Sulphonic Groups Research Articles

Recyclable antimicrobial sulphonated poly (ether ether ketone) – copper films: Flat vs micro-pillared surfaces

The existence of bacteria and fungi on surfaces can be a serious threat to health causing numerous infections. With these microorganisms developing resistance over the years, there is an increasing need to develop surfaces that can kill or inhibit the growth of bacteria and fungi. In this work, we report the fabrication of sulphonated poly (ether ether ketone) (SPEEK) and its copper composite films as promising antimicrobial materials and investigated the effects of fabricating surface structures (micro-pillars) on the films. The fabricated films were systematically characterized and it was observed that both SPEEK and SPEEK – Cu films possessed antimicrobial properties which initially killed all of E. coli within 15 min of contact. Over longer times, as the films aged, the SPEEK – Cu film still achieved over 2 log (for flat film) and 4 log (for micro-pillared film) reduction of E. coli within 1 h of contact and it showed significant fungal growth reduction for Saccharomyces cerevisiae (yeast) and Aspergillus niger with 2 h of contact. Micro-pillared films had a larger water contact angle (131°) in comparison to flat films (64°) which thus rendered it hydrophobic. It was also observed that these micro-pillared films showed better antimicrobial properties and better copper release than flat as a result of better exposure of copper particles on the top surface of micro-pillars. The fabricated films were also thermally stable and exhibited tensile strengths ranging from 50 to 160 MPa depending on the surface morphology and copper content. Furthermore, the films were found to be recyclable by dissolution in sulphuric acid and re-casting to form new films with replenished sulphonic acid groups in the polymer matrix and restored antimicrobial properties.

Study on Interaction of Coomassie Brilliant Blue G-250 with Bovine Serum Albumin by Multispectroscopic

Aim of present study was to investigate the interaction of coomassie brilliant blue G-250 (CBBG-250) with bovine serum albumin (BSA) by the multispectroscopic methods. Fluorescence-data showed that the complex of BSA-CBBG-250 forming made the intrinsic fluorescence quenching of BSA by CBBG-250 interaction. BSA also could interact with CBBG-250 and the CBBG-BSA complexes formed in a molar ratio of 1:1. UV–Vis results displayed that the apparent binding (association) constant Ka of CBBG-250 with BSA was 5.03 × 104 (298 K), 3.04 × 104 (303 K), 2.84 × 104 (308 K) and 1.99 × 104 (313 K) L mol−1 at different temperatures, respectively. The enthalpy change (△H) and entropy change (△S) were respectively calculated to be − 45.32 kJ mol−1 and − 139.18 J mol−1 K−1, indicating that the hydrogen bonds and Van der Waals forces played dominant roles in the interaction. The results showed that the diphenylamine structure and amino acid residues in the Coomassie Brilliant Blue G-250 had a strong Van der Waals force. The phenyl sulphonic acid group undergoes electrostatic interactions and hydrogen bond interactions with basic amino acids; the compound Coomassie Brilliant Blue G-250 can form a stable complex with BSA.

Investigations of vegetable tannins as hair dyes and their interactions with pre-bleached hair fibres.

The aim of this work was to investigate an alternative hair-dyeing method with vegetable colourants as the tannins, as well as the impact of pre-treatment as the bleaching process. Untreated, 1, 2 and 3 times bleached hair tresses that were dyed with tannins in combination with metal salts were characterized. The wash fastness and the colour strength of the vegetable-dyed hair tresses were spectrophotometrically investigated. To determine the colour strength KS and the wash fastness of vegetable-dyed and pre-bleached hair tresses, a three-dimensional colour coordinate system - CIELab - which describes the visual spectra is used. The distance between two colours in the CIELab colour space is expressed by ∆E-values, which are used to identify the wash fastness of the vegetable dye. The hair tresses that had been 3 times pre-bleached showed the highest colour strength and the best wash fastness. The fixation of the tannin-mordant complexes on the hair fibre proceeded effectively just when the hair tresses were bleached before the dying process. It is suggested that the sulphonic acid groups, which increase after bleaching hair, interact with the tannin-mordant hair dye and lead to stronger cross-links between keratinous fibres and tannin-mordant complexes. It was observed that the colour strength of the vegetable-dyed tresses correlates with the bleaching process. The presented results demonstrate that the fixation of the vegetable tannin-mordant dying solution on the hair fibres succeed effectively on pre-bleached hair tresses.

