Residual Alkali Research Articles

Catalytic ammonia decomposition over CMK-3 supported Ru catalysts: Effects of surface treatments of supports

CMK-3 carbon was used as a catalyst support for Ru catalyst for ammonia decomposition. The supports were treated with acid, and the effects of treatment on the properties of CMK-3 supports were studied by N 2 adsorption, XRD, XPS and mass titration. The chemical treatment of carbon support cause significant changes in carbon surface chemistry and in turn had significant effects on both catalyst dispersion and catalytic activity. It is found that the as-synthesized CMK-3 carbon is not a good catalyst support for this reaction. However, surface functional groups produced by acid treatments led to larger Ru catalyst particles, while alkali treatments made the Ru catalyst dispersion even worse due to the residue alkali or earth alkali metals. Interestingly, relatively larger Ru catalyst particles but still well dispersed in the channel of the mesoporous structures of the carbon improves NH 3 conversion into H 2. This is determined by the chemical reaction rate-limiting step of ammonia decomposition. The catalytic activity follows the order: Ru–K/CMK-3 > Ru–Na/CMK-3 > Ru–Ca/CMK-3 > Ru–Cl/CMK-3 > Ru–SO 4/CMK-3 > Ru–PO 4/CMK-3 > Ru/CMK-3 > Ru–Li/CMK-3. CMK-3 is not a good carbon catalyst support due to its amorphous structure resulting in the poor electron conductivity.

Kraft and soda-AQ pulping of dry fractionated reed canary grass

The effect of dry fractionation on pulping and pulp properties of reed canary grass was studied for two alkaline pulping processes. Multivariate data analysis was used to evaluate the influence of dry fractionation, alkali charge and cooking time on pulp yield, screening reject, drainage, fibre length distribution, kappa number and residual alkali in black liquor for kraft and soda-anthraquinone pulping of the grass. Of the factors included in the design, dry fractionation had the greatest influence on all the responses. Dry fractionation gave a pulp with higher yield, lower screening reject, lower kappa number, better drainage and reduced fines for both pulping processes.

Isolation and Characterization of Alkali-soluble Pectic Polysaccharides in Peach (Prunus persica Batsch) Fruit

The alkali-soluble polysaccharides in the cell wall extracted from immature and over-ripe peach fruit (Prunus persica Batsch) were analyzed. After removing water and the chelate compound (CDTA) soluble polysaccharides from the crude cell wall in the peach fruit tissue, the residual alkali soluble polysaccharides were extracted sequentially with 50 mM Na2CO3, 1 M KOH, and 4 M KOH. Using an ion exchange chromatography (DEAE-Sepharose 2.5 cm × 30 cm), the 1 M and 4 M KOH fractions were separated into three (1 M KOH a-c) and four fractions (4 M KOH a-d), respectively, but Na2CO3 soluble polysaccharides were not fractionated by this method. The acidic polysaccharide in 1 M KOH fraction (1 M KOH-b and c) was subjected to further analysis. The major sugars in fraction 1 M KOH-b and 1 M KOH-c were xylose and arabinose, respectively. The result of gel filtration (Sepharose CL-4B 1.5 × 40 cm) showed that the average molecular weight of the fraction 1 M KOH-b was heavier than that of the fraction 1 M KOH-c; moreso in immature fruit harvested on Aug. 7 than that in over-ripe fruit harvested on Aug. 24. The results of xylanase (EC 3.2.1.8) treatment of fraction 1 M KOH-b and sugar composition analysis using GLC showed that this fraction was composed of complex polysac-charides of xylan and rhamno-galacturonan. Based on the data of acid hydrolysis and sugar composition analysis the polysaccharides in fraction 1 M KOH-c consisted of xyloglucan and rhamno-galacturonan.

