改性西瓜皮生物炭的制备及其对Pb(Ⅱ)的吸附特性

Preparation of Modified Watermelon Biochar and Its Adsorption Properties for Pb(Ⅱ)

以西瓜皮为原料,使用硫化铵[(NH4)2S]对其改性制备生物炭(MBC),用于对Pb(Ⅱ)进行吸附.探究了溶液pH、吸附时间、吸附剂添加量、Pb(Ⅱ)初始质量浓度和离子强度等因素对Pb(Ⅱ)吸附效果的影响.结果表明,饱和吸附时间为5 h,吸附反应的最佳pH为6,当Pb(Ⅱ)初始质量浓度1000 mg·L^-1,吸附剂添加量为2.0 g·L^-1时,MBC对Pb(Ⅱ)的最大吸附量可达97.63 mg·g^-1,明显高于未改性西瓜皮生物炭(BC)对Pb(Ⅱ)的吸附量.改性西瓜皮生物炭对Pb(Ⅱ)的吸附符合Langmuir等温吸附模型和拟二级动力学模型,证明吸附以单分子层化学吸附为主.使用氢氧化钠溶液对吸附Pb(Ⅱ)之后的MBC进行解吸来研究MBC的可重复使用性,在第六次循环中吸附量仍达64.74 mg·g^-1.采用傅立叶转换红外光谱(FT-IR)、X射线光电子能谱(XPS)、氮吸附(BET)、扫描电镜-能谱分析(SEM-EDS)、X射线衍射(XRD)和Zeta电位对吸附剂进行表征分析,发现吸附机制主要是MBC含氧和MBC含硫基团通过络合作用和沉淀作用来吸附Pb(Ⅱ).因此,硫化铵改性西瓜皮生物炭可以作为一种高效的Pb(Ⅱ)吸附剂.

In this study,watermelon rind was used as a raw material to modify watermelon rind biochar(MBC)with ammonium sulphate[(NH4)2S]for adsorption of Pb(Ⅱ)ions.The effects of solution pH,adsorption time,adsorbent addition amount,initial mass concentration of Pb(Ⅱ)ions,and ionic strength on the adsorption of Pb(Ⅱ)ions were investigated.The results show that the saturated adsorption time was 5 h,the optimum pH of the adsorption reaction was 6,and when the initial mass concentration of Pb(Ⅱ)ions were 1000 mg·L^-1,and the amount of adsorbent was 2.0 g·L^-1.The maximum adsorption amount of MBC to Pb(Ⅱ)ions can reach 97.63 mg·g^-1,which is significantly higher than unmodified watermelon husk biochar(BC).The adsorption of Pb(Ⅱ)ions by modified watermelon biochar was in accordance with the Langmuir isotherm adsorption model and the pseudo second-order kinetic model,which proves that adsorption is dominated by monolayer chemical adsorption.The desorption of MBC after adsorption of Pb(Ⅱ)ions was carried out using a sodium hydroxide solution to study the reusability of MBC,and the adsorption amount was still 64.74 mg·g^-1 in the sixth cycle.Characterization and analysis of adsorbents by Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,nitrogen adsorption,scanning electron microscopy-energy spectroscopy,zeta potential analysis,and X-ray diffraction(XRD)were carried out,which showed that the adsorption mechanism is mainly that MBC oxygen-and MBC sulfur-containing groups adsorb Pb(Ⅱ)through complexation and precipitation.Therefore,ammonium sulfide modified watermelon rind biochar can be used as a highly efficient lead adsorbent.