Thermal Degradation Steps Research Articles

A new method based on TGA/FTIR coupling to quantify the different thermal degradation steps of EVA/HNT composites prepared by different processing

The aim of the present article is to expose a new method based on TGA-FTIR coupling to quantify the different steps of the thermal degradation of EVA in the presence of HNT. Moreover, this quantification of the thermal degradation was also correlated to the color change. EVA/HNT composites were processed with different processing conditions: solvent casting in THF or melt blending at different temperatures. The HNT fillers content (from 10 wt% up to 30 wt%) and the melt blending temperature (at 130 °C, 150 °C, 170 °C and 190 °C) were varied. The thermal degradation of EVA in the presence of HNT presents three noticeable steps as evidenced by TG analysis: i) P1, which was identified as the catalytic degradation of vinyl acetate (VA) part of EVA occurring during the heating ramp (around 250 °C), ii) P2, which is the main degradation of VA (around 350 °C) and iii) P3, which is the degradation of the polyethylene chain of EVA (around 500 °C). Nevertheless, in the case of melt blended EVA/HNT composites, macroscopic changes (strong smell and browning color) indicate a thermal degradation occurring during the melt blending process, namely P0. FTIR-TGA coupling allows to quantify the contribution of P0, P1 and P2 (thermal degradation of VA units of EVA) using Gram Schmidt curves of released acetic acid gas which are obtained from the COac. band of acetic acid at 1795 cm−1. The contribution of each thermal degradation step of the VA part of EVA (named P0 to P2) was then quantified and reported as A0 to A2, respectively. The blending process (solvent or melt) such as the HNT fillers content and the melt blending temperatures have a significant influence on the EVA thermal degradation catalyzed by HNT. For example, it was shown that the thermal degradation of VA units occurring during the processing of EVA+ 30HNT composite (named A0 and catalyzed by the HNT) was of 40% for melt blending process (at 170 °C), whereas it was close to 0% for solvent casting process. Moreover, the macroscopic changes were evaluated by color measurements and an interesting correlation could be made between A0 and ΔE* which is the total color deviation. When a significant catalytic effect, during the melt process was observed (A0 values higher than 5%), the total color deviation ΔE* was increased linearly with A0. Finally, in order to avoid the catalytic effect of HNT on the EVA thermal degradation, a functionalization strategy has been developed with an organosilane leading to the suppression of P1, the catalytic degradation of VA in TG analyses.

Thermal Analysis and Biocidal Studies of Copper (II) Soapgroundnut Complex Containing Urea and Thiourea as a Ligand

Background: Studies on the thermal decomposition of synthesized complexes have great importance for calculating the thermal stability and characterization of copper (II) soap complexes, and represent new investigations on the solution of environmental problems. Aim: The present research work aims to report new findings in the field of thermogravimetric analysis and biocidal studies for copper (II) groundnut complexes with urea and thiourea ligands. Objective: The objective of this study was to conduct the kinetic analysis of copper (II) soap complexes of nitrogen and sulphur-containing ligands with the help of a thermogravimetric analyser (TGA), as this technique is commonly applied for thermal analysis. Methods: In relevance of aforesaid applications, the present work deals with determining the different thermal degradation steps of newly synthesized copper (II) groundnut urea complex (CGU) and copper (II) groundnut thiourea complex (CGT) by using Coats- Redfern, Horowitz-Metzger, Broido, and Piloyan-Novikova equations for determining kinetic parameters, i.e., the energy of activation (E), rate constant, order of decomposition reaction, and pre-exponential factor (Z). Results: The results obtained from kinetic parameters were used to evaluate the thermodynamic parameters, i.e., entropy of activation (ΔS), enthalpy of activation (ΔH), and Gibbs free energy of activation (ΔG), corresponding to the activation by using previously mentioned equations. Kinetics of degradation for the synthesized complexes in solid state were studied using thermogravimetric analysis technique (TGA) in nitrogen atmosphere. Conclusion: The present study has discussed the biocidal activities of these complexes against Staphylococcus aureus and an explicit correlation between structure and biological activity has also been provided.

