针铁矿改性生物炭对砷吸附性能

Application of Goethite Modified Biochar for Arsenic Removal from Aqueous Solution

为了提高生物炭(BC)对砷的吸附能力,本研究选取小麦秸秆作为原料,采用共沉淀方法制备了针铁矿(Goethite)改性生物炭材料(Goethite@BC).比较了BC、Goethite和Goethite@BC对As(Ⅲ)的吸附特性,同时使用SEM-EDS、BET、FT-IR、XRD和XPS等技术对改性吸附剂的理化性质和吸附机制进行表征.结果表明,扫描电子显微镜分析显示有纳米级针铁矿附着在生物炭表面,可有效提高生物炭的比表面积和总孔容; 3种吸附剂对As(Ⅲ)的吸附符合伪二级动力学模型和Langmuir等温吸附模型,Goethite@BC对As(Ⅲ)的最大吸附量为65. 20 mg·g^(-1),与BC相比吸附量提高了62. 10倍. Goethite@BC吸附机制包括非特异性吸附(静电引力)和特异性吸附(配位、络合、离子交换等),纳米针铁矿颗粒在Goethite@BC表面对污染物的吸附起到重要作用. Goethite@BC在污染物修复领域具有很好地应用前景.

To improve the adsorption capacity of wheat biochar(BC) for arsenic(As),wheat stalks were selected as biomass to generate nano-sized goethite modified biochar(Goethite@ BC) by co-precipitation. The adsorption capacities of BC,Goethite,and Goethite@ BC for As(Ⅲ) were compared. The samples were analyzed by scanning electron microscopy(SEM) along with energy dispersive spectrometry(EDS),Brunauer-Emmett-Teller(BET),Fourier transform infrared(FT-IR),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS) techniques. The results showed that the nano-goethite coating was uniformly attached to the surface of the BC and improved the surface area and total pore volume of the biochar. The adsorption of As(Ⅲ) by the three adsorbents was proved to fit well with the pseudo-second-order kinetic model and the Langmuir model. Compared to BC,the Goethite@ BC increased the adsorption rate of As(Ⅲ) by 62. 10 times,and the maximum adsorption capacity of Goethite@ BC was 65. 20 mg·g^-1.The adsorption mechanism of Goethite@ BC included non-specific adsorption(electrostatic attraction) and specific adsorption(coordination,complexation,ion exchange,etc.),and nano-goethite particles on the Goethite@ BC surface played an important role in the adsorption of As. Goethite@ BC has a good application prospects in the field of environmental remediation.