HNO3 Concentration Research Articles

Hydrofluorocarbon Diluent for CMPO Without Third Phase Formation: Extraction of Uranium(VI) and Lanthanide(III) Ions

ABSTRACT The extraction behaviors of trivalent lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) and hexavalent uranium with octylphenyl(,-diisobutylcarbamoylmethyl)phosphine oxide (CMPO) from a nitric acid medium were studied using hydrofluorocarbon (1,1,1,2,2,3,4,5,5,5- decafluoropentane: HFC-43) as a nonflammable diluent. It was revealed that HFC-43 exhibits high solubility of CMPO even in the absence of tributylphosphate (TBP), which has typically been necessary to prevent third-phase formation in the conventional TRUEX process using -dodecane as a diluent. Distribution ratios have been studied as a function of aqueous HNO concentrations, CMPO concentrations, and ionic radii of lanthanide(III) ions. The stoichiometry of the extracted coordination complex was examined based on the slope analysis, and it was determined that two to three CMPO molecules are coordinated to one lanthanide or uranium ion. The feasibility of the process is indicated by the distribution ratio, which is comparable to the conventional system using -dodecane as diluent. In addition, the safety benefits of applying the nonflammable solvent HFC to the TRUEX process are also presented.

Radiation-thermal stability of hydrazine nitrate in nitric acid solutions

The effect of temperature, HNO3 concentration and radiation dose rate on the decomposition of hydrazine nitrate in aqueous nitric acid solutions has been studied. Kinetic characteristics have been obtained for evaluating the yields of the main decomposition products of hydrazine nitrate - hydrazoic acid and ammonium nitrate. The results of the study are important for analyzing the explosion safety of technological processes with nitric acid solutions containing hydrazine nitrate.

Selective Extraction and Complexation Studies for Thorium(IV) with Bis-triamide Extractants: Synthesis, Solvent Extraction, EXAFS, and DFT.

Three octyl-extended bis-triamide extractants (L1-L3) were designed and synthesized for the selective solvent extraction of Th(IV) over U(VI) in a kerosene-HNO3 system. L1 and L2 exhibited good extraction property and selectivity toward Th(IV) over U(VI) and reached extraction equilibrium within 10 min. In a wide range of a HNO3 concentration from 0.1 to 3.0 M, the separation factor of Th(IV) over U(VI) (SFTh/U) of L1 and L2 ranged from 12.1 ± 1.6 to 123.0 ± 20.2 and 15.2 ± 2.4 to 88.1 ± 14.9, respectively. Slope analysis indicated that Th(IV) was extracted as different species under different HNO3 concentrations, in which the slopes were 2.08 ± 0.20, 1.61 ± 0.03, and 1.54 ± 0.03 for L1 and 2.37 ± 0.22, 2.07 ± 0.17, and 1.76 ± 0.18 for L2 under 0.1, 1.0, and 3.0 M HNO3, respectively. A continuous variation method (Job plot) illustrated a 1.5:1 ligand/thorium (L/Th) ratio in a methanol phase, indicating that L1/L2 and Th(IV) could form mixed 1:1 and 2:1 L/Th extracted complexes. Extended X-ray absorption fine structure (EXAFS) and density functional theory (DFT) calculations revealed that the extracted complexes of L1 and L2 with Th during the extraction process at 0.1 M HNO3 were [2L1·Th·3(NO3)]+ and [2L2·Th·3(NO3)]+.

Highly efficient uptake of tetravalent actinide ions from nitric acid feeds using an extraction chromatography material containing tetra-n-butyl diglycolamide and a room temperature ionic liquid

