Use Of HNO3 Research Articles

Biocomposite of hydrochar and Lindnera jadinii with magnetic properties for adsorptive removal of cadmium ions

The aim of the work was to check the possibility of obtaining a biocomposite with magnetic properties capable of removing cadmium ions from aqueous solutions. The biocomposite consists of hydrochar obtained by hydrothermal carbonization of raffia fibers, Lindnera jadinii yeast and Fe3O4 nanoparticles. The obtained biocomposite was characterized by SEM, FTIR, VSM, XRD, TGA and BET analysis. The study examined the effect of sorption time, initial concentration of cadmium ions, temperature, the pHZPC and the reusability of the biocomposite. Based on the obtained results, non-linear equilibrium and kinetic models were selected. The equilibrium model with the highest matching factor describing the sorption of Cd(II) by the bionanocomposite was the Temkin isotherm model R2 = 0.9960 and ARE = 2.06%, while the kinetic model with the best fit was the Elovich model R2 = 0.9928 and ARE = 5.44%. The results showed that the maximum Cd(II) adsorption capacity of the biocomposite was equal to 16.34 mg/g at 25 °C and increased with increasing temperature up to 26.22 mg/g at 40 °C. The performed Cd desorption tests showed a significant efficiency of the biocomposite for five successive cycles of the sorption-desorption process with the use of HNO3, obtaining a leaching degree of 96–98.8%. The conducted research provides new data on the use of composites obtained from biomass, microorganisms and Fe3O4 in the bioremediation of heavy metals from water media and proves the effectiveness of removal and potential use in real environmental conditions of the biocomposite due to its easy recovery from contaminated aqueous solutions.

A sequential leaching procedure for efficient recovery of gold and silver from waste mobile phone printed circuit boards

The present study reports a sequential, non-acid process for effective recovery of copper and precious metals from mobile phone printed circuit boards. In this process, gold and silver were first enriched during the synthesis process of cuprous chloride and then leached by thiosulfate method. Results indicated that the distribution of gold and silver in the liquid and solid phases during the synthesis of cuprous chloride process was affected by the [Cu]/[Cu2+] ratio. Enrichment of gold and silver in the residue after the cuprous chloride synthesis could be achieved by the adjusting the [Cu]/[Cu2+] ratio. The silver and gold leaching rates of the residue after cuprous chloride synthesis (93.8 % silver and 99 % gold) were much higher than those of the raw PCB sample (27.0 % silver and 14.2 % gold) under the same conditions. This process has the advantages of high leaching efficiency, high leaching rate and avoiding the use of HNO3 or aqua regia commonly used for copper, gold and silver recovery. Thus, this study offers a promising and environmentally friendly method for recovering valuable metals from e-waste.

Development of a Culture Medium for Microalgae Production Based on Minimal Processing of Oil Palm Biomass Ash

With the increasing participation of biomass in the world energy matrix, large amounts of ash are produced through combustion, resulting in the need to dispose of this waste to minimize the environmental impact. An alternative is to use ashes as phosphorus supplements in microalgae cultures. The present work describes the development and use of a balanced culture medium based on the minimal processing of oil palm biomass ash to cultivate Arthrospira platensis Paracas, Neochloris oleoabundans UTEX 1185, and Dunaliella salina SAG 184. The acid extraction process of phosphorus (P) was defined by evaluating the following parameters: temperature (20 to 70 °C), acid load (0.01 to 0.03 mols/g of ash) of HNO3, and liquid/solid ratio (50 to 150 mLg−1). The best efficiency of the extraction process was 97%. The use of HNO3 allowed for the production of an extract containing balanced amounts of N and P sources, the BAX medium (Biomass Ash Extract). This medium was efficient for cultivating the three microorganisms studied, reaching biomass concentrations of 2.03, 0.902, and 0.69 g/L or 84%, 82%, and 99% of the control concentrations for A. platensis, N. Oleoabundans, and D. salina, respectively. In a final scaling-up test, A. platensis showed productivity of 0.047 g L−1d−1 in a 120 L tank in a greenhouse. BAX can be an alternative nutrient medium for microalgae cultivation, especially in integration with biomass-fueled biorefineries.

The Safety Assessment of Toxic Metals in Commonly Used Herbs, Spices, Tea, and Coffee in Poland.

