Sodium Hydroxide Pretreatment Research Articles

Enhancement of paddy straw digestibility and biogas production by sodium hydroxide-microwave pretreatment

Biogas has become a promising energy substitute to fossil fuels. Lignocellulosics, being cheap and renewable resource, could be very well used as a feedstock for biogas generation. Paddy straw is an abundant lignocellulose which is rich in organic matter like cellulose, hemi-cellulose and lignin. It is generally disposed off by burning causing environmental pollution whilst it can be used for biofuel generation. The digestibility of paddy straw is low due to high lignin and silica content. The present study was carried out to enhance paddy straw digestibility and biogas production through sodium hydroxide (NaOH) pretreatment. The paddy straw was pretreated with NaOH by soaking (24 h) in different concentrations of NaOH (2, 4, 6, 8 and 10%) and supplementing with microwave irradiations (30 min, 720 W, 180 °C). 4% NaOH-30 min microwave was found to be the best pretreatment which resulted in 65.0% decrease in lignin content and 88.7% reduction in silica content. This increased digestibility due to reduced lignin and silica content resulted in 54.7% increase in biogas production. Scanning Electron Microscopy of pretreated paddy straw revealed breakdown of lignocellulose structure resulted from the tearing of different layers of cell wall of paddy straw.

Optimization of pre-treatment of de-oiled oil seed cake for release of reducing sugars by response surface methodology

AbstractPre-treatment is a process that releases simple sugars from complex lignocellulosic biomass by using chemicals like acid and alkali which are one of the simplest and cost effective techniques. In this study, the conditions for sulphuric acid and sodium hydroxide pretreatment of de-oiled oil seed cake (DOSC) were optimized by response surface methodology (RSM). The levels of factors (DOSC concentration, agitation speed, sulphuric acid (H2SO4), sodium hydroxide (NaOH) concentration and reaction time) that affect release of reducing sugars by pre-treatment were obtained by one factor at a time (OFAT) approach of which only H2SO4 concentration, NaOH concentration and reaction time showed significance. The levels of factors were optimized by central composite design. Optimized conditions were found to be 11.65% (v/v) of H2SO4 concentration at 1.28h and, 4 N of NaOH at 3.7 h for acid and alkali hydrolysis respectively. Under optimized conditions, the release of reducing sugars was found to be 0.69 g/L (41.36 mg RRS/ g cellulose) and 0.40 g/L (23.98 mg RRS/ g cellulose) for acid hydrolysis and alkali hydrolysis of DOSC, respectively. Hence, RSM was found to be an efficient technique to optimize the hydrolysis process and ensure maximum release of reducing sugars.

A physicochemical method for increasing methane production from rice straw: Extrusion combined with alkali pretreatment

Pretreatment is a crucial processing step in the conversion of lignocellulosic biomass (LB) into methane by anaerobic digestion. A physicochemical LB pretreatment method, i.e., using an extruder to reduce the biomass size prior to sodium hydroxide (NaOH) pretreatment, was reported. The optimal condition for economic feasibility and pretreatment efficiency was an alkaline loading rate of 3.0% at 35°C for 48h. Under this condition, the methane production from the rice straw that was processed by extrusion combined with NaOH pretreatment was 54.0% higher than that of a control sample. The energy recovery (ER) efficiency improved from 38.9% to 59.9% using the combination pretreatment. The mechanisms that caused the significant improvement in the methane production and ER efficiency in the extrusion–NaOH pretreatment were investigated. The pretreatment changed the physical properties (water-holding capacity, specific porosity, specific surface area and crystallinity index), the chemical composition (lignin, benzene–ethanol extractives and hot-water extractives) and the chemical structure, which increased degradation of holocelluloses and other difficulty biodegradable compounds.