Preparation of Composite Hydrogels with Silica Nanoparticles by Photoinitiated Polymerization Reaction

In this study, (3-mercaptopropyl) trimethoxysilane (MPTMS) modified silica nanoparticles (SiO2-MPTMS) were successfully prepared. The average size of SiO2-MPTMS nanoparticles was measured by Dynamic Light Scattering (DLS) as 341 nm in ethanol, while Scanning Transmission Electron Microscopy (STEM) analyzes confirmed that the nanoparticles were nano-sized and revealed that their shapes were spherical. Then, 3D nanocomposite hydrogels were prepared by incorporating SiO2-MPTMS nanoparticles in various ratios (0.25, 0.50, 0.75 and 1.0 wt %) into an acrylate resin consisting of N-isopropyl acrylamide (NIPAM) and polyethylene glychol diacrylate (PEGDA; as a crosslinker) by the photoinitiated polymerization reaction with Dimethoxy-2-phenylacetophenone (DMPA; as a photoinitiator). By Thermal Gravimetric Analyzer (TGA) measurements, it was determined that the nanocomposite hydrogels maintained their thermal stability up to 330 0C and the thermal degradation steps were close to each other. Scanning Electron Microscopy (SEM) study showed that the neat and nanocomposite hydrogels’ morphological structures were in the porous and smooth scaffold, and also that the SiO2-MPTMS nanoparticles (0.50 wt %) were homogeneously distributed in the network structures of hydrogels, localized in the bonds.

Synthesis, Characterization, Anti-bacterial and Anti-inflammatory Activities of Bismuth(III) Complexes Based on 5-chloro-2-mercaptobenzothiazole

Bismuth, known as a heavy metal, is excluded from this class due to its low toxicity. Due to this feature, bismuth containing compounds have always been interesting compounds in the field of medicinal chemistry. For this reason, the discovery of new bismuth compounds and the investigation of their biological properties are very important for this field. In this study, three new bismuth(III) compounds formulated as [Bi(L)2X3] (L: 5-chloro-2-mercaptobenzothiazole (ClMBZT); X: Cl, Br, and I) were synthesized for the first time and, the molecular structure of them were elucidated by a series of spectroscopic techniques. Thermal stability and degradation steps of the title compounds were analyzed by Thermogravimetric-Differential Thermal Analysis (TG-DTA). The antibacterial study has been conducted against six strains bacteria, and the results indicated that bismuth(III) compounds generally showed more effective antibacterial activity than free ligand. The anti-inflammatory potential of bismuth(III) compounds was investigated through in vitro lipoxygenase enzyme inhibition studies. The results show that bismuth(III) compounds have higher anti-inflammatory potential than free ligand.

Ag(μ‐en)][ReO4]: An Intermediate during Preparation of the Ethylene Epoxidation Catalyst

AbstractPreparation of a catalyst for the ethylene oxide production requires impregnation of a porous corundum support with an aqueous silver ethylene diamine oxalate complex solution, to which among others NH4[ReO4] is added. Here we report on [Ag(μ‐en)][ReO4] that precipitates from such a mixture. Single crystal structure analysis has revealed a striking similarity of the [Ag(μ‐en)]+ entity with the same complex cation encountered in[Ag(μ‐en)]2(C2O4)×2H2O. Silver is coordinated end‐on to the nitrogen atoms of the en ligands. The [ReO4]− anions are not bonded to the silver cations, but instead involved in N−H⋅⋅⋅O hydrogen bonds to the ethylene diamine molecules. The first step of thermal degradation occurs at approximately the same temperature for both, the main component precipitate [Ag(μ‐en)]2(C2O4)×2H2O and [Ag(μ‐en)][ReO4], warranting proximity of the rhenium promoter and the elemental silver deposit. At 300 °C, the temperature at which the catalyst for EO synthesis is commonly calcined, the decomposition product of plain [Ag(μ‐en)][ReO4] under synthetic air is Ag[ReO4], in full analogy to industrial manufacturing process for selected Re‐promoted EO catalyst formulations.

