Nanostructured Materials for Water Purification: Adsorption of Heavy Metal Ions and Organic Dyes

Approaches for the Efficient Removal of Fluoride from Groundwater: A Comprehensive Review

Contamination of groundwater with fluoride represents a significant global issue, with high concentrations posing serious public health threats. While fluoride is a critical element in water, excessive levels can be detrimental to human health and potentially life-threatening. Addressing the challenge of removing fluoride from underground water sources via nanotechnological approaches is a pressing concern in environmental science. To collate relevant information, extensive literature searches were conducted across multiple databases, including Google Scholar, PubMed, Scopus, Web of Science, the American Chemical Society, Elsevier, Springer, and the Royal Society of Chemistry. VOS Viewer software version 1.6.20 was employed for a systematic review. This article delivers an exhaustive evaluation of various groundwater fluoride removal techniques, such as adsorption, membrane filtration, electrocoagulation, photocatalysis, and ion exchange. Among these, the application of nanoparticles emerges as a notable method. The article delves into nano-compounds, optimizing conditions for the fluoride removal process and benchmarking their efficacy against other techniques. Studies demonstrate that advanced nanotechnologies-owing to their rapid reaction times and potent oxidation capabilities-can remove fluoride effectively. The implementation of nanotechnologies in fluoride removal not only enhances water quality but also contributes to the safeguarding of human health.

Simultaneous removal of calcium, cadmium and tetracycline from reverse osmosis wastewater by sycamore deciduous biochar, shell powder and polyurethane sponge combined with biofilm reactor

The treatment of reverse osmosis concentrate generated from urban industrial sewage for resource recovery has been hot. In this research, a biofilm reactor was constructed by combining sycamore deciduous biochar, shell powder, and polyurethane sponge loaded with Zobellella denitrificans sp. LX16. For ammonia nitrogen (NH4+-N), calcium (Ca2+), chemical oxygen demand (COD), cadmium (Cd2+), and tetracycline (TC), the removal efficiencies were 98.69 %, 83.95 %, 97.26 %, 98.34 %, and 69.12 % at a hydraulic retention time (HRT) of 4 h, pH of 7.0, and influent salinity, Ca2+, and TC concentrations of 1.0, 180.0, and 3.0 mg/L, respectively. The biofilm reactor packing has a three-dimensional structure to ensure good loading of microorganisms while promoting electron transfer and metabolic activity of microorganisms and increasing the pollutant tolerance and removal efficiency. The reactor provides a practical reference for the sedimentation of reverse osmosis concentrate to remove Cd2+ and TC by microbial induced calcium precipitation (MICP).

Application of Fe-MOFs in Photodegradation and Removal of Air and Water Pollutants: A Review

Photocatalytic technology has received increasing attention in recent years. A pivotal facet of photocatalytic technology lies in the development of photocatalysts. Porous metal-organic framework (MOF) materials, distinguished by their unique properties and structural characteristics, have emerged as a focal point of research in the field, finding widespread application in the photo-treatment and conversion of various substances. Fe-based MOFs have attained particular prominence. This review explores recent advances in the photocatalytic degradation of aqueous and gaseous substances. Furthermore, it delves into the interaction between the active sites of Fe-MOFs and pollutants, offering deeper insights into their mechanism of action. Fe-MOFs, as photocatalysts, predominantly facilitate pollutant removal through redox processes, interaction with acid sites, the formation of complexes with composite metal elements, binding to unsaturated metal ligands (CUSs), and hydrogen bonding to modulate their respiratory behavior. This review also highlights the focal points of future research, elucidating the challenges and opportunities that lie ahead in harnessing the characteristics and advantages of Fe-MOF composite catalysts. In essence, this review provides a comprehensive summary of research progress on Fe-MOF-based catalysts, aiming to serve as a guiding reference for other catalytic processes.

The influence of magnetic particle incorporation on bisphenol A removal by β-cyclodextrin-derived sorbent

A novel, biomass-derived hybrid sorbent Ban-CD-EPI-Fe was successfully synthesized in a coprecipitation method, in which β-cyclodextrin copolymerized with banana peel extract and epichlorohydrin was grafted onto an iron oxide surface. The composition, presence of functional groups, morphology, thermal stability, and magnetic properties of the obtained material were characterized by Powder X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Thermogravimetric Analysis (TGA), and Physical Properties Measurement System (PPMS). The material bearing around 28% of β-cyclodextrin units has mesoporous structure with plate-like morphology and active surface area determined by BET and Langmuir models equal to 38.35 and 53.59 m2 g-1, respectively. The sorption studies aimed to remove an endocrine disruptor - bisphenol A (BPA), from water. The results showed that the time evolution could be fitted with pseudo-second kinetic order with a rate constant k equal to 0.05 g mg-1 min-1. According to the Langmuir isotherm, a monolayer is created during BPA sorption, and the maximum sorption capacity was estimated as 93.5 mg g-1. After BPA sorption, the hybrid material could be easily separated by an external magnet and regenerated under mild conditions keeping its recyclability in at least eight cycles.

