Catalytic wet peroxide oxidation of phenol through mesoporous silica-pillared clays supported iron and/or titanium incorporated catalysts.

Catalytic performances of Silica Pillared Clay (SPC) supports synthesized in different silica amounts both from standard SWy-2 clay mineral and Hançili region bentonite rock (HWB), and iron (Fe) and/or titanium (Ti) incorporated SPCs in different combinations were evaluated in various advanced Catalytic Wet Peroxide Oxidation (CWPO) of phenol. Host clay mineral type led to different oxidation performances and metal loading created significant increases in the catalytic performance. CWPO performance of Fe-loaded SPCs was better than Ti-loaded ones, so oxidation parameters for Fe-SPCs were studied in detail. Catalyst amount and rise in temperature increased phenol conversion values significantly, and catalysts were more effective in lower pH reaction medium. Aromatic intermediates such as catechol, hydroquinone and benzoquinone formed at the beginning of oxidation were oxidized to carboxylic acids with an advancing oxidation time. The presence of carboxylic acids such as oxalic and formic acid resulted in relatively low total organic carbon (TOC) conversion values. The highest catalytic activity was obtained with high silica content Fe-SPCs synthesized with both host clays. Complete conversion was nearly achieved within 60 min with an experimental condition of T = 30 °C, pH = 3.7 and catalyst/solution ratio = 2 g/L for SWy-2 based catalyst by applying either CWPO or PCWPO (Photo Catalytic Wet Peroxide Oxidation) techniques. SCWPO (Sono Catalytic Wet Peroxide Oxidation) technique also yielded this value at the same oxidation conditions for HWB based catalyst. TOC conversion values at 240 min oxidation time were determined as 33% and 48% for SWy-2 based catalyst with CWPO and PCWPO techniques, respectively, and 37% for HWB based catalyst with SCWPO technique. SWy-2 based catalyst still retained its performance after 3 cycles.

Efficient removal of anti-inflammatory from solution by Fe-containing activated carbon: Adsorption kinetics, isotherms, and thermodynamics.

This work developed an innovative activated carbon (ICAC) derived from orange peels (OP) through chemical activation using FeCl3. The traditional activated carbon (PCAC) that was prepared through K2CO3 activation served as a comparison. Three adsorbents (ICAC, PCAC, and OP) were characterized by various techniques, these being: Brunauer-Emmett-Teller (BET) surface area analysis, thermo-gravimetric analysis, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. They were applied to remove diclofenac from aqueous solution applying batch experiments, in order to investigate the characteristics of adsorptive kinetics, isotherms, and thermodynamics. Results indicated that the SBET values were in the following order: 457 m2/g (PCAC) > 184 m2/g (ICAC) > 3.56 m2/g (OP). The adsorption process reached a fast equilibrium, with activating energies being 27.6 kJ/mol (ICAC), 16.0 kJ/mol (OP), and 11.2 kJ/mol (PCAC). The Langmuir adsorption capacities at 30 °C exhibited the decreasing order: 144 mg/g (ICAC) > 6.44 mg/g (OP) > 5.61 mg/g (PCAC). The thermodynamic parameters demonstrated a signal dissimilarity between biosorbent (ΔG° <0, ΔH° <0, and ΔS° <0) and activated carbon samples (ΔG° <0, ΔH° >0, and ΔS° >0). The presence of iron (FeOCl, γ-Fe2O3, and FeOOH) on the surface of ICAC played a determining role in efficiently removing diclofenac from solution. The excellent adsorption capacity of ICAC toward diclofenac resulted presumably from the contribution of complicated adsorption mechanisms, such as hydrogen bonding, ion-dipole interaction, π-π interaction, pore filling, and possible Fenton-like degradation. Therefore, FeCl3 can serve as a promising activating agent for AC preparation with excellent efficiency in removing diclofenac.

Chitosan-based film incorporated with silver-loaded organo-bentonite or organo-bentonite: Synthesis and characterization for potential food packaging material.