Enhancing the cell affinity of macroporous poly(L‐lactide) cell scaffold by a convenient surface modification method

AbstractIn this study, the macroporous poly(L‐lactide) (PLLA) cell scaffold was modified for enhancing its cell affinity by an improved surface‐treating medium, a mixture of aqueous 0.25 M NaOH/ethanol. Ethanol was applied as a co‐treating medium to wet the polylactone and assist the hydroxide nucleophilic attack on the ester bond. Low concentration of NaOH could be applied, severe bulk degradation could be avoided and the residual alkali was easy to remove. Treating time could also be shortened. After treatment under optimal conditions, the surface hydrophilicity and surface energy of PLLA were improved significantly and the surface roughness was also changed. Modification of the spherulite structure on PLLA surface was observed with the treating time using a computer‐assisted image analysis system (CAIAS). The results of gel permeation chromatography measurements indicated that only the outer layer of the PLLA was modified and the bulk properties were not altered. Mouse 3T3 fibroblasts culture results indicated that the improved surface‐treating medium was effective and convenient for enhancing the cell affinity of PLLA cell scaffold. Copyright © 2003 Society of Chemical Industry

Fourier‐transform infrared spectra of fatty acid salts—Kinetics of high‐oleic sunflower oil saponification

AbstractSodium, lithium, and calcium soaps obtained by saponification of high‐oleic sunflower oil were studied by Fourier‐transform infrared spectroscopy. Spectra of crude mixtures containing soap, glycerin, residual alkali, and triacylglycerols were compared to those of pure soaps obtained from fatty acids. The infrared spectra of crude soaps showed the same characteristic bands as pure ones. The absorption bands of asymmetric (ω2) and symmetric (ω1) stretching vibrations of the carboxylate group indicated that the metal‐oxygen bonds of these soaps had an ionic character whose strength differed from one cationic counterion to another. Once the characteristic absorption bands of the soaps were assigned, a kinetics study of saponification was performed. Saponification by sodium, anhydrous lithium, and calcium hydroxides was an autocatalytic reaction, characterized by an S‐shaped kinetics curve, whereas saponification by aqueous lithium hydroxide was stoichiometric. The structure of the metal‐oxygen bond played a role in the kinetic mechanisms.

Some factors affecting the brightness and TCF-bleachability of kraft pulp

By varying the cooking conditions, several series of kraft pulps having different brightness levels, i.e. different light absorption coefficients (k), were prepared. A clear correlation between the residual alkali concentration in the black liquor and the k-value was found. The darkening of the pulp (increasing k) was shown to be, in part, due to a higher content of calcium ions that increased lignin redeposition onto the fibers during the cook. Moreover, the production of a bright unbleached pulp (with low k-value) appeared to be beneficial for subsequent TCF-bleaching with hydrogen peroxide.

Xylanase pretreatment leads to enhanced soda pulping of wheat straw

Wheat straw was treated with a crude enzyme containing mainly xylanase prior to soda cooking. The enzyme was prepared from the culture filtration of Aspergillus niger strain An-76. The suitable conditions of pretreatment were xylanase dosage of 4 IU/g (on oven dry wheat straw), 48°C, 6–8 h, and pH 5.0, pretreated wheat straw was thorough washed after pretreatment. Xylanase pretreatment can improve pulpability of wheat straw effectively, and produce the pulps with lower kappa number (about 2 units lower), lower rejects and similar yields of screened-pulps under identical pulping conditions. The residual active alkali consistency of black liquor was increased by xylanase pretreatment. The brightness of bleached pulps from the xylanase pretreated wheat straw was about 3%ISO higher than that of the controls using identical bleaching sequence and conditions. The pulps, including unbleached pulps and bleached pulps, from the xylanase pretreated wheat straw had a higher tear index, a lower tensile index, and a lower burst index as compared to the control. The changes in the chemical components of wheat straw, crystallizability degree of cellulose, fiber average length and fines contents in the pulps were investigated in order to interpret differences of pulping results from the xylanase pretreated wheat straw and the controls.

