Ion Exchange Treatment Research Articles

Ion-exchange enhancement of borosilicate glass vials for pharmaceutical packaging

Pharmaceutical containers for parenteral use, including vials, ampoules, prefilled syringes, and cartridges, are traditionally made of glass. However, the most commonly used type, borosilicate glass, is susceptible to issues such as breakage, corrosion, and delamination, which can jeopardize the safety and efficacy of the enclosed drugs. To address these concerns without compromising the visual or qualitative aspects of borosilicate medical glass vials, this study aimed at the enhancement of their mechanical, chemical, and corrosion resistance. A single ion exchange treatment (IET) in a salt bath of molten KNO3 at temperatures of 400, 450, and 500 °C for 2, 12, and 24 h was applied. The effects of the ion exchange process performed under different conditions were assessed by measuring Vickers hardness, crushing load, and chemical durability. The mechanical load required to crush full-body vials after the ion exchange process at 500 °C for 2, 12, and 24 h showed an increase in the applied force values (1650 ± 80, 2340 ± 80, and 2325 ± 40 N) compared to untreated vials (1157 ± 20 N).No radial cracks were observed on the surface of treated glass vials after indentation, indicating the presence of compressive stresses that prevented the initiation and propagation of cracks. The EDS analysis confirmed an increase in potassium concentration and a decrease in sodium content near the surface of samples modified by ion exchange treatment. The treated samples showed appropriate chemical stability in different acidic, basic, and neutral solutions. Conspicuous changes are noticed in the Raman spectra after IET, specifically in the Qn species region. The results indicate the potential of the ion exchange treatment in enhancing the properties of borosilicate glass vials by relatively simple and easily scalable techniques.

Direct filtration of low-turbidity water by fixed-bed ion exchange treatment

In drinking water treatment, low-turbidity water (e.g., < 5 NTU) is often purified by direct filtration comprising coagulation, flocculation, and rapid sand filtration. This study assessed the potential of replacing the rapid sand filter with a fixed-bed ion exchange column. Two types of anion exchange resins, polyacrylic (Purolite A860) and polystyrene (Purolite A502PS), were used in fixed-bed columns without preceding coagulation and flocculation. After the first use of the new resins (14-h operation), the A860 column showed more significant head loss buildup than the A502PS column (151 and 101 cm, respectively). This can be attributed to the effective size of A860 resins (0.38 mm), which was smaller than that of A502PS resins (0.52 mm). A860 resins were superior to A502PS resins in filtrate quality. The A860 resins achieved filtrate turbidity (0.16–0.26 NTU) lower than the A502PS resins (0.19–0.35 NTU). Similarly, dissolved organic carbon removal by A860 resins (25–37 %) was higher than that by A502PS resin (15–25 %) due to the low hydrophobicity of the feed water. Air scouring and water backwashing were ineffective in regenerating A860 resins. In contrast, cleaning with a NaCl solution (pH = 12) partially recovered the capacity of A860 resins for turbidity removal.

A Scientometric analysis and bibliometric review of IOEX as a treatment to remove pollutants

Pollutants in water bodies pose a serious threat to both the aquatic ecosystem and human health. Ion exchange is used as a chemical process to remove unwanted dissolved ions from water and wastewater. It is widely accepted in developing countries. This analysis provides a bibliometric examination to consider the status and trends of advanced ion exchange worldwide. This study was conducted using the Dimensions website to identify and collect the most important research papers. The retrieved manuscripts were organized through Microsoft Excel and then VOS viewer was used to analyze the data by reviewing previous studies related to ion exchange as a contaminant removal treatment. To create maps and find out which countries, universities, and journals have published research articles on topics related to ion exchange, as well as authors who have studied the topic of ion exchange and their research, cooperation. To benefit from these studies and learn the importance of ion exchange as a treatment for removing pollutants. The electro neutrality of the ion exchange (IOEX) process must always be maintained because it is a stoichiometric process. Search results for IOEX were exported from Dimensions to a CSV file, both coexistence, cooperation with affiliate countries and consortia were implemented on the full search results. Ion exchange treatment has proven effective in treating industrial wastewater and domestic wastewater. Professionals and practitioners in the field are provided with important information through this examination of ion exchange research. The analysts learned about leading academic and research institutions, the state of the exploration field, and the most controversial issues surrounding advanced ion exchange. In addition, this lesson will provide the opportunity to learn basic facts that will develop the extent of ion exchange knowledge. The bibliometric survey method can also be used to visualize the trend of research and study in various fields.