An extraction chromatography (XC) material containing N,N,N’,N’-tetra-n-butyl diglycolamide (TBDGA) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide (C4mim∙NTf2), a room temperature ionic liquid, was used for the uptake of the tetravalent actinide ions Th(IV), Np(IV), and Pu(IV) from nitric acid feed solutions. The uptake of the metal ions followed the trend: Th(IV) < Np(IV) < Pu(IV), which is the same as that of their ionic potential values. While a decrease in the Np(IV) and Pu(IV) uptake was seen with increasing HNO3 concentration at lower acidities, an opposite trend was observed at higher acidities. Th(IV) uptake was not affected with the acid concentration. In view of the very high uptake and its importance in the nuclear fuel cycle, the major part of the studies was carried out with Pu(IV) ion. The loaded Pu(IV) was back extracted from the XC material using a mixture of 0.5 M oxalic acid and 0.5 M nitric acid. The Pu(IV) uptake by the XC material was fitted into different kinetic and isotherm models. The results conformed to the pseudo-second order kinetic model and the Langmuir monolayer sorption model. Column studies were carried out using a feed having 1.6 mg/L Pu solution in 3 M HNO3. While the breakthrough was obtained after passing ca. nine bed volumes, a sharp elution peak was obtained with >99% recovery in about seven bed volumes.

Fine Aerosol Acidity and Water during Summer in the Eastern North Atlantic

Aerosol pH governs many important atmospheric processes that occur in the marine boundary layer, including regulating halogen and sulfur chemistries, and nutrient fertilization of surface ocean waters. In this study, we investigated the acidity of PM1 over the eastern North Atlantic during the Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) aircraft campaign. The ISORROPIA-II thermodynamic model was used to predict PM1 pH and water. We first investigated the sensitivities of PM1 pH and water predictions to gas-phase NH3 and HNO3 concentrations. Our sensitivity analysis indicated that even though NH3 and HNO3 were present at very low concentrations in the eastern North Atlantic during the campaign, PM1 pH calculations can still be sensitive to NH3 concentrations. Specifically, NH3 was needed to constrain the pH of populations of PM1 that had low mass concentrations of NH4+ and non-volatile cations (NVCs). We next assumed that gas-phase NH3 and HNO3 concentrations during the campaign were 0.15 and 0.09 µg m−3, respectively, based on previous measurements conducted in the eastern North Atlantic. Using the assumption that PM1 were internally mixed (i.e., bulk PM1), we determined that PM1 pH ranged from 0.3–8.6, with a mean pH of 5.0 ± 2.3. The pH depended on both Hair+ and Wi. Hair+ was controlled primarily by the NVCs/SO42− molar ratio, while Wi was controlled by the SO42− mass concentration and RH. Changes in pH with altitude were driven primarily by changes in SO42−. Since aerosols in marine atmospheres are rarely internally mixed, the scenario where non-sea salt species and sea-salt species were present in two separate aerosol modes in the PM1 (i.e., completely externally mixed) was also considered. Smaller pH values were predicted for the aerosol mode comprised only of non-sea salt species compared to the bulk PM1 (difference of around 1 unit on average). This was due to the exclusion of sea-salt species (especially hygroscopic alkaline NVCs) in this aerosol mode, which led to increases in Hair+ values and decreases in Wi values. This result demonstrated that assumptions of aerosol mixing states can impact aerosol pH predictions substantially, which will have important implications for evaluating the nature and magnitude of pH-dependent atmospheric processes that occur in the marine boundary layer.

Regeneration of argan nutshell and almond shell using HNO3 for their reusability to remove cationic dye from aqueous solution

This study reported the desorption of adsorbed crystal violet (CV) dye on the argan nutshell (ANS) and almond shell (AS) using nitric acid (HNO3) as a desorbing agent and their reusability to remove the CV in multiple consecutive adsorption-desorption cycles. The prepared adsorbents were characterized using FTIR and SEM analysis. Different desorbing agents (HCl, HNO3, H3PO4, CH3COOH, NaOH, H2O, H2O (pH = 2), and H2O (pH = 11)) were tested to determine the best eluent. The effect of experimental parameters, such as CV-adsorbent dose (4–40 g L−1), contact time (0–180 min), and HNO3 concentration (0.01–2 M) on the desorption of the CV from CV-ANS and CV-AS was studied. The HNO3 (0.1 M) solution was an excellent eluent for the CV desorption from CV-ANS (98.21%) and CV-AS (98.60%) using 16 g L−1 of CV-adsorbent dose at 23 ± 1 °C for 60 min. The pseudo-second-order kinetic model well-exemplified experimental data. Excellent regeneration reusability of ANS and AS for the CV removal for six consecutive adsorption–desorption cycles. This study showed that argan nutshell and almond shell as low-cost adsorbents have tremendous potential for removing the CV in multiple consecutive adsorption-desorption cycles as an alternative eco-friendly process.

