Effect Of Activation Method Research Articles

Preparation of porosity-adjustable porous adsorbent materials derived from coal solid waste

Coal solid waste (CSW) was explored as precursor to prepare porous adsorption material (ACSW) by carbon dioxide activation. The effects of activation method (direct activation and pre-carbonization followed by activation), activation temperature, and activation time were systematically investigated. The burn-off characteristics of the CSW were measured, the ACSW were characterized by field emission scanning electron microscope, gas adsorption instrument and Raman spectrometer, and, in parallel, the adsorption ability was studied using methylene blue (MB) as a typical pollutant. The results showed that compared with direct activation, pre-carbonization reduced the carbon loss, increased the pore volume with pore size less than 1 nm, improved the carbon structural order and increased the MB adsorption performance. In addition, the evolution of the structure of the ACSW strongly depended on the activation temperature and time. With the increase of the activation time, the pore structure evolution underwent three stages: pore forming, expanding, and collapsing. Pore forming mainly involved clearing scattered graphite structures and amorphous carbon. Pore expanding mainly relies on consumption of regular graphite carbon crystal structure. At low temperature of 800 °C, micropores fully developed. As the activation temperature increased to 850–900 °C, pore expansion became apparent, mainly forming pores of 1–5 nm. Moreover, the MB adsorption capacity was positively correlated with the pore volume with pore size less than 5 nm. The burn-off can serve as an indicator for evaluating pore structure and the adsorption performance and when it was ∼25.5 %, the ACSW had the largest pore volume with pore size less than 5 nm and the highest MB adsorption capacity.

Cellulose-Amine Porous Materials: The Effect of Activation Method on Structure, Textural Properties, CO2 Capture, and Recyclability.

CO2 capture via physical adsorption on activated porous carbons represents a promising solution towards effective carbon emission mitigation. Additionally, production costs can be further decreased by utilising biomass as the main precursor and applying energy-efficient activation. In this work, we developed novel cellulose-based activated carbons modified with amines (diethylenetriamine (DETA), 1,2-bis(3-aminopropylamino)ethane (BAPE), and melamine (MELA)) with different numbers of nitrogen atoms as in situ N-doping precursors. We investigated the effect of hydrothermal and thermal activation on the development of their physicochemical properties, which significantly influence the resulting CO2 adsorption capacity. This process entailed an initial hydrothermal activation of biomass precursor and amines at 240 °C, resulting in C+DETA, C+BAPE and C+MELA materials. Thermal samples (C+DETA (P), C+BAPE (P), and C+MELA (P)) were synthesised from hydrothermal materials by subsequent KOH chemical activation and pyrolysis in an inert argon atmosphere. Their chemical and structural properties were characterised using elemental analysis (CHN), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The calculated specific surface areas (SBET) for thermal products showed higher values (998 m2 g-1 for C+DETA (P), 1076 m2 g-1 for C+BAPE (P), and 1348 m2 g-1 for C+MELA (P)) compared to the hydrothermal products (769 m2 g-1 for C+DETA, 833 m2 g-1 for C+BAPE, and 1079 m2 g-1 for C+MELA). Carbon dioxide adsorption as measured by volumetric and gravimetric methods at 0 and 25 °C, respectively, showed the opposite trend, which can be attributed to the reduced content of primary adsorption sites in the form of amine groups in thermal products. N2 and CO2 adsorption measurements were carried out on hydrothermal (C) and pyrolysed cellulose (C (P)), which showed a several-fold reduction in adsorption properties compared to amine-modified materials. The recyclability of C+MELA, which showed the highest CO2 adsorption capacity (7.34 mmol g-1), was studied using argon purging and thermal regeneration over five adsorption/desorption cycles.

Activation methods increase biochar's potential for heavy-metal adsorption and environmental remediation: A global meta-analysis

