Gold Recovery from E-Waste by Food-Waste Amyloid Aerogels

Demand for gold recovery from e-waste grows steadily due to its pervasive use in the most diverse technical applications. Current methods of gold recovery are resource-intensive, necessitating the development of more efficient extraction materials. This study explores protein amyloid nanofibrils (AF) derived from whey, a dairy industry side-stream, as a novel adsorbent for gold recovery from e-waste. To do so, AF aerogels are prepared and assessed against gold adsorption capacity and selectivity over other metals present in waste electrical and electronic equipment (e-waste). The results demonstrate that AF aerogel has a remarkable gold adsorption capacity (166.7 mg g-1) and selectivity, making it efficient and an adsorbent for gold recovery. Moreover, AF aerogels are efficient templates to convert gold ions into single crystalline flakes due to Au growth along the (111) plane. When used as templates to recover gold from e-waste solutions obtained by dissolving computer motherboards in suitable solvents, the process yields high-purity gold nuggets, constituted by ≈90.8 wt% gold (21-22 carats), with trace amounts of other metals. Life cycle assessment and techno-economic analysis of the process finally consolidate the potential of protein nanofibril aerogels from food side-streams as an environmentally friendly and economically viable approach for gold recovery from e-waste.

Interaction of chitosan with nanoplastic in water: The effect of environmental conditions, particle properties, and potential for in situ remediation

Micro- and nanoplastic (MNP) pollution in aquatic ecosystems requires investigation on its source, transport, and extent to assess and mitigate its risks. Chitosan is a potential biomolecule for water treatment, but its interaction with MNP is undefined. In this work, chitosan-nanoplastic interaction was explored in the laboratory under environmentally relevant conditions using polystyrene (PS) nanoplastic (NP) as model particle to identify conditions at which PS-chitosan interaction resulted in aggregation. Aggregation limits NP transport and allows separation of NP for targeted remediation. The effect of environmental conditions (pH, salinity, dissolved organic matter (DOM) content), chitosan particle size and NP surface modification on chitosan-NP interaction was studied at various chitosan doses. PS aggregated at chitosan doses as low as 0.2 % w/w, while higher doses of chitosan resulted in re-stabilization of NP in solution, restoring the particle size to its initial value. Increasing pH, DOM, or carboxyl modification of the NP surface also improved NP stability in solution. Increased salinity of the solution caused aggregation of unmodified PS independent of chitosan, but carboxyl-modified PS remained stable and aggregated at the same chitosan doses across all salinity levels. Chitosan with low molecular weight promoted PS aggregation at lower doses. Notably, zeta potential (ZP) alone did not indicate chitosan-induced PS aggregation, which occurred independently of changes in ZP. DLVO calculations based on ZP, however, still indicated attractive interaction due to charge differences, albeit with less contrast at high pH, salinity, and DOM content. Additional insights gained in the work recommend caution when using spectrophotometric methods to assess NP removal. Overall, this study demonstrates that chitosan impacts NP transport and holds potential for water remediation of NP.

Well-designed protein amyloid nanofibrils composites as versatile and sustainable materials for aquatic environment remediation: A review

Amyloid nanofibrils (ANFs) are supramolecular polymers originally classified as pathological markers in various human degenerative diseases. However, in recent years, ANFs have garnered greater interest and are regarded as nature-based sustainable biomaterials in environmental science, material engineering, and nanotechnology. On a laboratory scale, ANFs can be produced from food proteins via protein unfolding, misfolding, and hydrolysis. Furthermore, ANFs have specific structural characteristics such as a high aspect ratio, good rigidity, chemical stability, and a controllable sequence. These properties make them a promising functional material in water decontamination research. As a result, the fabrication and application of ANFs and their composites in water purification have recently gained considerable attention. Despite the large amount of literature in this field, there is a lack of systematic review to assess the gap in using ANFs and their composites to remove contaminants from water. This review discusses significant advancements in design techniques as well as the physicochemical properties of ANFs-based composites. We also emphasize the current progress in using ANFs-based composites to remove inorganic, organic, and biological contaminants. The interaction mechanisms between ANFs-based composites and contaminants are also highlighted. Finally, we illustrate the challenges and opportunities associated with the future preparation and application of ANFs-based composites. We anticipate that this review will shed new light on the future design and use of ANFs-based composites.

