Spent Pickle Liquor Research Articles

Interpreting the main effects on the efficiency and morphology for establishing a procedure of electrodepositing Zn from purified chloride SPL solutions

Potentiodynamic and galvanostatic experiments have been used to investigate the electrodeposition of Zn and to develop a reliable recovery method from a purified spent pickling liquor (SPL) of hot dip galvanization. The main bjective was to find the suitable conditions to deposit high-grade Zn from the purified ZnCl2–HCl–NaCl solution in a conventional electrowinning cell holding the stationary electrolyte. The effects of pH (1.5–4.5) in and Zn concentration (30–150 g/dm3) in the stationary electrolytes were studied first by the potentiodynamic method to reveal the major characteristics of the cathodic process and to give reference for further practical examinations by the galvanostatic technique. The electrowinning experiments pointed out the effects of these major parameters, beside other practical factors, like apparent current density (c.d.) and additional NaCl concentration. The long-term galvanostatic experiments proved that the current efficiency (c.e.) increases significantly as the pH and the Zn concentration are increased. A c.e. of ~ 99% can be reached with an electrolyte of pH ~ 5, Zn concentration ~ 50 g/dm3 applying a c.d. in the 300–600 A/m2 range. Increasing the Zn concentration could considerably improve also the deposit morphology. The addition of NaCl can practically improve the c.e. if the Zn concentration is at least around 50 g/dm3. In contrast, this improvement is largely off-set by the negative effects of strong H2 evolution at low (e.g. < 10 g/dm3) Zn concentrations. Extremely high Cl− ion concentrations, however, inhibit the cathodic reaction by stronger chloro-complex formation. In this case the intensive H+ reduction causes hydroxide precipitation.

Extraction of zinc from spent pickle liquor using primary amine extraction system

Spent pickle liquor is a hazardous liquid containing zinc and iron ions, and other environmentally harmful elements. Therefore, its discharge is prohibited because of ecological and environmental issues. A novel cleaning process for the recovery of Zn from spent pickle liquor using solvent extraction was proposed. The extraction system comprised a secondary carbon primary amine (N1923), isooctanol, and sulfonated kerosene. Spent pickle liquor after ultrasonic enhanced reduction pretreatment was studied experimentally, and effective parameters such as the extractant concentration, organic phase composition, and phase ratio (O/A) on the extraction were investigated. The extractant N1923 was found to selectively extract Zn(II) from the spent pickle liquor and retain Fe(II) in the raffinate. The concentration of Zn(II) ions in raffinate obtained using three-stage counter-current extraction was only 0.01 g/L. The raffinate could be further used to prepare an iron salt water purifier. A solution of H2SO4 was used to strip Zn from the loaded organic phase, yielding a Zn-rich solution containing 5.39 mol/L Zn, which could be used to prepare ZnO. The unloaded organic phase was recycled, and no emulsification or scale accumulation was observed during the process. The structure of the extracted complex was determined using the slope and loading capacity methods, and combined with FT-IR analysis. The main reaction that occurs during the extraction process is the anion-exchange reaction, with a stoichiometric ratio of N1923 to zinc ions of 1, resulting in an extracted complex of RNH3ZnCl3. Overall, the process provided an efficient, low-consumption, convenient, safe, and sustainable method for recovering Zn from spent pickle liquor and laying the foundation for industrial applications.

Catalytic pyrolysis of lignite with clay catalyst activated with spent pickling liquor

AbstractSpent pickling liquor (SPL) is an acidic waste with rich iron content from the stainless steel production industry. Reusability of SPL as a catalytic activity promoter in bentonite clay is crucial for the catalytic pyrolysis of various materials like biomass, coal, and waste plastics. For this aim, the bentonite catalyst activated with the SPL nomenclatured as SPL‐treated bentonite (SPLAB) catalyst was employed in the catalytic pyrolysis of lignite for an oil product with high yield and quality. The SPL‐treated bentonite catalytic pyrolysis oil (SPLABO) for the conditions of the final temperature of 600°C, heating rate of 10°C/min, and catalyst ratio of 15 wt% had a yield of 26.35 ± 1.14 wt% and good fuel properties in view of the higher heating value of 35.23 MJ/kg and density of 1076.4 kg/m3 at 20°C. Moreover, it has a rich chemical content by means of monocyclic aromatics and shorter chain alkanes compared with that of the thermal activated bentonite oil (TABO). Based on the chemical structure analysis results of the SPLABO and TABO comparatively, it was concluded that the SPL agent used as a catalytic activity promoter led to a significant increase in the catalytic activity of bentonite catalyst.

