Removal of Cr(VI) from Aqueous Solutions Using Amino-Functionalized Carbon Nanospheres Adsorbents.

Carbon nanospheres were prepared and functionalized with carboxyl acid groups (CNS-CA), then reacted with 3-aminopropyltriethoxysilane to introduce amino groups onto the surface (CNS-NH2) by post-synthesis grafting. CNS-NH2 was acidified in order to convert the amino groups (-NH2) into ammonium moieties (). Various techniques such as N2 physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetry, X-ray photoelectron spectroscopy, and transmission electron microscopy were used to characterize the nanospheres. The removal of chromium ions from aqueous solution using was investigated. Factors influencing the uptake of Cr(VI) ions such as solution pH, adsorbent dose, and initial Cr(VI) ion concentration were investigated. Equilibrium adsorption data fitted the Langmuir model very well. The adsorption maximum capacity of Cr(VI) was found to be 52.38 mg/g. The reusability of results indicated that it can be reused five times successfully without loss of adsorption capacity.

Investigation of ammonium ion removal from aqueous solutions using arene- and propylsulfonic Acid functionalized mesoporous silica adsorbents.

To counter environmental threats to the water resources polluted by NH, which is common in wastewaters and agricultural runoff, adsorption using mesoporous functional materials represents a promising alternative to existing treatment methods. In this study, adsorption of NH ions from aqueous solutions was investigated on arene- and propylsulfonic acid functionalized SBA-15 mesoporous silica materials. The adsorbents were synthesized via co-condensation and post-synthesis grafting procedures. Adsorbents were characterized by means of X-ray diffraction, N physisorption, titration, and elemental analyses. The effects of pH, NH initial concentration, temperature, adsorbent loading, organosilane molar ratio, and presence of competitive species on the performance of the adsorbent materials were examined. All the adsorbents having an organosilane/silica molar ratio of 1:5 displayed maximum adsorption capacity around approximately 25 mg g NH at the lowest temperature investigated, 5°C. This capacity decreased with increasing temperature. For a given initial NH concentration, the removal efficiency () increased with increasing adsorbent loading. For instance, increased from 24 to 59% when the adsorbent loading was increased from 2 to 10 g L at 25°C. The adsorption isotherms were well described by a Langmuir model equation. Adsorption capacity improved with increasing organosilane/silica molar ratio, reaching 42 mg g NH with a ratio of 2:5 at 25°C. Arene- and propylsulfonic acid functionalized SBA-15 materials synthesized via co-condensation and post-synthesis grafting proved to be effective high-capacity adsorbents for the removal of NH ions from aqueous solutions.

Aqueous Acetamiprid Degradation Using Combined Ultrasonication and Photocatalysis Under Visible Light.

Acetamiprid (ACE), a neonicotinoid pesticide widely used in pest control, was found in high concentrations in soils, rivers, and lakes. In the present study, ACE degradation was investigated using visible light driven photocatalysis over nitrogen-graphene oxide (N-GO) and palladium-graphene oxide (Pd-GO)-doped ZnO photocatalysts combined with ultrasonication implemented either as a pretreatment (sonolysis) or operated simultaneously with photocatalysis (sonophocatalysis). The effectiveness of the two ACE degradation processes was determined separately. The sonolysis pretreatment allowed reaching almost 40% acetamiprid conversion within 30 min of reaction. Pursuing with the photodegradation reaction in the presence of N-GO-ZnO and Pd-GO-ZnO resulted in a maximum conversion of 98% of ACE within 5 h. As for the sonophotocatalysis process, the reaction time was shortened from 5 to 2 h with 100% acetamiprid conversion. In addition, the photocatalysts were shown to keep their activity even after 5 sonophotocatalytic cycles, thus proving their reusability. Supplementary Information: The online version contains supplementary material available at 10.1007/s11270-022-05867-4.

Physical and Enzymatic Hydrolysis Modifications of Potato Starch Granules.

