A novel electrospun PVA/ZnO nanofiber adsorbent for U(VI), Cu(II) and Ni(II) removal from aqueous solution

Functionalization of a cast NaAl/binary ZnO/SiO2 nanohybrid with amine and Schiff base ligands as an adsorbent of divalent cations in water system

Casting method was used to synthesize a novel sodium alginate nanohybrid functionalized with aminated ZnO/SiO2 Schiff base for adsorption of nickel (Ni2+) and copper (Cu2+) divalent cations in single and binary water systems. The cast Schiff base nanohybrids were investigated using FESEM, XRD, BET, FTIR, TGA, and XPS analyses. The influence of unfunctionalized binary ZnO/SiO2 nano oxides and aminated Schiff base ligands formed by the reaction between salicylaldehyde and O-phenylenediamine on the adsorption of Ni2+ and Cu2+ cations was evaluated. The results confirmed that the aminated Schiff base ligands led to a higher adsorption ability of the cast nanohybrids containing interaction of divalent cations with nitrogen and oxygen atoms, as well as carboxyl and hydroxyl groups. The adsorption kinetics and isotherm for both cations followed a double-exponential model and the Redlich-Peterson model, respectively. The maximum monolayer capacity was found to be 249.8 mg/g for Cu2+ cation and 96.4 mg/g for Ni2+ cation. Thermodynamic analysis revealed an endothermic and spontaneous adsorption process with an increase in entropy. Furthermore, the synthesized Schiff base adsorbent could be easily reused over five times. The simultaneous adsorption in binary system exhibited a higher adsorption selectivity of the cast Schiff base nanohybrid for Cu2+ cation compared to Ni2+ cation. It was found that the removal percentages of Cu2+ and Ni2+ from industrial electroplating wastewater were 91.3 and 64.5%, respectively. Lastly, cost analysis of the synthesized nanohybrid was investigated.

A review on hybrid membrane-adsorption systems for intensified water and wastewater treatment: Process configurations, separation targets, and materials applied

In the era of rapid and conspicuous progress of water treatment technologies, combined adsorption and membrane filtration systems have gained great attention as a novel and efficient method for contaminant removal from aqueous phase. Further development of these techniques for water/wastewater treatment applications will be promising for the recovery of water resources as well as reducing the water tension throughout the world. This review introduces the state-of-the-art on the capabilities of the combined adsorption-membrane filtration systems for water and wastewater treatment applications. Technical information including employed materials, superiorities, operational limitations, process sustainability and upgradeing strategies for two general configurations i.e. hybrid (pre-adsorption and post-adsorption) and integrated (film adsorbents, low pressure membrane-adsorption coupling and membrane-adsorption bioreactors) systems has been surveyed and presented. Having a systematic look at the fundamentals of hybridization/integration of the two well-established and efficient separation methods as well as spotlighting the current status and prospectives of the combination strategies, this work will be valuable to all the interested researchers working on design and development of cutting-edge wastewater/water treatment techniques. This review also draws a clear roadmap for either decision making and choosing the best alternative for a specific target in water treatment or making a plan for further enhancement and scale-up of an available strategy.

Modified Silica Nanoparticles from Rice Husk Supported on Polylactic Acid as Adsorptive Membranes for Dye Removal

Industrial effluents and wastewater treatment have been a mainstay of environmental preservation and remediation for the last decade. Silica nanoparticles (SiO₂) obtained from rice husk (RH) are an alternative to producing low-cost adsorbent and agriculture waste recovery. One adsorption challenge is facilitating the adsorbate separation and reuse cycle from aqueous medium. Thus, the present work employs SiO₂ supported on polylactic acid (PLA) nanofibers obtained by the electrospinning method for Rhodamine B (RhB) dye adsorption. The silica surface was modified with trimethylsilyl chloride (TMCS) to increase affinity towards organic compounds. As a result, the silanized surface of the silica from rice husk (RHSil) promoted an increase in dye adsorption attributed to the hydrophobic properties. The PLA fibers containing 40% SiO₂ (w w^-1) showed about 85-95% capacity adsorption. The pseudo-first-order kinetic model was demonstrated to be the best model for PLA:SiO₂ RHSil nanocomposites, exhibiting a 1.2956 mg g^-1 adsorption capacity and 0.01404 min^-1 kinetic constant (k₁) value. In the reuse assay, PLA:SiO₂ membranes preserved their adsorption activity after three consecutive adsorption cycles, with a value superior to 60%. Therefore, PLA:SiO₂ nanocomposites from agricultural waste are an alternative to "low-cost/low-end" treatments and can be used in traditional treatment systems to improve dye removal from contaminated waters.