The presented study was aimed at the determination of the level of contamination with heavy metals (Cd, Pb, As, and Hg) in 240 samples of plant materials, i.e., herbal raw materials, spices, tea, and coffee. Moreover, a probabilistic risk assessment (noncarcinogenic and carcinogenic risks) was estimated by models including target hazard quotient (THQ) and cancer risk (CR). The samples were subjected to microwave mineralisation with the use of HNO3 (65%), while the determination of the content of the elements was performed with the use of inductively coupled plasma mass spectrometer (ICP–MS) and a mercury analyser. The element which was characterised by the highest level of accumulation in the analysed samples was lead (from 0.010 to 5.680 mg/kg). Among the heavy metals under analysis, the lowest concentration was noted in the case of mercury (from 0.005 to 0.030 mg/kg). A notably higher level of contamination with heavy metals was noted in the analysed samples of herbs and spices (0.005–5.680 mg/kg), compared to samples of tea and coffee (0.005–0.791 mg/kg). According to the guidelines of the World Health Organisation (WHO) concerning the limits of contamination of samples of herbal raw materials with heavy metals, lead levels exceeding the limits were only noted in 24 samples of herbs (18%). In all of the analysed samples of spices, tea, and coffee, no instances of exceeded limits were noted for any of the analysed heavy metals. The values of TTHQmax (in relation to the consumption of the analysed products) were as follows: up to 4.23 × 10−2 for spices, up to 2.51 × 10−1 for herbs, up to 4.03 × 10−2 for China tea, and up to 1.25 × 10−1 for roasted coffee beans. As the value of THQ ≤1, there is no probability of the appearance of undesirable effects related to the consumption of the analysed group of raw materials and products of plant origin. The CR value for As (max. value) was 1.29 × 10−5, which is lower than the maximum acceptable level of 1 × 10−4 suggested by United States Environmental Protection Agency (USEPA).

Preparation of highly selective magnetic cobalt ion-imprinted polymer based on functionalized SBA-15 for removal Co2+ from aqueous solutions.

In this research, a novel magnetic cobalt ion imprinted adsorbent (Co(II)-MIIP) was synthesized by use of magnetic SBA-15 core-shell. It was functionalized by dithizone, and after identification by various techniques was used for removal of cobalt from aquatic systems. The uptake of cobalt proceeded very fast and achieved to equilibration within 5min at which 74mgg-1 of cobalt was adsorbed at pH = 8 with adsorbent dose of 0.15g. The ion imprinted sorbent exhibited good selectivity towards cobalt ions. Separation and recovery of the used sorbent was carried out respectively by use of magnetic field and by use of HNO3 (0.1M), and 85% of the initial capacity was obtained after seven 7 regeneration cycles. Different isotherm models, and error analysis were used to evaluate the experimental data. Thermodynamic, and kinetic evaluations showed that sorption process was endothermic, and described by second order kinetic model (R2 > 0.99). The equilibrium was established within five min.

Effect of nano-cellulosic fiber on mechanical and barrier properties of polylactic acid (PLA) green nanocomposite film

Most of the packaging products are made up of non-biodegradable materials resulting in environmental pollution, so the materials derived from natural resources such as polylactic acid and cellulose nanofibers have been strongly advocated as potential material for packaging application. In this work, optically transparent green nanocomposite films were prepared by the incorporation of cellulose nanofibers (1, 3, 5 wt%) into the polylactic acid (PLA) matrix using a cost-effective solvent casting method. The resulting green nanocomposite films were evaluated for morphology, structural and, thermal properties by Scanning electron microscopy (SEM), x-ray diffraction (XRD), and Thermogravimetric analysis (TGA/DTG). The Cellulose nanofibers (CNFs) prepared by directly treating the jute fiber with HNO3–NaNO2 mixture resulted in CNFs diameter of 4–6 nm and length of several micrometers. SEM results revealed the uniform dispersion of CNFs into the PLA matrix. The incorporation of CNFs improved the physical properties, such as mechanical and barrier properties (Water vapor transmission rate and oxygen permeability) of the prepared nanocomposite films. Specifically, a higher loading of 5 wt% of CNFs in the PLA matrix enhanced the barrier and mechanical properties of the nanocomposite film compared to those of the pristine PLA films. Furthermore, the prepared nanocomposite films were optically transparent and thermally stable. These results demonstrate the use of HNO3–NaNO2 Oxidized CNFs in PLA matrix that makes it possible to produce nanocomposite film that has potential in packaging application.

