Dilute Acid Medium Research Articles

Dissolution of nanoparticulate IrO2 in dilute acidic baths through a pre-reduction step: A method to recover Ir from electrocatalytic/catalytic bodies

We report a process for recycling Ir-based nanosized electrocatalysts through dissolution of Ir under mild conditions (in dilute acidic media at ∼100 °C) and show that otherwise corrosion-resistant Ir-Oxide nanoparticles may be activated for dissolution in dilute HCl using a pre-reduction step. Effects of the reaction parameters such as the type of reducing agent, dissolution bath composition, reaction temperature, etc. was investigated. Further, structural characterizations to investigate the effect of the prereduction step on the Ir-Oxide and on the dissolved Ir species were made. The dissolved Ir was processed further to synthesize a new Ir-Oxide electrocatalyst exhibiting electrochemical performance (mass activity for oxygen evolution reaction) similar to that of the commercial Ir-Oxide. The study provides a recycling solution for the Ir-based electrocatalysts from relevant catalytic bodies and may be used for achieving sustainable acidic electrolyzers.

Determination of Lutecium in Radio-pharmaceutical Samples using High Resolution ICP-AES Technique

An analytical method was developed for the determination of Lutetium in dilute nitric acid medium using high resolution ICP-AES analytical technique. These studies were required for the determination of Lutetium contents in radiopharmaceutical samples. For the patients suffering from cancers, 177Lu DOTA-TATE peptide receptor radionuclide therapy is used. This necessitates the use of 177Lu and obviously the quantification of Lutetium for its efficient application during medical therapy which is used for the preparation of the patients suffering from cancers. Due to short half life of 177Lu of 6.67 days, it is most likely to get added up with Hf, as it is build up on storage, the undesired impurity element. Hence the effect of Hf on the determination of Lu was studied. Subsequently seven actual samples of 177Lu were analysed for Lu contents after taking into account Hf contribution if any.

Determination of Lutetium In Radiopharmaceutical Samples Using High Resolution ICP-AES Technique

An analytical method was developed for the determination of Lutetium in dilute nitric acid medium using high resolution ICP-AES analytical technique. These studies were required for the determination of Lutetium contents in radiopharmaceutical samples. For the patients suffering from cancers, 177Lu DOTA-TATE peptide receptor radionuclide therapy is used. This necessitates the use of 177Lu and obviously the quantification of Lutetium for its efficient application during medical therapy which is used for the preparation of the patients suffering from cancers. Due to short half life of 177Lu of 6.67 days, it is most likely to get added up with Hf, as it is build up on storage, the undesired impurity element. Hence the effect of Hf on the determination of Lu was studied. Subsequently seven actual samples of 177Lu were analysed for Lu contents after taking into account Hf contribution if any.

Determination of Lutetium In Radiopharmaceutical Samples Using High Resolution ICP-AES Technique

An analytical method was developed for the determination of Lutetium in dilute nitric acid medium using high resolution ICP-AES analytical technique. These studies were required for the determination of Lutetium contents in radiopharmaceutical samples. For the patients suffering from cancers, 177Lu DOTA-TATE peptide receptor radionuclide therapy is used. This necessitates the use of 177Lu and obviously the quantification of Lutetium for its efficient application during medical therapy which is used for the preparation of the patients suffering from cancers. Due to short half life of 177Lu of 6.67 days, it is most likely to get added up with Hf, as it is build up on storage, the undesired impurity element. Hence the effect of Hf on the determination of Lu was studied. Subsequently seven actual samples of 177Lu were analysed for Lu contents after taking into account Hf contribution if any

Data and statistical evaluation of the protection effect of essential oil extracts on plain carbon steel in dilute acid media

Optimal performance of corrosion inhibiting compounds significantly depends on specific range of inhibitor concentration and measurement time. Data on the protection effect of laurus cassia and rosmarinus angustifolius essential oil extracts on plain carbon steel in 0.5 M H2SO4 and HCl electrolyte was researched into by weight loss analysis. The data showed the admixed extracts were highly potent at the concentrations studied with protection effect typically above 95%. The protection effect increased progressively with measurement time at 1% to 2% extracts concentration beyond which (2.5% to 3% concentration) the results were generally constant. The extracts exhibited inhibition performance independent of concentration. Data on standard deviation showed the degree of deviation of protection effect with measurement time and concentration is minimal. The fraction of protection effect data above 90% protection in H2SO4 is 98% and 100% in HCl solution at limit of errors of 3.24% and 0%. Statistical data by analysis of variance shows both inhibitor concentration and measurement time remarkedly altered the protection effect of the extracts with statistical relevance values of 47.17% and 53.02 for concentration and 26.51% and 29.52% in H2SO4 and HCl solution.

