Non-activated Sample Research Articles

Preparation of Activated Carbon from Cassava Stem as a Adsorbent of Antibiotics Pollutants in Water

The aim of this research was to prepare activated carbon from cassava stem by chemical activation method using potassium hydroxide as activating agent with different pyrolysis temperatures (500, 600, 700 và 800 oC). All activated carbon samples (AC) provide the higher specific surface area than the non-activated carbon sample. The activated carbon (AC-7) sample prepared at 700 oC with the maximum specific surface area of 1643 m2/g and pore volume of 1.0293 cm3/g. The obtained activated carbon was used in the removal of tetracycline (TC) in water. The maximum adsorption capacity of AC-7 for TC reachered 357,14 mg/g. This value was higher other materials, the improved adsorption capacity of AC-7 could be explained the presence of mesopores with high specific surface area after KOH activation could be significantly improved the adsorption performance of the activated carbon materials. The result show the potential of AC in removing polluted antibiotics.

Activated Iron-Porous Carbon Nanomaterials as Adsorbents for Methylene Blue and Congo Red.

The adsorption properties of microporous carbon materials modified with iron citrate were investigated. The carbon materials were produced based on resorcinol-formaldehyde resin, treated in a microwave assisted solvothermal reactor, and next carbonized in the tube furnace at a temperature of 700 °C under argon atmosphere. Iron citrate was applied as a modifier, added to the material precursor before the synthesis in the reactor, in the quantity enabling to obtain the nanocomposites with C:Fe mass ratio equal to 10:1. Some samples were additionally activated using potassium oxalate or potassium hydroxide. The phase composition of the produced nanocomposites was determined using the X-ray diffraction method. Scanning and transmission electron microscopy was applied to characterize the changes in samples' morphology resulting from the activation process and/or the introduction of iron into the carbon matrix. The adsorption of nitrogen from gas phase and dyes (methylene blue and congo red) from water solution on the obtained materials was investigated. In the case of methylene blue, the adsorption equilibrium isotherms followed the Langmuir isotherm model. However, in the case of congo red, a linear dependency of adsorption and concentration in a broad equilibrium concentration range was found and well-described using the Henry equation. The most efficient adsorption of methylene blue was noticed for the sample activated with potassium hydroxide and modified with iron citrate, and a maximum adsorption capacity of 696 mg/g was achieved. The highest congo red adsorption was noticed for the non-activated sample modified with iron citrate, and the partition coefficient for this material equaled 171 dm3/g.

Investigation of physicochemical processes taking place in chemically activated very high volume fly ash mixtures

In order to reduce the negative impact of cement production on the natural environment, and in particular to reduce CO2 emission, new types of binders are sought. It is beneficial to use supplementary cementitious materials, such as fly ash. A very high volume of fly ash and a reduced amount of cement in the binder can, however, result in deterioration of some properties of the final composite. Such systems require activation. The aim of this work was to investigate the effects of different activators: spent aluminosilicate catalyst (very active pozzolanic material), Na2SO4 and Ca(OH)2 on the hydration/activation processes and development of 28-day compressive strength of the blends containing a very high volume of fly ash. Activators were introduced into the system in various combinations: alone or in mixtures. The following research methods were used: calorimetry, thermal analysis, X-ray diffraction and IR spectroscopy. It was shown that each type of activation accelerates cement hydration, improves pozzolanic activity and increases compressive strength compared to the results of non-activated reference sample. However, the activation kinetics and mechanism of interaction are different for different activators. The most promising results were obtained for the combination of three activators: spent aluminosilicate catalyst, Na2SO4 and Ca(OH)2.

Conversion of waste biomass to designed and tailored activated chars with valuable properties for adsorption and electrochemical applications.

