Study on the kinetics of the adsorption of reactive brilliant red K-2BP onto modified soybean straw activated carbon

In this paper, the soybean straw was modified into activated carbon adsorbent by chemical activation using zinc chloride as activator, and the influence of pH on the adsorption effect and the adsorption kinetic characteristics of reactive brilliant red K-2BP under different dosage, oscillation speed and temperature were investigated by static experiments. In addition, the kinetic date were respectively fitted by pseudo-first-order equation, pseudo-second-order equation and the intra particle diffusion equation. It was found that the adsorption effect could reach the best and the decolorization rate was as high as 95.6% when pH was 4. The adsorption effect was mainly affected by the dosage of adsorbent, and temperature and oscillation speed had little effect on it. The pseudo-second-order equation could provide good description to the adsorption process which was about the adsorption of adsorbent to reactive brilliant red K-2BP, and the correlation coefficient R-2 of which could reach at 0.999. The intra particle diffusion equation indicated that intra particle diffusion was the main control step of the adsorption rate but not the sole rate controlling step. Thermodynamic analysis suggested that the adsorption activation energy was small and its value was 16.6 KJ/mol, which indicated that the adsorption type of the whole process mainly was physical adsorption and its adsorption rate was fast. When the temperature was 20 degrees C, 25 degrees C or 30 degrees C, the Delta G* was greater than zero. It indicated that the adsorption was a non-spontaneous reaction, which required additional energy to promote the reaction.