Chemical Pretreatment and Enzymatic Saccharification of Seaweed Solid Wastes

The technical feasibility of seaweed waste utilization as a resource of renewable energy was investigated in this paper. The production of fermentable sugars from seaweed waste was studied by dilute sulfuric acid and sodium hydroxide pretreatment and further enzymatic hydrolysis. Pretreatment was conducted by using 1.0 and 2.0% dilute sulfuric acid w/v and 4 and 5% sodium hydroxide w/v for 30 min at 121 oC. Pretreated seaweed wastes were analyzed by X­Ray Diffraction (XRD) to examine the crystallinity index of the cellulose and observed using Scanning Electron Microscopy (SEM) to examine the changes in structure of cellulose fiber. Saccharification of pretreated seaweed waste was carried out using crude cellulase enzyme provided by Pulp and Paper Research Center in Bandung. Saccharification was done in shake flask with 20% of substrate in citrate phosphate buffer at 30 oC and 50 oC, agitation of 150 rpm in shaking incubator for 48 h. Samples were collected at 2, 6, 12, 24 and 48 h for further analysis. Enzyme concentrations were varied between 10­50 U/g dry samples. The results showed that dilute acid and base pretreatment of seaweed solid waste can be used to improve the digestibility of seaweed waste. It successfully acted by reducing the lignin content and degrading the structure of cellulose from crystalline into amorphous form which is more susceptible to the enzyme action.The optimum pretreatment condition was shown by 4% NaOH at 121 oC for 30 min, producing the most fermentable sugar concentration. Sugar concentration produced by saccharification was optimum at 50 oC, enzyme concentration of 50 U/g sample for 24 h base pretreatment. The results of the experiment were expected to contribute in the process development of bioconversion of lignocellulosic materials into renewable energy sources.

Optimization of hydrolysis and volatile fatty acids production from sugarcane filter cake: Effects of urea supplementation and sodium hydroxide pretreatment

Different methods for optimization the anaerobic digestion (AD) of sugarcane filter cake (FC) with a special focus on volatile fatty acids (VFA) production were studied. Sodium hydroxide (NaOH) pretreatment at different concentrations was investigated in batch experiments and the cumulative methane yields fitted to a dual-pool two-step model to provide an initial assessment on AD. The effects of nitrogen supplementation in form of urea and NaOH pretreatment for improved VFA production were evaluated in a semi-continuously operated reactor as well. The results indicated that higher NaOH concentrations during pretreatment accelerated the AD process and increased methane production in batch experiments. Nitrogen supplementation resulted in a VFA loss due to methane formation by buffering the pH value at nearly neutral conditions (∼6.7). However, the alkaline pretreatment with 6g NaOH/100g FCFM improved both the COD solubilization and the VFA yield by 37%, mainly consisted by n-butyric and acetic acids.

Rapid Biomimetic Coating of Biocompatible Calcium Phosphate on Titanium: Influence of Pretreated NaOH Concentration and Cleaning Method

In this study, the influence of employing three different sodium hydroxide (NaOH) pretreatment concentration (1, 3 and 5M) and two cleaning methods (Ultrasonic or Rinse) used in rapid biomimetic coating process on phase composition, function groups, thickness, amount and microstructure of the resulted coating was carried out. Regardless of process parameters, x-ray diffraction and Fourier transform infrared spectroscopy revealed that the all coating mainly comprised octacalcium phosphate and hydroxyapatite as main phases while the microstructure similarly consisted of sharp and interconnected plate-like calcium phosphate (CaP) crystals vertically grown on the surface of titanium. However, the change in sodium hydroxide concentration in pretreatment step and cleaning method influenced the weight change after pretreatment, coating continuity and uniformity, but not the weight change after coating. This could be related to amount of the amorphous alkali gel layer formed during pretreatment step which influenced the rate of coating formation in rapid biomimetic coating process.

Associating cooking additives with sodium hydroxide to pretreat bamboo residues for improving the enzymatic saccharification and monosaccharides production

Cooking additive pulping technique is used in kraft mill to increase delignification degree and pulp yield. In this work, cooking additives were firstly applied in the sodium hydroxide pretreatment for improving the bioconversion of bamboo residues to monosaccharides. Meanwhile, steam explosion and sulfuric acid pretreatments were also carried out on the sample to compare their impacts on monosaccharides production. Results indicated that associating anthraquinone with sodium hydroxide pretreatment showed the best performance in improving the original carbohydrates recovery, delignification, enzymatic saccharification, and monosaccharides production. After consecutive pretreatment and enzymatic saccharification process, 347.49g, 307.48g, 142.93g, and 87.15g of monosaccharides were released from 1000g dry bamboo residues pretreated by sodium hydroxide associating with anthraquinone, sodium hydroxide, steam explosion and sulfuric acid, respectively. The results suggested that associating cooking additive with sodium hydroxide is an effective pretreatment for bamboo residues to enhance enzymatic saccharification for monosaccharides production.