Applying a Fuzzy Gain-Scheduled PID Controller to Dyebath pH

One of the factors critical to dyeing levelness in the textile industry is pH control, but it is a difficult problem because of inherent nonlinearity and changing process dynamics. The proportional integral derivative (PID) controller has been widely used in industry. Conventional fixed gains are hard to achieve with dyebath pH control, since it is difficult to model the process and the scheme is not adaptive to time-varying characteristics. Thus, a fuzzy gain-scheduled PID controller is promising for dyebath pH control because of its self-adaptation and robustness. The control scheme uses fuzzy rules and reasoning to autotune PID gains without the need of modeling. A modification to overcome the difficulty in finding the ranges of gains for stability is proposed. Simplified dyeing experiments demonstrate that the proposed controller can track pH set values under the influence of temperature rise, residual alkali, etc.

Influence of the Nature of Residual Alkali Cations on the Catalytic Activity of Zeolites X, Y, and EMT in their Brønsted Acid Forms

Lanthanum-exchanged zeolites X, Y, and EMT, containing either sodium or potassium as residual cations, were used as catalysts in two acid-catalyzed hydrocarbon reactions, viz. the disproportionation of ethylbenzene and the isomerization of n-octane (for the latter reaction, Pd/γ-Al2O3 was admixed to the acid zeolites to make the catalysts bifunctional). All pairs of LaM-type zeolites (where M stands for Na or K) showed remarkable activity differences, the LaK form being always less active than the LaNa form. IR and 1H NMR spectroscopy revealed that, for a given zeolite type and degree of lanthanum exchange, the concentration of bridging hydroxyl groups in the large cages was at least 20% lower than that for the LaK form. 139La NMR spectroscopy indicated that the concentration of lanthanum ions in the large cages of the as-exchanged LaK forms was always lower than that in the corresponding LaNa forms. Surprisingly, already in the as-exchanged LaK forms, some La3+ migration into the small cages appears to occur, and this was corroborated by framework strains indicated by 29Si and 27Al NMR. It is proposed that potassium cations in the large cages cause an enhanced migration of lanthanum cations into the small cages and a preferential formation of Brønsted acid sites in these small cages during the thermal dehydration of lanthanum cations (Hirschler–Plank mechanism). A similar effect was found in HNaY and HKY zeolites: The presence of the bulkier potassium cations causes a significant diminution of the accessible Brønsted acid sites in the large cages and of the catalytic activity. Overall, one must conclude from these results that in zeolites possessing both large and small cages, the nature of the residual alkali cations can exert a pronounced influence on the local distribution of the Brønsted acid sites, regardless of how these sites were generated. Copyri ght 2001 Academic Press.

Fate of atrazine and chlorpyrifos during solid state fermentation—examination of processes

Solid state fermentation (SSF) was investigated as a means to dispose of two commonly used pesticides, chlorpyrifos (O, O‐diethyl O‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate) and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine). SSF experiments were carried out in bench‐scale bioreaetors (equipped with CO2 and volatile organic traps) containing a mixture of lignocellulosic materials and a radiolabeled pesticide. Ethyl acetate‐extractable, alkali soluble, and alkali insoluble fractions were evaluated for radioactivity following a 60‐d incubation period at 40°C. The majority of the [2, 6‐pyridyl‐14C]chlorpyrifos was associated with the ethyl acetate extract (about 74%), 17% was trapped as organic volatiles by polyurethane foam traps and < 0.5% of the chlorpyrifos was mineralized to CO2. Only small amounts of the radioactivity were associated with alkali soluble (0.0003%) and alkali insoluble (0.3%) fractions. In the [14C‐U‐ring] atrazine bioreactors, very little of the radioactivity volatilized (<0.5%) and less than 0.5% was mineralized to CO2. Approximately 57% of the applied radioactivity was associated with the ethyl acetate extract while 9% and 24% of the radioactivity was associated with the alkali soluble (humic and fulvic acids) and alkali insoluble fractions, respectively. Possible reaction mechanisms by which covalent bonds could be formed between atrazine (or metabolites) and humic substances were investigated. The issue of bound atrazine residue (alkali soluble fraction) was at least partially resolved. Oxidative coupling experiments revealed that formation of covalent bond linkages between amino substituent groups of atrazine residue and humic substances is highly unlikely.