Synthesis and Characterization of Ti-Nb2O5 Catalysts for Discoloration Reaction of Bromophenol Blue and Indigo Carmine Dyes

This work investigated the photodegradation of bromophenol blue (BPB) and indigo carmine (IC) dye under UV–Visible light using pure oxides of titanium and niobium, as well as TiO2-Nb2O5 oxides containing 0.5, 2.5 and 5 wt% of TiO2, prepared by wet impregnation of Nb2O5 with Ti tert-butoxide under inert atmosphere. The results of XRD and Raman spectroscopy showed the presence of anatase TiO2 phase and T-Nb2O5 phase with orthorhombic structure in the pure TiO2 and Nb2O5 oxides, respectively. The Nb2O5 oxides doped with TiO2 presented a T-Nb2O5 phase, but there was no formation of TiNb2O7. TiO2 anatase was observed in the mixed oxide with higher Ti content (5 wt% TiO2). A zeta potential analysis showed positive surface charge values for titanium oxide and negative for niobium oxide and mixed oxides. The addition of up to 5 wt% of the TiO2 fold the activity of Nb2O5 in the discoloration of both dyes. Pure TiO2 exhibits higher initial activity, which could be related to its positive PZC and higher attraction to sulphonic groups present in the dyes. Despite of the lower initial rate, 2.5 and 5% TiNb catalysts achieved full degradation of the dyes after 4 h of reaction.

Fibrillation and characterization of lignin-containing neutral sulphite (NS) pulps rich in hemicelluloses and anionic charge

The potential of neutral sulphite pulps from softwood with different yields (c. 58–84%) and high residual lignin contents (c. 10–25 wt%) was investigated as a raw material for lignin-containing cellulose nanofibrils (LCNFs) by following their fibrillation during grinding. It was found that the lower yield (58–65%) pulps needed two grinding cycles to produce fibrillated fibers with water retention values (WRV) as high as 400 g/g (at the energy consumption level of 1400 kWh/t). In contrast, the high yield (77–84%) pulps fibrillated more slowly, requiring five grinding cycles to reach comparable WRV values. Apparently, higher crosslinking degrees of lignin in the high yield pulps are hampering the fibrillation, although the high hemicellulose contents (21–24 wt%) and the high charge densities (200–350 µmol/g, originating from carboxylic and sulphonic acid groups) of the pulps were expected to enhance the fibrillation. Nevertheless, regardless of the different fibrillation behaviour, most of the pulps formed c. 10–15% of nanosized material below 30 nm and significant amounts of fibrils with size under 100 nm based on the centrifugation method and FE-SEM images. As the pulps were of moderate to high yield and fibrillated easily without any chemical or enzymatic pretreatments, they show promise for cost-efficient production of LCNFs. The nanopapers prepared from the fibrillated pulps showed tensile strengths (73–125 MPa) comparable with the nanopapers from high yield mechanical pulps, whereas the water contact angles (41°–58°) were closer the those of chemical pulps.

Investigation of a cation exchange membrane comprising Sulphonated Poly Ether Ether Ketone and Sulphonated Titanium Nanotubes in Microbial Fuel Cell and preliminary insights on microbial adhesion

Hydrothermally synthesized Titanium Nanotubes (TNTs) are sulphonated and characterized to confirm their morphological, physical and chemical characteristics. Different weight percentages (2.5, 5, 7.5 and 10 wt%) of Sulphonated TNTs (S-TNTs) are introduced into Sulphonated Poly Ether Ether Ketone (SPEEK) where the negative channels that form with the aid of sulphonic acid groups play an essential criterion for the improved proton conductivity and better water holding capacity. A tubular-designed Microbial Fuel Cell (MFC) of 300 mL volume is fabricated to test the potentiality of the self-assembled inorganic and functionalized Titanium nanotubes incorporated SPEEK membranes. SPEEK + 7.5% S-TNT exhibits a maximum power density of 121 mW m−2 with higher ion exchange capacity of 3.2 meq g−1 and lower internal resistance of 30 Ω. Biofouling investigation after 3 weeks of operation reveals that the optimized membrane displays better proton conductivity with an electrochemically stable biofilm without deteriorating the essential membrane characteristics. Preliminary microbial studies reveal the dominance of gram negative bacteria accelerating the rate of enriched extra-electrogen transfer (EET) to the anode enabling better MFC performance.