Corrosion Inhibition and Adsorption Mechanism of PVP for Mild Steel in 1.0 M H2SO4: Experimental and Theoretical Approach

Aim:Corrosion of mild steel pipe line when exposed to dilute sulphuric acid is a very serious problem for people in the industry and they are in constant search of highly efficient corrosion inhibitors for acidic medium. For designing new corrosion inhibitors, a through knowledge of corrosion and adsorption mechanism is required.Background:Pitting, cracking and uniform types of corrosion are very common forms of corrosion in dilute sulphuric acid medium. A highly efficient acid corrosion inhibitor is required to minimize all these three forms of corrosion.Objective:The objective was to provide a solution for pitting, cracking, and uniform types of corrosion and to study corrosion and inhibition mechanisms so that highly efficient corrosion inhibitors can be designed.Methods:Polyvinyl pyrrolidone (PVP) was explored as a corrosion inhibitor for mild steel in 1.0 M H2SO4 by experimental and theoretical techniques. Experimental techniques used were impedance, weight loss, metallurgical microscopy, and polarization. Theoretical techniques used were DFT, MD simulation, Frontier molecular orbital, Langmuir, and Frumkin adsorption. Theoretical parameters like interaction energy, adsorption energy, Fukui function, chemical potential, electron density distribution, HOMO/LUMO eigenvalue, etc., help in understanding the mechanism of adsorption of PVP on the Fe (110) surface.Results:Experimental results were supported by theoretical studies. A linear relation was observed between PVP concentration and inhibition efficiency. A maximum of 85.92% inhibition efficiency was observed with a regression coefficient of 0.998. The pore length, the number of pits, and cracks intensity decrease with the concentration of PVP. The waste dilute H2SO4 after the weight loss study was investigated for its biocompatibility and was found to be within the acceptable limit.Conclusion:PVP was proved to be a highly efficient acid corrosion inhibitor for mild steel in 1.0 M H2SO4 medium.

Pertraction of Vanadium(V) from Dilute Acidic Media by an Emulsion Liquid Membrane Containing a Commercial Extractant

AbstractEmulsion liquid membrane (ELM) pertraction of VV ions from dilute acidic solution by using a mixture of di(2‐ethylhexyl)phosphoric acid (D2EHPA) and mono(2‐ethylhexyl)phosphoric acid (M2EHPA) was studied. First, solvent extraction of VV from an aqueous medium was performed, and the optimum feed pH and extractant concentration were obtained. Tributyl phosphate was used as modifier to increase membrane stability and decrease membrane swelling. The effects of diluent type, extractant concentration of the emulsifier concentration, stripping reagent concentration (sulfuric acid), organic phase/stripping phase volume ratio, emulsification time and speed, feed initial pH, agitation speed, temperature, and contact time on VV extraction efficiency and ELM stability were considered.

Spectroscopic Study of the Behavior of Mo(VI) and W(VI) Polyanions in Sulfuric-Phosphoric Acid Mixtures.

