Characterization and treatment of chromium-containing wastes generated from analytical and environmental chemistry laboratory of the Institute of Chemistry, UPLB.

Date

10-2009

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Josefina L. Solivas

Co-adviser

Conrado P. Monterola

Abstract

Methods such as pH adjustment and hydrogen sulfide for the precipitation of chromium metal were employed in this study. Two different chromium-containing wastewater samples were collected from Chemistry 32 and Chemistry 133 Laboratories of the Institute of Chemistry. Characterization was done based on the following parameters: pH, hexavalent chromium concentration using colorimetric methods and total chromium concentration using flame atomic absorption spectrophotometric analysis. Treatment of the wastewater samples involved hydrogen sulfide precipitation for Chemistry 32 wastewater while precipitation by pH adjustment for Chemistry 133. The two wastewater samples had a pi! of 1.15 and -0.73.The optimum pH of precipitation of chromium metal was also determined for each wastewater sample in which three replicates were performed. The aim is to precipitate the chromium metal and lower the concentration to the allowable limits set by the DENR before discharge to our water system. For Chemistry 32 wastewater sample, the pH of maximum precipitation was pH 7.0. After precipitation, the solution resulted to have a 7.26 pg Cr" /mL and 6.60 pg total Cr mL corresponding to 91.04 % and 92.73 % precipitation respectively. Upon comparison with pH 8.0 which was not precipitated by hydrogen sulfide, the concentration obtained was 7.26 ug Cr"/ mL (91.04 (%) and 5.97 ug total Cr/mL (93.44 %) indicating that p11 adjustment alone for Chemistry 32 wastewater was enough to decrease the concentration (Cr"and total Cr) and precipitate chromium metal. Treatment of Chemistry 133 wastewater by pH adjustment showed that after precipitation, it contained 5.87 ug Cr' /mL and 2.26 ug total Cr/mL resulting to 90.74 % and 99.56 % precipitation. The optimum pH of precipitation was found to be at pH 7.0 for both chromium species. The statistically precise data gathered from the study using the Pearson correlation for not normally distributed data and Spearman correlation for nomialle distributed data showed that there was a strong correlation between the pH and the concentration of both chromium species (Cr6+ and total Cr) in the solution for both wastewater samples. As the pH of the solution increases, the concentration decreases within the limits set by the DENR for wastewater effluents. This could be accounted to the basicity of the solution where hydroxide ions facilitate the precipitation of the metal.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2009 C4 G88

Document Type

Thesis

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