Coagulative removal of microplastics from aqueous matrices: Recent progresses and future perspectives

Coagulation-flocculation-sedimentation (CFS) system has been identified as one of the favored treatment technique in water/wastewater treatment systems and hence, it is crucial to comprehend the efficacy of different coagulants used in removing microplastics (MPs) from aqueous matrices. Henceforth, this study critically reviews the recent progress and efficacy of different coagulants used to date for MPs removal. This includes laboratory and field-scale studies on inorganic and organic coagulants, as well as laboratory-scale studies on natural coagulants. Inorganic and organic coagulants have varying MPs removal efficiencies such as: Fe/Al-salts (30 %-95 %), alum (99 %), and poly aluminum chloride (13 %-97 %), magnesium hydroxide (84 %), polyamine (99 %), organosilanes (>95 %), and polyacrylamide (85 %-98 %). Moreover, studies have highlighted the use of natural coagulants, such as chitosan, protein amyloid fibrils, and starch has shown promising results in MPs removal with sevral advantages over traditional coagulants. These natural coagulants have demonstrated high MPs removal efficiencies with chitosan-tannic acid (95 %), protein amyloid fibrils (98 %), and starch (>90 %). Moreover, the MPs removal efficiencies of natural coagulants are compared and their predominant removal mechanisms are determined. Plant-based natural coagulants can potentially remove MPs through mechanisms such as polymer bridging and charge neutralization. Further, a systematic analysis on the effect of operational parameters highlights that the pH affects particle surface charge and coagulation efficiency, while mixing speed affects particle aggregation and sedimentation. Also, the optimal mixing speed for effective MPs removal depends on coagulant type and concentration, water composition, and MPs characteristics. Moreover, this work highlights the advantages and limitations of using different coagulants for MPs removal and discusses the challenges and future prospects in scaling up these laboratory studies for real-time applications.

Interfacial Electrostatic Self-Assembly of Amyloid Fibrils into Multifunctional Protein Films

Amyloid fibrils have generated steadily increasing traction in the development of natural and artificial materials. However, it remains a challenge to construct bulk amyloid films directly from amyloid fibrils due to their intrinsic brittleness. Here, a facile and general methodology to fabricate macroscopic and tunable amyloid films via fast electrostatic self-assembly of amyloid fibrils at the air-water interface is introduced. Benefiting from the excellent templating properties of amyloid fibrils for nanoparticles (such as conductive carbon nanotubes or magnetic Fe₃ O₄ nanoparticles), multifunctional amyloid films with tunable properties are constructed. As proof-of-concept demonstrations, a magnetically oriented soft robotic swimmer with well-confined movement trajectory is prepared. In addition, a smart magnetic sensor with high sensitivity to external magnetic fields is fabricated via the combination of the conductive and magnetic amyloid films. This strategy provides a convenient, efficient, and controllable approach for the preparation of amyloid-based multifunctional films and related smart devices.

Ion release and local effects of titanium metal particles from dental implants: An experimental study in rats

BACKGROUND

The objective of this study was to evaluate the accumulation of ions in blood and organs caused by titanium (Ti) metal particles in a mandibular defect in rats, together with a description of the local reaction of oral tissues to this Ti alloy debris.

METHODS

Twenty Sprague-Dawley rats were randomly distributed into three groups: an experimental group with a mandibular bone defect filled with metallic debris obtained by implantoplasty; a positive control group; and a negative control group. Thirty days after surgery, the rats were euthanized and perilesional tissue surrounding the mandibular defect was removed, together with the lungs, spleen, liver, and brain. Two blood samples were collected: immediately before surgery and before euthanasia. The perilesional tissue was histologically analyzed using hematoxylin-eosin staining, and Ti, aluminum, and vanadium ion concentrations in blood and organs were measured by TQ-ICP-MS. Descriptive and bivariate analyses of the data were performed.

RESULTS

All rats with implanted metal debris showed metal particles and a bone fracture callus on the osseous defect. The metal particles were surrounded by a foreign body reaction characterized by the presence of histiocytes and multinucleated giant cells (MNGCs). The experimental group had a significant higher concentration of Ti ions in all studied organs except lung tissue (p < 0.05). In addition, there were more V ions in the brain in the experimental group (p = 0.008).

CONCLUSIONS

Although further studies are required to confirm the clinical relevance of these results, Ti metal particles in the jaw might increase the concentration of metal ions in vital organs and induce a foreign body reaction.

Amyloid-Templated Palladium Nanoparticles for Water Purification by Electroreduction

Electrocatalysis offers great promise for water purification but is limited by low active area and high uncontrollability of electrocatalysts. To overcome these constraints, we propose hybrid bulk electrodes by synthesizing and binding a Pd nanocatalyst (nano-Pd) to the electrodes via amyloid fibrils (AFs). The AFs template is effective for controlling the nucleation, growth, and assembly of nano-Pd on the electrode. In addition, the three-dimensional hierarchically porous nanostructure of AFs is beneficial for loading high-density nano-Pd with a large active area. The novel hybrid cathodes exhibit superior electroreduction performance for the detoxification of hexavalent chromium (Cr6+ ), 4-chlorophenol, and trichloroacetic acid in wastewater and drinking water. This study provides a proof-of-concept design of an AFs-templated nano-Pd-based hybrid electrode, which constitutes a paradigm shift in electrocatalytic water purification, and broadens the horizon of its potential engineered applications.

