Anionic Ones Research Articles

Mixing Order Asymmetry in Nanoparticle-Polymer Complexation and Precipitation Revealed by Isothermal Titration Calorimetry.

In recent years, there has been a renewed interest in complex coacervation, driven by concerted efforts to offer novel experimental and theoretical insights into electrostatic charge-induced association. While previous studies have primarily focused on polyelectrolytes, proteins, or surfactants, our work explores the potential of using cerium (CeO2) and iron (γ-Fe2O3) oxide nanoparticles (NPs) to develop innovative nanomaterials. By combining various charged species, such as polyelectrolytes, charged neutral block copolymers, and coated NPs, we study a wide variety of complexation patterns and compare them using isothermal titration calorimetry, light scattering, and microscopy. These techniques confirm that the titration of oppositely charged species occurs in two steps: the formation of polyelectrolyte complexes and subsequent phase (or microphase) separation, depending on the system studied. Across all examined cases, the entropic contribution to the total free energy surpasses the enthalpic contribution, in agreement with counterion release mechanisms. Furthermore, our investigation reveals a consistent asymmetry in the reaction enthalpy associated with the secondary process, with exothermic profiles observed upon the addition of cationic species to anionic ones and endothermic profiles in the reverse case.

Rescue of dead MnO2 for stable electrolytic Zn-Mn redox-flow battery: a metric of mediated and catalytic kinetics.

The virtues of electrolytic MnO2 aqueous batteries are high theoretical energy density, affordability and safety. However, the continuous dead MnO2 and unstable Mn2+/MnO2 electrolysis pose challenges to the practical output energy and lifespan. Herein, we demonstrate bifunctional cationic redox mediation and catalysis kinetics metrics to rescue dead MnO2 and construct a stable and fast electrolytic Zn-Mn redox-flow battery (eZMRFB). Spectroscopic characterizations and electrochemical evaluation reveal the superior mediation kinetics of a cationic Fe2+ redox mediator compared with the anionic ones (e.g. I- and Br-), thus eliminating dead MnO2 effectively. With intensified oxygen vacancies, density functional theory simulations of the reaction pathways further verify the concomitant Fe-catalysed Mn2+/MnO2 electrolysis kinetics via charge delocalization and activated O 2p electron states, boosting its rate capability. As a result, the elaborated eZMRFB achieves a coulombic efficiency of nearly 100%, ultra-high areal capacity of 80 mAh cm-2, rate capability of 20 C and a long lifespan of 2500 cycles. This work may advance high-energy aqueous batteries to next-generation scalable energy storage.

Novel rod-like [Cu(phen)2(OAc)]·PF6 complex for high-performance visible-light-driven photocatalytic degradation of hazardous organic dyes: DFT approach, Hirshfeld and fingerprint plot analysis

A novel octahedral distorted coordination complex was formed from a copper transition metal with a bidentate ligand (1,10-Phenanthroline) and characterized by Ultraviolet–visible spectroscopy, Ultraviolet–visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller, Field emission scanning electron microscopy, and Single-crystal X-ray diffraction. The Hirshfeld surface and fingerprint plot analyses were conducted to determine the interactions between atoms in the Cu(II) complex. DFT calculations showed that the central copper ion and its coordinated atoms have an octahedral geometry. The Molecular electrostatic potential (MEP) map indicated that the copper (II) complex is an electrophilic compound that can interact with negatively charged macromolecules. The HOMO-LUMO analysis demonstrated the π nature charge transfer from acetate to phenanthroline. The band gap of [Cu(phen)2(OAc)]·PF6 photocatalyst was estimated to be 2.88 eV, confirming that this complex is suitable for environmental remediation. The photocatalytic degradation of erythrosine, malachite green, methylene blue, and Eriochrome Black T as model organic pollutants using the prepared complex was investigated under visible light. The [Cu(phen)2(OAc)]·PF6 photocatalyst exhibited degradation 94.7, 90.1, 82.7, and 74.3 % of malachite green, methylene blue, erythrosine, and Eriochrome Black T, respectively, under visible illumination within 70 min. The results from the Langmuir-Hinshelwood kinetic analysis demonstrated that the Cu(II) complex has a higher efficiency for the degradation of cationic pollutants than the anionic ones. This was attributed to surface charge attraction between photocatalyst and cationic dyes promoting removal efficiency. The reusability test indicated that the photocatalyst could be utilized in seven consecutive photocatalytic degradation cycles with an insignificant decrease in efficiency.

