Sucrose-Triggered, Self-Sustained Combustive Synthesis of Magnetic Nickel Oxide Nanoparticles and Efficient Removal of Malachite Green from Water

Exploring Ficus religiosa inflorescence powder as an eco-friendly and sustainable solution for the removal of crystal violet with a disposal solution

This study investigates the potential of using Ficus religiosa inflorescence (peepal tree) as an efficient solution for removing crystal violet from simulated and industrial wastewater. Various analyses were conducted to understand the adsorbent's structure, including particle morphology, BET surface area, FTIR, and pHZPC. The adsorption process was studied under different physicochemical factors such as temperature, concentration, contact time, and pH. Results revealed rapid adsorption, with 94.15% removal efficiency within the first 15 min at neutral pH. The highest observed adsorption capacity was 198.03 mg g-1, following pseudo-second-order kinetics (R2 = 0.99), indicating chemisorption. The Langmuir model accurately described the adsorption pathway (R2 = 0.99), showing monolayer adsorption. Thermodynamic analysis indicated an exothermic, feasible, and spontaneous process with increased entropy. The adsorbent could be easily regenerated using a 1:1 MeOH/H2O mixture for up to three cycles, yielding up to 73.86%. Real-time application with industrial effluent containing crystal violet showed up to 44.70% adsorption. The experiments demonstrated reliability with evaluated standard deviations (0.017935-0.000577) and relative standard deviations (0.439-0.673%), confirming statistical reliability. In conclusion, it presents a sustainable and eco-friendly approach for removing crystal violet dye from diverse wastewater sources.

The Effect of Composition on the Properties and Application of CuO-NiO Nanocomposites Synthesized Using a Saponin-Green/Microwave-Assisted Hydrothermal Method

In this study, we explored the formation of CuO nanoparticles, NiO nanoflakes, and CuO-NiO nanocomposites using saponin extract and a microwave-assisted hydrothermal method. Five green synthetic samples were prepared using aqueous saponin extract and a microwave-assisted hydrothermal procedure at 200 °C for 30 min. The samples were pristine copper oxide (100C), 75% copper oxide-25% nickel oxide (75C25N), 50% copper oxide-50% nickel oxide (50C50N), 25% copper oxide-75% nickel oxide (25C75N), and pristine nickel oxide (100N). The samples were characterized using FT-IR, XRD, XPS, SEM, and TEM. The XRD results showed that copper oxide and nickel oxide formed monoclinic and cubic phases, respectively. The morphology of the samples was useful and consisted of copper oxide nanoparticles and nickel oxide nanoflakes. XPS confirmed the +2 oxidation state of both the copper and nickel ions. Moreover, the optical bandgaps of copper oxide and nickel oxide were determined to be in the range of 1.29-1.6 eV and 3.36-3.63 eV, respectively, and the magnetic property studies showed that the synthesized samples exhibited ferromagnetic and superparamagnetic properties. In addition, the catalytic activity was tested against para-nitrophenol, demonstrating that the catalyst efficiency gradually improved in the presence of CuO. The highest rate constants were obtained for the 100C and 75C25N samples, with catalytic efficiencies of 98.7% and 78.2%, respectively, after 45 min.

Lanthanide-Doped ZnO Nanoparticles: Unraveling Their Role in Cytotoxicity, Antioxidant Capacity, and Nanotoxicology

This study used a sonochemical synthesis method to prepare (La, Sm)-doped ZnO nanoparticles (NPs). The effect of incorporating these lanthanide elements on the structural, optical, and morphological properties of ZnO-NPs was analyzed. The cytotoxicity and the reactive oxygen species (ROS) generation capacity of ZnO-NPs were evaluated against breast (MCF7) and colon (HT29) cancer cell lines. Their antioxidant activity was analyzed using a DPPH assay, and their toxicity towards Artemia salina nauplii was also evaluated. The results revealed that treatment with NPs resulted in the death of 10.559-42.546% and 18.230-38.643% of MCF7 and HT29 cells, respectively. This effect was attributed to the ability of NPs to downregulate ROS formation within the two cell lines in a dose-dependent manner. In the DPPH assay, treatment with (La, Sm)-doped ZnO-NPs inhibited the generation of free radicals at IC50 values ranging from 3.898 to 126.948 μg/mL. Against A. salina nauplii, the synthesized NPs did not cause death nor induce morphological changes at the tested concentrations. A series of machine learning (ML) models were used to predict the biological performance of (La, Sm)-doped ZnO-NPs. Among the designed ML models, the gradient boosting model resulted in the greatest mean absolute error (MAE) (MAE 9.027, R2 = 0.86). The data generated in this work provide innovative insights into the influence of La and Sm on the structural arrangement and chemical features of ZnO-NPs, together with their cytotoxicity, antioxidant activity, and in vivo toxicity.

