Oxalic Acid Medium Research Articles

Selective recovery of Cu from copper mold production waste by organic ligands

In the present study, organic acids - oxalic acid, citric acid, tartaric acid and siderophore Desferrioxamine B were evaluated for their efficiencies to selectively recover Cu from its mold production waste. XRD analysis showed that copper mold production waste mainly consisted of Fe and Cu. The complete dissolution of this waste in aqua regia and subsequent analysis via ICP-MS revealed metal contents of 355.3 mg/g Fe and 293.9 mg/g Cu. Among all the organic acids, citric acid had the highest leaching efficiency (58.5 %) for Fe while leaching <1 % of Cu. Whereas, the leaching of Cu and Fe was poor in oxalic acid medium and Cu leaching was also negligible in tartaric acid medium. Only Fe showed 11.2 % leaching efficiency at 2 mol/L tartaric acid. The step-by-step leaching of production waste with citric acid lead to 100 % leaching of Fe while leaving 93.1 % of Cu with a yield of >99 % in the solid residue in the 4th step. Further, the siderophore Desferrioxamine B could effectively leach Fe (91.2 %) while 21.4 % leaching of Cu in 30 days. The presence of Fe impedes the leaching of Cu from the waste as demonstrated by leaching and DFT calculations due to higher stability of Fe-citrate and Fe-desferrioxamine B complex compared to Cu-organic complexes. This recycling technique described herein is simple, reliable and environmentally friendly for recovery of Cu from copper mold production waste.

Retrieval and processing of radioactive muck settled in the bottom of radioactive liquid waste storage tanks

Alkaline radioactive liquid waste storage tanks contain huge quantity of chemical muck settled at the bottom of the tank. This muck contains fission products, corrosion products, actinides and other chemicals. As the precipitate remain settled for decades, the elements get converted from hydroxides to oxy-hydroxides and oxides which are difficult to dissolve in mineral acids. Treatment feasibility of this legacy muck was studied by simulating muck using acidic radioactive liquid waste followed by its dissolution and conditioning in borosilicate glass matrix. Dissolution was better in a mixture of nitric acid and oxalic acid medium. Immobilization studies of the muck dissolved solution in borosilicate glass showed that 25% waste oxide could be immobilized in glass matrix whereas when mixed with High Level liquid Waste (HLW), 34% waste oxide could be immobilized in glass matrix. Chemical durability and thermal stability of the glass samples were evaluated and are within the appropriate limit.

Metal recovery from spent Ni-Mo-V hydrodesulphurisation catalyst in oxalic acid media by mechanochemical treatment

ABSTRACT The spent hydrodesulphurisation (HDS) catalysts used for the removal of sulphur from petroleum products can be a secondary source of especially Mo and V. This work describes the mechanochemical extraction of Mo, Ni, V, Al and P from spent petrochemical catalysts in H2C2O4. The effect of rotational speed, H2C2O4 concentration, ball to the dust weight ratio and solid-to-liquid ratio on the extraction rate of roasted spent catalyst was investigated. The reactions proceed with an increase in H2C2O4 concentration for extraction of Mo, V and P. The reactions for the extraction of Mo, V and P proceed with an increase in H2C2O4 concentration, but the dissolution behaviour of Ni is different from other elements. 87% of Mo, 44% of Ni, 82% of V, 36% of Al and 78% of P were extracted at optimum experimental conditions.

Synthesis and characterization of poly (aniline-co-p-nitroaniline) (PANA) and its corrosion-resistant properties against corrosive media

The co-polymerization of aniline with p-nitroaniline has been synthesized in oxalic acid medium, here ammonium persulfate (APS) acts as an oxidant. TGA analysis was used to study the thermal stability of the copolymer, as well as FTIR, UV–Vis spectroscopy, and XRD. The synthetic poly (aniline-co-p-nitroaniline) (PANA) is used as a barrier/redox pigment for PANA coatings. The anti-corrosion study on PANA coatings was performed with a 3% NaCl solution for up to 35 days. The coating resistance of PANA coatings is three orders of magnitude more than that of pure epoxy coatings, according to the results of electrochemical impedance spectroscopy (EIS). The scanning vibrating electrode method (SVET) was used to investigate the self-healing characteristics of this PANA coating.