The solution chemistry of Mo(VI) and W(VI) in mixtures of sulfuric and phosphoric acids is relevant to the development of practicable hydrometallurgical processes for the recovery and separation of these two elements from low-grade scheelite ores. The behavior of Mo(VI) and W(VI) in such mixtures has been studied using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), nuclear magnetic resonance (NMR), and small-angle X-ray scattering (SAXS) spectroscopies, along with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Where applicable, these techniques have produced a self-consistent picture of the similarities and differences between the chemical speciation of Mo(VI) and W(VI) as functions of solution composition, mostly at a constant phosphorous/metal (P/M; M = Mo(VI) or W(VI)) ratio of ∼1. In dilute acidic media (0.02 mol·kg-1 H+, without H2SO4), Mo(VI) exists mostly (∼60%) as P2Mo5O236- with the remaining ∼40% as β-Mo8O264-. Under the same conditions, W(VI) is largely present as NaPW11O396- (∼80%) and P2W5O236- (∼10%), with the remainder probably occurring as isopolytungstates such as W12O4212- and some tungstophosphate dimers such as P2W18O626-. At higher acid concentrations (≲5 mol·kg-1 H2SO4), polymeric Mo(VI) anions are broken down to form the oxocations MoO22+ and Mo2O52+ and their protonated forms, with the dimers becoming increasingly dominant at higher acidities (∼80% in 5 mol·kg-1 H2SO4). In stark contrast, W(VI) polyanions do not decompose at higher acidities but instead form (∼70% in 0.6 mol·kg-1 H2SO4) a Keggin ion, PW12O403-. Further acidification with H2SO4 results in the agglomeration of this Keggin ion, forming clusters of about 50 and 100 Å in diameter that ultimately produce crystalline precipitates, which could be identified in part by their X-ray diffraction patterns. Possible application of these findings to the hydrometallurgical separation of Mo and W using acidic solutions is briefly discussed, based on a limited number of batch solvent extractions.

Pursuing green and efficient process towards recycling of different metals from spent lithium-ion batteries through Ferro-chemistry

Sustainable recycling of different value-added metals from spent lithium-ion batteries (LIBs) can expect significant environmental and economic benefits for the fulfillment of resources utilization. During the separation and recovery of different metals, excessive chemical consumption caused by prolonged processes may eventually spoil the environmentally soundness recycling of spent LIBs. Here, Ferro-chemistry was innovatively proposed towards the recycling of different metals based on transformation of iron morphology from different types of spent LIBs (LiCoO2 and LiFePO4). It can be concluded from the thermodynamic results that redox reaction will take place in dilute sulfuric acid medium without addition of reductant/oxidant, indicating that Fe(II) in LFP can be used as reductant for the direct leaching of LiCoO2. Leaching results indicate that 99.9% Li, Fe, P and 92.4% Co can be dissolved and existed as Fe3+, Li+, PO43− and Co2+ under the optimized conditions, with a decline of over 80% acid consumption. The leaching kinetics of different metals and reaction mechanism suggest that Fe(II) will be promptly liberated to lixivium and then slowly oxidized into Fe(III) with the existence of Co(III), resulting in a synergetic leaching of Co and Fe. Then, Fe(III) can be precipitated as FePO4 at pH of 2.5, which can remove PO43− with the direct generation of LiFePO4 precursors. This above ferro-chemistry strategy can effectively reduce the consumption of chemicals with reduced environmental footprint.

Corrosion inhibition and statistical data of thiocarbanilide and thiocarbanilide admixed with 4-hydroxy-3-methoxybenzaldehyde on carbon steel in dilute acid media

The inhibition performance of thiocarbanilide (TD) and thiocarbanilide admixed with 4-hydroxy-3-methoxybenzaldehyde (TDHM) on the corrosion of mild steel in 1M H2SO4 and HCl acid solutions was studied through coupon measurement. Data obtained showed the optimal performance of TD is 71.69% in H2SO4 and 83.14% HCl acid solution respectively. TDHM performed more effectively with optimal inhibition efficiency of 96.77% and 97.21% in both acids. The result showed the performance of corrosion inhibiting compounds improves through synergistic interaction with other compounds. However, exposure time and inhibitor concentration strongly influenced the performance of the compounds at varying degrees. Statistical data shows the standard deviation for inhibition efficiency of the compounds was significantly higher in H2SO4 compared to HCl due to the high degree of variation analogous to exposure time and stability of the inhibitor molecules. TD and TDHM generally showed lower standard of deviation, higher mean value, lower margin of error and higher proportion of inhibition efficiency data above 70% inhibition performance. Statistical data from analysis of variance depict both exposure time and inhibitor concentration is statistically relevant, and influences the inhibition performance of TD and TDHM compounds. However, the influence of concentration is significantly limited compared to exposure time with statistical relevance values above 60%