Waste biomass, a renewable energy source, is inexpensive material that has great potential in sorption and electrochemical application. The selected waste materials (corncobs, coconut shells, walnuts, and pistachio husks) allow to close the production cycle and enable material recycling, which are important aspects in the hierarchy of waste management. The proposed methodology for production and activation of biochars can be used industrially due to highly porous structure, developed surface area, and sorption ability of the obtained activated carbons (AC). A significant increase (from 4 up to more than 10 times) in specific surface area (SSA) is observed for all samples after the CO2 activation process (0.5 h at 800 °C) up to 725 m2 g-1 for corncobs, 534.9 m2 g-1 for pistachio husks, 523 m2 g-1 for coconut shells, and 393 m2 g-1 for walnut husks. The highest value of SSA is achieved for the AC derived from corncobs. This material is evaluated for use as an adsorbent, revealing 99% removal of Rhodamine B (dye/AC ratio of 0.0017) and 69% removal of chromium (dye/AC ratio of 0.0028). Based on the adsorption kinetics analysis, it is demonstrated that the Cr(VI) undergoes physical adsorption, while RhB undergoes chemisorption. In addition, corncob-derived AC exhibits superior electrochemical performance in 6 M KOH compared to the nonactivated biochar. A specific capacitance of 70 F g-1 at 5 A g-1 is achieved, along with outstanding rate capability (45 F g-1 at 50 A g-1) and cycling stability (94% at 10 A g-1 after 10,000 cycles). In contrast, the nonactivated sample shows only 34 F g-1 at 5 A g-1 and 13 F g-1 at 50 A g-1, with a stability of 91.4%.

Activation of nickel foam, as a current collector of a supercapacitor, by impact nickel plating: influence of treatment conditions

Nickel foam is widely used as a current lead/current collector and as the base of nickel hydroxide electrodes for hybrid supercapacitors. An investigation of the influence of activation conditions for a commercial sample of nickel foam produced by Linyi Gelon LIB Co Ltd (China) was carried out using the method of impact nickel plating. The morphology of activated and non-activated nickel foam samples was investigated by scanning electron microscopy. Activated and non-activated nickel foam samples were investigated by methods of cyclic voltammetry and galvanostatic charge-discharge cycling in the supercapacitor mode. It was shown that upon activation at i=1 A/dm2 and τ=10 min, a thin layer of porous nickel with incomplete coverage was formed. Activation with impact nickel at i=7 A/dm2 and τ=3 min revealed the formation of a nickel coating with a highly developed surface, on which local cracks were found as a result of the accumulation of internal stresses. Activation with impact nickel at i=1 A/dm2 and τ=10 min led to the formation of a coating with a highly developed surface, with significant peeling of the coating. Cyclic voltammetry showed high efficiency of impact nickel activation at i=7 A/dm2, τ=3 min, and i=20 A/dm2, τ=5 min. The specific current of the cathode peak increased 6.06–6.44 times with respect to the non-activated sample. The investigation of the activated samples' electrochemical characteristics by the galvanostatic cycling method showed that impact nickel activation at i=1 A/dm2 and τ=10 min was insufficient. It was found that at a discharge up to E=0 V, the maximum specific capacitance of 0.731 F/cm2 was obtained for samples activated by impact nickel at i=7 A/dm2 and τ=3 min. The increase in specific capacitance compared to the non-activated sample was 4.49 times. At full discharge, the highest electrochemical activity was found for nickel foam samples activated by impact nickel at i=20 A/dm2 and τ=5 min. The specific capacitance was 0.505 mA∙h/cm2, and it increased 9.02 times

Carbonization, Activation and Description of Activated Carbon from Palm Tree Leaves

One of the maximum residences of activated carbon is adsorption capacity, this significance grows every day in a variety of fields. One of its examples is water treatment, processing of potable, all of those residences deliver capacity of activated carbon in smell elimination and flavor in residues of dissolved natural and color. Activated carbon was made from the carbonization of palm tree leave’s stems and activated using calcium chloride, then tested with an increase in reactivity indicated by iodine adsorption test up to 68.6% reactivity increase in commercial sample and 48.7% in palm tree leaves sample. As the methods and precursors of activated carbon are very diverse and result in deferent adsorption properties, the primary test includes: carbonization of palm tree leaves, size reduction and classification of the charcoal produced, applying an iodine test on the non-activated sample, activating another sample with activating agent CaCl2 to comparison between the activated carbon and the non-activated carbon and shows the increasing in the adsorption capacity for elemental iodine in activated carbon.

