Stable and recyclable lanthanum hydroxide-doped graphene oxide biopolymer foam for superior aqueous arsenate removal: Insight mechanisms, batch, and column studies

In this study, a graphene oxide-based lanthanum hydroxide/chitosan foam (CSGOL foam) was synthesized for arsenate (As(V)) remediation in surface water. The synthesized CSGOL foam texture and purity was assessed using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) studies. The results proved that the foam was highly porous, stable, and had high surface functionality that facilitated adsorption for water pollutant removal. The sorption results proved that the As(V) removal was high (146.20 mg/g at pH 6 with 0.5 g/L CSGOL foam) when compared to the similar type of materials, endothermic chemisorption due to the production of monodentate and bidentate inner-sphere complexes. Furthermore, continuous column results indicated that the As(V) concentration in real surface waters was reduced to WHO standards (less than 10 μg As/L of water) of As(V) in drinking water for up to 10,000 bed volume. Further it can be used up to four cycles without loss of efficacy less than 93%. Because of its excellent removal capabilities and simple synthesis technique, CSGOL foam shows significant promise for treating As(V)-containing water. Further, the XPS analysis and batch studies results suggests that As(V) removal mechanism was involved electrostatic and surface complexation through chemical interaction predominately.

Magnesium ferrite-nitrogen-doped graphene oxide nanocomposite: effective adsorptive removal of lead(II) and arsenic(III)

Magnetic nanocomposites have received immense interest as adsorbents for water decontamination. This paper presents adsorptive properties of nitrogen-doped graphene oxide (N-GO) with magnesium ferrite (MgFe₂O₄) magnetic nanocomposite for removing lead(II) (Pb(II)and arsenite As(III) ions. Transmission electron microscope (TEM) image of synthesized nanocomposite revealed the wrinkled sheets of N-GO containing MgFe₂O₄ nanoparticles (NPs) with particle size of 5-15 nm distributed over its surface. This nanocomposite displayed higher BET surface area (72.2 m²g^-1) than that of pristine MgFe₂O₄ NPs (38.4 m²g^-1). Adsorption on the nanocomposite could be described by the Langmuir isotherm with the maximum adsorption capacities were 930 mg/g, and 64.1 mg/g for Pb(II) and As(III), respectively. Whereas, maximum removal efficiencies were observed to be 99.7 [Formula: see text] 0.2% and 93.5 [Formula: see text] 0.1% for Pb(II) and As(III), respectively. The study on the effect of coexisting anions on the adsorption of metal ions showed that the phosphate ions were potential competitors of Pb(II) and As(III) ions to adsorb on the nanocomposite. Significantly, the investigation on adsorption of metal ion in the presence of coexisting heavy metal ions indicated the preferential adsorption of Pb(II) ions as compared to Cd(II), Zn(II) and Ni(II) ions. The effectiveness of the nanocomposite to remove the metal ions in electroplating wastewater was demonstrated.

Polyvinyl Alcohol Polymer Functionalized Graphene Oxide Decorated with Gadolinium Oxide for Sequestration of Radionuclides from Aqueous Medium: Characterization, Mechanism, and Environmental Feasibility Studies

Uranium (U(VI)) and thorium (Th(IV)) ions produced by the nuclear and mining industries cause water pollution, thereby harming the environment and human health. In this study, gadolinium oxide-decorated polyvinyl alcohol-graphene oxide composite (PGO-Gd) was developed using a simple hydrothermal process to treat U(VI) and Th(IV) ions in water. The developed material was structurally characterized by highly advanced spectroscopy and microscopy techniques. The effects of pH, equilibration time and temperature on both radionuclides (U(VI) and Th(IV)) adsorption by PGO-Gd were examined. The PGO-Gd composite adsorbed both metal ions satisfactorily, with adsorption capacities of 427.50 and 455.0 mg g-1 at pH 4.0, respectively. The adsorption properties of both metal ions were found to be compatible with the Langmuir and pseudo-second-order kinetic models. Additionally, based on the thermodynamic characteristics, the adsorption was endothermic and spontaneous. Furthermore, the environmental viability of PGO-Gd and its application was demonstrated by studying its reusability in treating spiked surface water. PGO-Gd shows promise as an adsorbent in effectively removing both radionuclides from aqueous solutions.