A mathematical model of kraft pulping related to the alkali concentration in the cooking liquor

A new mathematical model for checking and controlling the kraft pulping process has been derived. The model is based on the modified relationship between the lignin content and the alkali concentration of a cooking liquor expressed as the ratio of lignin/active alkali vs. concentration of the active alkali in a cooking liquor. The derived model characterizes the variation of the lignin content of the partially delignified wood or pulp with the concentration of the residual alkali in a cooking liquor during an entire pulping cycle, i.e. during the initial, transition, bulk and residual phases of the kraft delignification. The relationship between the lignin content of the partially delignified wood ships or pulp and the concentration of the residual alkali in a cooking liquor is expressed by the logarithmic straight line equation or its power form. The slope and intercept constants of the derived equation for the individual phase of delignification have different values.

Response of Broiler Chicks to Dietary Inclusion of Alkali-treated and Washed Cocoa-pod Husk

Sobamiwa, O. 1999. Response of broiler chicks to dietary inclusion of alkali-treated and washed cocoa-pod husk. J. Appl. Anim. Res., 15: 191–196. Performance characteristics and apparent retention of nutrients were studied in 150 broiler chicks fed 0, 5, 10, 15 and 20% alkali-treated, and, washed, cocoa-pod husk (TWCPH) in their diets from day-old, to 4 weeks. Dietary inclusion of TWCPH at 5, 10 and 15% stimulated, higher (P<0.05) feed intake. Weight gain, feed conversion and the digestibilities of dry matter and phosphorus were depressed, at TWCPH levels above 5%. The method, of alkali treatment used, in this study appeared effective in taking care of excess ash and residual alkali characteristic of alkali- treated materials but was ineffective in upgrading the nutritive value, of cocoa, husk for broiler chicks.

Effect of pH, Temperature, and Time on Inactivation of Tannins and Possible Implications in Detannification Studies

The tannins from quebracho and leaves of Acioa barteri after purification, and commercially available tannic acid, were stored in buffers of different pH values (6−11) at 0, 20, and 37 °C. The recovery of tannins was monitored at different time intervals (up to 18 h) using Folin−Ciocalteu and butanol−HCl−Fe3+ reagents. The recovery of tannins decreased with increase in time of storage, increase in pH, and increase in temperature. The decrease in the recovery of tannins was accompanied by a decrease in their protein precipitation capacity, and also there was no defined peak for the assay medium following the butanol−HCl−Fe3+ method for the purified quebracho and A. barteri tannins when stored at pH 11. These observations suggested that the decrease in recovery of tannins was due to inactivation of tannins. A. barteri tannins were found to be most susceptible to pH-mediated inactivation. The stirring of quebracho tannins increased the rate of inactivation at pH 11. The results suggested that alkaline pH inactivates the tannins. The rate of inactivation is higher at higher temperatures, and it can be further increased by oxygen present in the air or possibly by any other oxidizing agent. These observations were exploited to detannify tannins in some agroindustrial byproducts by using hydrogen peroxide (a strong oxidizing agent) in the presence of sodium hydroxide. This treatment was found to be very effective; the decrease in tannins reached as high as 99% in some cases. The results of the present study also highlighted a problem related to quantification of tannins in samples treated with alkalis. During extraction of tannins from such materials, tannins were inactivated due to alkalinity in the extraction medium, thereby giving an underestimate of the actual tannin levels. The alkalinity in the extraction medium results from the residual alkali present in the treated materials. This problem was overcome by addition of hydrochloric acid in the extraction medium so that the pH during extraction did not rise above 7. The results of the present study also suggest that for studying the nutritional, physiological, and biological effects of tannins (i) the pH of the tannin-containing solution should never at any stage be alkaline, (ii) the solution should be kept at low temperature, and (iii) the exposure to oxygen or to any other oxidizing agent should be avoided. Keywords: Inactivation of tannins; pH; temperature; detannification; quantification of tannins

