Novel Treatment Process of Harmful Organic Materials in Waste Water Using Temperature-Sensitive Gel Synthesized from PVA

Abstract

The adsorption removal of harmful organic materials in waste water has been carried out using the adsorption and desorption characteristics of a temperature-sensitive polymer gel which is synthesized from polyvinylalcohol (PVA). A new adsorption removal process using an air lifting type vessel has been designed and examined for practical use. Three types of polymerization degrees (1000, 1700 and 2500) of PVA were used in this experiment. The gel volume in water was induced the volume contraction at around 305 K for 1000, 310 K for 1700 and 320 K for 2500, respectively. At higher temperatures, the temperature-sensitive polymer gel shrinks because of discharging water, whereas, in contrast, at lower temperatures, the gel swells as a result of absorbing water. The reversibility of the volume change of the synthesized polymer gel is confirmed by changing temperature. The adsorption behavior of organic materials onto PVA polymer gels in water was investigated at various temperatures. The amount of adsorption of organic materials increases remarkably at temperatures higher than about 305 K for 1000, 310 K for 1700 and 320 K for 2500. The saturated amounts of adsorption are about 0.05 mmol/g-gel for 1000, 0.26 mmol/g-gel for 1700 and 0.20 mmol/g-gel for 2500, respectively. The organic material in waste water could be adsorbed and desorbed reversibly onto PVA polymer gel by the temperature swing. The mechanism of adsorption and desorption of organic materials onto the gel can be explained by the hydration and dehydration of the polymer gel. The driving force of the adsorption is considered to be the hydrophobic interaction between PVA polymer gel and organic compounds. The novel continuous removal process for organic materials in waste water was designed and discussed for practical use.