Oat Plant Amyloids for Sustainable Functional Materials

Amyloid functional materials from amyloid fibril building blocks, produced in vitro from amyloidogenic natural proteins or synthetic peptides, show diverse functionalities ranging from environmental science and biomedicine, to nanotechnology and biomaterials. However, sustainable and affordable sources of amyloidogenic proteins remain the bottleneck for large-scale applications, and to date, interest remains essentially limited to fundamental studies. Plant-derived proteins would be an ideal source due to their natural abundance and low environmental impact. Hereby oat globulin, the primary protein of oat plant (Avena sativa), is utilized to yield high-quality amyloid fibrils and functional materials based thereof. These fibrils show a rich multistranded ribbon-like polymorphism and a fibrillization process with both irreversible and reversible pathways. The authors furthermore fabricate oat-amyloid aerogels, films, and membranes for possible use in water purification, sensors, and patterned electrodes. The sustainability footprint of oat-amyloids against other protein sources is demonstrated, anticipating an environmentally-efficient platform for advanced materials and technologies.

Biopolymer-Based Membrane Adsorber for Removing Contaminants from Aqueous Solution: Progress and Prospects

The demand for energy-efficient water treatment as well as the limitation in adsorption of existing membranes has motivated the pursuit of membranes that can break the selectivity-permeability trade-off and provide high selective adsorption for chemicals of interest. The membrane adsorbers have received a lot of attention for removing contaminants from aqueous solution due to combine both advantages of adsorption and membrane separation. Membrane adsorbers constructed by biopolymer with many functional groups are widely used in water purification, because the biopolymers are easily available from biomass materials in nature, degradable, and low-cost. This paper summarizes the characteristics and important development direction of these types of biomass-based membrane adsorption materials to adsorb organic/inorganic contaminants of water and analyzes the preparation methods of natural biomacromolecule cellulose, chitosan, sodium alginate, and protein to construct the membrane adsorption materials, as well as the application of pollutant removal from aqueous solutions. According to the current problems and shortcomings in the research of biopolymer-based membrane adsorbers, it is proposed to improve the understanding of the adsorption mechanism of biopolymer-based membrane adsorbers and accelerate the development of practical applications as the focus of future research.

Sustainable Removal of Microplastics and Natural Organic Matter from Water by Coagulation-Flocculation with Protein Amyloid Fibrils

Water contamination is a global threat due to its damaging effects on the environment and human health. Water pollution by microplastics (MPs), dissolved natural organic matter (NOM), and other turbid particles is ubiquitous in water treatment. Here, we introduce lysozyme amyloid fibrils as a novel natural bio-flocculant and explore their ability to flocculate and precipitate the abovementioned undesired colloidal objects. Thanks to their positively charged surface in a very broad range of pH, lysozyme amyloid fibrils show an excellent turbidity removal efficiency of 98.2 and 97.9% for dispersed polystyrene MPs and humic acid (HA), respectively. Additionally, total organic carbon measurements confirm these results by exhibiting removal efficiencies of 93.4 and 61.9% for purifying water from dispersed MPs and dissolved HA, respectively. The comparison among amyloid fibrils, commercial flocculants (FeCl₃ and polyaluminumchloride), and native lysozyme monomers points to the superiority of amyloid fibrils at the same dosage and sedimentation time. Furthermore, the turbidity of pristine and MP-spiked wastewater and lake water decreased after the treatment by amyloid fibrils, validating their coagulation-flocculation performance under natural conditions. All these results demonstrate lysozyme amyloid fibrils as an appropriate natural bio-flocculant for removing dispersed MPs, NOM, and turbid particles from water.

Protein nanofibrils for next generation sustainable water purification

Water scarcity is rapidly spreading across the planet, threatening the population across the five continents and calling for global sustainable solutions. Water reclamation is the most ecological approach for supplying clean drinking water. However, current water purification technologies are seldom sustainable, due to high-energy consumption and negative environmental footprint. Here, we review the cutting-edge technologies based on protein nanofibrils as water purification agents and we highlight the benefits of this green, efficient and affordable solution to alleviate the global water crisis. We discuss the different protein nanofibrils agents available and analyze them in terms of performance, range of applicability and sustainability. We underline the unique opportunity of designing protein nanofibrils for efficient water purification starting from food waste, as well as cattle, agricultural or dairy industry byproducts, allowing simultaneous environmental, economic and social benefits and we present a case analysis, including a detailed life cycle assessment, to establish their sustainable footprint against other common natural-based adsorbents, anticipating a bright future for this water purification approach.

