Alkali Dosage Research Articles

Process Parameters Optimization of Casuarina equisetifolia for Enhanced Production of Bleachable Grade Kraft Pulp through RSM

Casuarina equisetifolia (beach sheoak), a fast-growing deciduous tropical hardwood tree, was utilized to assess its suitability for pulp and paper production. Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the kraft pulping process by varying the alkali doses, reaction temperature, and time. Using the best optimum pulping conditions with alkali charge 17.9%, temperature 170.2 °C, and pulping time 82.1 min, a high screened pulp yield of 52.4% with low kappa number of 18.1 and pulp viscosity of 974.5 cm3/g could be achieved. The laboratory handsheets prepared with kraft pulp under optimum conditions showed good mechanical strength properties at an optimum beating level of 45 °SR.

Effect of alkali dosage and silicate modulus on carbonation of alkali-activated slag mortars

The long-term durability and their mechanisms of alkali-activated cement based materials have remained largely elusive. In this paper, carbonation of alkali-activated slag (AAS) mortars activated by NaOH and waterglass with different alkali dosages and silicate moduli has been investigated after exposure to 3 ± 0.2% (v/v) CO2 at 20 ± 2 °C/65 ± 5% RH for 56 days. The results show that carbonation resistance of the AAS mortars increases with increase of not only alkali dosage but also silicate modulus. In addition to the higher pore solution alkalinity and slag reaction extent, the relatively higher carbonation resistance of the AAS mortars is attributed to the lower porosity and average pore size. The loss of compressive strength for the waterglass activated slag mortars after carbonation is due to decalcification of C-A-S-H phase, whereas the carbonation of katoite contributes to the increase of compressive strength of the NaOH activated slag mortars.

Effects of alkali dosage and silicate modulus on alkali-silica reaction in alkali-activated slag mortars

The effects of silicate modulus and alkali dosage on alkali-silica reaction (ASR) of alkali-activated slag (AAS) mortars are investigated under accelerated mortar bar testing conditions as specified in ASTM C1260. At a given alkali dosage, an intermediate silicate modulus with respect to highest ASR expansion is observed, which increases from 1.0 to >2.0 with increase of alkali dosage. The effect of silicate modulus on ASR expansion is found to be governed by the pore solution alkalinity. At a given higher silicate modulus such as 1.5 and 2.0 at 14 day, the ASR expansion tends to increase with increase of alkali dosage, whereas it decreases with increase of alkali dosage at a given lower silicate modulus such as 0–0.5 at 28 day. The mechanism governing the effect of alkali dosage on ASR expansion is more complicated and cannot be explained by only the pore solution alkalinity.

Fundamental understanding of distracted oxygen delignification efficiency by dissolved lignin during biorefinery process of eucalyptus

In this work, a fundamental understanding of oxygen delignification distracted by dissolved lignin was investigated. In the new biorefinery model of shortening kraft pulping integrated with extended oxygen delignification process, increasing content of residual lignin in the original pulp could result in enhanced delignification efficiency, higher pulp viscosity and less carbonyl groups. However, the invalid oxygen consumption by dissolved lignin could be increased with the increase of process temperature and alkali dosage. The normalized ultraviolet absorbance (divided by absorbance at 280 nm) also showed that the content of chromophoric group in dissolved lignin decreased with oxygen delignification proceeded, both of which indicated that dissolved lignin could enhance the invalid oxygen consumption. Therefore, a conclusion that replacement of the liquor at the initial phase of oxygen delignification process would balance the enhancement of delignification efficiency and invalid oxygen consumption was achieved.

