Enhanced Adsorption of Methylene Blue Using H 2 O 2 -Modified Hydrochar

Recently, improving the adsorption capacity of pristine hydrochar by selecting an environmentally friendly, readily available, and low-cost modifier has become a research hotspot. In this research, the pristine hydrochar derived from sawdust (HTC) was treated using the H 2 O 2 , which was expected to get the modified hydrochar (HTC-H) with excellent properties beneficial for methylene blue (MB) removal. Compared to HTC, the HTC-H had higher surface area (increased by 11.20%) and larger CEC (increased by 11.80%); besides, the oxygen-containing functional groups of HTC-H was richer than that of HTC, evidenced by element analysis (higher O/C) and Fourier transform infrared spectroscopy analysis. Because of the improvement of these characteristics, the MB maximum adsorption capacity of HTC-H increased by 45.70%. Moreover, MB adsorption kinetics of HTC-H fit well with the pseudo-second-order-model. In addition, MB adsorption capacity increased at both high pH and ion strengths. All the results showed the H 2 O 2 -modified hydrochar has a good application prospect in environmental applications requiring MB removal. Graphical abstract