Efficient aqueous molybdenum removal using commercial Douglas fir biochar and its iron oxide hybrids

Article Authors: Naba Krishna Das a 1, Chanaka M. Navarathna a 1, Jacinta Alchouron b, Beatrice Arwenyo a, Sharifur Rahman a, Brooke Hoffman a, Khiara Lee c, Sean Stokes a, Renel Anderson d, Felio Perez e, Dinesh Mohan f, Charles U. Pittman Jr. a, Todd Mlsna a


Molybdenum (Mo) is a naturally-occurring trace element in drinking water. Most commonly, molybdate anions (MoO42-) are in well water and breast milk. In addition, it is used in medical image testing. Recently, the EPA classified Mo as a potential contaminant, as exposure can lead to health effects such as gout, hyperuricemia, and even lung cancer. We have assessed the sorptive removal of aqueous molybdate using Douglas fir biochar (DFBC) and a hybrid DFBC/Fe3O4 composite containing chemically-coprecipitated iron oxide (Fe3O4). Adsorption was studied at various: pH values, equilibrium times (5 min-24 h), initial Mo concentrations (2.5–1000 mg/L), and temperatures (5, 25, and 40 °C) using batch sorption and fixed-bed column equilibrium methods. Langmuir capacities for DFBC and DFBC/Fe3O4 (at pH 3, 2 hrs equilibrium) were within 459.3–487.9 mg/g and 288–572 mg/g, respectively. These adsorbents and their Mo-laden counterparts were characterized by elemental analysis, BET, PZC, SEM, TEM, EDS, XRD, and XPS. MoO42- adsorption on DFBC is thought to be governed primarily via electrostatic attraction. Adsorption by DFBC/Fe3O4 is primarily governed by chemisorption onto magnetite surface hydroxyl groups, while electrostatics prevail in the DFBC-exposed phase. Stoichiometric precipitation of iron molybdates triggered by iron dissolution was also considered. The data suggest that DFBC and DFBC/Fe3O4 are promising candidates for molybdate sorption.

Bibliographical metadata

Journal Journal of Hazardous Materials
Volume 443
Related Faculties/Schools

aDepartment of Chemistry, Mississippi State University, MS 39762, USA
bUniversidad de Buenos Aires, Facultad de Agronomía, Departamento de Recursos Naturales y Ambiente, Cátedra de Botánica General, Av. San Martín 4453, C1417DSE, Buenos Aires, Argentina
cDepmartment of Biology, Tougaloo College, Tougaloo, MS 39174, USA
dBiochar Supreme Inc., Everson, WA 98247, USA
eMaterial Science Lab, Integrated Microscopy Center, University of Memphis, Memphis, Tennessee 38152, USA
fSchool of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India