Hydrolysis of pentosans in bagasse pith

Work has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi-logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith. K₁ = 6.4 × 10⁵C^1.02 exp (?6378/T) K₂ = 10.7C^0.363 exp (- 2826/T)     

Synthesis,characterization, and application of new low‐cost ion exchangers

This paper represents a simple method for preparing and characterizing of low‐cost ion exchangers of sulfonated carbon prepared from Terminalia Chebula‐Retz., (family–combretaceae) as a source of cheap plant material blended with phenol‐formaldehyde as a crosslinking agent. The prepared ion exchange resins (IERs) are characterized by infrared (IR) spectral and thermal studies. All the important physicochemical properties of the ion exchangers have been determined. The synthesized resins have cation exchange capacity upto 1.84 mmol g^?1. The rational thermodynamic equilibrium constant (ln K) are calculated for H⁺ and Zn²⁺ exchanges on the resin having various amount of sulfonated Terminalia Chebula Retz. carbon (STCC). The thermodynamic parameters were calculated, and suitable explanations are given. It is concluded from the present study that PFR sample could be blended with 20% (w/w) of STCC, without affecting its physicochemical, spectral, and thermal properties. Hence blending with STCC will definitely lower the cost of the ion exchange resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4104–4113, 2006     

Synthesis and Properties of Synthetic Egyptian Corncob-Phenol Formaldehyde Cationic Exchanger

Studies have been carried out on the synthesis, composition, stability, and ion-exchange properties of cationic resins from poly-condensation of Egyptian corncobs (as a source of inexpensive and renewable material) with phenol in the presence of parafonnaldehyde as a crosslinking agent. These exchangers are stable in water, organic solvents, thermal treatment and mineral acids (1 M). The samples, having a cation-exchange capacity up to 3.22 mEq g^?1 of dry resin, are being introduced as a new cationic exchanger. The cationic exchanger shows a limited affinity for the binary separation of some divalent cations.     

Hydrolysis of pentosans in bagasse pith

Work has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi-logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith.      

Synthesis,Surface and Antimicrobial Activities of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants [C_nH_2n+1–O–CH₂–CH(OH)–CH₂–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? [ 3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2‐hydroxy‐1,3‐oxypropylene group [?CH₂–CH(OH)–CH₂–O–] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C_nH_2n+1–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? (n‐4‐n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.     

Adsorption of dyes onto bagasse pith using a solid diffusion model

The adsorption of four dyes (Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114) onto bagasse pith has been studied using an agitated batch adsorber. The variables studied were initial dye concentration and pith mass. A mathematical model has been developed based on external mass transfer and solid-phase diffusion. The model has been used to generate theoretical concentration–time decay curves, and these results were adjusted to experimental data by a best fit approach. The external mass transfer coefficients are 2.0 × 10^?3, 1.5 × 10^?3, 8.0 × 10^?4, and 5.0 × 10^?4 cm s^?1 and the solid diffusivities are 1.1 × 10^?8, 1.0 × 10^?8, 6.0 × 10^?9, and 3.0 × 10^?9 cm² s^?1 for Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114.     

Synthesis,characterization, and preliminary antimicrobial evaluation of bisphenol‐A formaldehyde resin coordinated with transition metal complexes of ethylenediamine

Coordination polymers containing bisphenol‐A, formaldehyde, and transition metal complexes of ethylenediamine [M(en)₂] were synthesized by the reaction of bisphenol‐A, formaldehyde, and M(en)₂ complex in alkaline medium, using M for Fe⁺³, Co⁺², Ni⁺², Cu⁺², and Zn⁺². The materials were characterized by elemental analysis, FTIR, UV–Vis, ¹H‐NMR spectra, TGA, and magnetic susceptibility measurement. The geometry of the central metal ions was determined by electronic spectral studies and magnetic moment measurement. The M N and C N bonds were confirmed by the IR spectra of the polychelates. The ¹H‐NMR spectra of the chelating resins confirmed polycondensation with well‐defined peaks for bridging methylene functions. Complexation studies with transition metal ions revealed effective coordination of the bisphenol‐A formaldehyde resin. The antimicrobial activities of these chelated resins were screened against E. coli, S. dysantrea (bacteria), and C. albicans, A. niger (fungi) by using agar well diffusion method. All the polymeric chelates show promising antimicrobial activities. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on Cesium Uptake by Phenolic Resins

Abstract

The selective removal of cesium by phenolic ion-exchange resins from highly salted alkaline radioactive solutions was studied. The resins were synthesized by alkaline polycondensation of phenol, resorcinol, catechol, and a resorcinol-catechol mixture with formaldehyde and characterized for their moisture regain, ion-exchange (H⁺→Na⁺) capacity, and distribution coefficient (K_D ) for cesium. The effects of open and sealed curing of the polymers on their properties were studied. The effect of Na⁺, NaOH, and Cs⁺ concentration on the uptake of cesium by resorcinol-formaldehyde resin was investigated, in particular. The chemical, thermal, and radiation stabilities of the polymers were also studied.     

