Green synthesis of the Fe3O4@polythiophen-Ag magnetic nanocatalyst using grapefruit peel extract: Application of the catalyst for reduction of organic dyes in water

Efficient removal of methyl orange and ciprofloxacin by reusable Eu-TiO2/PVDF membranes with adsorption and photocatalysis methods

The presence of methyl orange (MO) and ciprofloxacin (CIP) in wastewater poses a serious threat to the environment and human health. Titanium dioxide nanoparticles (TiO2 NPs) are widely studied as photocatalysts for wastewater treatment. However, TiO2 NPs have the drawbacks of high energy required for activation, fast electron-hole pair recombination and difficulty in recovering from water. To overcome these problems, europium decorated titanium dioxide/poly(vinylidene fluoride) (Eu-TiO2/PVDF) membranes were successful prepared in this work by combining the modified sol-gel method and the immersion phase inversion method. The Eu-TiO2/PVDF membranes obtained with the increase of Eu-TiO2 NPs content during the preparation process were named M1, M2 and M3, respectively. The pure PVDF membrane without the addition of Eu-TiO2 NPs was named M0, which was prepared by the immersion phase inversion method and served as a reference. The prepared Eu-TiO2/PVDF membranes could not only adsorb MO, but also degrade CIP under visible-light irradiation. Moreover, the Eu-TiO2/PVDF membranes exhibited adsorption-photocatalytic activity towards a mixture of MO and CIP under visible-light irradiation. Last but not the least, the Eu-TiO2/PVDF membranes exhibited excellent recyclability and reusability, opening the avenue for a possible use of these membranes in sewage-treatment plants.

Application of Electrochemical Oxidation for Water and Wastewater Treatment: An Overview

In recent years, the discharge of various emerging pollutants, chemicals, and dyes in water and wastewater has represented one of the prominent human problems. Since water pollution is directly related to human health, highly resistant and emerging compounds in aquatic environments will pose many potential risks to the health of all living beings. Therefore, water pollution is a very acute problem that has constantly increased in recent years with the expansion of various industries. Consequently, choosing efficient and innovative wastewater treatment methods to remove contaminants is crucial. Among advanced oxidation processes, electrochemical oxidation (EO) is the most common and effective method for removing persistent pollutants from municipal and industrial wastewater. However, despite the great progress in using EO to treat real wastewater, there are still many gaps. This is due to the lack of comprehensive information on the operating parameters which affect the process and its operating costs. In this paper, among various scientific articles, the impact of operational parameters on the EO performances, a comparison between different electrochemical reactor configurations, and a report on general mechanisms of electrochemical oxidation of organic pollutants have been reported. Moreover, an evaluation of cost analysis and energy consumption requirements have also been discussed. Finally, the combination process between EO and photocatalysis (PC), called photoelectrocatalysis (PEC), has been discussed and reviewed briefly. This article shows that there is a direct relationship between important operating parameters with the amount of costs and the final removal efficiency of emerging pollutants. Optimal operating conditions can be achieved by paying special attention to reactor design, which can lead to higher efficiency and more efficient treatment. The rapid development of EO for removing emerging pollutants from impacted water and its combination with other green methods can result in more efficient approaches to face the pressing water pollution challenge. PEC proved to be a promising pollutants degradation technology, in which renewable energy sources can be adopted as a primer to perform an environmentally friendly water treatment.

Recyclable Mussel-Inspired Magnetic Nanocellulose@Polydopamine-Ag Nanocatalyst for Efficient Degradation of Refractory Organic Pollutants and Bacterial Disinfection

Development of a novel strategy to tackle bacterial-contaminated complex industrial wastewaters containing refractory organic pollutants is of great demand. In this study, polydopamine (PDA)-coated magnetic cellulose nanofiber (MCNF)-loaded silver nanoparticle (AgNP) (MCNF/PDA-Ag) nanocomposites were designed and applied for efficient degradation of organic dye pollutants and inactivation of Escherichia coli (E. coli) in wastewater. In the presence of NaBH₄, MCNF/PDA-Ag could achieve a high catalytic reduction rate of 6.54 min^-1 for the removal of methylene blue. Similarly, it showed good catalytic reduction performance for methyl orange (0.63 min^-1) and 4-nitrophenol (2.94 min^-1). The MCNF/PDA-Ag nanocomposites can be easily magnetically recycled and reused with negligible loss of catalytic performance. Moreover, this nanocatalyst also exhibited excellent disinfection performance against E. coli, with more than 99% disinfection ratio at very low doses (50 μg/mL). Overall, this work provides new insights into a delicate design of advanced magnetically recyclable silver nanocomposites with ultrahigh catalytic rates and excellent antibacterial properties from sustainable nature biomass.

Valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment: Approaching green chemistry and circular economy principles

Water pollution is one of the most critical issues worldwide and is a priority in all scientific agendas. Green nanotechnology presents a plethora of promising avenues for wastewater treatment. This review discusses the current trends in the valorization of zero-cost, biodegradable, and readily available agro-industrial biowaste to produce green bio-nanocatalysts and bio-nanosorbents for wastewater treatment. The promising roles of green bio-nanocatalysts and bio-nanosorbents in removing organic and inorganic water contaminants are discussed. The potent antimicrobial activity of bio-derived nanodisinfectants against water-borne pathogenic microbes is reviewed. The bioactive molecules involved in the chelation and tailoring of green synthesized nanomaterials are highlighted along with the mechanisms involved. Furthermore, this review emphasizes how the valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment adheres to the fundamental principles of green chemistry, circular economy, nexus thinking, and zero-waste manufacturing. The potential economic, environmental, and health impacts of valorizing agro-industrial biowaste to green nanomaterials are highlighted. The challenges and future outlooks for the management of agro-industrial biowaste and safe application of green nanomaterials for wastewater treatment are summarized.

Composite of MOF and chitin as an efficient catalyst for photodegradation of organic dyes

A novel composite has been fabricated by using MOF and chitin as a natural and biocompatible compound. To this purpose, MOF was synthesized by using 2-aminoterephthalic acid and iron (III) chloride hexahydrate and then reacted with Cl-functionalized chitin. The resulting composite was characterized and utilized as a catalyst for degradation of methylene blue both in dark condition and under visible light irradiation. The results indicated superior catalytic activity under visible light irradiation. Furthermore, study of the reaction variables, including basicity, dye concentration and catalyst loading showed that the highest catalytic activity was achieved at basic condition. It was also found that both initial dye concentration and catalyst loading can affect the catalytic activity. To disclose the merits of the composite compared to its individual components, kinetic studies of the photo-degradation process in the presence of the composite, chitin and MOF have been performed. The results confirmed superior activity the composite compared to its components. The study of the mechanism of the reaction using scavengers confirmed that the created holes (h⁺) are the most effective species in the process of photocatalytic degradation of MB. Notably, the catalyst was recyclable and could be used for degradation of other dyes.

Gold nanoparticles decorated biguanidine modified mesoporous silica KIT-5 as recoverable heterogeneous catalyst for the reductive degradation of environmental contaminants

This current study involves the novel synthesis of Au nanoparticles (Au NPs) decorated biguanidine modified mesoporous silica KIT-5 following post-functionalization approach. The tiny Au NPs were being stabilized over the in situ prepared biguanidine ligand. The high surface area material was characterized using analytical techniques like Fourier Transformed infrared (FT-IR) spectroscopy, N2-adsorption-desorption isotherm, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction study (XRD). Our material was found to be an efficient catalyst in the reductive degradation of harmful water contaminating organic dyes like Methylene blue (MB), Methyl Orange (MO) and Rhodamin B (RhB) in presence of NaBH4 at room temperature. The whole procedure was followed up with the help of time dependant UV-Vis spectroscopy. All the reactions followed pseudo-unimolecular kinetics and corresponding rate constant were determined. The reduction rate becomes high in presence of higher load of catalysts.

Plant Extract Induced Biogenic Preparation of Silver Nanoparticles and Their Potential as Catalyst for Degradation of Toxic Dyes

This study focusses on the synthesis of silver nanoparticles (Ag-nPs) by citrus fruit (Citrus paradisi) peel extract as reductant while using AgNO3 salt as source of silver ions. Successful preparation of biogenic CAg-nPs catalyst was confirmed by turning the colorless reaction mixture to light brown. The appearance of surface Plasmon resonance (SPR) band in UV-Vis spectra further assured the successful fabrication of nPs. Different techniques such as FTIR, TGA and DLS were adopted to characterize the CAg-nPs. CAg-nPs particles were found to excellent catalysts for reduction of Congo red (CR), methylene blue (MB), malachite green (MG), Rhodamine B (RhB) and 4-nitrophenol (4-NP). Reduction of CR was also performed by varying the contents of NaBH4, CR and catalyst to optimize the catalyst activity. The pseudo first order kinetic model was used to explore the value of rate constants for reduction reactions. Results also interpret that the catalytic reduction of dyes followed the Langmuir–Hinshelwood (LH) mechanism. According to the LH mechanism, the CAg-nPs role in catalysis was explained by way of electrons transfer from donor (NaBH4) to acceptor (dyes). Due to reusability and green synthesis of the CAg-nPs catalyst, it can be a promising candidate for the treatment of water sources contaminated with toxic dyes.