Dissolution of Th0.25U0.75O2 sintered pellets: Impact of nitrate ions and nitrous acid

In order to gain insights on the kinetics of the dissolution of Gen(IV) MOX fuels, sintered pellets of Th0.25U0.75O2 were prepared as surrogates. Particularly, the impact of nitrogen species on the kinetics of dissolution of Th1-xUxO2 in nitric acid must be evaluated. In this work, various experiments were performed to determine the influence of nitrate ions and nitrous acid on the dissolution rate and mechanism of Th0.25U0.75O2 in nitric acid. It appeared that the addition of 3 mol L−1 NH4NO3 to the 1 mol L−1 HNO3 solution led to a strong increase of the dissolution rate. Thus, it seemed that the greatest impact on the dissolution kinetics during the induction period was associated to undissociated HNO3 instead of free nitrate ions. What is more, addition of a constant HNO2 concentration of 2 × 10−3 mol L−1 to 1 mol L−1 HNO3 induced a strong increase of the dissolution rate. However, the dissolution kinetics remained much faster in 4 mol L−1 HNO3, which was associated to the presence of an equivalent concentration of HNO2 in the solution. It then appeared that HNO2 species was not the prevailing species responsible for the catalysis of the dissolution kinetics of Th0.25U0.75O2. However, microstructural evolutions of the pellets dissolved in the presence of HNO2 showed the existence of small intra-granular corrosion pits covering the entire surface of the grains. That confirmed the highly oxidizing nature of HNO2 regarding to tetravalent uranium. Nevertheless, the presence of large cavities also suggested the existence of heterogeneous progress of the dissolution, associated to the existence of preferential dissolution zones consequently to the accumulation of reactive species in confined areas. Such reactive species might be HNO2, but more probably another unknown catalyst present at equilibrium with HNO2.

A HNO3 -Responsive Aqueous Biphasic System for Metal Separation: Application towards CeIV Recovery.

An acidic aqueous biphasic system (AcABS) presenting a desired and reversible phase transition with HNO3 concentration and temperature was developed herein as an integrated platform for metal separation. The simple, economical, and fully incinerable (C,H,O,N) AcABS composed of tetrabutylammonium nitrate ([N4444 ][NO3 ])+HNO3 +H2 O was characterized and presented an excellent selectivity towards CeIV against other rare earth elements and transition metals from both synthetic solutions and nickel metal hydride (NiMH) battery leachates. The acid-driven self-assembly of AcABS bridges the gap between traditional ABS and liquid-liquid extraction whilst retaining their advantageous qualities, including compatibility with highly acidic solutions, water as the primary system component, the avoidance of organic diluents, rapid mass transfer, and the potential integration of the leaching and separation steps.

Formation and Prevention of Secondary Nitrate in PM2.5 in Tianjin

To study the formation and approaches to controlling secondary nitrate in PM2.5, the ionic compositions of PM2.5, pH of aerosols, variations in NH3-NH4+ and HNO3-NO3- concentrations, and the joint NH3/HNO3 sensitivity regime map of ammonium nitrate were investigated based on high-resolution online monitoring data for an urban site in central Tianjin from 2018 to 2019. The results showed that the average concentration of PM2.5 was 58μg·m-3, and the main ionic compositions of PM2.5 were nitrate (NO3-), ammonium (NH4+), sulfate (SO42-), Cl-, and K+ with corresponding mass percentages of 18.4%, 11.6%, 10.3%, 3.3%, and 2.6%, respectively. Concentrations of PM2.5 and the main components were relatively high during the heating season and relatively low during the non-heating season. The aerosols were weakly acidity with an average pH of 5.21; pH was higher in spring and winter and lower in summer and autumn, and diurnal variations pH were lower in the morning (00:00-08:00) and slightly higher at other times. The concentrations of NH3(g) (gas NH3) and HNO3(g) (gas HNO3) were 16.7μg·m-3and 1.2μg·m-3, respectively. The concentrations of NH3(g) were relatively higher from April to September and lower from October to February of the following year. HNO3(g) concentrations did not show any clear monthly pattern. Except during the summer, NH3(g) concentrations were higher in the morning and evening, and HNO3(g) concentrations were higher during the day. No clear linear relationships were observed between the concentrations of NH3(g) and NH4+ nor the concentrations of HNO3(g) and NO3- at different pH levels. Higher concentrations of NO3- and NH4+ were observed in the morning and evening, while no linear relationships were observed between the pH and concentrations of NH3(g)-NH4+ and HNO3(g)-NO3-. The joint NH3/HNO3 sensitivity regime map showed that most of the points were located in the HNO3 sensitive region with some in the NH3 & HNO3 sensitive region. In spring, autumn, and winter, most of the points were located in the HNO3 sensitive region while in summer, a significant quantity of the points were located in the NH3 & HNO3 sensitive region. Therefore, the precursors of HNO3 (such as NOx) should be controlled in the spring, autumn, and winter, and attention should be given to the control of the precursors of HNO3 (NOx) and NH3 in the summer to effectively control nitrate and ammonium aerosols in PM2.5 in Tianjin.

