Functionalization of Synthesized Nanoporous Silica and Its Application in Malachite Green Removal from Contaminated Water
Bahman Hassan-Zadeh 1, Reza Rahmanian 1, Mohammad Hossein Salmani 2, Mohammad Javad Salmani 3*
1 Department of Chemical Technology, Iranian Research and Organization for Science and Technology, Tehran, Iran.
2 Environmental Science and Technology Research Center, Department of Environmental Health Engineering, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
3 DVM Student, Faculty of Veterinary Medicine, Shahid Bahonar University of Kerman, Kerman, Iran.
A R T I C L E I N F O |
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ABSTRACT |
ORIGINAL ARTICLE |
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Introduction: Nanoporous silica has received growing interest for its unique application potential in pollutant removal. Therefore, the development of a simple technique is required to synthesize and functionalize the nanoporous materials for industrial application.
Materials and Methods: The synthesis of nanoporous silica was investigated by the template sol-gel method, and it functionalized as an adsorbent for adsorption of malachite green. The morphology and structure of the prepared and functionalized nanoporous silica were studied using X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption-desorption technique. Subsequently, the effective parameters such as solution pH, contact time, and initial concentration on the adsorption process were optimized by adsorption tests.
Results: The results showed that high-order nanoporous silica had been produced with an average diameter of 20.12 nm and average pore volume of 1.04 cm3.g−1. It was found that the optimum parameters of pH, initial concentration and contact time for malachite green adsorption on nanoporous silica were 6.5, 10 mg.l-1, and 60 min, respectively. The experimental data confirmed the Freundlich model (R2 = 0.995) and the obtained kinetic data followed the pseudo-first-order equation. The maximum adsorption capacity calculated by Langmuir isotherm was found to be 116.3 mg.g-1.
Conclusion: The high adsorption capacity showed that the acid-functionalized nanoporous silica adsorbent can be used as an adequate adsorbent to remove malachite green from aquatic environments. The large surface area can be suggested that the silica nanoporous will have potential application prospects as the adsorbent. |
Article History:
Received: 15 February 2021
Accepted: 20 May 2021
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*Corresponding Author:
Mohammad Javad Salmani
Email:
mjsalmani80@Yahoo.com
Tel:
+983531492234
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Keywords:
Functionalization,
Malachite Green,
Water Pollution,
Silicon Dioxide. |
Citation: Hassan-Zadeh B, Rahmanian R, Salmani MH, et al.
Functionalization of synthesized nanoporous silica and its application in Malachite Green removal from contaminated water. J Environ Health Sustain Dev. 2021; 6(2): 1311-20.
Introduction
Porous materials are classified into three kinds: microporous (pore diameter less than 2 nm), mesoporous (pore diameters between 2 and 50 nm), and macroporous (pore diameters greater than 50 nm). The term nanoporous is applied for those porous materials with a diameter less than 100 nm. Porous solids, particularly nanoporous materials, are generally used as adsorbents, catalysts, and catalytic bases due to having a higher surface area 1, 2. Among these, the MCM-41, SAB-15, and HMS are some of the mesoporous materials with the ordered pore structures as certain forms (hexagonal-cylinder) widely used in catalytic processes 3. The SBA-type silica materials are usually synthesized in the presence of nonionic surfactants. These substances synthesized by the interaction of EOxPOyEOx block copolymer with silica minerals via hydrogen bonding are carried out under acidic conditions 4. The production is shown as S0(XI)0, where S is a surfactant with the zero electric charges, I is mineral spices, and x is a negative charge ion. Figure 1a illustrates the interaction of surfactant and the silica source in the presence of the ion-pair (H+ and Cl-). Figure 1b shows the structure of mesoporous SBA-15 and the hexagonal arrangement of its cavities, as well as the connection mode of major canals as to small lateral canals 5.
Figure 1: a) Interaction of surfactant and silica source b) the structure of mesoporous SBA-15
The most common methods for removing organic pollutants from wastewater are catalytic oxidation, photocatalytic oxidation, coagulation, and adsorption using activated carbon,
inexpensive adsorbents, and nano adsorbents 6-8. Among these methods, adsorption is regarded as a stable separation process and an effective manner for aquatic depollution. Low cost, high flexibility, easy design and composition, and high sensitivity to toxic substances in water purification and treatment make it surpass the other techniques. Moreover, it does not produce dangerous by products
9, 10. The key point in the removal of dyes using adsorbents is the providing of efficient and stable adsorbents. In recent years, porous adsorbents with high surface area, adsorption capacity, and large pore volume have been a remarkable growth
for the selective adsorption of cations and anions, organic compounds like dyes, aromatic hydrocarbons, and large organic molecules 11.
