Physicochemical properties and lead ion adsorption of biochar prepared from Turkish gall residue at different pyrolysis temperatures

How to correctly and scientifically dispose of medicine residue on the basis of protecting the environment is an urgent problem to be solved due to the continuous generation of a large amount of waste medicine residue. In this paper, the application of waste medicine residue (large volume produced each year) as a precursor in producing a biochar that could adsorb Pb ion was reported. Biochar is a stable, aromatic, porous substance that is rich in carbon and prepared through pyrolysis of waste biomass under anaerobic conditions. In this study, medicine residue was used as raw material, and high‐temperature sintering furnace was used to prepare medicine slag biochar at different temperatures of 200°C, 300°C, 400°C, 500°C, and 600°C. The resulting biochar was characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), specific surface area analysis, field emission‐scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), and Raman spectroscopy (RS). Experimental results showed that with the increase in pyrolysis temperature, the biochar structure was destroyed. The yield decreased as the temperature gradually decreased from 81.69% to 33.90%. With the increase in temperature, the pH, the ash, and the fixed carbon gradually increased, whereas the number of surface functional groups decreased. The quasi second order kinetic equation can better fit the kinetic characteristics of adsorbing Pb ion by biochar. In general, this study provides a valuable method for recycling medicine residue. Characteristics of biochar. Temperature can affect the structure and such physic‐chemical properties as pH, retaining carbon, ash content and C content of biochars. The carbon of biochars is highly ordered and aromatized. The process of absorbing Pb ion by the biochars is the quasi second order kinetic equation.