One-Step Fabrication of Dual Responsive Lignin Coated Fe₃O₄ Nanoparticles for Efficient Removal of Cationic and Anionic Dyes

Dual-functional lignocellulosic mulch as agricultural plastic alternative for sustained-release of photosensitive pesticide and immobilizing heavy metal ions

The extensive utilization of non-biodegradable plastic agricultural mulch in the past few decades has resulted in severe environmental pollution and a decline in soil fertility. The present study involves the fabrication of environmentally friendly paper-based mulch with dual functionality, incorporating agrochemicals and heavy metal ligands, through a sustainable papermaking/coating technique. The functional paper-based mulch consists of a cellulose fiber web incorporated with Emamectin Benzoate (EB)@ Aminated sodium lignosulfonate (ASL). The spherical microcapsules loaded with the pesticide EB exhibited an optimal core-shell structure for enhanced protection and controlled release of the photosensitizer EB (Sustained release >75 % in 50 h). Meanwhile, the ASL, enriched with metal chelating groups (-COOH, -OH, and -NH2, etc.), served as a stabilizing agent for heavy metal ions, enhancing soil remediation efficiency. The performance of paper-based mulch was enhanced by the application of a hydrophobic layer composed of natural chitosan/carnauba wax, resulting in exceptional characteristics such as superior tensile strength, hydrophobicity, heat insulation, moisture retention, as well as compostability and biodegradability (biodegradation >80 % after 70 days). This study developed a revolutionary lignocellulosic eco-friendly mulch that enables controlled agrochemical release and soil heavy metal remediation, leading to a superior substitute to conventional and non-biodegradable plastic mulch used in agriculture.

Effect of Aminating Lignin Loading with Arbuscular Mycorrhizal Fungi on Soil Aggregate Structure Improvement

Lignin is an important component of plant fiber raw materials, and is a three-dimensional network structure aromatic polymer with abundant resources and a complex structure in nature. Lignin is generally used as industrial waste, and its potential value has not been fully utilized. Modern agriculture extensively uses chemical fertilizers, leading to the gradual degradation of soil fertility and structure, which seriously affects crop growth, nutrient transport, and root respiration function. Based on soil bulk density, porosity, aggregates, and their stability indicators, this study analyzed the effects of aminated industrial lignin and its loading with arbuscular mycorrhizal fungi on soil structure improvement and plant growth. It was hoped that resource-rich lignin could play a beneficial role in improving soil structure and promoting crop growth. The phenolic hydroxyl group of lignin was epoxidized and further aminated to load with arbuscular mycorrhizal fungi. The results indicated that amine-modified lignin could effectively load with arbuscular mycorrhizal fungi. The application of arbuscular mycorrhizal fungi-supported aminated lignin to soil aggregate structure improvement greatly reduced the bulk density of soil, and increased the porosity of soil and the content of large granular soil. Compared with unmodified soil, soil bulk density decreased by 73.08%, the porosity of soil increased by 70.43%, and the content of large granular soil increased by 56.38%. Using the improved soil for corn cultivation efficiently increased the biomass of corn. The plant height was increased by 72.16%, the root-shoot ratio was increased by 156.25%, and other indexes were also improved to varying degrees. The experimental method provides an important basis for the effective utilization of lignin materials in agriculture in the future.

The Use of Various Types of Waste Paper for the Removal of Anionic and Cationic Dyes from Aqueous Solutions

This study examined the possibility of using various types of waste paper-used newsprint (NP), used lightweight coated paper (LWC), used office paper (OP), and used corrugated cardboard (CC)-for the removal of anionic dyes, Acid Red 18 (AR18) and Acid Yellow 23 (AY23), and cationic dyes, Basic Violet 10 (BV10) and Basic Red 46 (BR46), from aqueous solutions. The scope of this research included the characterization of sorbents (FTIR, SEM, BET surface area, porosity, pHPZC, effectiveness of water coloration), determination of pH effect on the effectiveness of dye sorption, sorption kinetics (pseudo-first-order model, second-order model, intraparticular diffusion model), and the maximum sorption capacity (Langmuir models and Freundlich model) of the tested sorbents. The use of waste paper materials as sorbents was found to not pose any severe risk of aquatic environment contamination. AR18, AY23, and BV10 sorption intensities were the highest at pH 2, and that of RB46 at pH 6. The waste paper sorbents proved particularly effective in removing cationic dyes, like in the case of, e.g., NP, which had a sorption capacity that reached 38.87 mg/g and 90.82 mg/g towards BV10 and BR46, respectively, and were comparable with that of selected activated carbons (literature data).