Think before throw: waste chili stalk powder for facile scavenging of cationic dyes from water

Chili stalk powder (CS), a non-conventional adsorbent, has been exercised for facile removal of cationic dyes from simulated and wastewater by batch technique. The prepared material has been characterized by Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller analysis (BET), powder X-ray diffraction (powder XRD), and pHZPC and tested best with methylene blue and crystal violet under ambient conditions. FTIR denotes the presence of carbonyl and polyphenolic groups, responsible for dye adsorption. BET surface area analysis evaluates the porous nature and specific surface area of the material, and powder XRD confirms its amorphous nature. The porous structure could be ascertained from the FESEM image, and energy dispersive X-ray analysis (EDX) confirms the elemental composition. The pH above pHzpc shows an increase in removal efficiency. The maximum adsorption capacities are 49.53 and 36.88 mg/g for methylene blue (MB) and crystal violet (CV) respectively. Linear as well as non-linear plots for kinetic and isotherm models were studied. Both dye uptake fits the linear plot of Langmuir adsorption isotherm (R2 = 0.999 and 0.995) and pseudo-second-order kinetics (R2 = 0.998 and 0.999). In the non-linear plot, the adsorption process for both dyes fit Langmuir (R2 = 0.999 for MB and R2 = 0.983 for CV) as well as Freundlich adsorption (R2 = 0.999 for MB and R2 = 0.994 for CV). 75.48% crystal violet (CV) and 73.35% methylene blue (MB) regeneration were successful in 1:1 methanol medium and reused for up to three cycles. The uptake mechanism is suggested to be a union of π-π stacking, electrostatic interaction, and weak hydrogen bonding. The material was tested with industrial effluent to prove its application in real wastewater treatment. Moreover, the material shows superior adsorption capacity than contemporary phytosorbents. To conclude, a zero-cost adsorbent using green chili stalk has been demonstrated for wastewater treatment.

Pristine wild sugarcane (Saccharum spontaneum) as a biosorbent for removal of methylene blue from wastewater: isotherm, kinetics and regeneration studies

Saccharum spontaneum, popularly known as Kashful (KF) is a seasonal perennial grass with thin culms, mostly an abundantly growing shrub during the autumn season in southern Asia. It is used as no-cost scavenger to convincingly arrest methylene blue, a recalcitrant dye from colored effluent. FTIR, FESEM-EDX, and BET surface area characterize the material well whereas the surface activity was evaluated from zero-point charge (pHZPC = 6.720). FTIR highlights the presence of polyphenolic and carboxylate moieties. The surface texture is rod-like with intermittent non-homogeneous pores with occasional fractures. The equilibrium reaches within 60 min with the maximum adsorption capacity of 20.917 mg/g. The fibrous powder of kashful stalk (KFS) follows pseudo-second-order (R2 = 0.999 for linear and R2 = 0.985 for non-linear) kinetics and both Langmuir and Freundlich isotherm model (for linear, Langmuir R2=0.995; for non-linear, R2 = 0.994 for both Langmuir and Freundlich model). The uptake process was spontaneous (ΔG= -3.077 kJ/mol) and endothermic (ΔH = 17.815 kJ/mol). 1:1 methanol could regenerate the dye-loaded material in up to 55% and onward efficiency was conducive for three consecutive cycles. Industrial effluent analysis suggests a real-time removal of ∼55% in the first cycle. Saccharum spontaneum could be exercised to solve environmental problems related to colored water.

