Saccharification of bagasse pith

Work is reported here on a process for the saccharification of bagasse pith, as the second part of a study of bagasse processing aimed at establishing an integrated industry. A method for pentose preparation from bagasse pith is designed on the basis of the conclusions reached in the first part of the study. It is preferable to Scholler's process in recovery of sugar and in concentration of the sugar solution. A process for glucose production from pentose-exhausted cellulosic residue is also developed to avoid the difficulties encountered in the Udic-Rheinau process. It seems to be a promising continuous process capable of giving a higher yield of glucose with less acid at a higher speed and affording favourable conditions for crystallising the dissolved glucose.     

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.      

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)     

Adsorption of basic dyes from model aqueous solutions onto novel spherical silica support

Removal of CI Basic Blue 9 or CI Basic Red 5 from model aqueous solutions has been studied with spherical silica precipitated in an emulsion system used as an adsorbent. The process of removal of the dye impurities has been studied for the dyes in a wide range of concentrations (50–2000 mg dm⁻³) in model systems. The degree of dye adsorption, chemical stability of the pigments obtained and their detailed physicochemical and morphological characterisation have been ascertained. In particular, the dye removal method proposed has been found to be highly effective in removing CI Basic Blue 9 (99.9%). The degree of dye extraction from the silica (SiO₂) surface at the dye concentration in the model solutions in the range 1000–2000 mg dm⁻³ did not exceed 1.0%. The pigment composites produced are characterised by high uniformity of the particles (polydispersity index = 0.005) with the diameters ranging from 360 to 510 nm. The pigment particles are spherical in shape and of intense blue or red colour.     

The Adsorption of basic dye onto silica from aqueous solution-solid diffusion model

The adsorption of Basic Blue 69 dye onto silica in a batch adsorption system has been studied. A two resistance mass transfer model has been developed based on film resistance and homogeneous solid phase diffusion. An analytical solution is presented and experimental results and theoretical data are in good agreement, for a wide range of operating conditions, using a single external mass transfer coefficient and a single effective solid diffusivity. The variables investigated are: initial dye concentration, solid/liquid ratios and adsorbent particle size range. Under constant agitation conditions almost all data can be correlated using a film mass transfer coefficient of 2.0 x 10^?4 cm sec^?1 and a diffusion coefficient of 1.2 x 10^?9 cm² sec^?1.     

Nitrogen containing additives in soda pulping of bagasse pith

Unbleached soda pulp was prepared from Egyptian bagasse pith by varying the alkali concentration and the time of heating at the boiling point of the liquor under atmospheric pressure. A linear relationship was observed between the dissolved pith and the dissolved lignin. Pulping with alkali concentration higher than 10% but not exceeding 16% was more effective, since more delignification took place with lower dissolved pith percentage. p- And m-nitrobenzoic acids and also hydroxylamine hydrochloride had a slight or no effect on the yield of the pulps. The alkali solubility percentage of the pulps prepared in the presence of any of the additives was lower than the control pulp. The delignification was enhanced more on the addition of hydroxylamine hydrochloride than p-nitrobenzoic acid, while m-nitrobenzoic acid seemed to have no effect. The yield of the pulps thus prepared, as determined by weighing, showed lower values than those determined by a chemical method. The soda delignification rate was shown to be proportional to the amount of unremoved lignin and the concentration of alkali in the liquor. The delignification reaction was found to follow approximately first-order kinetics.     

