热解温度调控棉秆生物炭对PSNPs吸附性能与机制的影响

Effect of Pyrolysis Temperature on Adsorption Performance and Mechanism of Cotton Stalk Biochar for Polystyrene Nanoplastics

摘要:

针对农业面源微塑料污染问题，以棉秆为原料，在350~750℃下制备系列生物炭，系统考察热解温度对生物炭理化性质和对聚苯乙烯纳米塑料（PSNPs）吸附性能的影响，结合SEM、BET、FTIR及XPS等表征手段，揭示其对PSNPs的吸附机制。结果表明：随热解温度升高，生物炭产率由36.65%降至26.34%，芳香化程度增强（H/C由0.752降至0.197），孔结构呈先发育后衰减趋势，表面极性和含氧官能团含量呈下降趋势;650℃生物炭（CS650）性能最优，比表面积达202.03 m2/g，微孔占比96.1%，芳香碳比例75.99%，平衡吸附容量达最大值12.68 mg/g;此时，吸附动力学符合Elovich模型（R2=0.9899），等温线符合Sips模型（R2=0.9906），理论最大吸附容量39.3 mg/g，吸附性能主要以表面附着和孔口截获为主，π-π相互作用与氢键协同促进等多机制实现高效吸附，且酸性条件下吸附容量较高。研究结果为农业废弃物精准高效利用及微塑料污染控制提供了技术支撑。

Abstract:

Aiming at the pollution problem of agricultural non-point source microplastics, a series of biochar were prepared from cotton stalk at 350~750℃. The effects of pyrolysis temperature on the physical and chemical properties of biochar and the adsorption performance of polystyrene nanoplastics (PSNPs) were systematically investigated. Batch adsorption experiments, including kinetics, isotherms and pH effect were conducted to evaluate the adsorption behaviors. Moreover, the adsorption mechanism was elucidated by SEM, BET, FTIR and XPS characterizations. The results showed that with the increase of pyrolysis temperature, the yield of biochar was decreased from 36.65% to 26.34%, the degree of aromatization was increased (H/C decreased from 0.752 to 0.197), the pore structure developed first and then declined, and the content of surface polarity and oxygen-containing functional groups was decreased. At 650℃, the biochar (CS650) exhibited the best performance, with a specific surface area of 202.03 m2/g, micropores accounting for 96.1%, aromatic carbon accounting for 75.99%, and the maximum equilibrium adsorption capacity of 12.68 mg/g. The adsorption kinetics conformed to the Elovich model (R2=0.9899), and the isotherm fitted the Sips model (R2=0.9906), with a theoretical maximum adsorption capacity of 39.3 mg/g. The adsorption process was mainly achieved through surface adhesion and orifice interception, synergistically promoted by π-π interaction and hydrogen bonding. Additionally, solution pH values significantly affected the adsorption, with acidic conditions being more favorable due to weakened electrostatic repulsion. The research result can provide technical support for accurate and efficient utilization of agricultural waste and microplastic pollution control.