Adsorptive removal of Safranine T dye from aqueous solutions using sodium alginate-Festuca arundinacea seeds bio-composite microbeads

In this study, composite microbeads were prepared using Festuca arundinacea seeds and sodium alginate biopolymer at different ratios and utilized as sorbents for the sorption of Safranine T from wastewater. The sorbents were characterized by FTIR, SEM, XRD, and BET analysis. According to BET analysis, the specific surface area of the adsorbents was calculated to be 10.99 m2/g and the surface was found to be mesoporous. The optimum conditions for adsorption studies including initial pH (2-12), concentration (10-50 mg/L), contact time (0-150 min), and adsorbent mass (0.05 g/50 mL-0.25 g/50 mL) were determined at 25 °C. The raw data obtained from sorption tests were applied to Freundlich, Langmuir-1, Langmuir-2, Langmuir-3, Langmuir-4, Temkin, Toth, and Koble-Corrigan isotherm models. The best results were obtained from the Langmuir-2 and accordingly the qm values were calculated as 454.54, 833.33, and 625.00 mg/g for FA, FA-SA-20, and FA-SA-30 at 25 °C, respectively. Adsorption kinetic data illustrated that the process followed the PSO model. Reusability and desorption studies were performed for composite microbeads. Additionally, the thermodynamic studies were performed at 25, 35 and 45 °C. Considering all these results, it was seen that the FA-SA-20 composite had the highest adsorption capacity and the best desorption efficiency.

Neolamarckia cadamba (cadamba) waste pulp as a natural and techno-economic scavenger for methylene blue from aqueous solutions

In this work, Neolamarckia cadamba (cadamba), also known as bur flower tree has been exercised to demonstrate as an excellent methylene blue scavenger from simulated as well as industrial wastewater. The particle morphology and structural insights were gained from FESEM, BET surface area, FTIR, and pHZPC. The adsorption behavior was mapped by different physico-chemical parameters such as contact time, pH, input concentration, and temperature. Experimental data reveal rapid adsorption, and >90% uptake was successful within the first 15 min and reaches equilibrium by 45 min (removal efficiency = 94.15%) at neutral pH. The maximum adsorption capacity was found to be 115.60 mg/g. The uptake process follows pseudo-second-order kinetics (R2 = 0.99), confirming a chemisorption process while the Langmuir model (R2 = 0.99) satisfactorily addresses the adsorption path. Thermodynamic parameters suggest a spontaneous, feasible, and exothermic process with increased entropy. Spent adsorbent could easily be regenerated in up to 74% using 1:1 MeOH/H2O with a potential of three-cycle use. Real-time efficacy has been established with an MB containing industrial effluent and up to 44.70% adsorption, which confirms the material's practical applicability. Statistical reliability was confirmed by the relative standard deviation. Altogether, the present material offers clean and green removal of methylene blue dye from versatile wastewater.

Augmented dye eradication from wastewater using alkali-aided, reinforced waste acacia (Acacia auriculiformis) leaves

The present investigation demonstrates the augmented dye scavenging from wastewater using alkali-mutated acacia (Acacia auriculiformis) leaves powder. The material was synthesized by mild chemical activation by using 0.1 M sodium hydroxide as an activator under room temperature stirring for 3h and isolated as a dark brown powder. The material was characterized using FTIR, FESEM, XRD, and pHzpc; and tested successfully with crystal violet and methylene blue. While FTIR confirms the presence of polyphenolic and polysaccharide moieties, FESEM reveals unprecedented circular hollow pipe-like channels decorated in a highly ordered fashion, facing pores for optimum dye uptake. The adsorption is tunable with working pH, and the maximum adsorption capacities are 67.25 and 78.55 mg g-1 for CV and MB. Both adsorption process follows Langmuir isotherm (R2 = 0.994) and pseudo-2nd-order kinetics (R2 = 0.999). Thermodynamic analysis verifies a spontaneous process with an endothermic interaction beside an elevated degree of randomness. About 80% of the spent material could be regenerated using 1:1 methanol/water. Analysis of industrial effluent suggests 37% removal per cycle, with an operating ceiling of 95%. To wind up, due to huge availability, porous nature, and superior adsorption capacity over other phytosorbents, NaOH-activated acacia leaves could be considered as techno-economic and potential scavengers for sustainable water treatment.

