The invention provides a method for treating
silicon in
waste oil sand which is generated in a
silicon ingot cutting process. The method comprises the following steps of: washing the
waste oil sand in alkali liquor for a certain period of time in a countercurrent mode to dissolve
silicon powder, a small amount of iron,
copper and residual
polyethylene glycol (PEG) in the
waste oil sand; separating the mixture to obtain waste oil sand
solid and liquid which is obtained after washing; adding alkali into the liquid which is obtained after washing till the solution reaches a certain concentration; washing the waste oil sand once again; repeating the steps of adding the alkali and washing the waste oil sand for several times; washing the waste oil sand by using pure water; separating to obtain
silicon carbide (SiC)
solid and liquid which is obtained after washing;
drying the SiC, and recycling; adding the alkali into the liquid which is obtained after washing to obtain a washing solution for washing other waste oil sand; and when the concentration of the silicon in the liquid which is obtained after washing reaches the needed concentration, collecting, and thus obtaining silica
sol. In the whole treatment process, materials are recycled in a closed mode, and the method is
pollution-free, environment-friendly (waste water cannot be generated and discharged), low in consumption and economic. By the method, the defects of complex process flows, low efficiency,
high energy consumption, long treatment cycle, severe environmental
pollution and the like which commonly exist in the prior art of recycling the silicon are overcome, and the problems of the accumulation of waste residues and environmental
pollution in industries are solved effectively.