Procedure for the synthesis of AlSBA-15 with high aluminium content: Characterization and catalytic activity

Abstract In this study, AlSBA-15 materials with low nSi/nAl ratio were hydrothermally prepared by using three different acids, i.e. HCl, HNO3 and H2SO4, aiming to investigate the effect of the synthesis environment on their physicochemical properties. The resulting aluminium substituted molecular sieves were used as a supports for Pt catalysts. The AlSBA-15 materials and the Pt/AlSBA-15 catalysts were characterised by different techniques (N2 sorption, XRD, Py–FTIR, 27Al MAS NMR, CO chemisorption, TEM and SEM) and tested in n-heptane hydroconversion. It was found that the crystallisation of AlSBA-15 structure under the use of HNO3 led to the formation of AlSBA-15 with the highest amount of Al atoms in tetrahedral coordination. Depending on the AlSBA-15 preparation conditions, the Pt/AlSBA-15 catalysts displayed different physicochemical features, especially in term of acidity. As a consequence of the highest substitution of Al in tetrahedral positions in AlSBA-15 sample synthesised under the use of HNO3, the corresponding Pt catalyst exhibited the highest Bronsted acid sites concentration. The results of n-heptane hydroconversion showed that, this catalyst provided the highest yield of the most desired high-octane number products, i.e. multibranched heptane isomers. At the same time it was less selective towards hydrocarbons displaying the boiling temperatures higher than this of n-heptane (they are produced in cyclisation and aromatization) which are the precursors of carbonaceous deposits.

Boron‐Doped Diamond as an All‐In‐One System for the Mineralization and Detection of Lead in Waters

AbstractBoron‐doped diamond (BDD) electrodes were used in a single‐compartment electrochemical cell to monitor the degradation of organic matter (OM) and the detection of lead in water. Using sulfuric acid as the electrolyte, the mineralization step was almost complete after 20 min under galvanostatic electrolysis conditions, irrespective of the OM [i. e. phenol or humic acid (HA)]. Nevertheless, H2SO4 was not suitable for samples containing Pb(II), as it induces PbSO4 precipitation. On the other hand, the use of HNO3 resulted in a decrease in the HA degradation yield to 30 %, but remained at 90 % for phenol without any interference with respect to lead detection. Under these latter experimental conditions, the assay of Pb(II) was performed by using differential pulse anodic stripping voltammetry. The BDD electrode exhibited a linear response in the range 1–10 ppm with a normalized sensitivity of 2.66 nC ppm−1 min−1. Accurate results were obtained in solutions containing 20 ppm phenol, as compared to reference technique analysis.

Are Nitric Acid (HNO3) Digestions Efficient in Isolating Microplastics from Juvenile Fish?

A standard method for the detection and isolation of microplastics is required to adequately investigate plastic ingestion by juvenile fish. Dissections of juvenile fish guts require precise handling, which can affect the processing time if sample numbers are high. To investigate the efficacy of nitric acid (HNO3) in aiding the isolation of microplastics using whole fish, we digested juvenile glassfish, Ambassis dussumieri (Cuvier, 1828), at room temperature and at 80 °C. For a complete digestion, overnight incubation in 10 mL of 55% analytical-reagent (AR) HNO3 was sufficient for a whole fish of 1 g at room temperature. When coupled with elevated temperature, the digestion time is shortened to a few minutes and larger fish of 3 g can be digested in 30 min. Four of the five types of plastic survived the process, with nylon being the exception. This is a shortfall to the method; however, until a better method replaces it, we still value the use of HNO3 for its simple, inexpensive, swift and complete digestions of whole fish. Four fish species from two feeding guilds were digested using this method to validate its use. The number of plastic particles ingested did not differ between benthic and pelagic species and microplastic fibres comprised the majority of the plastic types found.

Method development and validation for sulfur determination via CS molecule in petroleum green coke by high resolution continuum source molecular absorption spectrometry

