Effect Of Alkali Pretreatment Research Articles

Effect of low-temperature thermal-alkali pre-treatment on waste activated sludge solubilisation

The study was aimed to examine the effects of alkaline and thermal-alkaline pre-treatment on sewage sludge solubilisation with different alkali and its doses ranging from 40 mg alkali/g TS to 120 mg alkali/g TS. Initially, the effect of alkali pre-treatment was monitored with four alkali at room temperature, to further enhance soluble chemical oxygen demand (sCOD) and reduce treatment time, thermal-alkaline pre-treatment was performed with varying temperature from 40 to 70 °C. To explore and optimise the effects of temperature, alkali, and alkali doses on COD solubilisation, response surface methodology was employed. Statistical analysis of the variance was conducted to identify the relationship between experimental data and the proposed model. The thermal-alkaline process was optimised for maximum COD solubilisation with optimal conditions achieved at 65.61 °C of 66.57 mg alkali /g TS for NaOH and 27 °C of 20 mg/g TS for KOH. The maximum COD solubilisation achieved at these optimised conditions for NaOH and KOH was 21.28 % and 16.13 %, respectively. The results demonstrated a significant improvement in protein and carbohydrate concentration and a 16–20 % reduction in sludge solid content after thermal-alkali pre-treatment.

The Effect of Alkali Pretreatment and Different Parts of Sargassum polycystum Thallus on Alginic Acid Attributes

Alginic acid is an intermediate product in the alginate extraction process. In this study, alginic acid was generated from three separate sections of the thallus. The study aimed to define the influence of alkali solvents for pretreatment and the thallus parts from S. polycystum to produce alginate. Thus, this study identifies the proper utilization of seaweed as a source of alginate. The extraction procedure to obtain alginic acid was performed using Na2CO3 at a 2% concentration. The pretreatment improved the quality before extraction by soaking in KOH as a solvent. The statistical analysis was used to define significant differences in the pretreatment and thallus parts of the S. polycystum using ANOVA and the Tukey test as the post hoc. Alkali pretreatment and thallus sections substantially influence alginic acid yield, viscosity, and gel strength. Yield, ash content, moisture, pH, viscosity, whiteness degree, and gel strength of the best alginic acid chosen (pretreatment with KOH 0.90% from the basal section) were around 21.51 %, 10.34 %, 7.04 %, 2.54, 53.37 cP, 57.91 %, and 58.80 g/cm2, respectively. Except for the ash content parameter, the qualities of the alginic acid generated satisfied the standard. In conclusion, it is a better understanding of the alginate production from different thallus parts, making utilization more effective.

Effects of alkali pretreatment on the flotation of spodumene and feldspar

The surface chemistry and morphology of minerals produced by alkali pretreatment affects their flotation behaviors. This study systematically investigated the impact on the mineral surface dissolution using NaOH as a modifier, which could modify the surface properties of minerals and improve the floatability difference between spodumene and feldspar. Various characterizations including flotation experiments, flotation kinetics analysis, SEM analysis, microcalorimetry analysis, zeta potential measurements, XPS analysis and ICP-MS analysis were conducted. Single minerals and actual ore flotation experiment results were in good agreement, and the flotation grade and recovery of Li2O in spodumene concentrates increased by 1.11 % and 6.99 %, respectively, after NaOH pretreatment. The flotation kinetics results demonstrated the cumulative recoveries of spodumene exhibited the best agreement with the first-order kinetic model and the flotation kinetic constant was improved after alkali pretreatment. Microcalorimetric results indicated the absolute values of the reaction heat for spodumene were higher than that of feldspar reacted with collectors after the alkali pretreatment. XPS and ICP results demonstrated the amounts of Al active sites on the spodumene surface was significantly increased after alkali pretreatment compared to that on the feldspar surface, improving the selective adsorption of NaOL.