Removal of heavy metals (HMs) by adsorption on biochar's surface has shown promising results in the remediation of contaminated soil and water. The adsorption capacity of biochar can be altered by pre- or post-pyrolysis activation; however, the effect of activation methods on biochar's adsorption capacity varies widely. Here, we conducted a meta-analysis to identify the most effective methods for activation to enhance HM removal by biochar using 321 paired observations from 50 published articles. Activation of biochar significantly improves the adsorption capacity and removal efficiency of HMs by 136 and 80 %, respectively. This study also attempts to find suitable feedstocks, pyrolysis conditions, and physicochemical properties of biochar for maximizing the effect of activation of biochar for HMs adsorption. Activation of agricultural wastes and under pyrolysis temperatures of 350–550 °C produces biochars that are the most effective for HM adsorption. Activation of biochars with a moderate particle size (0.25–0.80 mm), low N/C (<0.01) and H/C ratios (<0.03), and high surface area (> 100 m2 g−1) and pore volume (> 0.1 cm3 g−1) are the most desirable characteristics for enhancing HM adsorption. We conclude that pre-pyrolysis activation with metal salts/oxides was the most effective method of enhancing biochar's potential for adsorption and removal of a wide range of HMs. The results obtained from this study can be helpful in choosing appropriate methods of activations and the suitable choice of feedstocks and pyrolysis conditions. This will maximize HM adsorption on biochar surfaces, ultimately benefiting the remediation of contaminated environments.

Activated carbon from hydrolysis lignin: Effect of activation method on carbon properties

This study presents the effects of different activation methods to produce activated carbon from the hydrolysis lignin. Pretreatment of the feedstock with common mineral acids (HCL, HNO3, and H3PO4), different steam rates for physical activation, and different chemical activating agents (ZnCl2, Na2CO3, and KOH) for chemical activation were investigated. The pretreated biomass was carbonized and activated in one-stage process and the surface characteristics, such as total pore volume, pore size distribution and specific surface area, were investigated. The results showed that the activated carbon surface properties were not greatly affected by acid pretreatment. Brunauer-Emmett-Teller (BET) surface areas as high as 616 m2/g could be achieved with physical activation and 2054 m2/g with chemical activation. Different steam rates in the selected interval (0.5–2 cm3/min) did not change the pore size distribution but had small positive effect on the specific surface area, while chemical activation with ZnCl2 increased the mesoporosity, and activation with KOH increased the microporosity and oxygen groups in the form of ether and alcohol bonds.

Removal of gaseous H2S using microalgae porous carbons synthesized by thermal/microwave KOH activation

H2S has strong toxicity and corrosivity, which can endanger human health and corrode equipment. This article used the two types of activation methods as a comparison to activate raw biochar from microalgae pyrolysis to prepare microalgae porous carbon for removal of gaseous H2S. The difference in textural properties and functional group of the prepared microalgae porous carbon using two types of activation methods is studied emphatically. Then physicochemical property of microalgae porous carbons was characterized and effect of activation methods, KOH/raw biochar mass ratio and sorption temperature on desulfurization was tested. Sorption products, mechanism, kinetics and thermodynamics were studied. Reuse of deactivated adsorbents was also explored. Research revealed that both activation methods substantively improved pore structure and increased active functional group contents of raw biochar, greatly promoting desulfurization. Compared to thermal activation, active functional groups of microalgae porous carbons prepared by microwave-assisted activation had no obvious difference, but pore structure was greatly improved, leading to higher H2S sorption capacity. Results of product characterization, thermodynamics and kinetics demonstrated that in the H2S sorption process, physical sorption was major and chemical sorption was auxiliary. Spent containing-sulfur microalgae porous carbons showed good Hg0 capture ability, far exceeding commercial activated carbon.

Erratum: “Effects of activation method and temperature to III-nitride micro-light-emitting diodes with tunnel junction contacts grown by metalorganic chemical vapor deposition” [Appl. Phys. Lett. 119, 202102 (2021)

Erratum: “Effects of activation method and temperature to III-nitride micro-light-emitting diodes with tunnel junction contacts grown by metalorganic chemical vapor deposition” [Appl. Phys. Lett. <b>119</b>, 202102 (2021)

Effects of activation method and temperature to III-nitride micro-light-emitting diodes with tunnel junction contacts grown by metalorganic chemical vapor deposition

The optical and electrical characteristics of InGaN blue and green micro-light-emitting diodes (μLEDs) with GaN tunnel junction (TJ) contacts grown by metalorganic chemical vapor deposition (MOCVD) were compared at different activation temperatures among three activation methods from the literature, namely, sidewall activation, selective area growth (SAG), and chemical treatment before sidewall activation. The devices with chemical treatment before activation resulted in uniform electroluminescence and higher light output power, compared to the devices with sidewall activation and SAG. Moreover, the green μLEDs showed greater optical degradation at elevated activation temperatures, whereas the blue μLEDs yielded trivial difference with activation temperatures from 670 to 790 °C. The 5 × 5 μm2 devices with chemical treatment before activation and SAG yielded almost identical voltage at 20 A/cm2, and the voltage penalty significantly decreased with activation temperature in the case of devices with sidewall activation. The devices with chemical treatment before activation resulted in higher external quantum efficiency (EQE) and wall-plug efficiency (WPE) in low current density range compared to the devices with SAG. The enhancements in EQE and WPE were observed in different μLED sizes, suggesting that chemical treatment before sidewall activation enables the use of TJ contacts grown by MOCVD and is advantageous for applications that require high brightness and efficiency.