Adsorption of anionic amphiphilic polyelectrolytes onto amino-terminated solid surfaces

The adsorption behavior of several amphiphilic polyelectrolytes of poly(maleic anhydride-alt-styrene) functionalized with naphthyl and phenyl groups, onto amino-terminated silicon wafer has been studied by means of null- ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The maximum of adsorption, Γ_plateau, varies with the ionic strength, the polyelectrolyte structure and the chain length. Values of Γ_plateau obtained at low and high ionic strengths indicate that the adsorption follows the “screening-reduced adsorption” regime. Large aggregates were detected in solution by means of dynamic light scattering and fluorescence measurements. However, AFM indicated the formation of smooth layers and the absence of aggregates. A model based on a two-step adsorption behavior was proposed. In the first one, isolated chains in equilibrium with the aggregates in solution adsorbed onto amino-terminated surface. The adsorption is driven by electrostatic interaction between protonated surface and carboxylate groups. This first layer exposes naphtyl or phenyl groups to the solution. The second layer adsorption is now driven by hydrophobic interaction between surface and chains and exposes carboxylate groups to the medium, which repel the forthcoming chain by electrostatic repulsion. Upon drying some hydrophobic naphtyl or phenyl groups might be oriented to the air, as revealed by contact angle measurements. Such amphiphilic polyelectrolyte layers worked well for the building-up of multilayers with chitosan.     

Mixture diffusion of sulfonated dyes into cellulose membrane. I. Application of parallel diffusion model to binary system of acid dyes with small affinity onto cellulose

Transport phenomena of a binary mixture of dyes with a small affinity onto cellulose into a water-swollen cellulose membrane were studied at 55°C. The results were analyzed on the basis of a parallel transport theory of surface and pore diffusion. The diffusion of dye molecules in a binary dye system could be described by the parallel diffusion model. Although existence of the other dye decreased the equilibrium adsorption of both dyes onto cellulose, the surface and pore diffusivities for the model of both dyes were same as those in the single dye system. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2175–2181, 1997     

Adsorption thermodynamics and diffusion of disperse anthraquinone dyes in acetate fibre

Diffusion coefficients, thermodynamic parameters and adsorption equilibrium isotherms of some anthraquinone dyes for acetate fibre are reported. The chemical constitution seems to be more important than the size factor in determining dye diffusion into the interior of the fibres. The activation energies of diffusion decreased strongly when o-dichlorobenzene was present, due to the plasticising effect of carrier. Nernst partition isotherms were obtained, up to saturation. Substantivity decreased when water-solubilising groups are present in the molecule.The aqueous solubilities and heats of solution have been measured; the higher ΔH_w values were found for the derivatives which can form intermolecular hydrogen bonding in the crystalline state.     

Synthesis and studies of egyptian bagasse pith phenol formaldehyde cationic exchangers

The article is concerned with a simple method for preparing cationic resins from polycondensation of Egyptian bagasse pith (as a source of cheap and renewable material) with phenol and paraformaldehyde as a cross-linking agent. Optimum principal reaction conditions of the preparation and properties are determined and compared with resin without bagasse pith content. The Synthesized resins are stable in water, organic solvents, thermal treatment, and mineral acids (1M). The sample having a cation exchange capacity up to 3.92 meq g^?1 of dry resins are being introduced as new cationic exchangers. The synthesized resins are used in the study of the possible separation of univalent cations. The rational thermodynamic equilibrium constants (In K) are calculated for Li⁺ ?Na⁺ exchanges on the resins having a various amount of bagasse pith. The thermodynamic parameters are computed and suitable explanations are described. © 1994 John Wiley & Sons, Inc.     

Adsorption of acid dye onto woodmeal by solid diffusional mass transfer

The adsorption of Telon Blue (Acid Blue 25) dye onto wood has been studied using an agitated batch adsorber. The variables studied include agitation, initial dye concentration, wood mass, wood particle size and dye solution temperature. Isotherms were measured and the isotherm parameters were determined.

