硅改性生物炭吸附水中Cd(Ⅱ)机理的量化分析

Quantitative analysis on the adsorption of Cd(Ⅱ) by silicon-modified biochar in aqueous solutions

以纳米二氧化硅为硅源制备硅改性生物炭,利用吸附动力学、吸附等温线及SEM-EDS、XRD、FTIR、XPS等表征研究硅改性生物炭对水中Cd(Ⅱ)的吸附机理,并定量分析各种吸附机制的贡献率.结果表明,当添加SiO2质量比为0.5%时制备的生物炭(0.5SiBC)吸附Cd(Ⅱ)效果最佳,最大吸附量为132.64 mg·g^(-1),是未改性生物炭(BC)的1.56倍;0.5SiBC对Cd(Ⅱ)吸附过程符合拟二级动力学和Freundlich模型,其吸附过程属于化学吸附;XRD、FTIR和XPS等结果表明,0.5SiBC吸附Cd(Ⅱ)的机理主要有矿物质沉淀、离子交换作用和络合作用,各种机理贡献率依次为:矿物质沉淀(46.61%)>离子交换(33.79%)>其他机理(18.36%)>络合作用(1.24%);0.5SiBC对Cd(Ⅱ)的离子交换和矿物质沉淀量比BC分别提高133.80%和41.46%,硅改性主要通过提高生物炭的离子交换和矿物质沉淀能力来提高吸附Cd(Ⅱ)的能力.研究表明,硅改性生物炭作为去除水溶液中Cd(Ⅱ)的吸附剂具有较好的应用前景.

Silicon-modified biochar was prepared with nano silica as a silicon source.The adsorption of Cd(Ⅱ)by silicon-modified biochar in aqueous solution was studied to explore the adsorption kinetics,adsorption isotherm,trhough material characterization and quantitative analysis of various adsorption.The results show that when the mass ratio of SiO2is 0.5%,the prepared biochar(0.5SiBC)presents the best adsorption performance on Cd(Ⅱ),and the maximum adsorption capacity reaches 132.64 mg·g^(-1),which is 1.56 times higher than the capacity of the unmodified biochar(BC).The adsorption process of Cd(Ⅱ)by 0.5SiBC conforms to pseudo second-order kinetics and the Freundlich model,and this process is characterized as chemical adsorption.The results of XRD,FTIR,and XPS demonstrate that the adsorption mechanisms of Cd(Ⅱ)by 0.5SiBC mainly include mineral precipitation,ion exchange,and complexation.The contribution rates of various mechanisms are ordered from the biggest to the smallest contribution as follows:mineral precipitation(46.61%),ion exchange(33.79%),other mechanisms(18.36%),and complexation(1.24%).The ion exchange and mineral precipitation of Cd(Ⅱ)by 0.5SiBC were 133.80%and 41.46%higher than the one of BC,respectively.Silicon modification mainly improves the adsorption capacity of Cd(Ⅱ)by improving the ion exchange and the mineral precipitation capacity of biochar.The result of this work shows that silicon-modified biochar presents great potential as an adsorbent for removing Cd(Ⅱ)from aqueous solutions.