高温与冻融循环对水热炭和生物炭吸附污染物的影响

将农林废弃物通过不同碳化方式制备成水热炭或生物炭,用于土壤改良和环境污染修复,是当前研究和应用的热点领域。由于受到不同自然条件的长期影响,如环境温度变化,水热炭和生物炭会发生老化作用,从而影响其对污染物的吸附能力,因此,评估老化作用对碳化材料吸附能力的影响是一个重要的科学问题。采用高温和冻融循环2种加速老化方式模拟自然界中的温度变化,对稻壳和玉米秸秆水热炭、生物炭进行老化培养,通过元素分析仪、傅里叶红外光谱分析仪、扫描电子显微镜等手段对老化前后水热炭、生物炭样品的物化性质进行分析,通过批实验对比研究2种新鲜炭材料对Cd(II)及莠去津的吸附能力及吸附稳定性,并研究了30、60、90次老化循环后生物炭和水热炭吸附能力的变化。结果表明,生物炭对Cd(II)和莠去津有良好的吸附稳定性,而水热炭对莠去津的吸附稳定性较差。2种老化作用均使水热炭、生物炭表面含氧官能团增加,从而增强了水热炭、生物炭对Cd(II)和莠去津的吸附能力。在高温和冻融环境中,随着老化时间的持续,生物炭比水热炭更容易受到环境的影响。研究相关成果对于水热炭和生物炭合理应用于不同环境的污染修复具有试验参考价值。

Effects of High Temperature and Freeze-thaw Cycle Ageing on Adsorption Performance of Hydrochar and Biochar on Pollutants

The application of hydrochar or biochar derived from agricultural wastes into soil amendments and remediation is one of hot topics nowadays. Due to long-term varied natural condition, such as changed ambient temperature, the properties of hydrochar or biochar would change and have some effect on the adsorption capacities. Hence, it is an important issue to assess the adsorption performance of hydrochar and biochar under the effect of ageing. In the study, high temperature ageing and freeze-thaw cycle ageing were used to simulate the changed ambient temperature. The physicochemical properties of fresh and aged rice husk and corn straw derived biochars and hydrochars were compared by multi-techniques of elemental analysis, Fourier infrared spectrometer (FTIR) and scanning electron microscope (SEM). The adsorption capacity and stability of hydrochar and biochar, as well as the effects of different ageing time (e.g., 30, 60, 90 cycles) on their adsorption capacity, were compared by batch experiments. The results showed that biochar had good adsorption stability for Cd (II) and atrazine, while hydrochar had poor adsorption stability for atrazine. The two ageing processes increased the oxygen containing functional groups of hydrochar and biochar, thus enhancing the adsorption capacity of Cd (II) and atrazine. In high temperature and freeze-thaw environment, biochar was more susceptible to environmental effects than hydrochar as the ageing time increased. The obtained results from this study suggest us to consider the rational use of hydrochar and biochar in the environmental remediation.