Hydrometallurgical leaching and kinetic modeling of low-grade manganese ore with banana peel in sulfuric acid

Manganese was leached from a low-grade manganese ore (LGMO) using banana peel as the reductant in a dilute sulfuric acid medium. The effects of banana peel amount, H2SO4 concentration, reaction temperature, and time on Mn leaching from the complex LGMO were studied. A leaching efficiency of ∼98% was achieved at a leaching time of 2 h, banana peel amount of 4 g, leaching temperature of 120°C, manganese ore amount of 5 g, and sulfuric acid concentration of 15vol%. The phase, microstructural, and chemical analyses of LGMO samples before and after the leaching process confirmed the successful leaching of manganese. Furthermore, the leaching process followed the shrinking core model and the leaching rate was controlled by a surface chemical reaction (1 − (1 − x)1/3 = kt) mechanism with an apparent activation energy of 40.19 kJ·mol−1.

Cetyl Trimethyl Ammonium Bromide as Anti-Pit Agent for Mild Steel in Sulfuric Acid Medium

Aim: Pitting corrosion is a very serious problem for mild steel when it comes in contact with the dilute sulfuric acid medium. Specialized corrosion inhibitors are essentially required to minimize pitting and uniform types of corrosion in mild steel. Background: Most of the corrosion inhibitors discovered so far protects the mild steel from uniform type of corrosion. But pitting corrosion is more fatal than a uniform type of corrosion because it immediately makes mild steel unfit for use as leakage starts from the pit. Objective: The objective was to protect the mild steel alloys from pitting corrosion when comes in contact with dilute sulfuric acid by the use of organic corrosion inhibitor. Methods: Cetyl Trimethyl Ammonium Bromide (CTAB) is tested as a corrosion inhibitor for mild steel in 0.1 N H2SO4 as corroding medium at 25.0, 30.0 and 35.0°C by weight loss, electrochemical polarization, and Impedance spectroscopy methods. Surface study of corroded and un-corroded specimens of mild steel was carried out by Metallurgical Research Microscopy (MRM) and Scanning Electron Microscopy (SEM) techniques. Results: Surface study confirms that the adsorption of CTAB takes place through nitrogen atom resulting in the formation of uniform, nonporous, passive film confirmed by decrease in Warburg Impedance (Zw), decrease in Faradaic current, increase in Capacitive current, an increase in charge transfer resistance, Rct (41 to 401 Ω cm2) and significant increase in capacitive loop in Nyquist plot with increase in concentration of CTAB which results in significant decrease in corrosion rate of mild steel in 0.1N H2SO4 medium (percentage corrosion inhibition efficiency: 95.0%) especially eradicating pitting type of corrosion. Conclusion: CTAB was proved to be a very good anti-pit agent for mild steel in 0.1N sulfuric acid medium. Pitting and uniform type of corrosion was significantly reduced by the use of CTAB as corrosion inhibitor for mild steel in the dilute sulfuric acid medium at 25.0, 30.0 and 35.0°C.

Corrosion inhibition effect of citrus sinensis essential oil extract on plain carbon steel in dilute acid media

The inhibition performance of essential oil extracts of citrus sinensis (CS) on the corrosion of plain carbon steel (PCS) in 0.5 M H2SO4 and 0.5 M HCl solution was evaluated by weight loss measurement, potentiodynamic polarization technique, optical macroscopy and ATF-FTIR spectroscopy. CS more effectively inhibited PCS corrosion in HCl solution compared to H2SO4 with optimal inhibition result of 81.61% in HCl and 76.95% in H2SO4 from weight loss measurement. The corresponding values from potentiodynamic polarization are 94.90% in HCl and 76.93% in H2SO4 solutions respectively. Inhibition efficiency generally decreased with respect to exposure time, but increased with increase in inhibitor concentration in both acids. The inhibition performance of CS was observed to be mixed type inhibition effect in both acids with dominant cathodic inhibition reaction mechanism at 6%-10% CS concentration in HCl solution. CS influenced the anodic cathodic polarization plots in H2SO4 solution through surface coverage of the steel inhibiting the redox electrochemical process. In HCl significant influence of the anodic-cathodic polarization plots results in pseudo passivation behavior during potential scanning. Inhibition. FTIR spectra peaks showed aggregation of CS molecular functional groups with decreased transmittance over a wide spectrum in corroded H2SO4 solution compared to specific spectra peaks in HCl with decreased transmittance due to limited absorption of protonated CS molecules. Optical images of corroded and non-inhibited PCS specimen from both acids exhibited severe surface degradation with macro pits visible on the steel from H2SO4 solution. The inhibited steel from both acids displayed improved surface morphology due to surface protection effect of CS molecules.

