• 关键词：生物碳  水稻秸秆  有机污染物  吸附作用  构-效关系

• 基金项目：国家自然科学基金项目(No.41071210);浙江省自然科学基金杰出青年基金项目(No.R5100105)

• 陈再明
• 浙江大学环境科学系,杭州 310058

• 陈宝梁
• 1. 浙江大学环境科学系,杭州 310058;
  2. 浙江省有机污染过程与控制重点实验室,杭州 310058

• 周丹丹
• 1. 浙江大学环境科学系,杭州 310058;
  2. 浙江省台州市环境科学设计研究院,台州 318000

• 摘要：以水稻秸秆为原料,采用限氧裂解法制备了不同温度(100～700 ℃)的秸秆生物碳,用TG-DTG热重分析、CHNO元素分析、FTIR、BET-N₂比表面及孔径分布等手段表征生物碳的组成与结构,研究生物碳吸附水中硝基苯、对硝基甲苯、萘、菲等有机污染物的性能及影响因素,探讨其作用机制及构-效关系,试图为高效利用废弃农业秸秆资源、制备廉价的有机物吸附材料提供理论依据.结果表明,水稻秸秆生物碳含有丰富的有机碳组分和无机矿物组分,随着裂解温度升高,生物碳中有机组分的含碳量逐渐升高、极性减弱、芳香性增强,而无机矿物组分的相对含量则不断增加;当裂解温度从300 ℃升至400 ℃时,比表面积突然增大(0.16→110 m²·g^-1)、微孔结构被打开,主要由于水稻秸秆中纤维素组分大量分解所致.水稻秸秆生物碳吸附有机污染物的主要介质为有机组分,等温吸附曲线符合Freundlich方程,回归参数N、logK_f与生物碳的芳香性指数(H/C原子比)呈良好的线性关系;定量描述了分配作用和表面吸附作用的相对贡献.随碳化温度升高,等温吸附曲线由线性变为非线性,吸附机制从分配作用→分配作用+表面吸附作用→表面吸附作用;分配作用部分与有机污染物的logK_ow呈正相关,而表面吸附则与污染物的疏水性、分子尺寸及其与生物碳的极性匹配性有关.

• Abstract：A series of biochars was prepared by pyrolyzing rice straw, an agricultural wastes, at various temperatures (100～700 ℃) under an oxygen-limited condition. The compositions of biochars were characterized by thermogravimetric analysis (TG-DTG), elemental composition (CHNO), Fourier transform infrared spectroscopy (FTIR) and BET-N₂ specific surface area analysis. Sorption properties of biochars with nitrobenzene, p-nitrotoluene, naphthalene and phenanthrene were investigated. Sorption mechanisms and influential factors were discussed. The result shows that rice straw derived biochars are rich in organic and inorganic fractions. With the increase of the pyrolytic temperature, the organic fraction is progressively pyrolyzed while the inorganic fraction is remained. When the pyrolytic temperature increases from 100 ℃ to 700 ℃, the organic content and polarity of biochar decrease, whereas the aromaticity dramatically increases. The micropores of biochars are suddenly developed and surface area is sharply enlarged (0.16→110 m²·g^-1) when the pyrolyzing temperature rises from 300 ℃ to 400 ℃, which are consistent with the structural alteration derived from FTIR and TG-DTG data. Sorption isotherms fit well with the Freundlich equation, and the Freundlich regression parameters (i.e., N and logK_f) are linearly related to the biochars' aromaticity indices (the H/C atomic ratio). Sorption of biochar is mainly governed by the organic fraction. Contributions of adsorption and partition to total sorption of biochars are quantified. Sorption isotherms of biochars were evolved from linear at relative low pyrolytic temperature to nonlinear at relative high pyrolytic temperature. Correspondingly, the sorption mechanisms were transformed from partition-dominated to combination of partition and adsorption and then to adsorption-dominated. Partition fractions were positively correlated with octanol-water partition coefficients (logK_ow) of organic pollutants, while adsorption was controlled by chemicals' hydrophobicity, dimension and polarity compatibilities between organic molecules and biochars. These observations will provide a theoretical basis to design a cost-effective and high-efficient sorbent based on agricultural biomass waste.

• Key words：biochar  rice straw  organic pollutants  sorption  mechanism

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