Long-term effect of municipal solid waste compost on the recovery of a potentially toxic element (PTE)-contaminated soil: PTE mobility, distribution and bioaccessibility

Compost from municipal solid waste (MSWC) can represent a resource for the environmental management of soils contaminated with potentially toxic elements (PTEs), since it can reduce their mobility and improve soil fertility. However, the long-term impact of compost on soil recovery has been poorly investigated. To this end, the influence of a MSWC added at different rates (i.e. 1.5, 3.0 and 4.5% w/w) to a multi-PTE-contaminated (e.g. Sb 412 mg kg−1, Pb 2664 mg kg−1 and Zn 7510 mg kg−1) sub-acidic soil (pH 6.4) was evaluated after 6 years since its addition. The MSWC significantly enhanced soil fertility parameters (i.e. total organic carbon, Olsen P and total N) and reduced the PTE labile fractions. The distribution maps of PTEs detected through µXRF analysis revealed the presence of Zn and Pb carbonates in the amended soils, or the formation of complexes between these PTEs and the functional groups of MSWC. A higher oral, inhalation and dermal bioaccessibility of each PTE was detected in the soil fine-grained fractions (< 2 and 2–10 µm) than in coarse particles (10–20 and 20–50 µm). The MSWC amendment generally did not modify the PTE bioaccessibility, while the relative bioaccessibility of cationic PTEs was greater than that of anionic ones (e.g. Cd > Zn > Pb > Sb > As). Pb and Sb showed the highest hazard quotients (e.g. 2.2 and 10 for Sb and Pb, respectively, in children). Overall, the results indicated that the MSWC used can be an effective option for the recovery of PTE-contaminated soils, even in the long term.

Metastable Charged Dimers in Organometallic Species: A Look into Hydrogen Bonding between Metallocene Derivatives.

Multiply charged complexes bound by noncovalent interactions have been previously described in the literature, although they were mostly focused on organic and main group inorganic systems. In this work, we show that similar complexes can also be found for organometallic systems containing transition metals and deepen in the reasons behind the existence of these species. We have studied the structures, binding energies, and dissociation profiles in the gas phase of a series of charged hydrogen-bonded dimers of metallocene (Ru, Co, Rh, and Mn) derivatives isoelectronic with the ferrocene dimer. Our results indicate that the carboxylic acid-containing dimers are more strongly bonded and present larger barriers to dissociation than the amide ones and that the cationic complexes tend to be more stable than the anionic ones. Additionally, we describe for the first time the symmetric proton transfer that can occur while in the metastable phase. Finally, we use a density-based energy decomposition analysis to shine light on the nature of the interaction between the dimers.

Multi-Element Doping Boosts a Layered Metal Oxide Electrode for Superior Water Oxidation

More than precisely controlling the active species to optimize the binding with reaction intermediates, applying lab-designed electrocatalysts for practical water electrolysis requires overcoming limitations of mass and electron transports, which are however difficult to achieve by a single strategy. Here, based on a category of layered cobalt oxides (ACoO2, A = alkali metal), we report a multi-element doping method to favor the in-situ reconstruction of more-active species during water oxidation, boost the electronic conductivities, and extend the potential range of kinetic currents. Specifically, various doping elements including both cationic and anionic ones were screened experimentally for ACoO2 and the composition of LiCo1-x-y-zNixFeyPdzO2 was identified with the optimal catalytic properties. Compared with common cobalt oxides and (oxy)hydroxides, LiCo1-x-y-zNixFeyPdzO2 regulated the in-situ catalyst reconstruction during both room- and high-temperature water oxidation, and boosted electronic conductivity by 2-4 orders of magnitudes. Consequently, LiCo1-x-y-zNixFeyPdzO2 outperformed RuO2, Co3O4, α- and β-Co(OH)2 by delivering an anion exchange membrane water electrolysis current density of 1 A cm-2 at about 1.75 V, and showed little degradation during the 500-hour stability test. This work represents a step forward in rationally boosting the catalytic properties of anode materials for practical membrane water electrolysis.

Novel anthracene and pyrene containing Cd(II)-based coordination polymers for adsorptive removal of toxic dyes from aqueous medium

In the present work, we have synthesized two new one- and two-dimensional Cd(II) coordination polymers (CPs), formulated as [Cd(L1)(Formamide)2]n (1) and [Cd2(L2)2(MeOH)2]n (2), by the solvothermal reactions of Cd(NO3)2·4H2O with the anthracene and pyrene group bearing carboxylic acids 5-{(anthracen-9-ylmethyl)amino}isophthalic acid (H2L1) and 5-{(pyren-1-ylmethyl)amino}isophthalic acid (H2L2), respectively. The newly synthesized CPs were characterized by FT-IR, elemental, thermogravimetry and single-crystal and powder X-ray diffraction analyses. The single-crystal X-ray diffraction analysis demonstrates that CPs 1 and 2 have one-dimensional double chain and two-dimensional structures, respectively. These novel CPs were employed for the adsorptive removal of various toxic cationic and anionic organic dyes in aqueous medium. Both CPs are highly effective for the removal of cationic dyes in comparison to anionic ones. However, the two-dimensional pyrene group containing CP 2 shows a higher efficiency (removal efficiency of 75–97 %) in removing three different 6 × 10−5 M cationic dyes. In addition, the adsorption kinetics and isotherms for both CPs were determined. An insight into the removal of the organic dyes is provided by in silico studies. Moreover, the stability and recyclability of both CPs were tested under adsorption conditions.

Low Energy Isomers and Infrared Spectra Simulations of C4H3N, C4H4N, and C4H5N and Related Ions

The relative stability of pyrrole derivatives were investigated by applying a global minimum (GM) search for the low-lying energy structures of C4HnN (n = 3-5) clusters at neutral, anionic, and cationic states. Several low-energy structures, previously not reported, were identified. The present results reveal a preference for cyclic and conjugated systems for the C4H5N and C4H4N compounds. In particular, the structures of the cationic and neutral C4H3N species are different from the anionic ones. For the neutrals and cations, cumulenic carbon chains were found, while for the anions, conjugated open chains were obtained. Of particular relevance, the GM candidates C4H4N+ and C4H4N are different from those reported previously. For the most stable structures, infrared spectra were simulated and the main vibrational bands were assigned. Also, a comparison with available laboratory data was done aiming to corroborate with experimental detection.

Alkyl chain length and headgroup dependent stability and agglomeration properties of surfactant-assisted colloidal selenium nanoparticles

In this study, we have systematically investigated and reported the growth, stability, and aggregation properties of selenium nanoparticles (Se NPs) in the presence of surfactant systems comprising different head groups and alkyl chain lengths. Here, the n-alkyl sulfates (C10-C14) and n-alkyl trimethylammonium bromides (C12-C18) were used as the anionic and cationic surfactants. The obtained results showed that the shortening in the alkyl chain length both in anionic and cationic groups does not affect the Se NPs morphologically, however it leads to a gradual increase in their mean sizes. It was also found that the surfactants having a cationic head group pave the way for forming the bigger NPs compared to the anionic ones. In addition, especially in the cationic group, the NPs were found to be in an increasing aggregation tendency with decreasing number of carbon atoms in the chain length. On the other hand, it was observed that the absorbance tends to decrease with time both in the anionic and cationic systems. The rate of decrease in the absorbance within the time revealed that the elongation in the alkyl chain length gives rise to a more stable nanoparticle solution for both surfactant systems. Furthermore, the results revealed that the surfactants having an anionic head group kept the Se NPs more stable in their solutions as compared to cationic ones. The scanning electron microscopy images corresponding to absorption measurements taken for certain days suggested that the formation of aggregated structures, which increase along with time in the nanoparticle solution, is responsible for the accelerated decrease in the absorbance as the tail length decreases.