Recent progress on electrospun nanofibrous polymer membranes for water and air purification: A review

Developing new polymer membranes with excellent thermal, mechanical, and chemical stability has shown great potential for various environmental remediation applications such as wastewater treatment and air filtration. Polymer membranes have been widely investigated over the past years and utilized to overcome severe ecological issues. Membrane-based technologies play a critical role in water purification and air filtration with the ability to act efficiently and sustainably. Electrospun nanofiber membranes have displayed excellent performance in removing various contaminants from water, such as bacteria, dyes, heavy metals, and oil. These nanofibrous membranes have shown good potential to filter the air from tiny particles, volatile organic compounds, and toxic gases. The performance of polymer membranes can be enhanced by fine-tuning polymer structure, varying surface properties, and strengthening overall membrane porosity. In this review, we discuss the involvement of electrospun nanofibrous membranes in different environmental remediation applications. It further reviews the recent progress of polymer membrane development by utilizing nanoparticles and naturally occurring polymers.

Superhydrophobic and highly moisture-resistant PVA@EC composite membrane for air purification

Electrospun fiber membranes have great potential in the field of air filtration because of their high porosity and small pore size. Conventional air filtration membranes are hydrophilic, leading to weak moisture-barrier properties, which hinders their application in high-humidity environments. In this study, eugenol was added to polyvinyl alcohol and ethyl cellulose (EC) for electrospinning and electrospraying, respectively, of superhydrophobic bilayer composite fiber membranes to efficiently filter particulate matter (PM) in air. Owing to its surface microstructure, electrosprayed EC increased the water contact angle of the PVA membrane from 142.8 to 151.1°. More importantly, the composite air-filter membrane showed a low filtration pressure drop (168.1 Pa) and exhibited high filtration efficiencies of 99.74 and 99.77% for PM1.0 and PM2.5, respectively, and their respective quality factors were 0.0351 and 0.0358 Pa-1. At the same time, the filtration performance of the air filtration membrane remained above 99% at high air humidity. This work reports composite membranes that can effectively capture PM of various sizes and thus may provide a reference for the manufacturing of green air filters for high-humidity environments.

A critical and recent developments on adsorption technique for removal of heavy metals from wastewater-A review

This review provides a quantitative description of the nano-adsorbent processing and its viability against wastewater detoxification by extracting heavy metal ions. The impact of nano-adsorbent functionalities on specific essential attributes such as the surface area, segregation, and adsorption capacity were comprehensively evaluated. A detailed analysis has been presented on the characteristics of nanomaterials through their limited resistance to adsorb some heavy metal ions. Experimental variables such as the adsorbent dosage, pH, substrate concentration, response duration, temperature, and electrostatic force that influence the uptake of metal ions have been studied. Besides, separate models for the adsorption kinetics and isothermal adsorption have been investigated to understand the mechanism behind adsorption. Here, we reviewed the different adsorbent materials with nano-based techniques for the removal of heavy metals from wastewater and especially highlighted the nano adsorption technique. The influencing factors such as pH, temperature, dosage time, sorbent dosage, adsorption capacities, ion concentration, and mechanisms related to the removal of heavy metals by nano composites are highlighted. Lastly, the application potentials and challenges of nano adsorption for environmental remediation are discussed. This critical review would benefit engineers, chemists, and environmental scientists involved in the utilization of nanomaterials for wastewater treatment.