Effect of isolation procedures on the molecular composition and physical properties of Eucheuma cottonii carrageenan

Direct treatment of Eucheuma cottonii with hot potassium hydroxide leads to a solid residue (alkali treated weed) which was found to contain predominantly carrageenan and cellulose. Following dispersion and heating in water, separation into polymer-containing solution and an insoluble particulate phase was readily achieved. Chemical analysis of solubilized polymers showed that the predominant carrageenan present in native weed was a mu/kappa-carrageenan which was readily converted into kappa with hot alkali. The particulate phase from both materials was predominantly cellulose; characterization by X-ray diffraction showed the presence of partial cellulose type I crystallinity. Solid state 13C-NMR spectra showed that this crystalline fraction was ~53% of the total cellulose and was comprised of ~40% type I α and ~60% type I β . The cellulosic part seemed unaffected by the hot alkali treatment. A carrageenan type polysaccharide was found associated with the cellulosic fraction; which underwent the same conversion as the mu/kappa carrageenan on alkali treatment. Further refining of solubilized carrageenan by isopropyl alcohol precipitation, gel pressing or freeze-drying, resulted in only minor differences in chemical composition. Hot solution viscosity and gelation properties in the presence of potassium chloride were measured showing no significant differences in gelling behaviour between alkali treated weed and the different carrageenan isolates but a higher solution viscosity for the alkali treated weed.

Humidity Effects on Porous Silica Thin Films

ABSTRACTImpedance Spectroscopy is being used to study the humidity sensitivity of porous silica thin films. The films are processed via a colloidal sol-gel method which leaves some remnant potassium and sodium. Previous work on bulk porous silica samples processed by the same method showed that the dielectric properties and ac conductivity were very sensitive to changes in humidity. The aim of this work was to determine if the same dependencies could be found in the thin films. The capacitance, dielectric loss, and ac conductivity of the films were measured in a controlled environment chamber from 20–80% RH for frequencies ranging from 10Hz–10MHz. In addition to characterizing films with varying amounts of residual alkali ions obtained through leaching, we have also measured films that were surface doped with controlled amounts of KCl, LiCl, or NaCl. Relative humidity dependencies in the films are not as dramatic as in the bulk samples. The reasons for this behavior are not yet clear, but may be associated with the porosity, thickness, and surface area of the films.

The nutritive value of alkali-treated cocoa husk meal in broiler chick diets

The effect of alkali concentration and treatment on the chemical composition of cocoapod husk (CPH) was investigated. This was followed by the incorporation of the alkalitreated CPH (TCPH) in broiler starter diets to investigate its nutritive value. Alkali was obtained from cocoa-pod ash, 7.35 g of which was found to be equivalent in alkali strength to 1 g sodium hydroxide. Longer alkali treatment time (48 h) yielded similar effects to those produced after 24 h. Increasing alkali concentration (5, 10, 15 and 20 g kg −1) decreased the amounts of crude fibre, hemicellulose, cellulose and crude protein, but increased total ash, Na, Cu, Fe, Mn and Zn contents of CPH. An alkali concentration of 10 g kg −1 (which appeared most balanced in its effect on the chemical contents of CPH) was employed in a 24 h-treatment of the husks used in the feeding trial. TCPH was included in the diets at concentrations of 0, 50, 100 and 150 g kg −1. Each diet was fed to triplicate groups of 15, day-old broiler chicks for 28 days. The results showed that increasing TCPH level up to 100 g kg −1 did not significantly reduce growth performance and apparent digestibility of nutrients. Dietary inclusion of TCPH at 150 g kg −1 significantly ( P < 0.05) reduced weight gain and feed efficiency compared with those on the control diet (weight gain, 497.0 g vs. 520.3 g; feed efficiency, 2.61 vs. 2.12, respectively). Also the apparent digestibilities of crude protein (0.80) and crude fat (0.90) for the control diet decreased significantly ( P < 0.05) to 0.75 and 0.84, respectively, for the 150 g kg −1 TCPH diet. Water consumption of chicks increased with increasing TCPH level. It was concluded that in order to effect the potential upgrading of the nutritive value of CPH, it is necessary to remove salt deposition and residual alkali, which may have masked the effect of alkali treatment.

