改性生物炭的光谱表征及砷的吸附效果研究

Spectroscopic characterization of modified biochar and its adsorption capability of arsenic

为了研究棉花秸秆生物炭的基本性质及其对砷的吸附效果,采用FeCl3·6H2O改性棉花秸秆生物炭,通过XRD、FT-IR和SEM等技术表征其光谱性能,并探究其对砷的吸附效果。结果表明:采用FeCl3·6H2O改性棉花秸秆生物炭后,生物炭的pH值、比表面积以及C、N、H元素的含量和C/N的比值随Fe含量的提高显著降低,灰分和O元素的含量以及H/C、O/C和(N+O)/C的比值随Fe含量的提高显著增加,生物炭表层Fe2O3和Fe3O4的含量增加。生物炭改性后缩短了吸附砷的平衡时间,吸附率高达73.4%,远高于未改性生物炭的吸附率(44.7%),吸附量高达7.63 mg/g,远高于未改性生物炭的吸附量(4.33 mg/g),且随Fe含量的提高,吸附率和吸附量均显著增加。其作用机制主要是通过改性生物炭静电吸附能力、离子交换和Fe^3+的还原作用降低水溶液中的As的含量,进而达到去除水溶液中As的目的。

In order to study the basic properties of cotton straw biochar and its adsorption effect of arsenic,the spectral properties of modified cotton straw biochar with FeCl3·6H2O was explored using XRD,FT-IR and SEM analysis,and its adsorption capability of arsenic(As)was investigated.The results show that pH value,specific surface area,contents of C,N,H elements and C/N ratio of the modified cotton straw biochar modified with FeCl3·6H2O significantly decreased with the increase of Fe content,whereas ash content and element O,H/C,O/C and(N+O)/C contents increased significantly with the increase of Fe content,as well as Fe2O3 and Fe3O4 contents on the surface of the modified cotton straw biochar.The balance time of arsenic adsorption was greatly shortened after the modification,and its adsorption rate was higher than 73.4%,far higher than that of the unmodified biochar(44.7%),with the adsorption capacity of 7.63 mg/g,which is much greater that of the unmodified biochar(4.33 mg/g).In addition,the adsorption rate and capacity significantly increased with the increase of Fe content.The adsorption mechanism behind these phenomena is that the electrostatic adsorption capacity of the modified biochar,ion exchange and the reduction of Fe^3+in the aqueous solution reduce the As content,which in turn reach the goal of As removal in the aqueous solution.