Novel Au NPs/Preyssler acid/TiO2 nanocomposite for the photocatalytic removal of azo dye

Rapid and efficient removal of water-soluble dyes via natural asphalt oxide as a new carbonaceous super adsorbent; NA-oxide synthesis and characterization

In this study, natural asphalt was oxidized to synthesize a new nano-structure adsorbent for dye removal. The functionalization of natural asphalt by oxidation introduced new properties that influenced its activity. The process of oxidizing natural asphalt with potassium permanganate resulted in a low-cost adsorbent, which can potentially be a more affordable option compared with synthetic alternatives. Characterization analysis confirmed the enhanced surface area, improving dye interaction and adsorption. The interconnected channels and capillaries of the oxidized natural asphalt facilitated the capillary action drawing in liquids, including dyes. The distinctive porosity of natural asphalt oxide (NA-oxide) was noted, and the experimental results showed that the NA-oxide nanoadsorbent efficiently adsorbed cationic and anionic dyes in water, with maximum capacities of 14.68 mg.g-1, 17.81 mg.g-1 and 16.47 mg.g-1 for methyl orange, methylene blue and Rhodamine B, respectively. The study investigated various parameters, such as concentration, adsorption dose, pH, contact time, and temperature, affecting the dye removal process. Langmuir, Freundlich, and Temkin isotherms along with pseudo-first and pseudo-second-order kinetic equations were applied to assess the adsorption process, indicating that dyes adhered to the pseudo-first-order model and Langmuir isotherm. Analysis of MO, MB, and RhB dyes revealed conformity to Langmuir isotherm and first-order kinetics. Thermodynamic evaluations like ΔH°, ΔS°, and ∆G° displayed the exothermic and spontaneous nature of dye adsorption on the NA-oxide adsorbent. Furthermore, the absorbent displayed remarkable stability with a recovery rate of 98.45% after ten cycles, signifying its potential for enduring effectiveness in dye removal processes.

Catalytic engineering of transition metal (TM: Ni, Pd, Pt)-coordinated Ge-doped graphitic carbon nitride (Ge@g-c3n4) nanostructures for petroleum hydrocarbon separation: An outlook from theoretical calculations

The extraction, processing, and utilization of petroleum often results in the release of diverse hydrocarbon pollutants into the environment, leading to severe ecological and health implications. Herein, the adsorption and separation of ethane (EAN), ethene (EEN), ethyne (EYN), and benzene (BZN) fractions of paraffin, olefin, acetylene, and aromatic petroleum hydrocarbons were investigated via the catalytically engineered nickel group transition metals; nickel (Ni), palladium (Pd), and platinum (Pt). These transition metals were coordinated on Germanium-doped graphitic carbon nitride (Ge@g-C3N4) nanostructures, and the behavior of the systems was studied through Kohn-Sham density functional theory (KS-DFT) with the B3LYP-D3(BJ)/Def2-SVP computational method. The adsorption of petroleum hydrocarbons decreased in the order Ge_Ni@C3N4 > Ge_Pd@C3N4 > Ge_Pt@C3N4>Ge_Pt@C3N4. These results showed that the coordination of Ni, Pd, and Pt within Ge@C3N4 improved the separation of petroleum hydrocarbons.

Unveiling the remarkable simultaneous adsorption-photocatalytic potential of Ag nanoparticles-anchored phosphotungestic acid loaded ZIF-8 for Congo red removal

This research paper presents a direct approach to synthesize AgNPs deposited on polyoxometalate/ZIF-8 on-site (referred to as AgNPS@PW@ZIF-8) to develop a highly efficient photocatalyst in the water treatment. Phosphotungestic acid (PW) serves a multi-purpose in this context: it acts as a bridge layer between AgNPs and Zeolitic Imidazolate Framework-8 (ZIF-8), a local reducing agent, and a catalyst for electron transfer during the photocatalysis process. A comprehensive characterization of the resulting nanostructure was performed utilizing an array of techniques, such as XRD, FTIR, EDX, TEM, BET, Raman, and TGA. The nanostructure that was created exhibited effective removal of Congo red at different pH levels via a combination of simultaneous adsorption and photocatalysis. After 60 min at pH 7, the dye molecules were completely eliminated in the presence of 0.5 g/L AgNPS@PW@ZIF-8 at room temperature. The charge transfer can be facilitated by the PW bridge layer connecting AgNPs and ZIF-8, owing to the photoactive characteristics and strong electron transfer capabilities of PW molecules. Strong electron transferability of PW between Ag nanoparticles and ZIF-8 facilitates charge transfer and significantly improves the photocatalytic performance of ZIF-8. Moreover, the nanostructure demonstrated great structural stability and recyclability, sustaining a high efficiency of removal throughout five consecutive cycles through the implementation of a simple procedure. Widespread applications of the developed nanostructure in aquatic environments for adsorption and photocatalytic reactions are possible.

