改性柚子皮对水中Pb^(2+)的吸附行为研究

Adsorption performance of Pb 2+in aqueous solution by modified pomelo peel

经NaOH-草酸改性废弃柚子皮制得低成本柚子皮生物吸附剂.通过考察pH值、吸附剂量、铅离子初始质量浓度、吸附时间等影响因素,系统研究改性柚子皮生物吸附剂对水中Pb^(2+)的吸附性能;利用红外光谱技术对改性前后柚子皮进行了表征,提出了NaOH-草酸对柚子皮的协同改性机制并对吸附等温线、吸附动力学以及吸附热力学进行了分析.结果表明,柚子皮经NaOH-草酸改性后,可提高羧基官能团数目,使吸附Pb^(2+)能力提高.相同条件下,柚子皮及改性柚子皮对Pb^(2+)的吸附容量分别是3.68 mg/g和18.76 mg/g.Pb^(2+)初始质量浓度50 mg/L、溶液pH值5.0、改性柚子皮生物吸附剂投加量8 g/L、吸附90min时,Pb^(2+)去除率为96.10%;Pb^(2+)的吸附过程可以用准二级动力学模型以及Langmuir等温模型很好地描述.生物吸附剂对Pb^(2+)的吸附是自发的吸热过程.

The pomelo peel was modified via sodium hydroxide and oxalic acid to obtain a low-cost biomass adsorbent-modified pomelo peel sorbent(MPPS).The pomelo peel sorbent(PPS)before and after modification(MPPS)was characterized by Fourier transform infrared spectroscopy(FTIR)and the synergistic modification mechanism of sodium hydroxide and oxalic acid on pomelo peel was analyzed.While the influencing factors such as pH,adsorbent dosage,initial Pb^(2+)concentration and contact time on the adsorption of Pb^(2+)onto MPPS were investigated by batch experiments.In addition to this,the isotherms,kinetics and thermodynamics of the biosorption were also studied.The results showed that the carboxyl groups of the pomelo peel increased after modification via sodium hydroxide and oxalic acid and thus improved the adsorption performance.The adsorption capacities of Pb^(2+)onto PPS and MPPS were 3.68 mg/g and 18.76 mg/g respectively under the same condition and the removal rate of Pb^(2+)achieved 99.9%after 90 minutes while pH value is 5.0,the initial concentration of Pb^(2+)is 50 mg/L and the dosage of the biosorbent is 8 g/L.The adsorption was well described by a pseudo-second order kinetic model and the adsorption process was fitted by the Langmuir model.Furthermore,the absorption was a spontaneous,endothermic process.