Materials For Water Purification Research Articles

Enhanced catalytic ozonation towards oxalic acid degradation over novel copper doped manganese oxide octahedral molecular sieves nanorods.

A series of copper doped manganese oxide octahedral molecular sieves (Cu-OMSx-T) with different Cu/Mn ratios and hydrothermal temperatures were successfully synthesized and used for catalytic ozonation towards oxalic acid (OA) degradation. The as-prepared Cu-OMSx-T composites were comprehensively investigated by BET, FT-IR, XPS and etc. characterizations. The results indicated that the Cu doping would increase the specific surface area, change chemical bonds, and promote the transformation of multivalent metals and the generation of oxygen vacancies. It was noteworthy that the hydrothermal temperature played an important role in the morphology of Cu-OMSx-T composites and the Cu/Mn molar ratios greatly influenced the catalytic activities. Amongst, the Cu-OMS0.5-140 achieved the optimum catalytic activity with 97.3% of OA degradation efficiency and 98.8% of mineralization rate in 30 min at pH 6.0. Moreover, hydroxyl radical and superoxide radical were identified as the major reactive radicals and the catalytic mechanism for OA degradation enhancement was also elucidated. In addition, the Cu-OMS0.5-140 exhibited great stability and reusability with high OA mineralization rate (>90%) and low metal release after five times recycle. Overall, the results indicated that the synthesized Cu-OMS0.5-140 is an efficient, stable, and recyclable ozonation catalyst, and could be a promising alternative material for water purification.

Development of modernized paper filtering materials for water purification, assessment of their properties

Filtering paper materials (FPM), which are easy to recycle, are widely applied to water purification. The main disadvantage of the absolute majority of filtering materials, including paper, is their tendency to biofouling. This drawback considerably limits or even sometimes makes it impossible to use filtering materials and/or sorbents in a certain medium. In connection with the above, the object of our study was the process of water purification using the FPM with disinfecting properties based on modified cellulose fibers and natural sorbent palygorskite, which can adsorb mechanical impurities, heavy metal ions, entero-viruses, and bacteria.It was found that the samples of modified filtering paper materials with the highest density and lowest thickness and the samples with the lowest density and the highest thickness have higher filtration and sorption capacity compared to samples with the mean values of these technological characteristics.Swelling of cellulose fibers reduces the impact of the compositional structure of the studied FPM samples on their filtering capability and increases the impact of the compositional structure on the sorption ability of these FPM.It was established that the samples with the introduction of about 40 % phosphoric ester of cellulose into their composition have the best technological characteristics.The character of dependence of the rate of filtration process on consumption of purified water, thickness, density and composition of FPM was established. The obtained mathematical models are presented by second-order polynomial and make it possible to take into consideration not only technical specifications, but also the impact of the FPM composition on the rate of filtration process of purified water. Among the studied parameters, the content of sulfate viscose or sulfate bleached viscose in paper-forming mass of the studied samples and consumption of the purified water have the highest impact on the rate of the filtration process at constant pressure and contamination concentration. The proposed mathematical models also allow to determine the necessary compositional structure for obtaining FPM with determined properties

T4,4,4-graphyne: A 2D carbon allotrope with an intrinsic direct bandgap

A novel two-dimensional (2D) structurally stable carbon allotrope is proposed using first-principles calculations, which is a promising material for water purification and for electronic devices due to its unique porous structure and electronic properties. Rectangular and hexagonal rings are connected with acetylenic linkages, forming a nanoporous structure with a pore size of 6.41 Å, which is known as T4,4,4-graphyne. This 2D sheet exhibits a direct bandgap of 0.63 eV at the M point, which originates from the pz atomic orbitals of carbon atoms as confirmed by a tight-binding model. Importantly, T4,4,4-graphyne is found to be energetically more preferable than the experimentally realized β-graphdiyne, it is dynamically stable and can withstand temperatures up to 1500 K.