Enhanced activation of ultrasonic pre-treated softwood biochar for efficient heavy metal removal from water

Physical and chemical modification on biochar is an interesting approach to enhance the properties and make them potential candidates in adsorption of heavy metals from water. Studies have shown that ultrasound treatments as well as alkali activations on biochar has positive impact on adsorption behaviour of the material. Base activation on biochar derived from ultrasound pre-treated woodchips were studied to understand the influence of ultrasound pre-treatment on chemical modification of biochar and the adsorption properties emerged from it. 40 and 170 kHz ultrasound pre-treated softwood woodchips were subjected to laboratory scale pyrolysis and the resulted biochars were treated with NaOH. The physicochemical properties were examined, and the adsorption experiments revealed that ultrasound pre-treatment assisted biochars have better adsorption capacity as compared to untreated biochar samples after activation. 170 kHz pre-treated sample exhibited an equilibrium adsorption capacity of 19.99 mg/g which is almost 22 times higher than that of corresponding non-activated sample. The ultrasound pre-treated samples showed improved competitive adsorption behaviour towards copper ions in comparison with nickel or lead. The overall study suggests that ultrasound pre-treated biochars combined with alkali activation enhances the heavy metal removal efficiency and these engineered biochars can be used as an effective adsorbent in the field of wastewater treatment.

Efficient separation of fluoride and graphite carbon in spent cathode carbon from aluminum electrolysis by mechanical activation assisted alkali fusion treatment

Spent cathode carbon (SCC) is the largest and most inevitable hazardous solid waste continuously discharged from the aluminum electrolysis industry. In this study, mechanical activation was used to assist alkali fusion treatment in dissociating toxic substances and recovering graphite carbon from SCC. The effect of mechanical activation (i.e., milling speed, ball-to-material mass ratio, and milling time) on the alkali fusion treatment was investigated. Its effect on the physicochemical properties of SCC–Na2CO3 mixtures was also analyzed through particle size distribution, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, X–ray diffraction and thermogravimetric analysis–differential scanning calorimetry. Results showed that mechanical activation enhanced the alkali fusion treatment by improving the physical separation of fluoride, the mixing uniformity and reaction contact area of SCC and Na2CO3, and promoting the conversion of Na2CO3 to Na2O. The formation of agglomerates was the main reason that the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased initially then decreased with the increment in mechanical activation conditions. Under optimal mechanical activation conditions, the carbon content of recovered graphite carbon and the fluoride ion leaching rate increased from 89.35% and 76.50% (non-activated sample) to 93.93% and 95.02%, respectively, indicating that mechanical activation assisted alkali fusion treatment effectively enhanced the separation efficiency of fluoride and graphite carbon. In addition, thermodynamic analysis of the alkali fusion treatment and characterization of recovered graphite carbon (under the optimal mechanical activation conditions) were performed. Results demonstrated that the simultaneous conversion of multiple fluorides (i.e., Na3AlF6 and CaF2) and oxidative decomposition of cyanide in SCC can be achieved via mechanical activation assisted alkali fusion treatment. These findings indicate that mechanical activation–assisted alkali fusion treatment is a promising method for the detoxification and utilization of SCC.

Effect of microwave radiation and mechanical activation on the Carbothermic reduction of molybdenum trioxide: Improving the practical efficiency

In this research two different paths were used to cabothermic reduction of MoO3. In the first and second path, as received MoO3 and graphite with stoichiometric ratios were mixed and mechanically activated at 5, 10, 15 and 24 h and heating by microwave oven (first path) and furnace at 700 and 1000 °C in second path. The XRD results of activated samples before heating showed that, MoO2 was produced in the planetary ball mill after 5 h milling and don't change to another phase during milling up to 24 h. the SEM and XRD results in first and second path showed that the final product was molybdenum carbide but in the non-activated samples the final products were molybdenum carbide and unreacted MoO2. The practical efficiency calculations in first and second method showed that heating of samples by microwave radiation and mechanical activation increase the practical efficiency and decrease the sublimation of molybdenum trioxide. The TGA analysis of non-activated MoO3+ C mixture indicated that the reduction goes with three steps but in the 24 h activated sample, it was seen that the reduction goes with one peak. In other words, the first and second peaks in non-activated sample were not detected in the activated sample that increases the practical efficiency due to prevent the sublimation of MoO3