Novel Cr(III), Ni(II), and Zn(II) complexes of thiocarbamide derivative: Synthesis, investigation, theoretical, catalytic, potentiometric, molecular docking and biological studies

Throughout this research, the thiocarbamide derivative (H 2 L), and its Cr(III), Ni(II) and Zn(II) complexes have been reported. The thiocarbamide moiety was established with a reaction of benzoyl isothiocyanate and 1 H -1,2,4-triazol-3-amine. Structural elucidation of such compounds was achieved using elementary examination, spectral and magnetic experiments. The octahedral construction of the Cr(III) complex, the tetrahedral geometry of the Zn(III) complex and the mixed geometry (tetrahedral and square planar) of the Ni(II) complex have been verified by the optimization of structure using DFT. The action of Zn 2+ complex in the oxidative degradation of an organic azo-dye was investigated, and it showed promising results. The thermal degradation behavior of thiocarbamide metal complexes were studied as well as the calculation of the kinetic data for title compounds (E a , A, ΔH*, ΔS* and ΔG*) of thermal degradation steps has been tested utilizing two different techniques. Liver carcinoma (HePG2) and breast carcinoma (MCF-7) cytotoxicity as well as ABTS-antioxidant activities demonstrated the effective inhibitory of the Ni(II)-complex relative to other tested compounds. The antimicrobial activity of the compounds suggests that Cr(III) has the highest activity. Furthermore, the Molecular Operating Environment (MOE) program was used to calculate the binding affinity between the EGFR protein and the compounds under investigation.

Synthesis, Characterization, Isoconversional Analysis and Degradation Kinetics of Novel Acetate Coated Hydroxyethyl Starch: A New Candidate as a Drug Carrier

The hydroxethyl starch (HES) is very trending biopolymer in biomedical field. In recent research we have successfully synthesized a novel ester of HES, i.e., HES-acetate by acetylation of HES followed by investigation of its thermal behavior. The successful acetylation of HES was confirmed by Fourier Transform Infrared (FTIR) and Proton-Nuclear Magnetic Resonance (1H NMR) spectroscopic techniques. Thermal stability and thermal degradation kinetics of HES-acetate were investigated by thermo-gravimetric analysis. Flynn–Waal–Ozawa model was fitted to the thermal data to find the values of thermodynamic triplet (ΔS, ΔG and ΔE). Energy of activation (Ea) values of the major thermal degradation steps were found to be 242.85 and 287.17 kJ mol–1 for HES and HES-acetate, respectively. The order of degradation, integral procedural decomposition temperature (IPDT) and index of intrinsic thermal stability (ITS) were also taken into account. The results of the thermal analysis reveal that the HES-acetate gained significant thermal stability as compared to that of HES. This benign polysaccharide-based material was investigated for its potential in drug release studies by taking caffeine as a model drug. HES-acetate-based matrix tablets showed sustained release behavior of the drug indicating its potential for the development of oral delivery systems for sustained drug release.

Synthesis and spectroscopic characterizations of manganese(II), iron(III), copper(II) and zinc(II) hydrazine complexes as catalytic activity agents

ABSTRACT. This article deals with the preparation and coordination of NH2—NH2 hydrazine molecule compounds. The hydrazine sulfate complexes of Mn(II), Fe(III), Cu(II), and Zn(II) were prepared. These complexes were characterized by elemental, infrared, conduction, electron absorption spectroscopy, magnetic susceptibility, thermogravimetric analyses, X-ray powder diffraction (XRD) patterns and atomic force microscopy (AFM) studies. The magnetic measurements were confirmed that the Mn(II), Fe(III), Cu(II), and Zn(II) hydrazine complexes have an octahedral geometric structure. Thermogravimetric and its differential thermogravimetric analysis referred that all complexes passed through two-to-three thermal degradation steps with solid metal sulfate as a residual product. The infrared spectra inferred that the NH2—NH2 ligand forms complexes through nitrogen atoms of the—NH2 moiety, while the elemental analysis indicates [M(NH2—NH2)3]SO4 (where M = Mn(II), Cu(II), and Zn(II)) while the iron(III) complexes have the [Fe2(NH2—NH2)4(SO4)2]SO4 formula of coordination compounds, NH2—NH2 acts as a double bond. Both XRD and AFM analysis deduced that the synthesized hydrazine metal complexes were found to be in nano scale range 10—30 nm.
 
