Research Information System
9th IUPAC International Conference on Green Chemistry, Athens, Greece, 5 - 09 September 2022, pp.1, (Summary Text)
Pollution of water resources due to the discharge of industrial wastes is an important environmental problem.
Industrial wastewater contains large amounts of heavy metal ions and organic pollutants, which endanger human
health and the environment. For this reason, many studies have been carried out to remove heavy metals from
water. The adsorption process is widely used for the removal of heavy metals from wastewater due to its low
cost, applicability and environmental friendliness [1,2]. The efficiency of adsorption is heavily dependent upon
the choice of adsorbent. The required qualifications involve many chemical and structural properties such as
high mechanical and chemical stability, low cost, ease of regeneration and reuse, high surface area and befitting
porous structure and chemical functionality [2]. Chitosan, a cheap and sustainable natural polysaccharide with
high density of -NH2 and –OH functionalities, meets many of these demands with the exception of limited
physical stability in mildly acidic environment. Yet, physical and/or chemical modification procedures can be
used to alter solubility and improve adsorption capacity. To date, modified forms of chitosan, i.e cross-linked,
blended or as a composite component, have been synthesized and used in various adsorbent processes [3].
In this work, chitosan/polyvinyl alcohol blend beads synthesized by hydrothermal method were used in the
continuous adsorption process for Cr(VI) ions. In order to evaluate the efficiency and sustainability of the
process column and process parameters of bed height, initial concentration and flow rate were studied at
different levels. Additionally, the desorption efficiency and reusability of chitosan/polyvinyl alcohol beads were
investigated at three consecutive adsorption-desorption cycles.
For this purpose, 4 wt.% chitosan solution prepared in 4 % (v/v) acetic acid was blended with 10 wt.% PVA
solution in equal proportions. Gelling was achieved in 1.0 M NaOH solution for 24 hours. Beads were
transferred to a stainless-steel autoclave where hydrothermal treatment was performed at 140°C for 12 hours.
After drying the beads were utilized as the fixed bed adsorbent material for continuous Cr (VI) adsorption
experiments. The process parameters of flow rate, initial concentration and bed height were varied between 2 -6
mL/min, 25-75 ppm and 2.5-7.5 cm, respectively. Cr (VI) concentration of solutions was analyzed
spectrophotometrically at 540 nm. Data were used for the construction of breakthrough curves and modeling
studies were conducted using Thomas and Bohart-Adams models. Regeneration was studied in 0.1 M NaOH. All
experiments were conducted in triplicates and results were reported as the average. The structural properties of
beads were investigated using N2 adsorption (BET), scanning electron microscopy (SEM), Fourier transform
infrared (FT-IR) spectroscopy.
According to the results, highest removal efficiency was achieved at the lowest studied flow rate of 2 mL/min,
with 6 cm of bed height and 50 ppm initial Cr(VI) concentration. Both Thomas and Bohart-Adams models were
descriptive of the adsorption data with regression coefficients over 90%. The surface area of the blend beads
were determined as 2.96 m2
/g with overall pore volume of 0.35 cm3
/g.