A comprehensive review on preparation, functionalization and recent applications of nanofiber membranes in wastewater treatment

The direct discharge of significant amounts of polluted water into water bodies causes adverse ecological and human health effects. This severe deterioration in water quality creates significant challenges to meet the growing demand for clean water. Therefore, the world urgently needs environmentally friendly advanced technology to overcome this global crisis. In this regard, nanofiber-based membrane filtration is a promising technique in wastewater remediation because of their huge surface area, extremely porous structure, amenable pore size/pore size distribution, variety of material choices, and flexibility to modification with other functional materials. However, despite their unique properties, fouling, poor mechanical properties, shrinkage, and deformation are major drawbacks of nanofiber membranes for treating wastewater. This review presents a comprehensive overview of nanofiber membranes' fabrication and function in water purification applications as well as providing novel approaches to overcoming/alleviating the mentioned disadvantages. The review first presents nanofiber membrane preparation methods, focusing on electrospinning as a versatile and viable technique alongside discussing the parameters controlling nanofiber morphology. Afterward, the functionalization of nanofiber membranes by combining them with other nanomaterials, such as metal and metal-oxide nanoparticles, carbon nanotubes, metal-organic frameworks, and biomolecules, were demonstrated and discussed. In addition, nanofiber membranes functionalized with microorganisms were highlighted. Finally, we introduced and discussed in detail the most relevant and recent advances in nanofiber applications in wastewater treatment in the context of removing different pollutants (e.g., heavy metals, nutrients, radioactive elements, pharmaceuticals, and personal care products, dyes, and pesticides). Moreover, the promising antimicrobial ability of nanofiber membranes in removing microorganisms from wastewater has been fully underscored. We believe this comprehensive review could provide researchers with preliminary data and guide both researchers and producers engaged in the nanofiber membrane industry, letting them focus on the research gaps in wastewater treatment.

A critical review on various remediation approaches for heavy metal contaminants removal from contaminated soils

Heavy metal pollution remains a global environmental challenge that poses a significant threat to human life. Various methods have been explored to eliminate heavy metal pollutants from the environment. However, most methods are constrained by high expenses, processing duration, geological problems, and political issues. The immobilization of metals, phytoextraction, and biological methods have proven practical in treating metal contaminants from the soil. This review focuses on the general status of heavy metal contamination of soils, including the excessive heavy metal concentrations in crops. The assessment of the recent advanced technologies and future challenges were reviewed. Molecular and genetic mechanisms that allow microbes and plants to collect and tolerate heavy metals were elaborated. Tremendous efforts to remediate contaminated soils have generated several challenges, including the need for remediation methodologies, degrees of soil contamination, site conditions, widespread adoptions and various possibilities occurring at different stages of remediation are discussed in detail.

Heavy metal removal by biomass-derived carbon nanotubes as a greener environmental remediation: A comprehensive review

The concentrations of heavy metal ions found in waterways near industrial zones are often exceed the prescribed limits, posing a continued danger to the environment and public health. Therefore, greater attention has been devoted into finding the efficient solutions for adsorbing heavy metal ions. This review paper focuses on the synthesis of carbon nanotubes (CNTs) from biomass and their application in the removal of heavy metals from aqueous solutions. Techniques to produce CNTs, benefits of modification with various functional groups to enhance sorption uptake, effects of operating parameters, and adsorption mechanisms are reviewed. Adsorption occurs via physical adsorption, electrostatic interaction, surface complexation, and interaction between functional groups and heavy metal ions. Moreover, factors such as pH level, CNTs dosage, duration, temperature, ionic strength, and surface property of adsorbents have been identified as the common factors influencing the adsorption of heavy metals. The oxygenated functional groups initially present on the surface of the modified CNTs are responsible towards the adsorption enhancement of commonly-encountered heavy metals such as Pb²⁺, Cu²⁺, Cd²⁺, Co²⁺, Zn²⁺, Ni²⁺, Hg²⁺, and Cr⁶⁺. Despite the recent advances in the application of CNTs in environmental clean-up and pollution treatment have been demonstrated, major obstacles of CNTs such as high synthesis cost, the agglomeration in the post-treated solutions and the secondary pollution from chemicals in the surface modification, should be critically addressed in the future studies for successful large-scale applications of CNTs.