Biopolymer-clay composite films were synthesized and characterized for food packaging material. The synthesis was conducted in two stages. Cetrimonium bromide-modified bentonite (CTAB-bentonite) was first exchanged with Ag ions to obtain Ag-CTAB-bentonite. Biopolymer-clay composite films were then performed by a solution-casting method between chitosan (biopolymer) and Ag-CTAB-bentonite or between chitosan and CTAB-bentonite. Different weights of CTAB-bentonite (3% and 5% wt.) and Ag-CTAB-bentonite (3% and 5% wt.) were used during the second stage. The resultant films were characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscope coupled with energy dispersive X-ray spectroscopy, atomic force microscopes, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, optical measurement, and others (moisture content, swelling behavior, water solubility, antibacterial, shredded carrot preservation, and biodegradability). Results indicated that the properties (thermal stability, thermomechanical ability, UV-visible light barrier, shredded carrot preservation) of the chitosan-based film incorporated with the synthesized composites were enhanced compared to those of the CS film. The CS/(CTAB-bentonite)-3% and CS/(Ag-CTAB-bentonite)-3% films exhibited antibacterial properties against Escherichia coli, Salmonella enterica subp. enterica, Staphylococcus aureus, and Listeria monocytogenes. The chitosan-based film reinforced with the two prepared composites can be potential for food preservation and packaging.

Important role of pore-filling mechanism in separating naproxen from water by micro-mesoporous carbonaceous material.

Commercial micro-mesoporous carbonaceous material (MCM; 56.8% mesopores) was applied for investigating the removal phenomenon of naproxen drug in aqueous solutions through batch adsorption experiments. Results demonstrated that the adsorption capacity of MCM to naproxen was slightly affected by different pHeq (2.0-11) and ionic strength (0-1 M NaCl). Adsorption kinetics, isotherms, thermodynamics, and mechanisms were evaluated at pH 7.0. Adsorption kinetics indicated the rate constants for adsorption (0.2 × 10-3  L/(mg × min) and desorption (0.076/min) and the adsorption equilibrium constant (2.6 × 10-3  L/mg). Adsorption isotherm showed that MCM exhibited a high-affinity adsorption capacity to naproxen (even at low concentrations) and its Langmuir maximum adsorption capacity (Qmax ) was 252.7 mg/g at 25°C. Adsorption thermodynamics proved that the adsorption process was endothermic and physisorption (ΔH° = 9.66 kJ/mol). The analysis result of pore size distribution demonstrated that the internal pore structure of MCM was appropriate for adsorbing naproxen molecules. Pore-filing mechanism (pore diffusion phenomenon) was confirmed by a considerable decrease in BET-surface area (585 m2 /g) and total pore volume (0.417 cm3 /g) of MCM after adsorbing naproxen (~1000 mg/L and pH 7.0) at 5 min (341 and 0.256), 60 min (191 and 0.205), 120 min (183 and 0.193), 360 min (144 and 0.175), and 24 h (71.6 m2 /g and 0.123 cm3 /g, respectively). The pore diffusion occurred rapidly (even at the initial adsorption period of 5 min). The FTIR technique was applied to identify the existence of C-H···π and n-π interaction. π-π interaction (evaluated through ID /IG ratio and C=C band) played a minor contribution in adsorption mechanisms. The ID /IG ratio (determined by the Raman technique) of MCM before adsorption (1.195) was similar to that after adsorption (1.190), and the wavenumber (C=C band; its FTIR spectrum) slightly shifted from 1638 to 1634 cm-1 after adsorption. A decrease in the Qmax value of MCM from 249 to 217 (H2 O2 -oxidized MCM) or to 224 mg/g (HNO3 -oxidized MCM) confirmed the presence of π-π interaction. Electrostatic attraction was a minor contribution. MCM can serve as a promising material for removing naproxen from water environment through a pore-filling mechanism. PRACTITIONER POINTS: Pore-filling mechanism was proposed by comparing textural properties of MCM before and after adsorbing naproxen. C-H···π and n-π interactions were identified via FTIR technique. π-π interaction was observed by FTIR and Raman techniques. Oxidation of MCM with HNO3 or H2 O2 was a helpful method to explore π-π interaction. Electrostatic attraction was explained through studies: effects of pH and NaCl along with desorption.

Ameliorative effect of different mesoporous bioactive glass materials in experimental tibial defects in rats.