Modification of cation exchange membrane by grafted poly(4-vinyl-N-methylpyridinium-iodide)

It is well known that cation exchange membranes, having a very thin layer of a cationic polyelectrolyte on the membrane surface, have preferential permselectivity for monovalent cations in a monovelent-divalent cations system. We studied the relationship between preferential permselectivity and molecular structure of the cationic polyelectrolyte. Grafted poly(4-vinyl-N-methylpyridinium-iodide) was used and was compared with poly(4-vinyl-N-methylpyridiniumiodide). The backbone polymers were poly(styrene-co-p-benzylstyrene) and poly(benzyl), onto which 4-vinylpyridine was grafted by anionic polymerization and then quaternized with CH₃I. The grafted poly(4-vinyl-N-methylpyridinium-iodide) is effective in making the cation exchange membrane preferentially permselevtive for Na⁺ - Ca²⁺ system and is more preferable than poly(4-vinyl-N-methylpyridinium-iodide) in terms of electric resistance of the membrane. However, the relationship between the molecular structure of the cationic polyelectrolyte and the durability of the preferential permselectivity is not clear.     

Cationic Ruthenium‐Cyclopentadienyl‐Diphosphine Complexes as Catalysts for the Allylation of Phenols with Allyl Alcohol; Relation between Structure and Catalytic Performance in O‐ vs. C‐Allylation

A new catalytic method has been investigated to obtain either O‐ or C‐allylated phenolic products using allyl alcohol or diallyl ether as the allyl donor. With the use of new cationic ruthenium(II) complexes as catalyst, both reactions can be performed with good selectivity. Active cationic Ru(II) complexes, having cyclopentadienyl and bidentate phosphine ligands are generated from the corresponding Ru(II) chloride complexes with a silver salt. The structures of three novel (diphosphine)Ru(II)CpCl catalyst precursor complexes are reported. It appears that the structure of the bidentate ligand has a major influence on catalytic activity as well as chemoselectivity. In addition, a strong cocatalytic effect of small amounts of acid is revealed. Model experiments are described that have been used to build a reaction network that explains the origin and evolution in time of both O‐allylated and C‐allylated phenolic products. Some mechanistic implications of the observed structure vs. performance relation of the [(diphosphine)RuCp]⁺ complexes and the cocatalytic role of added protons are discussed.     

Cationic surfactant-selective potentiometric sensors based on neutral ion-pair carrier complexes

Poly(vinyl chloride) (PVC) membrane electrodes to determine monomer concentrations of tetradecyltrimethylammonium ion (TTA⁺) and hexadecylpyridinium ion (HPy⁺) based on neutral ion-pair carrier complexes of tetradecyltrimethylammonium dodecyl sulfate (TTA⁺-DS⁻) and hexadecylpyridinium dodecyl sulfate (HPy⁺-DS⁻), respectively, are reported here. The electrodes exhibit a Nernstian slope of 59 mV per decade for TTA⁺ and a sub-Nernstian slope of 34.5 mV per decade for HPy⁺ ions. The TTA⁺ ion-selective electrode (ISE) and the HPy⁺-ISE can determine the monomer units down to concentrations as low as 4.0×10⁻⁴M and 1.66×10⁻⁵ M, respectively. The effect of various additives, such as the anionic polyelectrolyte sodium dextran sulfate and macrocyclic β-cyclodextrin, on the surface activity exhibited by the cationic surfactants TTA⁺-DS⁻ and HPy⁺-DS⁻, in the presence of background concentrations of NaCl was also examined with surfactant-selective sensors. The Gibbs free energy of micelle formation (ΔG _m ) of both surfactants in the presence of various additives was calculated and found to be less favorable with respect to an increase in the amount of additives due to less availability of cationic surfactant monomer units. The ion-pair complexes TTA⁺-DS⁻ and HPy⁺-DS⁻ were found to behave as selective carrier compounds in PVC membranes in determining the concentration of monomer units of both TTA⁺ and HPy⁺, respectively. The proposed sensors worked well at a fairly acidic pH of 1–6.5 with response time of 60 s. The sensors responded well to the surfactant ions even in the presence of additives at lower concentration. The lifetime of the sensors is 3 mon.     

