title: Effect of nanoscale zero-valent iron and magnetite (Fe3O4) on the fate of metals during anaerobic digestion of sludge.
abstract: Anaerobic digestion (AD) is one of the most widely used processes to stabilize waste sewage sludge and produce biogas renewable energy. In this study, two different iron nanoparticles [nanoscale zero-valent iron (nZVI) and magnetite (Fe3O4)] were used in the mesophilic AD processes (37 ± 1 °C) to improve biogas production. In addition, changes of heavy metal (Cd, Co, Cu, Zn, Ni and Cr) speciation during AD of sludge with and without iron nanoparticles have been investigated. Concentrations of metals in the initial sludge were as follows: 63.1, 73.4, 1102.2, 2060.3, 483.9 and 604.1 mg kg(-1) (dry sludge basis) for Cd, Co, Cu, Zn, Ni and Cr, respectively. Sequential fractionation showed that metals were predominantly bonded to organic matter and carbonates in the initial sludge. Compared with AD without iron nanoparticles, the application of iron nanoparticles (at dose of 0.5% in this study) showed positive impact not only on biogas production, but also on improvement of metals stabilization in the digestate. Metals were found concentrated in Fe-Mn bound and residual fractions and little was accumulated in the liquid digestate and most mobile fractions of solid digestate (water soluble, exchangeable and carbonates bound). Therefore, iron nanoparticles when properly used, could improve not only biogas yield, but also regulate and control the mobilization of metals during AD process. However, our study also observed that iron nanoparticles could promote the immobilization of phosphorus within the sludge during AD, and more research is needed to fully address the mechanism behind this phenomenon and the impact on future phosphorus reuse.
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Laboratory of Physical Chemistry, University of Abomey-Calavi, Benin, BP 4521, Cotonou, Benin.
authors.forename: Fidèle
authors.initials: F
authors.lastname: Suanon
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Sun
authors.affiliation: Laboratory of Applied Hydrology, University of Abomey-Calavi, Benin, Calavi, 01, BP 526, Cotonou, Benin; Laboratory of Inorganic Chemistry and Environment, University of Abomey-Calavi, Benin, BP 4521, Cotonou, Benin.
authors.forename: Daouda
authors.initials: D
authors.lastname: Mama
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
authors.forename: Jiangwei
authors.initials: J
authors.lastname: Li
authors.affiliation: Laboratory of Physical Chemistry, University of Abomey-Calavi, Benin, BP 4521, Cotonou, Benin; Beninese Center for Scientifics Research and Technologies (CBRST), 03 BP 1665, Cotonou, Benin.
authors.forename: Biaou
authors.initials: B
authors.lastname: Dimon
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address: cpyu@iue.ac.cn.
authors.forename: Chang-Ping
authors.initials: CP
authors.lastname: Yu
mesh_terms: D000693:Anaerobiosis; D005591:Chemical Fractionation; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D019216:Metals, Heavy / Q000378:metabolism*; D012722:Sewage / Q000032:analysis*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D019216:Metals, Heavy; D012722:Sewage; D007501:Iron; D052203:Ferrosoferric Oxide
keywords: Anaerobic digestion; Fractionation; Heavy metals; Magnetite; Nanoscale zero-valent iron; Sludge