Preservation of Raw Camel Milk by Lactoperoxidase System Using Hydrogen Peroxide Producing Lactic Acid Bacteria

This study was conducted to investigate the effect of lactic acid bacteria (LAB) activated lactoperoxidase system (LPs) on keeping quality of raw camel milk at room temperature. Camel milk samples were collected from Errer valley, Babile district of eastern Ethiopia. The level of hydrogen peroxide (H2O2) for activation of LPs was optimized using different levels of exogenous H2O2. Strains of LAB (Lactococcus lactis 22333, Weissella confusa 22308, W. confusa 22282, W. confusa 22296, S. Infatarius 22279 and S. lutetiensis 22319) with H2O2 producing properties were evaluated, and W. confusa 22282 was selected as the best strain to produce H2O2. Storage stability of the milk samples was evaluated through the acidification curves, titratable acidity (TA), total bacterial count (TBC) and coliform counts (CC) at storage times of 0, 6, 12, 18, 24 and 48 hours. The LP activity and the inhibitory effect of activated LPs were evaluated by growing E. coli in pasteurized and boiled camel milk samples as contaminating agent. Results indicated that the W. confusa 22282 activated LPs generally showed significantly (P < 0.05) slower rates of acidification, lactic acid production and lower TBC and CC during the storage time compared to the non-activated sample. The H2O2 producing LAB and exogenous H2O2 activated LPs in pasteurized camel milk significantly reduced the growth of E. coli population compared to non-activated pasteurized milk. Overall, the result of acid production and microbial analysis indicated that the activation of LPs by H2O2 producing LAB (i.e. W. confusa 22282) maintained the storage stability of raw camel milk. Therefore, it can be concluded that the activation of LPs by biological method using H2O2 producing LAB can substitute the chemical activation method of LPs in camel milk.

Nitrogen, Phosphorus Co-doped Carbon Obtained from Amino Acid Based Resin Xerogel as Efficient Electrode for Supercapacitor

The organic xerogel was synthesized from the polymerization reaction of a kind of amino acid, tyrosine, and pyrrole-2-carbaldehyde using phosphoric acid as the catalyst and phosphorus source. Nitrogen (N) and phosphorus (P) co-doped carbon (NPC) aerogels were obtained via the cabonization of the synthesized organic xerogel and subsequently being activated by KOH. The influences of the activation agent ratio and activation temperature on the structure, morphology, and the final electrochemical property of NPC materials have been investigated. Compared to the nonactivated sample, the obtained activated N/P-co-doped hierarchical porous carbon exhibits superior electrochemical performance. The optimized sample shows a high specific capacitance of 302 F g–1 at 0.5 A g–1 and good rate capability with capacitance remaining of 214 F g–1 at 20 A g–1, as well as excellent cycling stability with 100% retention after 20,000 cycles in 6 M KOH electrolyte. Considering the practical application, when 60 mg of active mat...

Research and development of iridium cerium photocathode for SuperKEKB injector linac

We present the results of our investigation on iridium cerium compound as a photocathode material for the SuperKEKB photoinjector. A large-size iridium cerium compound with excellent machinability was obtained by a two-stage production method combining cold crucible induction melting and spark plasma sintering, and its usability as photocathode material was verified. The quantum efficiency (QE) of the non-activated sample was measured with 266 nm laser pulses to be 2.12 × 10−6. The QE of the cleaned sample was found to be 1.49 × 10−4, exhibiting an improvement by a factor ~ 70. The high resistance to poisoning against oxidization and carbonization of iridium cerium compound leads to useful properties, such as the compound being easily activate by laser cleaning and its reasonably high QE being maintained under non-ultra-high vacuum conditions. These significant advantages of the iridium cerium photocathode allow for the generation of high-charge electron beams with a bunch charge of 4.8 nC, when used with an advanced radio-frequency (rf) gun in the SuperKEKB injector linac. The QE of iridium cerium compound which was mounted in the rf gun was found to stay within the range of (8 ~ 10) × 10−5 for a year and a half without cathode maintenance such as laser cleaning.

