Metilen mavisinin magnetik aktif karbon ile adsorpsiyonunun incelenmesi
Investigation of adsorption of methylene blue with magnetic activated carbon
Yazar: ZEYNEP AYDEMİR
Danışman: DOÇ. DR. ESRA ALTINTIĞ
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Ana Bilim Dalı / Anorganik Kimya Bilim Dalı
Derece: Yüksek Lisans, 2023
Konu: Kimya = Chemistry

Özet:
Bu çalışma da mısır koçanından elde edilmiş aktif karbon Fe3O4 ile modifiye edilerek
Fe3O4 -AK adsorbanı elde edildi. Öncelikle elde edilen Fe3O4 -AK adsorbanın yapısını
spesifik yüzey alanı (BET), Enerji Dağıtıcı X-ışını Spektroskopisi (SEM-EDX) ile
Taramalı Elektron Mikroskobu ve Fourier Dönüşümü Kızılötesi Spektroskopisi
(FTIR) gibi analiz teknikleri ile karakterize edildi. Fe3O4 -AK adsorbanı karakterize
edildiğin de sonuç olarak, partikül boyutunun küçük , yüzey alanın büyük ve
gözenekliliğe sahip adsorban olduğu görülmüştür. Metilen mavisi (MM) boyar
maddesinin giderimin de Fe3O4 -AK adsorbanı kullanılmıştır. Uygulanan deneysel
çalışma da karıştırma hızı, temas süresi, adsorban dozu, başlangıç konsantrasyonu ve
pH gibi çeşitli adsorban parametrelerinin etkileri incelenmiştir. Metilen mavisi (MM)
boyar maddesinin Fe3O4 -AK adsorban sulu çözeltilerinden uzaklaştırılması üzerinde
denge, termodinamik ve kinetik çalışmalar yapılmıştır. Çalışma da incelenen
parametreleri arasında ilk olarak çözelti pH'ı (2,0-9,0), adsorban miktarı (0,05-0,5 g L-
1) aralıkların da, sıcaklık (298-318 K) değerlerin de, temas süresi (5-180 dk) ve
konsantrasyon (50-500 mg/L-1) yer alır. Deneysel çalışmalar sonucun da en iyi verimin
pH 7,0 olduğu görülmüştür. Temas süresi incelendiğin de 30 dk ya kadar arttığı ve
daha sonra sabitlendiği görülmüştür. Kinetik modeller incelendiğin de Fe3O4 -AK
veriminin yalancı ikinci dereceden tepkimeye uygun olduğu görülmüştür.
Termodinamik olarak incelendiğin de ise ekzotermik olduğu görülmüştür. Fe3O4 -AK
adsorbanının Langmuir maksimum adsorpsiyon kapasitesi 312,8 mg /g-1 idi. Yeniden
kullanılabilirlik performansı çevre temizliği için önemli kriterlerden biridir.
Adsorpsiyon çalışması sekiz döngüden oluşmaktadır. İlk dört döngü sırasında
adsorpsiyon etkinliğinde sadece yaklaşık %15 azalma meydana geldi ve desorpsiyon
etkinliği neredeyse sabit olmasına rağmen, 8. döngüden sonra yaklaşık %27'ye ulaştı.
Ürettiğimiz adsorbenttin kapasitesindeki azalma, çevrim işlemi sırasında adsorpsiyon
bölgelerinin kısmen devre dışı kalmasından kaynaklanıyor olabilir. . Bu amacın
doğruluğu ve tutarlılığı yüksek olan bu işlemler için minimum maliyet ve emekle
sonuç alınması açısından literatüre farklı bir bakış açısı sağlayacağına inanıyoruz.
Sonuç olarak, geliştirilen Fe3O4 -AK adsorbentinin MM'nin sulu ortamdan
uzaklaştırılması sırasında pozitif bir yeniden kullanım performansı sergilediği açıkça
görülmektedir.

Abstract:
Colored wastewater containing dyes has a complex chemical structure. For this reason,
direct discharge into the recording environment without treatment can have harmful
effects on the environment. For this reason, such effluents with high dye content must
be treated with appropriate methods and discharged into the receiving environment.
Color removal can be achieved by the adsorption process, which is one of the
traditional treatment methods.