 KEY WORDS: Hydrazine, FTIR, AFM, XRD, Transition metals
 Bull. Chem. Soc. Ethiop. 2022, 36(1), 33-44. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i1.4

Synthesis, ligation characteristics and analytical utility of the Schiff base (E)-1-[4-(2,4-dihydroxybenzylidene)-amino)ethanone and its precious group metal (Ru3+, Pt4+ & Ir3+) complexes

A series of new Schiff base nano sphere complexes of Ru3+, Pt4+ and Ir3+ of the Schiff base (E)-1-[4-(2,4-dihydroxybenzylidene)-amino)ethanone (H2L) was synthesized and characterized. Formation of non-electrolytic complexes of the general molecular formulas [M2(HL)(Cl)x(NH3)y].zH2O, where M = Ru3+, Pt4+ and Ir3+, HL = monobasic ligand, x = 5, y = 4, z = 0 for Ru3+ (1); x = 7, y = 2, z = 1 for Pt4+ (2), and x = 5, y = 4, z = 1 for Ir3+ (3) was achieved, respectively. The chemical structures and the kinetic parameters of the thermal degradation steps of the complexes were assigned by Coats–Redfern (C-R) and Horowitz–Metzger (H-M) models. Ruthenium (III) complex (1) being d5 (low spin), S = 1/2 revealed paramagnetic character with µeff.of 1.82 B.M. The redox behavior of the complex [Pt2(HL)(Cl)7(NH3)2].H2O suggested the possible use of the title Schiff base for establishing cost effectiveness and precise voltammetric protocol for total quantification and chemical speciation of Pt2+ and Pt4+ species in water samples.

Synthesis, spectroscopic and thermal studies of Cu+2, Ni+2and Co+3complexes of Schiff base containing furan moiety. Antitumor, antioxidant, antibacterial and DNA interaction studies

Three mononuclear bioefficient imine‐based coordination complexes [Cu(FMIMBCP)2] (1), [Ni(FMIMBCP)2] (2), and [Co(FMIMBCP)3] (3) were synthesized using ligand [FMIMBCP = (((furan‐2‐yl)methylimino)methyl)‐6‐bromo‐4‐chlorophenol]. The formation of the complexes was ascertained by elemental analysis, Fourier transform infrared, UV–Visible, electrospray‐mass spectrometry, electron paramagnetic resonance, and thermogravimetric analysis. From the thermogravimetric curves, the kinetic and thermodynamic parameters of the thermal degradation steps were computed. The stability of the complexes has been calculated from quantum chemical parameters using HOMO‐LUMO energies. The comparative binding propensity profiles of above synthesized complexes with thecalf thymus‐DNA were investigated via UV absorption and fluorescence studies. On the basis of extended conjugation and increased chromophores, complex3exhibited superior bioactivity with greater calculated DNA binding constant values, (Kb) 5.73 × 104 M−1(3) as compared to complexes1(2.96 × 104 M−1) and2(8.38 × 103 M−1). The competitive binding titration with ethidium bromide (EB) revealed that metal complexes efficiently displace EB from the EB‐DNA system. The complexes were found to have pronounced cleavage efficiency as evaluated from agarose gel electrophoresis. The anticancer activity of the ligand and metal complexes against MCF‐7 and KB3 cells revealed that the complexes were more efficacious than the corresponding ligand. Further, in vitro antioxidant activity against DPPH proclaimed the remarkable bioefficiency of compounds, which makes them promising as an active chemotherapeutic agent. The complexes have strong antibacterial activity againstBacillus thuringiensis,Streptococcus pneumoniae,Escherichia coli, andPseudomonas putida.