Alkali Pretreatment and Acid Hydrolysis of Coconut Pulp and Empty Fruit Bunch to Produce Glucose

Lignocellulose waste has great potential to be converted into value added products sustainably as it is readily available at low cost. The aim of this study is to examine the amount of glucose produced from coconut pulp and coconut empty fruit bunch using acid hydrolysis. Sodium hydroxide pretreatment is carried out at 70oC using different concentrations of sodium hydroxide which are 5%, 10%, 15% and 20% v/v for a duration time of 2 hours. Optimum pretreatment is evaluated using Fourier Transform Infra-Red (FTIR) analysis. It is observed that optimum pretreatment is at 20% v/v sodium hydroxide. The optimum samples are then hydrolysed using concentrations of 5%, 10%, 15% and 20% v/v of sulphuric acid at different temperatures of 30, 50, 70 and 90oC for 2 hours. Glucose concentration is analysed using an ultraviolet (UV) Spectrophotometer. The highest glucose concentrations obtained are 0.895 g/L and 0.550g/L for coconut pulp and coconut empty fruit bunch, respectively at 20% v/v acid concentration and a temperature of 90oC.

Enhancement of volatile fatty acids production from rice straw via anaerobic digestion with chemical pretreatment.

Rice straw is one of the most abundant renewable biomass sources and was selected as the feedstock for the production of volatile fatty acids (VFAs) from which microbial biodiesel can be produced. Two kinds of chemical pretreatments involving nitric acid and sodium hydroxide were investigated at 150 °C with 20 min of reaction time. The nitric acid pretreatment generated the most hemicellulose hydrolyzate, while significant reduction of the lignin occurred with sodium hydroxide pretreatment. Anaerobic digestion of 20 g/L rice straw yielded 6.00 and 7.09 g VFAs/L with 0.5% HNO3 and 2% NaOH, respectively. The VFAs yield with 2% NaOH was 0.35 g/g.

Pretreatment of a refractory arsenopyritic gold ore using hydroxyl ion

A sodium hydroxide pretreatment at ambient temperature was evaluated to increase gold extraction from a high-grade arsenopyrite mineral. A 2k factorial experimental design was established, with the following variables: NaOH concentration (0.1–3M), solid concentration (40–200g/L) and treatment time (6–48h). After applying the pretreatment, standard leaching tests with thiosulfate solution were performed to quantify the effects of these three variables on the gold extraction. While only 23 and 29% gold extraction was achieved in the as received mineral with cyanide and thiosulfate leaching, respectively, up to 81% was obtained with the pretreatments. The lower solid concentration and the higher NaOH concentration gave the best results. This demonstrates that the use of the hydroxyl ion represents an effective treatment for minerals with gold encapsulated in arsenopyrite. Gold extraction was related to that of arsenic removal. Silver leaching was also improved for most pretreatments, but to a lesser extent.

Enhancing Biogas Production from Pumpkin (Telfairia occidentalis) Stalk Waste through Its Blending with Cow Dung and Alkaline Sodium Hydroxide Pretreatment

Improvement of biogas production from Pumpkin (Telfairia occidentalis) stalk waste through its blending with cow dung and alkaline sodium hydroxide pretreatment was investigated. Untreated pumpkin stalk waste (Un-PST) acted as the control. Initial verification carried out using this waste led to the present investigation. The batch digestion process anaerobically took place for 30 days under ambient atmospheric conditions. Bio-digesters of 41.00 dm working volume were utilized. Cumulative volume of biogas yield from the cow dung blended with pumpkin stalk (PST-cd) was 3.57 dm/TS.kg and alkaline treated waste (PST-t) gave 4.48 dm/TS.kg, while untreated pumpkin stalk waste (Un-PST), yielded 1.50 dm 3 /TS.kg. Each of these systems also produced flammable gas at different times: the Un-PST -15 th day, PST-cd -5 th day and PST-t-8 th day, respectively. Paired sample T-Test carried out on volume of gas data indicated that t (t statistic) was 5.15 for paired sample Un-PST & PST-cd while 6.51 for Un-PST & PST-t with degree of freedom as 29; at 95% conf. interval. Hence, there was a significant (p0.05) difference in volume of gas production Original Research Article Eunice et al.; JSRR, 5(3): 194-202, 2015; Article no.JSRR.2015.087 195 between the untreated and treated waste systems. Overall, results indicate that the yield of biogas from the waste through the different treatments were significantly (p<0.05) enhanced for renewable energy production, sustainable environment and wealth recovery for urban and rural dwellers of developing countries such as Nigeria, when properly harnessed.