Potential of a Nigerian biotite-rich kaolinite ore to industrial alumina by hydrometallurgical process

Increasing demands for aluminium and aluminium oxide with diverse industrial applications have prompted the development of a low-cost and eco-friendly technique as a substitute for conventional ore treatments by reduction-roasting route, requiring high energy consumption. For example, the demand for high-grade industrial alumina (Al2O3) as valuable materials in refractories, pigments, adsorbents, catalysis, water purification, aluminium production and metallurgical applications cannot be over emphasized. Thus, the upgrading of a Nigerian biotite-rich kaolinite ore containing admixture of kaolinite (Al2.00Si2.00O9.00: 96-900-9231), biotite (Mg6.55Fe3.46Al5.29Ti1.34Si11.36K4.00O48.00: 96-900-0844) and quartz (Si3.00O6.00: 96-900-9667) impurities by hydrometallurgical route was investigated in phosphoric acid media. During leaching, parameters such as leachant concentration, particle size and reaction temperature on the extent of ore dissolution were accordingly examined. At optimal leaching conditions (2.0 mol/L H3PO4, 75 °C), 87.0% of the initial 10 g/L ore reacted within 120 min. The activation energy of 16.6 kJ/mol supported the diffusion control reaction mechanism. The unreacted product (∼13.0%) analyzed by XRD was found to contain siliceous impurities including iron silicate and manganese silicate which could serve as valuable by-products for some defined industries. The leach liquor at optimal leaching conditions was accordingly treated to obtain pure aluminium solution which was further beneficiated to obtain high-grade alumina (α-Al2O3) of industrial value with 96.3% purity.

WASTE-FREE TECHNOLOGY OF CHLORELLA SOROKINIANA MICROALGAE BIOMASS USAGE FOR LIPIDS AND SORBENTS PRODUCTION

In the present article we introduce application areas of Сhlorella sorokiniana microalgae biomass for national economy (feed and biologically active additives, etc). Here it is shown that thermal and chemical modification of plant material waste might result in obtaining of highly-efficient materials for water purification. Major stages of waste-free technology of microalga processing with further extraction of valuable lipids and obtaining of sorption materials are schematically shown. We have determined fatty-acid content of lipid fraction (77 mg/g), obtained by Soxhlet method from lyophilized microalga biomass. It was revealed, that it includes 83.7% of unsaturated fatty acids (generally, С18:1, С18:2, С18:3), whereas saturated fatty acids are mostly presented by С16 – С20 family. In lyophilized biomass we discovered α-linolenoic acid (Omega-3, 28.3%), which is one of the most valuable biologically active compounds, required for full-value human life and activities. Microstructure analysis of residual biomass of C. sorokiniana microalgae has shown pore surface, formed by destroyed cells. In the course of studying the sorption properties of residual biomass with the use of initial and final concentration parameters, the efficiency of purification of model water from Fe3+ ions (47.5%) was evaluated, which indicates the need to modify the sorption properties of biomass. It has been established that the degree of wastewater purification containing iron (III) compounds can be significantly increased (by 1.8 times) by forming from the residual biomass granular materials with additional introduction of chitosan in the composition, which using as a binder and a modifying additive (mass ratio 4:1).

Fabrication and characterization of amphiphilic magnetic water purification materials for efficient PPCPs removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants that have gained increasing attention in recent years. Conventional adsorption materials exhibit poor efficiency in removing PPCPs. In this regard, a series of magnetic particles (Nanda Amphiphilic Materials, NDAMs) was fabricated and characterized in this study. These materials were prepared by special polymerization with different monomer proportions [N-vinyl-2-pyrrolidone (NVP)/divinylbenzene, (DVB)]. Characterization results indicated that NDAM-40 (n(NVP):n(DVB), 6:4) was the most effective and possessed the largest BET surface area (650 m2/g) among the nine prepared NDMAs. NDAM-40 also possessed the highest nitrogen content (1.13%) and the smallest contact angle (71.5°). Seventeen representative PPCPs were chosen to investigate the adsorption performance of NDAM-40. Norit, a commercial activated carbon, was used for comparison. NDAM-40 exhibited faster adsorption rate than Norit. For most PPCPs, the pseudo-second-order rate constants of NDAM-40 were more than five times higher than those of Norit. The amounts (Qe) of most PPCPs adsorbed on NDAM-40 were two to five times higher than those on Norit. NDAM-40 was applicable to water purification because of its definite advantages in terms of removal efficiency and recyclability. The removal efficiency of 17 PPCPs exceeded 80% when using NDAM-40, and only 20%–70% when using Norit.