Potentiodynamic Study of The Effects of Nickel on The Electrodeposition of Zinc from Chloride Media

Abstract. The potentiodynamic experiments of the nickel effects on the zinc electrodeposition have been done to understand the impact of Ni impurities on the electrowinning of Zn from spent pickling liquor. The nickel chloride solutions of Ni concentrations 90 and 1 g/dm3 were used as the electrolytes. The latter was also mixed with 90 g/dm3 Zn in the experiments. All the runs were carried out at room temperature with 40 mV/s continuous polarization speed and with 1/s sampling rate. It was observed that nickel electrodeposition from chloride media containing 90 g/dm3 Ni started with the generation of hydrogen bubbles, entirely blocking the cathode surface. Only a slight current development was observed until the polarization potential ~ -0,8 V. The visual observation showed bubbles also formed at the anode, which may represent chlorine and/or oxygen evolution. While, in the electrodeposition of nickel with only 1 g/dm3 Ni concentration in the electrolyte, metal deposition was hardly observed, but visible hydrogen bubbles constantly blocked the cathode surface. A similar tendency was observed in the mixed-solution electrolysis cell; the initial tiny bubbles accumulated at the cathode surface more than in the pure Zn solution. The enhancement of H2 evolution indicates how nickel deposition may contribute to the loss of useful current in the process of Zn electrodeposition. The mass of nickel deposited from the mixed solutions significantly decreases as the Ni concentration decreases in the electrolyte, while the mass of deposited zinc is relatively constant. It means that the purity of the produced Zn is appreciably higher – with respect to Ni – if nickel is efficiently eliminated from the solution before electrowinning.

(Digital Presentation) The Role of Iron in the Zinc Electrodeposition from Chloride Media for Recovering Zinc from Spent Pickling Liquors

Electrodeposition of Zn from chloride media had been studied by potentiodynamic method to understand the characteristics of Zn recovery from spent pickling liquor (SPL). Various concentration, pH, agitation speed and impurities contamination were examined in the series of experiments. The influence of Zn concentration in the range of 30-150 g/dm3 relevant to the real SPL were studied along with acidity level change (pH 1.5-5.5). It was found that the cathodic deposition started with the uniform patern followed by sponge-like deposit and as the concentration of the electrolyte near the cathode surface decreased, the dendritic deposition start to grow, especially at the edge of the cathodes.It was found that the effect of iron concentration on the polarization curves of zinc from SPL is complex. Initially it has a negative effect on the generated cathodic current because of the enhancement of hydrogen bubble formation. At a higher concentration range, however, iron deposits at a relatively higher rate. Further increased iron concentrations may make the composition of the Zn-Fe deposit dominantly in favor of iron, resulting in a hydrogen dominated cathodic mechanism. It is also characterised by the loss of the dendritic structure – attributed mostly of zinc deposition when hydrogen bubbles are not blocking the cathode. As the gas evolution becomes more characteristic, the deposit tends to become more powdery. Under such conditions the cathode becomes smoother and the active surface is reduced. Increasing the stirring speed, the powder was easily detached from the cathode surface. Iron, however can enhance the cathodic deposition process of zinc. With 30 – 60 g/dm3 iron in the 90 g/dm3 Zn solution, an increased iron concentration resulted in a significant increase in the mass of the deposited zinc. This may be interpreted by a beneficial effect of the increased hydrogen evolution enhancing the zinc ion transport to the electrode surface. However further increments of iron had a contrary effect, possibly by the locally increased – and generally detected – pH of the solution indirectly causing a superficial precipitation of hydroxides. Technically pure zinc could be deposited from only low-iron (< < 30 g/dm3) zinc solutions (of 90 g/dm3 Zn) at relatively vigorous stirring speeds. High iron concentration in the solution is definitely unsuitable for obtaining the aimed quality of cathode zinc.

