Highly Flexible and Porous Nanoparticle-Loaded Films for Dye Removal by Graphene Oxide-Fungus Interaction

A novel mycelial pellet applied to remove polycyclic aromatic hydrocarbons: High adsorption performance & its mechanisms

Mycelial pellets formed by Penicillium thomii ZJJ were applied as efficient biosorbents for the removal of polycyclic aromatic hydrocarbons (PAHs), which are a type of ubiquitous harmful hydrophobic pollutants. The live mycelial pellets were able to remove 93.48 % of pyrene at a concentration of 100 mg/L within 48 h, demonstrating a maximum adsorption capacity of 285.63 mg/g. Meanwhile, the heat-killed one also achieved a removal rate of 65.01 %. Among the six typical PAHs (pyrene, phenanthrene, fluorene, anthracene, fluoranthene, benzo[a]pyrene), the mycelial pellets preferentially adsorbed the high molecular weight PAHs, which also have higher toxicity, resulting in higher removal efficiency. The experimental results showed that the biosorption of mycelial pellets was mainly a spontaneous physical adsorption process that occurred as a monolayer on a homogeneous surface, with mass transfer being the key rate-limiting step. The main adsorption sites on the surface of mycelia were carboxyl and N-containing groups. Extracellular polymeric substances (EPS) produced by mycelial pellets could enhance adsorption, and its coupling with dead mycelia could achieve basically the same removal effect to that of living one. It can be concluded that biosorption by mycelial pellets occurred due to the influence of electrostatic and hydrophobic interactions, consisting of five steps. Furthermore, the potential applicability of mycelial pellets has been investigated considering diverse factors. The mycelia showed high environmental tolerance, which could effectively remove pyrene across a wide range of pH and salt concentration. And pellets diameters and humic acid concentration had a significant effect on microbial adsorption effect. Based on a cost-effectiveness analysis, mycelium pellets were found to be a low-cost adsorbent. The research outcomes facilitate a thorough comprehension of the adsorption process of pyrene by mycelial pellets and their relevant applications, proposing a cost-effective method without potential environmental issues (heat-killed mycelial pellets plus EPS) to removal PAHs.

Graphene oxide enabled self-assembly of silver trimolybdate nanowires into robust membranes for nanosolid capture and molecular separation

A graphene oxide (GO) assisted self-assembly strategy for growing a silver trimolybdate nanowire membrane with capabilities of nanosolid capture and small molecule separation is reported. Thanks to the GO bridges and the accurate self-assembly process, the resulting membrane exhibits outstanding mechanical properties (can withstand 4300 times its weight) and impressively high porosity (97%). On the basis of the robustness and high porosity of the membrane, column-shaped filter apparatus has been fabricated, in which the membrane served as a self-standing permeation barrier to assess its permeability and practical application as a nanosolid filter and molecule filter. The permeability test of the membrane with pure water uncovers that the membrane exhibits fast permeability while driven by hydrostatic pressure only because of its significantly high porosity. The separation test of the membrane with P25 TiO₂ solution, 13 nm Au solution, and yellow-emitting CdTe QDs reveals that all the tiny nanosolids are completely removed from the solution, which suggests that the membrane is an efficient nanosolid filter. Its efficiency is increased by the induction of surface collision from numerous nanowire barriers and the deposition of nanosolids on the nanowire surface. The separation test of the membrane with a mixed-dye solution reveals that sulfur containing methylene blue (MB) molecules are highly efficiently extracted under various chemical conditions, evidencing that the membrane is an ideal molecule filter too. Its high selectivity and high efficiency originated from the Ag-S bonding between the interlayered silver ions of the silver trimolybdate nanowire and the sulfur atom of MB molecules. Based on the above results, the silver trimolybdate nanowire membrane has been applied to purify drugs, which successfully removed sulbactam sodium impurity F from sulbactam sodium, demonstrating a purity increment from 98.92% to 99.93%. The present work should provide a significant step forward to bringing macroscopic 1D nanomaterial architectures much closer to real-world applications involving isolation and enrichment of catalyst reclamation, high-value chemical recovery, drug purification, and environmental remediation.