The efficiency of nano-TiO2 and γ-Al2O3 in copper removal from aqueous solution by characterization and adsorption study

Water pollution is a major global challenge given the increasing growth in the industry and the human population. The present study aims to investigate the efficiency of TiO2 and γ-Al2O3 nanoadsorbents for removal of copper (Cu(II)) from aqueous solution as influenced by different chemical factors including pH, initial concentration, background electrolyte and, ionic strength. The batch adsorption experiment was performed according to standard experimental methods. Various isotherm models (Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich) were fitted to the equilibrium data. According to geochemical modeling data, adsorption was a predominant mechanism for Cu(II) removal from aqueous solution. Calculated isotherm equations parameters were evidence of the physical adsorption mechanism of Cu(II) onto the surface of the nanoparticles. The Freundlich adsorption isotherm model could well fit the experimental equilibrium data at different pH values. The maximum monolayer adsorption capacity of TiO2 and γ-Al2O3 nanosorbents were found to 9288 and 3607 mg kg-1 at the highest pH value (pH 8) and the highest initial Cu(II) concentration (80 mg L-1) respectively. Copper )Cu(II) (removal efficiency with TiO2 and γ-Al2O3 nanoparticles increased by increasing pH. Copper )Cu(II) (adsorption deceased by increasing ionic strength. The maximum Cu(II) adsorption (4510 mg kg-1) with TiO2 nanoparticles was found at 0.01 M ionic strength in the presence of NaCl. Thermodynamic calculations show the adsorption of Cu(II) ions onto the nanoparticles was spontaneous in nature. Titanium oxide (TiO2) nanosorbents could, therefore, serve as an efficient and low-cost nanomaterial for the remediation of Cu(II) ions polluted aqueous solutions.

A review of recent progress in polymeric electrospun nanofiber membranes in addressing safe water global issues

With rapid advancement in water filtration materials, several efforts have been made to fabricate electrospun nanofiber membranes (ENMs). ENMs play a crucial role in different areas of water treatment due to their several advantageous properties such as high specific surface area, high interconnected porosity, controllable thickness, mechanical robustness, and wettability. In the broad field of water purification, ENMs have shown tremendous potential in terms of permeability, rejection, energy efficiency, resistance to fouling, reusability and mechanical robustness as compared to the traditional phase inversion membranes. Upon various chemical and physical modifications of ENMs, they have exhibited great potential for emerging applications in environment, energy and health sectors. This review firstly presents an overview of the limiting factors influencing the morphology of electrospun nanofibers. Secondly, it presents recent advancements in electrospinning processes, which helps to not only overcome drawbacks associated with the conventional electrospinning but also to produce nanofibers of different morphology and orientation with an increased rate of production. Thirdly, it presents a brief discussion about the recent progress of the ENMs for removal of various pollutants from aqueous system through major areas of membrane separation. Finally, this review concludes with the challenges and future directions in this vast and fast growing area.

A critical review on the electrospun nanofibrous membranes for the adsorption of heavy metals in water treatment

Electrospun nanofibrous membranes (ENFMs) have many superior advantages, such as large specific surface area, high porosity, easy modification, good flexibility, and easy separation for recycling, which are consider as excellent adsorbents. In this paper, the research progress in the adsorption of heavy metals in water treatment by ENFMs is reviewed. Three types of ENFMs, including organic polymer ENFMs, organic polymer/inorganic material composite ENFMs and inorganic ENFMs are summarized, and their adsorption capacities for heavy metals in water are compared. The adsorption selectivity and capacity of ENFMs for heavy metals are depended largely on the type and number of functional groups on the surface of membranes, and usually the more the functional groups, the higher the adsorption capacity. The adsorption mechanisms of ENFMs are also mainly determined by the type of functional groups on the membrane. At present, the main challenge is to achieve the mass production of high-quality nanofibers and their actual application in the treatment of heavy metal-containing wastewater. Therefore, more consideration should be focused on the improvement of stability, mechanical strength and reusability of ENFMs. This review may provide an insight for the development of ENFMs-based adsorbents for heavy metals separation and water purification in the future.