Evaluation of Kynurenine Behaviour on the Glassy Carbon Electrode Modified By Nafion Layer

Kynurenine is the first stable metabolite of tryptophan degradation formed via kynurenine pathway. Inflammation accompanying several disorders can activate kynurenine pathway, therefore increased level of kynurenine is associated with cancer, depression, schizophrenia, encephalopathy, HIV, dementia, amyotrophic lateral sclerosis, malaria, Alzheimer’s, and Huntington’s disease [1]. Kynurenine is an immuneregulatory molecule, which is further converted to other compounds showing biological activity, i.e. neuroprotective or neurotoxic effects on human cells. Studying properties of kynurenine is currently the important topic and might bring new information in context of biological processes [2].The presented work examines the potential of the cation exchange membrane Nafion® (used i.e. in voltammetric analytical approaches) to interact with kynurenine. Nafion is the polymer (ionomer) consisted of tetrafluorethylene or Teflon® backbone with perfluorovinyl ether groups terminated with sulphonate groups. The Nafion allows positively charged species (molecules or cations) to pass through, and at the same time excludes negatively charged compounds [3]. No studies have been conducted on the electrochemical behavior of kynurenine at Nafion covered glassy carbon electrode. Our preliminary studies have shown that kynurenine exhibits efficient adsorption on the Nafion layer, previously deposited by drop coating on the glassy carbon substrate.Voltammetric response of kynurenine strongly depends on the thickness of the Nafion layer. Thus, we attempted to evaluate the relationship between voltammetric signal of the molecule and morphology of the Nafion film deposited in different ways on the glassy carbon substrate (flat and rod electrode). For comparison several different approaches have been utilized for Nafion deposition, i.e. layer of varied thickness of Nafion were deposited on the rod carbon glassy electrode (CGE) or different withdrawal speed of the electrode from the solution of varied concentration of polymer was applied. The great benefit of this technique is possibility to control the thickness at a very high precision level on the whole electrode surface. The morphology surface electrode (roughness and waviness) both with flat and rod shape before and after Nafion deposition were evaluated by optical profilometer, mechanical profilometer, and atomic force microscopy. Moreover, Nation layer thickness on the rod GCE was determined by laser scan micrometer. Morphology characteristic of flat GCE was combined with chemical analysis at atomic and molecular level using complementary methods, such as: TOF-SIMS (time of flight secondary ion mass spectrometry) and XPS (X-ray photoelectron spectrometry). In addition, we propose new methodology for in situ molecular analysis of the rod CGE/Nafion after kynureine adsorption. It combines TOF-SIMS with cyclic voltammetry (CV). In this fashion CGE/Nafion was withdrawn at constant speed from electrolyte contained kynurenine, whilst CV measurements were conducted. When CV experiment was finished, samples were transferred to TOF-SIMS instruments and chemical analysis of different segments with area 100x100 um2 along length of rod were conducted. In that way molecular analysis of every segment surface CGE/Nafion corresponding to applied potential was performed.The results presented here provide new insights in analytical electrochemistry in case of kynurenine behavior on Nafion layer.[1] Y. Chen, G.J. Guillemin, Kynurenine Pathway Metabolites in Humans: Disease and Healthy States, Int J Tryptophan Res. 2009; 2: 1-19.[2] I. Sadok, A. Gamian, M. Staniszewska, Chromatographic analysis of tryptophan metabolites, J Sep Sci. 2017; 40(15):3020-3045.[3] R.K. Nagarale, G.S. Gohil, Vinod K. Shahi, Recent developments on ion-exchange membranes and electro-membrane processes, Adv. Colloid Interface Sci. 2006; 119: 97-130.

