Abstract: The process comprises isolating phenol and partially formaldehyde wherein molar ratio thereof is from 1:1.4 to 1:3.5 at a pH of from 0.65 to 0.8 in the presence of a vegetable sorbent, such as saw-dust, at the boiling point. The resultant product of reaction of phenol and formaldehyde with components of the sorbent is separated from the liquid phase and used. Methanol is removed from the liquid phase, whereafter residual formaldehyde is isolated therefrom by adding a condensation component selected from phenol and urea and a vegetable sorbent. The process is conducted at 60.degree.-100.degree. C. at a pH of from 0.65 to 10. The resultant product of reaction of the phenolic component, formaldehyde and components of the sorbent is also used.The process enables the purification degree of waste liquors from toxic substances to be as high as 98-99%, and makes it possible to obtain a useful product.