Applications of polystyrene/graphite composites in water purification as a semiconductor visible-light photocatalyst for organic pollutant degradation

The aim of this study was to prepare a polymer/graphite composite thin film as a cheap, and nontoxic photocatalyst that could be activated by visible light. It was characterized using ultraviolet/visible spectrophotometry and X-ray diffraction. Scanning electron microscopy was used to examine the photocatalyst surface before and after a photodegradation process. The photocatalyst showed activity under visible light and was used for the photodegradation of methylene blue (MB) and rhodamine B (Rh-B) as target pollutants. The process was studied with different pH values, initial dye concentrations, and light intensities from the radiation source to evaluate their effects. The results revealed that the photodegradation was affected by the initial dye concentration, and also showed that the best conditions for the photodegradation reactions of both dyes were an alkaline medium and a light intensity of 80 wt. The films prepared under the conditions reported herein could be promising materials in water purification.

Water Is a Cagey Liquid.

Liquid water is considered poorly understood. How are water's physical properties encoded in its molecular structure? We introduce a statistical mechanical model (CageWater) of water's hydrogen-bonding (HB) and Lennard-Jones (LJ) interactions. It predicts the energetic and volumetric and anomalous properties accurately. Yet, because the model is analytical, it is essentially instantaneous to compute. This model advances our understanding beyond current molecular simulations and experiments. Water has long been regarded as a "2-density liquid": a dense LJ liquid and a looser HB one. Instead, we find here a different antagonism underlying water structure-property relations: HBs in water-water pairs drive density, while HBs in cooperative cages drive openness. The balance shifts strongly with temperature and pressure. This model interprets the molecular structures underlying the liquid-liquid phase transition in supercooled water. It may have value in geophysics, biomolecular modeling, and engineering of materials for water purification and green chemistry.

Novel 2D Nanosheets with Potential Applications in Heavy Metal Purification: A Review

AbstractOver the past decades, extensive studies have been carried out for the design of advanced materials for water purification. Heavy metal pollution in water is a serious global environmental problem due to their toxicity and carcinogenicity. With the discovery of graphene, novel 2D nanosheets, derived from the wide variety of traditional materials, have emerged as some of the most promising candidates for heavy metal purification. This review summarizes the recent progress on the novel 2D nanosheets with their applications in heavy metal purification. First, the authors introduce the unique advances on 2D nanomaterials, followed by the description of their composition and crystal structures. Some novel 2D nanosheets with great success in heavy metal purification field are then summarized, including insights on their advantages over traditional materials and limitations in practical applications, along with some advances in interfacial structure modifications for future work. The functional design of more and more novel 2D interfacial materials with unique properties is still demanding for future industrial applications.

