Alkali precipitation of gold smelting wastewater and cement-based solidification/ stabilization of its wet copper sludge using rice hull ash as admixture

Date

10-2009

Degree

Bachelor of Science in Chemical Engineering

College

College of Engineering and Agro-Industrial Technology (CEAT)

Adviser/Committee Chair

John Meynard M. Tengco

Co-adviser

Veronica P. Migo

Committee Member

Monet Conception C. Maguyon, Marilyn C. Del Barrio

Abstract

An evaluation of the feasibility of alkali precipitation for the removal of heavy metals, with copper as primary consideration, from gold smelting wastewater was performed. The removal efficiencies and final dissolved concentrations of copper, and heavy metals, in the effluent were used as performance indicators. The optimum pH to which the heavy metals can be simultaneously precipitated, with copper as the main concern, is obtained. Also, the use of solidification/stabilization technology to the sludge formed from alkali precipitation was evaluated. The effects of varying the proportions of ordinary Portland cement, rice hull ash, and wet sludge on the unconfined compressive strength, durability, and leachability properties of the blocks were evaluated. Results of alkali precipitations showed that the optimum pH for copper and other heavy metals removal is at pH11.5 where copper, lead, and chromium removal efficiencies are found to be 99.998%, 99.763%, and88.593%, respectively. At the optimum pH, the final dissolved concentrations of the metals are 0.18ppm, 0.47ppm, and 1.07ppm for copper, lead, and chromium , respectively. Copper and lead final dissolved concentrations fell within DENR standards, while that of chromium did not. The alkali dose at the optimum pH is 9.583g NaOH per liter of wastewater. The amount of sludge produced is 11.88g dried sludge per liter of wastewater.Results for the solidification/stabilization of alkali precipitation sludge showed that all the blocks produced passed the 50psi-standard for unconfined compressive strength. For the durability test only design mix E (1.54:0.23:0.23), F(1.0:0.0:0.0), H, (0.65:0.0.35), and I(0.77:0.11:0.12) the 1ppm standard set by USEPA 40 CFR 141; Japanese legislation and Thai Legislation.

Language

English

Location

UPLB College of Engineering and Agro-Industrial Technology

Call Number

LG 993.5 2009 E62 T36

Document Type

Thesis

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