Background: Enhancing the bone healing procedure would resultantly improve the post-recovery life quality, as well as the speed with which the patient returns to their former life quality. Porous structures can provide a large surface area and abundant channels to facilitate mass transfer. Objective: To evaluate the application of mesoporous materials in the bone healing of surgically created defects on the tibiae of male adult Wistar rats. Methods: The defect areas were evaluated after implantation of 4 types of bioactive glass histopathologically and immunohistochemically. Fifty adult rats were divided into 5 groups including a control group without material. The used products were mesoporous bioactive glass (MBG), Cu-MBG, Zn-MBG, and Cu-Zn-MBG. Unicortical bone defects with a 3 mm diameter were performed in both tibiae of the animals and filled with 4 types of glass particles. The rats were then euthanized at 15 d and 30 d. Tibial samples were collected and the tissues forwarded for histological processing, and examined using light microscopy. Additionally, bone healing was evaluated by assessing the levels of bone morphogenetic protein BMP2, collagen 1, osteocalcin (OST), and vascular endothelial growth factor (VEGF) using immunohistochemical methods. Results: Within the 15th day, all groups presented connective tissue septa; at the 30th day, the new bone formation was more intense in the Cu-Zn-MBG group. Additionally, BMP2, collagen 1, OST, and VEGF immune expression were more prominent in the Cu-Zn-MBG group. Conclusions: The study results indicated that MBG may be used for the repairing of bone defects. Cu-Zn-MBG may be the best choice for this purpose.

Peanut shells-derived biochars prepared from different carbonization processes: Comparison of characterization and mechanism of naproxen adsorption in water.

The ubiquitous appearance of nonsteroidal anti-inflammatory drugs (i.e., naproxen) in water bodies has raised enormous concerns among general public. Development of promising materials for eliminating such contaminants from water environment has attracted much attention in the scientific community. In this study, three (direct, post-treated and pre-treated) methods were developed to prepare biochars (800-PSB, 800-800-PSB, and 190-800-PSB, respectively) derived from the wastes of peanut shells (PS). They were thoroughly characterized by various important properties (i.e., porosity and superficial functional group) and applied to remove naproxen drug from water. Results indicated that although the pre- and post-treatments had a slight effect on the surface area of biochars (i.e., 571 m2/g for 800-PSB, 596 m2/g for 800-800-PSB, and 496 m2/g for 190-800-PSB), such treatments remarkably improved the adsorption capacity of biochar. The maximum adsorption capacity of biochar (obtained from the Langmuir model) towards naproxen in solution at 25 decreased in the following order: 800-800-PSB (324 mg/g) > 190-800-PSB (215 mg/g) > 800-PSB (105 mg/g). The thermodynamic study demonstrated that the adsorption was spontaneous and exothermic. Depending the preparation process, the contribution of each mechanism in the adsorption process was dissimilar. The overall adsorption mechanism was regarded as pore filling, π-π interaction, hydrogen bonding formations, n-π interaction, van der Waals force, and electrostatic attraction. Two methods used to identify the important role of π-π interaction were proposed herein. The possible desorption and reuse of laden-biochars were investigated by the chemical and thermal methods. The prepared biochar samples can serve as potential carbonaceous porous adsorbents for effectively removing naproxen from water media.

Innovative spherical biochar for pharmaceutical removal from water: Insight into adsorption mechanism.

In this study, we developed an innovative spherical biochar with high porosity and excellent paracetamol (PRC) adsorption capacity. The optimal pyrolysis temperatures for the preparation of spherical biochar (derived from pure glucose) and non-spherical biochar (from pomelo peel wastes) were obtained at 900 °C and 700 °C, respectively. Various advanced techniques were applied to characterize the prepared biochars. Spherical and non-spherical biochars exhibited large specific surface area (1292 and 1033 m2/g) and high total pore volume (0.704 and 1.074 cm3/g), respectively. The adsorption behavior of PRC onto two biochars was conducted utilizing batch experiments. Results demonstrated that the adsorption process was slightly affected by the change of solution pH (2-11) and addition of NaCl (0.05-1.0 M) and was able to achieve fast equilibrium (∼120 min). The maximum adsorption capacity of spherical biochar (286 mg/g) for PRC was approximately double that of non-spherical biochar (147 mg/g). The signal of thermodynamic parameters was negative ΔG° and ΔH° values, but positive ΔS° value. The adsorption mechanism consisted of pore-filling, hydrogen bonding formations, n-π and π-π interactions, and van der Waals force. The adsorption capacities of two biochars were insignificantly dependent on different real water samples containing PRC. Consequently, the biochars can serve as a green and promising material for efficiently removing PRC from water.

Adsorption mechanism of hexavalent chromium onto layered double hydroxides-based adsorbents: A systematic in-depth review.

An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl-, NO3-, SO42-, and CO32-) provide a high anion exchange capacity (53-520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer-Emmett-Teller specific surface area of LDH (1.80-179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° <0) and endothermically (ΔH° >0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.