Electrospinning of PAN and composite PAN-GO nanofibres

Purpose: The aim of this study was to present the influence of used reinforcement phase – graphene oxide (GO) and the electrospinning process parameters (the distance between the nozzle and collector) on the morphology and the structure of the obtained composite PAN-GO nanofibres. Design/methodology/approach: To produce pure polymer nanofibers, a 10% (wt.) electrospinning solution the polyacrylonitrile (PAN) was dissolved in N, N-dimethylformamide (DMF). The spinning solution used for electrospinning PAN-GO composite fibres was made by dissolving the PAN in a mixture of GO and DMF. By changing the configuration of the distance between the nozzle and collector (10 and 20 cm) and maintaining the remaining parameters (solution flow rate and potential difference between the electrodes), four samples in the form of nanofibrous mats were made. In order to identify the structure and morphology of the reinforcing phase, X-ray microanalysis (EDX) and scanning electron microscopy (SEM) were performed. In addition, the structure of graphene oxide microparticles was investigated by a Raman spectrometer. In order to determine the influence of the distance between the nozzle and the collector used in the electrospinning process and the addition of the reinforcing phase to the morphology and structure of the obtained PAN polymer nanofibres and PAN-GO composite nanofibres, they were examined using SEM. The analysis of the chemical composition of PAN and PAN-GO fibres was carried out using X-ray microanalysis. Findings: The morphology and structure analysis indicated that polymer nanofibres PAN for both the distances between the nozzle and the collector show no structural defects and presented same diameter over the entire length of the fibre. Nanofibres with the addition of GO obtained at both distances between the electrodes, showed defects in the form of beads. In addition, it was observed that with increasing distance between the nozzle and collector the diameter of obtained nanofibres is smaller for both pure PAN and composite PAN-GO samples. Research limitations/implications: The paper is the basis for further research in the field of the use of PAN-GO composite nanofibres as water purification materials. Originality/value: The electrospinning method can be an alternative to conventional methods for the production of filtering membranes due to the ease of carrying out the process and the fact that a material with a high specific surface area is obtained.

Novel composite materials as P-adsorption agents and their potential application as fertilizers

<p>The main objective of this study is to review the role of phosphorus in fertilizers, emphasizing in phosphate rock which is the primary source for phosphate fertilizer, with reference to harmful heavy metals as a consequence of their use. Simultaneously, this study examined the use of P-Adsorption agents as a potential application in agriculture, as the adsorbed phosphorus can be used as fertilizer or enriching soil conditioners. Therefore, it is generated a sustainable cycle taking into account a renewable resource-based Phosphorus Adsorption Agent (P-AA) leading to environmental protection and conservation of natural resources. Finally, this study highlighted new aspects that support P bioavailability of Humic-metal-P (HMP) in soils, correlating with novel materials in water purification.</p>

Drum Stick Seed Powder as Smart Material for Water Purification: Role of Moringa oleifera Coagulant Protein-Coated Copper Phosphate Nanoflowers for the Removal of Heavy Toxic Metal Ions and Oxidative Degradation of Dyes from Water

Seed powder of vegetable drum stick (Moringa oleifera) is a household known material for the coagulation of impurities from water. We find from our lab experiments that this material indeed removes toxic inorganic heavy metal ions and organic dyes; however, the latter can be degraded in the presence of H2O2 under Cu2+ as catalyst. To understand the details of the treatment of water that is taking place by this seed powder, a simple inorganic–protein nanoflower system was developed using copper phosphate (CuP), and a low molecular weight, cationic, and coagulant protein of Moringa oleifera (MOCP), to result in the nanoflowers (NFs), CuPNF_MOCP. The CuPNF_MOCPs were synthesized at different ratios of inorganic versus protein components and characterized by spectroscopy and microscopy techniques. Both the time- and the protein concentration-dependent flower growth showed complete flower morphology within 24 h with tightly packed petals having smooth surface upon increasing the protein concentration as notice...

Hybrid Adsorbent Materials Obtained by the Combination of Poly(ethylene-alt-maleic anhydride) with Lignin and Lignosulfonate

Lignin is one of the most available biomass products, but its potential for the development of functional materials has yet to be unleashed. Here, the modification of lignin and lignosulfonate with poly(ethylene-alt-maleic anhydride) [P(E-alt-MA)], a functional polymer of wide industrial use, is accomplished by means of a simple esterification reaction. As a result, hybrid adsorbent materials for water purification can be obtained, which were thoroughly characterized. The combination of P(E-alt-MA) with lignin increased hydrophilicity of the latter, making it dispersible in aqueous environments, while with lignosulfonate it gave rise to a water-insoluble, thus easily recoverable, product. The adsorption properties of the resulting products have been tested against a model water pollutant (methylene blue), demonstrating remarkable adsorption speed (in the order of minutes), adsorption efficiency and stability over a wide range of pH (2–12). Moreover, after the incorporation of magnetite nanoparticles by in situ synthesis, adsorbent materials able to be magnetically recovered were developed.

