(2013?Anhui simulation) A sewage treatment method used in industry is as follows: keep the pH of the sewage between 5.0 and 6.0, and generate Fe(OH) precipitate by electrolysis.

A. Maintain the pH of the sewage between 5.0 and 6.0, through electrolysis to generate Fe (OH) 3 precipitation, added to make the conductive ability to enhance the electrolyte must be soluble in water, neutral salt, adding sulfuric acid can not generate Fe (OH) 3 precipitation, so A error;

B. Electrolysis cell Fe for the anode, the occurrence of Fe-2e-=Fe2 +, so B error;

C. The battery is a molten carbonate as an electrolyte, the negative electrode reaction is CH4+4CO32--8e-=5CO2+2H2O, the positive electrode reaction is O2+2CO2+4e-=2CO32-, and the only substance that can be recycled is carbon dioxide, so C is correct;

D. The cathode's electrode reaction is: 2H++2e-=H2↑. The cathode produces 44.8L (standard condition) that is, 2mol of hydrogen produced, so the amount of material transferred electrons for 4mol, according to the battery's negative electrode reaction is CH4 + 4CO32 - 8e - = 5CO2 + 2H2O, when the B device has 1.6 gCH4 to participate in the reaction, that is, 0.1mol of methane to participate in the reaction, there is a 0.8 mol of electrons transferred, then C electrode Theoretically, the gas generated in the standard condition is 8.96L, so D is wrong.

Therefore, choose C.