Vinylidene chloride- and styrene-based sulphonate-containing copolymers

Bare polyvinyl chloride (PVC) and polyvinylidene chloride are not commercially used due to their high softening point (185–200 o С ) and the absence of a suitable solvent for obtaining coatings (films) from their solutions. Therefore, vinyl chloride and vinylidene chloride are mainly applied in the production of copolymers having a lower pour point and better solubility as compared to homopolymers. Polymer materials based on copolymers of vinyl chloride and vinylidene chloride are widely used in a number of industrial applications. Recent research has been focused on monomer rafting onto a vinyl chloride and vinylidene chloride copolymer base by the formation of free radicals as a result of the transfer reaction of a chlorine atom to an initiating agent followed by sulphonation. Membranes obtained from solutions of grafted copolymers possess high proton conductivity values resulting in their perspective application for fuel cell manufacture. In order to obtain such membranes, it is necessary to carry out studies on the synthesis of vinylidene chloride copolymers and the substitution of chlorine atoms with sulphonic acid groups in these copolymers. In the framework of this work, vinylidene chloride and styrene copolymers were obtained by radical copolymerisation. The substitution of chlorine atoms by sulphonic acid groups in the synthesised copolymer was studied. The composition and structure of the copolymers were characterised using elemental analysis and IR spectroscopy data. The co-polymerisation values indicate a greater reactivity of styrene in comparison with vinylidene chloride. The interaction of a vinylidene chloride copolymer and styrene with sodium sulphide is accompanied by dehydrochlorination of vinylidene chloride units. The spatial modified copolymer structures are generated by double bonds formed as a result of elimination in a macromolecule.

MODIFICAÇÃO QUÍMICA DO POLIPROPILENO ATRAVÉS DA INTRODUÇÃO DE GRUPOS SULFÔNICOS PARA APLICAÇÃO COMO CATALISADOR EM REAÇÕES DE ESTERIFICAÇÃO

CHEMICAL MODIFICATION OF POLYPROPYLENE THROUGH THE INTRODUCTION OF SULPHONIC GROUPS FOR APPLICATION AS CATALYST IN ESTERIFICATION REACTIONS. In this work, the chemical modification of pristine polypropylene was carried out through sulfonation reactions with concentrated sulfuric acid (PPS1) and fuming sulfuric acid (PPS2), for production of heterogeneous catalysts used in esterification reactions. Fourier transform infrared spectroscopy, elemental analysis, degree of substitution and ion exchange capacity showed that both sulfonation agents were effective to promote the functionalization of polypropylene, with the fuming sulfuric acid capable of promoting a greater chemical modification. The materials catalytic activity in esterification reaction of oleic acid with methanol was evaluated at 100 ºC, methanol: oleic acid molar ratio of 78:1 and with 5 wt% of catalyst (referred to oleic acid weight). It was observed that reaction catalyzed by PPS1 converted 68.02% of oleic acid to methyl oleate in 3 hours of reaction, while PPS2 reached 86.47% conversion in five hours, showing even greater catalytic efficiency than the commercial ion exchange resin, Amberlyst 15. Therefore, the conditions employed for the sulfonation of polypropylene were satisfactory to produce materials with acid characteristics necessary to catalyze the esterification reaction of oleic acid with methanol.

Synthesis, characterization and application of S-TiO2/PVDF-g-PSSA composite membrane for improved performance in MFCs

Sulfonated titanium dioxide (S-TiO2) was prepared by the grafting of sulfonic groups onto TiO2, and doped into the PVDF-g-PSSA as a highly efficient inorganic additive, thus achieving simultaneous improvement of the proton conductivity and anti-fouling property of the synthesized S-TiO2/PPSSA proton exchange membrane (PEM). The S-TiO2/PPSSA membrane was implemented in microbial fuel cell (MFC) for the first time, and its physicochemical properties and performance in MFC were studied. A new technique of combining Quartz crystal microbalance with dissipation with membrane spin-coated sensors made by a spin coating method was utilized to provide an insight into the anti-fouling property of the prepared membranes. The implementation of Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy demonstrated TiO2 was successfully introduced into the sulphonic groups. The S-TiO2/PPSSA-5.0 membrane has a significant increase in the water uptake (40.9%) and proton conductivity (0.067 S/cm) compared with the PVDF-g-PSSA membrane. QCM-D results indicated that it has better anti-fouling property than pristine membrane and Nafion 117. Moreover, the MFC with the S-TiO2/PPSSA-5.0 membrane exhibited a maximum power density of 130.54 mW/m2, very close to that of Nafion 117 (132.02 mW/m2), but had the highest COD removal of 91% and least bio-fouling adsorption. These results demonstrate that the blending of sulfonated organic polymers and sulfonated inorganic additives can improve the electrochemical and anti-fouling properties of the composite membranes, which is a new concept for the preparation of PEM suitable for MFC. The S-TiO2/PPSSA-5.0 composite PEM is an appropriate candidate separator for the large-scale application of MFCs.