Effects of Ultrasonication Time on the Properties of Polyvinyl Alcohol/Sodium Carboxymethyl Cellulose/Nano-ZnO/Multilayer Graphene Nanoplatelet Composite Films

Ultrasonication-assisted solution casting was used to prepare polyvinyl alcohol (PVA)/sodium carboxymethyl cellulose (CMC)/nano-ZnO/multilayer graphene nanoplatelet (xGnP) composite films; the performances (mechanical properties, water vapor permeability (WVP), biodegradability and antibacterial activity) of these films were investigated as a function of the ZnO NPs:xGnP mass ratio and ultrasonication time. Intermolecular interactions among ZnO NPs, xGnP and the PVA/CMC matrix were shown to improve WVP, while X-ray diffraction and scanning electron microscopy analyses revealed that the internal reticular structure of ultrasound-treated PVA/CMC/ZnO NPs/xGnP composite films was in a fluffier state than that of the untreated composite films and the PVA/CMC film. The incorporation of ZnO NPs and xGnP into the composite film reduced its tensile strength and elongation at break, and increased antibacterial activity and biodegradability. In addition, we carried out the experiment of strawberry preservation and measured weight loss ratio, firmness, content of total soluble solids and titration acid. Finally, the composite film of 7:3 had the best preservation effect on strawberries. Thus, the obtained results paved the way to develop novel biodegradable composite films with antimicrobial activity for a wide range of applications.

Effective Heavy Metals Removal from Water Using Nanomaterials: A Review

The discharge of toxic heavy metals including zinc (Zn), nickel (Ni), lead (Pb), copper (Cu), chromium (Cr), and cadmium (Cd) in water above the permissible limits causes high threat to the surrounding environment. Because of their toxicity, heavy metals greatly affect the human health and the environment. Recently, better remediation techniques were offered using the nanotechnology and nanomaterials. The attentions were directed toward cost-effective and new fabricated nanomaterials for the application in water/wastewater remediation, such as zeolite, carbonaceous, polymer based, chitosan, ferrite, magnetic, metal oxide, bimetallic, metallic, etc. This review focused on the synthesis and capacity of various nanoadsorbent materials for the elimination of different toxic ions, with discussion of the effect of their functionalization on the adsorption capacity and separation process. Additionally, the effect of various experimental physicochemical factors on heavy metals adsorption, such as ionic strength, initial ion concentration, temperature, contact time, adsorbent dose, and pH was discussed.

Removal of U(VI) from aqueous and polluted water solutions using magnetic Arachis hypogaea leaves powder impregnated into chitosan macromolecule

In this study m-AHLPICS (magnetic Arachis hypogaea leaves powder impregnated into chitosan) was prepared and utilized as an adsorbent to remove U(VI) from aqueous and real polluted wastewater samples. m-AHLPICS was characterized by using the BET, XRD, FTIR, SEM with elemental mapping and magnetization measurements. Different experimental effects such as pH, dose, contact time, and temperature were considered broadly. Chitosan modified magnetic leaf powder (m-AHLPICS) exhibits an excellent adsorption capacity (232.4 ± 5.59 mg/g) towards U(VI) ions at pH 5. Different kinetic models such as pseudo-first-order, and pseudo-second-order models were used to know the kinetic data. Langmuir, Freundlich and D-R isotherms were implemented to know the adsorption behavior. Isothermal information fitted well with Langmuir isotherm. Kinetic data followed by the pseudo-second-order kinetics (with high R² values, i.e., 0.9954, 0.9985 and 0.9971) and the thermodynamic data demonstrate that U(VI) removal using m-AHLPICS was feasible, and endothermic in nature.

Electrospinning of polyvinyl alcohol into crosslinked nanofibers: An approach to fabricate functional adsorbent for heavy metals

Electrospun nanofibers have a wide range of applications due to their unique miniature size and accompanying ultra-high specific surface area. Polyvinyl alcohol(PVA) is a kind of hydrophilic materials, and hence its nanofiber morphology prepared by electrospinning disappeared after solution immersing. In the present work, crosslinked PVA nanofibers were prepared by electrospinning and then employing glutaraldehyde vapor crosslinking to improve their water resistance and mechanical properties. As an application, these nanofibers were used to adsorb Cu²⁺ and Pb²⁺ according to varying crosslinking time and different concentrations of ionic solution. It was observed the crosslinked PVA nanofiber films maintained good fiber morphology after adsorption, while the nanofiber morphology of uncrosslinked samples was lost. The stability of the crosslinked nanofiber films in water was improved, the adsorption equilibrium time of Pb²⁺ decreased from 30 h to 10 h while the equilibrium adsorption time of Cu²⁺ decreased from 15 h to 5 h, and the tensile strength of the nanofiber films with crosslinking time of 20 h was 7.99 MPa, which was 240% higher than that of the nanofiber with crosslinking time of 1 h, indicating higher efficiency.

