Comparative assessment of Reactive Black 5 removal from aqueous solution using organically modified montmorillonite clays
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Date
2025
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Abstract
The discharge of synthetic dyes such as Reactive Black 5 (RB5) into aquatic environments poses a serious environmental
challenge due to their persistence, toxicity, and resistance to conventional wastewater treatments. In this study, organoclays
were synthesized by modifying natural montmorillonite clays originating from Algeria (Mnt A) and Germany (Mnt G)
using hexadecyltrimethylammonium bromide (HDTMA) and hydrochloric acid (HCl), aiming to enhance their adsorption
efficiency for RB5 removal. The clays were characterized using granulometry, XRD, FTIR, TGA-DTG, XRF, and zeta
potential analysis, confirming successful modification. Batch adsorption experiments showed rapid dye removal within
60 min, with optimal performance at pH 2, an initial dye concentration of 100 mg/L. Kinetic modeling revealed that the
adsorption process followed a pseudo-second-order model, while the equilibrium data were fitted to Langmuir, Freundlich,
and Temkin isotherm models. Among these, Langmuir provided the best fit, indicating monolayer chemisorption, with
Mnt AM exhibiting the highest adsorption capacity (113.4 mg/g) compared to Mnt GM (101.8 mg/g) and the raw montmorillonite.
Temkin
model
analysis
further
contributed
to
understanding
the
energy
distribution and
adsorbent–adsorbate
interactions.
Mechanistic
insights
indicated
that
the
unmodified
clays
relied
mainly
on
cation
bridging,
hydrogen
bonding,
and
van der Waals forces, while HDTMA-modified clays benefited from the additional electrostatic attraction, the hydrophobic
effects, and π–π stacking. These results underscore the potential of organoclays as efficient, reusable adsorbents
for textile wastewater remediation.