Adsorption Studies on the Removal of Anionic and Cationic Dyes from Aqueous Solutions Using Discarded Masks and Lignin

The carbon materials derived from discarded masks and lignin are used as adsorbent to remove two types of reactive dyes present in textile wastewater: anionic and cationic. This paper introduces the results of batch experiments where Congo red (CR) and Malachite green (MG) are removed from wastewater onto the carbon material. The relationship between adsorption time, initial concentration, temperature and pH value of reactive dyes was investigated by batch experiments. It is discovered that pH 5.0-7.0 leads to the maximum effectiveness of CR and MG removal. The equilibrium adsorption capacities of CR and MG are found to be 232.02 and 352.11 mg/g, respectively. The adsorption processes of CR and MG are consistent with the Freundlich and Langmuir adsorption models, respectively. The thermodynamic processing of the adsorption data reveals the exothermic properties of the adsorption of both dyes. The results show that the dye uptake processes follow secondary kinetics. The primary adsorption mechanisms of MG and CR dyes on sulfonated discarded masks and alkaline lignin (DMAL) include pore filling, electrostatic attraction, π-π interactions and the synergistic interactions between the sulphate and the dyes. The synthesized DMAL with high adsorption efficiency is promising as an effective recyclable adsorbent for adsorbing dyes, especially MG dyes, from wastewater.

pH-responsive magnetic Fe3O4/carboxymethyl chitosan/aminated lignosulfonate nanoparticles with uniform size for targeted drug loading

In order to improve the effect of anti-tumor drugs, a magnetic delivery system for targeted drug was reported. Firstly, aminated lignosulfonate (ALS) and carboxymethyl chitosan (CMCS) were used to fabricate nano Fe₃O₄ to obtain pH-responsive magnetic Fe₃O ₄ /CMCS/ALS nanoparticles. Then the nanoparticles were loaded with doxorubicin hydrochloride (DOX), realizing the targeted delivery and controlled release of anti-tumor drugs. It was found that the amount of crosslinking agent and emulsifier were the key factors affecting the morphology and size of the magnetic nanoparticles. Under optimized conditions, the particle size was about 79.9-169.9 nm, exhibiting excellent pH responsiveness. When the drug-to-material ratio was 11:10, the DOX loading rate and the encapsulation rate of the nanoparticles was 48.68 % and 86.23 %. While the Fe₃O₄ /CMCS/ALS-DOX particles could release 63.14 %, 56.71 %, and 14.28 % of DOX at pH 4.0, 5.3, and 7.4, respectively. The results showed that the Fe₃O₄ /CMCS/ALS particles exhibited excellent drug loading and release behavior based on the pH responsiveness, which could be described by Langmuir adsorption model and Fick's law of diffusion respectively. MTT assay and Live/dead staining experiments also showed that the drug-loaded particles had obvious growth inhibition on cancer cells.

Rapid and Efficient Removal of Anionic Dye in Water Using a Chitosan-Coated Iron Oxide-Immobilized Polyvinylidene Fluoride Membrane

Anionic dyes are one of the most serious contaminants in water as these molecules are known to be toxic to many living organisms. Herein, we report the development of functionalized polyvinylidene fluoride membranes modified with chitosan-coated iron oxide nanomaterials (Fe-PVDF) for the efficient treatment of anionic dye-contaminated water. Aqueous solutions of anionic dyes could be captured rapidly by passing through the functionalized membrane under reduced pressure. Under neutral conditions, Fe-PVDF showed a maximum removal capacity of 74.6 mg/g for Evans blue (EB) through the adsorption process. In addition, the adsorption capacity was significantly enhanced up to 434.78 mg/g under acidic conditions. The adsorption process for EB matched well with the Langmuir model, indicating monolayer adsorption of the dye to the membrane surface. Moreover, Fe-PVDF can be reusable by a simple washing step in an alkaline solution, and thus, the composite membrane was applied several times without a significant decrease in its adsorption performance. The same composite membrane was further applied to the removal of five other different anionic dyes with high efficiencies. The adsorption mechanism can be explained by the electrostatic interaction between the positively charged chitosan and the negatively charged dye as well as the affinity of the sulfate groups in dye molecules for the surface of the iron oxide nanoparticles. The easy preparation and rapid decolorization procedures make this composite membrane suitable for efficient water treatment.