Efficient removal of Acid Green 25 dye from wastewater using activated Prunus Dulcis as biosorbent: Batch and column studies

Biosorbent synthesized from dead leaves of Prunus Dulcis with chemical activation during the synthesis was applied for the removal of Acid Green 25 dye from wastewater. The obtained biosorbent was characterized using Brunauer-Emmett-Teller analysis, Fourier transform-infrared spectroscopy and scanning electron microscopy measurements. It was demonstrated that alkali treatment during the synthesis significantly increased surface area of biosorbent from 67.205 to 426.346 m2/g. The effect of various operating parameters on dye removal was investigated in batch operation and optimum values of parameters were established as pH of 2, 14 g/L as the dose of natural biosorbent and 6 g/L as the dose of alkali treated biosorbent. Relative error values were determined to check fitting of obtained data to the different kinetic and isotherm models. It was established that pseudo-second order kinetic model and Langmuir isotherm fitted suitably to the obtained batch experimental data. Maximum biosorption capacity values were estimated as 22.68 and 50.79 mg/g for natural biosorbent and for alkali activated Prunus Dulcis, respectively. Adsorption was observed as endothermic and activation energy of 6.22 kJ/mol confirmed physical type of adsorption. Column experiments were also conducted to probe the effectiveness of biosorbent for practical applications in continuous operation. Breakthrough parameters were established by studying the effect of biosorbent height, flow rate of dye solution and initial dye concentration on the extent of dye removal. The maximum biosorption capacity under optimized conditions in the column operation was estimated as 28.57 mg/g. Thomas and Yoon-Nelson models were found to be suitably fitted to obtained column data. Reusability study carried out in batch and continuous column operations confirmed that synthesized biosorbent can be used repeatedly for dye removal from wastewater.

Effect of Alkalis pretreatment on Lignocellulosic Waste Biomass for Biogas Production

Abstract- Converting lignocellulosic waste biomass into biogas is a multi-step process; the rate limiting reaction is lignin removal. The objective of the current study was to evaluate alkali treatment for lignin removal and potential of biogas yield of pretreated waste biomass compare to untreated one. Three alkali reagents at various dosages: NaOH (1,2,3, and 5%), KOH (1,2,3, and 5%), and Ca(OH) 2 (0.5%) were tested at three different heating processes, water bath, autoclave and short time microwave. NaOH with short time microwave heating process had the highest delignification of 70-86% compare to other alkalies and heating processes. However, an opposite effect of high alkali dosage was observed on holocellulose. The highest cumulative biogas of 560 mL/gVS was obtained from 2% NaOH pretreated wheat straw, which was 2-times higher than the cumulative biogas produced from the same untreated substrates. In the present study 2% NaOH alkali and microwave heating is determined optimum for lignin removal from waste biomass and enhancement in biogas production. Keywords Anaerobic digestion; alkaline pre-treatment; biogas; delignification; lignocellulosic waste.

The Effects of NaOH-Urea Aqueous Solution on the Strength and Softness Properties of Bamboo Ligno-cellulosic Fibers

APMP (alkaline peroxide mechanical pulp) of bamboo was treated in NaOH-urea aqueous solution to modify the fiber properties. The effects of soaking time, fiber concentration, alkali dosage, freezing temperature, and freezing time were evaluated by single-factor experiments. The optimal conditions were determined as a soaking time of 10 min, a fiber concentration of 15%, an alkali dosage of 6%, a freezing temperature of -7 °C, and a freezing time of 40 min. Compared with the properties of untreated APMP, the tensile index of the treated APMP was increased by 64%, and the burst index was increased by 82%. The bulk was reduced by 15%, and the softness was increased by 18%. There was no obvious variation on the folding strength. According to the instrumental analysis, there were no significant effects on the structure in terms of functional groups, the crystalline region, or the fiber surface morphology; however, the variation on the fiber quality was more significant.

Effect of Alkali Treatment Combined with High Pressure on Extraction Efficiency of β-d-Glucan from Spent Brewer’s Yeast

β-d-glucan, an important constituent of spent brewer’s yeast cell walls, shows numerous physiological functions, leading to the great potential to be used in food industry. Conventional isolation method of β-d-glucan (alkali treatment at ordinary pressure, ATOP) requires high alkali dosage and excessively long extraction time. In this paper, we found that combination of high pressure treatment and alkali treatment could reduce alkali dosage and significantly shorten processing time. Transmission electron micrographs of yeast cells showed that combination of high pressure treatment and alkali treatment made yeast cell walls swell significantly and become loose, which increased the contact area with alkali solution and contributed to the efficient removal of other impurities. Accordingly, an innovative isolation method (i.e., alkali treatment at high pressure, ATHP) of β-d-glucan from spent brewer’s yeast was developed in this study. The optimal conditions of 0.85% alkali concentration, 6.5:1 liquid–solid ratio, 108 °C temperature (pressure, 0.039 MPa), and 5 min time were obtained by using single-factor experiments and response surface methodology. Under these conditions, β-d-glucan content and extraction rate were 78.11 and 78.38%, respectively. NMR spectra confirmed that glucan prepared by ATHP is a polymer of β-(1,3) linked glucose with β-(1,6) branches.