Prospective evaluation of EDXRF for studying the cation exchange membrane separation of Co from Zr in oxalic acid media and comparison with radiotracer experiments

This work focuses on the selective separation of Co from Zr and Nb, for the decontamination of pressure tubes from pressurized heavy water reactor. Initial experiments were carried out using the respective radiotracers. These laboratory scale studies explore the feasibility of using oxalic acid, a benign complexing medium, for the Zr–Nb matrix, with targeted sorption of trace levels of 60Co on cation exchange membranes. Sorption of Co(II) on the membrane followed pseudo second order kinetics and the equilibrium capacity was 1.89 meq g-1. Oxalic acid concentration was a trade-off between the loading of matrix elements and the % sorption of Co(II). Energy dispersive X-ray fluorescence (EDXRF) spectrometry was used for monitoring the sorption of Co on the membrane from inactive sample solutions. Sorption improved the EDXRF detection limits for Co from 50 μg in solution to 1.3 μg on the membrane, where the total concentration of the matrix elements in solution was 50 g L-1. EDXRF method was validated by spike recovery and radiotracer studies.

The effect of electrolytes on the coating of polyaniline on mild steel by electrochemical methods and its corrosion behavior

Polyaniline (PANI) is extensively researched as a corrosion protection coating for mild steel (MS) against acidic and neutral media. Corrosion inhibition performance of PANI coating on MS depends on the electrolytic solution employed for polymerization. In this study, the electropolymerization of aniline onto MS using sodium potassium tartrate (Na-K tartrate) and benzoic acid in the alcohol-water (BAW) medium is reported. The composition of BAW system was optimized and used for electropolymerization of aniline for the first time. The results showed the formation of a passive yet electro-conductive layer before the polymerization initiated. A compact layer with a fine structured PANI coating in both media was obtained. Cyclic voltammetry (CV) produced a stable PANI coating without showing anodic current in the cathodic scan. The concentration of aniline and electrolytes were optimized for better coating conditions. The prepared PANI coating was characterized by Fourier-transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV–vis) spectroscopy, Scanning electron microscope (SEM) in combination with energy dispersion spectrometer (EDX) and X-ray diffractometer (XRD). The results of PANI coating in Na-K tartrate and BAW medium are compared with a standard PANI coating prepared in oxalic acid medium. The inhibition efficiencies of PANI coating obtained in Na-K tartrate and BAW were estimated to be 82.5 % and 99.99 %, respectively in 0.1 M NaCl solution.

Improved facile synthesis of mesoporous SBA-15-CTA using citric acid under mild conditions

Unlike being traditionally synthesized in HCl intermediates, in this study, well-ordered 2D hexagonal mesoporous silica (SBA-15) was developed under moderate polycarboxylic acid (e.g. citric acid or oxalic acid) medium without introducing inorganic salts and mineral acids. The key synthesis factors such as the type and concentration of polycarboxylic acids, preparation temperature and crystallization time are systemically studied. It was found that the amount of carboxyl groups inside the organic acid molecules plays a critical role in synthesizing high-quality mesoporous silica products owing to their bridging effects on both nonionic copolymer micelles and silica precursors. The more carboxyl groups the organic acid possesses, the less dosage of organic acid will be used. The citric acid concentration can be as low as 0.0010 molL-1 (pH ​> ​3) for forming the high quality SBA-15-CTA materials (CTA stands for the material prepared under citric acid medium) their microstructure and rod-like particle size can be tailored by varying the acid type and preparation conditions. As-synthesized SBA-15-CTA supported Ni catalysts showed a good potential for dry reforming of methane (DRM) reaction with much less coke formation at 700 ​°C. The synthesis strategy for mesoporous silica under moderate organic acid medium demonstrates a promising prospect for other mesoporous materials preparation and utilizations in catalysis, selective adsorptions, drug delivery, and so on.

Electrochemical Deposition of Polyaniline on Carbon Steel for Corrosion Study in Geothermal Solution