Development and validation of a method for determination of sulfur via CS molecule in petroleum green coke samples by high resolution continuum source molecular absorption spectrometry (HR-CS MAS) is the aim of this work. The protocol adopted for the method validation followed criteria based on international guidelines. Optimizations and determination of the analyte in the samples were carried out at the wavelength 258.0330nm, at the same spectral interval of the analytical line of Tl. Slurry prepared using Triton X-100 (0.05% v/v) without the use of HNO3, is proposed as a simple and fast sample treatment. Chemical modifier KOH (1.0% m/v) was important to promote the formation and stabilization of CS molecule. Pyrolysis and Vaporization temperatures were optimized using different compounds, ammonium sulfate, l-cysteine monohydrochloride and thiourea aqueous solutions, and also certified reference material, NIST 2718, and petroleum green coke. Compromise temperature conditions were 1000°C and 2600°C, for pyrolysis and vaporization, respectively. Aqueous calibration with thiourea presented the best condition and was chosen for the determination of the analyte. The obtained concentrations of sulfur in coke samples were between 6.20mgg−1 and 9.40mgg−1. The following parameters were evaluated as validation protocol: accuracy, precision, linearity, limits of detection and quantification, sensitivity, selectivity, robustness, working range and measurement uncertainty. Weighted least square (WLS) method was employed to estimate LOD and LOQ, since it leads to lower final uncertainty. The evaluation of the validation parameters, especially the measurement uncertainty, confirmed the satisfactory performance of the method.

Development and optimization of a standard method for extraction of microplastics in mussels by enzyme digestion of soft tissues.

The authors compared procedures for digestion of mussel soft tissues and extraction of microplastics. Complete tissue digestion was achieved with 1M NaOH, 35% HNO3 , and protease at 9.6 UHb/mL (unit hemoglobin per mL); but use of HNO3 caused unacceptable destruction of some microplastics. Recovery of microplastics spiked into mussels was similar (93 ± 10%) for NaOH and enzyme digestions. The authors recommend use of industrial enzymes based on digestion efficiency, microplastic recovery, and avoidance of caustic chemicals. Environ Toxicol Chem 2017;36:947-951. © 2016 SETAC.

Evaluation of the Use of a Reflux System for Sample Preparation of Xanthan Gum and Subsequent Determination of Ca, Cu, K, Mg, Na and Zn by Atomic Spectrometry Techniques

The aim of this study was to evaluate the performance of a reflux system adapted in the digestion tubes in sample preparation of xanthan gum for subsequent determination of Ca, Cu, K, Mg, Na and Zn by using spectrometric techniques. Through the proposed method, the samples were digested with HNO3 for 3 h in a digester block at 220 °C. The accuracy of the method was evaluated by comparing the results with another sample preparation method and by using recovery tests, which results vary between 83 and 103%. The efficiency of digestion was assessed and significant results were verified through residual carbon values, which were five times lower compared to conventional acid digestion in open system, with use of HNO3 and HClO4. The proposed methodology is a simple and accurate analytical strategy, which does not require the use of special equipment, neither a mixture of strong oxidizing acid in the sample preparation.

Kinetics of tetrabromobisphenol A (TBBPA) reactions with H2SO4, HNO3 and HCl: Implication for hydrometallurgy of electronic wastes

Hydrometallurgy is an acid leaching based process widely used for recovering precious metals from electronic wastes (e-wastes). The effects of acid leaching on the fate of brominated flame retardants (BFRs) in typical hydrometallurgical processes remain largely unknown. This study was aimed at evaluating the fate of tetrabromobisphenol A (TBBPA), a commonly used BFR, in three acid leaching reagents (i.e. H2SO4, HNO3, and HCl) commonly used in hydrometallurgy. It was found that the reactions of TBBPA with concentrated H2SO4 followed a pseudo-zero-order rate and the reaction rates declined rapidly as the concentrations of H2SO4 decreased. In contrast, TBBPA could be easily transformed in less concentrated HNO3 solutions (<21.7wt%) and the reactions followed a pseudo-first-order rate. The reaction products identified by GC–MS indicated different transformation pathways of TBBPA in H2SO4 and HNO3. HCl or HCl/H2SO4 mixtures (3:1, v/v) did not appear to react with TBBPA, while aqua regia (3:1 HCl/HNO3, v/v) reacted violently with TBBPA and led to almost complete disappearance of TBBPA within a minute. It suggested that HNO3 significantly affected the fate of TBBPA and the use of HNO3 as leaching reagents in hydrometallurgy of e-wastes should be carefully evaluated. Collectively, our findings of distinct fate of TBBPA in different acid leaching reagents provided fundamental information for design of hydrometallurgical treatment of e-wastes to minimize acid reactions with BFRs within plastics matrix and to maximize acid leaching efficiency for metals recycling processes.