Recently, iron-fortified AC has been used as an alternative to other AC fortification
methods because of its benefits. Magnetization is one of the modal methods used to
combine AC and iron oxide to synthesize a recoverable magnetic AC adsorbent for
water/soil treatment purposes. Magnetic AC can be separated from the environment
using magnets and external magnetic fields. In this study, Fe3O4 -AC adsorbent was
obtained by modifying activated carbon with Fe3O4. AC/Fe3O4 obtained using the coprecipitation
method was synthesized using a mixture of Fe3+ and Fe2+ and activated
carbon. To synthesize AC/Fe3O4, 7.8 g FeCl3·6H2O was weighed, and 100 mL of
deionized water was added to it. A few drops of concentrated Fe(OH)3 were added to
prevent precipitation, then fish were thrown into it and placed on a magnetic stirrer,
and 3.9 g of it was added. It was heated by adding FeSO4·7H2O. At 70 °C, 3.3 g of AC
and 100 mL of 5 mol L-1 NaOH were added rapidly. After stirring for 120 min at 80°C,
this black mixture brought to room temperature was collected with the help of a
magnet. The obtained magnetic adsorbent was washed with distilled deionized water
and filtered with blue band filter paper. After washing with distilled water and ethanol
first, it was dried in an oven at 60 °C.
The structure of the Fe3O4 -AC adsorbent used was determined using the specific
surface area (BET), Energy Dissipative X-ray Spectroscopy (SEM-EDX) and
Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy (FTIR)
analysis data. The surface morphologies of the samples were made using JEOL-JSM-
6060LV Scanning Electron Microscopy (SEM). Multi-point Brunauer–Emmett–Teller
(BET) surface area (m2g-1), pore size (nm), micropore and Meso-macropore volumes
(cm3g-1) using surface and pore characterization device (Micromeritics ASAP 2020)
(SBET) analysis was determined by the nitrogen (N2) gas adsorption technique in a
liquid nitrogen environment at 77 K. Before the BET analysis, the temperature in the
degassing treatment applied to the sample was 300 °C and the time was 360 min.
XRD test was performed to determine whether the AC/Fe3O4 surface was crystalline
or amorphous before and after AC adsorption. However, after AC is converted to
AC/Fe3O4, the amorphous nature of crude AC is minimized. Two broad peaks are
observed in the AC XRD model at 2θ = 25◦ and 2θ = 43◦. When the Fe3O4 -AC
adsorbent was characterized, it was found to be a tubular adsorbent with small coil
size, large surface area. Fe3O4 -AC adsorbent is used for methylene blue (MB) dyestuff
removal. For the experimental study, firstly, 1000 mg/L stock MB solution was
prepared. Findings of mean pore diameter indicate the porous nature of AC and
AC/Fe3O4 (2.0 nm < pore size range<50 nm). This result explains that the increase in
the pore diameter is due to the AC/Fe3O4 adsorption capacity.
In allen experimentellen studien wurde reines wasser verwendet. The chemicals,
NaOH, HCI, Methylene Blue (MB)(M.F.=C16H18ClN3S3.H2O, M.W.=319.86 g/mol),
ethanol, FeSO4·7H2O, and FeCl3·6H2O with analytic grade were purchased from
Merck (Merck Co. Darmstadt, Germany). All chemicals used in the study are of
analytical grade and no further purification process has been performed.
The prepared MB stock solution was diluted with distilled water and calibration
solutions were prepared at concentrations of 1, 2, 3, 4, 5, 10 mg/L. The dyestuff
solutions to be used in the experiment were prepared as 50, 100, 150, 200 mg/L.
Application treatments also eliminate the effects of various adsorbent parameters such
as mixing speed, contact time, adsorbent dose, initial finishes and pH. Equilibrium,
thermodynamic and kinetic studies were carried out on the removal of methylene blue
(MB) dyestuff from Fe3O4 -AC adsorbent aqueous solutions. Adsorption experiments
were carried out in batch bath system. An MB stock solution was prepared at a
concentration of 1000 mg/ L-1. Standard solutions (1-5 mg /L-1) and working solutions
(50-500 mg/L-1) were prepared by diluting the stock solutions with deionized water
(chemical strength: 18 MΩ cm-1). 0.1 M NaOH or 0.1 M HCl solutions were used for
pH adjustment of MB solutions. After adsorption, the MB concentration in the solution
was measured in triplicate with a spectrophotometer (Shimadzu UV-Vis 1240) at a
wavelength of 665 nm. In experimental studies, contact time (5-150 min), initial MB
concentration (50-500 mg/ L-1), adsorbent dose (0.05-0.5 g/ L-1), initial pH values (2-
9), temperature (298 -318 K), contact time (5-180 min) were measured and optimum
values were determined. The experimental performance result is that the best yield is
pH 7.0. When the contact time was examined, it was noted that it stabilized after 30
minutes. Our study used pseudo-first- and pseudo-second-order models to understand
the kinetics behind MB subtraction and to analyze kinetic data. The experiment was
carried out in a 250 mL bottle by incorporating a mass of 0.1 g L-1 of AC/Fe3O4 in
100 mL of the aqueous solution of MB with an initial concentration of 100 mg L-1.