The effect of the number of SO3- groups on the adsorption of anionic dyes by the synthesized hydroxyapatite/Mg-Al LDH nanocomposite

In this study, a new nanocomposite of hydroxyapatite (HA)/Mg-Al layered double hydroxide (LDH) was successfully formed via a facile co-precipitation method and applied to adsorb three anionic dyes of alizarin red S (ARS), Congo red (CR), and reactive red 120 (RR120) differing in the number of SO3- groups from aqueous solution. Based on a combination of characterization analysis and adsorption experiments, HA/Mg-Al LDH nanocomposite showed better adsorption performance than HA and Mg-Al LDH. Using XRD and TEM analyses, the crystallinity and the presence of nanoparticles were confirmed. According to the SEM investigation, the Mg-Al LDH layers in the nanocomposite structure were delaminated, while HA nanorods were formed at the surface of Mg-Al LDH nanoparticles. The higher BET surface area of the novel HA/Mg-Al LDH nanocomposite compared to HA and Mg-Al LDH provided its superior adsorption performance. Considering an effective amount of adsorbent dosage, pH 5 was selected as the optimum pH for each of the three dye solutions. According to the results from the study of contact time and initial concentration, the pseudo-second-order kinetic (R2 = 0.9987, 0.9951, and 0.9922) and Langmuir isotherm (R2 = 0.9873, 0.9956, and 0.9727) best fitted the data for ARS, CR, and RR120, respectively. Anionic dyes with different numbers of SO3- groups demonstrated distinct adsorption mechanisms for HA and Mg-Al LDH nanoparticles, indicating that the adsorption capacity is influenced by the number of SO3- groups, with HA/Mg-Al LDH nanocomposite offering superior performance toward dyes with higher numbers of SO3- groups. Furthermore, ΔH° less than 40 kJ/mol, positive ΔS°, and negative ΔG° accompanied by the mechanism clarifying show physical spontaneous adsorption without an external source of energy and increase the randomness of the process during the adsorption, respectively. Finally, the regeneration study demonstrated that the nanocomposite could be utilized for multiple adsorption-desorption cycles, proposing the HA/Mg-Al LDH as an economically and environmentally friendly adsorbent in the adsorption of anionic dyes in water treatment processes.

Design and synthesis of high performance magnetically separable exfoliated g-C3N4/γ-Fe2O3/ZnO yolk-shell nanoparticles: a novel and eco-friendly photocatalyst toward removal of organic pollutants from water

Herein, a new visible-light active exfoliated g-C3N4/γ-Fe2O3/ZnO yolk-shell nanoparticles (NPs) was synthesized as a magnetically separable photocatalyst. For an in-depth understanding of the magnetic photocatalyst's structural, morphological, and optical properties, the products were extensively characterized with FT-IR, XRD, TEM, HRTEM, FESEM, EDS, EDS-mapping, VSM, DRS, EIS, and photocurrent. The photocatalyst was then utilized to degrade Levofloxacin (LEVO) and Indigo Carmine (IC) by visible light at room temperature. The exfoliated g-C3N4/γ-Fe2O3/ZnO yolk-shell NPs photocatalyst revealed 80% and 95.6% degradation efficiency for Levofloxacin and Indigo Carmine within 25 and 15 min, respectively. In addition, the optimal factors such as concentration, loading of photocatalyst, and pH were also assessed. Levofloxacin degradation mechanistic studies showed that electrons and holes significantly contribute to the photocatalytic process of photocatalyst degradation. In addition, after 5 times regeneration, exfoliated g-C3N4/γ-Fe2O3/ZnO yolk-shell NPs remained as an excellent magnetic photocatalyst for the eco-friendly degradation of Levofloxacin and Indigo Carmine (76% and 90%), respectively. The superior photocatalytic performance of exfoliated g-C3N4/γ-Fe2O3/ZnO yolk-shell nanoparticles (NPs) was mostly ascribed to the synergistic advantages of stronger visible light response, larger specific surface area, and the more effective separation and transfer of photogenerated charge carriers. Based on these results, the highly effective magnetic photocatalyst achieved better results than numerous studied catalysts in the literature. The degradation of Levofloxacin and Indigo Carmine under environmentally friendly conditions can be achieved using exfoliated g-C3N4/γ-Fe2O3/ZnO yolk-shell NPs (V) as an efficient and green photocatalyst. The magnetic photocatalyst was characterized by spectroscopic and microscopic methods, revealing a spherical shape and particle size of 23 nm. Additionally, the magnetic photocatalyst could be separated from the reaction mixture by a magnet without significantly reducing its catalytic activity.

Insights into organic-inorganic hybrid molecular materials: organoimido functionalized polyoxomolybdates

Polyoxometalates (POMs) are polyatomic anions that comprise transition metal group 5 (V, Nb, Ta) or group 6 (Mo, W) oxyanions connected together by shared oxygen atoms. POMs are fascinating because of their exclusive and remarkable characteristics. One of the most interesting features of POMs is their capability to function as an electron relay by performing stepwise multi-electron redox reactions while maintaining their structural integrity. Functionalization of POMs with amino organic compounds results in organoimido derivatives of polyoxometalates, which have aroused interest due to augmentation of their properties. Comprehensive study has shown that the synthesis methodologies to obtain desired organoimido derivatives of POMs by employing various imido-releasing reagents have progressed drastically in recent decades, particularly the innovative DCC-dehydrating technique. These organoimido functionalized POMs have been used as major building blocks to develop unique nanostructured organic-inorganic hybrid molecular materials. Many conventional organic synthesis processes such as Pd-catalyzed carbon-carbon coupling and esterification reactions have been performed with organoimido functionalized POMs where the presence of POM triggered the reaction process. Thus, investigation of the reactivity of organoimido derivatives of POMs foreshadows the intriguing future of POMs chemistry.

