磁性生物质炭制备方法及其对水体Pb^(2+)吸附特性的影响

INFLUENCE OF MAGNETIC BIOCHAR PREPARATION METHODS ON ADSORPTION CHARACTERISTICS OF Pb^(2+) IN WASTEWATER

为了获得兼具磁分离和优良吸附性能的环境友好型吸附材料,以杉木(FW)为原材料制备生物质炭(FWBC),分别用沉淀法、浸渍法制得磁性生物质炭FWFe(2)、FWFe(3)。通过元素分析、磁性分析、SEM-EDS、XRD、FTIR等手段表征生物质炭吸附前后特性。研究了FWFe(2)、FWFe(3)对水中Pb^(2+)的吸附特性,探讨了2种磁化方法吸附Pb^(2+)的机理。结果表明:磁化后的生物质炭含有Fe_(3)O_(4)颗粒。FWFe(2)和FWFe(3)的饱和磁化强度分别为35.59,27.76 emu/g,具有良好的磁分离能力。FWFe(2)、FWFe(3)吸附Pb^(2+)的过程符合准二级动力学和Langmuir等温吸附模型。FWFe(2)的吸附性能明显优于FWFe(3)和FWBC,平衡吸附量达到817.64 mg/g,是FWBC的12倍。采用沉淀法磁化的生物质炭可有效提高对水体Pb^(2+)的吸附。吸附机理主要包括离子交换和金属(氢)碳酸盐共沉淀、物理吸附、与表面官能团的络合反应。研究结果有利于推进农林废弃生物质的资源化利用及磁性生物质炭在环境中的实际应用。

In order to prepare environmental-friendly adsorption materials with magnetic separation and excellent adsorption properties,the effect of different preparation methods on the adsorption properties of biochar was investigated.Fir wood(FW)pruned from deforestation residues was used as the feedstock.The original biochar FWBC was obtained by pyrolysis of FW at high temperature.Magnetic biochars FWFe(2)and FWFe(3)were prepared by two methods:precipitation and impregnation.The biochar was characterized by elemental analysis,magnetic analysis,SEM-EDS,XRD and FTIR.The adsorption characteristics of FWFe(2)and FWFe(3)for Pb^(2+) in water were studied.The adsorption mechanisms of different biochars were discussed.The results showed that the magnetized biochars contained Fe_(3)O_(4) particles.The saturation magnetization of FWFe(2)and FWFe(3)were 35.59 and 27.76 emu/g,respectively,which indicated good magnetic separation capability for all kinds of biochars.The Pb^(2+)adsorption characteristics by FWFe(2)and FWFe(3)were more in line with the pseudo second order kinetics and Langmuir isotherm model,which indicated that the adsorption was mainly chemical adsorption.The adsorption performance of the magnetized FWFe(2)was significantly better than that of FWFe(3)and the original biochar.The equilibrium adsorption capacity was 817.64 mg/g,which was 12 times of that of FWBC.Magnetization by precipitation method could effectively improve the adsorption of Pb^(2+).The adsorption mechanism mainly included ion exchange and metal(hydrogen)carbonate coprecipitation,physical adsorption and complexation with surface functional groups.The results were helpful to promote the utilization of agricultural and forestry waste biomass and the practical application of magnetic biochar in environment.