Polyaniline has been widely developed for many applications, e.g. sensor, supercapacitor components, electrochromic devices, and anticorrosion pigments. Although the addition of polyaniline pigment in organic coatings has been an alternative for corrosion protection in industrial applications, the protection mechanism is still not fully understood. Herein in this study, as a part of the development of polyaniline/silicon dioxide coating for geothermal application, polyaniline has been deposited electrochemically on carbon steel surface in oxalic acid medium and tested in geothermal solution to understand the contribution of polyaniline to the corrosion protection of a polyaniline-based composite in the geothermal system. To observe the surface/interface reaction between the electrolyte and electrode surface during the electrochemical polymerization, electrochemical impedance spectroscopy (EIS) was applied after each cycle. For corrosion study in the geothermal application, an artificial geothermal solution was used with the composition of 1,500 mg/l Cl-, 20 mg/l SO42-, 15 mg/l HCO3-, 200 mg/l Ca2+, 250 mg/l K+, and 600 mg/l Na+, and pH 4 to simulate a geothermal brine found in Sibayak, Indonesia. An electrochemical measurement was performed by monitoring the open circuit potential over seven days, with the interruption by EIS every 22 hours. The experiments were performed at room temperature and 150 °C (1 MPa) in an oxygen-free environment. Impedance spectra showed a reduction of the total impedance value of approximately 10 times for specimens measured at 150 °C compared to the specimens measured at room temperature, suggesting a less stable layer at high temperature.

Dissolution Kinetics Potential of a Biotite-Rich Kaolinite Ore for Industrial Applications by Oxalic Acid Solution

The increasing demand for pure aluminum and aluminum compounds of industrial quality from kaolinite ore cannot be overemphasized. Nigeria is one of the African countries endowed with abundant solid mineral resources that have not been sufficiently exploited to assist its indigenous industries. A wide array of applications of pure aluminum and its compounds are available, such as paper filling, refractories, adsorbent, catalysis, and paint additives. In this study, the upgrading of a Nigerian biotite-rich kaolinite ore by a hydrometallurgical route was investigated in oxalic acid media. During leaching studies, the effects of parameters including reaction temperature, lixiviant concentration and particle size on the extent of ore dissolution were examined. At optimal conditions (1.0 mol/L C2H2O4, 75 °C), 92.0% of the initial 10 g/L ore was reacted within 120 min. The dissolution curves from the shrinking core model were analyzed and found to conform to the assumption of surface diffusion reaction, and the calculated activation energy of 33.2 kJ/mol supported the proposed model. The unreacted product (~8.0%) analyzed by XRD was found to contain siliceous impurities and could serve as a valuable by-product for certain industries.

The role of tetraalkylammonium for controlling dealumination of zeolite Y in acid media

The use of zeolite Y as a catalyst was strictly limited in the hydrophobic system due to its low Si/Al ratio. To increase the Si/Al ratio of zeolite Y, several methods have been developed although it remains a challenge. One of the methods to increase Si/Al ratio in zeolite is by means of dealumination using an acidic medium. In the present work, dealumination of zeolite Y was investigated using oxalic acid media in the presence of tetraalkylammonium (TAA) cations. The TAA cations employed in this work were tetramethylammonium (TMA), tetraethylammonium (TEA), tetrapropylammonium (TPA), and tetrabutylammonium (TBA). TAA cations successfully protect zeolite Y framework during the dealumination process, resulting in increased Si/Al ratio with relatively preserved crystallinity. Among the TAA cations, the ability to protect zeolite Y framework during acid treatment decreases as the length of the alkyl chain increase from TMA to TPA cations. However, the trend could not be applied at TBA cation. This nonlinear correlation is attributed to the interplay between electronic and steric properties of the TAA cations.

Non-Dispersive Extraction of Ge(IV) from Aqueous Solutions by Cyanex 923: Transport and Modeling Studies

Transport process of germanium from an aqueous solution containing oxalic acid and 100 mg/L Ge was studied. Cyanex 923 immobilized in a polytetrafluoroethylene membrane was employed as a carrier in a flat-sheet supported liquid membrane (FSSLM) system. The speciation of the germanium ion in the oxalic acid medium and related diagrams were applied to study the transport of germanium. The effective parameters such as oxalic acid, carrier concentration, and strip reagent composition were evaluated in this study. Based on the experimental data, the oxalic acid and carrier concentrations of 0.075 mol/L and 20% v/v were the condition in which the efficient germanium transport was achieved, respectively. The concentration range of 0.04–0.1 mol/L was selected for sodium hydroxide (NaOH) as a strip reagent providing the best efficiency to transport germanium through the supported liquid membrane (SLM) system. Furthermore, the permeation model was obtained to calculate the mass transfer resistance of the membrane (Δm) and feed (Δf) phases. According to the results, the values of 1 and 1345 s/cm were found for Δm and Δf, respectively.