Metabolic Acidosis and Subclinical Metabolic Acidosis in CKD.

Metabolic acidosis is not uncommon in CKD and is linked with bone demineralization, muscle catabolism, and higher risks of CKD progression and mortality. Clinical practice guidelines recommend maintaining serum total CO2 at ≥22 mEq/L to help prevent these complications. Although a definitive trial testing whether correcting metabolic acidosis improves clinical outcomes has not been conducted, results from small, single-center studies support this notion. Furthermore, biologic plausibility supports the notion that a subset of patients with CKD have acid-mediated organ injury despite having a normal serum total CO2 and might benefit from oral alkali before overt acidosis develops. Identifying these individuals with subclinical metabolic acidosis is challenging, but recent results suggest that urinary acid excretion measurements may be helpful. The dose of alkali to provide in this setting is unknown as well. The review discusses these topics and the prevalence and risk factors of metabolic acidosis, mechanisms of acid-mediated organ injury, results from interventional studies, and potential harms of alkali therapy in CKD.

Oxalate formation during hydrogen peroxide-reinforced oxygen delignification

The effects of different process parameters (alkali dosage, hydrogen peroxide dosage, temperature, reaction time, and oxygen pressure) on oxalate formation during hydrogen peroxide-reinforced oxygen delignification (OP) of Eucalyptus kraft pulp were investigated in the present study. The relationships between oxalate formation and the dosages of both alkali and peroxide were found to be almost linear. Oxalate formation could be divided into “fast” and “slow” periods, depending on the reaction time. The best selectivity for the OP process was achieved using an alkali dosage of 2.0%, a hydrogen peroxide dosage of 2.0%, a temperature of 100°C, an oxygen pressure of 0.6MPa and a reaction time of 60min. Oxalate formation was also, to some extent, reduced under these conditions. These results will be very helpful in optimizing the OP process, controlling oxalate formation and improving product quality.

Impact of mild alkali dosage on immobilized Exiguobacterium spp. mediated cost and energy efficient sludge disintegration

Approaches to (extracellular polymeric substance) EPS removal were studied with major aim to enhance the biodegradability and sludge solubilization. In this study, a novel approach of entrapment of bacterial strain was carried out to achieve long term activity of protease secreting bacteria Exiguobacterium sp. A mild treatment of potassium hydroxide (KOH) was applied to remove EPS which was followed by entrapment under the biological pretreatment. The efficiency of Exiguobacterium was predicted through dissolvable organic and suspended solids (SS) reduction. The maximum dissolvable organic matter released was 2300mg/L with the solubilization of 23% which was obtained for sludge without EPS (SWOE). For dissolvable organic release, SWOE showed higher final methane production of 232mL/g COD at the production rate of 16.2mL/g COD.d. The SWOE pretreatment was found to be cost effective and less energy intensive beneficial in terms of energy and cost (43.9KWh and −8.2USD) when compared to sludge with EPS (SWE) pretreatment (−177.6KWh and −91.23USD).

Synthesis of sodium carboxymethyl cellulose using bleached crude cellulose fractionated from cornstalk

In this study, crude cellulose derived from cornstalk, after bleaching, was used as raw material for the synthesis of sodium carboxymethyl cellulose (CMC) by reacting with the cellulose with NaOH and chloroacetic acid at 75 °C for 1.5 h. Effects of alkali dosage, concentration of chloroacetic acid on the physical and chemical properties of the CMC products were investigated. It was revealed that the reactants alkali reagent/chloroacetic acid/cellulose at the molar ratio of 4.6:2.8:1and 4:2.5:1, or at the molar ratio of NaOH/ClCH2COOH ≈1.6–1.64, resulted in CMC products of relatively high water solubility. The viscosity-average molecular weight Mv of these two CMC products obtained at molar ratios of 4.0:2.5:1 and 4.6:2.8:1 is in the range of 1.94 × 104–2.48 × 104 g mol−1, and the average DS of the two products are 0.57 and 0.85, respectively. As the solute concentration is above 2 wt%, the viscosity of the CMC-water solution exhibits nonlinear (exponential) increasing with increasing the solute concentration (typical of non-Newton fluids).