Magnetic polymeric core-shell as a carrier for gradual release in-vitro test drug delivery

At first functionalized graphene oxide was selected as a basic substrate obtained through process of functionalization of graphene oxide with diethylenetriamine as substrates. Then magnetic nanoparticle sediments were formed and coated on the functionalized graphene oxide as the core center. The core nanoparticle was added to a gel containing poly (lactic-co-glycolic acid), polyethylene glycol, and polyvinylpyrrolidone and nilotinib drug for forming a shell on the core. After separation and freeze-drying, single core-shell particles were obtained. The second shell was coated by dispersing first core-shell in a new gel containing polylactic acid, polyvinyl alcohol, polyethylene glycol, and nilotinib. The third layer was laminated on core-dual shell particle by entering in sodium alginate, polyethylene glycol, poly (lactic-co-glycolic acid), polylactic acid and nilotinib gel according to the same method used above. In order to determine the gradual release, the core-single, dual and triple shell nanoparticles dispersed in phosphate buffer saline at the several pHs (3, 5.4, 7.4) and as well as monitoring the released concentration of nilotinib by UV-Vis spectrophotometer technique. Core-triple shell particle had gradual release at three different rates over the long time. Finally, the average release rate for 400 mg of drug, in single layer, double-layer and three layers were reported to be equal to 15.8, 10.4 and 6.6 mg/h at intervals of 24, 37 and 60 h, respectively. The release rate of the drug reduced by increasing the pH value. All products were characterized using several techniques.

Adsorption of Lead Ion from Wastewater Using Non-Crystal Hydrated Calcium Silicate Gel

In order to obtain low-cost and excellent adsorption materials, this paper used calcium acetate and water glass as raw materials to synthesis hydrated calcium silicate gel by precipitation method. The performance and structure of hydrated calcium silicate gel were systematically studied by X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, specific surface area analyzer and scanning electron microscope. Studies have shown that, non-crystal hydrated calcium silicate gel (CSH) were successfully prepared, and the removal rate of lead ion using CSH reached more than 90%. The adsorption process is consistent with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, and the limit adsorption capacity reaches 263.17 mg·g-1. The acid treatment experiment proved that the adsorption capacity of lead ion using CSH was satisfactory, and the adsorption rate remained at >60% after 5 cycles. The research may provide a low-cost, high-efficiency and high stability adsorbent.

Potential of the magnetic hollow sphere nanocomposite (graphene oxide-gadolinium oxide) for arsenic removal from real field water and antimicrobial applications

Potential of the magnetic hollow-sphere nanocomposite, graphene oxide-gadolinium oxide (GO-Gd₂O₃) for arsenic (As) removal from real field water with developing a continuous operating system and antimicrobial activity were investigated. The characterization results suggest that the prepared GO-Gd₂O₃ is a hallow sphere wool-like nanocomposite having 50.91 m² g^-1 surface area. The sorption studies revealed that a high adsorption capacity (216.70 mg g^-1) can be achieved using GO-Gd₂O₃ (0.1 g L^-1) at a pH of 6.0, and temperature of 293 K. The main and novel observations from the loading of Gd₂O₃ are that the GO adsorption efficiency, adsorbent separation rate from aqueous solutions, and the stability of the composite have been altered. Thus, the developed material can overcome the separation and stability issues associated with the bare GO, and exhibits an enhanced adsorption capacity toward arsenic was higher or comparable with existing magnetic material. In addition, the developed adsorption method was well applied for real field water samples collected from the mining area of South Korea where the GO-Gd₂O₃ can reduce the quantity of arsenic under the maximum accepted concentration of arsenic considered fit for drinking water stipulated by environmental protection agencies. Furthermore, the GO-Gd₂O₃ nanocomposite shows a high bacterial photocatalytic inactivation and was comparable with other reports.

Facile Synthesis, Characterization, and Adsorption Insights of Lanthanum Oxide Nanorods

This study synthesized lanthanum oxide (La2O3) nanorods to develop a practical approach for the removal of arsenic from groundwater. La2O3 nanorods were synthesized by a simple hydrothermal process followed by calcination at 500 °C and were characterized by spectroscopic and microscopic techniques. To evaluate the adsorption mechanism of La2O3 nanorods, adsorption parameters including solution pH, temperature, equilibrium isotherms, and kinetics for arsenic were studied. The results suggested that the arsenic uptake was a rate-limiting, monolayer adsorption interaction on the La2O3 nanorods homogeneous surface. In addition, it was found that the adsorptive removal behavior of La2O3 for As(V) was sensitive to the initial pH and temperature, and the maximum uptake amount of as prepared La2O3 was found to be 260.56 mg/g of As(V) at pH 6.0 and 25 °C. Furthermore, the uptake capacity of La2O3 nanorods for As(V) increased with temperature. The resultant thermodynamic parameters (ΔG0, ΔH0, and ΔS0) suggested an endothermic adsorption of As(V) on La2O3. The adsorption capacity of La2O3 was higher than that of several reported nanocomposites, suggesting its practical applicability and novelty for As-contaminated wastewater treatment.