Malachite Green (MG) is a methylated diamino
-triphenylmethane dye that shows different colors in various pHs.
The chemical properties of MG are chemical formula: C23H25N2Cl, molecular weight: 364.91 g/mol, λmax: 618 nm. This substance is converted into cells to
leucomalachite, a cytotoxic and
carcinogenic pigment that can cause severe respiratory irritation. Mammals can be dangerously affected by 0.1 μg of MG in their bodies
12, 13. It has been found that this substance causes liver cancer in mice and reproductive abnormalities
in rabbits
. Direct contact with MG
can lead to DNA mutations 12. Malachite green has been banned since 1983 in food-related applications. Nevertheless, using MG
in the aquaculture industry as a fungicide agent and food additive for fish is very popular.
The utilization of mesoporous as an alternative adsorbent has many advantages, such as environmental friendliness, low cost, higher surface area, chemical stability, and a high potential for chemical modification
14-16. Depending on the target pollutants, mesoporous can be used as an adsorbent both in natural or modified form. Among the various types of mesoporous, silica is the most utilized material consisting of a functionalized group. The overall negative charge on the silica mesoporous by functionalized with organic materials is useful for the adsorption of cationic organic pollutants such as MG.
According to the importance of this subject throughout the world, a new method with high adsorption capacity for removal of MG was investigated in this study. The objective of the research work was to assess the ability of acid-functionalized mesoporous for the removal of MG dye from an aqueous solution. The influence of contact time, initial concentration, and aqueous solution pH was estimated. The experimental adsorption results were analyzed by different adsorption isotherm and kinetic models.
Materials and Methods
All reagents used were of analytical reagent-grade chemicals. The stock solution of the MG
dye was prepared by dissolving the laboratory-grade of MG (Merck, Germany) in deionized water. Dimethylformamide (DMF), silica, 3-aminopropyltriethoxysilane, pure succinic acid, and ethanol 95% were used to synthesize and functionalize nanoporous silica. The FT-IR analysis was performed by an EQUINOX 55BRUKER, and the concentration of MG in solution was done with a UV-1600 Light Ray spectrophotometer. Nitrogen adsorption-desorption (BET) was used to determine the type of porosity, specific surface area, pore-volume, and diameter of SBA-15 by Belsorp Mini II porosimeter. The measurements were performed in 77 ºK, and the sample was degassed at 300 ºC. Mesopour volume and diameter are calculated by Barrett- Joyner- Halenda (BJH) pore size distribution curve. Average pore diameter and total pore volume are determined by Brunauer- Emmett- Teller (BET) curve.
Synthesis of nanoporous SBA-15
First, 60 g of surfactant of poly (ethylene glycol) P123 was weighed and added in the 1.7 L of 0.2 N hydrochloric acids into a 3-liter beaker. To get a uniform mixture, the solution was stirred for 15 h via a shaker. It was then poured into a 4-liter glass reactor, and the container was washed with 400 ml of deionized water. It was heated at a fixed temperature of 40 °C for two h at a shaking speed of 53 RPM. Next, 127.5 g silica was added dropwise until it turned to a milky white after 20 min while the addition of silica was speeded up. The suspension was stirred at the same temperature for 24 h, continuously. After this time, the suspension was heated at the temperature of 100 °C for 48 h. Then, the residual was filtered and rinsed with water and ethanol. After drying, it was soxhlet with ethanol until all its surface surfactants were extracted. Then it was calcined in a furnace at the temperature of 600 °C for 6 h so that all surfactants oxidized and existed in the form of
CO
2 1.
Addition -COOH group
One gram of SBA-15 was dispersed in 25 ml of dry DMF. The amount of 0.2 g of succinic anhydride and 0.02 g of N,N
0 –dicyclohexylcarbodiimide (DCC) were separately prepared in the container containing 25 ml of DMF. Next, the solution containing SBA-15 was added dropwise into the solution containing succinic anhydride, which was well stirred on the shaker. After it, the solution was continuously stirred for 24 h. Then it was washed with DMF and ethanol, soxhlet with ethanol, and finally dried in the incubator
17.
Adsorption process
The adsorption process was carried out by batch mode in various pH and initial concentrations of MG at contact times with the adsorbent dose of 20 mg at the lab temperature of 22 ºC. After the adsorption process, the suspension was filtered, and the concentration of the remaining MG was measured by a UV spectrometer in the maximum wavelength of 618 nm. Then q
e was calculated using the equation 1as follow expression: