Efficient adsorption of three dyes by soybean residue (okara) biochar in an aqueous solution.

In this study, biochar (BC) was prepared from okara (BC-OA) and applied to the adsorption of methylene blue (MB), neutral red (NR) and malachite green (MG) in aqueous solutions. Different analytical techniques characterized the structure and surface chemical properties of the adsorbents. The results were used to analyze the adsorption interaction between BC-OA and contaminants, and a single factor test determined the optimal adsorption conditions. The results showed that the removal ratio increased with the solution pH value, indicating that the alkaline condition was more conducive to adsorption. In the adsorption--desorption regeneration experiment, the adsorption performance of BC-OA decreased slightly, reflecting the stability of BC performance. The Langmuir isothermal adsorption model could describe the adsorption process better, with correlation coefficient (R²) of 0.9565, 0.9870 and 0.9825, and qm of 294.04, 583.50 and 1,058.36 mg/g, respectively. The fitting results of the pseudo-first-order kinetic model show that chemisorption controls the whole adsorption process. In this work, the adsorbent (BC) was prepared by using okara biomass material. The experimental results show that the adsorption effect is good, the adsorption speed is fast, the preparation process is simple and environmentally friendly, and BC can be used as a new type of high-efficiency adsorbent, which can expand its application in dyes wastewater treatment. [ABSTRACT FROM AUTHOR]