高锰酸钾改性铁泥生物炭对镉砷的吸附特性

Adsorption Characteristics of Cd and As on Iron Sludge Biochar Modified by Potassium Permanganate

该文以铁泥(IS)为原料、高锰酸钾为改性剂,采用浸渍-热解法制备负载锰氧化物的新型零价铁生物炭(FMBC)。以Cd(Ⅱ)、As(Ⅲ)为目标污染物,通过批量吸附实验考察了pH、吸附时间和初始浓度对FMBC吸附效果的影响,结合XPS、FTIR、XRD等表征探究其吸附机理。结果表明,FMBC表面粗糙、孔隙结构及官能团丰富,零价铁和铁锰氧化物是FMBC的主要晶相。随着溶液初始pH的升高(2~6),FMBC对Cd(Ⅱ)的吸附率逐渐增加,p H<6时,As(Ⅲ)的吸附率变化不大。FMBC对Cd(Ⅱ)和As(Ⅲ)的吸附过程均以非均质的化学吸附为主,吸附Cd(Ⅱ)以多层吸附为主,吸附As(Ⅲ)以单层吸附为主,同时也存在不均匀表面的多层吸附。Cd(Ⅱ)和As(Ⅲ)的理论最大吸附量分别为95.34 mg/g和116.83 mg/g,较改性前提高了15.9%和39.18%。Cd(Ⅱ)主要通过共沉淀、络合反应、离子交换、氧化还原和阳离子-π作用吸附在FMBC上,As(Ⅲ)主要通过氧化还原、络合作用和离子交换被FMBC吸附。研究成果可为铁泥的资源化利用及Cd(Ⅱ)、As(Ⅲ)污染的处理提供科学依据和技术支持。

A new zero-valent iron biochar(FMBC)loaded with manganese oxides was prepared by the impregnation-pyrolysis method using iron sludge(IS)as raw material and potassium permanganate as modifier.The effects of pH,adsorption time and initial concentration on the adsorption effect of FMBC were investigated by batch adsorption experiments with Cd(Ⅱ)and As(Ⅲ)as the target pollutants,and the adsorption mechanism was explored by combining XPS,FTIR and XRD characterization.The results showed that the surface of FMBC was rough,rich pore structure and functional groups.Zerovalegnt iron and iron-manganese oxides were the main crystalline phases of FMBC.The adsorption rate of FMBC on Cd(Ⅱ)gradually increased with the increase of the initial pH of the solution(2~6),and the adsorption rate of As(Ⅲ)did not changed at pH<6.The adsorption processes of both Cd(Ⅱ)and As(Ⅲ)by FMBC are dominated by non-homogeneous chemisorption,and the adsorption of Cd(Ⅱ)is dominated by multilayer adsorption,and the adsorption of As(Ⅱ)is dominated by monolayer adsorption,while multilayer adsorption on inhomogeneous surfaces also exists.The theoretical maximum adsorption capacities of Cd(Ⅱ)and As(Ⅲ)were 95.34 mg/g and 116.83 mg/g,respectively,which were 15.9%and 39.18%higher than those before modification.Cd(Ⅱ)was mainly adsorbed on FMBC through co-precipitation,complexation reaction,ion exchange,redox and cation-r interaction,and As(Ⅲ)was mainly adsorbed by FMBC through redox,complexation and ion exchange.The research results can provide scientific basis and technical support for the resource utilization of iron mud and the treatment of Cd(Ⅱ)and As(Ⅲ)pollution.