Effect of coating nanostructure on the electrokinetics of polyelectrolyte-coated particles. Grafted vs adsorbed polymer

In this work, the electrokinetic response of nanoparticles suspensions under the action of alternating electric fields is analyzed for the case that the particles are coated with a shell of polyelectrolyte. This is an important field of application of colloidal systems, as the coating is necessary or even unavoidable for control of the stability or functionalization of the particles for a specific use. Characterization of the coating in situ is not an easy task, and electrokinetics can help in answering this question, if one goes beyond the simple routine evaluation of the electrophoretic mobility of the particles, which will provide information on the sign (and perhaps a sort of effective amount) of the surface charge and potential, but little more. The richness and rigour of the information is much more significant if AC fields are used. This is the case for the techniques evaluated in the present investigation, namely, AC electrophoresis and dielectric dispersion. They jointly sweep several decades in frequency, and are sensitive in different manners to the size of the particles, the charge of the core and the shell, the thickness and rigidity of the latter, etc. In addition, an important distinction is made between coatings with a soft or adsorbed layer structure and those with a grafted, ideally radially arranged (brush-like) polyelectrolyte. A model is first described for the AC electrokinetics in both cases, and it is demonstrated that the brush structure magnifies the Maxwell-Wagner (or double layer) polarization, leading to an elevation in the AC mobility for frequencies around the MHz, and it very much raises the amplitude of the alpha- or concentration-polarization relaxation detected in the dielectric dispersion. The distribution of the charge in a thicker region for the brush structure explains these results. Experimental investigations are carried out with silica spheres coated by PDADMAC (+) and PSS (-) polyelectrolytes in the soft-layer case, and by (vinylbenzyl)trimethylammonium chloride (+) and sodium 4-vinylbenzenesulfonate (-) monomers that were polymerized (grafted) on the particles. The results show that the brush coating produces the expected MW elevation of the mobility, mostly in the case of the cationic polymer, apparently better attached to the particles by electrostatic attraction to the negative charge of the core silica particles. In contrast, a rather monotonous decrease of the mobility in absolute value is measured for the soft coatings, indicating that the inertia of the particles sets out at lower frequencies because of aggregation. Dielectric spectra confirm the better stability in the presence of the grafted polymer, although a low-frequency elevation in the logarithmic derivative of the permittivity is a proof of the existence of aggregates, less abundant in any case than for soft coatings. Dielectric data also confirm the different amounts of charge, larger for grafted cationic layers than for anionic ones. Finally, the model elaborated can fit the experimental results yielding quantitative values of the main parameters of the coated particles, namely, effective size, overall charge of the coating, and thickness and ionic permeability of the latter.

Unveiling the Assembly of Neutral Marine Polysaccharides into Electrostatic-Driven Layer-by-Layer Bioassemblies by Chemical Functionalization