Preparation of Three-Dimensional MF/Ti3C2Tx/PmPD by Interfacial Polymerization for Efficient Hexavalent Chromium Removal

Heavy metal pollution is a serious threat to human health and the ecological environment, but adsorption technology based on nano adsorbents can effectively treat the crisis. However, due to the nanoscale effect, nano adsorbents have some crucial shortcomings, such as recycling difficulty and the loss of nanoparticles, which seriously limit their application. The feasible assembly of nano adsorbents is an accessible technology in urgent need of a breakthrough. In this study, three-dimensional (3D) adsorbent (MF/Ti3C2Tx/PmPD) with excellent performance and favorable recyclability was prepared by interfacial polymerization with melamine foam (MF) as the framework, two-dimensional (2D) titanium carbide (Ti3C2Tx) as the bridge and Poly (m-Phenylenediamine) (PmPD) as the active nano component. The morphology, structure, mechanical property of MF/Ti3C2Tx/PmPD and reference MF/PmPD were investigated through a scanning electron microscope (SEM), Fourier transformed infrared spectra (FT-IR), Raman scattering spectra and a pressure-stress test, respectively. Owning to the regulation of Ti3C2Tx on the morphology and structure of PmPD, MF/Ti3C2Tx/PmPD showed excellent adsorption capacity (352.15 mg/g) and favorable cycling performance. R-P and pseudo-second-order kinetics models could well describe the adsorption phenomenon, indicating that the adsorption process involved a composite process of single-layer and multi-layer adsorption and was dominated by chemical adsorption. In this research, the preparation mechanism of MF/Ti3C2Tx/PmPD and the adsorption process of Cr(VI) were systematically investigated, which provided a feasible approach for the feasible assembly and application of nano adsorbents in the environmental field.

Application of Functionalized Graphene Oxide Based Biosensors for Health Monitoring: Simple Graphene Derivatives to 3D Printed Platforms

Biosensors hold great potential for revolutionizing personalized medicine and environmental monitoring. Their construction is the key factor which depends on either manufacturing techniques or robust sensing materials to improve efficacy of the device. Functional graphene is an attractive choice for transducing material due to its various advantages in interfacing with biorecognition elements. Graphene and its derivatives such as graphene oxide (GO) are thus being used extensively for biosensors for monitoring of diseases. In addition, graphene can be patterned to a variety of structures and is incorporated into biosensor devices such as microfluidic devices and electrochemical and plasmonic sensors. Among biosensing materials, GO is gaining much attention due to its easy synthesis process and patternable features, high functionality, and high electron transfer properties with a large surface area leading to sensitive point-of-use applications. Considering demand and recent challenges, this perspective review is an attempt to describe state-of-the-art biosensors based on functional graphene. Special emphasis is given to elucidating the mechanism of sensing while discussing different applications. Further, we describe the future prospects of functional GO-based biosensors for health care and environmental monitoring with a focus on additive manufacturing such as 3D printing.

Applying Cryo-X-ray Photoelectron Spectroscopy to Study the Surface Chemical Composition of Fungi and Viruses