Hollow CuCo-based trimetallic oxides derived from ZIF-67 as enhanced electrocatalysts for OER

Multimetallic oxide configuration and hollow structure construction are effective strategies for the design of efficient electrocatalysts, which can regulate the intrinsic properties of the active sites, enlarge the specific surface areas and expose more active sites. In this work, hollow-structured CuCo-based ternary metal oxides supported nitrogen-carbon networks (HS-CuMCoOx, M = Fe/Zn/Ni) derived from ZIF-67 hollow spheres were fabricated through facile ion exchange and heat treatment. The prepared composites possess hollow configurations with homogeneously dispersed trimetallic active species on the shells. Among all the ternary metallic derivatives, hollow spheres supporting Cu, Fe, and Co oxides (HS-CuFeCoOx) exhibited highest electrocatalytic activity towards oxygen evolution reaction (OER). The improved OER performance ascribed to the inherent electrocatalytic properties of the ternary metal active species and microstructure by hollow structure design and heat treatment, which offered an effective synthetic strategy for the fabrication of trimetallic oxide composites for as OER electrocatalysts.

Chitosan/Graphene oxide/SiO2 Nanoadsorbents for the Removal of Cr(VI) from Wastewaters

The swift industrialization and urbanisation have led to the discharge of significant amounts of hazardous heavy metals into water environments. Heavy metal pollution is currently one of the most significant environmental challenges being addressed, attracting researchers due to its biotoxicity, and non-biodegradability even at minimal concentrations [1]. Chromium (Cr) is among the most prevalent heavy metal contaminants. Its oxidation state, Cr(VI), harms the environment yet has catastrophic consequences for human health [2]. It is removed by physical and chemical procedures such as ion exchange, chemical precipitation and electrochemical treatment. Yet, most of these procedures have downsides, such as the formation of hazardous sludge, causing disposal issues and the need for costly tools and monitoring systems [3]. Adsorption is regarded an appealing and favourable technology because to its ease of design, simplicity, and high efficiency. Carbon-based nanomaterials have been investigated as superior adsorbents in aqueous solutions for the separation of organic and inorganic contaminants. The current study recommends the usage of adsorbents based on graphene oxide (GO). GO is an oxygen-rich material that is produced during the oxidation of graphite. It features hydrophobic areas due to aromatic groups in the nanosheets' centres, along with a large number of hydrophilic functional groups such as hydroxy, aldehyde, epoxy, and carboxyl groups [4]. The latter allow GO to swell and perform electrostatic functions. Chitosan (Cs) is a great adsorbent since it is inexpensive, is biocompatible, and causes no secondary pollution. Its molecular chains include -NH2 and -OH groups, which can interact with heavy metal ions and give significant adsorption capacity [5]. Silicon dioxide (SiO2) nanoparticles with graphene oxide have better physical and chemical characteristics than graphene oxide-like surface area. Similar research has revealed that the presence of SiO2 increases the adsorbent's adsorption capacity for Cr(VI) [6]. The effect of the pH value, contact time and initial chromium concentration was examined in order to determine the feasibility of Cs/GO@SiO2. Its structure and the morphology were studied in detail by the application of BET, XRD, FTIR and SEM techniques. According to the results, the modification of Cs with GO@SiO2 enhanced the percentage removal of chromium ions, especially, in acidic conditions by using 0.5 g/L of the adsorbent. Experimental data of equilibrium were used to calculate adsorption isotherms. According to thermodynamics the spontaneous nature of their adsorption was confirmed. Overall, the results indicate that Cs/GO@SiO2 can be effectively employed for removal of chromium from aqueous solutions.

Potential strategies for phytoremediation of heavy metals from wastewater with circular bioeconomy approach.

Water pollution is an inextricable problem that stems from natural and human-related factors. Unfortunately, with rapid industrialization, the problem has escalated to alarming levels. The pollutants that contribute to water pollution include heavy metals (HMs), chemicals, pesticides, pharmaceuticals, and other industrial byproducts. Numerous methods are used for treating HMs in wastewater, like ion exchange, membrane filtration, chemical precipitation, adsorption, and electrochemical treatment. But the remediation through the plant, i.e., phytoremediation is the most sustainable approach to remove the contaminants from wastewater. Aquatic plants illustrate the capacity to absorb excess pollutants including organic and inorganic compounds, HMs, and pharmaceutical residues present in agricultural, residential, and industrial discharges. The extensive exploitation of these hyperaccumulator plants can be attributed to their abundance, invasive mechanisms, potential for bioaccumulation, and biomass production. Post-phytoremediation, plant biomass can be toxic to both water bodies and soil. Therefore, the circular bioeconomy approach can be applied to reuse and repurpose the toxic plant biomass into different circular bioeconomy byproducts such as biochar, biogas, bioethanol, and biodiesel is essential. In this regard, the current review highlights the potential strategies for the phytoremediation of HMs in wastewater and various strategies to efficiently reuse metal-enriched biomass material and produce commercially valuable products. The implementation of circular bioeconomy practices can help overcome significant obstacles and build a new platform for an eco-friendlier lifestyle.

A New Strategy for a Separate Manufacture of Arabinooligosaccharides and Oligogalacturonides by Hydrothermal Treatment of Sugar Beet Pulp

Sugar beet pulp (SBP) samples were subjected to a two-step non-isothermal autohydrolysis process in order to obtain mixtures enriched in oligogalacturonides (OGalA) and arabinooligosaccharides (AOS) in separate streams. Operating at a maximum temperature of 130 °C, mixtures containing up to 30.4% oven-dry basis (o.d.b.) of OGalA with an OGalA/AOS ratio of 5.0 g/g were obtained during the first stage. Then, the treated solids were subjected to a second treatment at temperatures in the range 160–175 °C. When those solids were treated up to 175 °C, a mixture mainly made up of AOS (37.5% o.d.b.) with an AOS/OGalA ratio of 3.91 g/g was obtained as an effluent from the reactor. In order to increase their purity, both streams were then subjected to different refining steps. A product enriched in highly methylated and partially acetylated OGalA (42.5% o.d.b., degree of methylation (DM) = 69.2% mol/mol and degree of acetylation (DA) = 36.4% mol/mol), containing 17.2% o.d.b. of non-volatile non-identified compounds, was obtained by membrane filtration of the first-stage liquors, whereas a second one, mainly made up of AOS and galactooligosaccharides (GalOS) (55.0% AOS o.d.b., 13.8% GalOS o.d.b., and 13.3% non-volatile non-identified compounds, o.d.b.), was manufactured after an ion exchange treatment followed by membrane filtration of the second-stage liquors. This strategy was demonstrated to be a suitable and scalable alternative for the separate production of refined mixtures rich in OGalA or neutral pectic-oligosaccharides. Both types of products can result in different effects on the intestinal microbiota: AOS and GalOS show a significant bifidogenic effect and they could be consumed alone or combined with selected probiotic strains of Bifidobacteria for improving an unbalanced microbiota, whereas OGalA has been demonstrated to have a variety of biological properties and can promote the growing of some bacteria such as Faecalibacterium prausnitzii, a butyrate-producing microorganism underrepresented in patients with active IBD and infectious colitis.

