Research Of Factors Affecting The Stability Of Nano Titanium Dioxide In Natural Waterbodies

Nanomaterials have been widely used in many aspects of human daily life aswell as in the industrial and agricultural productions, along with a greatdevelopment potential. Nano titanium dioxide is one of the typical, most widelyused nanomaterials. In case a large amount of nano titanium dioxide is releasedinto the environment, it may put significant hazards on the environment and humanhealth. The purpose of this paper is to study the stability of nano titanium dioxidein the natural waters, in order to provide a theoretical basis for the risk assessment,treatment and disposal of nanoaterialsBy measuring the sedmentation, agglomeration behavior and the changes ofzeta potential, we evaluated the stability of nano titanium in three different waterbodies. Meanwhile we considered the impacts of concentration, temperature,ultrasound and turbulence on the stability of nano titanium dioxide in waterenvironment. The results can provide basic data to demonstrate the environmentbehavior of nano titanium dioxide.The effect of turbulence on the stability of nano titanium dioxide showed that,the concentration of nano titanium dioxide in the waters increased with theincrease of rotation speeds within a fixed time period (7h). When the speeds goup to about0.32m/s, nano titanium dioxide can completely suspend in bothultrapure water and lake water. While in the seawater, the critical speed to enablenano titanium dioxide suspended completely is about0.34m/s. These results mayhave an important role for simulating the migration and trassformation of nanotitanium dioxide in narural waters.The effect of concentration on the stability of nano titanium dioxide showedthat, the settling rate of nano titanium dioxide in lake and sea water accelerate dwith the increase of its initial concentration. The concentration (100mg/L) ofnano titanium dioxide in sea water decreased more than80%in7h. In ultrapurewater, the absolute value of zeta potential increased with the increases of its initialconcentration, while in lake, it's opposite to the case of ultrapure. The zetapotential of nano titanium dioxide in seawater had a very larger uncertainty. Theinitial concentration has no significantly affect on it.The effect of temperature on the stability of nano titanium dioxide showedthat, improving the temperature of these three waters can increase the particle sizeof nano titanium dioxide, and promote the agglomeration of nanoparticles. Oneexample is, nano titanium dioxide (80mg/L) in35?decreased25%larger than 10?in7h. So, an proper increase in water temperature can promote the settlingand agglomeration behaviors of nano titanium dioxide, thus reducing its stabilityin waters.The impact of ultrasound on the stability of nano titanium dioxide in differentwaters showed that, a nano titanium dioxide (20mg/L) particle with average sizeof1300nm decreased to740nm after ultrasound pretreatment. Ultrasound caninhibit the settling behavior of nanoparticles, decrease the agglomerat ion size, andimprove the absolute value of nano titanium dioxide zeta potential in waters. Suchresults indicate that ultrasound is an effective method to maintain the stability ofnanoparticles in waters, and change the environment behavior of nano titaniumdioxide in actual waters.Overall, by considering all factors on the environment behavior of nanotitanium dioxide in these three tested waters, nano titanium dioxide has the higheststability in ultrapure water, most likely to settling and aggregation in seawater, andthe stability of nano titanium dioxide in lake water falls between these two waters.In addition, increasing water temperature and the dosing concentration of nanotitanium dioxide can reduce the stability of nano titanium dioxide, whereasultrasound and turbulence can enhance the dispersion and stability of nanotitanium dioxide in waters.