Ammodaucus Leucotrichus Cosson & Durieu fruits essential oil as corrosion inhibitor of tinplate in 0.5M oxalic acid medium and its thermodynamic properties

The anticorrosion proprieties of Ammodaucus leucotrichus Cosson & Durieu essential oil (ALEO) against the corrosion of tinplate in 0.5M oxalic acid medium was studied in the interest to improve the corrosion resistance of cans in interaction with food contains. For this, the gravimetric test, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used. The different corrosion test used show that the ALEO has an anticorrosion effect with an inhibition efficiency of 83.83% at 4g.L -1 , this can be pertained to the chemical composition of the studied essential oil. The essential oil behavior at rang temperature (303-373K) show that ALEO exhibits good inhibition even at moderate to high temperatures. The estimation of the corrosion activation parameters reveal that the essential oil shows good inhibitor characteristics with a physisorption mechanism. By using the scanning electron microscopy and energy dispersive X-rays (SEM-EDX), it is clear that the surface is remarkably improved in the presence of ALEO compared with that exposed to the acid medium without essential oil.

Effect of current density on the corrosion protection performance of polyaniline coated AISI 4140 steel

ABSTRACTThe present work reports on electropolymerisation of aniline onto AISI 4140 steel substrate at room temperature in oxalic acid media by the potentiodynamic electrodeposition method. The effect of coating current density on the morphology of conductive polymer films and their corrosion behaviour has been investigated. The electrolyte solution comprised 0.1 M aniline + 0.3 M oxalic acid. The effects of deposition current density changes (0.1, 0.2, 0.3, 0.4 and 0.5 mA cm−2) on the films were investigated. The PANI film was characterised using cyclic voltammetry and optical microscopy; it was covered with a dark green-yellow homopolymer film of strongly adherent homogeneous characteristic. The corrosion behaviour of steel electrodes with and without polyaniline (PANI) film in 3.5 wt-% NaCl solution was investigated through anodic polarisation curves. The results indicated that the PANI coating obtained under 0.2 mA cm−2 was the most corrosion protective.

Determination of the Acetyl Group in Biomass and Its Products by Headspace Gas Chromatography

This paper reports on a robust method to quantify the acetyl group in biomass and its derived liquid or solid samples using headspace gas chromatography (HS–GC). The method was based on the sample pretreatment in an oxalic acid medium (0.6 mol/L) at 150 °C and 10 min for the liquid samples or 70 min for the solid samples to convert the acetyl group to acetic acid, which can be quantified by a full evaporation HS–GC technique. It was found that ∼100 μm was the suitable solid particle size to be used in the sample analysis at the suggested pretreatment condition. The results showed that the present method has good measurement precision (relative standard deviation was less than 2.09% for the liquid sample and 2.83% for the solid sample) and accuracy (with the recoveries of 96.2–104% in the acetyl group quantification). The limit of quantification of the method was 163 mg/L for the biomass liquid samples and 0.11% for the biomass solid samples. The present method can be a valuable tool to provide the high-th...

Radiochemical separation of 231Pa from siliceous cake prior to its determination by gamma ray spectrometry

Abstract A simple and fast radiochemical method for the separation of protactinium (231Pa) from siliceous cake for its determination by gamma ray spectrometry is described. The method involves (a) a novel approach, the fusion of the siliceous cake with sodium peroxide, (b) the dissolution of the fused mass in nitric acid and (c) the co-precipitation of 231Pa with manganese dioxide formed in-situ by the addition of solid manganous sulfate and potassium permanganate to the solution. The fusion, effected in a single step, is simpler and highly effective in comparison to methods reported hitherto in literature. The radiochemical yield of 231Pa, determined using 311.9 keV gamma ray of 233Pa radiotracer is quantitative (~90%). The decontamination factors calculated using gamma ray spectrometry and energy dispersive X-ray fluorescence measurements show that the separation from the interfering radionuclides is high whereas separation from major and minor elements is good. Separation by ion-exchange method in hydrochloric acid, hydrofluoric acid and oxalic acid media have comparatively much lower yields. The concentration of 231Pa in the siliceous cake measured using interference-free 283.6 keV gamma ray was found to be (6.4±0.33) μg kg−1. The measured concentration of 231Pa was well above the limit of quantitation whereas the coefficient of variation was ~5%. The improvement in the limit of detection was due to the reduction in spectral background. Systematic evaluation of various uncertainty parameters showed that the major contributors to the combined uncertainty were efficiency of the high purity germanium detector and the counting statistics. The present sample decomposition and separation methods are robust, simple to perform and can be effectively used for the determination and hence source prospecting of protactinium.