Electrochemical performance of 2-meracaptobenzothiazole on the corrosion inhibition of selected metallic alloys in dilute acid media

The inhibition performance of 2-meracaptobenzothiazole on the corrosion of 316 austenitic stainless steel in 3M HCl, mild steel in 1M HCl and 1060 aluminium alloy in 2M H2SO4 solution alloy was studied by coupon measurement. Results showed the compound performed more effectively on the 316 steel with average corrosion inhibition performance result of 90% followed by the aluminium alloy with average inhibition performance value of 70%. 2-meracaptobenzothiazole performed poorly on mild steel with average inhibition performance results of 55% at low concentration and results below 0% and high inhibitor concentrations. Statistical data through showed that inhibitor concentration only influenced the inhibition performance of 2-meracaptobenzothiazole. Inhibitor concentration and exposure time were statistically relevant to the inhibition performance of 2-mercaptobenzothiazole on mild steel at varying degrees while both inhibitor concentration were statistically irrelevant to the inhibition performance of 2-meracaptobenzothiazole on 1060 aluminium alloy. Adsorption isotherm studies showed SD adsorption on the metallic alloys aligned with Langmuir, Frumkin and Freudlich adsorption with general correlation coefficient above 0.9991.

Data on the corrosion inhibition effect of 2-meracaptobenzothiazole on 316 austenitic stainless steel, low carbon steel and 1060 aluminium in dilute acid media

Abstract 2-Mercaptobenzothiazole was evaluated for its corrosion inhibition effect on 316 stainless steel, low carbon steel and 1060 aluminium alloy in 3 M HCl, 1 M HCl and 2 M H2SO4 solution by coupon measurement. Results showed the organic compound performed effectively at all concentrations studied on 316 steel and 1060 aluminium with highest inhibition values of 94.07% and 79.7%. Generally, the inhibition performance of 2-mercaptobenzothiazole was above 90% at all concentrations for 316 steel and 70% for 1060 aluminium. The inhibition performance was observed to be independent of inhibitor concentration, though performance was significantly time dependant on 1060 aluminium. 2-mercaptobenzothiazole performed very poorly on low carbon steel at inhibitor concentrations above 1.25% and inhibition efficiency values below 0%. At concentrations below 1.25%, the inhibition performance was marginal at average value of 57%. 2-mercaptobenzothiazole inhibition performance on low carbon steel was observed to be time and concentration dependant.

Evidence for photochemical synthesis of fluoromethane

Cu2+ – assisted photomethylation of fluoride in dilute acetic acid medium is suggested to occur by radical halogen atom transfer, with Cu(ii) acting in a catalytic capacity.

Synthesis and Adsorption Study of some Chitosan Acid Derivatives as Dispersants for Ceramic Alumina Powders

The different functionality nature of Chitosan adds to its application as a preferable natural polymer not only for the recovery, separation, and concentration of metal ions, but for the fabrication of a wide spectrum of efficient materials, and opens a new window to act as a dispersant for ceramic particles in an aqueous medium; this is why the current study focused on getting Chitosan from chitin extracted from shrimp shells by known and modified chemical methods to obtain a high Degree of Deacetylation (DD) reached 93% to increase its solubility in dilute acidic aqueous medium. Three acid Chitosan derivatives were synthesized by grafting Chitosan chains with Glutaric, Pimelic, and Sebacic acids. The grafting process was checked by FTIR, which confirmed the compositions of the acid derivatives prepared as well as Chitosan... The ability of Chitosan and its derivatives to act as a dispersant for alumina ceramics powder was assessed by sedimentation and rheological techniques. The results showed that they have good power for deflocculating alumina particles, this implies that they may be good dispersant for ceramic processing in aqueous media which is the priority for ceramic manufacturers. The quantity of adsorbed dispersants, qe (mg/g), was determined by thermal gravimetric analysis, and hence the remaining concentration in equilibrium Ce (mg/L), four different types of adsorption isotherm models were determined and evaluated by calculating the variables and constants for each type and studying the behavior of polymers prepared toward each model. The S-shape curve was obtained from plotting qe vs Ce referring to that the adsorption follows BET isotherm of multi-layer where each layer obeys Langmuir-Freundlich isotherm.

