nanoparticles induces a global increase in the fracture energy of nanocomposite associated to different failure mechanisms. Magnetic data indicate that iron particles based nanocomposites display room-temperature ferromagnetic behaviour with saturation magnetization and coercivity depending on the diameter of the metal core.

Preparation and Characterization of Activated Carbon from Waste Rubber Tires: A Comparison between Physical and Chemical Activation

Abstract. Waste tires, which are an abundant waste product of the automobile industry, were used to prepare activated carbon by means of physical and chemical activation. A two-stage process was used, with a semi-carbonization stage as the first stage, followed by an activation stage as the second stage.All experiments were conducted in a laboratory-scale muffle furnace under static conditions in a self-generated atmosphere. During this process, the effects of the parametric variables of semi-carbonization time (for the physical activation process), activation time and temperature and impregnation ratios (for the chemical activation process) on the percentage yield were studied and compared. Varying these parametric variables yielded interesting results, which in turn affected the adsorption process of 2,4-DCP, which was the simulated pollutant in aqueous form. The optimized percentage yields of activated carbon that were obtained were 41.55% and 44.88% ofthe physical and chemical activation treatment processes respectively.Keywords: Physical activation, chemical activation, waste rubber tires, 2,4-dichlorophenol, activated carbon.

Cleaner production of porous carbon from palm shells through recovery and reuse of phosphoric acid

The work attempts to understand the effect of process condition on the acid recovery in the process of porous carbon preparation using phosphoric acid as the activating agent from palm shells precursor. Additionally the effect of reusability of the recovered acid on the textural characteristics and the yield of porous carbon were assessed. Although the economics of this process largely depends on the effective recovery and reuse of acid, none of the earlier work attempted a systematic study on the recovery and reuse of phosphoric acid. The activation was performed covering an activation temperature of 375–525 °C in a self-generated atmosphere. The effectiveness of reclaimed acid was assessed for three cycles covering an activation temperature between 325 and 525 °C. The activation process resulted in an acid loss of 20–25% for the activation temperature in the range of 325–475 °C, while at 525 °C it was in the range of 30–35%. The percentage loss marginally increased with subsequent activations using the reclaimed acids. The reclaimed phosphoric acid was found to have almost similar activation capabilities as that of fresh acid in terms of yield and textural characteristics of the activated carbon. At an activation temperature of 475 °C, the reclaimed phosphoric acid in all three subsequent usages resulted in a carbon with Brunauer–Emmett–Teller (BET) surface area and pore volume of approximately 2000 m2/g and 1.2 cm3/g. However a drastic reduction in the surface area was observed with the reclaimed phosphoric acid at an activation temperature of 525 °C with BET surface area dropping from 2153 to 941 m2/g with the reagent recycled thrice.

Preparation and characterization of activated carbon from Typha orientalis leaves

Background In this study, activated carbon (AC) was prepared from Typha orientalis or commonly known as cattail leaves using physical and chemical activation phosphoric acid (H3PO4), as dehydrating agent. A two-stage process was used, i.e., semi-carbonization stage at 200 °C for 15 min as first stage followed by second stage activation, at 500 °C for 45 min. The precursor material with the impregnated agent was exposed straight away to semi-carbonization and activation temperature using a laboratory scale muffle furnace (Carbolite RHF 1500, England) under static condition in a self-generated atmosphere.

Heat-field-stimulated decomposition reaction in Cu2ZnSnS4

Thermal stability is essential for the potential solar cell material Cu2ZnSnS4 (CZTS) in achieving a satisfactory photovoltaic device performance. Although the loss of Sn from CZTS has been reported, the basic decomposition mechanism of a CZTS system has not been well established yet, especially with regard to the role of active Cu1+ ions. This paper not only provides a deeper understanding of the change of Sn species, which includes an equimolar–isobaric vaporization mode transition and a solid–vapor phase transition in a self-generated atmosphere, but also reveals the oxidation state alternation (Cu1+/Cu2+) and transfer mechanism of Cu species through carefully designed experiments and a reaction kinetic study. Cu ions are unexpectedly found to be active in affecting the degradation reaction by valance alternation and ion movement upon the application of a heat field to balance the derivation caused by a non-uniform temperature gradient. As a result, a Cu–Zn separation appears, with Cu accumulating near the hot area and Zn near the cold area. A decomposition reaction model of CZTS under a directional heat field is proposed to describe the elemental and electronic state change in atomic scale, and a perfect match is obtained between the model and the experimental results. This paper paves a way to solve the thermal stability issue of Cu2ZnSnS4.