Effect of Activation Methods on the Supercapacitor Performance of Hydrochar Derived from Oil Palm Empty Fruit Bunch

In this study, the activated carbon (AC) derived from oil-palm empty fruit bunches (EFB) for using in effective supercapacitor application was carried out by two main steps namely hydrothermal carbonization and activation with three different activated agents steam, carbon dioxide and potassium hydroxide for increase of the AC’s specific area. The fabricated AC had surface area of 246.9 – 809.7 m2/g which were extremely higher as compared to the non-activated carbon i.e., 1.1 m2/g. It is concluded that the chemically AC afforded the best material and showed the high specific capacitance of 101.1 F/g at the scan rate of 5 mV/s with 1 M Na2SO4 as neutral electrolyte over the three-electrode cell. The study revealed that EFB could be considered as a promising potential electrode for supercapacitor.

Degradation of the UV-filter benzophenone-3 in aqueous solution using persulfate activated by heat, metal ions and light

The goals of this study were to bring forward new data and insights into the effect of activation methods, operational variables and reaction pathways during sulfate radicals-based oxidation of benzophenone-3 (BP-3) in aqueous solution. Heat, transition metal ions (Fe2+, Cu2+, Co2+), UV and visible light irradiation were used to activate persulfate (PS) to degrade BP-3. The results showed that these three activation methods can remarkably enhance BP-3 removal efficiency. Under the conditions of [BP-3]0: [PS]0 = 1: 500, pH = 7.0, and 40 °C, complete removal of BP-3 (1.31 μM) was observed in 3 h. In the pH range of 3.0–9.0, the degradation of BP-3 decreased with increasing pH. Increasing the PS dosage accelerated the reaction, while the presence of humic acid (HA) significantly inhibited the efficiency of BP-3 removal. Based on electron paramagnetic resonance (EPR) and radical quenching studies, sulfate and hydroxyl radicals contributed to the oxidation process. According to the evolution of BP-3 and its 7 by-products, as well as frontier electron densities (FED) calculation, two routes were proposed involving hydroxylation, demethylation and direct oxidation. On the whole, this work is a unique contribution to the systematic elucidation of BP-3 removal by PS.

The effects of activation method on the pore structure and electrochemical properties of ordered mesoporous carbons used as the electrode materials of supercapacitors

The effects of activation method on the pore structure and electrochemical properties of ordered mesoporous carbons used as the electrode materials of supercapacitors

The effect of activation methods on the electrochemical performance of ordered mesoporous carbon for supercapacitor applications

Ordered mesoporous carbon (CMK-3) was fabricated by a simple nanocasting method using SBA-15 as a hard template. The CMK-3 had a two-dimensional hexagonal mesoporous structure and a specific surface area of approximately 975.9 m2 g−1. The CMK-3 was modified by HNO3 solutions with magnetic stirring and ultrasonic activation, respectively, to explore the influence of various activation methods on pore structure, surface state, morphology, and electrochemical performance. The CMK-3 modified by ultrasonic activation (CMK-3-US) reached the optimal specific capacitance of 233.4 A g−1 at 0.5 A g−1 and retained 94.2% after 500 cycles in 3 M KOH electrolyte. Furthermore, a symmetric supercapacitor was successfully assembled using CMK-3-US electrodes, which delivered an excellent energy density of 21.5 Wh kg−1 at a power density of 225 W kg−1 and exhibited great long-term stability with 97.5% retention after 4000 cycles. Compared to magnetic stirring activation, ultrasonic cavitation could better increase the efficiency of the HNO3 activation for mesoporous carbon particles. The results indicate ultrasonic activation is an efficient way to modify carbon-based electrode materials for supercapacitors.