Recovery of zinc and iron from hot-dip galvanizing spent pickle liquor using solvent extraction

The disposal of spent pickle liquor from the hot-dip galvanizing process is of serious environmental concern that demands development of safe and economical methods. The present work attempts to extract zinc and iron utilizing a mixture of trialkyl-phosphine oxide (Cyanex 923) as the extractant. Isooctanol and sulfonated kerosene was mixed with the extractant to improve the mass transfer as well as to suppress emulsification. The effect of the extractant concentration, organic phase composition, contact duration, temperature, phase ratio (O/A) were assessed to identify the optimal process conditions. A thorough analysis of the zinc extraction mechanism was carried out utilizing FT-IR, Raman spectroscopy, and ESI-MS analysis. The structures of extractant and extraction complex were simulated using density functional theory (DFT), the overall situation and the local activity index were calculated. The extraction mechanism is proposed based on theoretical simulation and characterization, supported by the experimental results. The extraction process was identified to be exothermic in nature with the extraction efficiency of zinc as high as 95.57% under the optimal conditions. The extraction efficiency of 99.99% for zinc and 1.90% for iron could be achieved in a three-stage countercurrent extraction process. The single stage stripping efficiency of zinc was 95.25% with 0.8 mol/L HNO3. The extraction efficiency of zinc was 92.50% after five extraction and stripping cycles.

Valorization of secondary resources into silica-based adsorbents: Preparation, characterization and application in dye removal from wastewater

Low-cost silica, magnetite, and magnetic silica were prepared using corn cob and spent pickle liquor. To enhance the adsorption characteristics, the extracted silica was heat-treated and the ratio of silica:magnetite was optimized. A detailed characterization of the prepared materials was conducted and the adsorption characteristics were also inclusively assessed.The characterization study disclosed that the prepared materials were nanosized, nonporous, and forms large aggregates with inter-particles voids. The prepared silica was amorphous and heat treatment of extracted silica increased the specific surface area greatly. The superparamagnetism and consequent magnetic separability is an advantage of magnetic silica. The adsorption study showed that the optimum silica:magnetite ratio, solution initial pH, and adsorbent dosage were 1:10, 3 and 2 g/L, respectively. The adsorption kinetics obeyed the pseudo-second-order equation while the adsorption isotherm was best described by Langmuir model. Magnetic silica provides a balance between the adsorption capacity (19 mg/g) and magnetic separation possibility after wastewater treatment. Amongst the different prepared materials, heat-treated silica achieved the highest adsorption capacity (44 mg/g) toward RhB and was better than many other adsorbents reported in the literature.

An investigation on optimum grinding system and conditions for steel plant ARP by-product α-Fe2O3 for pigment industry

After some other processes, α-Fe2O3 red powder particles -by-product of regeneration of spent pickling liquor in ARP in iron and steel industry- should be ground up to pigment grade to convert it to a value added product, red iron oxide pigment. In this study, grinding tests on α-Fe2O3 red powder were performed using four different types of laboratory-scale mills, namely the vibrating cup mill, vertical ball mill, planetary ball mill, and fluidized bed jet mill. The particle structure of the α-Fe2O3 was investigated by SEM, while its chemical composition was determined by ICP-OES, density, LOI, humidity, Cl content etc. were determined by laboratory tests. Particle size distribution and surface area value of each ground sample was determined using the laser diffraction method. Targeted particle size distribution ranges could only be achieved with the jet mill. Other mills encountered caking and adhesion problem with α- Fe2O3. It was assessed that the adhesion to the inner walls of the grinding chamber and the caking effect were both caused by the humidity content of the material. The grinding yield of the material was found to increase with increased jet mill grinding air pressure (0.8, 3.2 and 7 bars).