Methylene Blue Dye Adsorption on Iron Oxide-Hydrochar Composite Synthesized via a Facile Microwave-Assisted Hydrothermal Carbonization of Pomegranate Peels' Waste

The toxicity of dyes has a long-lasting negative impact on aquatic life. Adsorption is an inexpensive, simple, and straightforward technique for eliminating pollutants. One of the challenges facing adsorption is that it is hard to collect the adsorbents after the adsorption. Adding a magnetic property to the adsorbents makes it easier to collect the adsorbents. The current work reports the synthesis of an iron oxide-hydrochar composite (FHC) and an iron oxide-activated hydrochar composite (FAC) through the microwave-assisted hydrothermal carbonization (MHC) technique, which is known as a timesaving and energy-efficient method. The synthesized composites were characterized using various techniques, such as FT-IR, XRD, SEM, TEM, and N2 isotherm. The prepared composites were applied in the adsorption of cationic methylene blue dye (MB). The composites were formed of crystalline iron oxide and amorphous hydrochar, with a porous structure for the hydrochar and a rod-like structure for the iron oxide. The pH of the point of zero charge (pHpzc) of the iron oxide-hydrochar composite and the iron oxide-activated hydrochar composite were 5.3 and 5.6, respectively. Approximately 556 mg and 50 mg of MB dye was adsorbed on the surface of 1 g of the FHC and FAC, respectively, according to the maximum adsorption capacity calculated using the Langmuir model.

A State-of-Art Review of the Metal Oxide-Based Nanomaterials Effect on Photocatalytic Degradation of Malachite Green Dyes and a Bibliometric Analysis

A wide range of hard contaminants in wastewater is generated from different industries as byproducts of the organic compound. In this review, various metal oxide-based nanomaterials are employed for the photocatalytic removal of malachite green (MG) dye from wastewater. Some cost-effective and appropriate testing conditions are used for degrading these hard dyes to get higher removal efficiency. The effects of specific parameters are considered such as how the catalyst is made, how much dye is in the solution at first, how much nanocatalyst is needed to break down the dye, the initial pH of the dye solution, the type of light source used, the year of publications, and how long the dye has to be exposed to light to be removed. This study suggests that Scopus-based core collected data employ bibliometric methods to provide an objective analysis of global MG dye from 2011 to 2022 (12 years). The Scopus database collects all the information (articles, authors, keywords, and publications). For bibliometric analysis, 658 publications are retrieved corresponding to MG dye photodegradation, and the number of publications increases annually. A bibliometric study reveals a state-of-art review of metal oxide-based nanomaterials' effects on photocatalytic degradation of MG dyes (12 years).

Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water

The extract of ficus leaves was used to prepare manganese (IV) oxide nanoparticles (MnO2 NPs) for the first time. Several different analytical techniques were used to characterize the prepared MnO2 NPs. MnO2 has spherical crystals that are ~ 7 nm on average in size and have 149.68 m2/g of surface area and 0.91 cm3/g of total pore volume. Malachite green (MG) dye was then taken out of the water by adsorption using MnO2 NPs. Optimization of various adsorption parameters resulted in 188.68-277.78 mg/g maximum adsorption capacities at 298-328 K tested temperatures and 99.6% removal of 50 mg/L MG within 90 min using MnO2 dose of 0.01 g at pH 10 and 298 K. The results were tested using pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich, and Liquid film kinetic models as well as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The most likely models to describe the adsorption process at 298 K are pseudo-second-order kinetics (R2 = 0.997) with a rate constant of 4 × 10-4 g/(mg.min) and Langmuir isotherm (R2 = 0.973). Additionally, the positive values of enthalpy change (3.91-67.81 kJ/mol) and the negative values of Gibb's free energy (- 3.38 to - 19.7 kJ/mol) indicate that the process is endothermic, spontaneous, and thermodynamically feasible. MnO2 NPs sustained their adsorption efficiency at 90.4% after 5 sorption cycles. MnO2 appears to be more selective for MG in studies examining the adsorption of various cationic dyes. Lately, the biosynthesized MnO2 NPs can be utilized to remove MG from aqueous solutions effectively.