Effects of activation method and mental effort on touchscreen task performance for users with and without upper extremity motor control disabilities

The rise in popularity of touchscreens supports the need for improving the usability and accessibility of the technology for users with varying abilities. Touchscreen activation methods (tapping, take-off) can help address these issues but may have trade-offs (longer time to complete task). This study evaluated tapping and take-off touchscreen activation methods during a multi-item selection activity. Participants with (n = 10) and without (n = 10) motor control disabilities affecting upper extremity function (+MCD and źMCD, respectively) completed an experimental task to select four items from a list using either tapping or take-off activation with two different levels of mental effort (memorization vs. no memorization). Fewer errors (29 vs. 21 %, p = .018) but longer task completion times (14.3 vs. 9.04 s, p = .007) were observed for take-off vs. tapping. Error rate doubled for memorization compared to no memorization (33.5 vs. 16.5 %, p = .002). Both +MCD and źMCD groups had fewer errors using the take-off method, but tapping was preferred, had fewer misses and required less task completion time during a menu selection activity. For tablet touchscreen menu selection applications for individuals with and without upper extremity motor control disabilities, take-off activation method is more accurate than tapping though tapping is preferred, has fewer misses and requires less task completion time. Additional mental demand leads to an increase in the number of errors during touchscreen operation.

Production of activated carbons from biodegradable waste materials as an alternative way of their utilisation

New carbonaceous adsorbents were prepared by means of direct, physical and chemical activation of corn cobs and cherry stones as well as coffee and tobacco industry waste materials. The effect of activation method on the textural parameters, acid-base character of the surface and sorption properties toward toxic gases of the materials obtained was tested. Depending on the precursor as well as method of preparation, the final products were micro/mesoporous activated carbons of surface area reaching to 1426 m2/g, showing largely different acid-base properties of the surface. The results obtained in our study have proved that a suitable choice of the activation procedure for industrial and agricultural biodegradable waste materials permits production of cheap carbonaceous adsorbents with very high sorption capacity towards nitrogen dioxide and hydrogen sulphide reaching to 83 mg NO2/gads and 215 mg H2S/gads, respectively.

Практикоориентированное обучение и воспитание студентов-юристов младших курсов в вузе

The article is the analysis of effectiveness of active methods of studying of law. The experience of organizing visiting session of courts and their conduct in the university is analyzed here. The work of the student’s group of promoting the rule of law as a means of legal education is studied in the paper.

Sorption Properties of Carbonaceous Adsorbents Obtained by Pyrolysis and Activation of Pistachio Nut Shells

A series of carbonaceous adsorbents was obtained by physical and chemical activation of pistachio nut shells. The effect of activation method on the textural, acid–base and adsorption properties of the materials obtained was tested. The materials prepared were characterized by iodine and methylene blue removal at room temperature. Depending on the procedure of activation, the final products were microporous activated carbons of surface area varying from 530 to 1204 m2/g, exhibiting diverse acidic–basic surface character. The results obtained in this study prove that a suitable choice of the activation procedure for agricultural waste materials permits production of low-cost adsorbents characterized by very high adsorption capacity towards iodine and methylene blue (1280 and 400 mg/g, respectively).

Remediation HCHs POPs-contaminated soil by activated persulfate technologies: Feasibility, impact of activation methods and mechanistic implications

Hexachlorocyclohexanes (HCHs) waste stockpiles are the single largest source of POPs. Sites contaminated with high levels of HCHs pose serious threats to public health and environmental safety, but there remains a lack of proper environmentally sound solution. To provide guidance on this issue, the remediation of contaminated soil with high levels of γ-HCH (∼800mg/kg) by persulfate with three commonly applied field activation methods, namely heat activation at 40°C, high pH and Fe(III)-EDTA activation, was investigated. The effects of activation method and persulfate dosage on the degradation and dechlorination of γ-HCH were studied, and degradation pathways were proposed. The results show that heat-activated persulfate is highly effective for the remediation of γ-HCH, achieving complete degradation and dechlorination of γ-HCH in 14days. Under high pH conditions, γ-HCH rapidly dehydrochlorizes into trichlorobenzenes, which are further degraded by persulfate. On the other hand, persulfate alone at 20°C and Fe(III)-EDTA activated persulfate are not effective for the degradation of γ-HCH, due to limited generation of reactive radical species resulting from the inefficient activation of persulfate, and the competition of soil organic materials and Fe(III)-EDTA with γ-HCH for reactive radicals.

