Characteristics of waste hair biochar and its adsorption to Ni(Ⅱ) and Zn(Ⅱ)

The properties of biochar prepared from waste hair were analyzed by element composition and SEM, and the adsorption ability to heavy metals from domestic wastewater observed.The adsorption kinetics processes of Ni(Ⅱ) and Zn(Ⅱ)were fitted by Lagergren model, and the adsorption isotherm of Ni(Ⅱ) and Zn(Ⅱ) fitted by Langmuir and Freundlich models to investigate the adsorption characteristics of biochar on heavy metals Ni(Ⅱ) and Zn(Ⅱ) in water. The results showed that the carbon content of biochar was high, being alkaline, and the surface structure had porosity with strong adsorption ability. At carbonization temperatures of 300 and 350 °C, the actual maximum equilibrium adsorption for Ni(Ⅱ) was 5.48 and 6.25 mg/g, and the actual maximum equilibrium adsorption for Zn(Ⅱ) was 3.02 and 3.78 mg/g, respectively. The Lagergren model can well describe the adsorption process of Ni(Ⅱ) and Zn(Ⅱ), mainly with chemical adsorption; and the higher the carbonization temperature, the faster the adsorption rate. Langmuir and Freundlich model fitting curves can better describe the isothermal adsorption of Ni(Ⅱ) and Zn(Ⅱ); and the higher the adsorption temperature, the more the adsorption capacity. At the temperature of 20,30 and 40 ℃, the saturated adsorbents of Ni(Ⅱ) were 5.59,7.16 and 7.23 mg/g, and the saturated adsorbents of Zn(Ⅱ) were 1.28,1.29 and 1.32 mg/g, respectively.