Marine-origin polysaccharides, in particular cationic and anionic ones, have been widely explored as building blocks in fully natural or hybrid electrostatic-driven Layer-by-Layer (LbL) assemblies for bioapplications. However, the low chemical versatility imparted by neutral polysaccharides has been limiting their assembly into LbL biodevices, despite their wide availability in sources such as the marine environment, easy functionality, and very appealing features for addressing multiple biomedical and biotechnological applications. In this work, we report the chemical functionalization of laminarin (LAM) and pullulan (PUL) marine polysaccharides with peptides bearing either six lysine (K6) or aspartic acid (D6) amino acids via Cu(I)-catalyzed azide-alkyne cycloaddition to synthesize positively and negatively charged polysaccharide-peptide conjugates. The successful conjugation of the peptides into the polysaccharide's backbone was confirmed by proton nuclear magnetic resonance and attenuated total reflectance Fourier-transform infrared spectroscopy, and the positive and negative charges of the LAM-K6/PUL-K6 and LAM-D6/PUL-D6 conjugates, respectively, were assessed by zeta-potential measurements. The electrostatic-driven LbL build-up of either the LAM-D6/LAM-K6 or PUL-D6/PUL-K6 multilayered thin film was monitored in situ by quartz crystal microbalance with dissipation monitoring, revealing the successful multilayered film growth and the enhanced stability of the PUL-based film. The construction of the PUL-peptide multilayered thin film was also assessed by scanning electron microscopy and its biocompatibility was demonstrated in vitro towards L929 mouse fibroblasts. The herein proposed approach could enable the inclusion of virtually any kind of small molecules in the multilayered assemblies, including bioactive moieties, and be translated into more convoluted structures of any size and geometry, thus extending the usefulness of neutral polysaccharides and opening new avenues in the biomedical field, including in controlled drug/therapeutics delivery, tissue engineering, and regenerative medicine strategies.

Design strategy of infrared 4-hydroxybenzylidene-imidazolinone-type chromophores based on intramolecular charge transfer: A theoretical perspective

Partial genetically encoded 4-hydroxybenzylidene-imidazolinone (HBI)-type chromophores are new promising fluorescent probes, which are suitable for imaging and detection of living cells. However, the lack of infrared chromophores hinders the development seriously. Here more than 30 HBI-type chromophores with regular structure modifications were employed and typical spectral redshift change laws and mechanisms were investigated by quantum methods. Results show that both one-photon spectrum (OPS, absorption/emission) and two-photon absorption (TPA) can achieve large redshift via either extending conjugated lengths of frag-3 or enlarging conjugated areas of frag-1 of HBI skeleton. Spectral redshifts of all chromophores are highly related to intramolecular charge transfer (ICT), but neutral ones are closely related to the total ICT or electron-accepting-numbers of frag-3, and the high correlative factor of anions is the aromaticity of frag-2 bridge. The frag-2 bridge with high aromaticity can open a reverse charge transfer channel in anion relative to neutral, obtaining significant redshift. Based on analysis, a new 6-hydroxyl-naphthalene-imidazolinone (HNI) series, which have larger conjugated area in frag-1, are predicted. The OPS and TPA of anionic HNI ones acquire about 76–96 nm and 119–146 nm red-shift relative to traditional HBI series respectively as a whole. The longest emission of anionic HNI-4 realizes more 244 nm redshift relative to HBI-1. Our work clarifies worthy spectral regularities and redshift mechanisms of HBI-type chromophores and provides valuable design strategy for infrared chromophores synthesis in experiment.

Alkaline ball-milled peanut-hull biosorbent effectively removes aqueous organic dyes

Advanced biosorbents increasingly attract attention for their application in environment remediation. Here, a facile one-step approach to alkaline ball milling was used to synthesize a porous peanut hull biosorbent without heating. The alkaline ball-milled peanut-hull (ABP) biosorbent was characterized for its ability to remove Congo red (CR), titan yellow (TY), and methyl violet (MV) from aqueous solutions. ABP processed abundant O-containing functional groups and developed porosity, resulting in maximum sorption capacities of 4864.4 (CR), 455.9 (TY), and 126.1 (MV) mg g−1. Freundlich isotherm and PSO kinetic models best fit the anionic dye's (CR and TY) adsorption by ABP, indicating multiple mechanisms might control the adsorption process. Freundlich and PFO kinetics models best described cationic MV adsorption by ABP, suggesting the adsorption of cationic dye could also be governed by multi-mechanisms but less heterogeneous than that of anionic dye. The results suggest that alkaline ball-milling is promising approach to converting biomass into advanced biosorbents for organic dyes, especially anionic ones.