In this work, a valorization of the starch stemming from downgraded potatoes was approached through the preparation of starch nanoparticles using different physical methods, namely liquid and supercritical carbon dioxide, high energy ball milling (HEBM), and ultrasonication on the one hand and enzymatic hydrolysis on the other hand. Starch nanoparticles are beneficial as a reinforcement in food packaging technology as they enhance the mechanical and water vapor resistance of polymers. Also, starch nanoparticles are appropriate for medical applications as carriers for the delivery of bioactive or therapeutic agents. The obtained materials were characterized using X-ray diffraction as well as scanning and transmission electron microscopies (SEM and TEM), whereas the hydrolysates were analyzed using size exclusion chromatography coupled with pulsed amperometric detection (SEC-PAD). The acquired results revealed that the physical modification methods led to moderate alterations of the potato starch granules' size and crystallinity. However, enzymatic hydrolysis conducted using Pullulanase enzyme followed by nanoprecipitation of the hydrolysates allowed us to obtain very tiny starch nanoparticles sized between 20 and 50 nm, much smaller than the native starch granules, which have an average size of 10 µm. The effects of enzyme concentration, temperature, and reaction medium pH on the extent of hydrolysis in terms of the polymer carbohydrates' fractions were investigated. The most promising results were obtained with a Pullulanase enzyme concentration of 160 npun/g of starch, at a temperature of 60 °C in a pH 4 phosphate buffer solution resulting in the production of hydrolysates containing starch polymers with low molecular weights corresponding mainly to P-10, P-5, and fractions with molecular weights lower than P-5 Pullulan standards.

Visible light driven photocatalytic degradation of aqueous acetamiprid over nitrogen and graphene oxide doped ZnO composites.

The present investigation focused on the photocatalytic degradation of acetamiprid in aqueous solutions under visible light over bare ZnO as well as N- and N-GO-doped photocatalysts. The synthesised materials were characterised using SEM, TEM, XRD, nitrogen sorption, photoluminescence, UV-Vis, FTIR and electrochemical impedance spectroscopy techniques. The obtained results pointed out the high photocatalytic performances of the N-GO-ZnO allowing complete degradation of the acetamiprid after 5 hours of reaction at ambient temperature. Under otherwise the same operating conditions, 12, 38 and 68% conversion were reached in the absence of any photocatalyst, over the bare ZnO and N-doped ZnO materials, respectively.

Development of α- and γ-Fe2O3 decorated graphene oxides for glyphosate removal from water.

In this study, the proposed adsorbent composed of graphene oxide (GO) functionalized by magnetic nanoparticles of iron oxide (α-γ-Fe2O3) was obtained by a simple ultrasonication process. This new material was used for the removal of glyphosate in water. The nanoparticulated iron oxide used was synthesized by means of a modified sol-gel method, which does not use organic solvents. The adsorbent material (GO-α-γ-Fe2O3) obtained was characterized by magnetic measurements, and it can be proved that it has superparamagnetic properties, allowing fast and efficient magnetic separation. The equilibrium time for the adsorption of glyphosate when using GO-α-γ-Fe2O3 was 2 hours and the maximum removal was 92% at 15°C, with a maximum adsorption capacity of 46.8 mg g-1. Langmuir model and pseudo-second-order kinetic model correlated satisfactorily to the experimental data. The thermodynamic parameters showed that the adsorption of glyphosate on GO-α-γ-Fe2O3 was spontaneous, exothermic and thermodynamically favorable at temperature of 15-45°C. Thus the adsorbent material GO-α-γ-Fe2O3 proposed in this study is considered a good candidate to be used in the removal of glyphosate from aqueous solutions, presenting high adsorption capacity, low cost and magnetic properties that facilitate the separation of the adsorbent material.

Adsorption of phosphate and nitrate anions on ammonium-functionalized MCM-48: effects of experimental conditions.

In this study, ammonium-functionalized MCM-48 (Mobil Composite Material No. 48) was used as an adsorbent to remove nitrate (NO(-)(3)) and monobasic phosphate (H(2)PO(-)(4)) anions from aqueous solutions. The effects of operating conditions such as temperature, adsorbent loading, initial anion concentration, pH, and the presence of competitive ions on the adsorption performances were examined. Results showed that adsorption capacity decreased with increasing temperature. The adsorption capacity increased with adsorbent loading and initial anion concentration. The removal of nitrate was maximum at pH<8, while phosphate removal was maximized at pH 5. The adsorption was almost unaffected by the presence of competitive ions in the case of phosphate anions. However, their presence adversely affected nitrate adsorption. Desorption of both anions was rapidly achieved within 10 min using NaOH at 0.01 M. Regeneration tests showed that the adsorbent retained its capacity after 5 adsorption-desorption cycles.