Study on the properties of artificial flood-prevention stone made by Yellow River silt

In the Yellow River Basin, the source of flood-prevention tone is scarce. The purpose of this study is to investigate the feasibility of producing a kind of artificial flood-prevention stone by using Yellow River silt via alkali-activated method. The effects of alkali dosage, slag content and curing age on the compressive strength of artificial flood-prevention stone were studied. The results showed that the specimen made from optimal mix proportion can meet the requirement of flood-prevention stone. The main product in alkali-activated process is C-S-H gel confirmed by microcosmic tests such as SEM/EDS, TG/DTG and so on. CaCO3 is generated by the carbonation of partial C-S-H gel and residual Ca(OH)2. C-S-H gel and CaCO3 have common contribution to strength. In addition, frost resistance of the artificial flood-prevention stone at the age of 90days was evaluated by freeze-thaw cycle method. The porosity and pore size distribution were tested by Mercury intrusion porosimetry (MIP) to explicate the change before and after freeze-thaw cycle. As a whole, it is feasible to produce artificial flood-prevention stone by using the Yellow River silt.

Effect of alkali dosage on alkali-silica reaction in sodium hydroxide activated slag mortars

Alkali-silica reaction (ASR) is one of the durability factors limiting the commercial use of alkali-activated slag (AAS) concrete. The effect of alkali dosage is of great importance and barely studied for ASR in AAS system. This study investigates the effect of alkali dosage on ASR in sodium hydroxide (NaOH) activated slag mortars. In addition to ASR expansion, the changes in sample weight, compressive strength, pore structure, and pore solution chemistry are also investigated for better understanding the factors controlling the ASR in AAS mortars. The present study shows that the pore solution alkalinity increases with increasing the alkali dosage of the activator. However, the ASR expansion decreases with increasing the alkali dosage. The SEM/EDX results show no significant difference in both morphology and chemical composition of the ASR products. The lower ASR expansion at higher alkali dosage may be attributed to the relatively higher concentration of aluminum in the pore solution due to higher degree of slag hydration, which is expected to mitigate the dissolution of silica from the reactive aggregate.

Structural Characterization of Lignin Isolated from Wheat-Straw during the Alkali Cooking Process

To investigate the behavior of lignin during the alkali cooking process with different alkali doses, this work demonstrated the structural characteristics illustrated by spectroscopic analyses. Gel permutation chromatography (GPC) and nuclear magnetic resonance (NMR) indicated that the lignin was composed of typical structures for a grass, generally with S and G units and small amounts of H units. The main substructures present were β-O-4 aryl ether linkages, and there were lower amounts of β-β and β-5 linkages. Alkali treatment conditions had evident effects on the chemical structures and properties of lignin. Moreover, NMR indicated that alkali cooking caused lignin to depolymerize more easily with increasing severity and to condense.

Optimization of sodium sulfide treatment of rice straw to increase the enzymatic hydrolysis in bioethanol production

The efficiency of sodium sulfide-assisted alkaline pulping for cellulose preparation from Oryza sativa L. rice straw in Vietnam for enzymatic saccharification was investigated. The response surface methodology was used for the determination of optimal technological parameters of alkaline pulping such as active alkali dosage, temperature and time. The optimal technological parameters were established to be active alkali dosage of 7%, treatment temperature of 100 °C and treatment time of 120 min. At these regimes, a maximal sugar yield of 51.8% (over dry rice straw) was obtained. It meant that the saccharification efficiency up to 97.1% could be achieved by using sodium sulfide-assisted alkaline pretreatment method. Addition of sodium sulfide into alkaline pretreatment resulted in higher sugar yield, higher level of depolymerization of lignin and less loss of cellulose. Moreover, liquid hydrolyzate after enzymatic hydrolysis was analyzed by HPLC to determine the compositions of sugar mixture. The fiber morphology in pretreated biomass solid was also revealed by SEM.

