羊粪生物炭对水体中诺氟沙星的吸附特性

Adsorption characteristics of norfloxacin in aqueous solution by sheep manure biochar

以羊粪为原料分别在350、450、550、650℃条件下制备生物炭,通过元素分析、BET-N_2、电镜扫描及FTIR表征了不同热解温度下羊粪生物炭的结构特征,并采用序批实验研究了pH、生物炭投加量、热解温度、初始浓度等因素对羊粪生物炭吸附水体中诺氟沙星(NOR)的影响及吸附机制.结果表明,随着热解温度的升高,生物炭的比表面积、总孔容、平均孔径增大,芳香性和稳定性也有所提高.羊粪生物炭吸附NOR的最佳初始pH为6.0,吸附在180 min左右达到平衡,采用准二级动力学模型能更好地拟合动力学数据(R^2>0.96),吸附速率由表面吸附和颗粒内扩散共同控制.等温吸附拟合发现,Langmuir模型能较好地描述NOR在羊粪生物炭上的吸附行为(R^2>0.93),吸附过程均为有利吸附,且可能与氢键和π-π键作用密切相关,4种热解温度下生物炭的吸附能力大小为:650℃>550℃>450℃>350℃.吸附过程中ΔGθ<0、ΔHθ>0、ΔSθ>0,表明羊粪生物炭对NOR的吸附是自发、吸热及熵增加的过程.650℃和550℃条件下制备的羊粪生物炭可作为水体中NOR的优势吸附材料.

Sheep manure was pyrolyzed to prepare biochars under different temperatures of 350, 450, 550 and 650℃. Elemental analysis, BET-N2, scanning electron microscopy and FTIR spectra were used to measure their structure and properties. Batch experiments were conducted to investigate norfloxacin （NOR） adsorption by using the prepared biochars, as well as the possible influencing factors, such as pH, adsorbent dosage, temperature and initial concentration. The results show that the specific surface area, total pore volume, average pore size, aroma and stability of the hiochars were increased with as the rising temperature. The optimal initial pH for adsorption was 6.0, and the adsorption equilibrimn time was 180 min. The pseudo- second-order kinetic model was effective to reflect the adsorption process which was influenced by the surface adsorption and the particles diffusion. The Langmuir model was reasonable to describe the adsorption behavior, which was possibly related to the hydrogen bond and π-π bond. The adsorptive capacity followed by different pyrolysis temperatures was 650, 550, 450, and 350℃. The results of thermodynamic analysis（ △Gθ 〈0,△Hθ〉0,△Sθ〉0） show that the NOR adsorption was a spontaneous and exothermic process increased by entropy. The bioehars prepared at 650℃ and 550℃ were considered as the optimal adsorbents.