The effect of electron irradiation on aqueous dispersions of humic acids and lignin

• Electron irradiation promotes coagulation in aqueous dispersions of lignin and humic acids.
• Maximal effect of coagulation is achieved at absorbed dose 5–15 kGy.
• Negative charge accumulating by absorption of incident electrons results in stabilizing negatively charged micelles.

The effect of irradiation by accelerated electrons on optical absorption of diluted aqueous solutions of lignin and humic acids was studied under two different irradiation conditions: when thickness of irradiated solution layer was less than the electrons range in the solution (mode I) and vice versa (mode II). Dominating agglomeration and sedimentation of the compounds has been demonstrated to take place under irradiation in mode I, maximal effect being achieved at absorbed dose 5–15 kGy. Under irradiation in mode II, i.e. when all the incident electrons were being absorbed, the radiation-induced coagulation was depressed. The dependence of radiation effect on irradiation conditions may be caused by stabilizing action of accumulating excess charge of absorbed electrons on negatively charged micelles of lignin and humic acids.