Efficient removal of environmental pollutants by green synthesized metal nanoparticles of Clitoria ternatea

Prevention and management of water pollution are becoming a great challenge in the present scenario. Different conventional methods like carbon adsorption, ion exchange, chemical precipitation, evaporation, and biological treatments remove water pollutants. Nowadays, the requirement for effective, non-toxic and safe waste management strategies is very high. Nanomaterials have been explored in various fields due to their unique characteristics. Green synthesis of nanomaterial is becoming more popular due to their safety, non-toxicity, and ease of scale-up technology. Metal nanoparticles can be synthesized using a green synthesis method using biological sources provided by eco-friendly, non-hazardous nanomaterials with superior properties to bulk metals. Hence, this study has designed a green synthesis of magnetic (cobalt oxide) and noble (gold) nanoparticles from the fresh flowers of Clitoria ternatea. The flavonoids and polyphenols in the extract decreased the energy band gap of cobalt oxide and gold nanoparticles; hence, the capping of the natural constituents in Clitoria ternatea helped form stable metal nanoparticles. The cobalt oxide and gold nanoparticles are evaluated for their potential for eliminating organic pollutants from industrial effluent. The novelty of this present work represents the application of cobalt oxide nanoparticles in the removal of organic pollutants and a comparative study of the catalytic behaviour of both metal nanoparticles. The degradation of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of gold nanoparticles was completed in 120, 45, and 20 min with rate constants of 3.7 × 10−3/min, 6.9 × 10−3/min, and 16.5 × 10−3/min, respectively. Similarly, the photocatalysis of bromophenol blue, bromocresol green, and 4–nitrophenol in the presence of cobalt oxide nanoparticles was achieved in 60, 90, and 40 min with rate constants of 2.3 × 10−3/min, 1.8 × 10−3/min, and 1.7 × 10−3/min, respectively. The coefficient of correlation (R2) values justify that the degradation of organic pollutants follows first-order kinetics. The significance of the study is to develop green nanomaterials that can be used efficiently to remove organic pollutants in wastewater using a cost-effective method with minimal toxicity to aquatic animals. It has proved to be useful in environmental pollution management.

Natural flavonols as probes for direct determination of borax: From conventional fluorescence analysis to paper-based smartphone sensing

Borax is strictly regulated in the food processing and pharmaceutical industry due to its physiological toxicity, and the development of a direct analytical method is essential for effectively monitoring the borax abuse. In this work, the fluorescence properties of flavonoids, including flavones, isoflavones and flavonols, were systematically investigated from aqueous to borax solutions, and it was found that the weak intrinsic fluorescence of flavonols could be pervasively sensitized by borax. A natural flavonol, morin, was subsequently chosen as a representative probe to develop a turn-on fluorescence sensing method for borax analysis, which achieved a linear response spanning four orders of magnitude with a detection limit of 1.07 μM (0.22 μg mL−1 in terms of Na2B4O7 content). Furthermore, a smartphone-assisted paper-based test device was designed and constructed by 3D printing technology. Using morin-impregnated test strips as the carrier, the borax could be visually detected by the RGB signals of the captured images, with a detection limit of 0.13 mM (27.05 μg mL−1 for Na2B4O7). Combining ion exchange treatment for food samples and sodium periodate oxidation for drug samples, the developed methods were successfully applied for the direct analysis of borax in various products with the recoveries of 86.9–106.3% for traditional fluorescence analysis and 82.7–108.8% for smartphone-assisted fluorescence sensing. The fluorescence property of the morin-borax system was studied using time-dependent density functional theory, and the sensing mechanism was discussed in conjunction with experimental research.