Half a century of amyloids: past, present and future

Amyloid diseases are global epidemics with profound health, social and economic implications and yet remain without a cure. This dire situation calls for research into the origin and pathological manifestations of amyloidosis to stimulate continued development of new therapeutics. In basic science and engineering, the cross-β architecture has been a constant thread underlying the structural characteristics of pathological and functional amyloids, and realizing that amyloid structures can be both pathological and functional in nature has fuelled innovations in artificial amyloids, whose use today ranges from water purification to 3D printing. At the conclusion of a half century since Eanes and Glenner's seminal study of amyloids in humans, this review commemorates the occasion by documenting the major milestones in amyloid research to date, from the perspectives of structural biology, biophysics, medicine, microbiology, engineering and nanotechnology. We also discuss new challenges and opportunities to drive this interdisciplinary field moving forward.

Transition Metal Dichalcogenide-Silk Nanofibril Membrane for One-Step Water Purification and Precious Metal Recovery

With the rapid worldwide industrial development, large amounts of pollutants such as heavy metals are discharged into the water sources, causing a huge threat to living beings. To mitigate this issue, there is an urgent need for new water treatment strategies. Inspired by a natural shell nacre structure and a multidimensional hybrid concept, we demonstrate multilayered inorganic-organic hybrid membranes using metallic molybdenum disulfide (MoS₂) as two-dimensional transition metal dichalcogenide nanosheets and one-dimensional silk nanofibrils for water purification. Because of its possessing negatively charged layers and interaction sites, the hybrid film could adsorb metal ions and dyes from water. The separation performance can be tuned by changing the component ratios of these two nanomaterials. During filtration, due to the reducing effect of the MoS₂ nanosheets, precious metal ions are reduced to their nanoparticle form without any further thermal or chemical treatments. In addition to the one-step removal and recovery of metal ions, the hybrid membranes exhibit excellent potential for the determination and removal of different dyes from water. The results of this research can open up an effective and green avenue for water purification and recovery of metal ions dissolved in water.

Dual nanofibrillar-based bio-sorbent films composed of nanocellulose and lysozyme nanofibrils for mercury removal from spring waters

The present study explores the preparation of dual nanofibrillar-based bio-sorbent films composed of cellulose nanofibrils (CNFs) and lysozyme nanofibrils (LNFs) for application in the removal of Hg(II) from aqueous solutions. The free-standing films were fabricated via simple vacuum filtration of water suspensions of CNFs and LNFs and disclose good mechanical and thermal properties. The Hg(II) removal efficiency was evaluated by atomic fluorescence spectroscopy in ultra-pure and natural spring waters contaminated with environmental realistic levels of mercury (50 μg L^-1). The removal efficiency is pH-dependent reaching a maximum of 99 % after 24 h at a pH value close to the isoelectric point of the protein. Under the experimental conditions, the sorption kinetics are well described by the pseudo-second-order and Elovich models, suggesting a chemisorption mechanism. These results demonstrate the ability of the dual nanofibrillar-based films to remove Hg(II) from water samples reaching a residual concentration lower than the guideline value for water intended for human consumption (1 μg L^-1). Therefore, the CNFs/LNFs bio-sorbents might be a solution to treat low-concentrated mercury-contaminated waters.

Amyloid Fibrils Aerogel for Sustainable Removal of Organic Contaminants from Water

Water contamination by organic pollutants is ubiquitous and hence a global concern due to detrimental effects on the environment and human health. Here, it is demonstrated that amyloid fibrils aerogels are ideal adsorbers for removing organic pollutants from water. To this end, amyloid fibrils prepared from β-lactoglobulin, the major constituent of milk whey protein, are used as building blocks for the fabrication of the aerogels. The adsorption of Bentazone, Bisphenol A, and Ibuprofen, as model pollutants, is evaluated under quasi-static conditions, without use of energy or pressure. Through adsorption by amyloid fibrils aerogel, excellent removal efficiencies of 92%, 78%, and 98% are demonstrated for Bentazone, Bisphenol A, and Ibuprofen, respectively. Furthermore, the maximum adsorption capacity of amyloid fibrils aerogel for Bentazone, Bisphenol A, and Ibuprofen is 54.2, 50.6, and 69.6 mg g^-1 , respectively. To shed light on the adsorption equilibrium process, adsorption isotherms, binding constants, saturation limits, and the effect of pH are evaluated. Finally, the regeneration of the aerogel over three consecutive cycles is studied, exhibiting high reusability with no significant changes in its removal performance. These results point at amyloid fibrils aerogels as a sustainable, efficient, and inexpensive technology for alleviating the ubiquitous water contamination by organic pollutants.