Synthesis, phase evolution and properties of phase-pure nanocrystalline BiFeO3 prepared by a starch-based combustion method

The preparation of phase-pure nano-sized BiFeO3 by a combustion-like method using starch as complexing agent is described herein. Phase evolution and development of the crystallite size during the synthesis were monitored depending on the heat treatment and the composition of the (BiFe)-gels. Phase-pure BiFeO3 was obtained at a low heating rate and calcination temperatures between 500 and 600°C. Above 600°C the BiFeO3 gradually decomposed to Bi25FeO40 and Bi2Fe4O9. The investigations showed that the appearance of secondary phases depends on the heating rate, calcination temperature, and the fuel to oxidizer ratio in the (BiFe)-gel. The use of HNO3 instead of acetic acid in the preparation of the (BiFe)-gel promotes the formation of secondary phases. To study the phase stability the phase-pure BiFeO3 powder (1c) obtained after calcining at 550°C (dcryst=37nm) was sintered to ceramic bodies up to 800°C. During sintering the BiFeO3 phase decomposed to Bi25FeO40 and Bi2Fe4O9 gradually. The activation energy for the decomposition process during sintering was calculated to 337±19kJ/mol using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. Magnetic measurements on phase-pure BiFeO3 powders show maximal magnetization of about 0.7emu/g at 90kOe and coercivities between 5 and 7kOe at 300K. Investigations at 10K reveal a loop shift (exchange-bias) up to 2.9kOe in the negative direction. The optical band gaps of the phase-pure BiFeO3 powders were determined as 2.28(4)eV.

Nitration of anisol in dispersions of mesoporous oxides impregnated with heteropolyacids

Amorphous and long range ordered cubic and hexagonal silica impregnated with heteropolyacids was investigated as catalyst for nitration of anisol using HNO3 as nitrating agent. The use of HNO3 together with a solid acid catalyst is an environmentally attractive alternative to the conventional procedure that employs HNO3 together with H2SO4. The aqueous nitric acid was loaded in the pores of the mesoporous material and the HNO3 filled particles were subsequently dispersed in anisol. The reaction took place at the interface between the two liquid phases, i.e., at the pore openings. It was shown that ordered mesoporous silica is more efficient than amorphous silica and that silica with cubic geometry is the most efficient. Two heteropolyacids of Keggin type, phosphotungstic acid and phosphomolybdic acid, were tested. One Wells–Dawson type of phosphotungstic acid was included as well as cesium exchanged heteropolyacid acids of Keggin type. The best yield was obtained with mesoporous cubic silica impregnated with cesium exchanged phosphotungstic acid. The amount of heteropolyacid used in the impregnation turned out to be critical. Above a certain loading the activity went down, probably due to clogging of the pores. The preferred catalyst could also be reused with retained activity.

Trace Cd, Co, and Pb elements distribution during Sulcis coal pyrolysis: GFAAS determination with slurry sampling technique

A simple and fast method based on graphite furnace atomic absorption spectrometry (GF AAS) and slurry sampling technique (SlS) was developed to determine trace Cd, Co and Pb in high-sulphur coal (Sulcis, Italy) and coal chars derived at 600, 750 and 950°C under N2 atmosphere for developing a clean coal for electricity production. The proposed method was then coupled to a four-step sequential chemical extraction method for assessment of metals distribution in coaled samples. The slurries were prepared by varying sample mass (1–50mg), volume (1–3mL) and kind of dispersing medium (1% v/v Triton X-100 and 2N HNO3), and sonication time (5–30min). Pyrolysis/atomization temperatures as well carrier gas flow rate were optimised. Pd(NO3)2 and NH4H2PO4 were employed to stabilize Cd and Pb, respectively, in the pyrolysis stage of furnace program. The use of HNO3 as dispersing agent was found to be effective in lowering the high level of background absorption on the Cd analytical signal produced by raw coal matrix. Conversely, coal charred samples did not show significantly level of background interferences, so that Triton X-100 dispersing agent could be used for all analytes. Calibration curve against acid-matched standards was allowed for Cd, whereas the standard addition calibration was used for Co and Pb owing to chemical matrix interferences. The precision, expressed as relative standard deviation (% RSD, n=5), was better than 5% for Cd, Co, and Pb at 1, 10, and 15μgL−1 levels, respectively. The accuracy of the analytical method was checked by analyzing a BCR No. 182 steam coal certificated reference material and the results were in good agreement with certificated and informed values. The solid detection limits (3σblank) were as low as 0.001 Cd, 0.01 Co, and 0.01 Pb mgkg−1, using 30mg sample mass and slurry concentration of 30m v−1 for Cd, and 50mg sample mass and 50m v−1 slurry concentration for Co and Pb. The content of elements in Sulcis coal was found to be 0.33 Cd, 4.0 Co, and 3.8 Pb mgkg−1 and mostly associated to sulphates and di-sulphides as indicated by the leaching test. Under pyrolysis conditions Cd significantly volatilised (about 64%) at temperature higher than 600°C, whereas residue chars at 950°C are enriched in Co and Pb up to 20%. The proposed method is suitable for routine metals monitoring in coaled samples.