Effects of different pretreatments combined with steam explosion on the properties of bamboo fibers

Bamboo pretreatment is a key technology for the preparation of bamboo fibers (BFs) for composites. This study examined the properties of BFs prepared by steam explosion (SE) BFs following pretreatment by enzyme, alkali, and salt. The microstructure, functional groups, crystallinity, and surface chemical elements of BFs were characterized by environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that bamboo could be separated into fiber bundles through SE after pretreatment. The separation of BFs pretreated by enzyme and alkali were better, but colloid remained and was able to stick the fibers together. Through performing different pretreatments before SE, the lignin and hemicellulose of BFs were partially removed, and alkali pretreatment had the best effect on lignin removal. The crystal structure of the BFs did not change significantly, and the crystallinity of BFs was highest at 2 MPa and 6 min when pretreated by alkali. The XPS results showed that the effect of alkali pretreatment at 2 MPa for 6 min was the best.

Quantitative visualization of subcellular lignocellulose revealing the mechanism of alkali pretreatment to promote methane production of rice straw

BackgroundAs a renewable carbon source, biomass energy not only helps in resolving the management problems of lignocellulosic wastes, but also helps to alleviate the global climate change by controlling environmental pollution raised by their generation on a large scale. However, the bottleneck problem of extensive production of biofuels lies in the filamentous crystal structure of cellulose and the embedded connection with lignin in biomass that leads to poor accessibility, weak degradation and digestion by microorganisms. Some pretreatment methods have shown significant improvement of methane yield and production rate, but the promotion mechanism has not been thoroughly studied. Revealing the temporal and spatial effects of pretreatment on lignocellulose will greatly help deepen our understanding of the optimization mechanism of pretreatment, and promote efficient utilization of lignocellulosic biomass. Here, we propose an approach for qualitative, quantitative, and location analysis of subcellular lignocellulosic changes induced by alkali treatment based on label-free Raman microspectroscopy combined with chemometrics.ResultsFirstly, the variations of rice straw induced by alkali treatment were characterized by the Raman spectra, and the Raman fingerprint characteristics for classification of rice straw were captured. Then, a label-free Raman chemical imaging strategy was executed to obtain subcellular distribution of the lignocellulose, in the strategy a serious interference of plant tissues’ fluorescence background was effectively removed. Finally, the effects of alkali pretreatment on the subcellular spatial distribution of lignocellulose in different types of cells were discovered.ConclusionsThe results demonstrated the mechanism of alkali treatment that promotes methane production in rice straw through anaerobic digestion by means of a systemic study of the evidence from the macroscopic measurement and Raman microscopic quantitative and localization two-angle views. Raman chemical imaging combined with chemometrics could nondestructively realize qualitative, quantitative, and location analysis of the lignocellulose of rice straw at a subcellular level in a label-free way, which was beneficial to optimize pretreatment for the improvement of biomass conversion efficiency and promote extensive utilization of biofuel.

Effects of alkali pretreatment on lyocell woven fabric and its influence on pilling properties

Experiments were conducted to study the influence of various concentration of alkalis on the pilling properties of lyocell fabrics. Generally, the lyocell fabric has more tendency of pill formation due to fibrillation properties. Therefore, present work is focused on the impact of alkali pretreatments with various concentration from 0.5 mol/L to 3 mol/L on lyocell with their pilling resistance. Due to the morphological changes, pilling results are attributed to the alkali types and their concentration. Treatment with TmAH and LiOH at 2 mol/L shows the reduction of a number of fibrils leading to reduce the pill generation significantly. Carboxyl content and iodine sorption value are analyzed to find the impact of alkali on the accessible region and structural changes respectively, also surface modification was observed by SEM to confirm the surface characteristics. Overall results shows that the reduction of fibrillation leads to better pilling resistance of lyocell fabric.

