Effects Of Pyrolysis Temperature On Biochar Properties And Its Heavy Metal Adsorption Characteristics

Biochar is produced from biomass under anaerobic or anoxic conditions pyrolysis of carbon-rich product. Biomass, the material to form biochar, is widely available and most of them are agricultural and forestry wastes. The adventages of adsorption of heavy metals by biochar are low cost, high efficiency and cause no secondary pollution. Recently, biochar has attracted widespread attention due to its adsorption of heavy metals from solution.Pyrolysis temperature is one of the most important factors that influence the properties of biochar. However, few works on how pyrolysis temperature influences biochar has been studied. Aimed at this goal and considering the environment pollution caused by heavy mental, cornstalk-based biochar(CB) and poplar-based biochar(PB) are produced at a temperature range of 250~450 ℃ and their characteristics on heavy metal adsorption as well as its characteristics were investigated. The main findings are as follows.First of all, the contents of various elements varied with the pyrolysis temperature. The groups of biochar changed with a rise in pyrolysis temperature and the aromaticity was enhanced. The characteristics of biochars were closely related to the pyrolysis temperature and biomass resource.In this study, the adsorption of Cr(Ⅵ) and Pb(Ⅱ) on two biochars was studied. Results showed that the adsorption of Pb(II) on biochar had a close agreement with both Langmuir and Freundlich models and the adsorption of Cr(VI) agreed better with Langmuir model. In terms of kinetic model, adsorption of Cr(Ⅵ) and Pb(Ⅱ) followed pseudo second order kinetic model. The substantial acidic functional groups on biochars surface played a crucial role on the adsorption of Cr(Ⅵ). Cation exchange capacity and precipitation played a crucial role on the adsorption of Pb(Ⅱ). The characteristics of biochars adsorption of Cr(Ⅵ) and Pb(Ⅱ) were closely related to the pyrolysis temperature and biomass resource.Based on the result, it is important reference for biochar further practical application. At the same time, it is meaningful for solving environmental and energy problems which currently present.