Multifunctional lignin-based nanocomposites and nanohybrids

Significant progress in lignins valorization and development of high-performance sustainable materials have been achieved in recent years. Reports related to lignin utilization indicate excellent prospects considering green chemistry, chemical engineering, energy, materials and polymer science, physical chemistry, biochemistry, among others. To fully realize such potential, one of the most promising routes involves lignin uses in nanocomposites and nanohybrid assemblies, where synergistic interactions are highly beneficial. This review first discusses the interfacial assembly of lignins with polysaccharides, proteins and other biopolymers, for instance, in the synthesis of nanocomposites. To give a wide perspective, we consider the subject of hybridization with metal and metal oxide nanoparticles, as well as uses as precursor of carbon materials and the assembly with other biobased nanoparticles, for instance to form nanohybrids. We provide cues to understand the fundamental aspects related to lignins, their self-assembly and supramolecular organization, all of which are critical in nanocomposites and nanohybrids. We highlight the possibilities of lignin in the fields of flame retardancy, food packaging, plant protection, electroactive materials, energy storage and health sciences. The most recent outcomes are evaluated given the importance of lignin extraction, within established and emerging biorefineries. We consider the benefit of lignin compared to synthetic counterparts. Bridging the gap between fundamental and application-driven research, this account offers critical insights as far as the potential of lignin as one of the frontrunners in the uptake of bioeconomy concepts and its application in value-added products.

Synthesis of a Lignin-Fe/Mn Binary Oxide Blend Nanocomposite and Its Adsorption Capacity for Methylene Blue

A high-performance modified lignin adsorbent was prepared through coprecipitation of ferrous, ferric, and permanganate with lignin in sodium hydroxide solution. The structural characteristics of the synthesized lignin-Fe/Mn binary oxide blend nanocomposite (L-F/M) and its performance on the methylene blue (MB) removal from aqueous solution were evaluated. Influence factors of adsorption effects were analyzed including pH, contact time, dye concentration, temperature, and thermodynamics. The pseudo-second-order kinetic model well described the adsorption kinetics, and the adsorption isotherms best fitted the Langmuir model with a maximum adsorption capacity of 252.05 mg g-1 at 298 K. The adsorption mechanism showed that the L-F/M introduced the metallic element and negative charges to the lignin surface, which improved the adherence of MB via hydrogen bonding, electrostatic interaction, and coordination. Moreover, the removal ratio of MB maintained 81.2% after being used in five adsorption-desorption cycles. Results indicated that the L-F/M obtained was an efficient candidate for dye wastewater treatment.

Facile fabrication and characterization of kraft lignin@Fe3O4 nanocomposites using pH driven precipitation: Effects on increasing lignin content

This work offers a facile fabrication method for lignin nanocomposites through the assembly of kraft lignin onto magnetic nanoparticles (Fe3O4) based on pH-driven precipitation, without needing organic solvents or lignin functionalization. Kraft lignin@Fe3O4 multicore nanocomposites fabrication proceeded using a simple, pH-driven precipitation technique. An alkaline solution for kraft lignin (pH 12) was rapidly injected into an aqueous-based Fe3O4 nanoparticle colloidal suspension (pH 7) under constant mixing conditions, allowing the fabrication of lignin magnetic nanocomposites. The effects of increasing lignin to initial Fe3O4 mass content (g/g), increasing in ratio from 1:1 to 20:1, are discussed with a complete chemical, structural, and morphological characterization. Results showed that nanocomposites fabricated above 5:1 lignin:Fe3O4 had the highest lignin coverage and content (>20%), possessed superparamagnetic properties (Ms ≈ 45,000 A·m2/kg2); had a negative surface charge (-30 mV), and formed multicore nanostructures (DH ≈ 150 nm). The multicore lignin@Fe3O4 nanocomposites allowed rapid magnetically induced separations from suspension. After 5 min exposure to a rare-earth neodymium magnet (1.27 mm × 1.27 mm × 5.08 mm), lignin@Fe3O4 nanocomposites exhibited a maximum methylene blue removal efficiency of 74.1% ± 7.1%. These nanocomposites have potential in magnetically induced separations to remove organic dyes, heavy metals, or other lignin adsorbates.