Use of HNO3 as the source of NO to prepare a nitric oxide complex of ruthenium

Reaction of cis-Ru(bisox)(2)Cl(2), where bisox is 4,4,4',4'-tetramethyl-2,2'-bisoxazoline, with HNO(3) in 1 : 4 molar proportion in boiling water under N(2) atmosphere and subsequent addition of an excess of NaClO(4).H(2)O yields [Ru(bisox)(HL)(NO)](ClO(4))(NO(3)) (1). HL is a hydrolysed form of bisox where one of the oxazoline rings opens up. X-Ray crystallography shows that 1 contains an octahedral RuN(5)O core. HL binds the metal through an imino N, an amide N and an alcoholic O atom. Reaction of cis-Ru(bisox)(2)Cl(2) with an excess of NaNO(2) in water gives cis-Ru(bisox)(2)(NO(2))(2) (2). On acidification by HClO(4) in methanol, is smoothly converted to cis-[Ru(bisox)(2)(NO(2))(NO)](ClO(4))(2) (3) due to equilibrium (1). [Formula: see text] (1) The X-ray crystal structures of 2 and 3 have also been determined. NO binds Ru in 1 and 3 linearly. The Ru-NO bond length in 1 is 1.764(13) A and that in 3 is approximately 1.78 A. All the three complexes have been characterised by FTIR, NMR and ESIMS. The NO stretching frequencies in 1 and 3 are 1897 and 1936 cm(-1) respectively. While 3 reverts back to 2 readily in presence of OH(-) [equilibrium (1)], 1 does not react with OH(-). It is concluded that while in the reaction of cis-Ru(bisox)(2)Cl(2) with HNO(3), bisox is hydrolysed following abstraction of NO from HNO(3), generation of the nitrosyl complex 3 via reaction (1) is not accompanied with such hydrolysis.

Determination of trace aluminum concentration and homogeneity in biological reference material TORT-1 by instrumental neutron activation analysis and graphite furnace atomic absorption spectroscopy

The biological reference material TORT-1, lobster hepatopancreas, was analyzed for aluminum by instrumental neutron activation analysis (INAA) and graphite furnace atomic absorption spectroscopy (GFAAS). After correction of the INAA results for interferences from 28Al produced by 31P(n,α)28Al and 28Si(n,p)28Al reactions, and use of HNO3 plus HF for sample dissolution for the GFAAS analyses, the methods gave similar results of 43 ± 3 and 42 ± 2 μg/g respectively for 200 to 300-mg test portions. Analysis of six portions from each of six bottles of TORT-1 showed no statistical difference at the 95% confidence level for the between and within bottle variances. Therefore, the material can be considered homogeneous for aluminum if 200- to 300-mg test portions are taken. The variance was greater and the average lower when 30-mg test portions were analyzed for aluminum by GFAAS. The pattern of the results, together with the need for HF in the dissolution procedure, suggests the presence of aluminum-containing microparticulate mineral matter, perhaps silicate material, in the material.

Improvement of Continuity of the Alloy Layer of Electrolytic Tinplate: Experiments with Oxidizing Pickling Agents

SummaryIn continued attempts to determine factors affecting the corrosion behaviour of tinplate, an examination has been made of various pickling treatments for steel prior to laboratory acid tinning and flowmelting. Corrosion behaviour has been assessed by the “Special Property” tests which are currently used to assess tinplate in relation to shelf life of cans. Results have shown that the use of HNO3 as a pickling treatment prior to tinplating can be extremely effective in improving corrosion behaviour. Optimum concentration was shown to be 5% w/v. An explanation for the improved corrosion behaviour is offered in terms of improved alloy (FeSn2) continuity which in turn is dependent on the effect of HNO3 on the steel surface prior to tinplating. Reference is made to a commercial trial which confirms the laboratory experimental results.