The development of environmentally friendly adsorbents has been extensively carried out to overcome the
detrimental effects of heavy metal accumulation, which has persistently become a global ecological problem. In
pursuit of generating eco-friendly adsorbents, a green method for synthesizing thiamine functionalized-Fe3O4
(FT) was developed in this study. A one-step chemical oxidation and functionalization technique was used to
prepare FT using the ammonia-containing solvent. A molar ratio of ammonia:Fe:thiamine of 15:1:1 was shown to
produce FT15 with high yield, adsorptivity, and purity. XRD, XPS, FTIR, SEM, and SQUID characterization of
FT15 revealed the formation of superparamagnetic thiamine functionalized Fe3O4 in their particles. This
superparamagneticity facilitates the easy recovery of FT15 particles from the waste-containing solution by using
an external magnetic force. The batch adsorption of Cu(II) onto FT15 showed the best fit with the Sips adsorption
isotherm model with a maximum adsorption capacity of 426.076 mg g- 1, which is 5.69-fold higher capacity than
the control unmodified Fe3O4 (F15). After five adsorption-desorption cycles, the FT15 can maintain up to 1.95-
fold higher capacity than the freshly synthesized F15. Observation on the physicochemical properties of the postadsorption materials showed the contribution of an amine group, pyrimidine ring, and the thiazolium group of
thiamine in boosting its adsorption capacity. This study provides important findings to advance the adsorptivity
of magnetic adsorbents with promising recoverability from aqueous solution by employing naturally available
and environmentally friendly compounds such as thiamine.