Pertraction of Np(IV) and Pu(IV) across a flat sheet supported liquid membrane containing two N-pivoted tripodal diglycolamides

Two tripodal diglycolamide (DGA) ligands with a central N atom, dissolved in a mixture of 5% isodecanol and 95% n-dodecane, were evaluated for the liquid-liquid extraction and the pertraction across a flat sheet PTFE membrane of tetravalent Np(IV) and Pu(IV) from dilute nitric acid medium. The ligand with an isopropyl group substituted at the inner amidic N atom of the tripodal DGA ligand (termed as i-Pr3-TREN-DGA) showed higher extraction for the tetravalent actinides than the other ligand with no substitution but with a C3 instead of a C2 spacer (termed as TRPN-DGA). Although the extraction studies indicated higher extraction of Pu(IV) than Np(IV) for both the ligands, an unusual reversal in the pertraction efficiency across the supported liquid membrane was observed in nitric acid feeds. Transport parameters such as the diffusion coefficients (Do) and the permeability coefficients (P) were determined for the metal ion transport with both the ligands. The liquid membranes membrane showed poor stability, limiting their long term use.

Injectable Hydrogel through Hydrophobic Grafting on Chitosan for Controlled Drug Delivery.

An injectable hydrogel of chemically modified chitosan has been developed for controlled drug delivery application. Highly hydrophilic chitosan is chemically modified through grafting of ester-diol based polyurethane to transform into hydrogel through hydrophilic-hydrophobic balance. Grafting is confirmed through different spectroscopic techniques such as 13C NMR, UV-visible, and FTIR. Grafted copolymer shows higher contact angle as well as poorer swelling than pure one. Hydrogel of graft copolymer is made in dilute acetic acid medium. Surface morphology of the hydrogel, as investigated through SEM, exhibits an interconnected porous network suitable for drug delivery vehicle. In vitro drug release kinetics reveals that the graft copolymer releases the drug in a sustained manner as compared to the pure one. Two types of model drugs (antibacterial tetracycline hydrochloride and anticancerous doxorubicin hydrochloride) are used for release study to check the control release for various applications. The cytotoxicity of the newly developed hydrogel is accessed using the B16-F10 melanoma cell line, and the hydrogel is found to have a better biocompatible nature than that of pure chitosan. Cellular uptake of drug from graft copolymer hydrogel has considerably increased vis-à-vis pure drug resulting in significant enhancement of cell killing using the developed drug embedded hydrogel system. In vivo gelation study in an animal model verifies that the graft copolymer has the fine ability to be used as an injectable hydrogel for disease control. Hence, the developed graft copolymer has the potential to be used as an injectable hydrogel as a controlled drug delivery vehicle.

Data on the comparative evaluation of the corrosion inhibition of vanillin and vanillin admixed with rosmarinus officinalis on mild steel in dilute acid media

Abstract Study of the synergistic properties of promising corrosion inhibition compounds has been a major focus of research. Comparative evaluation of the corrosion inhibition effect of vanillin (VA) and vanillin admixed with rosmarinus officinalis (VARO) on mild steel in 1 M H2SO4 and HCl solution was performed through coupon measurement. Data obtained show VA performed effectively at all concentrations studied with optimal inhibition efficiency of 96.60% and 92.11% in H2SO4 and HCl solutions. VARO performed effectively in HCl solution with optimal value of 95.63% compared to its average performance in HCl at 66.17% in H2SO4.