磁性氧化铁/桑树杆生物炭的制备及其对砷污染土壤溶解性有机碳和砷形态的影响

Preparation of Magnetic Iron Oxide/Mulberry Stem Biochar and Its Effects on Dissolved Organic Carbon and Arsenic Speciation in Arsenic-Contaminated Soils

以桑树杆为原料,制备了原始桑树杆生物炭(M-BC)及磁性氧化铁/桑树杆生物炭(Fe-BC)并对其进行表征.通过土壤培养实验,研究了3个温度下炭化制备的Fe-BC和M-BC在不同培养时间对土壤浸出液溶解性有机碳(DOC)和土壤砷(As)形态等的影响.结果表明:①Fe-BC负载的铁氧化物主要为Fe_(3)O_(4),且有磁性,主要官能团有C=O双键、O—H键、C—O键和Fe—O键;Fe-BC-400、Fe-BC-500和Fe-BC-600的pHzpc分别为8.92、8.74和9.19,比表面积分别为447.412、482.697和525.708 m^(2)·g^(-1).②土壤浸出液中ρ(DOC)随着M-BC和Fe-BC炭化温度的升高而分别降低11.6~315.6 mg·L^(-1)和78~365.6 mg·L^(-1),土壤浸出液中DOC浓度与土壤电导率(EC)值呈负相关;在培养第35 d,添加Fe-BC-600的土壤浸出液中As浓度比对照组土壤浸出液中的降低了55.96%.土壤浸出液中As浓度与DOC浓度相关性不显著.③添加Fe-BC的土壤有效态As占比均低于对照组的,在培养第35 d时,Fe-BC-600可使土壤有效态As占比降低39.21%.④在培养第35 d时,添加M-BC的土壤残渣态As含量减少了17.76%~49.11%,添加Fe-BC-600的土壤残渣态As占比增加了80%.Fe-BC-600最有利于降低土壤溶液DOC浓度,提高残渣态As含量,从而降低土壤As生物有效性.研究可为磁性氧化铁/生物炭在砷污染土壤修复提供理论依据.

In this study,original mulberry-biochar(M-BC)and magnetic iron oxide/mulberry stem biochar(Fe-BC)materials were prepared and characterized using mulberry stems as the raw material.The effects of carbonized temperature of Fe-BC and M-BC on dissolved organic carbon(DOC)and arsenic(As)speciation in soil leaching solutions were studied using soil incubation experiments.The results showed that:①Fe-BC was mainly composed of Fe_(3)O_(4)and was magnetic,and the main functional groups were a C=O double bond,O-H bond,C-O bond,and Fe-O bond.The point of zero charge values(pHzpc)of Fe-BC-400,Fe-BC-500,and Fe-BC-600 were 8.92,8.74,and 9.19,respectively,and the specific surface areas of Fe-BC-400,Fe-BC-500,and Fe-BC-600 were 447.412,482.697,and 525.708 m^(2)·g^(-1),respectively.②With the increase in the carbonization temperature of M-BC and Fe-BC,theρ(DOC)of soil leaching solution decreased 11.6-315.6 mg·L^(-1)and 78-365.6 mg·L^(-1),respectively.The DOC concentration of soil leaching solution was negatively correlated with soil EC.On day 35 of the incubation experiments,compared with that in soil after incubation without biochar(control),the As concentration of the soil leaching solution with Fe-BC-600 decreased by 55.96%,and there was no significant correlation between the As concentration of the soil leaching solution and the DOC concentration of the soil.③The available As concentration on day 35 in soil after incubation with Fe-BC was lower than that of the control group;the available As concentration on day 35 in soil incubated with Fe-BC-600 was reduced by 39.21%.④The residue As concentration on day 35 in soil incubated with M-BC decreased by 17.76%-49.11%.The residue As content on day 35 in soil incubated with Fe-BC-600 increased by 80%.Fe-BC-600 was most beneficial to reduce the DOC concentration and the available As content in soil leaching solution and increased the residue As content,thus reducing the bioavailability of soil arsenic.Therefore,this study can provide a theoretical basis for magnetic iron oxide/biochar remediation in arsenic-contaminated soil.