Pyrometallurgical recycling of stainless steel pickling sludge: a review

Stainless steel pickling sludge (SSPS), generated from the lime neutralization process of spent pickling liquor, is classified as a hazardous waste consisting of abundant metals like Fe, Cr and Ni, and other elements like F, S and Na, etc. Rather than a common disposal in landfill, recovering these metals and other valuable components from SSPS can not only create economic benefits, but also eliminate its adverse impacts on human health and the environment. A review of the formation mechanism and basic properties of SSPS was made, and the technical features, advantages and limitations of a series of pyrometallurgical treatment processes were summarized. Based on these, the main challenges for recycling of SSPS through the existing techniques are demonstrated. The traditional pelletizing/sintering-blast furnace process can only be used as a partial solution. Direct use of SSPS as flux in an argon–oxygen decarburization converter or electric arc furnace is a promising way, but low S sludges are preferred. The STAR process shows excellent recovery for metals, but it also has a low tolerance to the S and F contents in SSPS. And the INMETCO process is highly flexible in treatment of various wastes, whereas it exhibits relatively low Cr recovery and produces poor-quality pig iron. In addition, the feasibility of the rotary kiln-electric furnace, solid-state reduction of chromite and reduction-magnetic separation processes requires further studies. An urgent task at present is to develop a system for scientific classification and separate collection of SSPS in terms of chemical composition, notably S and F contents.

SYNTHESIS OF MAGNETIC NANOPARTICLES FROM SPENT PICKING LIQUORS IN AQUEOUS SATURATED SOLUTION OF CALCIUM HYDROXIDE

Spent pickling liquor is a considered hazardous waste because of its very high level of acidity and high metal concentration, and the conventional neutralization method regenerates an excessive quantity of sludge that poses a serious problem concerning to the landfill disposal and risk of ground water contamination. Therefore, recovery of spent pickling liquor is necessary. Several approaches have been investigated for spent pickling liquor recovery, but they are generally costly and lead to produce various iron salts or oxides which have a limited value. In the present study, we explore the potential of using spent pickling liquor as iron precursor for the synthesis of magnetic nanoparticles. Here, Fe3O4 nanoparticles were prepared easily by oxidation-precipitation from spent hydrochloride acid pickling liquors in aqueous saturated solution of calcium hydroxide at room temperature, in the air, and under suitable speed of rotation. The FT-IR, XRD and TEM results shown that monodisperse Fe3O4 nanoparticles in the size range of 10-25 nm were obtained, with a high level of crystallinity. The BET surface area was about 46 m2 g-1. The synthesized Fe3O4 nanoparticles exhibited the superparamagnetic behavior with relatively high saturation magnetization, Ms = 73 emu/g. The synthesis procedure of magnetic nanoparticles revealed here will provide a new possibility for spent pickling liquors recovery more effectively.&#x0D; For citation:&#x0D; Vu Minh X., Le Ha T. T., Pham Lan T., Pham Nam H., Le Huong T. M., Le Lu T. Nguyen Dung T. Synthesis of magnetic nanoparticles from spent picking liquors in aqueous saturated solution of calcium hydroxide. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 59-63

Electrochemical Removal of Copper from Regenerated Pickling Solutions of Steel Plants

The spent pickle liquor contains the dissolved metal salts of iron, chrome, copper, nickel and zinc [1]. The acid can be cleaned from its impurities, except for its copper ion, by the regeneration process. When the copper concentration of the pickling solution exceeds the level of about 100 ppm, the copper inside the solution replaces the iron in the steel and copper starts plating randomly on the metal surface in the following pickling processes. Because of the plating problem, the acid needs to be discard from the acid line. By adding fresh acid to the line the discarding can be delayed [2]. An electrochemical procedure was conducted to overcome the cementation problem experimentally in an environmental and economical way. Electrowinning of dilute copper from strong acid solution is a challenge in this case so the optimum current density, electrolysis duration and the electrode materials were determined in this study. It was found that increase in the current density and electrolysis duration increases the copper removal, but changes the morphology of deposits. A slower compact deposition procedure was selected to achieve continuous removal of copper instead of faster discontinuous powder deposition from the regenerated pickling solutions of steel plants.

