A novel hydrogel bead [tannic acid
(TA)–poly(vinyl alcohol)
(PVA)/sodium alginate (SA)] with high strength prepared by biocompatible
PVA, TA, and biocompatible SA via an instantaneous gelation method
was applied to remove methylene blue (MB) from aqueous solution. The
obtained TA–PVA/SA hydrogel beads were fully characterized
by thermogravimetric analysis, Fourier-transform infrared spectroscopy,
X-ray photoelectron spectroscopy, scanning electron microscopy, and
so on. The adsorption performances of TA–PVA/SA hydrogel beads
for MB were investigated by changing the factors of TA content, initial
concentration, pH, adsorbent dosage, contact time, and temperature
systematically. The maximum capacity of TA–PVA/SA hydrogel
beads for MB removal was obtained to be 147.06 mg/g at 30 °C,
whose capability was better than that without TA. After fitting the
adsorbed data, it was basically consistent with the Langmuir isotherm
and pseudo-second-order kinetic model. Thermodynamic studies indicated
that MB removal was spontaneous and exothermic in nature. It is concluded
that the low-cost TA–PVA/SA hydrogel beads as an easily recoverable
adsorbent have a great potential on the removal of hazardous dyes
from wastewater.
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