Enzymatic and alkali pretreatments were
employed to improve nickel biosorption capacity of
Rhizomucor
pusillus
biomass. Pretreatment with 0.002–80 g l
-1
NaOH and 0.0001–0.1 Anson Unit (AU) g
-1 protease
enhanced the biosorption capacity of fungal biomass.
Increasing the concentration of NaOH from 0.002 to 5 g l
-1
improved nickel removal from 93.2 to 100.0 % while
untreated biomass showed 64.6 % Ni(II) removal. Pretreatment
with higher concentrations of NaOH, 5–80 g l
-1
resulted in nearly complete removal of nickel ions. Pretreatment
of the biomass with 0.0001 AU g
-1 protease
improved the nickel removal to over 91 %, while increasing
the enzyme loading to 0.1 AU g
-1 improved the removal to
93 %. Untreated biomass removed 78.4, 63.0, and 96.3 %of
chromium, copper, and lead ions, respectively, from a
mixture solution of the ions. Respective metal removals
were increased to 100, 98.9, and 100 % after pretreatment
with 0.2 g l
-1 NaOH solution and to 87.8, 86.7, and 100 %
after the enzymatic pretreatment with 0.1 AU g
-1 protease.
Scanning electron microscopy analysis indicated that alkali
and enzymatic pretreatments enhanced the porosity of the
biomass. Furthermore, compositional analysis showed that
both of the pretreatments removed a major part of fungal
proteins (2.1–95.8 % removal). Glucosamine,
N-acetyl
glucosamine, and phosphates were the major ingredients of
the pretreated biomass.