Potential of Scenedesmus-fabricated ZnO nanorods in photocatalytic reduction of methylene blue under direct sunlight: kinetics and mechanism

Organic synthetic dyes are widely used in several industries; however, their inherent resistance to biodegradation necessitates to investigate alternative methods for the remediation of this class of hazardous substances. In the present study, a green synthesis of ZnO nanorods was achieved in a fast, environment-friendly, and safe microwave process employing algal extract. Different metabolites like sugars, proteins, fatty acids, amino acids, and vitamins present in the algal extract reduced the Zn²⁺ into ZnO. The XRD analysis showed that the nanostructure was a crystalline hexagonal nanorod having a crystalline size of 27.37 nm. The XPS spectra of ZnO nanorod showed characteristic peaks at binding energy 1043, 1020, 496, 137, 87, and 8 eV corresponding to Zn2p_1/2, Zn2p_3/2, Zn_LMM, Zn_3s, Zn_3p, Zn_3d, respectively. The synthesized ZnO nanorods were in-situ functionalized and showed strong catalytic activity in photoreduction of a model organic dye methylene blue (MB) under direct sunlight irradiation. Synthesized ZnO nanorods showed a complete (100%) reduction of model dye MB from its 10 mg/L aqueous solution. The photocatalytic degradation of MB followed the Michaelis-Menten kinetics. The rate of ZnO-catalyzed photocatalytic degradation depends on the concentrations of ZnO, pH, and sunlight irradiation. The ZnO nanorod-catalyzed photoreduction of MB involves hydroxyl radicals. Algal-mediated and microwave-assisted synthesis provides a scalable source of metal oxide nanoparticles for the remediation of dye-containing wastewaters under natural sunlight. Apart from application in the removal of dyes, ZnO nanorods are excellent material for applications in semiconductors, electronics, optics, bio-imaging, and drug delivery.

One-pot preparation of hydrophobic lignin/SiO2 nanoparticles and its reinforcing effect on HDPE

Nano silica (SiO₂) is usually used as a common reinforcing agent in polymer materials, in which the interfacial interaction greatly affects the mechanical properties of the composites. The reinforcement effect of silica on non-polar polymer is restricted due to their poor compatibility. In this work, amphipathic lignin modified by quaternization and alkylation was used as a modifier for silica to prepare hydrophobic lignin/SiO₂ nanoparticles by in-situ one-pot co-precipitation method. In alkaline solution, hydrophobic lignin and SiO₂ (from Na₂SiO₃) were self-assembled to form nanospheres through electrostatic and hydrophobic interactions. The results showed that the lignin/SiO₂ nanoparticles were highly hydrophobic nanospheres with macropores in the surface. When the lignin/SiO₂ nanoparticles (10 wt%) were added to reinforce high-density polyethylene (HDPE), the mechanical properties of HDPE were improved with the strength of 24.5 MPa and the elongation of 1096%, which were increased by 10.4% and 14.3% compared with the control HDPE, because of the good compatibility and large bonding area. This work puts forward a new solution for the application of lignin in reinforcement of non-polar polymers.

Lignin-derived (nano)materials for environmental pollution remediation: Current challenges and future perspectives

The supply of affordable drinking and sufficiently clean water for human consumption is one of the world's foremost environmental problems and a large number of scientific research works are addressing this issue Various hazardous/toxic environmental contaminants in water bodies, both inorganic and organic (specifically heavy metals and dyes), have become a serious global problem. Nowadays, extensive efforts have been made to search for novel, cost effective and practical biosorbents derived from biomass resources with special attention to value added, biomass-based renewable materials. Lignin and (nano)material adorned lignin derived entities can proficiently and cost effectively remove organic/inorganic contaminants from aqueous media. As low cost of preparation is crucial for their wide applications in water/wastewater treatment (particularly industrial water), future investigations must be devoted to refining and processing the economic viability of low cost, green lignin-derived (nano)materials. Production of functionalized lignin, lignin supported metal/metal oxide nanocomposites or hydrogels is one of the effective approaches in (nano)technology. This review outlines recent research progresses, trends/challenges and future prospects about lignin-derived (nano)materials and their sustainable applications in wastewater treatment/purification, specifically focusing on adsorption and/or catalytic reduction/(photo)degradation of a variety of pollutants.

Novel Mesoporous Lignin-Calcium for Efficiently Scavenging Cationic Dyes from Dyestuff Effluent

A novel adsorbent lignin-calcium was fabricated by a simple flocculation-sedimentation approach to remove methylene blue. The structure and morphology of the well-prepared sample were analyzed by multiple characterization methods. Lignin-calcium microspheres demonstrated a mesoporous and inserted layer structure with a coarse surface. Methylene blue (MB) adsorption by lignin-calcium complied with the Langmuir model, showing a maximum adsorption amount of 803.9 mg/g, exceeding that reported in the literature by 3-22-fold. The adsorption kinetics matched the pseudo-second-order model well. The pore volume diffusion model was technically applied to evaluate the mass transfer mechanisms. The effective pore volume diffusion coefficient was 6.28 × 10^-12 m²/s. Furthermore, lignin-calcium exhibited excellent adsorbability for methylene blue across a pH range from 3 to 11 and could be regenerated by hydrochloric acid with an elution efficiency of 62.44%. Multiple mechanisms may support the adsorption. Altogether, the tailor-made lignin-calcium is promising as an efficient and sustainable adsorbent for scavenging cationic dyes from dyestuff effluent.

