Removal of chromate ion from aqueous solutions by sponge iron

Abstract

A B S T R A C THexavalent chromium ion is the most toxic form of chromium ions and it is considered as a hazardous pollutant. So removing this ion from effluents is very important. One possible approach is reducing Cr(VI) to Cr(III) by metallic iron. Sponge iron was used in this study, and the influence of parameters such as the amount of sponge iron in the solution, effect of acid washing of sponge iron, initial pH and temperature of the reaction on the efficiency of the reduction process were investigated. The possibility of reusing and regenerating of used sponge iron was also studied. Furthermore, the effect of sodium tartrate was investigated. This compound eliminates the precipitates of Cr(III), Fe(III) hydroxides, and Cr x Fe 1 À x (OH) 3 and thus reduces surface passivation of sponge iron. X-ray diffraction analysis and scanning electron microscopy images were employed to investigate the chemical composition and surface morphology of the sponge iron before and after the treatment. The results revealed that acid cleaning of the sponge iron, decreasing the solution pH, increasing the temperature and adding sodium tartrate to the solution improve the Cr(VI) removal efficiency. Furthermore, it was found that the used sponge iron can be reused after acid washing.

Green walnut shell as a new material for removal of Cr(VI) ions from aqueous solutions

“…Cr(VI) [18]) include chemical precipitation and filtration [2], chemical oxidation or reduction [19,20], electrochemical treatment [21], reverse osmosis [10], solvent extraction [22], adsorption [23,24], and ion exchange [25]. These processes have several disadvantages including high operational cost, incomplete removal, low selectivity, high energy consumption, and generation of a large amount of toxic sludge to be disposed of [26,27].…”

Experimental study of a two‐stage thermochemical cycle for hydrogen production

“…This is an exceedingly high value compared to the specific surface area of sponge iron obtained by conventional processes, for which a typical value of 1 m 2 /g of DRI has been reported for Schutze 55 . In a study on the removal of the chromate ion from aqueous solutions, two different DRIs, which had a surface area of 0.769 and 0.924 m 2 /g, were used successfully as catalysts 56 …”

“…55 In a study on the removal of the chromate ion from aqueous solutions, two different DRIs, which had a surface area of 0.769 and 0.924 m 2 /g, were used successfully as catalysts. 56 A study on the effect of adding biomass to iron ore pellets before burning which was subsequently reduced by hydrogen showed that the addition of 2% of biomass causes the surface area of the obtained DRI to increase from 6.03 m 2 /g without addition to 16.26 m 2 /g after the addition, and the presence of iron whiskers in the DRI was noticed. 57 Thus, it is clear that the large surface area obtained in the present work is due to the formation of iron whiskers during the reduction process.…”

Adsorption Kinetics of Cupric Ions on Mixture of Modified Corn Stalk and Modified Tomato Waste

“…It may be found as a dangerous contaminant in food, especially shellfish, liver, mushrooms, nuts and chocolate [7] [8] [9]. There are different methods for the removal of heavy metals including chemical precipitation, reverse osmosis, ion exchange, and coagulation [1] [10] [11]. However, the application of such methods is limited due to some reasons such as incomplete metal removal, energyintensive, economically expensive, and generation of secondary waste products [12] [13].…”