Evaluation of Physicochemical, Spectral and Thermal Properties of Energy of Consciousness Healing Treated Iron Sulphate

Iron sulphate is used in the treatment of iron deficiency anaemia and other chronic disorders such as heart and kidney diseases. This study has the objective to analyze the impact of The Trivedi Effect®-Energy of Consciousness Healing Treatment on the physicochemical, spectroscopic and thermal properties of iron sulphate using various analytical techniques. In this, the test compound, i.e., iron sulphate was divided into two parts; one as control (without Biofield Energy Treatment), and the other as Biofield Energy Treated, which received the Biofield Energy Treatment remotely by the renowned Healer, Mr. Mahendra Kumar Trivedi. The PXRD analysis of the Biofield Energy Treated sample showed significant alterations in the range of -39.49 to 301.40% in the relative intensities, and from -15.40 to 33.36% in the crystallite sizes, compared with the control sample. The average crystallite size of the treated sample was also increased by 4.98% as compared to the control sample. The particle sizes in the treated sample at d10, d50, d90 and D(4,3) values were significantly increased by 67.12%, 47.72%, 33.18% and 42.01%, respectively; whereas, the specific surface area was significantly reduced by 38.39%, compared with the control sample. The TGA thermograms showed three steps of thermal degradation in which, the weight loss of Biofield Energy Treated sample in the first and second step was reduced by 5.82% and 16.09%, respectively, while, it was increased by 6.78% in the third step, compared to the control sample. The total weight loss in the treated sample was also reduced by 2.76%, along with slight alteration in the maximum thermal decomposition temperature, compared with the control sample. The DSC analysis showed the decrease in the melting temperatures of the 1st, 2nd and 4th peaks by 8.24%, 19.29%, and 0.61%, respectively, while 4.57% increase in the 3rd peak of the treated sample, compared with the control sample. The latent heat of fusion (ΔH) corresponding to the 1st, 2nd, 3rd and 4th peaks of the treated sample also showed alterations by -92.29, -86.29, 60.92, and 6.37%, respectively, compared with the control sample. The Trivedi Effect®-Consciousness Energy Healing Treatment might produce a novel polymorphic form of iron sulphate having increased crystallite and particle size along with enhanced thermal stability. It may help in improving the quality, safety and stability during the process of handling, storage, and shipment of the iron sulphate with better therapeutic response against iron deficiency anaemia.

Physicochemical, Thermal and Spectroscopic Characterization of the Energy of Consciousness Healing Treated Withania somnifera (Ashwagandha) Root Extract

Ashwagandha root extract is widely used in nutraceutical preparations due to its broad range of pharmacological activities. The objective of this study was to analyse the impact of Biofield Energy Treatment (The Trivedi Effect®) on the physicochemical, thermal and spectral properties of ashwagandha root extract by using various analytical techniques. The sample of ashwagandha root extract was divided into two parts in which one part was kept untreated and called as control sample; while the other part was provided with the Consciousness Energy Healing Treatment remotely by the Biofield Energy Healer, Mr. Mahendra Kumar Trivedi and termed as Biofield Energy Treated sample. The study reported that the particle size values at d10, d50, d90, and D (4,3) in the Biofield Energy Treated sample was significantly decreased by 9.23%, 9.04%, 11.86%, and 10.59%, respectively compared with the control sample. Thus, the surface area of the treated sample was significantly increased by 10.75% compared to the control sample. The PXRD analysis showed that the control as well as the Biofield Energy Treated samples was amorphous in nature. The DSC analysis showed that the onset evaporation temperature and latent heat of vaporization were significantly altered by 2.18% and-10.29%, respectively in the Biofield Energy Treated sample compared with the control sample. The TGA analysis indicated the four step thermal degradation of both the samples. The 1st, 2nd, 3rd, and 4th steps of thermal degradation of the treated sample showed an alteration in the weight loss by -6.59%, 1.97%, -1.80%, and -8.65%, respectively along with 0.81% reduction in the total weight loss, compared with the control sample. Besides, the maximum thermal degradation temperature (Tmax) in the control sample was observed at 234.17°C and 365.12°C for the two broad peaks, which was decreased by 1.73% and 0.82%, respectively compared to the control sample. The overall analysis suggests that the Energy of Consciousness Healing Treatment might enhance the solubility, absorption, and bioavailability profile of ashwagandha root extract along with altered thermal stability. Such altered properties might help in designing better pharmaceutical and nutraceutical preparations; thereby provide better therapeutic response against various diseases such as amnesia, arthritis, anxiety, cancer, impotence, neurodegenerative, and cardiovascular diseases.