Improving Biomethane Production and Mass Bioconversion of Corn Stover Anaerobic Digestion by Adding NaOH Pretreatment and Trace Elements.

This research applied sodium hydroxide (NaOH) pretreatment and trace elements to improve biomethane production when using corn stover for anaerobic digestion. Full-factor experimental tests identified the best combination of trace elements with the NaOH pretreatment, indicating that the best combination was with 1.0, 0.4, and 0.4 mg·L−1·d−1 of elements Fe, Co, and Ni, respectively. The cumulative biomethane production adding NaOH pretreatment and trace elements was 11,367 mL; total solid bioconversion rate was 55.7%, which was 41.8%–62.2% higher than with NaOH-pretreatment alone and 22.2%–56.3% higher than with untreated corn stover. The best combination was obtained 5–9 days shorter than T90 and maintained good system operation stability. Only a fraction of the trace elements in the best combination was present in the resulting solution; more than 85% of the total amounts added were transferred into the solid fraction. Adding 0.897 g of Fe, 0.389 g of Co, and 0.349 g of Ni satisfied anaerobic digestion needs and enhanced biological activity at the beginning of the operation. The results showed that NaOH pretreatment and adding trace elements improve corn stover biodegradability and enhance biomethane production.

Thermo‐mechanical extrusion and sodium hydroxide pretreatments for ethanol production from destarched corn fiber

The effect of thermo‐mechanical extrusion and sodium hydroxide pretreatments on ethanol production from destarched corn fiber (DCF) was investigated. DCF was extruded at screw speed of 300 rpm, feed moisture content of 30%, and melt temperature of 140°C and then pretreated by 0.75, 1.50, 2.25, and 3.00% of sodium hydroxide solution in the autoclave at 121°C for 1 h. After sodium hydroxide pretreatment, the liquid and solid fractions were separated by centrifugation. The dry solid fraction was used for the determination of composition, characterization (crystallinity index, microstructure, degree of polymerization), enzymatic saccharification and fermentation process. Extruded DCF pretreated by 0.75% sodium hydroxide significantly decreased lignin content, crystallinity index and degree of polymerization for efficient enzymatic saccharification and gave significant increase in ethanol yield (35.13 g L−1). Therefore, thermo‐mechanical extrusion followed by 0.75% of sodium hydroxide pretreatment was a good pretreatment for ethanol production from DCF. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 823–831, 2015

Influence of process parameters on the content of biomimetic calcium phosphate coating on titanium: a Taguchi analysis.

In this study, a statistical design of experimental methodology based on Taguchi orthogonal design has been used to study the effect of various processing parameters on the amount of calcium phosphate coating produced by such technique. Seven control factors with three levels each including sodium hydroxide concentration, pretreatment temperature, pretreatment time, cleaning method, coating time, coating temperature and surface area to solution volume ratio were studied. X-ray diffraction revealed that all the coatings consisted of the mixture of octacalcium phosphate (OCP) and hydroxyapatite (HA) and the presence of each phase depended on the process conditions used. Various content and size (-1-100 μm) of isolated spheroid particles with nanosized plate-like morphology deposited on the titanium surface or a continuous layer of plate-like nanocrystals having the plate thickness in the range of -100-300 nm and the plate width in the range of 3-8 μm were formed depending on the process conditions employed. The optimum condition of using sodium hydroxide concentration of 1 M, pretreatment temperature of 70 degrees C, pretreatment time of 24 h, cleaning by ultrasonic, coating time of 6 h, coating temperature of 50 degrees C and surface area to solution volume ratio of 32.74 for producing the greatest amount of the coating formed on the titanium surface was predicted and validated. In addition, coating temperature was found to be the dominant factor with the greatest contribution to the coating formation while coating time and cleaning method were significant factors. Other factors had negligible effects on the coating performance.