Protein encapsulation of nanocatalysts: A feasible approach to facilitate catalytic theranostics

Enzyme-mimicking nanocatalysts, also termed nanozymes, have attracted much attention in recent years. They are considered potential alternatives to natural enzymes due to their multiple catalytic activities and high stability. However, concerns regarding the colloidal stability, catalytic specificity, efficiency and biosafety of nanomaterials in biomedical applications still need to be addressed. Proteins are biodegradable macromolecules that exhibit superior biocompatibility and inherent bioactivities; hence, the protein modification of nanocatalysts is expected to improve their bioavailability to match clinical needs. The diversity of amino acid residues in proteins provides abundant functional groups for the conjugation or encapsulation of nanocatalysts. Moreover, protein encapsulation can not only improve the overall performance of nanocatalysts in biological systems, but also bestow materials with new features, such as targeting and retention in pathological sites. This review aims to report the recent developments and perspectives of protein-encapsulated catalysts in their functional improvements, modification methods and applications in biomedicine.

Effective mitigation of single-component and mixed textile dyes from aqueous media using recyclable graphene-based nanocomposite

The present study reported the synthesis and utilization of a graphene-based hybrid nanocomposite (MnFe₂O₄/G) to mitigate several synthetic dyes, including methylene blue, malachite green, crystal violet, and Rhodamine B. This adsorbent was structurally analyzed by several physicochemical techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, N₂ adsorption-desorption isotherm measurement, point of zero charge, and Boehm titrations. BET surface area of MnFe₂O₄/G was measured at 382.98 m²/g, which was substantially higher than that of MnFe₂O₄. MnFe₂O₄/G possessed diverse surface chemistry properties with the presence of many functional groups such as carboxylic acid, phenolic, lactone, and basic groups. MnFe₂O₄/G was used to remove synthetic dyes in the aqueous media. The effect of many factors, e.g., concentration (5-50 mg/L), pH (4-10), dose (5-20 mg), and temperature (25-45 °C) on adsorption performance of MnFe₂O₄/G was conducted. Kinetic, isotherm, intraparticle, and thermodynamic models were adopted for investigating adsorption phenomenon of dyes on MnFe₂O₄/G. The maximum adsorption capacity of dyes over MnFe₂O₄/G was found as Rhodamine B (67.8 mg/g) < crystal violet (81.3 mg/g) < methylene blue (137.7 mg/g) < malachite green (394.5 mg/g). Some tests were performed to remove mixed dyes, and mixed dyes in the presence of antibiotics with total efficiencies of 65.8-87.9% after 120 min. Moreover, the major role of π-π stacking interaction was clarified to gain insight into the adsorption mechanism. MnFe₂O₄/G could recycle up to 4 cycles, which may be beneficial for further practical water treatment.

Alkali treated water chestnut (Trapa natans L.) shells as a promising phytosorbent for malachite green removal from water

Search for eco-friendly adsorbents for sustainable dye treatment is on the rise. The present study demonstrated the enhanced removal of malachite green (MG) with alkali-modified shells of water chestnut (AWCN) under optimized physio-chemical parameters. Alkali treatment significantly reduces the lignocellulosic components which in turn increased the water stability. The material was been characterized by pHzpc, FTIR, FESEM-EDAX, and BET surface area analysis. pH-dependent adsorption was noticed and the maximum adsorption capacity was determined as 136.46 mg/g. Adsorption followed pseudo-second-order kinetics (R²=0.99) and Langmuir isotherm model (R²=0.99). Thermodynamic parameters suggested that the adsorption process is spontaneous (ΔG°= -2.99 kJ/mol), favorable and endothermic (ΔH°=34.72 kJ/mol). Simple regeneration allows multi-cycle use with minimal loss of activity. The mechanism has been proposed to be a combination of electrostatic interaction, H-bonding, and π-π stacking between AWCN and MG. In conclusion, alkali modification of Trapa natans L. shells provides excellent removal of MG from water.