Spectral characterization of tetradentate Schiff base complexes of N2O2 donor groups

Copper(II) complexes of tetra dentate Schiff bases N, N’ – disalicylidene – 1, 2 – phenylenediamine(H2dsp), N, N’ – disalicylidene – 3, 4 – diaminotoluene(H2dst), 4 – nitro - N, N’ – disalicylidene – 1, 2 – phenylenediamine(H2ndsp), N, N’ – disalicylideneethylenediamine(H2salen) have been synthesized and characterized by elemental analysis, electronic spectra, IR spectra, magnetic susceptibility measurement, EPR, CV and thermal studies. TG studies show that Cu(dsp) and Cu(ndsp) complexes thermally degrade in two steps and Cu(dst) and Cu(salen) in one step. Kinetic and thermodynamic parameters were computed from thermal decomposition data. The activation energies of both the thermal degradation step lie in between 52 – 74 kJ/mol .

Acesulfame complex compounds of some lanthanide group metal cations. Synthesis and characterization

Some rare earth metal cations (Eu3+, Tb 3+, Ho3+, Er 3+ and Yb3+) of the acesulfame ligand and complex compounds were synthesized by hydrothermal method. Elemental analysis, infrared spectroscopy, mass analysis and solid-state UV–vis spectroscopy methods were used for the structural characterization of these compounds. In addition, TGA curves were recorded to determine the thermal degradation steps and possible degradation products of complex structures. As a result of the analysis of the structures, it was determined that the load equivalence of the metal cations having +3 oxidation steps provided with three monoanionic acesulfame ligands included in the structure. Rare earth elements, which have high coordination due to their large radii, are thought to exhibit hexadecimal coordination in synthesized molecules. The coordination sphere is complemented by two acesulfame and 2 aqua ligands showing acidic -N and carbonyl oxygen binding to the bidentate. One acesulfame ligand is thought to be located outside the coordination sphere as a counter ion. According to the recorded TGA curves, all molecules were found to contain one hydrate water. It was determined by FT-IR analysis that all complex structures formed the metal oxides in the reaction vessels as thermal decomposition products.

Comparative isoconversional thermal analysis of Artemisia vulgaris hydrogel and its acetates; a potential matrix for sustained drug delivery

Artemisia vulgaris hydrogel (AVH) was acetylated (AAVH) and characterized by FTIR, CP/MAS 13C-NMR spectroscopic techniques and thermogravimetric analysis. Flynn–Waal–Ozawa model was used to investigate thermal degradation kinetics. Energy of activation (Ea) values of first and major thermal degradation steps were found to be 128.14 and 116.85 kJmol−1 for AVH and AAVH, respectively. Thermodynamic triplet, order of degradation reaction, integral procedural decomposition temperature (IPDT) and comprehensive index of intrinsic thermal stability (ITS) were also taken into account. In vitro caffeine release from AVH-based matrix tablets indicates potential of AVH for the development of oral delivery systems for sustained drug release.