DETERMINATION OF PHYSICAL AND CHEMICAL PARAMETERS OF WATER BEFORE AND AFTER ION EXCHANGE TREATMENT

In accordance with consumer requirements, the water must be adequately purified, and the corresponding parameters within the defined values. Various methods are used for this purpose, of which the ion exchange method can be highlighted as the simplest, most efficient and economically profitable. Ion exchange is a reversible process of ion exchange between a solid phase and an electrolyte solution. The ion exchanger is a macromolecular insoluble material that has chemically bound electrified groups and mobile, oppositely charged ions that compensate for this electrification. Ion exchangers are usually used in the form of compact or granular beds that fill the column through which the solution with the ions to be exchanged flows.They usually contain phenolic, carboxylic, sulfonic amino and other groups, which is why the treatment also results in decarbonization, softening, demineralization and denitrification of water. As the assessment of water quality is based on the most significant physico-chemical parameters, the aim of the work is the analysis of drinking water before and after treatment with an ion exchanger.For this purpose, organoleptic parameters such as smell, taste and color were first analyzed. After that, physico-chemical parameters were analyzed: pH values, electrical conductivity, m-alkalinity, p-alkalinity, water hardness, organic matter content, chloride content, iron and manganese content. An ion exchanger based on resin was used, which after use was regenerated by washing with NaClsolution.The analysis of the water sample, before and after the ion exchange treatment, showed that the treatment process was effective and that the decarbonization and softening of the water was carried out, whereby the water was categorized as soft water (water &lt;9⁰dH).The analyzed water is tasteless, odorless and colorless before and after treatment. The results of the analysis showed that all the values of the analyzedphysico-chemical parametersare in accordance with the Rulebook on the Healthiness of Drinking Water(Official Gazetteof Federation of Bosnia and Herzegovina No.40/10) arebelow the maximum allowed values. KEYWORDS:water, ion exchange, physical-chemical parameters; water treatment

Improving separation of CH4 and N2 by adsorption on zeolite Y Ion–Exchanged with ammonium Cations: An experimental and Grand–Canonical Monte Carlo (GCMC) simulation investigation

The separation of methane (CH4) from industrially–important nitrogen (N2)-rich vent streams such as those in liquefied natural gas processing plants is challenging. Pressure swing adsorption (PSA) is a promising, cost–effective solution in gas separation, especially for small–scale units. Further development and commercialisation of PSA–based technologies require access to low–cost, selective adsorbent materials. The current work investigates the improved separation of CH4 from N2 by TMA–Y zeolite which is obtained from the ion exchange treatment of Na–Y zeolite with the ammonium salt tetramethylammonium chloride (TMACl). TMA–Y is commercially called Ionic Liquidic Zeolite (ILZ), patented at The University of Western Australia, and has now been demonstrated on tonne–scale. In particular, we use a combination of experimental and molecular simulation techniques to provide insights into the high CH4–over–N2 selectivity of TMA–Y. For this, we obtain equilibrium isotherms of CH4 and N2 on Na–Y at different temperatures and pressures before and after ion exchange. The true selectivities of the zeolite samples are determined using the Ideal Adsorbed Solution Theory (IAST) and binary–gas grand–canonical Monte Carlo (GCMC) molecular simulations. From experiments and IAST calculations, we report an increase of >110% in the CH4/N2 selectivity of Na–Y after treatment with TMACl (from 2.2 to 4.7 at 5.0 MPa and 303.15 K for a mixture of 0.1 CH4+0.9 N2 mol.mol−1). GCMC molecular simulations provide a detailed picture of the molecular origins of this effect. Specifically, the introduction of TMA+ ions into the structure of Na–Y zeolite leads to a reduction of the available adsorption volume by more than 40% (from 0.30 to 0.17 cm3.g−1 with N2 as the probe molecule) for both adsorbing gas species (i.e. CH4 and N2). However, at the same time, this leads to stronger CH4–cation interactions due to the much higher affinity of TMA+ cations (5 kJ.mol−1) than extra–framework Na+ cations (1 kJ.mol−1) towards CH4. The overall effect of these two trends combined is the higher selectivity of the resulting TMA–Y zeolite for CH4. These molecular insights are useful in the systematic engineering of new materials with improved separation performance.

Copper nanoparticle and point defect formation in Cu+-Na+ ion-exchanged glass using protons of 2 MeV energy.