Preparation, characterisation and applications of bone char, a food waste-derived sustainable material: A review

The production of increasing quantities of by-products is a key challenge for modern society; their valorisation - turning them into valuable compounds with technological applications - is the way forward, in line with circular economy principles. In this review, the conversion of bones (by-products of the agro-food industry) into bone char is described. Bone char is obtained with a process of pyrolysis, which converts the organic carbon into an inorganic graphitic one. Differently from standard biochar of plant origin, however, bone char also contains calcium phosphates, the main component of bone (often hydroxyapatite). The combination of calcium phosphate and graphitic carbon makes bone char a unique material, with different possible uses. Here bone chars' applications in environmental remediation, sustainable agriculture, catalysis and electrochemistry are discussed; several aspects are considered, including the bones used to prepare bone char, the preparation conditions, how these affect the properties of the materials (i.e. porosity, surface area) and its functional properties. The advantages and limitations of bone chars in comparison to traditional biochar are discussed, highlighting the directions the research should take for bone chars' performances to improve. Moreover, an analysis on the sustainability of bone chars' preparation and use is also included.

Chitosan-Bead-Encapsulated Polystyrene Sulfonate for Adsorption of Methylene Blue and Regeneration Studies: Batch and Continuous Approaches

Textile industrialization causes water pollution due to the discharge of industrial effluents into the environment. To reduce the impact of industrial effluent, it must be treated in wastewater treatment plants before discharge into rivers. Among all wastewater treatment approaches, the adsorption process is one method to remove pollutants from wastewater, but it has some limitations in term of reusability and ionic selective adsorption properties. In this study, we prepared cationic poly (styrene sulfonate) (PSS)-incorporated anionic chitosan beads synthesized using the oil-water emulsion coagulation method. The produced beads were characterized using FESEM and FTIR analysis. In batch adsorption studies, the PSS-incorporated chitosan beads exhibited monolayer adsorption processes, that is, exothermic processes that occur spontaneously at low temperatures, which were analyzed based on the adsorption isotherms, adsorption kinetics, and thermodynamics model fittings. The presence of PSS enables cationic methylene blue dye to adsorb to the anionic chitosan structure via electrostatic interaction between the sulfonic group and the dye molecule. The maximum adsorption capacity of PSS-incorporated chitosan beads achieved 42.21 mg/g, as calculated from the Langmuir adsorption isotherm. Finally, the PSS-incorporated chitosan beads demonstrated good regeneration with different types of reagents, especially using sodium hydroxide as a regeneration reagent. With the use of sodium hydroxide regeneration of this adsorbent material, a continuous adsorption setup also demonstrated that PSS-incorporated chitosan beads can be reused for methylene blue adsorption for up to three cycle processes.

Advanced Polymeric Nanocomposite Membranes for Water and Wastewater Treatment: A Comprehensive Review

Nanomaterials have been extensively used in polymer nanocomposite membranes due to the inclusion of unique features that enhance water and wastewater treatment performance. Compared to the pristine membranes, the incorporation of nanomodifiers not only improves membrane performance (water permeability, salt rejection, contaminant removal, selectivity), but also the intrinsic properties (hydrophilicity, porosity, antifouling properties, antimicrobial properties, mechanical, thermal, and chemical stability) of these membranes. This review focuses on applications of different types of nanomaterials: zero-dimensional (metal/metal oxide nanoparticles), one-dimensional (carbon nanotubes), two-dimensional (graphene and associated structures), and three-dimensional (zeolites and associated frameworks) nanomaterials combined with polymers towards novel polymeric nanocomposites for water and wastewater treatment applications. This review will show that combinations of nanomaterials and polymers impart enhanced features into the pristine membrane; however, the underlying issues associated with the modification processes and environmental impact of these membranes are less obvious. This review also highlights the utility of computational methods toward understanding the structural and functional properties of the membranes. Here, we highlight the fabrication methods, advantages, challenges, environmental impact, and future scope of these advanced polymeric nanocomposite membrane based systems for water and wastewater treatment applications.

