A Technology for Enhanced Control of Erosion, Sediment and Metal Leaching at Disturbed Land Using Polyacrylamide and Magnetite Nanoparticles
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Urbanization and human disturbance of land often result in serious soil erosion and releases of fine sediments and soil-bound toxic metals, which can lead to contamination of downstream water bodies and cause water treatment plant failure. Yet, effective technologies for rapid soil stabilization at disturbed sites have been lacking. The study tested the effectiveness of a commercial soil conditioner, known as polyacrylamide (PAM), in combination with a class of polymer-bridged magnetite nanoparticles for simultaneous control of soil erosion and metal leaching from disturbed sites. A small-scale box-test setup was constructed to test the releases of sediments and soluble metals from two disturbed surface under simulated rainfall conditions. Sandy loam soil from a local quarry mining site and Smith Farm loam soil were used as the model soils. Polymer-bridged magnetite nanoparticles were prepared using PAM or a water soluble starch as bridging agents. Arsenic (V) was used as a model soluble toxic metal. PAM stabilized magnetite nanopartilces (Total Fe=0.1g/L) had significant effects on runoff concentration control (90.8% reductions for Vulcan Site soil, 89.1% reduction for Smith Farm soil) and significant amount of turbidity removal (83.0% reductions for Vulcan Site soil, 90.5% reduction for Smith Farm soil), with 30% reduction of viscosity compared to PAM only. Starch partially stabilized magnetite nanoparticles associated with PAM application successfully immobilized the arsenate in soils (below 8% arsenate is leachable). Vulcan site soil is more vulnerable to runoff but easier to be stabilized by nanoparticles when contaminated than SmithFarm soil. Low pH value (pH: 5.46) and high dosage of Fe nanoparticles (total Fe = 1g) as well as the soil texture presents better removal efficiency for arsenate immobilization. Batch adsorption test and immobilization kinetics test reinforced the above findings. Key words: Arsenate immobilization; Magnetite nanoparticles; Polyacrylamide (PAM); Runoff; Sediment; Soil erosion; Water pollution control.
- Thesis_Min Zheng_2011.pdf