Sulfonated Cellulose-Based Magnetic Composite as Useful Media for Water Remediation from Amine Pollutants

Commercially available microcrystalline cellulose (MCC) was functionalized using chlorosulfonic acid, while iron oxide nanoparticles (IONPs) were adsorbed on the surface of the cellulose derivative by the Massart’s co-precipitation method. The obtained magnetite-decorated sulfate cellulose nanoparticles (MDSCNs) were characterized via Fourier transform infrared (FTIR) spectroscopy, scanning-electron microscopy (SEM), and elemental analysis, while the acidity of the functionalized cellulose was determined using an acid–base titration with phenolphthalein as an indicator. Furthermore, in order to determine the adsorptive power of the obtained composite, a series of analyses were performed on aqueous amine pollutants using flame ionization detection gas chromatography (GC-FID). The results of this study clearly show how a bio-compatible green polymer as cellulose can be easy functionalized in order to improve its chemical and physical properties, obtaining a magnetic composite useful in water purification. Adsorption percentages up to 90% and a very small amount of composite used (100 mg) proved how our material can be a powerful tool in environmental remediation.

Synthesis, Characterization, and Utilization of a Lignin-Based Adsorbent for Effective Removal of Azo Dye from Aqueous Solution

How to effectively remove toxic dyes from the industrial wastewater using a green low-cost lignocellulose-based adsorbent, such as lignin, has become a topic of great interest but remains quite challenging. In this study, cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment and Mannich reaction were combined to generate an aminated CELF lignin which is subsequently applied for removal of methylene blue and direct blue (DB) 1 dye from aqueous solution. ³¹P NMR was used to track the degree of amination, and an orthogonal design was applied to determine the relationship between the extent of amination and reaction parameters. The physicochemical, morphological, and thermal properties of the aminated CELF lignin were characterized to confirm the successful grafting of diethylenetriamine onto the lignin. The aminated CELF lignin proved to be an effective azo dye-adsorbent, demonstrating considerably enhanced dye decolorization, especially toward DB 1 dye (>90%). It had a maximum adsorption capacity of DB 1 dye of 502.7 mg/g, and the kinetic study suggested the adsorption process conformed to a pseudo-second-order kinetic model. The isotherm results also showed that the modified lignin-based adsorbent exhibited monolayer adsorption. The adsorbent properties were mainly attributed to the incorporated amine functionalities as well as the increased specific surface area of the aminated CELF lignin.

Iron Oxide/Chitosan Magnetic Nanocomposite Immobilized Manganese Peroxidase for Decolorization of Textile Wastewater

Because of its effectiveness in organic pollutant degradation, manganese peroxidase (MnP) enzyme has attracted significant attention in recent years regarding its use for wastewater treatment. Herein, MnP was extracted from Anthracophyllum discolor fungi and immobilized on the surface of magnetic nanocomposite Fe3O4/chitosan. The prepared nanocomposite offered a high surface area for MnP immobilization. The influence of several environmental factors like temperature, pH, as well as storage duration on the activity of the extracted enzyme has been studied. Fourier transmission infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM) techniques were used for the characterization of the prepared MnP/Fe3O4/chitosan nanocomposite. The efficiencies of the prepared MnP/Fe3O4/chitosan nanocomposite for the elimination of reactive orange 16 (RO 16) and methylene blue (MB) industrial dyes were determined. According to the results, the immobilization of MnP on Fe3O4/chitosan nanocomposite increases its capacity to decolorize MB and RO 16. This nanocomposite allowed the removal of 96% ± 2% and 98% ± 2% of MB and RO 16, respectively. The reusability of the synthesized nanocomposite was studied for five successive cycles showing the ability to retain its efficiency even after five cycles. Thus, the prepared MnP/Fe3O4/chitosan nanocomposite has potential to be a promising material for textile wastewater bioremediation.