Polypyrrole-Barium Ferrite Magnetic Cryogels for Water Purification

Magnetic polypyrrole-gelatin-barium ferrite (PPy-G-BaFe) cryogels/aerogels were synthesized by one-step oxidative cryopolymerization of pyrrole in the presence of various fractions of barium ferrite (BaFe) nanoparticles, dispersed in aqueous gelatin solution. The successful incorporation of BaFe into the composites was confirmed by elemental analysis and scanning electron microscopy paired with an energy-dispersive X-ray detector. The maximum achieved content of BaFe in the resulting material was 3.9 wt%. The aerogels with incorporated BaFe had significantly higher specific surface area and conductivity, reaching 19.3 m² g^-1 and 4 × 10^-4 S cm^-1, respectively, compared to PPy-G aerogel, prepared in the absence of BaFe (7.3 m² g^-1 and 1 × 10^-5 S cm^-1). The model adsorption experiment using an anionic dye, Reactive Black 5, showed that magnetic PPy-G-BaFe aerogel, prepared at 10 wt% BaFe fraction, had significantly higher adsorption rate and higher adsorption capacity, compared to PPy-G (dye removal fraction 99.6% and 89.1%, respectively, after 23 h). Therefore, the prepared PPy-G-BaFe aerogels are attractive adsorbents for water purification due to their enhanced adsorption performance and the possibility of facilitated separation from solution by a magnetic field.

Preparation of Copper Ion Adsorbed Modified Montmorillonite/Cellulose Acetate Porous Composite Fiber Membrane by Centrifugal Spinning

The natural adsorption material montmorillonite (MMT) was selected, and cellulose acetate (CA) was used as the loading substrate to design and prepare a kind of green and environment-friendly recyclable porous composite fiber membrane with good heavy metal ion adsorption performance. Acetic acid modified montmorillonite (HCl-MMT), sodium dodecyl sulfonate modified montmorillonite (SDS-MMT), and chitosan modified montmorillonite (CTS-MMT) were prepared by inorganic modification and organic modification, and the porous MMT/CA composite fiber membrane was constructed by centrifugal spinning equipment. The morphological and structural changes of MMT before and after modification and their effects on porous composite fiber membranes were investigated. The morphology, structure, and adsorption properties of the composite fibers were characterized by scanning electron microscopy (SEM) and atomic absorption spectrometry (ASS). The experimental results showed that the maximum adsorption capacity of Cu²⁺ on the prepared 5 wt% CTS-MMT composite fiber membrane was 60.272 mg/g after 10 h static adsorption. The adsorption of Cu²⁺ by a porous composite fiber membrane conforms to the quasi-second-order kinetic model and Langmuir isothermal adsorption model. The main factor of the Cu²⁺ adsorption rate is chemical adsorption, and the adsorption mechanism is mainly monolayer adsorption.

Comparative Study of Octavinyl Oligomeric Sesquisiloxane Nanomaterial-Modified Asphalt Using Molecular Dynamics Method

This paper mainly studies the compatibility and properties of octavinyl oligomeric silsesquioxane nanomaterial (nano-OvPOSS)-modified asphalt, in comparison with those of traditional zinc oxide nanomaterial (nano-ZnO) and silica nanomaterial (nano-SiO2), through the method of molecular dynamics simulation. Nano-OvPOSS, an organic–inorganic nano-hybrid material, is studied for the first time in the application of asphalt modification. By studying different sizes and types of nanomaterials, this paper elucidates the superiority of nano-OvPOSS as an asphalt modifier owing to the unique microstructure of eight organic groups of its inorganic framework. According to the results, nano-OvPOSS does not aggregate in the modified asphalt system and displays the best compatibility with asphalt when compared with nano-SiO2 and nano-ZnO. Moreover, nano-OvPOSS exhibits the most favorable compatibility with resinous oil out of the four asphalt components. The size of nano-OvPOSS determines its compatibility with asphalt. The smaller the particle size of nano-OvPOSS, the better its compatibility with asphalt. Therefore, out of all the four sizes of nano-OvPOSS (4.4 Å, 7 Å, 10 Å, and 20 Å) adopted in this study, the 4.4 Å nano-OvPOSS exhibits the best compatibility with asphalt. Additionally, compared with nano-SiO2 and nano-ZnO, nano-OvPOSS is capable of attracting more asphalt molecules around it so that it reduces the largest amount of ratio of free volume (RFV) of matrix asphalt, which can be reduced by 9.4%. Besides these characteristics, the addition of nano-OvPOSS into the matrix asphalt contributes to higher heat capacity, bulk modulus, and shear modulus of the asphalt system, which were increased by 14.3%, 74.7%, and 80.2%, respectively, thereby guaranteeing a more desirable temperature stability and deformation resistance in the asphalt system. Accordingly, nano-OvPOSS can be employed as a viable asphalt modifier to ensure a well-rounded performance of modified asphalt.