Promising bio-composites of polypyrrole and chitosan: Surface protective and in vitro biocompatibility performance on 316L SS implants

Advanced biomedical materials can potentially be developed from combinations of natural biodegradable polymers and synthetic polymers. We synthesized bioactive composites based on polypyrrole/chitosan through in-situ electrochemical polymerization in oxalic acid medium. Surface characterization results revealed the influence of chitosan inclusion on polypyrrole (PPy) surface morphology. Contact angle results confirmed the enhancement in surface hydrophilicity due to the addition of chitosan into the PPy matrix. Electrochemical corrosion studies revealed that the composite coatings showed enhanced protective performance compared to pure PPy. Further, we investigated the effect of the composite coatings on the growth of MG-63 human osteoblast cells to assess their biocompatibility. Monte Carlo simulations were engaged to assess the interactions between the metal surface and composite coatings. The composite containing equal parts PPy and chitosan was found to be biocompatible; together with the corrosion protection results, the findings indicated that this bioactive coating material has potential for use in 316L SS implants.

Effect of Anodizing Medium on The Morphology and Photoluminescent Property of Porous Alumina Film

Anodic alumina films with uniformly distributed self assembled pores of diameters in the nanometric length scale were prepared by dual step anodization technique in oxalic, phosphoric and sulphuric acid medium. The variations of pore morphology and photoluminescent properties were studied with respect to the change in electrolytic medium. The photoluminescence (PL) spectra of the films prepared in different electrolytic medium have been recorded and compared. The PL spectra of the porous anodic alumina (PAA) film prepared in oxalic acid was found to be much stronger than the PAA prepared in phosphoric and sulphuric acid. However, pore size of the PAA films prepared in oxalic and sulphuric acid were significantly smaller than the PAA films prepared in phosphoric acid medium. Presence of oxygen deficient defect centre exerts a strong influence on the PL properties of the films.

Recovery and separation of gallium(III) and germanium(IV) from zinc refinery residues: Part I: Leaching and iron(III) removal

In this research, gallium and germanium were separated and recovered from zinc refinery residues by a two-stage leaching. In the first leaching stage with sulfuric acid media, 92% of zinc and 94% of copper were leached resulting in significant gallium and germanium enrichment up to ca. 300%. In the second leaching stage with oxalic acid media, the effects of H2C2O4 concentration, leaching time, liquid-to-solid (L/S) ratio and temperature on the recovery of gallium and germanium were investigated. More than 96% of gallium and 99% of germanium were leached out using 70g/L H2C2O4 with a L/S ratio of 10 at 90°C for 2h. The removal of iron in the H2C2O4 leach solution was carried out using an ultrasound-assisted ferrous iron precipitation method in which >96% of Fe(III) was removed in the form of FeC2O4·2H2O with minor losses of Ga(III) and Ge(IV) (1.4% and 1.3%). The results indicated that high recoveries of gallium and germanium from the zinc refinery residues could be achieved with two-stage leaching method.

Comparison of polyaniline electrodeposition on carbon steel from oxalic acid and salicylate medium

Abstract Polyaniline (PANI) coatings on carbon steel (CS) substrate were electrodeposited from two different mediums such as oxalic acid (H 2 C 2 O 4 ) and sodium salicylate (C 7 H 5 NaO 3 ). In oxalic acid, the importance of the passivation of the carbon steel surface prior to PANI electrodeposition was investigated by linear potentiodynamic test. It showed below 0.3 M oxalic acid concentration PANI film formation was not complete. The extent of passivation of the carbon steel was found to depend on the strength of the oxalic acid, which determined the formation and the nature of the PANI film. Whereas, deposition from the sodium salicylate solution did not show any passivation peak, but resulted in the formation of a transparent, uniform, compact and adherent PANI coating. The formation, morphology and characteristics of the coatings were compared by cyclic voltammetry, scanning electron microscopy (SEM) and Raman spectroscopy.

First evidence of metal transfer into hydrophobic deep eutectic and low-transition-temperature mixtures: indium extraction from hydrochloric and oxalic acids

This is the first report on metallic species transfer from aqueous hydrochloric and oxalic acid media into hydrophobic deep eutectic and low-transition-temperature mixtures composed of quaternary ammonium salts or menthol and carboxylic acids.