Adsorption of Pb (II) ions from water using magnetically modified biochars obtained from microwave-assisted pyrolysis

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University of New Brunswick
In this study, biochars were produced from biomass at pilot scale in a microwave-assisted pyrolysis process. These pyrolyzed biochars were magnetically modified to improve their adsorption performance and facilitate the recovery of the spent biochars from solution. The magnetic chars were investigated as a potential renewable bio-sorbents for removing lead ions from aqueous solution in a batch-mode experiment. The biochar samples from microwave pyrolysis of 1.5 kg hemp stalks and maple wood chips biomass at a temperature range of 500–700 ˚C were first impregnated with H[subscript 2]O[subscript 2] (30%) solution and then magnetized by mixing aqueous Fe[superscript 3+]/Fe[superscript 2+] solution with biochar suspensions, followed by NaOH treatment. The synthesized magnetic adsorbents were characterized. The effects of temperature, pH, dosage, contact time and initial concentration of Pb (II) solution on adsorption were examined. Adsorption kinetics and isotherm of the modified biochars were modelled and their adsorption performance after 5 regeneration cycles quantified. The adsorbents recovery from solution with a low magnetic field was investigated. The prepared magnetic biochars demonstrated a potential as renewable adsorbents in treating lead ions-contaminated water. Keywords: Microwave-pyrolysis; Magnetic biochar; hemp; maple; adsorbent; water treatment; heavy metal ions.