Study on the Influence of Nano-OvPOSS on the Compatibility, Molecular Structure, and Properties of SBS Modified Asphalt by Molecular Dynamics Simulation

The present research is carried out to inspect the influence of nano-OvPOSS (octavinyl oligomeric silsesquioxane) with different particle sizes on styrene-butadiene-styrene (SBS) modified asphalt through the method of molecular dynamics simulation. This nanomaterial is investigated for the first time to be used in asphalt modification. With the construction of modified asphalt simulation models and the analysis of their mixing energy, radius of gyration (R_g), radial distribution function (RDF), ratio of free volume (RFV), heat capacity, bulk modulus, and shear modulus, this study elucidates the influence of nano-OvPOSS on the compatibility between SBS and asphalt, on the structure of SBS as well as that of asphalt molecules and on the temperature stability and mechanical properties of SBS modified asphalt. The results show that nano-OvPOSS not only is compatible with SBS as well as with asphalt, but also is able to improve the compatibility between SBS and asphalt. Nano-OvPOSS is able to reinforce the tractility of branched chains of SBS and make SBS easier to wrap the surrounding asphalt molecules. The free movement space of molecules in the SBS modified asphalt system also shrinks. Moreover, the addition of nano-OvPOSS into SBS modified asphalt results in higher heat capacity, bulk modulus, and shear modulus of modified asphalt. All of these effects contribute to a more stable colloidal structure as well as more desirable temperature stability and deformation resistance of the modified asphalt system. The overall results of the study show that nano-OvPOSS can be used as a viable modifier to better the performance of conventional SBS modified asphalt.

Recent Advances in Adsorptive Nanocomposite Membranes for Heavy Metals Ion Removal from Contaminated Water: A Comprehensive Review

Water contamination is one of the most urgent concerns confronting the world today. Heavy metal poisoning of aquatic systems has piqued the interest of various researchers due to the high toxicity and carcinogenic consequences it has on living organisms. Due to their exceptional attributes such as strong reactivity, huge surface area, and outstanding mechanical properties, nanomaterials are being produced and employed in water treatment. In this review, recent advances in the use of nanomaterials in nanoadsorptive membrane systems for wastewater treatment and heavy metal removal are extensively discussed. These materials include carbon-based nanostructures, metal nanoparticles, metal oxide nanoparticles, nanocomposites, and layered double hydroxide-based compounds. Furthermore, the relevant properties of the nanostructures and the implications on their performance for water treatment and contamination removal are highlighted. The hydrophilicity, pore size, skin thickness, porosity, and surface roughness of these nanostructures can help the water permeability of the nanoadsorptive membrane. Other properties such as surface charge modification and mechanical strength can improve the metal adsorption effectiveness of nanoadsorptive membranes during wastewater treatment. Various nanocomposite membrane fabrication techniques are also reviewed. This study is important because it gives important information on the roles of nanomaterials and nanostructures in heavy metal removal and wastewater treatment.

Gum Hydrocolloids Reinforced Silver Nanoparticle Sponge for Catalytic Degradation of Water Pollutants

The accumulation of organic contaminants including dyes in aquatic systems is of significant environmental concern, necessitating the development of affordable and sustainable materials for the treatment/elimination of these hazardous pollutants. Here, a green synthesis strategy has been used to develop a self-assembled gum kondagogu-sodium alginate bioconjugate sponge adorned with silver nanoparticles, for the first time. The properties of the nanocomposite sponge were then analyzed using FTIR, TGA, SEM, and MicroCT. The ensued biobased sponge exhibited hierarchical microstructure, open cellular pores, good shape memory, and mechanical properties. It merges the attributes of an open cellular porous structure with metal nanoparticles and are envisaged to be deployed as a sustainable catalytic system for reducing contaminants in the aqueous environment. This nanocomposite sponge showed enhanced catalytic effectiveness (k_m values up to 37 min⁻¹ g⁻¹ and 44 min⁻¹ g⁻¹ for methylene blue and 4-nitrophenol, respectively), antibacterial properties, reusability, and biodegradability (65% biodegradation in 28 days).