Synthesis and characterisation of PVDF-co-HFP/sTiO2 composites polymer electrolyte membranes

The Polyvinylidene fluoride (PVDF) can be combined with hexafluoropropilene (HFP) as to manifest a co-polymer called PVDF-co-HFP polymer. The PVDF-co-HFP polymer can be used as a proton exchange membrane due to its excellent mechanical strength, chemical resistance and thermal stability. It is, however, necessarily to modify the PVDF-co-HFP polymer, as an alternative to Nafion polymer membrane, by adding sulphonate groups via sulfonation and inorganic oxides such as TiO2 via oxide mixture. The research aimed to make a fuel cell membrane using PVDF-co-HFP polymer and study the effect of sulfonated TiO2 (sTiO) on the membrane to increase proton conductivity. PVDF-co-HFP membrane was prepared by which adding sTiO2 particles before it was sulfonated using 97% H2SO4. The sulfonation degree value was determined using the titration method while the proton conductivity was determined using the four-line probe. The membranes were characterised using SEM-EDX to see surface morphology and membrane composition, FTIR to confirm the presence of the -SO3H group. The results of SEM show that TiO2 particles are scattered on the surface of the membrane. EDX and FTIR results showed that sulfonation was successful in the presence of S elements by 0.77% and wavelengths 1143.2 and 1208.8 cm−1 by confirming the presence of the S=O group. The PVDF-co-HFP membrane with the addition of 3% sTiO2 particles with a sulphonation time of 6 h at 80 °C gave the best result with a proton conductivity value of 4.3 × 10−3 S cm−1 and a saturation grade of 19.37%. Thus, the PVDF-co-HFP/sTiO2 membrane can be used as a proton exchange membrane in the fuel cell.

Removal of Methylene Blue and Basic Yellow 28 Dyes from Aqueous Solutions Using Sulphonated Waste Poly Methyl Methacrylate

This work focuses on two different environmental problems: the recovery of plastic wastes PMMA (W PMMA) and their application in the removal of textile dyes Methylene Blue (MB) and Basic Yellow 28 (BY28) in aqueous solutions. The selected waste plastic was upgraded to produce an adsorbent suitable for dyes removal. For that, the material was grinded cryogenically up to a particle size of less than 100 μm and treated with sulfuric acid. The sulphonated waste PMMA (SW PMMA) was characterized by FTIR, scanning electronic microscopy (SEM) and chemical composition analysis (C, H, N, O and S content). The formation of sulphonic groups in the material after sulphonation reaction has been successfully demonstrated by FTIR, and can be observed mainly in the region 3087 cm−1 to 3657 cm−1, where an intense band bound to the stretching of the SO3H appeared; another absorption band appeared in the region from 1138 to 1271 cm−1 that corresponds to the symmetric stretching of the SO2 group. The effects of solution pH, initial dyes concentration, adsorbent dose and temperature were studied in batch experiments. The obtained data showed that SW PMMA adsorbent exhibit significant adsorption capacities of 97.09 mg g−1 and 222.22 mg g−1 for MB and BY28, respectively. The complete removal of MB and BY28 on the SW PMMA was achieved in less than 45 min. The Langmuir, Freundlich and Temkin models were applied and it was found that the equilibrium data could be satisfactory fitted to Langmuir adsorption isotherm. The kinetic study showed that the pseudo second order kinetic model correlates the experimental data. Furthermore, the thermodynamic parameters were determined for both dyes. As a result, the negative values of Gibbs free energy ∆G° indicated the spontaneity of the adsorption of MB and BY28 by SW PMMA. The negative values of ∆H° revealed the exothermic nature of the process and the negative values of ∆S° suggest the stability of MB and BY28 on the surface of SW PMMA.