Structural and morphological studies on alkaline pre-treatment of oil palm empty fruit bunch (OPEFB) fiber for composite production

Abstract Empty fruit bunch from the palm oil industry can be classified as a popular source among various waste streams in Malaysia as one of recyclable raw material that offered broad useful applications especially in bio-composite production. This is due to its abundantly generation, inexpensive and high mechanical properties. However, one of the major weakness of oil palm empty fruit bunch (OPEFB) is their hydrophilic characteristic that will cause the weak binding between the interaction of fiber and polymer matrix during the composite production. Thus, the pretreatment needs to be done in order to improve their compatibility. In this work, the effect of alkali pretreatment by using different alkaline solutions of 15% (w/v) concentration at 130°C and for 40 minutes with fiber to solution ratio at 1:20 have been investigated. Their physicochemical and structural behavior were studied in details by several analysis which are Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The experimental result showed that FTIR analysis expressed quite same spectra for NaOH and KOH treated OPEFB fiber in term of the decreasing in ester linkage stretching, aromatic groups and also lignin. SEM observation also contributed to highlight these changes by exposing their structure and morphology of treated fiber. Meanwhile XRD analysis clearly observed that the highest crystallinity index was 60.8% by KOH solution just slightly different from the NaOH solution by 0.5% compared to Al(OH)3 solution by 22.9%. From this finding, the modification of OPEFB fiber through alkaline pretreatment by three different alkali solution gave some changes to the nature of OPEFB fiber and can be seen clearly that both NaOH and KOH gave better perspective in term of the hydrophilicity reduction and surface effectiveness as well as cellulose structure improvement. Hence these transformations literally affected and contributed to the improvement in bonding strength with thermal stability that can be applied generally for advanced polymer composite production.

Effects of Alkali Pre-treatment, Total Solid Content, Substrate to Inoculum Ratio, and pH on Biogas Production from Anaerobic Digestion of Mango Leaves

The present study investigated the effects of five parameters [alkali (NaOH) pretreatment (doses and durations), total solid (TS) content, substrate to inoculum ratio (S/I), and pH] on biogas production from anaerobic digestion of mango leaves. To evaluate these parameters effects 26 batch experiments were conducted. Which included: NaOH pretreatment (doses: 0, 0.1, 0.2, 0.3, and 0.4 mol/L and durations: 4, 6, 8, 10, and 12 h), TS content (4, 6, 8, 10%), S/I (15, 20, 25, and 30%), and pH (6.5, 7.0, 7.5, and 8.0). Also, the kinetics of biogas production was studied by using three models: first order kinetic, Cone, and modified Gompertz models. It was found that the optimum conditions were: NaOH dose with 0.2 mol/L, NaOH duration for 10 h, TS content with 8%, S/I ratio with 20%, and pH of 7.5. These optimum situations gave the highest production with 616.2, 644.0, 1968.4, 1467.2, and 1488.6 mL/gVS, respectively. Cone model showed the best fit followed by modified Gompertz model and finally first order kinetic model. These results proved the applicability of mango leaves as a good source for renewable methane-rich energy, and the impact of NaOH pretreatment, TS, S/I, and pH on the biogas/methane yield.

Anaerobic Co-digestion of Giant Reed for Biogas Recovery

This study investigated the feasibility of anaerobic co-digestion of giant reed (GR) inoculated with waste manure as a co-substrate for biogas production. The performance of co-digestion was evaluated in 4 anaerobic digesters operated in batch mode at different conditions. The effects of alkali pretreatment with NaOH (4% w/v) solution, inoculum type, and thermal condition were studied. The results demonstrated that the alkali-pretreatment of GR enhanced the biogas generation by about 15% at mesophilic conditions. Thermophilic conditions enhanced the biogas recovery from both alkali-free and alkali pretreated GR by 15% and 127%, respectively. The kinetic study of the co-digestion process of GR for biogas recovery suggested a significant agreement between measured and predicted values obtained by Modified Gompertz Model with correlation coefficients ≥ 0.98 indicating favorable conditions for the co-digestion of inoculated GR.

