Dye-containing industrial effluents
create major concern nowadays.
To address the problem, magnetic nickel oxide nanoparticles (NONPs)
were synthesized using the autopropagator combustion technique assisted
by sucrose as fuel and used for the removal of toxic malachite green
(MG) from water. The material was characterized by scanning electron
microscopy (SEM–EDS), Fourier-transform infrared spectroscopy
(FTIR), X-ray diffraction (XRD), vibrating sample magnetism (VSM),
point of zero charge (pH
ZPC
), and Brunauer–Emmet–Teller
surface area analysis. SEM images show flowerlike texture with the
presence of multiple pores. VSM reveals a well-defined hysteresis
at room temperature, confirming a permanent magnetic nature of the
material. pH
ZPC
was found to be 6.63, which enables dye
separation in the drinking water pH range. MG removal from water was
carried out in the batch mode with optimized physicochemical parameters
such as contact time, pH, temperature, and dose. Langmuir adsorption
capacity was estimated to be 87.72 mg/g. Pseudo-second order kinetics
(
R
2
= 0.999) and Langmuir isotherm model
(
R
2
= 0.997) were found to best fit. The
magnetic nature facilitates fast and quantitative separation of NONPs
from solution using a hand-held magnet. Dye-loaded NONPs can be easily
regenerated up to 89% and reused up to five cycles without significant
loss of activity. The mechanism of adsorption is proposed to be a
combination of electrostatic attraction and weak hydrogen bonding.
Strategically designed straightforward synthetic protocol, low cost,
high uptake capacity, and sustainable use render NONPs an ideal alternative
for future dye treatment.