Interaction between microorganisms and their surroundings are generally mediated via the cell wall or cell envelope. An understanding of the overall chemical composition of these surface layers may give clues on how these interactions occur and suggest mechanisms to manipulate them. This knowledge is key, for instance, in research aiming to reduce colonization of medical devices and device-related infections from different types of microorganisms. In this context, X-ray photoelectron spectroscopy (XPS) is a powerful technique as its analysis depth below 10 nm enables studies of the outermost surface structures of microorganism. Of specific interest for the study of biological systems is cryogenic XPS (cryo-XPS). This technique allows studies of intact fast-frozen hydrated samples without the need for pre-treatment procedures that may cause the cell structure to collapse or change due to the loss of water. Previously, cryo-XPS has been applied to study bacterial and algal surfaces with respect to their composition of lipids, polysaccharides and peptide (protein and/or peptidoglycan). This contribution focuses onto two other groups of microorganisms with widely different architecture and modes of life, namely fungi and viruses. It evaluates to what extent existing models for data treatment of XPS spectra can be applied to understand the chemical composition of their very different surface layers. XPS data from model organisms as well as reference substances representing specific building blocks of their surface were collected and are presented. These results aims to guide future analysis of the surface chemical composition of biological systems.

A novel robust adsorbent for efficient oil/water separation: Magnetic carbon nanospheres/graphene composite aerogel

Recently, graphene aerogels (GAs) have attracted considerable research attention in oil/water separation owing to their remarkable properties. However, the serious stacking of graphene oxide nanosheets (GO) would lead to low adsorption capacity and poor recyclability. For the first time, with alkaline ammonium citrate as reducing agent and nitrogen source, the point-to-face contact between magnetic carbon nanospheres (MCNS) and graphene sheets was adopted to effectively inhibit the aggregation of graphene sheets. Nitrogen-doped magnetic carbon nanospheres/graphene composite aerogels (MCNS/NGA) were fabricated under weakly alkaline conditions by one-step hydrothermal in-situ electrostatic self-assembling strategy. The aerogels have low density, super-elasticity (up to 95 % compression), high specific surface area (787.92 m² g^-1) and good magnetic properties. Therefore, they exhibit adsorption capacity in the range of 187-537 g g^-1 towards various organic solvents and oils, superior to most reported materials to date. In addition, thanks to their good mechanical properties, excellent thermal stability and flame retardancy, they can be regenerated by squeezing, distillation and combustion. More importantly, magnetic control technology can be adopted to realize oriented adsorption and facilitate recycling of organic solvents and oils in extreme environments.

Enhanced passivation of lead with immobilized phosphate solubilizing bacteria beads loaded with biochar/ nanoscale zero valent iron composite

Phosphate solubilizing bacteria (PSBs) can effectively enhance the stability of lead via the formation of insoluble Pb-phosphate compounds. This research presents a bio-beads, which was implemented with the help of a self-designed porous spheres carrier, by immobilized PSBs strains Leclercia adecarboxylata (hereafter referred as L1-5). In addition, the passivation efficiency of lead via bio-beads under different conditions and its mechanism were also investigated in this study. The results indicated that phosphate solubilized by bio-beads could reach 30 mg/L in Ca₃(PO₄)₂ medium containing 1 mM Pb²⁺, and the highest removal rate of Pb²⁺ in beef peptone liquid medium could reach 93%, which is better than that of free bacteria. Furthermore, it was also concluded that the lead could be transformed into stable crystal texture, such as Pb₅(PO₄)₃Cl and Pb₅(PO₄)₃OH. Both hydrophobic and hydrophilic groups in the bio-beads could capture Pb²⁺, which indicated that electrostatic attraction and ion-exchange were also the mechanism of Pb²⁺ adsorption. All the experimental findings demonstrated that this bio-bead could be consider as an efficient way for the lead immobilization in contaminated soil in the future.

Enhanced adsorption-coupled reduction of hexavalent chromium by 2D poly(m-phenylenediamine)-functionalized reduction graphene oxide