Valorisation of Fruits, their Juices and Residues into Valuable (Nano)materials for Applications in Chemical Catalysis and Environment

One of the most abundant wastes from all around the world is nutrient resources. Among them, fruits, their extracts, and residues comprise a major portion, which contain many valuable components that get lost during disposal or become burden on the shrinking landfills. These concerns are addressed by seeking sustainable processing methods that would have a minimal environmental impact. The crops contain renewable chemicals which are useful for catalysis, wastewater treatment, or preparation of nanomaterials; there has been an upsurge for the industrial applications of (nano)materials as their environmental and catalytic appliances is a fascinating subject to design cheaper and safer catalytic systems. Due to the excellent chemical properties of the fruit extracts, they have garnered attention as cost-effective catalysts and support materials. This review focuses on the preparation of (nano)materials and their catalytic and environmental applications and highlights the potential appliances and industrial benefits derived from these low-cost renewable and sustainable greener sources thus essentially converting waste into wealth.

Bio-assisted synthesized Pd nanoparticles supported on ionic liquid decorated magnetic halloysite: an efficient catalyst for degradation of dyes

Using natural materials, i.e. halloysite nanoclay that is a biocompatible naturally occurring clay and Heracleum persicum extract that can serve as a green reducing agent, a novel magnetic catalyst, Fe₃O₄/Hal-Mel-TEA(IL)-Pd, has been designed and fabricated. To prepare the catalyst, halloysite was first magnetized (magnetic particles with mean diameter of 13.06 ± 3.1 nm) and then surface functionalized with melamine, 1,4 dibromobutane and triethanolamine to provide ionic liquid on the halloysite surface (5 wt%). The latter was then used as a support to immobilize Pd nanoparticles that were reduced by Heracleum persicum extract. The characterization of the catalyst established that the loading of Pd in Fe₃O₄/Hal-Mel-TEA(IL)-Pd was very low (0.93 wt%) and its specific surface area was 63 m²g⁻¹. Moreover, the catalyst showed magnetic property (Ms = 19.75 emu g⁻¹) and could be magnetically separated from the reaction. The catalytic performance of the magnetic catalyst for reductive degradation of methyl orange and rhodamine B in the presence of NaBH₄ in aqueous media was investigated. The activation energy, enthalpy, and entropy for the reduction of methyl orange were estimated as 42.02 kJ mol⁻¹, 39.40 kJ mol⁻¹, and −139.06 J mol⁻¹ K⁻¹, respectively. These values for rhodamine B were calculated as 39.97 kJ mol⁻¹, 34.33 kJ mol⁻¹, and −155.18 Jmol⁻¹K⁻¹, respectively. Notably, Fe₃O₄/Hal-Mel-TEA(IL)-Pd could be reused for eight reaction runs with negligible loss of the catalytic activity (~3%) and Pd leaching (0.01 wt% of the initial loading).

Biosynthesis of Au nanoparticles supported on Fe3O4@polyaniline as a heterogeneous and reusable magnetic nanocatalyst for reduction of the azo dyes at ambient temperature

In this research Au nanoparticles, supported on Fe₃O₄@polyaniline as a magnetic nanocatalyst, was synthesized and its performance has been evaluated to reduce Methylene Blue (MB) and Methyl Orange (MO) from aqueous solutions. Gold nanoparticles, as a nanocatalyst with excellent activity, were prepared through the reduction of Au³⁺ using a wild herbal extract (Allium Sp) without any toxic chemical compounds and harmful materials. The synthesized Fe₃O₄@PANI-Au magnetic nanocatalyst was characterized by different instruments. To investigate the effect of nanocatalyst concentration on the degradation rate of azo dyes, two different catalyst concentrations were used at ambient temperature. According to the carried out calculations, degradation reaction of azo dyes with NaBH₄ in presence of the nanocatalyst is 10³ to 10⁴ times faster than degradation without using the catalyst.

Preparation, characterization and catalytic application of nano-Fe3O4@SiO2@(CH2)3OCO2Na as a novel basic magnetic nanocatalyst for the synthesis of new pyranocoumarin derivatives

We present a study on the synthesis, characterization and application of sodium carbonate tag silica-coated nano-Fe₃O₄ (Fe₃O₄@SiO₂@(CH₂)₃OCO₂Na) as a novel and efficient heterogeneous basic catalyst.