Green Activated Magnetic Graphitic Carbon Oxide and Its Application for Hazardous Water Pollutants Removal

Graphitic carbon oxide (GCO) and magnetic graphitic carbon oxide (MGCO) were prepared from sugar via optimized green activation by employing ozone oxidation, and applied to wastewater treatment. The maximal oxidation and adsorption yield of pollutants were achieved at pH 2.0−4.0, which is the optimized pH for ozone oxidation of GC to generate GCO. As-prepared GCO and MGCO were characterized using X-ray, infrared, and microscopic techniques. The MGCO has enough saturation magnetization (MS) of 41.38 emu g−1 for separation of the sorbent from the reaction medium by applying an external magnetic field. Batch adsorption of radioactive and heavy metals (Th(IV), Pb(II)), and a dye (methylene blue (MB)) using GCO and MGCO was evaluated by varying the adsorbent dose, equilibrium pH, contact time, initial metal and dye concentrations, and kinetics and isotherms. Adsorption kinetics and isotherm studies indicated that Th(IV), Pb(II), and MB adsorption were best described by pseudo-second-order kinetics and Langmuir isotherm with R2 (correlation coefficient) > 0.99, respectively. The maximum adsorption capacities for Th(IV), Pb(II), and MB were 52.63, 47.39, and 111.12 mg g−1 on GCO and 76.02, 71.94, and 76.92 mg g−1 on MGCO. GCO and MGCO are prospectively effective and low-cost adsorbents for ion removal in wastewater treatment. As prepared MGCO can be reused up to three cycles for Th(IV), Pb(II), and MB. This work provides fundamental information about the equilibrium adsorption isotherms and mechanisms for Th(IV), Pb(II), and MB on GCO and MGCO.

Graphene Composites for Lead Ions Removal from Aqueous Solutions

The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other heavy metals, lead (Pb(II)) ions are some of the most toxic pollutants generated from both anthropogenic and natural sources in very large amounts. Adsorption is the simplest, efficient and economic water decontamination technology. Hence, nanoadsorbents are a major focus of current research for the effective and selective removal of Pb(II) metal ions from aqueous solution. Nanoadsorbents based on graphene and its derivatives play a major role in the effective removal of toxic Pb(II) metal ions. This paper summarizes the applicability of graphene and functionalized graphene-based composite materials as Pb(II) ions adsorbent from aqueous solutions. In addition, the synthetic routes, adsorption process, conditions, as well as kinetic studies have been reviewed.

Graphene/nickel oxide nanocomposites against isolated ESBL producing bacteria and A549 cancer cells

The synthesis of nickel oxide nanoparticles (NiO NPs) and graphene/nickel oxide nanocomposites (Gr/NiO NCs) was performed using a simple chemical reduction method. Powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to examine the crystalline nature and thermal stability of the synthesized NiO NPs and Gr/NiO NCs, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to observe the morphology of NiO NPs and Gr/NiO NCs and estimate their size range. TEM suggested that the NiO NPs were speared onto the surface of Gr nanosheet. The efficiency of NiO NPs and Gr/NiO NCs against extended spectrum β-lacamase (ESBL) producing bacteria, which was confirmed by specific HEXA disc Hexa G-minus 24 (HX-096) and MIC strip methods (CLSI); namely Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) was investigated using the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) methods. MIC results suggested that the NiO NPs and Gr/NiO NCs possess maximum growth inhibition of 86%, 82% and 94%, 92% at 50 and 30 μg/mL concentrations, respectively. Similarly, both nanomaterials were found to inhibit the β-lacamase enzyme at concentrations of 60 μg/mL and 40 μg/mL, respectively. The cytotoxicity of NiO NPs and Gr/NiO NCs was quantified against A549 human lung cancer cells. Cell death percentage values of 52% at 50 μg/mL against NiO NPs and 54% at 20 μg/mL against Gr/NiO NCs were obtained, respectively. The NCs were found to reduce cell viability, increase the level of reactive oxygen species (ROS) and modify both the mitochondrial membrane permeability and cell cycle arrest.