To improve the mass transfer efficiency of poly(m-phenylenediamine) for the effective removal of hexavalent chromium (Cr (VI)) from aqueous solution, a facile and one-step method to prepare two-dimensional poly(m-phenylenediamine) functionalized reduction graphene oxide (rGO-PmPD) by dilution polymerization is developed. The structure and morphology of rGO-PmPD as well as rGO and PmPD were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), Fourier-transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Raman, and X-ray diffraction (XRD). The preparation mechanism, adsorption performance, and mechanism of rGO-PmPD were then investigated in detail. The obtained rGO-PmPD exhibited thin 2D nanosheet morphology with much improved specific surface area and pore volume (18 and 25 times higher than that of PmPD, respectively). The Cr (VI) adsorption of rGO-PmPD was fitted well with the pseudo-second-order kinetic model and Langmuir isotherm model, and the maximum adsorption capacity of rGO-PmPD reached 588.26 mg g^-1, higher than that of PmPD (400 mg g^-1) and rGO (156.25 mg g^-1). Moreover, the regeneration efficiency of the rGO-PmPD nanosheet is also promising that the adsorption performance after five times of adsorption-desorption cycles still maintains more than 530 mg g^-1. The removal mechanism involved reduction coupled with adsorption and electrostatic interaction between rGO-PmPD and Cr (VI), and ~ 65% of Cr (VI) removal was attributed to reduction and ~ 35% was ascribed to adsorption and electrostatic interaction. This study thus provides a simple and effective route to achieve high accessible surface area of adsorbent materials with enhanced mass transfer efficiency and thereafter improved adsorption performance.

Simultaneous adsorption of As(III), Cd(II) and Pb(II) by hybrid bio-nanocomposites of nano hydroxy ferric phosphate and hydroxy ferric sulfate particles coating on Aspergillus niger

To develop an efficient, convenient and cost-effective method to simultaneously remove pollution of As(III), Cd(II) and Pb(II) in wastewater, a strategy to fabricate hybrid bio-nanocomposites ((n-HFP + n-HFS)@An) of nano hydroxy ferric phosphate (n-HFP) and hydroxy ferric sulfate (n-HFS) particles coating on Aspergillus niger was applied. The scanning electron microscope and energy dispersive spectrum analyses showed that (n-HFP + n-HFS)@An composites had been successfully developed which well solved the self-agglomeration problem of the nano particles. Comparing to the bulk nanoparticles, the adsorption rates of the (n-HFP + n-HFS)@An composites for the three metals were promoted 145.34, 28.98 and 25.18% and reached 76.84, 73.62 and 94.31%, respectively. Similarly, the adsorption capacities for As(III), Cd(II), and Pb(II) were 162.00, 205.83 and 730.79 mg/g, respectively. Moreover, the pseudo-second-order kinetic model was more relevant to the adsorption on the three metals by (n-HFP + n-HFS)@An, and adsorbing As(III) was fitted to the Freundlich isotherm model, while the adsorption on Cd(II) or Pb(II) was related to the Langmuir isotherm model. In addition, the adsorption of Cd(II) and Pb(II) was associated with transformation of hydroxyl groups and precipitation with phosphate. As(III) was adsorbed through exchange between AsO₂^- and SO₄^2- in the (n-HFP + n-HFS)@An composites.

In vivo and in vitro efficient textile wastewater remediation by Aspergillus niger biosorbent

In this work, the treatment of textile wastewater by a facile and high-efficiency technology using eco-friendly Aspergillus niger as a biosorbent was investigated. We measured physical changes (weight, size) during the formation and growth of fungus pellets and the pH values that influence the adsorption performance and biosorption mechanism. Three acid anionic dyes containing Acid Orange 56, Acid Blue 40 and Methyl Blue were chosen as model dyes to investigate batch adsorption efficiency. Two adsorption models (in vivo and in vitro) were adopted to decolorize the acid dyes. The results show that fungus pellets have excellent decoloration abilities with a high adsorption efficiency of 98% for 200 mg L-1 of acid dye. The pH value of the dye solution varied with the adsorption time and the dye removal efficiency greatly depended on the pH. The bioadsorption mechanism of nano-scale hyphae was revealed to be mainly due to electrostatic interactions caused by the pH change. Furthermore, the surface morphologies of the fungus after adsorption indicated that the dyes had been adsorbed on the surface of the fungus mycelia. Moreover, prepared 3D fungus/GO aerogels demonstrated superior dye removal abilities compared with fungus aerogels.

