Date of Award

2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

John J. Sansalone

Abstract

Urban storm water runoff mobilizes and transports significant loads of heavy metals. Promulgation of NPDES Phase II regulations has spurred development of Best Management Practices (BMPs) for in-situ control of heavy metals. In this study, Amphoteric materials such as manganese oxides and iron oxides on the various substrates including silica sands, polymeric beads and cementitious particles were investigated. Surface characterization results indicated that oxide coatings ranged from 20 to 200-mum in depth, and surface areas were significantly increased by greater than a factor of one thousand compared to uncoated media. Point of zero charge (PZC) for manganese oxide coated media generally ranged from 4 to 6. For manganese oxide coated polymeric media (MOPM), Freundlich type adsorption isotherms were observed, and MOPM has a comparable adsorption capacity for the divalent heavy metals compared to other commercial and research media. For manganese oxide coated cementitious media (MOCM), removal mechanisms proved to be more complicated with a parabolic isotherm results indicating the combination of surface precipitation and surface complexation. A surface complexation model, triple layer model, was utilized to model adsorption of divalent heavy metals for MOPM used as adsorptive media in storm water BMPs. Intrinsic surface acidity constants for MOPM were determined using FITEQL-TLM as log Kinta1 = 3.196 and log Kinta2 = -5.802 and the intrinsic surface reaction constants as log KintPb = -1.91, log KintCu = -2.53 and log KintZn = -4.45. For MOCM, the intrinsic surface complexation constants were log KintPb = -1.84, log KintCu = -4.11, log KintZn = -5.04, and log KintZn = -7.84. Surface complexation on the solid-water interface and precipitation in bulk solution were distinguished from the speciation distribution as a function of pH and it was found that surface complexation was the dominant removal mechanism in the typical storm water pH range. An overall rate kinetic, potential driving model, was developed based on an elementary second order rate law. This model was successfully utilized for the kinetic data of both MOPM and MOM. Based on column experiment performances of all the media and substrates examined in this study, amphoteric oxide coating significantly improved the adsorption capacity, with MOCM demonstrating the greatest adsorptive capacity.

ISBN

9780493563169

Pages

265

DOI

10.31390/gradschool_disstheses.419

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