Potential utility of graphene-based nano spinel ferrites as adsorbent and photocatalyst for removing organic/inorganic contaminants from aqueous solutions: A mini review

Toxic substances such as heavy metals or persistent organic pollutants raise global environmental concerns. Thus, diverse water decontamination approaches using nano-adsorbents and/or photocatalysts based on nanotechnology are being developed. Particularly, many studies have examined the removal of organic and inorganic contaminants with novel graphene-based nano spinel ferrites (GNSFs) as potential cost-effective alternatives to traditionally used materials, owing to their enhanced physical and chemical properties. The introduction of magnetic spinel ferrites into 2-D graphene-family nanomaterials to form GNSFs brings various benefits such as inhibited particle agglomeration, enhanced active surface area, and easier magnetic separation for reuse, making the GNSFs highly efficient and eco-friendly materials. Here, we present a short review on the state-of-the-art progresses on developments of GNSFs, as well as their potential application for removing several recalcitrant contaminants including organic dyes, antibiotics, and heavy metal ions. Particularly, the mechanisms involved in the adsorptive and photocatalytic degradation are thoroughly reviewed, and the reusability of the GNSFs is also highlighted. This review concludes that the GNSFs hold great potential in remediating contaminated aquatic environments. Further studies are needed for their practical and large-scale applications.

A comprehensive review of applications of magnetic graphene oxide based nanocomposites for sustainable water purification

With the rapid growth of industrialization, water bodies are polluted with heavy metals and toxic pollutants. In pursuit of removal of toxic pollutants from the aqueous environment, researchers have been developed many techniques. Among these techniques, magnetic separation has caught research attention, as this approach has shown excellent performance in the removal of toxic pollutants from aqueous solutions. However, magnetic graphene oxide based nanocomposites (MGO) possess unique physicochemical properties including excellent magnetic characteristics, high specific surface area, surface active sites, high chemical stability, tunable shape and size, and the ease with which they can be modified or functionalized. As results of their multi-functional properties, affordability, and magnetic separation capability, MGO's have been widely used in the removal of heavy metals, radionuclides and organic dyes from the aqueous environment, and are currently attracting much attention. This paper provides insights into preparation strategies and approaches of MGO's utilization for the removal of pollutants for sustainable water purification. It also reviews the preparation of magnetic graphene oxide nanocomposites and primary characterization instruments required for the evaluation of structural, chemical and physical functionalities of synthesized magnetic graphene oxide nanocomposites. Finally, we summarized some research challenges to accelerate the synthesized MGO's as adsorbents for the treatment of water pollutants such as toxic and radioactive metal ions and organic and agricultural pollutants.

Passivating effect of dehydrated sludge and sepiolite on arsenic contaminated soil

Exploring an efficient and economical method to remove arsenic from soil is of great practical significance but there were few studies on the combined use of sepiolite and dehydrated sludge as a repair agent to passivate heavy metals. Through soil passivation experiments, arsenic sequential extractions, and analysis of basic physicochemical properties of contaminated soils and repair agents, this study was to explore the applicability of dehydrated sludge-sepiolite compound repair agents and dehydrated sludge individual repair agents to passivate soil arsenic and its passivating effect. After passivation experiment, the best remediation period was 1-10 days. The best cultivated time was 10 day using DS2 repair agent. With a comparison of passivation effect of different repair agents, it was found that the best treatment group in individual repair agents was DS2 (10 days), and the best treatment group in compound repair agents was S1 (1 day). The passivation effect of individual repair agents was better than compound repair agents in 10-days cultivation. In the short term, the repair effect was increasing and then decreasing, thus this experiment was only suitable for use as a short-term repair method. The application of dehydrated sludge combined with sepiolite as repair agents provided a new way for both making full use of dehydrated sludge and controlling metal mobility.

Removal of Cu2+, Cd2+ and Pb2+ from aqueous solutions by magnetic alginate microsphere based on Fe3O4/MgAl-layered double hydroxide

In this work, the magnetic alginate microsphere of Fe₃O₄/MgAl-LDH (Fe₃O₄/LDH-AM) was prepared by immobilizing the Fe₃O₄/LDH with calcium alginate (CA) and was used to remove Cd²⁺, Pb²⁺, and Cu²⁺ from aqueous solutions. The obtained Fe₃O₄/LDH-AM was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller surface area determination. The results indicated that the surface groups of the alginate and LDH were retained and so was the crystal structure in the alginate microsphere. The adsorption performance of the Fe₃O₄/LDH-AM for Cd²⁺, Pb²⁺, and Cu²⁺ in aqueous solutions was evaluated by batch and column adsorption experiments. The effects of adsorption conditions, kinetics, isotherms, mechanisms, and potential applications were investigated. The adsorption kinetic data conformed to the pseudo-second-order kinetic equation, and the isotherm data fit well with the Freundlich and Langmuir isotherm models. The adsorption mechanism of Cd²⁺, Pb²⁺, and Cu²⁺ by the Fe₃O₄/LDH-AM entailed complexation and precipitation. The experimental breakthrough curves were correlated with the Thomas model. Moreover, the Fe₃O₄/LDH-AM displayed superior regeneration and reusability. These results suggest that the Fe₃O₄/LDH-AM is an efficient adsorbent for the removal of heavy metals and can be effectively employed in practical applications.