Enhanced removal efficiency of toluene over activated carbon under visible light

Toluene removal rates using activated carbon (AC) at various relative humidity (RH) levels (0%, 30%, 60%) were compared under dark and visible-light conditions. Light exposure significantly increased toluene-removal efficiency independent of RH. When AC was pre-treated with an optimal concentration of HNO3, its toluene-removal efficiency was enhanced further with light, an effect that can be attributed to increased surface-area and porosity. Fourier-transform infrared analysis confirmed that exposure of HNO3-modified AC to light induced partial oxidation of toluene. Within visible-light range (380–650 nm), shorter wavelengths were more effective for toluene-removal compared with longer wavelengths. This suggests that hydroxyl groups formed on AC-surface under light strongly interact with aromatic rings of toluene, allowing for greater uptake of toluene. Moreover, AC can sustain its photo-activity when mixed with cement and cured, suggesting its potential applications in air-purifying building materials. An efficient and practical method for regeneration of spent AC is also demonstrated.

Novel two-step process for remediation of Cs-contaminated soil assisted by magnetic composites

In this study, a new approach to remediate Cs+-contaminated soil using magnetic composites to improve both the efficiency of separation of clay particles and Cs+ desorption is proposed. An ultrasonic dispersion and magnetic separation process were first performed to selectively remove clay particles from soil. In the soil dispersion solution, polyethylenimine-grafted Fe3O4 nanoparticles were selectively bonded with clay particles through electrostatic attraction, enabling the clay particles to be easily separated from the solution under an external magnetic field. In a Cs+ desorption process, Cs+ removal increased with increasing HNO3 concentration and temperature; the addition of K+ to the acid solution further enhanced Cs+ desorption by replacing Cs+ on the accessible sites of the sand. The addition of a magnetic adsorbent (Fe3O4@SiO2@KTiFC, where KTiFC is potassium titanium(IV) hexacyanoferrate) to the acid treatment substantially improved Cs+ desorption (95.2%) by preventing re-adsorption of Cs+ onto the sand. Based on these results, we evaluated the applicability of the proposed process to the decontamination of radioactive soil. The clay separation process substantially reduced the radioactivity level of the soil from 1630 to 222 Bq/kg by concentrating most of the 137Cs into the magnetic fraction. After treatment of the residual sand using the optimized Cs+ desorption method, the final radioactivity of the treated soil (73.5 wt% of initial soil) was 53 Bq/kg, which is less than the clearance level (100 Bq/kg). Therefore, the proposed method is potentially an effective and practical approach for the decontamination of radioactive soil.