Synergetic effects of graphene–CoPc/silk fibroin three-dimensional porous composites as catalysts for acid red G degradation

The disposal of dye wastewater is one of the hotspots of scientific research, and graphene–CoTAPc–SF composites exhibit more effective catalytic abilities.

Sacrificial template induced interconnected bubble-like N-doped carbon nanofoam as a pH-universal electrocatalyst for an oxygen reduction reaction

In this paper, a controllable and scalable method to synthesize porous N-doped carbon nano-foams with pH-universal ORR activity is presented.

Hydrogel applications for adsorption of contaminants in water and wastewater treatment

During the last decade, hydrogels have been used as potential adsorbents for removal of contaminants from aqueous solution. To improve the adsorption efficiency, there are numerous different particles that can be chosen to encapsulate into hydrogels and each particle has their respective advantages. Depending on the type of pollutants and approaching method, the particles will be used to prepare hydrogels. The hydrogels commonly applied in water/wastewater treatment was mainly classified into three classes according to their shape included hydrogel beads, hydrogel films, and hydrogel nanocomposites. In review of many recently research papers, we take a closer look at hydrogels and their applications for removal of contaminants, such as heavy metal ion, dyes, and radionuclides from water/wastewater in order to elucidate the reactions between contaminants and particles and potential for recycling and regeneration of the post-treatment hydrogels. Graphical abstract ᅟ.

Simultaneous immobilization of cadmium and lead in contaminated soils by hybrid bio-nanocomposites of fungal hyphae and nano-hydroxyapatites

Self-aggregation of bulk nano-hydroxyapatites (n-HAPs) undermines their immobilization efficiencies of heavy metals in the contaminated soils. Here, the low-cost, easily obtained, and environment-friendly filamentous fungi have been introduced for the bio-matrices of the hybrid bio-nanocomposites to potentially solve such problem of n-HAPs. According to SEM, TEM, XRD, and FT-IR analyses, n-HAPs were successfully coated onto the fungal hyphae and their self-aggregation was improved. The immobilization efficiencies of diethylene-triamine-pentaacetic acid (DTPA)-extractable Cd and Pb in the contaminated soils by the bio-nanocomposites were individually one to four times of that by n-HAPs or the fungal hyphae. Moreover, the Aspergillus niger-based bio-nanocomposite (ANHP) was superior to the Penicillium Chrysogenum F1-based bio-nanocomposite (PCHP) in immobilization of Cd and Pb in the contaminated soils. In addition, the results of XRD showed that one of the potential mechanisms of metal immobilization by the hybrid bio-nanocomposites was dissolution of n-HAPs followed by precipitation of new metal phosphate minerals. Our results suggest that the hybrid bio-nanocomposite (ANHP) can be recognized as a promising soil amendment candidate for effective remediation on the soils simultaneously contaminated by Cd and Pb.

Efficient removal of Cr(VI) from water by quaternized chitin/branched polyethylenimine biosorbent with hierarchical pore structure

A novel chitin-based biosorbent (QCP) was synthesized by cross-linking quaternized chitin and branched polyethylenimine with the aid of epichlorohydrin for efficient removal of Cr(VI) from water. Because it possessed both quaternary ammonium groups and amino groups as well as the hierarchical pore structure, QCP presented a maximum adsorption capacity of 387.7 mg/g according to the Langmuir isotherm at 25 °C. The biosorption of QCP achieved the equilibrium within 40 min and followed the pseudo-second-order kinetic model. QCP worked well even in the solution with high pH and high content of competing anions and, it exhibited an excellent reusability. The main Cr(VI) uptake mechanism was confirmed to be electrostatic attractions between Cr(VI) anions and quaternary ammonium groups as well as the protonated amino groups, and followed by partial reduction of Cr(VI) to Cr(III) by amines and hydroxyls. This work may provide a potential for Cr(VI) removal by chitin-based biosorbents.