Comparative Equilibrium Studies on the Sorption of Metal Ions with Macroporous Resins Containing a Liquid Ion-Exchanger

Abstract

The distribution of five metal ions (M ^m+) including Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) between dilute sulfate solutions and macroporous resins containing di(2-ethylhexyl) phosphoric acid (D2EHPA, HR) was investigated. Experiments were carried out as a function of aqueous pH, D2EHPA concentration in the resin phase, and temperature. The equilibrium data were numerically analyzed. It was shown that the sorption reaction could be described by assuming the formation of metal complexes with a general composition MR _m (HR) _n in the resin phase. For several systems a change of complex stoichiometry with temperature was observed and discussed. The apparent thermodynamic data for the formation of these complexes were also calculated.     

Ionic conductivity of unsaturated polyester resin networks containing LiCIO4

Poly(ethylene oxide) (PEO) 400-maleate-isophthalate resins have been prepared and LiCIO₄ dissolved in the resins before crosslinking with 30% of styrene, vinylpyrrolidone or vinylpyridine. The DC conductivities of the resins were measured and found to increase in the order vinylpyridine 〈vinylpyrrolidone〉 styrene for the same [EO]/[Li⁺] ratio ( = 50). For the styrene system σ = 3 × 10^?6Scm^?1 at ambient temperatures and for the vinylpyridine system σ = 1 × 10^?7 Scm^?1. The T_gs of the system were also measured using dynamic mechanical thermal analysis and were found to be very close (257-260 K). The above sequence was therefore attributed to stronger site-binding of lithium ions at the more polar comonomers. An interpenetrating network (IPN) consisting of the styrene-polyester and incorporating 40% PEO 400 was also prepared with[EO]/[Li⁺]ratios of 20 and 50. These gave ambient temperature conductivities of 1 × 10^?5 and 3 × 10^?5 Scm^?1, respectively.     

The Coagulation of Finely-Divided Ion Exchange Resins and the Use of the Coagulated Material for Rapid Ion Removal

Abstract

Finely-ground ion exchange resin particles remove ions from solution much more rapidly than the conventional-size beads. Such finely-divided solids form suspensions when added to aqueous solutions. A method was required for rapidly removing such suspensions once ion adsorption had occurred, and to this end it is shown that the particles (-400 mesh) can be completely coagulated within a few minutes by the addition of suspensions of oppositely-charged solids. Thus anion exchange resins are coagulated by cation exchange resins (200 to 400), montmorillonite (200), kaolin (30), charcoal (10), silica (10), and glass (5), the figures representing arbitrarily defined relative coagulating abilities. Coagulating power is shown to increase markedly with decreasing particle size. Most suitable for ion removal is a mixed finely-divided resin formed by coagulation of anionic and cationic resins from pure water. The mixed resin, when added to 1 liter of 3 × 10^?4 M sodium phosphate solution removes all the phosphorus within 2 min, and when added to 1 liter of 2.5 × 10^?4 M calcium chloride, removes over 90% of the calcium within 3 min.     

The Separation of Zn and Cu Using Chelating Ion Exchangers and Temperature Variations

Abstract

This paper reports the results of a study on the ion-exchange equilibrium of Cu ²⁺ and Zn ²⁺ at different temperatures on chelating ion-exchange resins: Amberlite IRC-718 (iminodiacetic acid based functional groups), VPC-1 (picolinic acid based) and thiourea-based resins. The separation factors and the conditional equilibrium constants of the ion-exchange reaction were determined in temperature range from 15 to 75 °C. An estimation of thermodynamic functions has also been carried out. Possibility of the separation of Cu and Zn mixture by dual temperature ion-exchange method has been demonstrated.     

Cationic RuII Cyclopentadienyl Complexes with Antifungal Activity against Several Candida Species

Fungal infections, including those caused by antifungal-resistant Candida, are a very challenging health problem worldwide. Whereas different ruthenium complexes were previously studied for their anti-Candida potential, Ru-cyclopentadienyl complexes were overlooked. Here, we report an antifungal activity assessment of three Ru-cyclopentadienyl complexes with some insights into their potential mode of action. Among these complexes, only the cationic species [Ru-ACN]⁺ and [Ru-ATZ]⁺ displayed a significant antifungal activity against different Candida strains, notably against the ones that did not respond to one of the most currently used antifungal drugs fluconazole (FCZ). However, no apparent activity was observed for the neutral species, Ru−Cl, thus indicating the important role of the cationic backbone of these complexes in their biological activity. We suggest that reactive oxygen species (ROS) generation might be involved in the mechanism of action of these complexes as, unlike neutral Ru−Cl, [Ru-ACN]⁺ and [Ru-ATZ]⁺ could generate intracellular concentration-dependent ROS. We also observed a correlation between the ruthenium cellular uptake, ROS generation and fungal growth inhibitory activity of the compounds. Furthermore, docking simulations showed that the CYP51 enzyme can form more energetically favorable complexes with [Ru-ATZ]⁺ than fluconazole (FCZ); this suggests that CYP51 inhibition could also be considered as a potential mode of action.     