Synthesis of Chitosan-Ignosulfonate Composite as an Adsorbent for Dyes and Metal Ions Removal from Wastewater

Sodium lignosulfonate is a polymer with extensive sources and abundant functional groups. Therefore, it has potential value for research and wide utilization. In this study, the adsorption material was prepared by blending sodium lignosulfonate and chitosan, which could adsorb anionic and cationic dyes and metal ions. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetry (TG). The results showed that the composite was cross-linked mainly by the strong electrostatic interaction between the protonated amino group in chitosan and the sulfonate group in sodium lignosulfonate. Moreover, the effects of initial concentration, adsorption time, initial pH, and mass ratio of chitosan to sodium lignosulfonate on the adsorption performance of the composite were investigated. Meanwhile, the adsorption processes were agreed well with the pseudo-second-order kinetic model and Langmuir isotherm model. The adsorption mechanism was that the electrostatic interaction between the protonated amino and hydroxyl groups of the composite with anionic (SO3 -) and HCrO4 - groups of Congo red and Cr(VI), respectively. In addition, the electrostatic interaction between SO3 - of the composite and positively charged group of Rhodamine B played an important role in the adsorption of Rhodamine B.

Mesoporous silicate/carbon composites derived from dye-loaded palygorskite clay waste for efficient removal of organic contaminants

Palygorskite (Pal) is a natural abundant environment-friendly adsorbent that has shown high efficiency to decontaminate dye in water. However, the dye removal results in transformation of Pal to a very stable Maya Blue-like structure or waste Pal clay (WPal), which could not be easily regenerated by a commonly used desorption process. This paper presents a use of WPal as the precursor material to synthesize a highly-efficient mesoporous silicate/carbon composite adsorbent. The composite adsorbent has a large specific surface area (427.9 m²·g^-1), a high negative potential (-40.6 mV) and a mesoporous size (3.48 nm). This adsorbent shows almost complete removal of tetracycline (TC), crystal violet (CV) and methylene blue (MB) (initial concentration, 200 mg·L^-1) with the optimal adsorption capacities of 319.8 mg·g^-1, 244.4 mg·g^-1 and 281.7 mg·g^-1, respectively. The active -Si-O^- adsorption sites produced by the breaking of inert Si-O-Si (or M) bonds and the electrostatic interactions of negatively charged adsorbents to adsorbates play a major role in the adsorption process. Adsorption capacities of the developed composite are significantly higher than that of Pal, WPal and hydrothermally treated WPal (HWPal). Results demonstrate that the composite adsorbents have high potential in decontamination of organics in water efficiently.

Effect of the Surface Charge on the Adsorption Capacity of Chromium(VI) of Iron Oxide Magnetic Nanoparticles Prepared by Microwave-Assisted Synthesis

Solid phase extraction using magnetic nanoparticles has represented a leap forward in terms of the improvement of water quality, preventing the contamination of industrial effluents from discharge in a more efficient and affordable way. In the present work, superparamagnetic iron oxide nanoparticles (MNP) with different surface charges are tested as nanosorbents for the removal of chromium(VI) in aqueous solution. Uniform magnetic nanoparticles (~12 nm) were synthesized by a microwave polyol-mediated method, and tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) were grafted onto their surface, providing a variation in the surface charge. The adsorptive process of chromium was evaluated as a function of the pH, the initial concentration of chromium and contact time. Kinetic studies were best described by a pseudo-second order model in all cases. TEOS@MNP barely removed the chromium from the media, while non-grafted particles and APTES@TEOS@MNP followed the Langmuir model, with maximum adsorption capacities of 15 and 35 mgCr/g, respectively. The chromium adsorption capacities abruptly increased when the surface became positively charged as the species coexisting at the experimental pH are negatively charged. Furthermore, these particles have proven to be highly efficient in water remediation due their 100% reusability after more than six consecutive adsorption/desorption cycles.

Continuous Flow Removal of Anionic Dyes in Water by Chitosan-Functionalized Iron Oxide Nanoparticles Incorporated in a Dextran Gel Column

This paper describes a novel chromatographic method for efficient removal of anionic dyes from aqueous solutions. Chitosan-coated Fe₃O₄ nanoparticles can easily be immobilized on a dextran gel column. Single elution of Evans Blue (EB) solution to the nanoadsorbent-incorporated columns provides high removal efficiency with a maximum adsorption capacity of 243.9 mg/g. We also investigated the influence of initial concentration and solution pH on the removal efficiency of EB. The electrostatic interaction between the adsorbent surface and negatively charged sulfate groups on EB molecules promotes the efficient adsorption of dyes. The equilibrium data matched well with the Langmuir isotherm model, which indicated monolayer dye adsorption onto the adsorbent surface. To extend the application of the current method, we performed further adsorption experiments using other anionic dyes of different colors (Cy5.5, Acid Yellow 25, Acid Green 25, and Acid Red 1). All of these molecules can efficiently be captured under continuous flow conditions, with higher removal efficiency obtained with more negatively charged dyes. These findings clearly demonstrate that the present approach is a useful method for the removal of anionic dye contaminants in aqueous media by adsorption.

