High capacity aqueous phosphate reclamation using Fe/Mg-layered double hydroxide (LDH) dispersed on biochar

Sharifur Rahman; Chanaka M Navarathna; Naba Krishna Das; Jacinta Alchouron; Parker Reneau; Sean Stokes; Rooban V K G Thirumalai; Felio Perez; E Barbary Hassan; Dinesh Mohan; Charles U Pittman Jr; Todd Mlsna

doi:10.1016/j.jcis.2021.03.114

High capacity aqueous phosphate reclamation using Fe/Mg-layered double hydroxide (LDH) dispersed on biochar

J Colloid Interface Sci. 2021 Sep:597:182-195. doi: 10.1016/j.jcis.2021.03.114. Epub 2021 Mar 24.

Affiliations

¹ Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA.
² Universidad de Buenos Aires, Facultad de Agronomía, Departamento de Recursos Naturales y Ambiente, Cátedra de Botánica General, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina.
³ Department of Chemical Engineering, Louisiana Tech University, Ruston, LA 71272, USA.
⁴ Institute of Imaging and Analytic Technology (I(2)AT), Mississippi State University, Mississippi State, MS 39762, USA.
⁵ Material Science Lab, Integrated Microscopy Center, University of Memphis, Memphis, TN 38152, USA.
⁶ Department of Sustainable Bioproducts, Mississippi State University, Box 9820, Mississippi State, MS 39762, USA.
⁷ School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
⁸ Department of Chemistry, Mississippi State University, Mississippi State, MS 39762, USA. Electronic address: TMlsna@chemistry.msstate.edu.

PMID: 33866210
DOI: 10.1016/j.jcis.2021.03.114

Abstract

Phosphate is a primary plant nutrient, serving integral role in environmental stability. Excessive phosphate in water causes eutrophication; hence, phosphate ions need to be harvested from soil nutrient levels and water and used efficiently. Fe-Mg (1:2) layered double hydroxides (LDH) were chemically co-precipitated and widely dispersed on a cheap, commercial Douglas fir biochar (695 m²/g surface area and 0.26 cm³/g pore volume) byproduct from syn gas production. This hybrid multiphase LDH dispersed on biochar (LDHBC) robustly adsorbed (~5h equilibrium) phosphate from aqueous solutions in exceptional sorption capacities and no pH dependence between pH 1-11. High phosphate Langmuir sorption capacities were found for both LDH (154 to 241 mg/g) and LDH-modified biochar (117 to 1589 mg/g). LDHBC was able to provide excellent sorption performance in the presence of nine competitive anion contaminants (CO₃^2-, AsO₄^3-, SeO₄^2-, NO₃^-, Cr₂O₇^2-, Cl^-, F^-, SO₄^2-, and MoO₄^2-) and also upon remediating natural eutrophic water samples. Regeneration was demonstrated by stripping with aqueous 1 M NaOH. No dramatic performance drop was observed over 3 sorption-stripping cycles for low concentrations (5 ppm). The adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, TEM, and XPS. The primary sorption mechanism is ion-exchange from low to moderate concentrations (10-500 ppm). Chemisorption and stoichiometric phosphate compound formation were also considered at higher phosphate concentrations (>500 ppm) and at 40 °C. This work advances the state of the art for environmentally friendly phosphate reclamation. These phosphate-laden adsorbents also have potential to be used as a slow-release phosphate fertilizer.

Keywords: Adsorption; Biochar; Eutrophication; Layered double hydroxide; Phosphate.

MeSH terms

Adsorption
Charcoal
Hydroxides
Kinetics
Phosphates
Water
Water Pollutants, Chemical* / analysis

Substances

Hydroxides
Phosphates
Water Pollutants, Chemical
biochar
Water
Charcoal