Absorbable Organic Halide Reduction Research in Elemental Chlorine-Free Bleaching of Eucalyptus Kraft Pulp

The parameters of elemental chlorine-free (ECF) bleaching (D0EpD1) of eucalyptus kraft pulp were optimized to reduce AOX formation. The optimal conditions were pulp concentration 10%, ClO2 dosage 2.8%, pH 3.5, temperature 60°C, time 60 min at D0; H2O2 dosage 1.25%, alkali dosage 2.0%, temperature 65°C, time 105 min at Ep; ClO2 dosage 0.2%, pH 4.5, temperature 60°C, time 55 min at D1. AOX formation was 0.553 kg.tp–1, each stage was 0.470 kg.tp–1, 0.060 kg.tp–1 and 0.023 kg.tp–1, respectively. Compared with un-optimized AOX formation decreased by 23.7%.The brightness and viscosity was 84.36% ISO, 834.6 mL.g–1. In fact, good quality of the pulp was obtained when AOX formation has fallen dramatically. These provide a theoretical basis for reducing the produce of AOX and realizing the clean bleaching.

Fabrication of polymeric–Laponite composite hollow microspheres via LBL assembly

Hollow structure microspheres with composite polymeric–Laponite shells were prepared by electrostatic self-assembly of Laponite on the polymeric hollow microspheres in this work. The multilayer hydrophilic core/hydrophobic shell polymer latex particles containing carboxyl groups inside were first synthesized via seeded emulsion polymerization, followed by alkali treatment, generating polymeric hollow microspheres. Then, polyethyleneimine (PEI) and Laponite were alternately electrostatic adsorbed on the prepared polymeric hollow microspheres to form polymeric–Laponite composite hollow microspheres. It was indicated that the morphology of alkali-treated microspheres could be tuned through simply altering the dosage of alkali used in the post-treatment process. Along with the increasing of the coating layers, the zeta potential of microspheres absorbed PEI or Laponite approximately tended to be constant respectively, and the thickness of Laponite layer around the hollow microspheres increased clearly, getting more uniform and homogenous. Furthermore, the corresponding polymeric–Laponite hollow microspheres showed high pressure resistance ability compared to the polymeric hollow microspheres.

Post-treatment and evaluation of polyester filament cotton-like fabric

Alkali reduction treatment was found to reach the imitation of cotton fabric and improve the wear ability of polyester fabric in this paper. Four main factors on the wearable ability were analyzed and through a set of orthogonal tests the optimal treatment parameters were received that alkali dosage of 25 g/l, handing time of 50 min, bath ratio of 1:15 and treatment temperature of 110 °C. Under the optimal conditions, samples were processed and then compared with raw ones via SEM to conclude differential appearances of fibers. Furthermore, preferential performances of the processed fabrics were analyzed by a group of tests in terms of tensile, shear and compressive properties. The experimental results proved that with the treatment of alkali, polyester fabrics could show soft handle, mild glossiness and superior texture which were in high uniformity with cotton fabrics.

NaOH-Thiourea Aqueous Solution Treatment of Cellulose Fiber and its Effects on Bulk and Softness

Bleached kraft pulp of hardwood was pretreated in a NaOH-thiourea aqueous solution to modify the bulk and softness of the cellulose fibers with minimal reduction in paper strength. The effects of soaking time, fiber concentration, alkali dosage, and freezing time were evaluated through single factor experiments. The optimal conditions were determined to be a soaking time of 15 min, fiber concentration of 15%, alkali dosage of 9%, and freezing time of 75 min. Under the optimal conditions, the bulk and softness of the treated cellulose fibers were increased by 28.7% and 21.6%, respectively, compared with those of untreated cellulose fibers. The tensile and burst indices were only reduced by 1.2% and 5.1%, respectively, under these conditions. Also, there were almost no effects on the polymerization degree, the thermostability, and the structure of the functional groups or crystalline regions.