Adsorption performance and mechanisms of Pb(II), Cd(II), and Mn(II) removal by a β-cyclodextrin derivative

In this study, the novel adsorbent PVA-TA-βCD was synthesized via thermal cross-linking between polyvinyl alcohol and β-cyclodextrin. The characterization methods SEM-EDS, FTIR, and XPS were adopted to characterize the adsorbent. The effect of pH, contact time, initial concentrations, and temperature during the adsorption of Pb(II), Cd(II), and Mn(II) onto the PVA-TA-βCD was also investigated. In a single-component system, the data fitted well to pseudo-second-order, and film diffusion and intra-particle diffusion both played important roles in the adsorption process. As for isotherm study, it showed a heterogeneous adsorption capacity of 199.11, 116.52, and 90.28 mg g^-1 for the Pb(II), Cd(II), and Mn(II), respectively. Competition between the ions existed in a multi-component system; however, owing to the stronger affinity of the PVA-TA-βCD for Pb(II) relative to Cd(II) and Mn(II), the Pb(II) adsorption onto the PVA-TA-βCD was less affected by the addition of the other metals, which could be effectively explained by the hard and soft acid and base theory (HSAB). Furthermore, PVA-TA-βCD showed good reusability throughout regeneration experiments.

Performance of ceria/iron oxide nano-composites based on chitosan as an effective adsorbent for removal of Cr(VI) and Co(II) ions from aqueous systems

A novel chitosan/ceria/iron oxide (CS/ceria/Fe₃O₄) nano-composite adsorbent was synthesized for removal of Cr(VI) and Co(II) ions from aqueous systems in a batch system. The adsorbents were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and Brunauer- Emmett-Teller (BET) analyses. The behavior of swelling kinetics was also studied. The effect of several adsorption parameters including CeO₂ and Fe₃O₄ contents, initial pH, contact time, initial Cr(VI) and Co(II) concentration, and temperature on the adsorption capacity was studied. The double exponential model revealed a better fit with the kinetic data of Cr(VI) and Co(II) ions. The Cr(VI) and Co(II) adsorption process well fitted the Langmuir model. The maximum adsorption capacities estimated from Langmuir isotherm model were 315.4 and 260.6 mg/g for Cr(VI) and Co(II) ions, respectively. Also, thermodynamic parameters were used to distinguish the nature of Cr(VI) and Co(II) adsorption. The reusability of CS/ceria/Fe₃O₄ nano-composite was evaluated with stripping agents of 0.1 M NaOH and 0.1 M HNO₃. Finally, the evaluation of Cr(VI)-Co(II) coexisting system confirmed that the presence of Co(II) ions played an inhibitor role on the Cr(VI) adsorption.

Photocatalytic degradation of naphthalene using calcined FeZnO/ PVA nanofibers

Recently, the incorporation of metal oxide nanoparticles into polymers has gained great attention owing to their ample of applications. The green mediated synthesis Fe-doped ZnO nanoparticles have been incorporated into PVA nanofibers through electro spinning for the application of photocatalytic degradation. The PVA polymer concentration was optimized to obtain uniform fibers without beads. The Fe-doped ZnO nanofibers were characterized by various analyzing techniques. The results show that good physicochemical with high surface area, uniformity in fiber with an average diameter ranges from 150 to 300 and 50-200 nm for un-calcined and calcined Fe-doped ZnO nanofiber respectively. The photocatalytic activity of nanofibers was examined by the degradation of naphthalene. The efficiency was observed 96 and 81% for calcined and un-calcined nanofibers, respectively. The reusable efficacy of Fe-doped ZnO calcined nanofiber as a catalyst was studied. These studies corroborated that the calcined Fe-doped ZnO nanofiber as promising material for catalytic applications.