There are several applications for irradiating materials with protons that could provide alternative methodologies to synthesize and induce the formation of new compounds of different size scales. In this study, we explored the effects of proton irradiation oncommercial glass silicate that was previously subjected to a Cu+-Na+ ion exchange (IE) treatment at 600 °C for a duration of 60 min. The ion-exchanged glass samples were irradiated with protons (p+) of 2 MeV energy at doses in the range of thousands of grays (3.3 × 103, 7.9 × 103 Gy) and hundreds of thousands of grays (3.6 × 105 Gy). Significant changes in the optical and structural properties were observed post the radiation treatment. The UV-Visible absorption spectra of the irradiated samples revealed the appearance of overlapping absorption bands, which could be deconvoluted into three Gaussian-shaped bands peaking at 566, 620 and 680 nm. These three bands could be attributed to the surface plasmon resonance (SPR) of copper nanoparticles, non-bridging oxygen hole centers (NBOHCs) and self-trapped hole (STH) defects, respectively. Prominent photoluminescence (PL) was observed in the Cu-exchanged and irradiated samples, mainly induced by the presence of both Cu+ and Cu2O. Increasing the irradiation dose led to an increase in the PL intensity due to the conversion of Cu2+ ions into Cu+. This result was confirmed by electron paramagnetic resonance (EPR) spectroscopy that shows a decrease in the Cu2+ signal when increasing the dose of proton exposure. Transmission electron microscopy (TEM) and high-resolution TEM (TEM and HRTEM) observations confirmed the presence of copper nanoparticles (CuNPs) in the doped and p+ irradiated Cu-exchanged glass silicate samples. These CuNPs were found to be crystalline with an average size of 12.39 nm.

Low-cost fabrication of multicomponent silicate microspheres with tailored crystallization and morphology

This study presents a cost-effective method using sol-emulsion-gel approach to prepare micron-sized multicomponent silicate microspheres (SMs). SMs were obtained via rotary evaporation using water glass or silica sol as the silicon source. Results revealed that two-stage heating drying or two-step ion exchange treatment effectively suppressed crystallization in water glass-based SMs. The size and concentration of silicon sources and the rotary evaporation temperature dominated the sphericity and surface wrinkling of SMs. Smaller silicon sources like water glass or 5 nm silica sol with relatively high concentration, along with a suitable evaporation temperature like 65 °C, contributed to higher sphericity and smoother surfaces. The formation mechanism of microsphere crystallization and methods for its suppression were analyzed based on emulsion drying theory. Formation principles of microspheres with different morphologies were explained using wet-shell and dry-shell drying models. This method enables low-cost, large-scale fabrication of high-performance hollow glass microspheres (HGMs) with high quality SMs.

Advances in green materials derived from wood for detecting and removing mercury ions in water

The issue of mercury pollution in environmental remediation has garnered significant attention due to its severe health hazards to humans. Various strategies have been devised to mitigate the impact of toxic mercury ions, including coagulation, ion exchange, adsorption, membrane technology, and electrochemical treatment. Among these approaches, adsorption has emerged as an efficient and widely employed method for the uptake of low concentrations of mercury ions. It offers convenient operation, high removal efficiency, and facile regeneration of the adsorbent. Wood, being the most abundant renewable and sustainable bioresource, has garnered attention as a promising material for treating heavy metal wastewater. This is attributed to its unique physical and chemical characteristics, encompassing hierarchical pores, aligned channels, active functional groups, biodegradability, and cost-effectiveness. However, a comprehensive examination of the cutting-edge applications of wood and wood-derived biopolymers in the detection and removal of mercury ions from wastewater has yet to be undertaken. Consequently, this article presents a chronological overview of recent advancements in materials and structures derived from bulk wood and its constituents, including cellulose, lignin, hemicellulose, and tannin, with a specific focus on their utility in detecting and eliminating mercury from water sources. Subsequently, the most promising techniques and strategies involving wood and wood-derived biopolymers in addressing the predicament of mercury pollution are explored. Furthermore, this piece offers insights into the existing challenges and future prospects concerning environmentally friendly materials derived from wood, aiming to foster the development of cost-effective mercury adsorbents and detection devices.

Influence of reducing agent concentration on the luminescence and photophysical processes constant rates of silver clusters in silica-based glass

Series of silica-based glasses doped with antimony was synthesized to host luminescent silver clusters formed via Na+-Ag+ low-temperature ion exchange and heat treatment. Spectroscopic study reveals that increase in antimony concentration affects emission spectra, quantum yields, and fluorescence lifetimes. Photophysical processes rate constants, including radiative and nonradiative transitions and intersystem crossing, were estimated based on experimental spectroscopic characterization. Correlation between photophysical processes rate constants and increase in concentration of antimony was demonstrated.