Fabrication of magnetic lignosulfonate using ultrasonic-assisted in situ synthesis for efficient removal of Cr(Ⅵ) and Rhodamine B from wastewater

A novel and eco-friendly one-step approach has been developed to fabricate magnetic lignosulfonate (MLS) with high performance in wastewater treatment. The obtained MLS was characterized by FTIR, XRD, SEM, TEM, VSM. The results showed that MLS had a good magnetic behavior in an applied magnetic field and its saturation magnetization intensity was up to 43.98 emu/g. Moreover, MLS exhibited excellent adsorption properties for Cr(Ⅵ) (57.14 mg/g) and Rhodamine B (22.47 mg/g). Simultaneously, the adsorption kinetics and adsorption isotherm experiments indicated that the data was agreed well with the pseudo-second-order and Langmuir model, respectively. After five regeneration cycles, the desorption efficiencies of Cr(Ⅵ) and Rhodamine B could reach more than 70% and 85%, respectively. Hence, the magnetic lignosulfonate is a promising material as a highly adsorptive and recyclable adsorbent for removing metal ions and cationic pollutants in wastewater.

Data on the removal of Optilan Blue dye from aqueous media using starch-coated green synthesized magnetite nanoparticles

In this data article, we present supplementary data related to the research article entitled "Starch-coated green synthesized magnetite nanoparticles for removal of textile dye Optilan Blue from aqueous media" Stan et al., 2019. Data interpretations are included in the related research article Stan et al., 2019. The synthesized starch-coated Fe3O4 nanoparticles (ST-coated Fe3O4 NPs) were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) to illustrate the shape and surface coating of nanoparticles. Moreover, the Brunauer-Emmett-Teller (BET) technique was used to evidence starch deposition on magnetite nanoparticles. The obtained nanocomposites were used for adsorption of Optilan Blue (OB) in batch conditions and the optimum agitation speed and point of zero charge (pHpzc) were established. After OB adsorption on ST-coated Fe3O4 NPs, the nanocomposites were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The stability of starch coated Fe3O4 NPs in the acidic as well as alkaline pH was also evidenced by FTIR spectroscopy. In addition, to test the stability of ST-coated Fe3O4 NPs, leaching experiments were carried out. The experimental data were compared with isotherm and kinetic models in order to determine the most suitable for fitting.

Preparation of a Stable Nanoscale Manganese Residue-Derived FeS@Starch-Derived Carbon Composite for the Adsorption of Safranine T

To develop a novel, low-cost adsorbent with natural material and industrial waste as raw materials, nanoscale manganese residue-derived FeS@starch-derived carbon (MR–FeS@SC) composite was prepared by the carbonization of starch–manganese residue gel. Manganese residue-derived FeS (MR–FeS) and starch-derived carbon (SC) were also prepared as contrasts for comparative studies. The MR–FeS@SC nanocomposite exhibited relatively large specific surface area and micropore volume, appropriate pore size, abundant functional groups, strong interaction between the functional groups of SC and MR–FeS, and the immobilization and uniform distribution of MR–FeS nanoparticles onto SC support material, which contributed to better adsorption properties for the removal of Safranine T (ST) from the aqueous solution compared with those of MR–FeS and SC. The adsorption could be conducted at a wide range of pH and temperature to achieve a satisfy removal efficiency of ST with MR–FeS@SC nanocomposite as adsorbent. The adsorption kinetics well followed the pseudo-second-order model, and the dominant mechanism was chemisorption. The adsorption behavior was well described by the Langmuir isotherm model. Due to the strong interaction between MR–FeS nanoparticles and SC support, MR–FeS@SC nanocomposite exhibited better reusability and stability even after fifteen cycles. This study provides a facile method of preparing effective and stable adsorbents for the treatment of dye wastewater.