Vibrational spectra study of p-sulfonatocalix[4]arene containing azobenzene groups

The FTIR and FT Raman spectra of p-sulfonatocalix[4]arene acid, having azobenzene groups (FA), and its tetrasodium salt (S) were studied. Vibrational spectra of acid and its salts were calculated using the DFT method. The energy differences between E- and Z-forms of azobenzene groups in FA and S are 53.2 and 30.8 kcal/mol, respectively.The p-sulfonatocalix[4]arene is in cone conformation with a cyclic system of hydrogen bonds. The strength of the hydrogen bonds is lower in the salt molecule. The orientation of the aromatic units in the acid and salt is different. The assignment of the bands in the experimental vibrational spectra of the calixarenes was carried out by calculating the contributions of the internal coordinates to the potential energy. We identified characteristic bands for different conformations of the azobenzene groups. The analysis of molecular orbitals shows that HOMO is localized on aromatic units and that LUMO is associated with sulphonate groups.

Researches Concerning Chemical Modifications of Hair Keratin

The work presents chemical procedures used to obtain a film or a hydrogel after hydrolyze treatment of hair at the temperature of 150oC and the pressure of 4.9 atm. In order to obtain the hydrogel, this treatment is followed by a stage of oxidation with hydrogen peroxide, and a stage of reduction with Na2S2O4 or, in another variant, a stage of oxidation with hydrogen peroxide and a treatment with NaOH in alcoholic medium, to form natrium cationic groups. The protein chains with sulphonic groups and natrium cations determine opposite electrostatic interactions, with the formation of a polymer loop that incorporate water. The evaluation of formed hydrogel was carried out by determining the swelling degree. We have used optical and SEM photomicrographs to determine morphological organization, and EDAX micropictures for chemical modifications. A cellulose film realized by growing Gluconoacetobacter xylinus bacteria was used as control sample.

Vibrational spectroscopy of Fe tetrakis(4-sulphonatophenyl) porphyrin encapsulated within the metal organic framework HKUST-1

The ability to mimic catalytically diverse heme proteins through the encapsulation of iron porphyrins within the cavities of porous metal organic frameworks (MOFs) is a new approach to bioinspired materials. The encapsulation of Fe(3+)tetrakis(4-sulphonatophenyl)porphyrin (Fe4SP) within the octihemioctahedral cavities of HKUST-1 demonstrates site specific heme encapsulation within a MOF. The Fe4SP@HKUST-1 exhibited heme protein like peroxidase activity and crystallographically resolvable Fe4SP chromophores. Here, the vibrational structure of the encapsulated Fe4SP is examined using Raman and FTIR spectroscopies. The data reveals minimal structural perturbations upon encapsulation which is critical to the retention of heme catalytic properties in metallo-porphyrin based bioinspired MOFs. The FTIR data indicate non-covalent interactions involving the porphyrin peripheral sulphonic acid groups and the Cu paddle wheel clusters serving as the nodes within the framework.

Synergistic adsorption-photocatalysis processes of graphitic carbon nitrate (g-C3N4) for contaminant removal: Kinetics, models, and mechanisms

The synergy between adsorption and photocatalysis has been well recognized in contaminant photodegradation; however, the governing mechanism is still not clear. The main objective of this work is to understand the kinetic processes of synergic adsorption-photocatalysis of graphitic carbon nitrate (g-C3N4), a visible light responsive photocatalyst with a planar graphitic-like structure, in organic contaminant removal. An anionic dye Reactive Red 120 (RR120), which has six sulphonate groups and a complex aromatic molecular structure, was selected as a model contaminant compound. A range of experiments were conducted to determine the kinetics of adsorption, photodegradation, and the integrated process. Various kinetic models were used to simulate and interpret the experimental data and thus to unveil the governing mechanisms. The integrated adsorption and photodegradation of the dye by g-C3N4 was mainly controlled by: 1) adsorption of dye onto g-C3N4 surface, 2) photodegradation of dye in bulk solution, and 3) photodegradation of adsorbed dye on g-C3N4 surface. Both experimental and modeling results showed that the adsorption kinetic rate (3.37 min−1) was faster than the photodegradation kinetic rates. In addition, the surface photodegradation kinetic rate of adsorbed dye (0.149 min−1) was faster than that in solution (0.005 min−1). Adsorption process thus can promote the photodegradation of contaminants by g-C3N4. On the other hand, photodegradation of dye-laden g-C3N4 regenerated its adsorption capacity for multiple times, suggesting photocatalysis process can also promote the adsorption of contaminates on g-C3N4.