The pH was adjusted to 7.0 with constant stirring of the sample at 500 rpm and room
temperature (25 ± 2 °C). To determine the effect of contact time on adsorption,
AC/Fe3O4 (0.1 g) samples were made with 100 mL MB 100 mg L-1 solution.
In this study, using 0.1 g L-1AC/Fe3O4 activated carbon and 100 mL different initial
MB concentrations (50-500 mg L-1), isotherms should be used by revealing the
relationship between the equilibrium concentrations reached and the amount of
adsorbed substance per unit adsorbent. Modeling was done using Langmuir and
Freundlich isotherm model to show the relationship between MB amounts per
adsorbent unit.
When the kinetic models are examined, the pseudo-second properties of the Fe3O4 -
AC flow are suitable for the reaction. When examined thermodynamically, it was
found to be exothermic. The maximum adsorption capacity of Langmuir's Fe3O4 -AC
adsorbent was 312. 8 mg/g-1. Thermodynamic parameters show that the adsorption
process is endothermic in nature and is a spontaneous adsorption process.
Reusability performance is one of the important criteria for environmental cleanliness.
In the desorption process, a study was carried out for two different solvents, NaOH
and HCl, at five different temperatures. 0.1 g of Fe3O4 -AC was adsorbed and shaken
separately into 100 mL of 0.1-0.5 M NaOH and 0.1-0.5 M solutions at 298 K depthand 150 ppm playing speed for 60 minutes. MB desorption efficiency was investigated
using four different concentrated eluents: 0.1 M NaOH, 0.2 M NaOH, 0.1 M HCl, and
0.2 HCl. Desorption efficiency was determined as 73.42%, 78.7%, 89.16, %, and
98.56%, respectively. As can be seen from these results, the maximum desorption
efficiency was achieved by using 0.2 M HCI solution and therefore was selected as the
optimum eluent. Reusability performance is one of the important criteria for cleaning
processes. For the 0.2 M HCl eluent, the adsorption-desorption process was followed
and checked. Considering this important feature, an eight-cycle adsorption/desorption
process was performed to determine the reuse performance of the Fe3O4/AC adsorbent
for the removal of MB from the aquatic environment The adsorption study consists of
eight four. Only about 15% reduction in adsorption efficiency occurred during the first
four cycles and although the desorption efficiency was almost constant, it reached
about 27% after the 8th cycle. The decrease in the capacity of the adsorbent we
produced may be due to the partial deactivation of the adsorption sites during the
cycling process. As a result, it is clearly seen that the developed Fe3O4 -AC adsorbent
exhibits a positive reuse performance during the removal of MB from the aqueous
medium. An AC/Fe3O4 adsorbent has been effectively employed to remove MB
cationic dye from aqueous solutions. SEM/EDS, FTIR, and XRD results showed that
the composite was successfully prepared. Adsorption experiments showed that the
pseudo-second-order model provided the best description of the kinetic uptake
properties, while the adsorption results at equilibrium were explained by the Langmuir
model, where the maximum adsorption capacity (qmax) was 277.7 mg g-1.
Thermodynamic parameters show that the adsorption process is endothermic in nature
and is a spontaneous adsorption process.
The desorption process is the reverse of the adsorption process. In other words, it is
the situation where the particles adhering to the adsorbent surface are replaced by
another substance that can be adsorbed more strongly than themselves on the solid
surface and pass from the solid phase to the liquid phase or gas phase. In terms of the
parameters examined experimentally, the effect on each expenditure and adsorption
percentages was evaluated. Removing the methylene blue of the modified activated
carbon from the water also remains efficient. It is believed that the literature will
provide a different perspective in terms of obtaining results with minimum cost and
effort for these processes, which have high limitations and limitations of this purpose.
According to these results, it can be concluded that the prepared AC and
AC/Fe3O4adsorbent materials have a good potential for effective removal of MB from
aqueous solution due to some advantageous properties such as high surface area and
porosity, natural resource requirement and low cost.