Effects of Sodium Hydroxide Pretreatment on Structural Components of Biomass

Abstract. Pretreatment is a unit operation in the conversion of biomass to valuable products that utilizes various combinations of conditions, including chemicals, heat, pressure, and time, to reduce the recalcitrance of lignocellulose. Many such pretreatments have been developed over the years, as the operating conditions can be adapted so that lignocellulose is modified in ways unique to each pretreatment. By tailoring pretreatment conditions to achieve these modifications, the types of final products produced can be controlled. The purpose of this review is to provide a consolidated source of information for sodium hydroxide effects on lignocellulose. The structural characteristics of lignocellulose and the alterations that occur due to the application of sodium hydroxide are detailed. This review also includes a brief description of the chemical reaction mechanism that ensues during the pretreatment. Lastly, the results of studies that utilized sodium hydroxide pretreatment are discussed.

Fast Determination of the Composition of Pretreated Sugarcane Bagasse Using Near-Infrared Spectroscopy

The chemical composition of pretreated sugarcane bagasse (SCB), in terms of cellulose, hemicellulose and lignin, was analyzed using a fast near-infrared spectroscopy (NIR) technique. Spectra of four types of SCB, prepared using ammonia, hydrothermal, organosolv, and sodium hydroxide pretreatments, were correlated with results of classical chemical analyses using partial least squares (PLS) regression. In a novel approach, isolation of the components used to prepare synthetic samples of SCB permitted assessment of their influence on the model. Inclusion of the synthetic samples did not improve the performance of the model, due to structural differences such as chemical bonding and physical interactions between the components. For natural pretreated samples, the PLS technique showed good predictive capacity in the ranges (%, w/w) of 47.2–89.4 (cellulose), 0.2–27.0 (hemicellulose), and 2.1–30.0 (lignin) with low root-mean-square error values of 4.1, 3.8, and 3.5, respectively, and coefficient of determination higher than 0.80, demonstrating the suitability of using different pretreated samples in the same calibration model.

Impact of Alkali Pretreatment on the Chemical Component Distribution and Ultrastructure of Poplar Cell Walls

Alkali pretreatment is one of the leading pretreatment technologies for biofuel applications. The histochemical and structural characteristics of poplar cell walls were investigated before and after sodium hydroxide pretreatment (121 oC, 2%) to understand the alterations in biomass cellular structure, which were correlated with saccharification yield. Results showed that alkali pretreatment preferentially removed lignin from the S2 of fibers, which was similar to the behaviors of coniferyl alcohol and aldehyde (lignin-CAA), exhibiting a positive correlation between removal of the two structures. Additionally, the cellulose microfibril angle was enlarged as the residence time increased during pretreatment. Scanning electron microscopy (SEM) analysis further suggested that pretreatment caused ultrastructure changes in cell walls with cracks formation on cell wall surface, especially in the areas adjacent to the cell corner middle lamellar (CCML). Accordingly, the cellulose digestibility of residues increased from 32.1% for the raw material to 53.7% for the treated samples obtained in 72 h. It can be concluded that the changes in topochemistry and ultrastructure of poplar cell walls resulting from alkali pretreatment mediated the efficiency of enzymatic hydrolysis of residues.

Multi-Scale Visualization of Dynamic Changes in Poplar Cell Walls During Alkali Pretreatment

