Thiswork explores the potential of crab (Portunus sanguinolentus) shell particles for the removal of manganese(II)
and zinc(II) ions fromaqueous solutions. The removal of metal ions by crab shell was found to be pH dependent,
with optimum sorption occurring at pH 6 for both Mn(II) and Zn(II). The mechanism of metal removal by crab
shellwas identified asmicro-precipitation ofmetal carbonates followed by adsorption onto chitin at the surface of
crab shell, which was confirmed by pH edge and EDX analysis. The process of metal biosorption was rapid (90%
removal in 120 min forMn(II) and 90% removal in90 min for Zn(II)) at an initialmetal concentration of 500 mg/L.
Modeling results revealed that Mn(II) and Zn(II) kinetics data were successfully described using pseudo-first
and -second ordermodels, compared to the Elovich equation. Furthermore, isothermexperiments revealed that
crab shell possesses high uptake capacities of 69.9 and 123.7 mg/g forMn(II) and Zn(II), respectively, according to
the Langmuirmodel. Possibility of desorption and subsequent reuse of crab shellwas attempted using 0.1 MHCl
as elutant and the results were successful with the elutant exhibiting more than 99% elution efficiency for both
Mn(II) and Zn(II).