Processing of spent pickling liquor formed during treatment of titanium products

The article presents the research findings on processing of spent acid pickling liquor (SAPL) formed during etching of titanium products. The processing includes neutralizing the SAPL with alkali, filtering, drying and calcining the titanium hydroxide precipitate as well as electrochemical processing of the filtrate in an ion-exchange membrane cell. The proposed SAPL processing procedure allows obtaining titanium dioxide, sodium hydroxide and a mixture of acids. Titanium dioxide can be used in paint-and-varnish industry. The alkali can be used in neutralizing the SAPL. A mixture of acids is suitable for use in etching process of titanium products.

산세수와 게껍질을 이용한 신기능성 철분 비료의 상추 생육 촉진 효과

작물 재배에서 빈번히 발생되는 철분 부족 현상은 식물의 생육 저하와 생산성 감소를 야기한다. 철분의 흡수는 철분 킬레이트제를 이용해서 높일 수 있다. 본 연구에서는 제철산업의 부산물인 산세수 유래의 2가 철 이온을 게껍질(CSP)에 킬레이트시킨 신기능성 철분 비료(FCSP)를 제작하고, 상추 재배에 적용하여 생육 촉진 효과를 분석하였다. 제조한 철 비료의 효과를 검증하기 위해, 연구실 내 소규모 시험에서 무처리구, 게껍질 처리구, 그리고 여러 농도의 Fe-게껍질 킬레이트 처리구에서 상추의 생장을 분석한 결과, 50 ppm Fe-게껍질 킬레이트 처리구에서 엽수, 엽중, 엽장 및 엽폭이 무처리구와 게껍질 처리구에 비해 증가하였으며, 상추 잎의 엽록소의 함량 또한 증가하였다. 포장 시험 역시 50 ppm Fe-게껍질 킬레이트 처리구에서 엽수, 엽중, 엽장 및 엽폭에서 화학비료와 퇴비를 혼합한 기존 재배 방식 처리구에 비해 최대 2배 이상의 증가를 보였고, 식물체내 Fe의 함량 또한 가장 높게 나타났다. 또한 철 이온을 게껍질에 킬레이트한 비료의 처리가 토양 내의 Fe와 Ca의 함량을 증가시켰으며 유효인산과 유기물의 함량 또한 증가시켜 토질을 개선시키는 효과를 보였다. 이러한 결과들을 종합할 때, Fe-게껍질 킬레이트 복합체는 기존의 비료 처리 방식인 화학비료와 퇴비 사용 보다 뛰어난 생육 증대 효과와 토질 개선 효과를 나타냄으로써 작물 재배에 있어서 효과적인 신기능성 철분 소재로서 활용 가치가 있을 것으로 사료된다. Iron (Fe) is an important micronutrient for the health and growth of plants. Iron is usually provided by fertilizers, and iron-chelate fertilizers are well absorbed by plants. This study presents the plant growth-promoting effects of a new functional iron fertilizer, Fe-chelating crab shell powder (FCSP), which is generated from the chelation of Fe ions with crab shell powder. Iron chelate was derived from spent pickling liquor, which is rich in reductive iron, iron(II) oxide. To analyze the effects of FCSP on plant growth, we treated lettuce with several concentrations of FCSP in both lab- and field-scale experiments. In the lab-scale test, the treatment of 50 ppm of FCSP highly promoted growth and resulted in increases in the size, weight, number and chlorophylls content of leaves of plants compared to the treatment of crab shell powder. Fifty ppm of FCSP also increased the size and weight of leaves up to 2 times compared to the application of chemical fertilizer and/or compost in field conditions. In addition, the FCSP treatment resulted in the highest ion uptake of Fe in lettuce leaves. Moreover, FCSP led to increases in the amounts of Fe, Ca, available phosphorus and organic matter in treated soil, indicating that soil quality was improved. Taken together, our results demonstrate that FCSP promotes lettuce growth via enhancement of Fe availability and improves soil quality. Therefore, FCSP can be utilized as a new functional iron fertilizer.