Extraction Behaviors of Critical Rare Earth Elements with Novel Structurally Tailored Unsymmetrical Diglycolamides from Acidic Media

ABSTRACT A series of eight new structurally related unsymmetrical diglycolamides (UDGA) were designed and compared based on REEs extraction and phase compatibility at high acidic media concentration. The structure–reactivity relationship with extraction of REEs was studied in HCl, HNO3, and H2SO4 solutions. A symmetrical diglycolamide (DGA), N,N,N’,N’-tetradodecyldiglycolamide (TD2DGA), was synthesized for purpose of comparison. The influence of HCl, HNO3, and H2SO4 concentrations on the distribution ratios of the studied metal ions was investigated. In all systems, the mutual separation of the investigated REEs as well as from Fe(III), Ni(II), and Co(II) was achieved in the whole range of acidic solutions used by N,N′‐diisobutyl‐N,N′‐didodecyldiglycolamide (DiBD2DGA). A systematic investigation of the extraction of La(III), Pr(III), Nd(III), and Dy(III) was carried out with DiBD2DGA from hydrochloric acid media. The stoichiometry of the extracted REEs-UDGA complex was determined by the slope analysis method and complexation was found to be exothermic. The FT-IR spectra of these extracted species were studied. The back extraction of La(III), Pr(III), Nd(III), and Dy(III) was carried out.

Low temperature pickling regeneration process for remarkable enhancement in Cu(II) adsorptivity over spent activated carbon fiber

In this paper, a simple and efficient regeneration technology of low-temperature pickling regeneration process is proposed for Cu(II)-adsorbed activated carbon fiber felts (ACFFs). The regeneration process mainly uses the strong oxidation of acidic regenerant above boiling point to regenerate ACFFs in a confined space. With no demand for high temperature and high pressure, the regeneration process achieves a high efficiency regeneration and a remarkable enhancement of Cu(II) adsorptivity simultaneously for Cu(II)-adsorbed ACFFs. After parameter optimization, the pickling temperature of 383 K, pickling time of 3 h and HNO3 concentration of 150 g/L are adopted as optimum process parameters for the reutilization of ACFFs. The regeneration rates of ACFFs in five cycles are maintained at 424.08%–829.59%. Analytical results show that the enhancement of Cu(II) adsorptivity is mainly caused by the remarkable enhancement of specific surface area (increased by 106.08%), micropore volume (increased by 102.17%) and more abundant surface chemical structure (particularly carboxyl and nitro group) after treated by the regeneration process.

The Effect of Doping on the Digital Etching of Silicon-Selective Silicon-Germanium Using Nitric Acids.

Gate-all-around (GAA) field-effect transistors have been proposed as one of the most important developments for CMOS logic devices at the 3 nm technology node and beyond. Isotropic etching of silicon–germanium (SiGe) for the definition of nano-scale channels in vertical GAA CMOS and tunneling FETs has attracted more and more attention. In this work, the effect of doping on the digital etching of Si-selective SiGe with alternative nitric acids (HNO3) and buffered oxide etching (BOE) was investigated in detail. It was found that the HNO3 digital etching of SiGe was selective to n+-Si, p+-Si, and intrinsic Si. Extensive studies were performed. It turned out that the selectivity of SiGe/Si was dependent on the doped types of silicon and the HNO3 concentration. As a result, at 31.5% HNO3 concentration, the relative etched amount per cycle (REPC) and the etching selectivity of Si0.72Ge0.28 for n+-Si was identical to that for p+-Si. This is particularly important for applications of vertical GAA CMOS and tunneling FETs, which have to expose both the n+ and p+ sources/drains at the same time. In addition, the values of the REPC and selectivity were obtained. A controllable etching rate and atomically smooth surface could be achieved, which enhanced carrier mobility.

Nitric acid dry deposition associated with equilibrium shift of ammonium nitrate above a forest by long-term measurement using relaxed eddy accumulation

