Monitoring Tools and Strategies for Effective Electrokinetic Nanoparticle Treatment

Abstract

Nanoparticles are increasingly being used by industry to enhance the outcomes of various chemical processes. In many cases, these processes involve over-dosages that compensate for particle losses. At best, these unique waste streams end up in landfills. This circumstance is inefficient and coupled with uncertain impacts on the environment. Pozzolanic nanoparticle treatments have been found to provide remarkable benefits for strength restoration and the mitigation of durability problems in ordinary Portland cement and concrete. These treatments have been accompanied by significant particle losses stemming from over-dosages and instability of the colloidal suspensions that are used to deliver these materials into the pore structure. In this study, new methods involving simple tools have been developed to monitor and sustain suspension stability. Turbidity measurement was introduced to monitor the progress of electrokinetic nanoparticle treatment. This tool made it possible to amend a given dosing strategy in real time while it remains possible to make effective treatment adjustments. By monitoring the particle stability and using pH and electric field controls to avoid suspension collapse, successful electrokinetic treatment dosage strategies were demonstrated using 20 nm NALCO 1056 alumina-coated silica particles. These trials indicated that turbidity measurements could track the visually imperceptible phenomena of particle flocking early on at the inception of its development. Suspensions of these nanoparticles were successfully delivered into 5 cm diameter by 10 cm tall hardended cement paste (HCP) specimens by monitoring fluid turbidity along with the specific gravity and using these values to guide the active management of the treatment dosage and pH. Under this new strategy, these losses were reduced to 5% as compared to the 80% losses associated with other treatment approaches. The relationship between the turbidity and the specific gravity was found to be linear. These plots indicated regions of turbidity and specific gravity that were associated with particle flocking. The tools, guidelines, and strategies developed in this work made it possible to manage efficient (low-particle-loss) electrokinetic nanoparticle treatments by signaling in real time when adjustments to electric field, pH, and particle dosage increments were needed.