Alkali pretreatment is a promising pretreatment technology that can effectively deconstruct plant cell walls to enhance sugar release performance. In this study, multi-scale visualization of dynamic changes in poplar cell walls during sodium hydroxide pretreatment (2% w/v, 121°C) was carried out by light microscopy (LM), confocal Raman microscopy (CRM) and atomic force microscopy (AFM). LM observations indicated that swelling occurred primarily in the secondary wall (S) but alkali had little effect on the cell corner middle lamella (CCML). Correspondingly, there was a preferential delignification in the S at the beginning of pretreatment, while the level of delignification in CCML (~88%) was higher than that in the S (~83%) for the whole process revealed by Raman spectra. It also suggested that prolonging residence time to 180 min would not remove lignin completely but cause rapid loss of carbohydrates, which was further visualized by Raman spectroscopy images. Furthermore, AFM measurements illustrated that pretreatment with alkali exposed the embedded microfibrils from noncellulosic polymers clearly, enlarged the diameter of microfibrils, and decreased the surface porosity. These results suggested that there was a synergistic mechanism of lignocellulose deconstruction regarding cell wall swelling, main components dissolution, and microfibril morphological changes that occurred during alkali pretreatment.

Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae.

BackgroundHeavy usage of gasoline, burgeoning fuel prices, and environmental issues have paved the way for the exploration of cellulosic ethanol. Cellulosic ethanol production technologies are emerging and require continued technological advancements. One of the most challenging issues is the pretreatment of lignocellulosic biomass for the desired sugars yields after enzymatic hydrolysis. We hypothesized that consecutive dilute sulfuric acid-dilute sodium hydroxide pretreatment would overcome the native recalcitrance of sugarcane bagasse (SB) by enhancing cellulase accessibility of the embedded cellulosic microfibrils.ResultsSB hemicellulosic hydrolysate after concentration by vacuum evaporation and detoxification showed 30.89 g/l xylose along with other products (0.32 g/l glucose, 2.31 g/l arabinose, and 1.26 g/l acetic acid). The recovered cellulignin was subsequently delignified by sodium hydroxide mediated pretreatment. The acid–base pretreated material released 48.50 g/l total reducing sugars (0.91 g sugars/g cellulose amount in SB) after enzymatic hydrolysis. Ultra-structural mapping of acid–base pretreated and enzyme hydrolyzed SB by microscopic analysis (scanning electron microcopy (SEM), transmitted light microscopy (TLM), and spectroscopic analysis (X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Fourier transform near-infrared (FT-NIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy) elucidated the molecular changes in hemicellulose, cellulose, and lignin components of bagasse. The detoxified hemicellulosic hydrolysate was fermented by Scheffersomyces shehatae (syn. Candida shehatae UFMG HM 52.2) and resulted in 9.11 g/l ethanol production (yield 0.38 g/g) after 48 hours of fermentation. Enzymatic hydrolysate when fermented by Saccharomyces cerevisiae 174 revealed 8.13 g/l ethanol (yield 0.22 g/g) after 72 hours of fermentation.ConclusionsMulti-scale structural studies of SB after sequential acid–base pretreatment and enzymatic hydrolysis showed marked changes in hemicellulose and lignin removal at molecular level. The cellulosic material showed high saccharification efficiency after enzymatic hydrolysis. Hemicellulosic and cellulosic hydrolysates revealed moderate ethanol production by S. shehatae and S. cerevisiae under batch fermentation conditions.

Improving Anaerobic Codigestion of Corn Stover Using Sodium Hydroxide Pretreatment

NaOH pretreatment of corn stover was investigated for anaerobic codigestion of corn stover with swine manure to shorten digestion time and improve biogas yield. Different NaOH concentration (2%, 4%, and 6%) at various temperatures (20 °C, 35 °C, and 55 °C) and 3 h of pretreatment time were tested for corn stover pretreatment. A C/N ratio of 25:1 in the substrates (corn stover and swine manure) was employed in the codigestion test. The results showed that the lignin removal rate of 54.57% to 79.49% was achieved through the NaOH pretreatment. The highest biogas production rate was obtained from the corn stover pretreated at 6% NaOH at 35 °C produced for 3 h, which was 34.59% higher than that from the untreated raw corn stover. The increase of methane yield was from 276 to 350 mL/g VS. On the average, the reducing sugar content of corn stover decreased to 126.7 mg/g after digestion. Digestion time (T80) of pretreated corn stover was shortened from 18 days to 12–13 days. NaOH pretreatment not only effectively shortened the digestion time for anaerobic codigestion of corn stover with swine manure by removing the lignin from the corn stover but also improved biogas yield of corn stover. The pretreatment condition of 6% NaOH at 35 °C for 3 h is recommended for the pretreatment of corn stover.