The dry deposition process of nitrogen compounds still has considerable uncertainty due to the complex compound behavior in the atmosphere. To enhance understanding of the nitric acid (HNO3) dry deposition process that largely contributes to the total nitrogen deposition, we associate this process with the equilibrium shift of ammonium nitrate (NH4NO3) to HNO3 and ammonia (NH3) near the surface. We obtained the flux of HNO3 and PM2.5 components above a forest in suburban Tokyo using a relaxed eddy accumulation (REA) system incorporating the denuder/filter-pack sampling technique. We conducted continuous samplings on a weekly basis over a long-term period, from October 14, 2016 to October 3, 2018, including leafy and leafless conditions. The measured deposition velocities of fine NO3− particles were significantly (p < 0.05) larger than those of fine SO42− particles and similar to those of HNO3, regardless of the leafy and leafless periods. The larger deposition velocities of fine NO3− particles caused by the equilibrium shift of NH4NO3 were found to be similar to previous measurements at the same site. The measured deposition velocities of HNO3 were low and included many emission cases compared to those of fine NO3− particles. The lower HNO3 deposition velocities were associated with the equilibrium shift of NH4NO3 to the gas phase, causing the suppressed deposition and apparent emission of HNO3, particularly during the leafless period. The emission of HNO3 is possibly due to high HNO3 concentration near the surface, which is attributed to a small removal of the leafless canopy. The turbulence enhanced both the upward and downward fluxes of HNO3. These results will contribute to the better understanding for the dynamics of the nitrogen compounds in the atmosphere and the accurate assessment for the nitrogen deposition.

Solvent-Impregnated Resins Based on the Mixture of (2-Diphenylphosphoryl)-4-ethylphenoxy)methyl) diphenylphosphine Oxide and Ionic Liquid for Nd(III) Recovery from Nitric Acid Media.

Novel solvent-impregnated resins (SIRs) were prepared by treatment of styrene–divinylbenzene copolymer (LPS-500) with mixtures of the promising polydentante extractant (2-diphenylphosphoryl)-4-ethylphenoxy)methyl)diphenylphosphine oxide (L) and an ionic liquid [C4mim]+[Tf2N]−for the extraction chromatography recovery of Nd(III) from nitric acid solutions. It was shown that introduction of the ionic liquid into the SIR composition results in considerable enhancement of the Nd(III) recovery efficiency compared with resin impregnated only by L in slightly acidic media. The influence of the L: ionic liquid molar ratio in the SIRs composition, their percentages, concentration of metal and HNO3 in the eluent, and acid type on the value of synergistic effect and adsorption efficiency of Nd(III) recovery was studied. The SIR containing 40% of mixture of L and [C4mim]+[Tf2N]− with molar ratio 2:1 turned out to be the most efficient. The selectivity of Nd(III) separation from light and heavy rare-earth elements was studied and the optimal conditions of Nd(III) adsorption recovery and stripping by this SIR were chosen. It was found that in recovery efficiency of Nd(III) developed SIR exceeded the SIR containing Cyanex 923 (a mixture of monodentate trialkylphosphine oxides) and [C4mim]+[Tf2N]−.

Determination of iron, nickel, and vanadium in crude oil by inductively coupled plasma optical emission spectrometry following microwave-assisted wet digestion

The complexity of crude oil samples is the primary difficulty in reliable quantitation of their metal contents. However, substantial advances in sample digestion procedures have been presented as a result of the utilization of microwave radiation. Herein, a new method based on microwave-assisted digestion (MW-AD) for the decomposition of crude oil samples has been developed for efficient determination of iron, nickel, and vanadium by inductively coupled plasma optical emission spectrometry (ICP OES). Yttrium was used as an internal standard to achieve as accurately as possible quantitation. The digestion efficiency was optimized using various HNO3 concentrations (14.5, 9.1, 6.5, and 4 mol L−1) and different volumes of H2O2 by determining the residual carbon content (RCC) and residual acidity (RA) of the final digests. The obtained results revealed that 9.1 mol L−1 HNO3, 2 mL H2O2, and sample mass of 300 mg were the appropriate compromise conditions for efficient digestion and suitable final digests since RCC values and RA were below 10% and 35%, respectively. The MW-AD method was successfully validated by the analysis of samples spiked with the target metals at different concentration levels. The results demonstrated a satisfactory recovery in the range of 95–104.2% with intra-day and inter-day relative standard deviation of less than 10%. The method was also applied to the determination of the analyte metals in crude oil samples, and the results were compared with those obtained by the application of the ASTM D5708 method as a reference method.

