Synthesis and adsorption characteristics of an heterogenized manganese nanoadsorbent towards methyl orange
Graphical abstract
Introduction
Pollution of the biosphere with toxic dyes and metals has increased dramatically since the beginning of the industrial revolution, and water contamination by the disposal of effluents including organic and inorganic has become worldwide concern for the past few decades [1], [2].
The presence of dye and heavy metal over permissible levels in drinking water may cause adverse effect on human physiology. Industrial wastewaters are important source of environmental pollution due. Dye and metals are toxic, non-biodegradable, can be incorporated relatively easy in the food chain, and tend to accumulate causing several diseases and health disorders in humans, and other living organisms [3], [8].
Several conventional methods that have been reported to eliminate dye and heavy metal ions from various industrial effluents usually comprise chemical precipitation, flocculation, membrane separation, ion exchange, and evaporation, and are often costly, especially in removing heavy metal ions from dilute solutions. Adsorption is considered quite attractive in terms of its efficiency of removal from dilute solutions [3], [4], [5], [6], [7], [8], [9], [10].
Nanoparticles of a variety of shapes, sizes and compositions are changing nowadays the wastewater treatments [4], [11], [12], [13], [14], [15]. Preparation and investigation of novel nano materials is important in martial science. There are various nano-materials including carbon nanotubes, nano-wires and nano-particles those are important for scientific works. The nanostructures with large specific surface area and ease with which they could be immobilized onto solid support and the ability to functionalize with different functional active sites to increase their affinity towards target compounds, could provide an important and feasible platform for catalysis, separation, sensing, and fuel cells. Derivatization of inorganic solids with organic functional groups was widely studied and successfully applied in many divergent areas of research. It is essential to look for a new method with high sensitivity, simplicity and efficiency for the removing of methyl orange from aqueous media (Table 1). Inorganic supports offer several advantages with respect to activated carbon, agricultural waste and chitosan including better mechanical stability and a higher concentration of chelating groups on the surface, and they are often much cheaper than their organic counterparts. Therefore, parallel to the efficient activity and environmentally friendly aspect, economic cost can also determine whether a new system can be used to the environment or not. Because of cheap, easy synthesis in large quantities, chemical and thermal stability [16], [17], [19], [20]; the immobilized Schiff base complexes have important potentials for the removal of dyes from aqueous solution.
Here, we have demonstrated the application of a stable covalently immobilized Mn nanoparticles on the surface of SiO2–Al2O3 mixed-oxides host by a linker approach and studied the application of heterogenized Mn ions as an nano-adsorbent for capturing of methyl orange (MO) from aqueous solution. Furthermore, the high content of Mn(III) ion allows chemical modification of SiO2–Al2O3 mixed oxides in order to improve the adsorbent properties, such as selectivity and adsorption capacity. Reasons for choosing SiO2–Al2O3 mixed oxides include low thermal expansion and conductivity, low dielectric constant, excellent creep resistance, robust chemical and thermal stability, good high temperature strength, and oxidation resistance. However, the chemistry of manganese has received considerable attention due to the fact that manganese is believed to be catalytically active in a variety of metalloenzymes, that is, manganese is one of the most versatile metals, playing a central catalytic role in the environment. The structures of the obtained organometallic-modified Si–Al mixed oxides was confirmed by elemental analysis, BET (N2 adsorption–desorption technique), FT-IR spectroscopy, SEM, TEM, ICP–MS, and EPR.
Section snippets
Materials and preparation of the organometallic functionalized SiO2–Al2O3 mixed-oxide
All reagents (A.R.) were purchased from Merck and were used without further purification, except that solvents were treated according to standard methods.
The SiO2–Al2O3 used in this work was synthesized according to a sol–gel method [10]. The SiO2–Al2O3-supported 2-aminoethyl-3-aminopropyl-trimethoxysilane (2-AE-3-APTMS) was prepared by refluxing 5.2 g SiO2–Al2O3 that was activated at 550 °C for 6 h under air with 0.0195 mol of 2-AE-3-APTMS in dry dichloromethane (100 mL) for 24 h. The solid was
Results and discussion
The structures of the obtained organometallic-modified Si–Al mixed oxides was confirmed by elemental analysis, BET (N2 adsorption–desorption technique), FT-IR spectroscopy, SEM, TEM, ICP–MS, and EPR. Nitrogen sorption measurements of the modified Si/Al mixed oxides confirm the presence of the MnNPs attached to the modified Si/Al mixed oxides (Table 2). The considerable decrease in the specific surface area (SBET) clearly indicates functionalization of the surface of the mixed oxides with
Conclusion
A nanocomposite for the removal of methyl orange from aqueous solution was synthesized by the immobilization of MnNP on the SiO2/Al2O3, prepared from a sol–gel method. The operating parameters, pH of solution, contact time, and temperature, were effective on the removal efficiency of methyl orange. Equilibrium isotherms have been measured experimentally and analyzed by various equation isotherm models. The Langmuir–Freundlich isotherm equation was found to best represent the experimental
Acknowledgment
Thanks are due to the Iranian Nanotechnology Initiative for supporting of this work.
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