Robust interface on ENR-50/TiO2 nanohybrid material based sol-gel technique: Insights into synthesis, characterization and applications in optical

In this work, the sol–gel technique was used to prepare a new organic–inorganic hybrid from Epoxidized Natural Rubber (ENR-50) and Titanium dioxide (TiO2) by blending different content of titania precursors (10, 30, and 50 wt%) with an ENR-50 matrix. A wide range of analyses was conducted to understand the nature of this hybrid and also to evaluate its potential uses in applications required high refractive index such as micro optical and optoelectronic devices. Results indicated that the ring-opening reaction of epoxide groups in ENR-50 increased with the increase of titania content in the hybrid resulting a strong bonding between titania and ENR-50 through TiOC bond, which was observed in FTIR spectrum at 1027–1028 cm−1. It is also observed a slight decrease in the intensity of the amorphous peak along with a new crystalline peak appeared at 2θ = 23 and 27° due to the crystalline nature of titania. The hybrids showed three thermal degradation steps in the range of temperature 76 to 769 °C due to the existence of the Ti moieties with the mixture of polymer chains, which in turn shifted the Tg at 24.3, 26.9 and 28.1 °C for the hybrid at 10, 30, and 50 wt% TiO2 compared to the Tg of ENR-50 at −18.4 °C respectively. The morphology of the ENR-50 showed clear changes during of the synthesis of ENR-50/TiO2 hybrids, these changes were proven by SEM, TEM, and AFM analyses. Uv–Vis results showed that the higher wavelength peak at 293 nm has shifted to 296, 298 and 300 nm for the hybrid at 10, 30, and 50 wt% TiO2 respectively due to the strong interaction between titania precursors and ENR-50 matrix. Furthermore, the hybrids showed good optical transparency in the visible light range.

Enhanced adsorption of Levofloxacin and Ceftriaxone antibiotics from water by assembled composite of nanotitanium oxide/chitosan/nano-bentonite.

A novel NBent-NTiO2-Chit nanocomposite has been synthesized from the crosslinking combination of nanotitanium oxide-chitosan (NTiO2-Chit) and nanotitanium oxide-bentonite (NTiO2-Bent) via formaldehyde. The characterization of NBent-NTiO2-Chit was confirmed by different instrumentations. The particle size (34-97 nm) and surface area (16.385 m2 g-1) were confirmed from the scanning electron microscopy and BET measurement, respectively. The FT-IR of NBent-NTiO2-Chit confirmed the presence of OH, N-H, Si-O-Al and Si-O-Si functional groups. Four thermal degradation steps were characterized from the TGA of NBent-NTiO2-Chit with a total loss = 23.514% in the temperature range 30-600 °C. The assembled nanocomposite enhanced the removal of two important classes of antibiotics including Levofloxacin (LEVO) Ceftriaxone (CFT) in the forms of Fluoroquinolone and Cephalosporin, respectively. The various factors that affected the percentage of extraction were applied and optimized such as pH, dosage, initial concentration of LEVO and CFT, contact time and interfering ions. Maximum percentage values of 90.2% (pH 4) and 93.5% (pH 5) for LEVO and CFT, respectively, were achieved at 10 min. The enhancement in removal percentage of LEVO to 92.4% was mainly established by increasing the dose of NBent-NTiO2-Chit to 60.0 mg. The extraction mechanisms of LEVO and CFT were positively explained by three models of adsorption isotherm including Langmuir, Freundlich and Temkin. The obtained correlation coefficients (R2) by Langmuir model were 0.952 and 0.987 for LEVO and CFT, respectively to offer excellent fit to the adsorption processes. The thermodynamics parameters of NBent-NTiO2-Chit were evaluated and referred that the reaction is spontaneous and endothermic. The kinetic studies of NBent-NTiO2-Chit with LEVO and CFT antibiotics were better fitted by the pseudo-second-order based on the acquired R2 values as 0.999 and 0.997 for LEVO and CFT, respectively. The results proved that the designed NBent-NTiO2-Chit was successively implemented for extraction of LEVO and CFT from industrial wastewater providing percentage values 83.2 and 79.0% using 10.0 and 150.0 ± 1.0 mg NBent-NTiO2-Chit, respectively.

