Abstract:
Hexavalent chromium (Cr(VI)) contamination in drinking water due to industrial
activities is a growing worldwide concern. Cr(VI) concentrations exceeding a few
parts per billion (ppb) can cause serious health problems such as asthma, blood
cancer, kidney-related diseases, liver and spleen damage, as well as neurological
system, immunological deficiencies, and reproductive issues. This study, thus,
explored the feasibility of employing a novel polymeric ferromagnetic
nanocomposite adsorbent made of low-cost, biodegradable, and ultrapermeable materials from pulp and paper sludge for adsorptive removal of
hexavalent chromium (Cr6+) from synthetic wastewater. Vibrating-sample
magnetometer (VSM), X-ray diffraction (XRD), scanning electron microscopy
(SEM), Brunauer-Emmet-Teller surface area (BET), and Fourier transform
infrared (FTIR) were used to analyze the produced nanocomposite adsorbent.
The Fourier transform infrared results confirmed the presence of adsorptive
peaks attributed to −OH, −NH2, and FeO. Scanning electron microscopy
micrographs revealed a porous adsorbent surface. XRD revealed the existence
of the crystalline spinel-structured magnetite (Fe3O4) phase of iron oxide, while
the saturation magnetization was established to be 26.90 emu/g. The
Brunauer–Emmett–Teller analysis confirmed a slight decrease in the surface
area of the nanocomposite adsorbent to 6.693 m2
.g−1
, compared to Fe3O4
(7.591 m2
.g−1
). The optimum conditions for Cr6+ removal were pH 2.0, 1.0 g/L
adsorbent dose, room temperature (25°C), 120 min contact time, and 20 mg/L
pollutant concentration. During removal, the Cr(VI) was adsorbed by electrostatic
attraction and/or reduced to trivalent chromium Cr(III). At low starting Cr(VI)
concentrations, chemisorption dominated the removal process, but as
concentrations increased, physisorption became more significant. The prepared nanocomposite adsorbent presented exceptional removal efficiency of
up to 92.23%, indicating that it may be useful for the adsorption of metal ions from
industrial and household wastewater.
KEYWORDS
adsorption, nanocomposite adsorbent, chromium (VI), equilibrium studies, co-existing
ions, wastewater treatment