The Use of Allochthonous Tropical Peat Swamps of Antananarivo for Dyes Elimination in Effluents

Textile industries play an important role in the economy of developing countries. However, these industries are among the major consumers of water and chemical inputs. They reject considerable quantities of wastewater, the quality of which sometimes threatens the environment due to the inefficiency of the treatment methods used. This is combined with the inaccessibility to the advanced purification technologies because of their high cost. Many low-cost materials have been studied by scientists to treat effluents. The ATP (allochthonous tropical peat) of Antananarivo, Madagascar, has aroused interest in the treatment of wastewater, especially for colored textile effluents. The physico-chemical characteristics of the ATP are determined, then the BLM dye (methylene blue) is used as a model dye for adsorption. After that, treatment tests in the form of filtration are carried out with textile effluent. This study showed that ATP removes cationic dyes more favorably than anionic ones at pH greater than 4.2, the zero-charge point of peat. The adsorption of BLM, a cationic dye, on ATP is physisorption and endothermic. A maximum of 20mg of BLM dye is adsorbed per gram of ATP and its follows the Langmuir model. The analysis of the IR spectra showed that the carboxylic function and the phenol group of the peat are involved on the dye fixation. The treatment of effluent taken from the textile industry revealed that ATP improves the pH and the color of the effluent; however, it increases the COD due to the presence of certain organic acids.

Study of thermal decomposition of hay-based activated biocarbons modified with nanolayers of ionic polyacrylamide

The thermal behaviour of hay-based activated carbons modified with adsorption nanolayers of ionic polymers were investigated. The anionic and cationic forms of polyacrylamides (PAM) with different contents of ionizable groups were applied. Using spectrophotometry, potentiometric titration, microelectrophoresis, DCS (Differential Centrifugal Sedimentation) and thermal analysis methods, the adsorption and electrokinetic, properties, as well as thermal stability of studied activated biocarbons—PAM systems were established. It was shown that PAM adsorbed amounts on the activated biocarbon surfaces were considerably higher for cationic polyacrylamides than for anionic ones. The conducted TG-DSC-FTIR/MS analysis in helium showed a significant influence of the synthesis conditions on the content of oxygen surface groups of activated biocarbons obtained in conventional or microwave muffle furnace. The measurements carried out in the oxidizing atmosphere for the polymer-modified samples showed similarity to the original materials and were characterized by three main stages of decomposition: dehydration, decomposition of surface functional groups and, at high temperatures—combustion process. The main decomposition products were CO2 and H2O.

Graphene oxide, kaolinite clay and PVA-derived nanocomposite aerogel as a regenerative adsorbent for wastewater treatment applications

Present work addressed the polyvinyl alcohol (PVA)-assisted gelatinisation of thoroughly dispersed graphene oxide (GO) and Kaolinite clay sheets into hydrogel, followed by lyophilisation to prepare the lightweight (0.024 g.cm−3) and remarkably porous (96.6%) clay-GO-PVA (CGP) composite aerogel by removing of frozen water (ice) through sublimation. The macroporous channels in CGP aerogel besides the mesoporosity of constituent materials facilitated the mass transfer (wastewater) and enhanced the accessibility of surface-active sites for dye adsorption. The CGP aerogel enriched with ample oxygen functionalities exhibited negative zeta potential (−25 mV), facilitating higher adsorption of cationic dyes than anionic ones. The excellent fitting of MB dye adsorption by Langmuir equilibrium isotherm suggested uniform dye adsorption on the surface of CGP aerogel with a maximum adsorption capacity of 535 mg.g−1. The spectroscopic analyses (XPS, FTIR, Raman) revealed charge-driven electrostatic attraction, hydrogen linkages (dipole-dipole and Yoshida), π-π, and n-π interactions between the surface-active sites of CGP aerogel and organic dyes as major adsorptive pathways. The MB dye adsorption increased with temperature and gradually declined with increasing ionic strength of simulated wastewater. The weak acidic to neutral pH range showed higher adsorption of MB dye by CGP aerogel. The size, charge, and hetero atoms of organic dyes, surface-active sites, charge, and porosity of aerogel, along with accessibility to adsorption sites through structural porosity, governed the adsorption process. The CGP aerogel showed excellent regenerability for subsequent batches and exhibited 98% MB dye removal efficiency even after seven adsorption-desorption cycles. Such porous nanocomposite aerogel shows immense potential for wastewater treatment applications to remove organic pollutants.

