| Rice husk-based porous carbon were prepared by using H3PO4 and K2CO3 according to the development and shortcoming of porous carbon adsorption materials. The effects of the technologic factors of activation temperature, activation time, activation agent concentration, impregnation ratio and time on the yield and iodine adsorption performance of activated carbon (AC) were systematically investigated after using thermogravimetry to analyse the pyrolysis mechanism of rice husk, carbonized rice husk removed silicon, rice husk/ H3PO4, carbonized rice husk removed silicon/ H3PO4, rice husk/ K2CO3, carbonized rice husk removed silicon/ K2CO3. The main technology factors which affected the yield and absorption performance of rice husk-based activated carbon were sifted by Plackett-Burman (P-B) design, prediction model of iodine adsorption number were developed by using central composite design (CCD). The BET surface area, pore size distribution, microstructure, phase structure, surface functional groups were investigated by using specific surface area analyzer(BET), scanning electron microscope (SEM), X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), respectively. The adsorption effect of methylene blue dye was also investigated by activated carbon using K2CO3 activation method. The results were showed as the following:The activation energy and preexponential factor of rice husk and carbonized rice husk removed silicon in the pyrolysis temperature range (490～640K, 490～1020K) were 47.3 KJ/mol, 1.73×103 min-1 and 8.04KJ/mol, 5×10-2 min-1, respectively. The carbonization temperature was reduced 70K by the activation agent H3PO4, and the pyrolysis temperature range of rice husk / H3PO4 was between 600K to 823K. The yield of the samples prepared by using H3PO4 would decrease, the iodine adsorption value of samples would increase first and then decrease with increasing in activation temperature,impregnation time and ratio while keeping other technological factors as a constant. The yield and iodine adsorption value of rice husk and carbonized rice husk removed silicon were 48.3%, 35.4% and 651 mg·g-1, 953.4 mg·g-1 when the activation temperature, activation time, concentration of H3PO4, impregnation ratio and impregnation time kept at 723K, 0.42h, 36%, 4.5 and 12h, respectively.The pyrolysis temperature range of rice husk / K2CO3 was between 750K to 1173K through the analysis of TG and DTG curves of rice husk/ K2CO3 and carbonized rice husk removed silicon/ K2CO3. The yield of the samples prepared by using K2CO3 would decrease, the iodine adsorption value of samples would increase first and then decrease with increasing in activation temperature,activation time, concentration of K2CO3, impregnation ratio and time while keeping other technological factors as a constant. The yield and iodine adsorption value of rice husk and carbonized rice husk removed silicon were 15.51%, 20.23% and 1191.5 mg·g-1, 913.2 mg·g-1 when the activation temperature, activation time, concentration of K2CO3, impregnation ratio and impregnation time kept at 1123K, 1h, 2.5mol/L, 4.5 and 24h, respectively. The main technology factors such as activation temperature, concentration of K2CO3 and activation time which affected the yield and iodine adsorption value of rice husk-based activated carbon sifted by Plackett-Burman (P-B) design. The equation models were highly significant correlation(P < 0.0001, P <0.01), after optimized the experimental conditions of activated carbon prepared by using K2CO3 by CCD. The optimal conditions of rice husk-based activated carbon were obtained by using Design Expert7.0: the rice husk was infused in 1.95 mol/L K2CO3 solution, and then heat treating for 1.17h at 1029K, the value of yield and iodine adsorption number were 13.61%, 1058.83 mg/g. The verification test showed that the value of yield and iodine adsorption number were 14.53%,1021.3mg/g under the optimal conditions, agreed with the predicted values with 6.3%, 3.7% deviation, respectively.The specific surface area, pore size distribution, microstructure, phase structure and surface functional groups of activated carbon were investigated by using BET, SEM, XRD and FT-IR and results showed that specific surface area, total pore volume, micropore volume, mesoporous volume and mean pore size of AC1 were 1312m2/g, 0.78mL/g, 0.61 mL/g, 0.17 mL/g and 11.92 ?. The sample of AC2 has much pore. The average pore sizes of AC2, AC3 and AC4 were 4.7~5.6μm, 2~8μm and 3~7μm, respectively. The interplanar spacing of AC2(002) was greater than AC1, there were K2CO3,KOH,K2O and K in AC2, the interplanar spacing of AC4(002) was greater than AC3. There were -OH,-CH-,-C=O in the rice husk and carbonized rice husk removed silicon, the content of -Si-O decreased greatly after the rice husk carbonized and removed silicon. There were–OH, -C=C, -Si-O in the AC1, AC3, AC4.The influencing factors such as the initial concentration of methylene blue(MB), oscillation time, pH value and the dosage of AC on the removal rate of MB were investigated and the results showed that the removal rate of MB would decrease with increasing in the concentration of methylene blue(MB), the removal rate of MB would decrease from 99.5% to 60.4% when the concentration of MB increased from 300mg/L to 600mg/L. The removal rate of MB would increase with increasing in the dosage of AC or prolonging the oscillation time, the removal rate of MB increased from 52.5% to 60.1%. When 0.3g AC was put into the MB which initial concentration was 1000mg/L, the removal rate of MB reached to 99.98%. The best adsorption can be obtained when the pH value was 6. The adsorption of MB by rice husk-based porous carbon was best fitted to the Langmuir model, the maximum adsorption value Qm would decrease with increasing in the temperature, when the temperature was 298K, Qm reached to maximum value 476.2 mg·g-1. TheΔG0,ΔH0 andΔS0 were negative at different temperatures, which showed that the adsorption of rice husk-based porous carbon was a spontaneous and exothermic reaction.
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