Novel solid-state compounds of heavy rare-earth (III) picolinates. A pyrolytic study using: TG-DSC-IR, HSM-MS and GC-MS

Heavy trivalent lanthanides and yttrium picolinates were synthesized by complexation of basic rare-earth metal carbonates with an aqueous solution of picolinic acid. The novel compounds were obtained with the general formula Ln(L)3∙nH2O, where L is picolinate and n = 1.5 H2O (Dy, Ho, Yb, Lu and Y), 2 H2O (Tb and Tm) and 2.5 H2O (Er). The stoichiometry of the complexes was calculated through mass losses found using thermogravimetry (TG), complexometry and elemental analysis (EA). The thermal behavior in oxidative and pyrolytic atmospheres of the compounds was analyzed by simultaneous thermogravimetry - differential scanning calorimetry (TG-DSC). The gaseous products of the pyrolysis were determined throughout by monitoring the evolved species using TG-DSC couple to Fourier transform infrared spectroscopy (TG-DSC-IR), hot-stage microscopy mass spectrometry (HSM-MS), and gas chromatography-mass spectrometry (GC-MS). The obtained results validated mass loss assignments made using the TG curves. However, gaseous product analysis indicates the degradation processes are more complex than the thermoanalytical techniques suggest alone. This study used a GC-MS technique to identify the condensed gaseous products obtained during the second step of thermal degradation of the picolinate complexes. The analysis of the symmetric and asymmetric stretching frequencies of the carboxylate group in the IR spectra showed a monodentate bonding mode. The compounds were obtained in the amorphous state, as indicated by the powder x-ray diffractometry (PXRD) data.

Influence of modified starch and nanoclay particles on crystallization and thermal degradation properties of cross-linked poly(lactic acid)

Cross-linked poly(lactic acid) (PLA)/ maleated thermoplastic starch (MTPS)/ montmorillonite (MMT) composites were prepared by melt blending. Crosslinking was conducted by adding di-cumyl peroxide (DCP) in the presence of triallyl isocyanurate (TAIC) as co-agent. MTPS was produced by grafting maleic anhydride (MA) to thermoplastic starch in an internal mixer. DSC results demonstrated that crosslinking of PLA increased glass transition temperature (Tg) and reduced crystallinity. Presence of MTPS generally declined crystallinity despite of the relative effectiveness of nanoclay particles on enhancing the crystallinity of PLA matrix. Crosslinking of PLA caused significant improvement of thermal stability. Addition of MTPS decreased thermal stability of PLA. Presence of nanoclay enhanced the maximum temperature in final thermal degradation step. The non-isothermal kinetics of the degradation processes was assessed using two different integral methods. Results showed that crosslinking increased decomposition activation energy of PLA. However, addition of MTPS and nanoclay caused to decrease of activation energy.

Synergistic effect of alkyl lactate functional groups on properties of methacrylate polymers

In this work, four novel different alkyl lactate methacrylate monomers were synthesized through azeotropic esterification method by reacting methyl, ethyl, propyl and butyl lactates with methacrylic acid. The prepared monomers were polymerized through solution polymerization technique and both monomers and polymers were analyzed by FTIR, 1H NMR and 13C NMR spectroscopy techniques to elucidate the structure and to confirm their formation. Increasing the number of methylene units in alkyl lactate side chain decreases the glass transition temperature (Tg) of the polymers. Average molecular interchain spacing (〈R〉) of polymers was obtained from the wide-angle X-ray diffraction measurement and the values ranged from 6.26 to 7.18 A based on the length of alkyl lactate group. The prepared polymers showed hygroscopic property and their moisture absorption was in the range of 10–24% (w/w) depending upon the length of alkyl lactate moiety, relative humidity and time. These polymers have the potential for hydrogel applications owing to their increased moisture absorption capacity. Both polymethyl and propyl lactate methacrylate showed two distinct and prominent thermal degradations whereas polyethyl and butyl lactate methacrylates showed only a single distinct and prominent thermal degradation step. An interesting result of as-synthesized polymers showed odd–even chain length effect in the properties of 〈R〉, moisture uptake and thermal stability.