The synthesis of the P/N-type NdCoO3/g-C3N4 nano-heterojunction as a high-performance photocatalyst for the enhanced photocatalytic degradation of pollutants under visible-light irradiation

The treatment of industrial and domestic colored effluents and the use of photocatalysts have today attracted much attention among researchers. With the varied photocatalytic materials, the ones with narrow bandgap are thus of greater significance thanks to their acceptable performance in optical fields. The other obvious property of such materials is their lower costs because a large part of sunlight is in the visible region. In this work, the bare perovskite-type neodymium cobaltite and neodymium cobaltite/graphite carbon nitride (p/n-type NdCoO3/g-C3N4) was synthesized using sol-gel auto combustion. Different reductants were also employed during this fabrication for morphological engineerings, such as glucose (carbohydrate), L-valine (amino acid), and citric acid. As well, X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (EDS) were utilized to prove the purity of the specimens, and then transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FE-SEM) were applied to explore their morphology. The various properties of the product, such as the optical, magnetic, porosity, and surface features, were correspondingly checked by diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, vibrating-sample magnetometry (VSM), and Brunauer-Emmett-Teller (BET) surface area analysis, respectively. Citric acid was thus selected as an optimal fuel because of the formation of finer particles and morphology. In addition, the NdCoO3 nanoparticles (NPs) were exploited as a catalyst for the degradation of anionic dyes (viz. erythrosine [Red No. 3], methyl orange [MO], and eriochrome black T [EBT]) and cationic ones (i.e., rhodamine B [RhB], acid red 14 [ACR14], and acid yellow 23 [AY23]) under visible-light irradiation. The study findings accordingly revealed that the heterostructures emerged at the interfaces between the p-type NdCoO3 and n-type g-C3N4, leading to the EBT decolorization, reached 95.8% after 120 min, and were higher than the photodegradation of the pristine NdCoO3 and g-C3N4.

Comparative Study of Polysaccharide-Based Hydrogels: Rheological and Texture Properties and Ibuprofen Release.

Polysaccharides are attractive gelling agents in pharmacy due to their safety, biocompatibility, biodegradability, relatively easy way of preparation, and low price. Due to their variable physical-chemical properties, polysaccharides have potentialities to be used for designing new drug delivery systems for controlled drug release. In this comparative study, rheological and texture properties as well as the in vitro release of model drug ibuprofen (IBU) with 11 polysaccharide-based hydrogels were investigated. The in vitro release of IBU significantly differed between (i) neutral (hydroxy/alkylcelluloses), (ii) anionic (carboxyalkylcellulose and its sodium salt, tragacanth, carrageenan, xanthan gum), and (iii) cationic (chitosans) hydrogels due to different contribution of provided interactions and viscosity within the hydrogel groups. The drug release kinetics of each hydrogel system was evaluated for five kinetic models. Several combinations of cationic hydrogels with neutral or anionic ones were performed to illustrate possibilities of providing modified IBU release profiles. In this context, chitosan was presented as an effective modifier of diffusion profiles for negatively charged drugs formulated into combined polymeric systems, providing their prolonged release. The most appropriate hydrogel for the topical application (i.e., providing favorable rheological and texture properties along with the highest drug release) was selected from a studied series of polysaccharide-based hydrogels.