Oxidative acid leaching of mechanically activated sphalerite

ABSTRACTThe pressure leaching kinetics of mechanically activated sphalerite was investigated in this work. X-ray diffraction and scanning electron microscopy were used to characterise the influences of crystalline structure and morphology, respectively. A laser particle size analyser and specific surface area tester were used to determine the particle size and specific surface area, respectively. Compared to the non-activated sample, the activated samples demonstrated distinct physicochemical properties with higher reaction efficiencies and increased Zn recovery ratios. The activation energy of sphalerite decreased from 69.96 to 45.91, 45.11, and 44.44 kJ mol−1 as the activation time increased from 0 to 30, 60, and 120 min, respectively. The reaction orders for the H2SO4 solutions of the sphalerite samples activated for 0, 30, 60, and 120 min were 1.832, 1.247, 1.214, and 1.085, respectively, which indicated that the dependency of the sphalerite leaching process on H2SO4 could be reduced by means of mechanical activation.

The role of mechanical activation on atmospheric leaching of a lateritic nickel ore

The effect of mechanical activation on the atmospheric pressure leaching of a lateritic nickel ore was investigated to develop a superior alternative. Under the influence of mechanical activation, certain physico-chemical changes were observed. Accelerated leaching kinetics and less sulfuric acid consumption were found as the most beneficial effects of mechanical activation. 80.6% Ni and 84.5% Co in leach were obtained with the mechanically activated sample after 2h of leaching in 30% H2SO4 at 85°C and 1/2.5 solid/liquid ratio (w/w). When non-activated sample was leached under the same conditions, similar metal extractions could be obtained after 8h of leaching. Finally, a process flow sheet was developed including mechanical activation of the laterite, agitation leaching, iron precipitation step, and nickel-cobalt solvent extraction.

Lightweight and efficient microwave absorbing materials based on walnut shell-derived nano-porous carbon.

Lightweight microwave absorbing materials have drawn tremendous attention. Herein, nano-porous biomass carbon materials have been prepared by carbonization with a subsequent potassium hydroxide activation of walnut shells and the microwave absorption properties have also been investigated. The obtained samples have large specific surface areas with numerous micropores and nanopores. The sample activated at 600 °C with a specific surface area of 736.2 m2 g-1 exhibits the most enhanced microwave absorption performance. It has the maximum reflection loss of -42.4 dB at 8.88 GHz and the effective absorption bandwidth (reflection loss below -10 dB) is 1.76 GHz (from 8.08 GHz to 9.84 GHz), corresponding to a thickness of 2 mm. Additionally, the effective absorption bandwidth can reach 2.24 GHz (from 10.48 GHz to 12.72 GHz) when the absorber thickness is 1.5 mm. Three-dimensional porous architecture, interfacial polarization relaxation loss, and the dipolar relaxation loss make a great contribution to the excellent microwave absorption performance. In contrast, the non-activated sample with lower specific surface area (435.3 m2 g-1) has poor microwave absorption performance due to a poor dielectric loss capacity. This comparison highlights the role of micropores and nanopores in improving the dielectric loss property of porous carbon materials. To sum up, porous biomass carbon has great potential to become lightweight microwave absorbers. Moreover, KOH is an efficient activation agent in the fabrication of carbonaceous materials.

Isothermal thermo-analytical study and decomposition kinetics of non-activated and mechanically activated indium tin oxide (ITO) scrap powders treated by alkaline solution

Isothermal decomposition process of chemically transforming indium tin oxide (ITO) powders into indium (III) hydroxide powders was investigated. Two types of powders were analyzed, i.e., non-activated and mechanically activated. It has been found that in the case of activated sample, shorter induction periods appear, which permits growth of smaller crystals, while in the case of non-activated sample, long induction periods appear, characterized by the growth of larger crystals. DAEM approach has shown that decomposition processes of non-activated and mechanically activated samples can be described by contracting volume model with a linear combination of two different density distribution functions of apparent activation energies (Ea), and with first-order model, with a single symmetrical density distribution function of Ea, respectively. It was established that specific characteristics of particles not only affect the mechanism of decomposition processes, but also have the significant impact on thermodynamic properties.

