Award Date

August 2015

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Civil and Environmental Engineering

First Committee Member

Jacimaria Batista

Second Committee Member

Daniel Gerrity

Third Committee Member

Dave James

Fourth Committee Member

Spencer Steinberg

Number of Pages

127

Abstract

The use of cerium chloride (CeCl3) to remove fluoride and phosphate from waters is addressed in this study. High concentrations of fluoride exist in groundwater especially in developing countries. Consumption drinking water containing high levels of fluoride can lead to serious cases of dental and skeletal fluorosis. Current defluoridation technologies are limited, especially for high levels of fluoride, and are expensive. Industrial wastewaters contribute to the highest fluoride contamination in the world. With the increasing production of electronic materials, the global fluoride concentration and fluoride-contaminated waters have grown tremendously. Excessive discharge of phosphate into the environment promotes eutrophication of lakes and rivers. The major sources of phosphate pollution are agricultural and urban runoff and domestic wastewater discharges. Cerium chloride, a newly available coagulant is expected to remove both fluoride and phosphate from waters A commercially available cerium chloride e (i.e. Sorbx-100) which is a non-hazardous rare-earth salt solution developed for faster coagulation and flocculation of phosphate in wastewater has been recently made available(Molycorp Minerals Incorporated, n.d.). The objectives of this research are to determine the efficiency efficacy of cerium chloride in removing fluoride and phosphate from waters. Batch jar testing was performed to evaluate fluoride removal under different conditions. Column testing was used to test the phosphate removal efficiency of various media impregnated with cerium chloride Batch tests were used to support central composite design (CCD) model to evaluate the impact of major parameters (e.g. fluoride concentration, pH, and cerium dose) on the removal of fluoride from industrial wastewater. In addition, batch tests were also used to investigate the interference of competing ions on the removal of fluoride using cerium chloride.

The CCD model achieved an R-squared = 0.8615 and adjusted R-squared = 0.7368. The model was deemed to be statistically significant. The results showed that the highest removal (> 90%) was achieved at pH of 4.75 at cerium dose of 25 mM, regardless fluoride concentration. The results revealed that sulfate and phosphate have a positive impact on fluoride removal. Bicarbonate was shown to have as a negative impact on fluoride removal. For an actual industrial wastewater containing fluoride and with high alkalinity, no fluoride removal was observed with addition of cerium chloride. The observed fluoride removals can be attributed to two mechanisms: direction precipitation of cerium fluoride, and adsorption of fluoride ions and fluoride complexes onto the surfaces of cerium hydroxides and/or cerium carbonate. Impregnation of various filter media with cerium chloride and using various techniques was proven unsuccessful for phosphate (PO4-3-P) removal. Analysis of the cerium on the column effluent samples showed cerium leaching out of the media. Therefore, all methods for preparing impregnated media were ineffective.

Keywords

cerium chloride; coagulation; fluoride; industrial wastewater; phosphate

Disciplines

Civil Engineering | Engineering | Environmental Engineering

Language

English


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