Two-step process of regeneration of acid(s) from ZrF4 containing spent pickle liquor and recovery of zirconium metal

In this paper we describe a progressive two-step process that allows zirconium fluoride (ZrF4) contained in spent baths for etched zirconium alloys to be effectively recycled on a pilot scale and produce a high purity regenerated pickling acid. In the first step, a spent pickling liquor is treated by a BaF2 suspension to produce water insoluble Ba2ZrF8. After filtration of Ba2ZrF8 more than 99.9 wt % purity pickling acid is regenerated. The precipitation mechanism of Ba2ZrF8 is discussed and the role of BaF2 particles size on the precipitation process is demonstrated. In the second step the as-precipitated Ba2ZrF8 is mixed with Mg and Cu metal powders and heat-treated at 1200 °C (or above) to produce CuZr alloy ingot. The characteristics of the ingot are discussed in regard to Cu concentration and the heating temperature.

Crystalline-selected synthesis of ferrous oxalate dihydrate from spent pickle liquor

Ferrous oxalate dihydrate with different crystalline structures, polymorphs and sizes have been synthesized through a facile precipitation reaction from spent pickling liquors (SPL) by controlling synthesis conditions. The β-FeC2 O4 · 2H2 O in orthorhombic phase can be formed at room temperature, whereas α-FeC2 O4 · 2H2 O with a monoclinic unit cell can be obtained after aging at 80 °C. With the increasing aging temperature, the morphology of samples can be tailored from flower-like to prismatic-like and the particle-sizes are decreased. Innovatively, thermal decomposition behaviors of products have been investigated in details by X-ray diffraction pattern (XRD) and thermal gravimetric-differential scanning calorimetry (TG-DSC). The results show that both FeC2 O4 · 2H2 O samples can be transformed to α-Fe2 O3 in air atmosphere and Fe3 O4 in argon atmosphere at T ≧ 400 °C. In air atmosphere, there are two sharp exothermic peaks for β-FeC2 O4 · 2H2 O (250 °C) and α-FeC2 O4 · 2H2 O (239.5 °C) correspond to the decomposition reactions. In argon atmosphere, the decomposition end temperatures are 500 °C and 430 °C for β-FeC2O4 · 2H2O and α-FeC2O4 · 2H2O, respectively. This indicates that β-FeC2O4 · 2H2O has higher thermal stability in comparison with α-FeC2O4 · 2H2O.

A symmetric aqueous rechargeable battery based on NiFe2O4 derived from industrial effluents

Two different industrial effluents, spent pickle liquor and Ni-containing wastewater, were simultaneously treated via chemical precipitation and hydrothermal reaction to generate valuable NiFe2O4. Subsequently, the NiFe2O4 was used to construct a NiFe2O4//NiFe2O4 symmetric battery. The assembling process of NiFe2O4//NiFe2O4 symmetric battery is very simple since both the cathode and anode are the same material and the manufacturing cost for practical application is low. The NiFe2O4//NiFe2O4 symmetric battery was able to deliver specific capacity 23.1mAh/g based on the total mass of the active materials at discharging current densities 0.5A/g. After 500 charge-discharges cycles, the crystalline structure of NiFe2O4 still exhibit good stability and can pass the TCLP limits to be regarded as a general industrial waste. This research not only removes the heavy metal from two wastewaters to avoid the environmental risks but also provides an effective method to turn “waste” into useful materials.

Simulation of a regeneration plant for spent pickling solutions via spray roasting

Nowadays, pyrohydrolysis techniques are widely applied for regeneration of spent pickling liquors providing an excellent environmental and economical strategy to the problem of waste disposal/recovery, also thanks to the high acid recovery efficiencies (>99%) achieved. In fact, in these processes, iron chlorides are converted into iron oxides and hydrogen chloride at high temperature in spray roasting or fluidized bed reactors. Though the state-of-the-art technologies have been successfully applied only to large-scale plants, the development of small-scale units, able to perform a delocalized regeneration of spent solutions where these latter are actually produced, would be strongly needed in order to minimize the transportation of hazardous spent pickling and fresh HCl solutions to/from pickling factories from/to large centralized regeneration plants. In the present work, a steady-state simulation model for regeneration of spent pickling liquor via spray roasting has been developed, aiming at the analysis of performance of a small-scale unit. The simulation and optimization of the process has been carried out using Aspen Plus simulator. A simplified model of the spray roaster, based on the data collected from studies reported in the literature, has been implemented and exported from Aspen Custom Modeler. Solid recovery from roaster off-gases has been obtained by a cyclone and a Venturi scrubber, where the spent pickling liquor is concentrated prior to be sprayed into the reactor. Hydrogen chloride is absorbed in an adiabatic absorber, where a sub-azeotropic (18–20 wt%) hydrochloric solution is obtained. Prior to the stack, a scrubber is required to wash off the exhaust gases. Several parametric studies have been performed. Different designs of solid separators have been compared in order to investigate the particulate separation efficiency of the process, while absorption column’s packing types and rinse water flow rates have been varied in order to investigate their effects on HCl recovery and acid gas emissions.