Covalently cross-linked graphene oxide aerogel with stable structure for high-efficiency water purification

Porous graphene-based aerogels (GAs) hold great promise for water purification due to their fascinating properties. However, weak connections between the graphene oxide nanosheets cause instability and incompressibility in GAs during practical applications. Herein, the small organic molecule of cysteamine was selected as a covalent cross-linker to fabricate GAs through a facile one-step synthesis method. The porosity and mechanical stability of GAs were simultaneously improved due to strong covalent cross-linking between the graphene oxide nanosheets via cysteamine as the linkage. The resultant graphene/cysteamine aerogels (GCAs) were compressible with excellent structural stability under different acid, base, and organic solution conditions. The maximum oil absorption capacity of the GCAs reached as high as 251 g/g and did not obviously decrease even after regeneration by squeezing. In addition, the GCAs exhibited a high adsorption capacity for common dyes, such as methylene blue (207.8 mg/g) and methyl orange (70.2 mg/g). As expected, the as-prepared aerogels with high adsorption capacities, structural stability and excellent compressibility, have great potential as recyclable and durable materials for water purification.

Impact of Phosphate Adsorption on Complex Cobalt Oxide Nanoparticle Dispersibility in Aqueous Media.

A commonly overlooked and largely unknown aspect of assessing the environmental and biological safety of engineered nanomaterials is their transformation in aqueous systems. Complex metal oxides are an important class of materials for catalysis, energy storage, and water purification. However, the potential impact of nano complex metal oxides on the environment upon improper disposal is not well understood. We present a comprehensive analysis of the interaction of an environmentally relevant oxyanion, phosphate, with a complex metal oxide nanomaterial, lithium cobalt oxide. Our results show that adsorption of phosphate to the surface of these materials drastically impacts their surface charge, rendering them more stable in aqueous systems. The adsorbed phosphate remains on the surface over significant periods of time, suggesting that desorption is not kinetically favored. The implications of this interaction may be increased dispersibility and bioavailability of these materials in environmental water systems.

Nigella sativa plant based nanocomposite-MnFe2O4/BC: An antibacterial material for water purification

It is a challenge for the current world to provide chemical pollutants and microbes free affordable water. Clean water can be made available to common people by protecting the water sources, and purifying the polluted water. Carbon-based materials can be prepared and utilized for the remediation of water pollutants and microbes. The present study reveals the advancement in water treatment technology which includes the development of economic, eco-friendly, and phytogenic nanohybrid composite, MnFe2O4/BC. This composite inhibited the bacterial growth and adsorbed organic water pollutants. The hybrid composite was prepared by growing MnFe2O4 onto the Nigella Sativa plant seeds (Black Cumin) using simple co-precipitation process. The composite was characterized by FT-IR, XRD, SEM-EDX, TEM, TGA, and DSC techniques. MnFe2O4/BC has shown Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) growth inhibition activity. The hybrid composite was used as an adsorbent for methylene blue removal from water with an excellent adsorption capacity and can be used in cyclic manner. This composite, therefore, is affordable and sustainable adsorbent that can be used for water purification for the current and future scenario.

Thermoresponsive Amphoteric Metal-Organic Frameworks for Efficient and Reversible Adsorption of Multiple Salts from Water.