Chemoselective synthesis of bis(indolyl)methanes using sulfonic acid-functionalized chitosan

Herein, we describe the electrophilic substitution reaction of indole with aldehydes and ketone using sulphonic acid functional group containing chitosan for the synthesis of bis(indolyl)methanes. The reaction is chemoselective affording a product from aldehydes and indole. The catalyst can be reused up to three times without great loss in yields. Hence, chitosan–SO3H (CTSA) proved to be a heterogeneous, efficient, chemoselective, and reusable catalyst for the synthesis of bis(indolyl)methane derivatives.

Preparation and characterization of sulphonated bio-adsorbent from waste hawthorn kernel for dye (MB) removal

In this study, hawthorn kernel (HK), obtained from agricultural waste, which is eco-friendly and low cost material was selected as bio-adsorbent to remove of methylene blue (MB) from aqueous solutions. Since hawthorn kernel has low adsorption capacity, a new hawthorn-based bio-adsorbent having sulphonic acid groups (SHK) was prepared by activation using sulfuric acid with a very simple method. The optimal activation conditions were determined as 6 h, 85 °C, in 18 M sulfuric acid, with a sample/acid ratio of 1/5 (mass/volume). To determine the basic properties such as chemical structure, porosity and surface properties of the HK and SHK, they were characterized by Boehm Titration, BET, FTIR, SEM-EDX, XRD and pHpzc methods. Also, the thermal behavior of both adsorbents was examined by TGA. It was observed that activation has improved the thermal stability and also caused more amorphous structure. Optimum adsorption conditions were determined considering the amount of adsorbent, solution pH, MB initial concentration, and contact time and temperature parameters. Activation significantly changed the surface properties of the HK such as total acidity, functionality, porosity and surface pH. For MB adsorption on both adsorbents, pseudo-second-order kinetic model was found to be appropriate to explain kinetic behavior and equilibrium data fitted better to the Langmuir isotherm model. The maximum MB adsorption capacities of HK and SHK were calculated as 49.5 and 151.5 mg/g, respectively. It was determined from the calculated thermodynamic parameters that the adsorption of MB onto HK is spontaneous at low concentrations and high temperatures, but the adsorption of MB onto SHK is spontaneous at both high concentrations and low temperatures. After reusability studies which were carried out with 100 mg/L MB for five times, the SHK lost about 1% of its removal efficiency. As a result it was observed that SHK could be used as an efficient adsorbent for MB removal from aqueous solutions.

Influence of dye structure and temperature on the adsorption of acid dyes onto polyamide 6 knitwear

In this research, the influence of dye structure and dyeing temperature on the adsorption of acid dyes onto polyamide 6 knitwear (PA 6) was studied. Three acid dyes with different amounts of sulphonic groups, namely C. I. Acid Red 88, C. I. Acid Red 14, and C. I. Acid Red 18 were used. Dyeing was performed in a Launder-ometer apparatus at 40°C and 60°C, at pH 4. The samples were taken out of the apparatus at different time intervals. The results showed that both dye structure and dyeing temperature affected the adsorption of acid dyes onto PA 6 knitwear. The rate and quantity of adsorption increased with an increase in dyeing temperature and a decrease in the number of sulphonic groups in dyes.

Grafting of Heparin on Blend Membrane of Citric Acid Crosslinked Chitosan/Polyethylene Glycol-Poly Vinyl Alcohol (PVA-PEG)

Heparin, an active sulfate group material, grafted onto blend membrane citric acid cross-linked chitosan/poly (vinyl alcohol)-poly(ethylene glycol) (PVA-PEG) to improve the membrane properties. The physical tests shown that grafting reaction of citric acid crosslinked chitosan increased the mechanical strength and membrane swelling. The permeability test results, it was found that the grafted chitosan membrane was improved permeability of both urea and creatinine as compared to chitosan pure and chitosan crosslinked membrane. The negative charge of the sulphonate group of heparin increased the number of the active side of the carrier in the membrane, which then correlated to the membrane’s permeability process.