Recovery of organic resources from sewage sludge of Al-enhanced primary sedimentation by alkali pretreatment and acidogenic fermentation

Primary sludge from wastewater treatment is of rich organic contents that can be resource for recovery. However, the sludge derived from the chemically enhanced primary sedimentation (CEPS), especially using Al-based coagulants, features a rather low biodegradability and treatability due to the agglomeration of solid matters by the coagulant. In the present study, alkali pretreatments by three chemicals (NaHCO3, Na2CO3 and NaOH) were applied to disintegrate Al-based CEPS sludge (Al-sludge) aggregates and improve its hydrolysis and biodegradability for fermentation and organic recovery. Results showed that alkali pretreatment significantly reduced the Al-sludge particle size and accelerated the release of the enmeshed organics. NaHCO3 exhibited the best pretreatment result. At ambient temperature, the yield of volatile fatty acids (VFAs) of the Al-sludge pretreated by Na2CO3 (initial pH 10) was improved by four times compared to the untreated sludge, resulting from both the improved abiotic and biotic hydrolysis effects. The effect of alkali pretreatment on Al-sludge was found to be mainly attributable to the pH adjustment rather than the alkalinity increase. Illumina MiSeq sequencing revealed that protein-fermenting bacteria Treponema and Bacteroides became dominant during fermentation of the alkali pretreated sludge. By PACl-based CEPS and enhanced sludge acidogenesis, around 17% of organics in municipal wastewater can be recovered, mainly in the form of VFAs, which is significantly greater than 6% by the conventional primary sedimentation and sludge fermentation.

Seeking to enhance the bioenergy of municipal sludge: Effect of alkali pre-treatment and soluble organic matter supplementation

The aim of this research is to enhance the mesophilic anaerobic digestion of municipal sludge from Cadiz-San Fernando (Spain) wastewater treatment plant at 20days hydraulic retention time (HRT). Two different strategies were tested to improve the process: co-digestion with the addition of soluble organic matter (1% v/v); and alkali sludge pre-treatment (NaOH) prior to co-digestion with glycerine (1% v/v). Methane production (MP) was substantially enhanced (from 0.36±0.09 L CH4 l/d to 0.85±0.16 L CH4 l/d), as was specific methane production (SMP) (from 0.20±0.05 L CH4/g VS to 0.49±0.09 L CH4/g VS) when glycerine was added. The addition of glycerine does not seem to affect sludge stability, the quality of the effluent in terms of pH and organic matter content, i.e. volatile fatty acids (VFA), soluble organic matter and total volatile solid, or process stability (VFA/Alkalinity ratio<0.4). Alkali pre-treatment prior to co-digestion resulted in a high increase in soluble organic loading rates (more than 20%) and acidification yield (more than 50%). At 20days HRT, however, it led to overload of the system and total destabilization of the mesophilic anaerobic co-digestion of sewage sludge and glycerine.

Processing effects on bioactive components and functional properties of moringa leaves: development of a snack and quality evaluation.

The effect of alkali pre-treatment on the nutritional, anti-nutritional and functional properties of moringa (Moringa oleifera) leaf flour (MLF), and sensory assessment of MLF-based snack product was investigated. The pre-treatment reduced the content of anti-nutrients, but improved the functional properties of MLF. The MLF-based ready-to-eat puffed snack exhibited high protein (21.6g/100g) and dietary fiber (14.8g/100g) contents while it contained a low fat content of 3.7g/100g. The HPLC analysis of phenolics revealed that chlorogenic and gallic acids were the predominant phenolic acids present in the raw leaf flour, whereas p-coumaric, caffeic and gallic acids were the major phenolic acids in the pre-treated leaf flour. Flavonoids such as catechin, kaempferol, rutin and luteolin were present in both MLFs and the prepared snack. Overall sensory quality indicated that the snacks had acceptable textural attributes and improved nutritional profile at the 20% level of substitution. It is possible to develop a ready-to-eat convenience food product with good functional and nutritional properties using pre-treated moringa leaf.