Sonophotocatalytic Degradation of Malachite Green by Nanocrystalline Chitosan-Ascorbic Acid@NiFe2O4 Spinel Ferrite

Statistics show that more than 700 thousand tons of dye are produced annually across the globe. Around 10–20% of this is used in industrial processes such as printing and dyeing, while about 50% of the dye produced is discharged into the environment without proper physicochemical treatment. Even trace amounts of dye in water can reduce oxygen solubility and have carcinogenic, mutagenic, and toxic effects on aquatic organisms. Therefore, before dye-containing wastewater is discharged into the environment, it must be properly treated. The present study investigates the green synthesis of nickel ferrite NiFe2O4 (NIFE) spinel magnetic nanoparticles (MNPs) via chemical coprecipitation of a solution of Ni2+/Fe3+ in the presence of a biopolymer blend of chitosan (CT) and ascorbic acid (AS). The magnetic nanomaterial was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy–energy dispersive X-ray analysis (SEM-EDX), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), differential scanning calorimetry (DSC), and vibrating-sample magnetometry (VSM). The material was further explored as a catalyst for the photocatalytic degradation of malachite green (MG) under visible light irradiation coupled with ultrasonic waves. The combination of 90 min of visible solar light irradiation with 6.35 W·mL−1 ultrasonic power at pH 8 resulted in 99% of the photocatalytic efficiency of chitosan-ascorbic acid@NIFE (CTAS@NIFE) catalyst for 70 mg·L−1 MG. The quenching of the photocatalytic efficiency from 98% to 64% in the presence of isopropyl alcohol (IPA) suggested the involvement of hydroxy (•OH) radicals in the mineralization process of MG. The high regression coefficients (R2) of 0.99 for 35, 55, and 70 mg·L−1 MG indicated the sonophotocatalysis of MG by CTAS@NIFE was best defined by a pseudo first-order kinetic model. The mechanism involves the adsorption of MG on the catalyst surface in the first step and thereby mineralization of the MG by the generated hydroxyl radicals (•OH) under the influence of visible radiation coupled with 6.34 W·mL−1 ultrasonic power. In the present study the application of photodegradation process with sonochemistry results in 99% of MG mineralization without effecting the material structure unlike happens in the case adsorption process. So, the secondary pollution (generally happens in case of adsorption) can be avoided by reusing the spent material for another application instead of disposing it. Thus, the ecofriendly synthesis protocol, ease in design of experimentation like use of solar irradiation instead of electric power lamps, reusability and high efficiency of the material suggested the study to be potentially economical for industrial development at pilot scale towards wastewater remediation.

Dewaxed Honeycomb as an Economic and Sustainable Scavenger for Malachite Green from Water

Dewaxed honeycomb powder (HCP) was used as a promising adsorbent for removal of malachite green (MG) from aqueous solution. Raw honeycomb was strategically dewaxed by petroleum ether, and the purified product was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), pH_zpc, and proximate analysis. A high uptake capacity (123 mg/g) was found at neutral pH. Experimental data follow pseudo-second-order kinetics (k ₂ as 0.45 × 10^-2 g/min/mg, R ² = 0.986) and Langmuir isotherm with R ² 0.999. Thermodynamic parameters suggested a spontaneous (ΔG = -26.28 kJ/mol) and exothermic (ΔH = -11.61 kJ/mol) process, which suggests increased randomness (ΔS = 0.0486 kJ/mol) at the solid-liquid interface during the adsorption process. The material can be regenerated by ordinary salt solution (1 M NaCl) and efficiently reused for three cycles with a minimal loss in efficiency. Adsorption mechanism is proposed to be a combination of electrostatic interaction and π-π stacking between aromatic units of HCP and MG. Abundant availability, possibility of wax commercialization, economic sustainability, and comprehensive waste management make HCP an ideal choice for dye decolorization.