Heterogeneous UV-Switchable Au nanoparticles decorated tungstophosphoric acid/TiO2 for efficient photocatalytic degradation process

In the present study, gold nanoparticles were locally well-decorated on the surface of TiO₂ using the tungstophosphoric acid (HPW), as UV-switchable reducing intermediate linkers. The prepared Au NPs/HPW/TiO₂ nanostructure was characterized using FTIR, XRD, EDS, SEM and TEM, which confirmed the successful attachment of quasi-spherical Au NPs in the range of 20-30 nm on the surface of HPW modified TiO₂. Also, the FTIR results show that the Au NPs were binded to TiO₂ through the terminal the oxygen atoms HPW. The photocatalytic performance of prepared nanostructures was assessed in degradation of nitrobenzene. The nitrobenzene photodegradation kinetic study revealed that it well followed the Langmuir-Hinshelwood kinetic model with the apparent rate constant of 0.001 min^-1 using anatase TiO₂, 0.0004 min^-1 using HPW, 0.0014 using HPW/TiO₂, while it was obtained 0.0065 min^-1 using Au NPs@HPW/TiO₂ nanostructure. It shows that the photocatalytic rate of the prepared nanocomposites increased by 6.5- and 4.6-fold compared to photoactivity of anatase TiO₂ and HPW/TiO₂ respectively. Also, the photocatalytic mechanism of process was proposed. Moreover, the reusability study confirmed that its photocatalytic activity still remained high after three cycles.

Polymer Nanocomposites for Photocatalytic Degradation and Photoinduced Utilizations of Azo-Dyes

Specially designed polymer nanocomposites can photo-catalytically degrade azo dyes in wastewater and textile effluents, among which TiO2-based nanocomposites are outstanding and extensively explored. Other nanocomposites based on natural polymers (i.e., chitosan and kaolin) and the oxides of Al, Au, B, Bi, Fe, Li, and Zr are commonly used. These nanocomposites have better photocatalytic efficiency than pure TiO2 through two considerations: (i) reducing the hole/electron recombination rate by stabilizing the excited electron in the conducting band, which can be achieved in TiO2-nanocomposites with graphene, graphene oxide, hexagonal boron nitride (h-BN), metal nanoparticles, or doping; (ii) decreasing the band energy of semiconductors by forming nanocomposites between TiO2 and other oxides or conducting polymers. Increasing the absorbance efficiency by forming special nanocomposites also increases photocatalytic performance. The photo-induced isomerization is exploited in biological systems, such as artificial muscles, and in technical fields such as memory storage and liquid crystal display. Heteroaryl azo dyes show remarkable shifts in photo-induced isomerization, which can be applied in biological and technical fields in place of azo dyes. The self-assembly methods can be employed to synthesize azo-dye polymer nanocomposites via three types of interactions: electrostatic interactions, London forces or dipole/dipole interactions between azo dyes, and photo alignments.

Base-Resistant Ionic Metal-Organic Framework as a Porous Ion-Exchange Sorbent

A systematic approach has been employed to obtain a hydrolytically stable cationic metal-organic framework (MOF). The synthesized two-dimensional Ni(II)-centered cationic MOF, having its backbone built from purely neutral N-donor ligand, is found to exhibit uncommon resistance over wide pH range, particularly even under highly alkaline conditions. This report presents a rare case of a porous MOF retaining structural integrity under basic conditions, and an even rarer case of a porous cationic MOF. The features of stability and porosity in this ionic MOF have been harnessed for the function of charge- and size-selective capture of small organic dye through ion-exchange process across a wide pH range.

Emerging adsorptive removal of azo dye by metal-organic frameworks

Adsorptive removal of toxic compounds using advanced porous materials is one of the most attractive approaches. In recent years, the metal-organic frameworks (MOFs), a subset of advanced porous nano-structured materials, due to their unique characteristics are showing great promise for better adsorption/separation of various water contaminants. Given the importance of azo dye removal, as an important class of pollutants, this paper aims to review and summarize the recently published research on the effectiveness of various MOFs adsorbents under different physico-chemical process parameters in dyes adsorption. The effect of pH, the adsorption mechanism and the applicability of various adsorption kinetic and thermodynamic models are briefly discussed. Most of the results observed showed that the adsorption kinetic and isotherm of azo dyes onto the MOFs mostly followed the pseudo-second order and Langmuir models respectively. Also, the optimum pH value for the removal of majority of azo dyes by MOFs was observed to be in the range of ∼5-7.