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UBC Theses and Dissertations

Effect of radiation exposure on industrial flocculants and their performance Sulakh, Hiten


The effect of radiation exposure on four industrial flocculants under various physicochemical conditions, such as pH, ionic strength, flocculant concentration and number of CT exposures, was investigated by determining intrinsic viscosities from viscosity measurements on dilute flocculant solutions. Huggins equation was used for non-ionic flocculants and Fedors equation was used for anionic flocculants to evaluate the raw viscosity data through which intrinsic viscosity was calculated. The results indicated that the flocculants take a fully-extended conformation in distilled water at natural pH and 25°C and under no-exposure condition as seen from high intrinsic viscosity values. Exposing the dilute flocculant solution to x-rays resulted in decreases in the reduced and, in turn, the intrinsic viscosity. This effect can be attributed to the polymer degradation caused by the energy imparted by x-ray radiation. At a constant ionic strength of 0.01M NaCl, negatively charged carboxylate groups are shielded by the counterions from the salt, and the flocculant polymer assumes a coiled conformation, posing a smaller target for the x-rays. Similar intrinsic viscosities were observed under acidic conditions (pH ~3) as under dilute salt conditions, and thus the effects of x-rays were insignificant for a non-ionic flocculant and a marginal decrease in intrinsic viscosities was observed for anionic flocculants. Flocculation performance before and after exposure was also tested. These tests were conducted to validate the findings from intrinsic viscosity measurements and to assess if changes in intrinsic viscosity related to changes in flocculation performance. It was found that flocculation of model quartz suspension using a CT-exposed flocculant resulted in a lower settling rate of the flocs compared to flocculation using a fresh non-exposed polymer. This indicates the polymer breakage due to radiation exposure results in shorter polymer chain length and decreased flocculation performance.

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