Treatment and Recovery of Chrome from Electroplating Wastewater (By Chemical Precipitation) ( At Homicho Ammunition Engineering Industry)
No Thumbnail Available
Date
2016-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
the reduction process of hexavalent chromium from electroplating wastewater by
chemical precipitation in order to achieve the maximum trivalent chromium concentration.
Sodium bisulphite is one of the widely used coagulants in waste water treatment process and has
good reducing ability. Because of its reducing capacity, sodium bisulphite is applied to reduce
hexavalent chromium from electroplating wastewater. The study has been conducted in four
phases. In phase one reduction of hexavalent chromium, phase two determination of hexavalent
chromium, phase three precipitation of chromium sulphate followed by oxidation of the sludge
of Chromium (III) hydroxide. Phase one study was carried out to analyze the reduction process
of the toxic soluble hexavalent chromium by using the concept of design experiment to justify
the number of affecting factors and levels during the laboratory work followed by the synthetic
waste sample preparation at Homicho Ammunition Engineering Industry in Ambo.
Different experiments were considered like classical method of analysis to quantify and
qualify the wastewater sample, atomic absorption spectrophotometric technique was utilized to
determine the amount of total chromium, and finally colorimetric method to determine the
amount of hexavalent chromium with a suitable complexing agent to engulf the ionic hexavalent
Chromium. The total numbers of experiments were fifty four (54), the first twenty seven (27) run
was analyzed by labeling the distributed parameters in each beaker of the solution and the
number of factors with their levels were indicated. For the purpose of optimization of the
selected parameters experiments were replicated, then at the second round of the experiment run
number 44 was the optimized one. In order to perform these activities, the concentration of the
stock solution was 100 mg/L, and 50 ml of volume was taken to each 500 ml beaker volume with
concentration of 10 mg/L. With this amount phase two was conducted, to solidify the solution
containing chromium sulphate Cr2 (SO4)3 generated from the redox reaction. . The required
reduction time to reach equilibrium, the effectiveness of pH value for Cr (VI) reduction and the
required amount of sodium bisulphite to complete reduction were investigated. The redox
reaction was completed within 40 minutes, at pH of 2 and 50 mg/L of hexavalent chromium was
reacted with 200 mg/L of sodium bisulphite in deionized water.
Sodium hydroxide was used to precipitate the solution after the reaction of the precipitating
agent and hexavalent chromium. In Final phase oxidation of Chromium (III) hydroxide to
hexavalent chromium was carried out;
Key words: Cr (VI) reduction, Sodium bisulphite, wastewater treatment
Description
Keywords
Cr (VI) Reduction, Sodium Bisulphite, Wastewater Treatment