Removal of Toxic Hexavalent Chromium from Wastewater by Activated Carbon Generated from Liming Pelt Trimming with Tannin
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Hexavalent Chromium
Trimming
Tannin
Carbon fibers
Simultaneous Determination and Selective Determination of Trivalent Chromium and Hexavalent Chromium
In this paper,simultaneous determination and selective determination of trivalent chromium and hexavalent chromium were reviewed,the advantages and disadvantages of different measurement methods were analyzed,which had important significance for the research of trivalent chromium and hexavalent chromium.
Hexavalent Chromium
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The preparation of activated carbon containing basic surface radical with oxidant and at under high temperature is introduced. The ion exchange capacity of modified activated carbon are determined. The effects of chemical factors such as pH and concentration of hexavalent chromium are investigated. The removal mechanism of hexavalent chromium by modified activated carbon is discussed.
Hexavalent Chromium
Carbon fibers
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Hexavalent Chromium
Chromium Compounds
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Abstract Purpose Practically all salmon fillets produced in Norway are trimmed clean of unwanted fat, bone remnants and other defects according to customer requirements. In today's modern salmon-processing plants, the trimming operation is performed by a combination of automated trimming machines and manual post-trimming. Manual post-trimming is necessary due to the inability of current trimming machines to obtain satisfactory trimming. The purpose of this paper is to describe the work done so far toward a robotic post-trimming of salmon fillets. Design/methodology/approach A prototype concept system was developed to explore the possibility of robotic post-trimming. The concept is based on 3D machine vision, a high-speed robot manipulator and a flexible light-weight cutting knife. Findings The developed prototype demonstrated the feasibility of detecting a pre-defined object to be trimmed in 3D, and performing the specified trimming cut along a 3D cutting trajectory. Research limitations/implications The developed prototype system was built and integrated – focusing so far only on a single trimming operation: the tail cut. Originality/value The originality in the paper is the description of a prototype integrated system, focused on robotic post-trimming of salmon fillets. The value is in providing a starting point for further development toward a complete robotic post-trimming of salmon fillets.
Trimming
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Basic chromium sulphate is the most versatile and common tanning agent in the leather industry. Under certain circumstances, the oxidation of the trivalent chromium salts into the hexavalent compounds, which are used in leather manufacture, is a crucial issue. In this study, different proportions of basic chromium sulphate were used in tanning and re-tanning processes according to a commonly used recipe, and levels of chromium oxide and hexavalent chromium were studied stratigraphically in the cross-section of the leather. It was observed that the levels of chromium oxide and hexavalent chromium in the skins increased in relation to the proportions of basic chromium sulphate used in the process, and that the amounts added in the tanning process had a greater effect on the levels of hexavalent chromium formed in the layers of the skins than did the amounts added in re-tanning.
Hexavalent Chromium
Chromium oxide
Chromium Compounds
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This paper established the simultaneous determination of trivalent chromium and hexavalent chromium in leather extract by ion chromatographic analysis method. Using IonPac CS5A chromatographic column can finishing two valent chromiums analysis in 8 min. Trivalent chromium and hexavalent chromium were chelated respectively by PDCA and DPC, and were detected respectively in ultraviolet and visible wavelength by UV-Vis detector. The possible presence of dyes and organic pollutants in leather extract were pretreated by On Guard RP column. The detection limit of trivalent chromium and hexavalent chromium were 31.0 μg/L and 0.41 μg/L respectively. This method is of high sensitivity, low disturbance, hign accuracy and efficiency.
Hexavalent Chromium
Ion chromatography
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Hexavalent Chromium
Chromium Compounds
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The adsorption behavior of chromium(III, VI) onto activated carbon (AC, Merck Co. Ltd.) and oxine-impregnated activated carbon (AC(HOx)) was investigated by use of a column method. The adsorption of chromium(III, VI) onto activated carbon, and of chromium(VI) onto AC(HOx) showed remarkable pH-dependency. The optimum pH for the adsorption of chromium(VI) from 1.00 × 10-3 mol dm-3 chromium(VI) solution were about 2.5 for activated carbon and about 3.0 for AC(HOx). The amount of chromium(VI) adsorbed onto adsorbents at the optimum pH was 13.5 mg for 5.0 g of activated carbon and 22.0 mg for 5.0 g of activated carbon impregnated with 0.5 g of oxine. Chromium (VI) adsorbed onto activated carbon at pH 4.9 was completely desorbed with 0.10 mol dm-3 NaOH solution in the form of chromium(III) (33%) and chromium(VI) (67%). While less than 6% of the total chromium(VI) adsorbed onto AC(HOx) at pH 4.9 was desorbed with 0.10 mol dm-3 NaOH solution. It seems probable that the chromium(VI) which was adsorbed onto activated carbon in the forms of Cr(OH)(H2O)52+ appeared from the reduction of some portion of chromium(VI) with activated carbon, HCrO4- and Cr2O7-2. On the other hand, chromium(VI) may be adsorbed onto AC(HOx) mainly in the form of Cr(III)-oxine complex.
Carbon fibers
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Hexavalent chromium is a highly toxic heavy metal.In order to explore the adsorptive behavior of carbonaceous materials for hexavalent chromium in aqueous solution,as the first attempt,activated carbons were modified by Mn2+ with different concentrations.Contrast experiments were conducted using original activated carbon and modified activated carbon at different conditions such as pH,temperature,dosages and initial concentrations.The results showed that the activated carbon modified with Mn2+ solution could improve Cr(VI) adsorptive capacity at same conditions,the factors such as pH,temperature,dosage and the initial concentrations affected the Cr(VI) removal rates.The adsorption isotherms of activated carbon to Cr(VI) had better linear correlation with the Langmuir model.
Hexavalent Chromium
Langmuir adsorption model
Carbon fibers
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Abstract Trimming is the removal of excess metal from a stamped part to allow the part to reach the finished stage or to prepare it for subsequent operations. This article presents an analysis of parts to be trimmed and describes the selection criteria for the different types of trimming dies such as conventional trimming dies and cam trimming dies. It provides information on rough and finish trimming and construction details of trimming dies. The article reviews the selection criteria of presses for a trimming operation. It provides a discussion on the scrap and material handling processes in trimming.
Trimming
Scrap
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