Abstract:

The process conditions of wood-based activated carbon were optimized by using agriculture and forestry waste, peanut shell, as raw material, phosphoric acid as activator and sulfuric acid as auxiliary activator. The impacts of phosphoric acid concentration, impregnation ratio(volume-mass ratio of activator to peanut shell), activation time, activation temperature on the properties of activated carbon were investigated by using the response surface methodology. The results showed that through Box-Behnken test data, the P value of mathematical model of quadratic polynomial on the methylene blue adsorption value and iodine adsorption value was less than 0.000 1, the correct determination coefficients(R²) were 0.990 2 and 0.997 8, respectively, reached extremely significant level; and CV was less than 10%, the experiment had most high credibility and accuracy, and the regression equation was established. The optical process conditions of using phosphoric acid-sulfuric acid activation method to prepare peanut shell based activated carbon were peanut shell powder 1 g, phosphoric acid mass fraction 57.7%, impregnation ratio 2:1, activation time 117 min and activation temperature 550 ℃. Under the conditions, the methylene blue adsorption value was 147.2 mg/g, the iodine adsorption value was 1 022.03 mg/g, which was close to the predicted values and had good repeatability, the inner hole of the peanut shell base activated carbon was more developed, the larger methylene blue adsorption value and the relatively small iodine adsorption value maked the activated carbon have stronger adsorption capacity and desorption capacity, the study of preparation mechanism of peanut shell activated carbon had laid a solid foundation.

Key words: Box-Behnken design, phosphoric acid-sulfuric acid activation, peanut shell, activated carbon