Magnetic separation and adsorptive performance for methylene blue of mesoporous NiFe2O4/SBA-15 nanocomposites

Chemical activation of cotton fibers with varied regents induces distinct morphology of activated carbon and adsorption capacity of methylene blue

Some biomasses like cotton contain natural fibrous structures. This is a desirable structural feature for exposure of adsorption sites on cotton-derived activated carbon (AC). This was verified herein by conducting activation of cotton with ZnCl2, H3PO4, K2C2O4, or KOH, probing whether structural transformation during activation could be confined inside a cotton fiber. The results indicated that ZnCl2 showed the highest capability for generating pores (1432.8 m2·g-1), especially mesopores (> 50 %). This resulted from its highest activity for catalyzing the aromatization reactions associated with deoxygenation during the activation (C/O of 13.1 versus C/O of ca. 3.6 for counterparts). The intensive cracking from the potassium activators interfered with aromatization, retaining more oxygen but diminished pore development (ca. 1000 m2·g-1), especially mesopores (< 7 %). Furthermore, ZnCl2 catalyzed condensation of intermediates bearing CO and C-O-C, but KOH or K2C2O4 could not. ZnCl2 activation retained the fibrous structure of resulting activated carbon but induced the merge of fiber with the help of the formed reactive carbon cation, while H3PO4 led to the full deformation of fibers. Reactive "fiber intermediates" could also form in activation with KOH but not with K2C2O4, as K2C2O4 only catalyzed the transformation of inner structures. This work supports cotton pretreatment and chemical activation as a promising technique for creating porous AC with high adsorption capacity.

Synthesis of calcium carbonate-loaded mesoporous SBA-15 nanocomposites for removal of phosphate from solution

Removal of phosphate from water is very crucial for protecting the ecological environment since massive phosphorus fertilizers have been widely used and caused serious water deterioration. Thus, we fabricated a series of calcium carbonate-loaded mesoporous SBA-15 nanocomposites with different Ca:Si molar ratio (CaAS-x) as phosphorus adsorbents via a simple wet-impregnation method. The multiply approaches including X-ray diffraction (XRD), N2 physisorption, thermogravimetric mass spectrometry (TG-MS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) were used to characterize the structure, morphology, and composition of mesoporous CaAS-x nanocomposites. The phosphate adsorption efficiency of the CaAS-x nanocomposites was studied through adsorption and desorption batch tests. Results showed that the increases of Ca:Si molar ratio (rCa:Si) improved the phosphate removal capacity of CaAS nanocomposites, especially CaAS with the optimum synthesis molar ratio of Ca:Si as 0.55 showed the high adsorption capacity of 92.0 mg·g-1 to high concentration of phosphate (> 200 mg·L-1). Note that the CaAS-0.55 had a fast exponentially increased adsorption capacity with increasing the phosphate concentration and correspondingly showed a much faster phosphate removal rate than pristine CaCO3. Apparently, mesoporous structure of SBA-15 contributed to high disperse of CaCO3 nanoparticles leading to the monolayer chemical adsorption complexation formation of phosphate calcium (i.e., =SPO4Ca, =CaHPO4-, and =CaPO4Ca0). Therefore, mesoporous CaAS-0.55 nanocomposite is an environmental-friendly adsorbent for effective removal of high concentration of phosphate in neutral contaminated wastewater.

Synthesis of Magnetic Short-Channel Mesoporous Silica SBA-15 Modified with a Polypyrrole/Polyaniline Copolymer for the Removal of Mercury Ions from Aqueous Solution

A novel magnetic short-channel mesoporous silica SBA-15 composite adsorbent was prepared by the copolymerization of pyrrole and aniline. The prepared novel nanoadsorbent polypyrrole-polyaniline/CoFe2O4-SBA-15 (PPy-PANI/M-SBA-15) has a significant adsorption effect on heavy metal mercury ions. The batch adsorption experiment was carried out to study the effects of various parameters including solution pH, initial concentration (C 0), adsorbent dose (dosage), temperature (T), and contact time on the adsorption effect. The analysis results of the response surface method (RSM) and central composite design (CCD) show that the importance for adsorption factors is pH > C 0 > T > dosage, and the maximum capacity of PPy-PANI/M-SBA-15 is 346.2 mg/g under the optimal conditions of pH = 6.7, T = 310 K, C 0 = 29.5 mg/L, and a dosage of 0.044 g/L. The pseudo-second-order kinetic model and the Langmuir isotherm model simulate the adsorption behavior of mercury ions. In addition, thermodynamic parameters indicate self-heating and reversible adsorption processes. A covalent bond is formed between the nitrogen-containing functional group and the mercury ions. Excellent magnetic properties and high reproducibility indicate that PPy-PANI/M-SBA-15 has excellent recyclability and environmentally friendly properties and can become a potential heavy metal ion adsorbent in practical applications.

A facile synthesis of metal ferrites and their catalytic removal of toxic nitro-organic pollutants

Nitrocompounds are the major prime water contaminants. In this investigative study, toxic nitrocompounds (4-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol) were removed by using magnetic CuFe₂O₄, CoFe₂O₄, and NiFe₂O₄ material systems. The metal ferrites were synthesized through hydrothermal method and also followed with calcination process. The properties of metal ferrites were confirmed through using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) studies and results there on were presented. For the first time, the synthesized CuFe₂O₄, CoFe₂O₄, and NiFe₂O₄ material systems were used for the reduction of 4-nitrophenol (NP), 2,4-dinitrophenol (DNP), and 2,4,6-trinitrophenol (TNP) in aqueous medium. The UV-visible spectrometry was employed to monitor the removal of nitro compounds and formation of aminophenol. Among, the three catalysts, the CuFe₂O₄ displayed excellent removal activity for nitrocompounds. The CuFe₂O₄ nanoparticles completely removed the NP, DNP and TNP within 2, 5, 10 min, respectively. The NP reduction reaction follows the pseudo-first-order kinetics. Further, the investigated and proposed CuFe₂O_4, catalyst has given and demonstrated excellent kinetic rate constants 0.990, 0.317, 0.184 min^-1 for 4-NP, DNP and TNP respectively, which was very fast kinetic than the already published reports. Also, the aminophenol formation was confirmed for the above mentioned and select nitrocompounds. The obtained results confirm suggest that CuFe₂O₄ nanoparticles based material system could be one of the promising catalysts for nitro compounds removal process.