On the determination of residual alkali in black liquors

On the determination of residual alkali in black liquors

Preparation and characterization of ceria under an oxidizing atmosphere. Thermal analysis, XPS, and EPR study

Cerium hydroxide samples prepared with different precipitating agents (NaOH, KOH, NH[sub 4]OH) have been studied by thermogravimetry, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The untreated samples are a mixture of CeO[sub 2] and Ce(OH)[sub 4] with a small quantity of Ce(OH)[sub 3] present in the bulk of the solid. A part of the Ce[sup 3+] species remains stable even after calcination at high temperatures (1073 K) under air. The residual alkali elements issuing from the precipitating agents induce variations on the final state of the solid. 38 refs., 7 figs., 1 tab.

The utilization of alkali-treated wheat straw: effects of neutralization of residual alkali and potassium supplementation on growth and mineral balance of male calves

ABSTRACTThe mineral balance of male calves given neutralized (with HC1) and unneutralized 35 g NaOH per kg treated wheat straw (WS), was determined in a digestibility trial in which WS was offered at inclusion levels of 300, 500 and 700 g/kg diet. The ratio of apparently retained sodium (Na) and potassium (K) increased with increasing proportion of straw in the diet and was lower on neutralized straw diets.The effect of supplementation with 3 and 6 g K per kg diet dry matter in a diet comprising approximately 500 g/kg of 35 g NaOH per kg treated WS, on performance, mineral status and acidbase balance was examined in a growth trial with 56 Israeli-Friesian male calves. The animals on the untreated WS diet had significantly (P&lt; 0·05) less fat in the large depots and lower fat trim of carcass than did animals on the treated WS diets. No other differences in performance were significant. Ammonia concentration in rumen liquor and urea in blood were lower in the animals given alkali-treated WS. The concentrations of Na, K and chlorine in blood serum of the experimental animals were not affected by the treatment. The data on Na, K and magnesium (Mg) in muscle show depletion of Na and K and a trend towards a decrease in Mg concentration. K supplementation reduced the extent of depletion of Na and K. In bone, only Na was affected by the feeding of alkali-treated WS, the pattern being the same as in the muscle. The blood acid-base balance of the experimental animals was not significantly affected by treatments. The values of pH, actual bicarbonate and pCO2 of the animals given 35 g/kg alkali-treated WS indicate mild alkalosis in those animals. This alkalotic state did not affect performance. It appears that there is no Na loading problem which might interfere with growth.

Hydrothermal stability of US-Ex

USY samples, which were prepared from sodium Y whose Si/Al atomic ratios were in the range of 2.5 to 3.0, were treated hydrothermally under deep-bed conditions and with steam. The nonframework and framework aluminum was extracted with HCl solutions. The hydrothermal stabilities under 100% steam of US-Ex were examined in relation with the unit cell dimensions, chemical analyses, MAS n.m.r., t.g., and i.r. observations. The hydrothermal stability of US-Ex was affected mainly by the amounts of framework and nonframework aluminum and the retention of crystallinity, but not by the amounts of residual alkali metal oxides and the amount of 4-OH nest. Some of Si (3Al) and Si (2Al) units converted to nonframework Si (4Al), Si (3Al), and Si (2Al) units and left the vacancies larger than four OH nests in zeolite framework. It was confirmed that the population of Si (4Al), Si (3Al), and Si (2Si) in parent sodium Y affects the retention of crystallinity of US-Ex.