Lab-scale removal and selective recovery of cadmium (Cd2+), chromium (Cr6+) and lead (Pb2+) from synthetic wastewater

Date

4-2006

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Veronica P. Migo

Abstract

SUYOM, REYNAN FIEL G. University of the Philippines Los Banos, April 2006. Lab-scale Removal and Selective Recovery of Cadmium (Cd+2), Chromium (Cr+6) and Lead (Pb+2) from Synthetic Wastewater

Adviser: Dr. Veronica P, Migo

Hydrogen sulfide precipitation is a technology employed in the remediation of heavy metal-contaminated systems, the extent of which is determined by temperature, concentration of reactants and pH. In this study, the effect of pH on the efficiency of 142S precipitation for Cd, Cr and Pb, to simultaneously and sequentially precipitate these metals was investigated. Cd precipitates as the yellow CdS, Pb as black PbS and Cr as the green trivalent chromium hydroxide. The aim is to remove the metals or decrease their concentrations to the allowable limits set by the DENR before they are disposed to water bodies.

The pH of maximum precipitation for each metal solutions was studied from pH 0.05 to pH 13.00. The pH ranges for maximum precipitation of lead are: pH 8.00 to pH 2.00 and pH 13.00 to pH 12.00: cadmium has maximum precipitation at pH 3.00 to pH 2.65; and chromium has a maximum precipitation at pH range of pH 7.00 — pH 7.34. The final metal concentrations after hydrogen sulfide precipitation for Pb (0.00 ug/mL), Cr (0.17 ag/mL) and Cd (0.05 ug/mL) are within the limits set by the DENR for waste water effluents.

The pH values for the maximum precipitation of Cd, Cr and Pb in a single metal system are not applicable for the efficient selective precipitation of two-metal system. For Cd — Cr system. precipitation at pH 2.00 resulted in the 100.00% precipitation of Cd and 7.32% of Cr. For the Pb — Cd system, Pb can be selectively precipitated out first at pH 0.50. with a percent precipitation of 89.31%, with 25.83% of cadmium co-precipitating with it. The p11 of the solution can be adjusted to 1.00 followed by hydrogen sulfide precipitation to precipitate the remaining heavy metals. For Cr— Pb system. lead can be precipitated first at pH 1.00.Lead has a percent precipitation of 99.70% with 36.25% of chromium precipitating with it.

Lead may be precipitated out of a three-metal system at pH 13.00, with a percent precipitation of 99.96%. However at this pH. 60.00% of Cd and 28.20% of Cr co-precipitate with lead. The final concentrations after precipitation are: 6.00 ag/mL Cd, 59.25 ug/mL Cr and 0.02 ug/mL Pb.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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