A mathematical model has been developed using the basis of the model proposed by Mathews and Weber Jr. This model is based on external mass transfer and solid-phase diffusion, and has been used to generate theoretical concentration—time decay curves. The results of the model were adjusted to the experimental data using a ‘best fit’ approach. The external mass transfer coefficient was found to vary with the degree of agitation, and consequently all other variables were considered at a constant agitation speed of 400 rev min⁻¹. A good agreement between the theoretical generated and the experimental concentration—time decay curves was achieved using a constant external mass transfer coefficient, 0.30 × 10⁻³ cm ⁻¹, and a constant solid-phase diffusivity, 0.200 × 10⁻⁸ cm² s⁻¹, for varying initial dye concentrations as well as wood mass. In experiments where the particle diameter was varied, a constant external mass transfer coefficient was sufficient to describe the system, but a decreasing diffusivity was required with increasing particle size. To simulate the effect of varying temperature, both external mass transfer coefficient and diffusivity were varied.     

Adsorption of acid dyes using polyelectrolyte impregnated mesoporous silica

Cationic polyelectrolyte, PDDA (Poly(diallyldimethylammonium chloride)), was impregnated on mesoporous silica SBA-15 (PDDA/SBA-15) and amorphous conventional silica (PDDA/CS) supports. Acid dye adsorption characteristics, such as adsorption kinetics, adsorption isotherms, maximum adsorption capacity, and breakthrough curves of the prepared PDDA/SBA-15 and PDDA/CS adsorbents, were examined by batch and column adsorption techniques where the Acid Violet 17, Acid Red 44, and Acid Blue 45 were used as target adsorbates. PDDA/SBA-15 adsorbent showed fast adsorption kinetics of less than 10 min and much higher adsorption capacities compared to PDDA/CS due to large pore sizes, ordered cylindrical pore structures, and high amount of impregnated PDDA. Results from batch and column experiments showed that practical use of PDDA/SBA-15 adsorbent for effective removal of acid dyes from aqueous solution would be possible. Polyelectrolyte impregnation method was suggested as a simple method for the development of adsorbent with large pore diameters and efficient adsorption characteristics.     

Adsorption kinetics and mechanism of cationic methyl violet and methylene blue dyes onto sepiolite

The use of low-cost and ecofriendly adsorbents was investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. Sepiolite was used as an adsorbent for the removal of methyl violet (MV) and methylene blue (MB) from aqueous solutions. The rate of adsorption was investigated under various parameters such as contact time, stirring speed, ionic strength, pH and temperature for the removal of these dyes. Kinetic study showed that the adsorption of dyes on sepiolite was a gradual process. Quasi-equilibrium reached within 3 h. Adsorption rate increased with the increase in ionic strength, pH and temperature. Pseudo-first-order, the Elvoich equation, pseudo-second-order, mass transfer and intra-particle diffusion models were used to fit the experimental data. The sorption kinetics of MV and MB onto sepiolite was described by the pseudo-second-order kinetic equation. Intra-particle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. The diffusion coefficient, D, was found to increase when the ionic strength, pH and temperature were raised. Thermodynamic activation parameters such as ΔG¹, ΔS¹ and ΔH¹ were also calculated.     

Film‐surface diffusion during the adsorption of acid dyes onto activated carbon

A mass transport model has been developed and applied to the adsorption of three acid dyes onto activated carbon in three single component systems. The mass transfer model is based on two rate controlling mass transfer steps, namely external film mass transfer and homogeneous solid‐phase surface diffusion (HSD). Almost all previous film‐HSD models have been based on numerical solutions to the diffusion equation using orthogonal collocation or Crank–Nicolson finite difference solutions. However, in the present model a semi‐analytical solution to the solid surface diffusion equation is presented, yielding a sophisticated solution of the differential equations. The solutions provide a good correlation between the experimental concentration–time decay curves by incorporating the Langmuir equilibrium isotherm to describe the solid phase surface dye concentrations. However, the surface diffusivities show a dependence on the carbon particle surface coverage and these diffusivities have been correlated using a Darken relationship. Copyright © 2004 Society of Chemical Industry     

Design and mechanism of controllable respiration polyamideamine-epichlorohydrin modied sugarcane bagasse pith hemicellulose film

