TY - JOUR
T1 - Unraveling iron speciation on Fe-biochar with distinct arsenic removal mechanisms and depth distributions of as and Fe
AU - Xu, Zibo
AU - Wan, Zhonghao
AU - Sun, Yuqing
AU - Cao, Xinde
AU - Hou, Deyi
AU - Alessi, Daniel S.
AU - Ok, Yong Sik
AU - Tsang, Daniel C.W.
N1 - Funding Information:
We appreciate the financial support from the Hong Kong Environment and Conservation Fund (Project 101/2020 ) and Hong Kong Research Grants Council ( PolyU 15222020 ) for this study. We acknowledge the equipment support provided by the University Research Facility in Chemical and Environmental Analysis (UCEA) of the Hong Kong Polytechnic University.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/12
Y1 - 2021/12
N2 - Tailored manipulation of iron speciation has become a critical challenge for the further development of Fe-biochar as an economical and eco-friendly amendment for arsenic (As) immobilization. Herein, a series of Fe-biochars with manipulated iron speciations were fabricated by controlling the carbon structures and pyrolysis conditions. Results revealed that abundant labile-/amorphous-C induced more reductive-Fe(0) formation (10.9 mg g−1) in the Fe-biochar. The high Fe(0) content resulted in the effective As immobilization (4.34 mg g−1 As(V) and 7.72 mg g−1 As(III)) as evidenced by Pearson correlation coefficient (PCC) analysis. The hierarchical depth distributions of As and Fe on the Fe-biochar caused by the redox reaction and concomitant sorption of As proved the decisive role of Fe(0). An iron-oxide shell (~10–20 nm) with a high arsenic accumulation was revealed on the surface, while deeper within the particles, Fe(0) was found to be associated with elemental As (As(0), up to 19.4%). By contrast, pyrolysis with the stable-/graphitic-C generated more amorphous-Fe (61.9 mg g−1) on the Fe-biochar, which accounted for the high As removal (10.1 mg g−1 As(V) and 7.70 mg g−1 As(III)) despite the limited Fe(0) content. In comparison to the reductive Fe(0), distinct depth distribution was observed that the As/Fe ratio was marginally changed within 200 nm depth of the amorphous-Fe biochar after As decontamination. Co-precipitation of As with Fe released from amorphous-Fe contributed to this depth distribution, as evidenced by the high correlation between released-Fe and As immobilization capacity (PCC as 0.84–0.95). This study unveiled a crucial role of iron speciation on distinct mechanisms for As removal, guiding the application-oriented design of multifunctional Fe-biochar for broad environmental remediation.
AB - Tailored manipulation of iron speciation has become a critical challenge for the further development of Fe-biochar as an economical and eco-friendly amendment for arsenic (As) immobilization. Herein, a series of Fe-biochars with manipulated iron speciations were fabricated by controlling the carbon structures and pyrolysis conditions. Results revealed that abundant labile-/amorphous-C induced more reductive-Fe(0) formation (10.9 mg g−1) in the Fe-biochar. The high Fe(0) content resulted in the effective As immobilization (4.34 mg g−1 As(V) and 7.72 mg g−1 As(III)) as evidenced by Pearson correlation coefficient (PCC) analysis. The hierarchical depth distributions of As and Fe on the Fe-biochar caused by the redox reaction and concomitant sorption of As proved the decisive role of Fe(0). An iron-oxide shell (~10–20 nm) with a high arsenic accumulation was revealed on the surface, while deeper within the particles, Fe(0) was found to be associated with elemental As (As(0), up to 19.4%). By contrast, pyrolysis with the stable-/graphitic-C generated more amorphous-Fe (61.9 mg g−1) on the Fe-biochar, which accounted for the high As removal (10.1 mg g−1 As(V) and 7.70 mg g−1 As(III)) despite the limited Fe(0) content. In comparison to the reductive Fe(0), distinct depth distribution was observed that the As/Fe ratio was marginally changed within 200 nm depth of the amorphous-Fe biochar after As decontamination. Co-precipitation of As with Fe released from amorphous-Fe contributed to this depth distribution, as evidenced by the high correlation between released-Fe and As immobilization capacity (PCC as 0.84–0.95). This study unveiled a crucial role of iron speciation on distinct mechanisms for As removal, guiding the application-oriented design of multifunctional Fe-biochar for broad environmental remediation.
KW - Arsenic immobilization
KW - Co-precipitation
KW - Engineering biochar
KW - Green and sustainable remediation
KW - Iron transformation
KW - Redox reaction
UR - http://www.scopus.com/inward/record.url?scp=85112433548&partnerID=8YFLogxK
U2 - 10.1016/j.cej.2021.131489
DO - 10.1016/j.cej.2021.131489
M3 - Journal article
AN - SCOPUS:85112433548
SN - 1385-8947
VL - 425
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
M1 - 131489
ER -