Fabrication of bean dreg-derived carbon with high adsorption for methylene blue: Effect of hydrothermal pretreatment and pyrolysis process

This study explored the cooperative effects of hydrothermal or activators pretreatment and pyrolysis process on the chemical composition of bean dreg (BD)-derived carbon materials and its adsorption characteristics for methylene blue (MB) further. The results showed that hydrothermal assisted pyrolysis carbon with or without activator (HBK and HB) possess higher BET surface area than no hydrothermal assisted carbon (BKs and B, respectively). But surface area alone was not a critical factor contributing to MB adsorption, it also depends on strong electrostatic interaction and the hydrogen bonding interaction between N+ in MB combines with OH and COO− group of adsorbent surface by pH-dependent adsorption and pseudo-second-order model. Additionally, BK800 (pyrolysis at 800 °C) was identified as the most efficient adsorbent due to maximum adsorption capacity (434.78 mg g−1), and BDP (BD-derived polymer composite hydrogel), possessing excellent adsorption property and high reusability, made BK800 easier to separate from the regenerated dye solution.