Performance of synthesized cast and electrospun PVA/chitosan/ZnO-NH2 nano-adsorbents in single and simultaneous adsorption of cadmium and nickel ions from wastewater

The performance of synthesized cast and electrospun polyvinyl alcohol/chitosan/zinc oxide/aminopropyltriethoxylsilane (PVA/chitosan/ZnO-APTES) nano-adsorbents were compared in removal of Cd(II) and Ni(II) ions from wastewater. The adsorbents were characterized by SEM, BET, FTIR and TGA analyses. Furthermore, the swelling investigations were carried out to study the adsorbent stability in aqueous solution. The effect of several parameters such as contents of ZnO-NH₂, contact time, initial Cd(II) and Ni(II) concentration and temperature on the adsorption capacity was investigated in a batch mode. In comparison with cast adsorbent, nanofiber adsorbent indicated the better adsorption performance. The experimental data well fitted the double-exponential kinetic model. In single metal ion system, the maximum adsorption capacity of nanofiber for Cd(II) and Ni(II) ions is estimated to be 1.239 and 0.851 mmol/g, respectively, much higher than q_m of cast adsorbent for Cd(II) (0.625 mmol/g) and Ni(II) (0.474 mmol/g) ions. Thermodynamic parameters were investigated to identify the nature of adsorption process. In binary system of Cd(II)-Ni(II) ions, the inhibitory effect of competitive Cd(II) ion on the Ni(II) adsorption was greater than the inhibitory effect of competitive on the Cd(II) adsorption. The selectivity adsorption of both nanofiber and cast adsorbents was in order of Cd(II) > Ni(II).

Superior adsorption of 3D nanoporous architectures for Ni(ii) ions adsorption using polyvinyl alcohol as cross-linking agent and adsorption conveyor

In this study, we report a large-scale and low cost approach for the synthesis of three-dimensional (3D) polyvinyl alcohol/carbon nanotubes nanoporous architecture using self-assembly method. Polyvinyl alcohol, serving as a cross-linking agent and adsorption conveyor, could effectively interconnect carbon nanotubes sequentially and also effectively store Ni(ii) ions. An outstanding adsorption of 225.6 mg g⁻¹ was achieved for 3D nanoporous structure, which was 18-fold more than that for carbon nanotube powders and much higher than that for other sorbents reported in literature. In addition, it was found that 3D nanoporous architectures remained intact after adsorption, which could recollect resources and avoid carbon nanotube leakage into water. Therefore, the designed 3D nanoporous architectures have a good potential application in environmental protection.

In this study, we report a large-scale and low cost approach for the synthesis of three-dimensional (3D) polyvinyl alcohol/carbon nanotubes nanoporous architecture using self-assembly method.

Mesoporous MgO/PPG hybrid nanofibers: synthesis, optimization, characterization and heavy metal removal property

In this research, mesoporous magnesium oxide/poly(propylene glycol) (MgO/PPG) hybrid nanofibers were synthesized as a new adsorbent for the removal of heavy metal ions from solutions.

Synthesis of the modified nanofiber as a nanoadsorbent and its dye removal ability from water: isotherm, kinetic and thermodynamic

In this paper, poly(vinyl alcohol) (PVA) nanofiber was prepared and modified by diethylenetriamine (DETA) and ethylenediamine (EDA) in the presence of glutaraldehyde (GA). Dye removal ability of the modified nanofiber (PVA/DETA/EDA/GA) as a nanoadsorbent from water was studied. Fourier transform Infrared (FTIR) and scanning electron microscopy (SEM) were used to investigate the characteristics of the modified nanofiber. Direct Red 23 (DR23) and Direct Blue (DB78) were used. The effect of operational parameters such as pH, initial dye concentration, contact time, temperature and adsorbent dosage on dye removal was studied. The dye adsorption isotherms, kinetics and thermodynamics were investigated. The maximum dye adsorption capacity of the modified nanofiber was 370 and 400 mg/g for DR23 and DB78, respectively. Four isotherms, the Langmuir, the Freundlich, Tempkin and a modified Langmuir-Freundlich model were used. Dye adsorption on the modified nanofiber followed the Langmuir isotherm and pseudo-second kinetic order. Thermodynamic data showed that dye removal was a spontaneous, endothermic and physisorption process.