In-situ formed hybrid phosphates coating layer enabling co-free Li-rich layered oxides with stable cycle performance

Li-rich layered oxides (LLOs) with high specific capacities over 250 mAh/g, are thought to be promising cathode materials for high energy density lithium-ion batteries. However, sluggish kinetics, irreversible oxygen release, and irreversible evolution of the surface/interface have led to poor cyclic properties, which are the principal barriers to commercial applications. In this work, an in-situ hybrid phosphates coating layer that combines the advantages of superior ionic conductivity (Li3PO4) and structural stability (LiTMPO4, TM = Ni, Mn) is proposed by an ion exchange and heat treatment method. Remarkably, the hybrid phosphates (Li3PO4-LiTMPO4) coating is not only deposited on the secondary particles of polycrystalline Co-free LLO surface, but also incorporated into the pores and edges of secondary particles. Based on the above advantages, the treated LLO exhibits an initial coulombic efficiency of 92.8%, excellent capacity retention, outstanding rate capability, and thermal stability. Advanced in/ex-situ measurements ascertain that the improvement mechanism of hybrid phosphates coating can be attributed to the synergistic effect of Li3PO4 and LiTMPO4, which transports lithium ions while reducing surface side reactions, and the strong P–O bond inhibiting irreversible oxygen release, thereby stabilizing the surface structure.

Plant-based biopolymers for wastewater pollutants mitigation

Abstract Pollution is one of the most pressing issues of modern times. Effluent in the world is escalating due to the exponential growth in the industrial and agricultural sectors. The effluents contain heavy metals, pesticides, and inorganic substances ultimately leading to the deterioration of the ecosystem. Even though there are numerous wastewater treatment methods like adsorption, membrane separation, ion exchange, and physical, mechanical, and chemical treatments. They are expensive and have the risk of second-hand pollution. Biopolymers are alternate and superior to synthetic polymers due to their environmentally friendly approach and high efficiency in treating wastewater. The most prominent plant-based biopolymers for the treatment of pollutants are cellulose, starch, carrageenan, alginate, xylan, inulin, pectin, and tragacanth. These have their advantages and disadvantages in bioremediation. The mechanism of pollution removal has adsorption, flocculation, bridge formation, and electrostatic patches. They are biodegradable as they are natural in origin. They have proved to remove toxic pollutants like chitosan, pullulan, polyhydroxy alkonates and butyrates, dextran, starch and cellulose, polyvinyl alcohol and polycaprolactone, gelatin, collagen and wheat gluten, alginate, heparin, and pectin to name a few. Biopolymers are also sourced from diverse sources like agricultural wastes and well-known sources like plants, animals, and microbes. Biopolymer and its composites are utilized as coagulants and flocculants. They are cellulose graft polyacrylamide, anionic sodium carboxymethylcellulose, guar gum graft polyacrylamide, pectin polyacrylamide, starch, and tannin. Nanotechnology has led to the development of elite nanohybrid bio-adsorbents to actively remove pollutants. These nano adsorbents have been targeting pollutants like azo dyes, bovine serum albumin, cationic dyes, parabens, and methylene blue among others. Biopolymer composites are also widely used for diverse applications primarily due to their enhanced mechanical and thermal properties. Biopolymers from natural and synthetic sources can be modified and used as per the requirement.