Synthesis, characterization and insights into stable and well organized hexagonal mesoporous zinc-doped alumina as promising metathesis catalysts carrier.

A series of highly ordered hexagonal mesoporous alumina and zinc-modified mesoporous alumina samples are synthesized via a sol-gel method through an evaporation-induced self-assembly process using Pluronic F127 as nonionic templating agent and several aluminum precursors. The process was mediated using several carboxylic acids along with hydrochloric acid in ethanol. Successful impregnation of ZnCl2 was achieved while maintaining the ordered structure. The surface and textural properties of the materials were investigated. N2-physisorption analysis revealed a BET surface area of 394 m(2) g(-1) and a pore volume around 0.55 cm(3) g(-1). Moreover, small-angle XRD diffraction patterns highlighted the well-organized hexagonal structure even upon the incorporation of zinc chloride. The organized-structure arrangement was further confirmed by transmission electron microscopy (TEM) analysis. The Zn/Al composition of the final materials was confirmed by EDX and XPS analysis, and the zinc amount incorporated was analyzed by ICP. Furthermore, the surface modification with zinc chloride impregnation was analyzed by XPS, (1)H and (27)Al MAS-NMR and FTIR spectroscopic techniques. In addition, the effects of synthesis conditions and the mechanism of the mesostructure formation were explored. The catalytic activity of several methyltrioxorhenium (MTO)-based catalysts supported on these hexagonal mesoporous alumina materials was tested for methyl oleate self-metathesis. The results showed improved kinetics using hexagonal alumina in comparison to those using wormhole-like alumina counterparts. This behavior could be attributed to better mass transfer features of hexagonal mesoporous alumina. The prepared materials with desirable pore size and structure are suitable candidates as catalyst supports for metathesis of bulky functionalized olefins and other catalytic transformations due to their enhanced Lewis acidity and more uniform pore networks favoring enhanced and selective mass transfer phenomena.

Periodic mesoporous organosilica from micellar oligomer template solution.

Periodic mesoporous organosilica (PMO) with two-dimensional hexagonal symmetry was synthesised using a bridged silsesquioxane (CH3O)3Si-CH2-CH2-Si(CH3O)3 as precursor and polyoxyethylene non-ionic surfactant (Brij-56) as template. The hybrid material was characterised by X-ray diffraction, N2 adsorption, TEM, and solid-state 29Si MAS NMR spectroscopy.

Adsorptive removal of dihydrogenphosphate ion from aqueous solutions using mono, di- and tri-ammonium-functionalized SBA-15.

Adsorption of monovalent phosphate anions from aqueous solutions on mono, di- and tri-ammonium-functionalized mesoporous SBA-15 silica was investigated. The adsorbent was prepared via a post-synthesis grafting method, using 3-aminopropyltrimethoxysilane (N-silane), [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane (NN-silane) and 1-[3-(trimethoxysilyl)-propyl]-diethylenetriamine (NNN-silane), followed by acidification in HCl solution to convert the attached surface amino groups to positively charged ammonium moieties. The loading of amino moieties on the SBA-15 surface was varied from 5% to 40% as organoalkoxysilane/silica molar ratio. The adsorption experiments were conducted batchwise at room temperature. Results showed that adsorption capacity increased with increasing the concentration of functional groups on the SBA-15 adsorbent whatever the nature of the functional group. In the case of monoammonium functional groups, the adsorption capacity increased from 0.64 to 1.07 mmol H(2)PO(4)(-)/g when the molar ratio organoalkoxysilane/silica was varied from 5% to 40%, respectively. Similar tendency was observed in the case of diammonium and triammonium organic functional groups. Also, for the same organoalkoxysilane/silica molar ratio, the adsorption capacity increased markedly with the increase of the number of protonated amines in the functional groups. Therefore, maximum adsorption capacities of 1.07, 1.70 and 2.46 mmol H(2)PO(4)(-)/g adsorbent were obtained using mono-, di- and tri-ammonium-functionalized SBA-15, respectively.