the following description is of the best - contemplated mode of carrying out the invention . this description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense . the scope of the invention is best determined by reference to the appended claims . fig1 is a schematic view showing a flowchart of an embodiment of liquid - phase suspension treatment using a photocatalytic sol . this embodiment employs the method shown in fig1 . as to the method shown in fig1 , for example , it can be operated at an operation temperature between 5 - 50 ° c . first , the sample such as 10 g solid ash is wetted using 10 ml acetone , and is then mixed with excess photocatalytic sol such as 100 ml dilution solution by stirring , thus a liquid - phase suspension is formed . in the liquid - phase suspension , the ratio of the excess sol to ash stands at 9 : 1 by weight . the stirring may be mechanical stirring or stirring by an ultrasonic sieving . subsequently , the liquid - phase suspension is continuously stirred under illumination of a uv — c source for at least six hours , letting the ash particles to be sufficiently exposed to a uv — c source . the treated ash and the excess photocatalytic sol are separated , and the solid sample is then dried . a test is performed on the dried sample to measure the content of dioxins therein . the remaining photocatalytic sol can be recycled by adding fresh photocatalytic sol , thus not only reducing cost of materials but also avoiding water pollution . the content of tio 2 in the photocatalytic sol can be adjusted appropriately between 0 . 01 % and 0 . 1 % by weight . in doing so , the content of tio 2 in the photocatalytic sol can be maintained at an optimal value , and cost of the photocatalytic sol can be reduced , while still having the same or higher photocatalytic degradation efficiency of dioxins . in this embodiment , the tio 2 sol is neutral liquid - phase solution , and the tio 2 therein is an anatase crystalline structure . the particles in the tio 2 sol have a diameter less than 100 nm , preferably , less than 30 nm . table 1 shows that dioxins - containing samples were subjected to a liquid - phase suspension treatment using a photocatalytic sol . as shown in table 1 , the sample a ( ash ) and the sample b ( soil ) subjected to liquid - phase suspension treatment and illumination of a uv source ( e . g . uv - c or uv - a ) have lower concentration ( represented by ng - teq / g ) of dioxins . specifically , the dioxins - containing concentration of the samples subjected to illumination of uv - c is apparently reduced . fig2 is a schematic view showing a flowchart of an embodiment of another treatment using a photocatalytic sol . this embodiment employs the method shown in fig2 . as to the method shown in fig2 , for example , it can be operated at an operation temperature between 5 - 50 ° c . first , the sample such as 10 g solid ash is mixed with excess photocatalytic sol such as 100 ml dilution solution by stirring . the stirring may be mechanical stirring or stirring by an ultrasonic sieving . next , a solid - phase separation process is performed , thus a solid sample is obtained from the mixture . the solid sample is then spread on a sheet to be illuminated by uv - c for at least six hours . to make the solid sample sufficiently illuminated by uv - c , it is stirred every half an hour or an hour . the treated ash is directly subjected to measurement of the content of dioxins without separation of photocatalytic particles . in this embodiment , the tio 2 sol is neutral liquid - phase solution , and the tio 2 therein is an anatase crystalline structure . the particles in the tio 2 sol have a diameter less than 100 nm , preferably , less than 30 nm . table 2 shows that dioxins - containing samples were subjected to the treatment shown in fig2 using a photocatalytic sol . as shown in table 2 , the sample a ( ash ) and the sample b ( soil ) subjected to the treatment shown in fig2 and illumination of uv - c have relatively lower concentration ( represented by ng - teq / g ) of dioxins . according to methods of theses embodiments , nano - scale tio 2 sol serving as photocatalyst is employed to degrade dioxins on surfaces of the soil or ash . that is , by means of mixing and stirring the solid wastes and the tio 2 sol , and performing illumination of a uv source , the dioxins on surfaces of the solid wastes can be decomposed . compared to the conventional treatments , there is no need to undergo high temperature treatments and to use curing agents . alternatively , the methods of theses embodiments can be employed to decompose other organic contaminants on surfaces of the solid wastes at room temperature . while the invention has been described by way of example and in terms of the preferred embodiments , it is to be understood that the invention is not limited to the disclosed embodiments . to the contrary , it is intended to cover various modifications and similar arrangements ( as would be apparent to those skilled in the art ). therefore , the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements .
a method of removing organic contaminants from surfaces of solid wastes is disclosed . the method includes the steps of forming a tio 2 sol ; mixing the solid wastes and the tio 2 sol by stirring . furthermore , the mixture undergoes photo - catalytic remediation under illumination of a uv source prior to a solid - liquid separation process of the illuminated tio 2 sol and solid wastes .