Detoxification of sugarcane bagasse hemicellulosic hydrolysate with ion‐exchange resins for xylitol production by calcium alginate‐entrapped cells

This study describes the performance of four different resins, in sequence, to detoxify sugarcane bagasse hemicellulosic hydrolysate and to improve xylitol production by calcium alginate‐entrapped Candida guilliermondii FTI20037 cells under conditions of low oxygen concentration. The treatment resulted in a removal of 82.1% furfural, 66.5% hydroxymethylfurfural, 61.9% phenolic compounds derived from lignin degradation, 100% chromium, 46.1% zinc, 28.5% iron, 14.7% sodium and 3.5% nickel. On the other hand, the removal of acetic acid was not significant. A xylitol yield factor (Y_P/S) of 0.62 g g^?1 and a volumetric productivity (Q_p) of 0.24 g dm^?3 h^?1 were attained in the fermentation process for xylitol production from detoxified hydrolysate. Copyright © 2004 Society of Chemical Industry     

Structural development Of TMMA and SSQXN‐8 as porous chelating resins

Superfast kinetics of Nd⁺³, Eu⁺³, and Gd⁺³ ions were studied on the surfaces of N,N,N^\,N^\‐tetramethylmalonamide (TMMA) and silsesquioxane (SSQXN‐8) resins. TMMA and SSQXN‐8 were prepared by suspension polymerization and sol–gel routes, respectively. They were identified using elemental analysis, FTIR, H‐NMR, ¹³C‐NMR, MIP, and BET surface area. Kinetic investigations were performed in batch conditions and different models were used to fit the data; Boyd and Helfferich models were found the best. The diffusion of the ions through the resins were very fast and found to be in the order of 10^?16 m²/S. Effective diffusions of the studied ions were found to be 10^?15 order of magnitude and directly proportional to the kinetic energy of the transition state. ΔS* values from ?166.044 to ?179.297 J mol^?1 K^?1 were estimated as entropy stability factors of the system. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of a polyaminophosphonate and its evaluation as an antiscalant in desalination plant

The cationic monomer, N,N‐diallyl‐3‐(diethylphosphonato)propylammonium chloride, was cyclopolymerized in aqueous solutions using t‐butylhydroperoxide (TBHP) or ammonium persulfate (APS) as initiators to afford a cationic polyelectrolyte (CPE) having a (diethylphosphonato)propyl pendent. The CPE on acidic hydrolysis of the diester groups gave pH‐responsive polyzwitterionic acid (PZA) which on treatment with one and two equivalents NaOH gave zwitterionic/anionic polyelectrolyte (ZAPE) and dianionic polyelectrolyte (DAPE), respectively. The solution properties of the CPE, PZA, ZAPE, and DAPE were investigated in detail by viscometric technique. For the purpose of comparison, the solution properties of the polymers were correlated to a structurally similar polyzwitterion (PZ) having monoethylphosphonate and NH⁺ groups. When performance evaluation was carried out for application in reverse osmosis (RO) plants, DAPE at a concentration of 10 ppm in brackish water feed proved very effective as an inhibitor against calcium sulfate scale. POLYM. ENG. SCI., 54:166–174, 2014. © 2013 Society of Plastics Engineers     

Antibacterial activity of resin-containing triethylenetetramine side chains and/or thiol groups–metal complexes

Four chelating resins containing triethylenetetramine side chains and/or thiol groups were made from macroreticular 2,3-epithiopropyl methacrylate, styrene–divinylbenzene (DVB), or methyl methacrylate–DVB copolymer beads, and then the resins bearing metal ions such as Ag⁺, Cu²⁺, and Zn²⁺ were made. The antibacterial activity of the resins bearing metal ions against Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus) was investigated. The resins containing thiol groups showed the higher adsorption capacity for silver ions than for other metal ions. The resins, which contain both triethylenetetramine side chains and thiol groups, bearing silver ions (RE-TTA-Ag) exhibited high antibacterial activity against bacteria, especially E. coli, without the residual silver ions in water after contacting with bacteria. The activity of the RE-TTA-Ag did not decrease even after reusing several time. © 1996 John Wiley & Sons, Inc.