Reuse of iron ore tailings as an efficient adsorbent to remove dyes from aqueous solution

ABSTRACT In this work, an iron ore tailings sample (IOT), collected from a tailings dam in Minas Gerais, Brazil, was characterized. The IOT presented point of zero charge of ∼ 6, specific surface area of 4 m2 g−1, and was mainly composed of hematite and quartz. Subsequently, experiments were performed to evaluate the adsorption of an anionic dye, Direct Red 80 (DR80), and a cationic dye, Methylene Blue (MB), by the IOT, studying the effects of its dose (doseIOT) and the solution initial pH (pH0). The DR80 removal increased with the decrease of the pH0 while the opposite effect occurred in the experiments with the MB, suggesting the process is governed by the adsorption resulting from electrostatic forces. The increase in the doseIOT increased the DR80 and MB removal, which can be attributed to the greater availability of adsorption sites. Pseudo-second order kinetic (R2 > 0.9994) and the Langmuir equilibrium isotherm (R2 > 0.9842) models described well the DR80 adsorption by the IOT, being the reaction rate and maximum adsorption capacity higher at lower pH0. In a regeneration experiment, it was possible to desorb almost entirely the DR80 using a NaOH solution. Additionally, the regenerated IOT was able to adsorb the DR80, demonstrating its reusability. In a preliminary assay, the IOT decreased the colour of the textile wastewater sample at pH0 3. Therefore, the results indicate the potential use of IOT for removing electric-charged pollutants by adsorption, especially anionic ones under acidic conditions.

AN EFFECTIVE BIOSORBENT DERIVED N EFFECTIVE BIOSORBENT DERIVED FROM PRODUCTION WASTE ROM PRODUCTION WASTE FOR WATER TREATMENT: STUDYING OR WATER TREATMENT: STUDYING THE ADSORPTION OF SYNTHETIC DYES HE ADSORPTION OF SYNTHETIC DYES

Introduction. Eco-friendly disposal of food waste, in particular, nutshells and fruit kernels, is an important issue to ensure sustainable nature management. These secondary raw materials are the source of valuable polymeric materials, cellulose and lignin.Problem Statement. IGiven the capacity of the food industry in Ukraine and the amount of waste produced, the development of technologies for processing lignin-cellulose biomass is an important research and practical issue.Purpose. The purpose of this research is to study the adsorption properties of chemically modified biosorbent based on plant materials concerning synthetic dyes of different types and classes; to assess the feasibility of biosorbent production and efficiency of its application in water treatment.Materials and Methods. Lignocellulose sorbent (LCS) has been synthesized from non-wood raw materials by chemical modification with the use of phosphoric acid with the addition of urea in an aqueous media. The Fourier transform infrared and standard methods of plant raw material analysis have been used to determine the physicochemical characteristics of LCS. The adsorption of anionic (methyl orange, alizarin red S, eosin Y), cationic (methylene blue, neutral red), and nonionic (aniline yellow) dyes on LCS from aqueous solution has been studied in the batch mode.Results. The adsorption capacity of LCS towards cationic dyes (47.0–53.3 mg/g) is higher than that of anionic (22.2–36.9 mg/g) and nonionic (4.7 mg/g) ones. The adsorption kinetics have been adequately described by a pseudo-second-order equation. Adsorption of all classes of dyes on LCS is thermodynamically feasible, spontaneous, and endothermic process. The liquid by-product of LCS production contains 15% nitrogen and 10% phosphorus, so it may be used as a fertilizer. Conclusions. The proposed method for processing food waste provides obtaining effective sorbent and liquid NP-fertilizer. LCS removes both cationic and anionic pollutants from water, so it may be considered a promisingbiosorbent for water purification.