The major challenge in hemicellulose blend films for food packaging is to overcome the inferior wet strength and hydrophilic properties of hemicellulose-based films. Inspired by the principle of wet strength of paper, novel bio-based packaging film with high barrier and strength properties was designed via bagasse pith hemicellulose as main substrate materials and polyamideamine-epichlorohydrin (PAE) as strengthening agent. The chemical characterization showed that the mechanical and barrier properties of the blend films were found to be strongly dependent upon the amount of PAE added in the films. Compared with the film without PAE, the tensile strength of PAE-containing film with optimal amount of 1% PAE increased by 100.25%, the water vapor permeability decreased by 23.25%, and the oxygen permeability decreased by 87.18%. The results showed that the new ester bond formed between PAE and hemicellulose caused the more excellent mechanical and barrier properties of films.     

Adsorption of phenols onto a polymeric sorbent

Adsorption of phenols from aqueous solutions onto a polymeric sorbent, SP206, was carried out in a finite batch adsorber. Multicomponent adsorption equilibrium data were experimentally measured and compared with those predicted by the ideal adsorbed solution theory (IAST) based on the Langmuir equation as single species isotherms. Intraparticle diffusion during adsorption was assumed to be expressed by the pore diffusion and the surface diffusion mechanisms and the effective diffusion coefficient of each species was determined by comparing experimental and predicted concentration histories. The surface diffusion model incorporated with the IAST successfully simulated the adsorption behaviour of a phenols-polymeric sorbent system up to three-species mixtures. The regeneration of spent sorbents was also investigated to get information for a cyclic adsorption process.     

Adsorption/desorption of phenols onto granular activated carbon in a liquid–solid fluidized bed

The adsorption/desorption of phenols in aqueous solution onto coconut‐shell granular activated carbon (GAC) in a liquid–solid fluidized bed adsorber approaching saturation capacity was investigated. Experiments were carried out using a 20 mm id adsorber under a variety of operating conditions including GAC particle sizes (0.937, 1.524 mm), GAC mass (12, 24 g), influent phenol concentration (0.367–1.071 mmol dm⁻³), surface loading of GAC (2.0, 2.5 mmol g⁻¹) and liquid flow rate (0.15, 0.2, 0.35 dm³ min⁻¹). The effect of repetitive adsorption/desorption cycles on the adsorption capacity has also been examined for phenol/GAC systems. The model based on the external mass transfer with film‐surface diffusion, surface adsorption equilibrium and internal mass transfer was proposed to simulate the breakthrough curves of the phenol adsorption/desorption process. Using the experimentally measured Langmuir isotherm equilibrium parameters in the model has been found to describe reasonably well the experimental results. © 1999 Society of Chemical Industry     

Graft copolymerization of acrylonitrile onto bagasse and wood pulps

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.     

Adsorption of basic dyes in a fixed bed column

The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied by using a fixed bed column. The design procedures for fixed bed adsorption columns have been investigated for two basic dyes, Maxilon Goldgelb GL EC 400% (MG-400) and Maxilon Shwarz FBL-01 300% (MS-300). The effects of process variables such as bed height, volumetric flow rate, and dye concentration have been investigated. The results have been used to predict the effect of parameter changes on the system by using the bed depth service time (BDST) approach. The performances of the column charged with the natural zeolite were compared with those of the column charged with activated carbon.     

Saccharification of bagasse using a counter-current plug-flow reactor

A method for the simulation of a 3-stage counter-current plug-flow reactor (PFR) for the enzymic Saccharification of alkali-treated (a.t.) sugar cane bagasse is described. The PFR gave higher conversion than a conventional stirred-tank reactor (STR). The STR achieved 44.3% conversion while the PFR achieved 56.4% conversion using 11 % a.t. bagasse after 48 h. The PFR offers potential for more efficient mass transfer and enzyme utilisation, and reduced end product inhibition.