In Situ Synthesis of a Stable Fe₃O₄@Cellulose Nanocomposite for Efficient Catalytic Degradation of Methylene Blue

To rapidly obtain a stable Fe₃O₄@cellulose heterogeneous Fenton catalyst, a novel in situ chemical co-precipitation method was developed. Compared with mechanical activation (MA)-pretreated cellulose (MAC), MA + FeCl₃ (MAFC)-pretreated cellulose (MAFCC) was more easily dissolved and uniformly distributed in NaOH/urea solvent. MAFCC and MAC solutions were used as precipitators to prepare Fe₃O₄@MAFCC and Fe₃O₄@MAC nanocomposites, respectively. MAFCC showed stronger interaction and more uniform combination with Fe₃O₄ nanoparticles than MAC, implying that MAFC pretreatment enhanced the accessibility, reactivity, and dissolving capacity of cellulose thus, provided reactive sites for the in situ growth of Fe₃O₄ nanoparticles on the regenerated cellulose. Additionally, the catalytic performance of Fe₃O₄@MAFCC nanocomposite was evaluated by using for catalytic degradation of methylene blue (MB), and Fe₃O₄@MAC nanocomposite and Fe₃O₄ nanoparticles were used for comparative studies. Fe₃O₄@MAFCC nanocomposite exhibited superior catalytic activity for the degradation and mineralization of MB in practical applications. After ten cycles, the structure of Fe₃O₄@MAFCC nanocomposite was not significantly changed owing to the strong interaction between MAFCC and Fe₃O₄ nanoparticles. This study provides a green pathway to the fabrication of a stable nanocomposite catalyst with high catalytic performance and reusability for the degradation of organic pollutants.

Enhanced Catalytic Reduction of 4-Nitrophenol Driven by Fe₃O₄-Au Magnetic Nanocomposite Interface Engineering: From Facile Preparation to Recyclable Application

In this work, we report the enhanced catalytic reduction of 4-nitrophenol driven by Fe₃O₄-Au magnetic nanocomposite interface engineering. A facile solvothermal method is employed for Fe₃O₄ hollow microspheres and Fe₃O₄-Au magnetic nanocomposite synthesis via a seed deposition process. Complementary structural, chemical composition and valence state studies validate that the as-obtained samples are formed in a pure magnetite phase. A series of characterizations including conventional scanning/transmission electron microscopy (SEM/TEM), Mössbauer spectroscopy, magnetic testing and elemental mapping is conducted to unveil the structural and physical characteristics of the developed Fe₃O₄-Au magnetic nanocomposites. By adjusting the quantity of Au seeds coating on the polyethyleneimine-dithiocarbamates (PEI-DTC)-modified surfaces of Fe₃O₄ hollow microspheres, the correlation between the amount of Au seeds and the catalytic ability of Fe₃O₄-Au magnetic nanocomposites for 4-nitrophenol (4-NP) is investigated systematically. Importantly, bearing remarkable recyclable features, our developed Fe₃O₄-Au magnetic nanocomposites can be readily separated with a magnet. Such Fe₃O₄-Au magnetic nanocomposites shine the light on highly efficient catalysts for 4-NP reduction at the mass production level.

Highly Efficient, Low-Cost, and Magnetically Recoverable FePt⁻Ag Nanocatalysts: Towards Green Reduction of Organic Dyes

Nowadays, synthetic organic dyes and pigments discharged from numerous industries are causing unprecedentedly severe water environmental pollution, and conventional water treatment processes are hindered due to the corresponding sophisticated aromatic structures, hydrophilic nature, and high stability against light, temperature, etc. Herein, we report an efficient fabrication strategy to develop a new type of highly efficient, low-cost, and magnetically recoverable nanocatalyst, i.e., FePt⁻Ag nanocomposites, for the reduction of methyl orange (MO) and rhodamine B (RhB), by a facile seed deposition process. X-ray diffraction results elaborate that the as-synthesized FePt⁻Ag nanocomposites are pure disordered face-centered cubic phase. Transmission electron microscopy studies demonstrate that the amount of Ag seeds deposited onto the surfaces of FePt nanocrystals increases when increasing the additive amount of silver colloids. The linear correlation of the MO and RhB concentration versus reaction time catalyzed by FePt⁻Ag nanocatalysts is in line with pseudo-first-order kinetics. The reduction rate constants of MO and RhB increase with the increase of the amount of Ag seeds. FePt⁻Ag nanocomposites show good separation ability and reusability, and could be repeatedly applied for nearly complete reduction of MO and RhB for at least six successive cycles. Such cost-effective and recyclable nanocatalysts provide a new material family for use in environmental protection applications.