Semester

Fall

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Xinchao Wei

Abstract

The present study includes two parts: (1) Acid mine drainage (AMD) sludge, a waste product from coal mine water treatment, was used as an adsorbent to develop a cost-effective treatment approach to phosphorus removal from municipal secondary effluents. (2) Synthesized nano-magnetite was used as an adsorbent to develop an innovative technology for selenium removal from aqueous solutions. Each case involved a series of batch adsorption experiments conducted to evaluate adsorption kinetics, isotherms, and adsorptive thermodynamics. The effects of pH, temperature, concentration, contact time, and competing anions on the concerned pollutant removal were examined as well.;Adsorption of phosphorus onto AMD sludge particles followed the Freundlich isotherm model with an adsorption capacity ranging from 10 mg/g to 32 mg/g when the final effluent concentration increased from 0.2 mg-P/L to 13.6 mg-P/L. Increase in temperature and neutral/acidic pH favored P adsorption. Three types of water (synthetic wastewater, river water, and municipal secondary effluent) used in a continuous stirred tank reactor (CSTR) setting showed that P adsorption by AMD sludge was relatively independent of the presence of other ionic species. In treating municipal secondary effluent, phosphorus removal efficiency in excess of 98% was obtained. Results of this study indicated that it was very promising to utilize AMD sludge for phosphorus removal from secondary effluents and may be relevant to future efforts focused on the control of eutrophication in surface waters.;Selenite adsorption onto nano-magnetite was observed within 30 min and low pH (i.e., 3.0--5.0) favored the mechanism. Thermodynamic calculations indicated the spontaneity of the process and its endothermic nature. At an initial selenite concentration of 100 microg-Se/L, more than 95% removal was achieved; resulting in an effluent concentration less than 5 microg-Se/L with an adsorption capacity of ∼1 mg/g. Adsorption isotherm study indicated that the adsorption of selenite onto nano-magnetite followed the Freundlich model. Adsorption kinetics was well characterized by a pseudo-second-order model. It was observed that the presence of sulfate did not significantly affect the adsorption mechanism. In conclusion, it was found that nano-magnetite was a promising low-cost adsorbent to treat aqueous solutions containing low levels (50 to 500 microg/L) of selenium.

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