Regenerable, high-efficiency salt sorption materials are highly desirable for water treatment. Here, a thermoresponsive, amphoteric metal-organic framework (MOF) material is reported that can adsorb multiple salts from saline water at room temperature and effectively release the adsorbed salts into water at elevated temperature (e.g., 80 °C). The amphoteric MOF, integrated with both cation-binding carboxylic groups and anion-binding tertiary amine groups, is synthesized by introducing a polymer with tertiary amine groups into the cavities of a water-stable MOF such as MIL-121 with carboxylic groups inside its frameworks. The amphoterized MIL-121 exhibits excellent salt adsorption properties, showing stable adsorption-desorption cycling performances and high LiCl, NaCl, MgCl2 , and CaCl2 adsorption capacities of 0.56, 0.92, 0.25, and 0.39 mmol g-1 , respectively. This work provides a novel, effective strategy for synthesizing new-generation, environmental-friendly, and responsive salt adsorption materials for efficient water desalination and purification.

Tea Polyphenols Functionalized and Reduced Graphene Oxide-ZnO Composites for Selective Pb2+ Removal and Enhanced Antibacterial Activity.

New materials with good purification of water quality (heavy metal ions removal and inhibition of bacteria) have increasingly attracted more research attentions. Considering the advantages of zinc oxide (ZnO) and tea polyphenol functionalized and reduced graphene oxide (TPG), the TPG-ZnO composites were prepared under moderate hydrothermal method and characterized by various methods. Lead ions (Pb2+) and Streptococcus mutans (S. mutans) were used to evaluate the adsorption capacity and antimicrobial activity of the TPG-ZnO, respectively. The influencing factors for heavy metal ions removal (pH, contact time), adsorption kinetics, and isotherms were discussed in this article. Furthermore, their antibacterial properties against S. mutans were investigated by counting of colony-forming units (CFU), scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM). Results showed that the novel TPG-ZnO composites presented higher adsorption efficiency for Pb2+ (98.92%) compared with pure ZnO and enhanced antibacterial activity effects (99.99%) towards S. mutans, compared with pure ZnO and TPG (P < 0.05). The TPG-ZnO composites are therefore promising water purification materials for application in high-efficient removal of heavy metal ions and inhibition of bacterial growth.

Efficient Adsorption Characteristics of Pristine and Silver-Doped Graphene Oxide Towards Contaminants: A Potential Membrane Material for Water Purification?

In this work, we have investigated the potential of pristine and silver (Ag)-functionalized graphene oxide monolayers GO (GO-Ag) as efficient membranes for water filtration. Our first principles calculations based on density functional theory (DFT) reveal the hydrophilic nature of GO surfaces. The phonon frequency calculations within density functional perturbation theory (DFPT) confirmed the stability of GO sheets in aqueous media. Van der Waals-corrected binding energies of GO sheet towards heavy metals suggest that even pristine GO sheets are completely impermeable to various heavy metals like arsenic (As) and lead (Pb). However, compared to GO, the GO-Ag sheets have a much higher affinity towards the three amino acids histidine, phenyl-alanine and tyrosine, which are the main component of a bacteria cell wall. The GO-Ag sheet is found to be extremely efficient for bacteria inactivation.

Dynamics of a Water Nanodrop through a Holey Graphene Matrix: Role of Surface Functionalization, Capillarity, and Applied Forcing

Nanoporous graphene has emerged as an excellent material for desalination and water purification. Holey graphene (HG) is a special form of nanoporous graphene, where multilayers of nanoporous graphene get arranged in spatially separated stacks. In this paper, we employ molecular dynamics simulations to unravel the dynamics of a water drop in presence of an applied force F in such holey graphene architecture, which is characterized by the presence of either hydrophilic functionalization (HIF) or hydrophobic functionalization (HOF) of the edges of the holes. For realistic values of F, the consideration of water drop makes the capillary effects important, which in turn interplays with the wettability of the surface functionalization to ensure that the HG with the HOF causes both an enhanced flux and an enhanced permeated water volume. We relate these phenomena to the augmented water-hydrophilic-edge attraction that arrests the dewetting of water from the graphene stacks and slows the speed of water flowing p...