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Mondal, Kanchan; Mandich, N. V.; Lalvani, Shashi B.

doi:10.1023/a:1004107117531

Cited by 13 publications

(14 citation statements)

References 7 publications

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“…Many anode materials other than lead alloys have been tried, but nothing better has been found [119]. Recently, it was revealed that bismuth-doped lead anodes can triple the anodic reoxidation of Cr(III) [120]. Pure iron, such as Armco or electrolytic iron, dissolves less when used as an anode than steel, nickel, stainless steel, or similar alloys.…”

Section: Anodesmentioning

confidence: 99%

Electrodeposition of Chromium

Mandich¹,

Snyder²

2010

Modern Electroplating

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Electroplated chromium deposits rank among the most important plated metals and are used almost exclusively as the final deposit on parts. Without the physical properties offered by electroplated chromium deposits, the service life of most parts would be much shorter due to wear, corrosion, and the like. Parts would have to be replaced or repaired more frequently, or they would have to be made from more expensive materials, thus wasting valuable resources.The thickness of electroplated chromium deposits falls into two classifications: decorative and functional. Decorative deposits are usually under 0.80 mm in thickness. They offer a pleasing, reflective appearance while also providing corrosion resistance, lubricity, and durability. Decorative chromium deposits are typically plated over nickel but are occasionally plated directly over the substrate of the part.Functional ''hard chrome'' deposits have a thickness customarily greater than 0.80 mm and are used for industrial, not decorative, applications. In contrast to decorative deposits, functional chromium is usually plated directly on the substrate and only occasionally over other electrodeposits, such as nickel. Industrial coatings take advantage of the special properties of chromium, including resistance to heat, hardness, wear, corrosion, and erosion, and a low coefficient of friction. Even though it has nothing to do with performance, many users want their functional chromium deposits also to be decorative in appearance. Functional deposits are also used on parts such as cutting tools and strip steel and are even thinner than decorative deposits.The most common and oldest commercial type of chromium process utilizes hexavalent chromium (Cr 6 þ ) in an aqueous solution containing one or more catalysts. The

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Section: Anodesmentioning

confidence: 99%

Electrodeposition of Chromium

Mandich¹,

Snyder²

2010

Modern Electroplating

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“…OH Å was produced in a Fenton reaction by incubating for 60 min at 37°C in the presence of 1.0 mmol/L Fe 2+ , 2.0 mmol/L H 2 O 2 , 1.0 mmol/L EDTA, 1.0 mmol/L sodium salicylate, 20 mmol/L NaH 2 PO 4 -Na 2 HPO 4 buffer, pH 7.4, and different concentrations of test material (10,20, and 40 mg/ml, respectively) in a final volume of 5 ml. Solutions of Fe 2+ , H 2 O 2 and Fe 2+ were made up immediately before use in deaerated water and the iron salt was mixed with the EDTA before addition.…”

Section: Fenton Reaction Conditionmentioning

confidence: 99%

“…Therefore, the proper choice of a suitable electrode for this purpose is very important. There is a great interest in the development of PbO 2 and doped PbO 2 as anode electrode with high electro-catalytic activity for anodic oxygen transfer processes [7][8][9][10]. A general mechanism was proposed by Johnson and co-workers [11][12][13] for anodic oxygen transfer electro-catalysis at PbO 2 and doped PbO 2 electrodes with differential voltammetry.…”

Section: Introductionmentioning

confidence: 99%

Study on production of free hydroxyl radical and its reaction with salicylic acid at lead dioxide electrode

Wang

et al. 2005

Journal of Electroanalytical Chemistry

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“…8, 9, 12, and 13, were solved analytically using a combination of elimination of variable method and numerical integration. 18,19 The rate of accumulation of the ionic species can be rewritten as a fourth order differential equation and the corresponding solution is expressed as a function of time. The values of the constant of integration and the exponents were determined by the initial and boundary conditions.…”

Section: Mathematical Modelmentioning

confidence: 99%

“…Estimated values of the heterogeneous rate constants as described in the mathematical model. Values of reaction rate constants predicted by Mondal et al18 …”

mentioning

confidence: 97%

Iron Removal and Simultaneous Regeneration of Hexavalent Chromium in Spent Plating Solutions

Jegadeesan

Mondal

Lalvani

2005

J. Electrochem. Soc.

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This study focuses on the removal of metallic impurities such as Fe͑II͒, Fe͑III͒, and Cr͑III͒ from spent plating solutions via electrolytic separation. A two-chamber electrolytic cell separated by a ceramic membrane was used. The choice of the catholyte affected the removal rate of iron. As compared to chromic acid, sodium monophosphate was found to provide the maximum removal rates for iron ͑5.89 mM h Ϫ1 ͒. The main modes of mass transfer across the ceramic membrane were diffusion driven by concentration gradient and cation migration. Subsequent removal of the impurity from the cathode compartment was achieved via electrodeposition and precipitation as sludge. The iron removal increased 69% when the applied potential was increased from 5 to 7.5 V, while an increase in temperature from 45 to 55°C resulted in a 33% decrease in impurity removal. In addition, regeneration of Cr͑VI͒ occurred simultaneously due to the anodic oxidation of Cr͑III͒. The rate of regeneration was found to depend on the applied potential and the concentration of the Cr͑III͒ species in the anode chamber. A mathematical model describing the process was developed and validated. Modeling results indicate that a greater iron removal could be obtained if the impurities transported to the catholyte are deposited or precipitated at a faster rate. The estimated mobilities, diffusivities are in good agreement with those reported in the literature.Hexavalent ͑hard͒ chromium plating solutions consist of chromate anions (Cr x O y 2Ϫ ) as a source of chromium. During electrodeposition, the electrolyte is contaminated with metallic impurities such as trivalent chromium ͓Cr͑III͔͒, iron ͓Fe͑II͒ and Fe͑III͔͒, nickel ͓Ni͑II͔͒, and copper ͓Cu͑II͔͒ due to the incomplete reduction of polychromates and reverse etching of the metal substrates into the corrosive chromic acid solution. 1 Depending upon the concentration, the impurities in chromium plating baths affect the efficiency of the plating process and the quality of deposits produced. 2,3 Despite its high chromate content, the electrolyte needs to be discarded or processed to recover the metal impurities usually by high cost smelting operations. It is, therefore, desirable to regenerate the waste chromium liquors by continuously removing the impurities from the plating baths.The most commonly used regeneration technique is electrolytic separation. In this process, a two-compartment electrolytic cell divided by a cation exchange or a porous ceramic membrane for the separation of the purified and contaminated solution is used. 4 Upon the application of electric voltage across the electrodes, metal cations in the contaminated solution migrate from the anode to the cathode compartment through the porous membrane where they are concentrated. Subsequent precipitation as sludge or electrodeposition occurs in the cathode compartment depending on the applied potential and the pH of the catholyte. This technique is known to simultaneously remove contaminants such as Cu͑II͒, Ni͑II͒, and Fe͑III͒, and oxidize Cr͑III͒ to ...

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Untitled

Cited by 13 publications

References 7 publications

Electrodeposition of Chromium

Electrodeposition of Chromium

Study on production of free hydroxyl radical and its reaction with salicylic acid at lead dioxide electrode

Iron Removal and Simultaneous Regeneration of Hexavalent Chromium in Spent Plating Solutions

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