Processing Technogenic Raw Materials-Phosphorus Slags with the Production of Precipitated Nanosilica and Simultaneous Recovery of Valuable Components

The paper provides a flow sheet of the phosphorus slag processing to produce precipitated silica (white soot). The process conditions for opening phosphorus slag at the I stage of leaching have been selected: the nitric acid concentration is 3.5 mol/dm3; the ratio S:L = 1:3.5; the temperature is 60 oС; and the process duration is 1 hour. The parameters of the white soot production II stage have been determined: the HNO3 concentration is 6.5 mol/dm3; the ratio S:L = 1:3.5; the temperature is 50 oС; and the process duration is 1 hour. The temperature effect on the white soot structure and the specific surface have been established. At optimal process parameters, the white soot batches have been obtained with the main SiO2 component content of 88.2 and 90.5 %, and a specific surface of 170 and 182 m2/g, respectively. The through recovery of silicon into a commercial product is 98.0 % of its initial content in slag.

Utilization of Mendong Plants-Activated Charcoal as H2S and NO2 Gas Adsorbent: Preliminary Study

The study of exhaust H2S and NO2 gases using activated carbon has been conducted. In this study, activated carbon was prepared from mendong plant (Frimbistylis umbellaris), which was activated using zinc chloride (ZnCl2) with concentrations of 2.5; 5; 7.5; and 10 % w/v to determine the efficiency of H2S adsorption. Mendong charcoal was obtained from the process of using a modified tool. Activation was done by maceration using ZnCl2 activator (w/v) for 24 hours. The adsorption of H2S and NO2 was analyzed using UV-Vis spectrophotometry. Determinations of H2S gas carried out using the blue methylene’s method for 1 hour showed the highest effectiveness of mendong activated carbon was of that at the concentration of 2.5 % ZnCl2 w/v with 80% of H2S removal. Further, the mendong activated carbon with the concentration of 2.5% ZnCl2 w/v was used for NO2 adsorption. The adsorption of NO2 gas was conducted for 1 hour using Griess Saltzman’s method. The result showed that the largest concentration of NO2 gas was adsorbed when the HNO3 concentration was 1.5 M (0.057 µg/mL). The percentage of NO2 efficiency adsorbed was at 28%.

Highly Sensitive Porous PDMS-Based Capacitive Pressure Sensors Fabricated on Fabric Platform for Wearable Applications.

A novel porous polydimethylsiloxane (PDMS)-based capacitive pressure sensor was fabricated by optimizing the dielectric layer porosity for wide-range pressure sensing applications in the sports field. The pressure sensor consists of a porous PDMS dielectric layer and two fabric-based conductive electrodes. The porous PDMS dielectric layer was fabricated by introducing nitric acid (HNO3) into a mixture of PDMS and sodium hydrogen bicarbonate (NaHCO3) to facilitate the liberation of carbon dioxide (CO2) gas, which induces the creation of porous microstructures within the PDMS dielectric layer. Nine different pressure sensors (PS1, PS2,..., PS9) were fabricated in which the porosity (pore size, thickness) and dielectric constant of the PDMS dielectric layers were varied by changing the curing temperature, the mixing proportions of the HNO3/PDMS concentration, and the PDMS mixing ratio. The response of the fabricated pressure sensors was investigated for the applied pressures ranging from 0 to 1000 kPa. A relative capacitance change of ∼100, ∼323, and ∼485% was obtained by increasing the curing temperature from 110 to 140 to 170 °C, respectively. Similarly, a relative capacitance change of ∼170, ∼282, and ∼323% was obtained by increasing the HNO3/PDMS concentration from 10 to 15 to 20%, respectively. In addition, a relative capacitance change of ∼94, ∼323, and ∼460% was obtained by increasing the PDMS elastomer base/curing agent ratio from 5:1 to 10:1 to 15:1, respectively. PS9 exhibited the highest sensitivity over a wide pressure sensing range (low-pressure ranges (<50 Pa), 0.3 kPa-1; high-pressure ranges (0.2-1 MPa), 3.2 MPa-1). From the results, it was observed that the pressure sensors with dielectric layers prepared at relatively higher curing temperatures, higher HNO3 concentrations, and higher PDMS ratios resulted in increased porosity and provided the highest sensitivity. As an application demonstrator, a wearable fit cap was developed using an array of 16 pressure sensors for measuring and mapping the applied pressures on a player's head while wearing a helmet. The pressure mapping aids in observing and understanding the proper fit of the helmet in sports applications.