秸秆生物炭对双氯芬酸钠的吸附性能研究

Adsorption of diclofenac on straw-biochar

利用廉价的农业废弃物稻草秸秆,通过磷酸氢二铵((NH_4)_2HPO_4)活化制备得到秸秆生物炭(SBC),通过扫描电子显微镜(SEM)、比表面积分析(BET)、红外光谱(FTIR)等手段对其进行表征.研究了SBC对双氯芬酸钠(DCF)的吸附去除,并探讨了吸附时间、SBC投加量、pH值、阴离子浓度对吸附过程的影响.结果表明,当SBC投加量为0.3g/L时,DCF浓度为0.05mmol/L,60min后吸附量达到平衡;pH值范围在5.00～9.00时,SBC对DCF的吸附量去除率随着pH值的增加而减少;Cl^-、SO_4^(2-)和HCO_3^-对吸附过程的影响不大.拟合结果表明,SBC对DCF的吸附过程更符合准二级动力学模型和Freundlich吸附等温线.经Langmuir等温线模型计算理论最大吸附量为277.78mg/g(pH=7.00,T=20℃).热力学参数表明SBC对DCF的吸附是自发吸热过程.同活性炭和碳纳米管相比,SBC对DCF的吸附效果更好.

Straw-biochar (SBC) was prepared by rice straw, a cheap agricultural waste, through activation with ammonium hydrogen phosphate ((NH4)2HPO4). SBC was characterized by scanning electron microscopy (SEM), surface area measurements (BET) and Fourier transform infrared spectroscopy (FTIR). The effect of contact time, SBC dosage, initial pH and concentration of anions were investigated. The results indicated that adsorption capacity of SBC reached an equilibrium within 60min with 0.3g/L of SBC and 0.05mmol/L DCF. The removal rate of DCF decreased with pH increasing from 5.00 to 9.00. The addition of Cl-、SO4^2- and HCO3^- had a negligible impact on the adsorption of DCF. The adsorption of diclofenac on SBC could be well fitted by the pseudo-second-order kinetics and Freundlich isotherm model. The maximum adsorption capacity of SBC for DCF was calculated to be 277.78mg/g based on Langmuir isotherm model. Thermodynamic parameters illustrated that the adsorption process was spontaneous and endothermic. Compared with activated carbon (AC) and carbon nanotube (CNT), SAC achieved a better performance on the removal of DCF.