Isothermal kinetics of mechanochemically and thermally synthesized Ag from Ag2O

The kinetics of isothermal reduction of Ag2O with graphite under argon atmosphere for a non-activated sample and mechanically activated sample was investigated. It is found that Johnson–Mehl–Avrami model appropriately explained the thermal and mechanochemical synthesis of Ag from Ag2O+ghraphite mixture. The process kinetics was investigated using the same approach for milled and unmilled samples. The results show that the Avrami exponent of mechanochemical reduction is higher than that of high temperature thermal reduction. Also, the mechanisms of nuclei growth in thermal and mechanochemical reduction are diffusion controlled and interface controlled, respectively.

Influence of mechano-chemical activation on biooxidation of auriferous sulphides

The influence of mechano-chemical activation on biooxidation of auriferous flotation concentrate by a consortium of Acidithiobacilli species has been studied. The investigation revealed that substantial changes in the structure of the sulphides occurred when the concentrate was mechanically activated. The effects of activation were monitored through changes in the j-factor, mineral phases and also by chemical analysis. As a result of the changes in structure of the sulphide minerals, 96.7% biooxidation of the activated concentrate was achieved within 8days in contrast to 40% in the case of the non-activated sample after 20days. In the subsequent cyanidation process of the biooxidized residues using carbon-in-leach technique about 98% of gold in the mechanically activated concentrate was recovered whereas 74.6% was realised for the non-mechanically activated concentrate.

Effect of mechanical activation on thiosulfate leaching of gold from complex sulfide concentrate

The use of mechanical activation to enhance gold recovery from a CuPbZn complex sulfide concentrate was investigated. The effects of milling time, ball size, sample to ball ratio and milling speed on thiosulfate leaching were studied. Under optimum conditions of milling time 1 h, ball size 20 mm, sample to ball ratio 1/15 and mill speed 600 r/min, nearly 78% of sample is amorphized, particle size decreases from d 100=30 μm to d 100=8 μm, specific surface area increases from 1.3 m 2/g to 4.6 m 2/g and gold recovery enhances from 17.4 % in non-activated sample to 73.26 %.

Analysis of Mechanically Induced Reactivity of Boehmite Using Kinetics of Boehmite to γ-Al2O3 Transformation

This article focuses on the mechanically induced reactivity of boehmite prepared by thermal decomposition of gibbsite. Boehmite, which retained the morphology of gibbsite, was characterized by a specific surface area of 264 m2/g. Mechanical activation (MA) was carried out in a planetary mill up to 240 minutes. The samples were characterized in terms of morphology, characteristic particle diameters, Brunauer Emmett Teller (BET) specific surface area (SSABET), microcrystallite dimension (MCD), microstrain (e) and Fourier transform infrared spectroscopy. The reactivity was construed from the kinetics of thermal transformation of boehmite into γ-Al2O3. The transformation observed between 600 K and 900 K (327 °C and 627 °C), manifested itself as two overlapping peaks in the differential thermogravimetric plot. These peaks correspond to two stages of dehydroxylation involving Al2OH and AlOH groups in succession. The peaks were resolved using Gaussian deconvolution. The reactivity was assessed separately for the two stages by comparing the fraction reacted in MA samples (α) with that of nonactivated sample (α ref). During both stages, enhanced kinetics, as revealed by α-α ref plots, indicated an increase in reactivity with MA. The transformation mechanism conformed to n th order reaction (f[α] = [1 – α] n with n = 1.3–1.5 in both stages). Values of n remained similar for the activated and reference samples. Activation energies (E a) for the first and second dehydroxylation stages were respectively 115 and 300 kJ/mol for the nonactivated sample. E a for the second stage decreased exponentially to a value of 222 kJ/mol after 240 minutes of milling. An anomalous negative correlation between reactivity and SSABET was observed. Reactivity parameters were strongly correlated with MCD and e. A plausible explanation for the observed correlations is presented.