Superb adsorption capacity of biochar derived from leather shavings for Congo red

Research on biochar for removal of dyes has been a hot topic because of its excellent eco-friendly and economical properties. In this study, leather shavings biochar (LSB) with high adsorption capacity was prepared and tested with Congo red as a model dye for adsorption. The research results show that the as-prepared biochar exhibits a porous structure, with a high specific surface area (2365 m² g^-1), and it would be beneficial for removing Congo red from effluents. More interestingly, adsorption capacity of LSB for Congo red was enhanced by chromium compounds on the surface of biochar through chelation and electrostatic interactions. Chelation occured between the chromium compounds and amino groups of Congo red. Adsorption data for Congo red on the biochar were successfully described by Langmuir isotherm and the pseudo-second order kinetics model. Langmuir maximum adsorption capacity of LSB at 30 °C reached 1916 mg g^-1, which is much higher than that of conventional activated carbon (AC). Recycling experiment shows that LSB has a potential market for removing Congo red.