Porous biochar composite hydrogel for effective removal of low-concentration methylene blue from wastewater

In this work, two kinds of porous biochar composite hydrogel were prepared to effectively remove low-concentration dyes via simple one-pot aqueous polymerization. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), x-ray diffraction (XRD), thermogravimetric analysis (TGA), confocal laser scanning microscope (CLSM), and x-ray photoelectron spectroscopy (XPS) were used to confirm the successful synthesis of the composite hydrogels and the mesoporous structure was further verified through BET method. The adsorption factors were also studied, and the two adsorbents presented high removal efficiency in low concentration methylene blue (MB) solution. The adsorption process fitted the Freundlich isotherm model well, and the adsorption kinetics followed the pseudo-second-order kinetics model. After eight cycle tests, the composite hydrogels still kept a high removal efficiency for MB. In conclusion, the prepared composite hydrogels can be used as an effective adsorbent for removing the dyes from wastewater.