Comparative analysis of laboratory-scale chromium removal using zero-valent iron and sodium metabisulfite via response surface methodology for the treatment of a local chrome-tannery wastewater

Date

3-2010

Degree

Bachelor of Science in Agricultural Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Veronica P. Migo

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Abstract

Two treatment model systems were established that includes reduction process and precipitation process. Na2S2O5 and Fe0 were employed as reducing agents while sodium hydroxide was used as the precipitating agent. In the reduction process, pH, reaction time and dose of reducing agent were optimized using the response surface methodology, specifically, the Box-Behnken optimization. In the precipitation process, one-factor response surface methodology and regression analysis were used. Synthetic wastewater of 350 ppm Cr(VI) was used in the experiment. Hexavalent chromium was quantified using 1,5-diphenylcarbazide colorimetric method, in which absorbance was measured at 540 nm. Total chromium was quantified using flame atomic absorption spectroscopy (FAAS), in which absorbance was measured at 357.9 nm. In the reduction process using Na2S2O5 the optimum conditions were determined to be at pH 2.5, 30 minutes reaction time and 62.5 g/L dose while in using Fe0 the optimum conditions were pH 1.75, 60 minutes reaction time and 25 g/L dose. In the precipitation process, from reduction using Na2S2O5, the optimum pH and reaction time were determined to be at 10.96 and 40 minutes, respectively. While from the reduction using Fe0, the optimum pH and reaction time were 8.86 and 40 minutes, respectively. Analyzing for the cost, the combined reduction- precipitation treatment process of synthetic wastewater with 350 ppm chromium content using sodium metabisulfite is 19,476.71 Php, while for zero-valent iron is 18,226.71 Php. Based on the optimum conditions and practical considerations, the use of zero-valent iron is the better treatment model system. Treatment processes of local chrome-tannery effluents can then be optimized based on the results from the use of synthetic wastewater.

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2010 A13 M346

Document Type

Thesis

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