The electroreduction process of nitrobenzene

which consists of a series of elementary processes

is a complicated reaction system. Besides p-aminophenol

some by-products

such as azoxybenzene

azobenzene and diaminodiphenyl ether can also be produced in the process. These by-products which hardly dissolve in H2SO4 aqueous solution will adsorb and deposit on the surface of membrane material gradually and thus pollute the membrane material

which causes increases in bath voltages and decreases in current efficiency. In the paper

from the viewpoint of engineering application the fouling and cleaning processes of Nafion membrane in the direct electrochemical synthesis of p-aminophenol were investigated.In the process of direct electroreduction of nitrobenzene

the bath voltages and the current efficiency at different service times of Nafion membrane were measured

respectively.The fouling ratio of membrane and the cleaning degree of fouled membrane

characterized with bath voltage

were defined in this paper. Further

the fouling rate equation of Nafion membrane was presented.With the equation

the fouling rates and the fouling ratios of Nafion membrane at different service times could be calculated easily. Meanwhile

the bath voltages and the current efficiency at the different service times of Nafion membrane could be calculated easily as well. A kind of membrane cleaning agent consisting of anionic surfactants(AES

ABS and R-3)

nonionic surfactants(JFC

APG-10 and Tween-60)

isopropanol and water

was presented.When the fouled Nafion membrane was cleaned by the cleaning agent online for 2 h in the condition of pH≈13

60 ℃ and 4 L8226;min-1 circulation velocity

the bath voltage

SEM morphologies of membrane and membrane resistances could be restored to those of the initial membrane basically.The cleaning degree of fouled membranes was still close to 1 after the cleaning agent was used for 5 times repeatedly

and the strength of rinsed membranes was still the same as that of the initial membrane.