Improving the non-radical/radical transformation efficiency of halogenated polycyclic aromatic hydrocarbons by using metal ion-exchanged cryptomelane-type OMS-2 under moisture-unsaturated conditions

Halogenated polycyclic aromatic hydrocarbons (HPAHs) have recently remerged as major soil contaminants. However, limited studies have focused on the transformation and removal of HPAHs in soils. The transformation behaviors of HPAHs on cryptomelane-type manganese oxide (K(I)-OMS-2) and its metal ion-exchanged M-OMS-2 (M = Fe(III), Cu(II), and Zn(II)) under moisture-unsaturated conditions were systematically investigated. The transformation kinetics results showed that the transformation rate constants (k) of HPAHs were 0.077–0.829, 0.071–0.629, 0.068–0.530, and 0.064–0.259 d−1 for Fe(III)-OMS-2, Cu(II)-OMS-2, Zn(II)-OMS-2, and K(I)-OMS-2. The metal ion exchange treatment of K(I)-OMS-2 enhanced the transformation efficiency of HPAHs. The characterization (H2-TPR, CV, ESI, XPS, and EPR) and theoretical calculation (density of states and formation energy of oxygen vacancies) results indicated that the non-radical/radical transformation efficiency of HPAHs on M-OMS-2 was higher than that on K(I)-OMS-2. The transformation rate of HPAHs was positively correlated with the redox potential of metal ions and superoxide radical yield of M-OMS-2. Additionally, this study revealed that HPAHs with lower redox potential and more strongly bound to M-OMS-2 were more preferentially transformed. Finally, the experimental results of the addition of M-OMS-2 to the natural soil revealed that M-OMS-2 aids the transformation of HPAHs in soils. This study reveals the chemical transformation behavior of HPAHs in soils and suggests that M-OMS-2 can a promising agent for soil remediation.

Study of Structural and Optical Properties of Titanate Nanotubes with Erbium under Heat Treatment in Different Atmospheres.

Titanate nanotubes were synthesized and subjected to an ion exchange reaction with erbium salt aqueous solution to obtain titanate nanotubes exchanged with erbium (3+) ions. In order to evaluate the effects of the thermal treatment atmosphere on the structural and optical properties of erbium titanate nanotubes, we subjected them to heat treatment in air and argon atmospheres. For comparison, titanate nanotubes were also treated in the same conditions. A complete structural and optical characterizations of the samples was performed. The characterizations evidenced the preservation of the morphology with the presence of phases of erbium oxides decorating the surface of the nanotubes. Variations in the dimensions of the samples (diameter and interlamellar space) were promoted by the replacement of Na+ by Er3+ and the thermal treatment in different atmospheres. In addition, the optical properties were investigated by UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The results revealed that the band gap of the samples depends on the variation of diameter and sodium content caused by ion exchange and thermal treatment. Furthermore, the luminescence strongly depended on vacancies, evidenced mainly by the calcined erbium titanate nanotubes in argon atmosphere. The presence of these vacancies was confirmed by the determination of Urbach energy. The results suggest the use of thermal treated erbium titanate nanotubes in argon atmosphere in optoelectronics and photonics applications, such as photoluminescent devices, displays, and lasers.

Sorptive removal of short-chain perfluoroalkyl substances (PFAS) during drinking water treatment using activated carbon and anion exchanger

Laboratory tests and column tests were carried out in a waterwoks to investigate the removal of short- and long-chain PFAS using activated carbon filtration and ion exchange treatment. For all adsorbents, the sorption affinity of short-chain per- and polyfluoroalkyl carboxylic acids (PFCA) was significantly lower than that of long-chain PFAS or short-chain per- and polyfluoroalkyl sulfonic acids (PFSA). In the PFAS-polluted groundwater matrix, the short-chain PFCA PFBA and PFPeA could only be sufficiently removed with activated carbon over short run times of 6000 and 11,000 bed volumes (BV), respectively. Longer PFCA with a chain length of C6 or more were removed over longer run times.The removal of short-chain PFCA using ion exchange media could also only be achieved over relatively short run times of 5000 BV for PFBA, 10,000BV for PFPeA and 18,000 BV for PFHxA. These are sometimes significantly longer than those of activated carbon. Due to the higher material costs for ion exchange media, there are nevertheless no lower operating costs when the ion exchangers are used in single-use mode. However, ion exchangers can be regenerated and then reused which can result in economic advantages compared to activated carbon filtration. However, for the extensive regeneration, especially for the elution of the long-chain PFAS, the additional use of ethanol is needed in the process. In contrast, the short-chain PFBA and PFPeA can be extracted without organic solvent from a weakly basic ion exchanger.