Functional manganese ferrite/graphene oxide nanocomposites: effects of graphene oxide on the adsorption mechanisms of organic MB dye and inorganic As(v) ions from aqueous solution

In this study, manganese ferrite-graphene oxide (MFO-GO) nanocomposites were prepared via a co-precipitation reaction of Fe³⁺ and Mn²⁺ ions in a GO suspension. The effects of graphene oxide on the physicochemical characteristics, magnetic properties and adsorption activities of the MFO-GO nanocomposites were studied. Methylene blue (MB) and arsenic(v) were used in this study as model water pollutants. With an increase in the GO content in the range of 10 wt% to 50 wt%, the removal efficiency for both MB dye and arsenic(v) ions was improved. Our adsorption data revealed that the adsorption behavior of MB dye showed good agreement with the Langmuir isotherm model and pseudo-second-order equation, whereas the Freundlich isotherm model was more suitable for simulating the adsorption process of arsenic(v) ions on the MFO-GO nanocomposites. In addition, an important role of the GO content in the adsorption mechanisms of both MB dye and arsenic(v) ions was found, in which GO nanosheets play a key role in the mechanisms of electrostatic/ionic interactions, oxygen-containing groups and π–π conjugation in the case of the adsorption of MB dye, whereas the role of the GO content is mainly related to the mechanism of electrostatic/ionic interactions in the case of the adsorption of arsenic(v). Graphene oxide has the functions of increasing the number of active binding sites comprising oxygen-containing functional groups, reducing the agglomeration of MFO nanoparticles, increasing the number of adsorption sites, and improving the electrostatic/ionic interactions between adsorbents and adsorbates in order to enhance the adsorption performance of cationic organic dyes and/or heavy metal anions from aqueous solutions.

In this study, manganese ferrite-graphene oxide (MFO-GO) nanocomposites were prepared via a co-precipitation reaction of Fe³⁺ and Mn²⁺ ions in a GO suspension.

Preparation of nanoscale iron (oxide, oxyhydroxides and zero-valent) particles derived from blueberries: Reactivity, characterization and removal mechanism of arsenate

The application of iron nanoparticles (FeNPs) to the removal of various pollutants has received wide attention over the last few decades. A synthesis alternative to obtain these nanoparticles without using harmful chemical reagents, such as NaBH₄, is the use of extracts from different natural sources that allow a lesser degree of agglomeration, in a process known as green synthesis. In this study, FeNPs were synthesized by 'green' (hereafter, BB-Fe NPs) and 'chemical' (hereafter, nZVI) methods. Extracts of leaves and blueberry shoots (Vaccinium corymbosum) were used as reducing agents for FeCl₃·6H₂O solution in the green synthesis method. FeNPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrophoretic migration, Brunauer-Emmett-Teller (BET) surface area analysis and X-ray diffraction (XRD) and evaluated for the removal of As(V) from aqueous systems. In both synthesis methods, XRD analysis confirmed the presence of the different kinds of iron nanoparticles. SEM analysis showed that the average size of BB-Fe NPs was 52.4nm and that a variety of nanoparticles of different forms and associated structures, such as lepidocrocite, magnetite, and nZVI, were present, while the dimensions of nZVI were 80.2nm. Comparatively significant differences regarding the electrophoretic mobility were found between both materials pre- and post-sorption of As(V). The velocity of As(V) removal by BB-Fe NPs was slower than that by nZVI, reaching equilibrium at 120min compared to 60min for nZVI. The removal kinetics of As(V) were adequately described by the pseudo-second-order kinetic model, and the maximum adsorbed amounts of this analyte are in close accordance with the experimental results. The Langmuir-Freundlich model is in good agreement with our experimental data, where the sorption capacity of nZVI and BB-Fe NPs was found to be 52.23 ± 6.06 and 50.40 ± 5.90 (mg·g^-1), respectively. The use of leaves of Vaccinium corymbosum affords an easy-to-synthesize, low-cost, and eco-friendly material with capabilities similar to nZVI. BB-Fe NPs are promising for arsenic remediation, which has emerged as a new alternative for water purification and sanitation.