Determining the Mechanism and Efficiency of Industrial Dye Adsorption through Facile Structural Control of Organo-montmorillonite Adsorbents

The structural evolution of cost-effective organo-clays (montmorillonite modified with different loadings of CTAB (cetyltrimethylammonium bromide)) is investigated and linked to the adsorption uptake and mechanism of an important industrial dye (hydrolyzed Remazol Black B). Key organo-clay characteristics, such as the intergallery spacing and the average number of well-stacked layers per clay stack, are determined by low-angle X-ray diffraction, while differential thermogravimetric analysis is used to differentiate between surface-bound and intercalated CTAB. Insights into the dye adsorption mechanism are gained through the study of the adsorption kinetics and through the characterization of the organo-clay structure and surface charge after dye adsorption. It is shown that efficient adsorption of anionic industrial dyes is driven by three key parameters: (i) sufficiently large intergallery spacing to enable accommodation of the relatively large dye molecules, (ii) crystalline disorder in the stacking direction of the clay platelets to facilitate dye access, (iii) and positive surface charge to promote interaction with the anionic dyes. Specifically, it is shown that, at low modifier loadings (0.5 cation exchange capacity (0.5CEC)), CTAB molecules exclusively intercalate as a monolayer into the clay intergallery spaces, while, with increasing modifier loadings, the CTAB molecules adopt a bilayer arrangement and adsorb onto the exterior clay surface. Bilayer intercalation results in sufficiently large expansion of the intergallery spaces and significant disordering along the (001) stacking direction to enable high and relatively fast dye uptake via intraparticle diffusion. Poor and slow dye uptake is observed for the organo-clays with a monolayer structure, suggesting relatively inefficient dye adsorption at the clay edges. The optimized bilayer organo-clays (montmorillonite modified with 3CEC of CTAB) also show enhanced adsorption efficiencies for other important industrial dyes, highlighting the importance of structural control in organo-clays while also showing the adsorbents' great potential for use in industry where dye mixtures are encountered.

Synergic Adsorption-Biodegradation by an Advanced Carrier for Enhanced Removal of High-Strength Nitrogen and Refractory Organics

Coking wastewater contains not only high-strength nitrogen but also toxic biorefractory organics. This study presents simultaneous removal of high-strength quinoline, carbon, and ammonium in coking wastewater by immobilized bacterial communities composed of a heterotrophic strain Pseudomonas sp. QG6 (hereafter referred as QG6), ammonia-oxidizing bacteria (AOB), and anaerobic ammonium oxidation bacteria (anammox). The bacterial immobilization was implemented with the help of a self-designed porous cubic carrier that created structured microenvironments including an inner layer adapted for anaerobic bacteria, a middle layer suitable for coaggregation of certain aerobic and anaerobic bacteria, and an outer layer for heterotrophic bacteria. By coating functional polyurethane foam (FPUF) with iron oxide nanoparticles (IONPs), the biocarrier (IONPs-FPUF) could provide a good outer-layer barrier for absorption and selective treatment of aromatic compounds by QG6, offer a conducive environment for anammox in the inner layer, and provide a mutualistic environment for AOB in the middle layer. Consequently, simultaneous nitrification and denitrification were reached with the significant removal of up to 322 mg L^-1 (98%) NH₄, 311 mg L^-1 (99%) NO₂, and 633 mg L^-1 (97%) total nitrogen (8 mg L^-1 averaged NO₃ concentration was recorded in the effluent), accompanied by an efficient removal of chemical oxygen demand by 3286 mg L^-1 (98%) and 350 mg L^-1 (100%) quinoline. This study provides an alternative way to promote synergic adsorption and biodegradation with the help of a modified biocarrier that has great potential for treatment of wastewater containing high-strength carbon, toxic organic pollutants, and nitrogen.