The Effect of Activation Method on the Adsorption Performance of Saw-Dust Activated Carbon

Aims: The present study was conducted to evaluate the ability of modified saw dust to remove para - nitrophenol (PNP) from aqueous solution. Metho dology: Batch adsorption studies were carried out under varying conditions of initial pH, contact time and temperature . The performance of saw dust activated carbon was characterized by BET surface area FTIR and SEM. Three simplified kinetic models including pseudo - first order, pseudo - second order and intra particle diffusion were selected to follow the adsorption process. P lace and Duration of Study : Experiments were carried out in the National Rese arch Center, Department of Physical Chemistry at laboratory of Surface Chemistry and Catalysis. Study Design : The adsorption abilities of saw dust after thermal and chemical treatment were investigated for its efficiency in removing para - nitrophenol (PNP) from aqueous solution. Results: The Langmuir, Freundlich and Temkin models were used to describe the adsorption equilibrium studies of saw dust activated carbon. Results showed that the Langmuir isotherm showed better fit than Freundlich and Temkin isother m. The kinetic data were found to follow the pseudo - second order model. Intraparticle diffusion is not the sole rate controlling factor. The

Production, characterization, and evaluation of activated carbons from de-oiled canola meal for environmental applications

The objective of this study was the utilization of waste canola meal to produce activated carbons for environmental applications. Activated carbons were produced from de-oiled canola meal (DOCM) by slow-pyrolysis followed by physical (steam and CO2) and chemical (NH3 and KOH) activations. Physico-chemical characteristics of the precursor and activated carbons were investigated using BET, FTIR, SEM, TGA, Boehm, CHNSO, and particle size analysis. The effect of activation methods on porous structure and surface chemistry of activated carbons was investigated. Activated carbons produced from canola meal were evaluated for their efficiency as adsorbents for ammonium ion adsorption from aqueous solutions. The effect of pH, surface area, and surface functional groups of activated carbons was examined on adsorption of ammonium ion at 260.0mg/L. The role of both porous structure and surface functionality of activated carbons was studied as a function of adsorption of ammonium ion. The results showed that the maximum adsorption (qe) of ammonium ion was 55.4mg/g for steam activated carbon, 17.9mg/g for CO2 activated carbon, 56.7mg/g for ammonia-treated activated carbon, and 148mg/g for KOH activated carbon.

Effect of activation methods on the surface properties of carbonized biomass derived from fluted pumpkin stem (&lt;i&gt;Telfairia occidentalis Hook&lt;/i&gt; F) waste

The effect of chemical activation methods on some surface properties of carbonized biomass produced from fluted pumpkin waste was investigated using three activating reagents: H3PO4, ZnCl2 and H2O2. The surface properties studied were moisture content, sodium sorption capacity and iodine number. The surface properties of activated carbon were compared with that of the pure carbonized sample. The results obtained shows that the sample activated with H3PO4 (AM) with a sodium sorption capacity of 1.52 mmol/g was the most effective for the adsorption of sodium and other cations from solution, while the sample activated with ZnCl2 (BM) with sodium sorption capacity of 1.07 mmol/g has the least affinity for sodium. The iodine number determination also shows that the sample activated with H2O2 (NM) has the highest porosity with an iodine number of 60.3 mg/g I2. This implies that chemically activated carbon produced from fluted pumpkin waste could be utilized as low-cost, economic and environment friendly biosorbents for the removal and recovery of metals and other cations in solution.Keywords: Activated carbon, activation methods, surface property, fluted pumpkin.

Effect of Activation Method on the HDS Activity of Unsupported CoMoS Catalysts Prepared from a Novel Precursor

Unsupported Co promoted MoS2 catalysts for the hydrodesulfurization (HDS) reaction were prepared using a mixture of Co(dien)2MoS4 (dien = diethylenetriamine) and tetrapropylammonium thiomolybdate. The mixture was first treated in a high energy ball mill followed either by ex situ activation in forming gas or by in situ activation during the HDS reaction. The ex situ activation mode leads to a very active catalyst exhibiting 84.9 % conversion of dibenzothiophene within 5 h. The in situ activated catalyst is less active but still shows a remarkable performance. Transmission microscopy investigation demonstrates that in the ex situ activated catalyst the stacking of MoS2 slabs is lower than in the in situ obtained material, which is corroborated by Raman measurements on the materials. In addition, the average MoS2 slab length of the former sample is significantly shorter than for the latter material. During the in situ activation, crystalline Co9S8 is formed which may be a reason for the lower HDS activity. The chemical composition of the two catalysts is also different, with larger carbon and sulfur contents found for the in situ-formed sample. The deposition of carbon and sulfur on the surface of the catalyst may also account for the lower catalytic activity, compared to the ex situ obtained material. A conversion rate of dibenzothiophene in the HDS reaction is observed for an ex situ activated catalyst prepared using a new precursor material.