Low temperature hydrothermal synthesis and characterization of iron oxide powders of diverse morphologies from spent pickle liquor

Iron oxide nanoparticles (goethite and hematite) of various shapes have been synthesized through a simple hydrothermal reaction from the stripped solution of Fe(III) obtained after extraction and separation of Zn and Fe from spent pickle liquor. The influence of pH and synthesis time on the structure and morphology of the as-prepared α-Fe2O3 are investigated. It was possible to control the particle size and shape by adjusting the pH (2–12) of the starting solutions and time of synthesis (1–6h). Under the appropriate conditions, rod-like α-FeOOH (goethite) and hexagonal α-Fe2O3 (hematite) materials of the uniform nano-crystalline structure were selectively synthesized in large quantities. The morphology and structure of the final products were investigated in detail by X-ray powder diffraction pattern (XRD), transmission electron microscopy (TEM), Raman spectroscopy and vibrational sample magnetometer (VSM). The probable mechanism of formation of uniform α-FeOOH and α-Fe2O3 nano-particles is discussed on the basis of the experimental results and characterization studies. The evaluation of the magnetic property has established the weak ferromagnetism characteristics of both goethite and hematite at room temperature.

Solvent extraction and separation of zinc and iron from spent pickle liquor

The present study reports liquid-liquid extraction and separation of zinc and iron values from a spent pickle solution. Tertiary amine viz. tri-iso-octyl amine (TiOA) or tris(2-ethylhexyl) amine (TEHA), in the absence and presence of di-(2-ethylhexyl)phosphoric acid (HDEHP), has been used for the separation of zinc and iron. Three aqueous solutions were investigated: i) HCl–Fe(II)–Fe(III), ii) Zn(II)–HCl, and iii) HCl–Fe(II)–Fe(III)–Zn(II) with the composition similar to that of pickle liquor (g/L) [117 Zn(II), 90 HCl, 30 Fe(II) and 1 Fe(III)]. Co-extraction of Zn(II), HCl and Fe(III) was noticed with the extractants (amine/amine+HDEHP) without any appreciable selectivity except for Fe(II) which was not extracted by the solvent. Zn(II) was extracted selectively leaving Fe(II) in the raffinate provided that Fe(III) was removed from the solution at a low O/A phase ratio or reduced to Fe(II) state. Stripping of HCl, Zn(II) and Fe(III) was also not selective with distilled water. The Zn(II) free raffinate containing Fe(II) was microbially oxidized to Fe(III) and was then quantitatively extracted in 3-stages with 30% Versatic 10 acid at the O/A phase ratio of 3.5:1. Loaded Fe(III) was easily stripped from the organic phase with dilute sulfuric acid. A flowsheet is proposed to produce high purity Zn(II) and Fe(III) solutions by solvent extraction.

A study on treatment methods of spent pickling liquor generated by pickling process of steel

Metals to be coated require pre-treatment to remove rust or scale, impurities and inorganic contaminants. In steel industries, pickling process generates a considerable quantity of Spent Pickle Liquor (SPL) containing the dissolved metal salts of iron, chromium, copper, nickel and zinc as well as residual free acid. The waste generated by metal pickling and electroplating industries is identified as hazardous solid waste as per Indian Standards and United State Environmental Protection Agency (US EPA). This paper discusses the advantages and disadvantages of treatment methods of spent pickling liquor generated by pickling line of steel. The discussion shows that treatment method depends upon the quantity, quality and composition of SPL. Experimental modelling helps in better understanding of treatment process and also craft process more technically and economically feasible.