Microstructural, Mechanical, and Physicochemical Behaviours of Alkali Pre-treated Oil Palm Stalk Fibres

The effect of alkali pre-treatment (sodium hydroxide, NaOH) on the microstructural, mechanical, and chemical composition of oil palm stalk fibres (OPSF) is reported for future bioconversion processes. The OPSF was pre-treated with various concentrations of NaOH (5, 10, 20, 30, and 40% w/v). Scanning electron microscopy analysis revealed that 5% w/v alkali concentration caused complete removal of silica bodies and waxy layers, whereas pronounced degradation of the fibres occurred at 40% w/v NaOH concentration. Mechanical test results showed that the maximum elastic modulus of untreated OPSF was 2.5 GPa and the modulus was not sensitive to alkali concentration. Permanent set (plastic strain) and viscoelastic behaviours of OPSF were observed from the loading-unloading and stress relaxation test results, respectively. Agreement was observed between the Prony series viscoelastic model and test results, which provided further evidence of the viscoelastic behaviour of OPSF.

Comparison of thermophilic microaerobic and alkali pretreatment of sugarcane bagasse for anaerobic digestion

Effects of alkali pretreatment (AP) and thermophilic microaerobic pretreatment (TMP) on the AD of sugarcane bagasse were investigated and compared.

BIOETHANOL PRODUCTION FROM WATER HYACINTH BIOMASS USING ISOLATED FUNGAL STRAIN FROM LOCAL ENVIRONMENT

Fermentation of sugar released by saccharification of lignocellulosic materials produce bioethanol which is a renewable energy source. There are some technological barriers such as pretreatment, saccharification of cellulose and hemicellulose matrix, and simultaneous fermentation of hexose and pentose sugars which needs to be addressed for efficient conversion of lignocellulosic biomass to bioethanol. The present study evaluated water hyacinth as feedstock for bioethanol production, with the possible strategies by which the conversion to sugars from water hyacinth can be maximized. Effect of alkali pretreatment on WHB was studied. In this study, suitability of the feedstock for production of fermentable sugars using crude enzymes produced on site from isolated fungal strain (F13) from the local environment at CSIR-CMERI, Durgapur (Latitude: 23.55 O ; Longitude: 87.31 O ) was demonstrated where in the highest xylose yield obtained was 236.56 mg/g . Cellulase and xylanase activity was determined for biomass saccharification process. Finally , fermentation of the hydrolysate using pentose fermenting yeast, Pichia stipitis yielded an ethanol concentration of 3.193g/L.

Effect of hemicellulase, cellulase, xylanase and alkali pretreatment on the saccharification of Miscanthus sacchariflorus var. No.1

The optimum conditions for enzymatic treatment of Miscanthus sacchariflorus var. No. 1, a newly developed genotype in Korea, to produce water soluble carbohydrate were investigated using statistical methods. The individual effects of cellulase, hemicellulase and xylanase on water soluble carbohydrate (WSC) production were investigated. Then, the effects of combined addition of enzyme and M. sacchariflorus were evaluated and optimized using a Box Benhken design (BBD) and response surface model (RSM). Enzyme treatment was performed in a 45°C water bath for 12 h. The effects of alkali pretreatment conditions on enzymatic saccharification of M. sacchariflorus were investigated using the Taguchi design. Hemicellulase was the effective enzyme for WSC yield (mg of produced glucose/g M. sacchariflorus). This enzyme then became the fixed component, with cellulase, xylanase and M. sacchariflorus applied as variables. The optimum blend of enzymes was determined to be hemicellulase 5.0 U/ml, cellulase 8.0 U/ ml and xylanase 6.0 U/ ml. Incubation time, concentration of NaOH and M. sacchariflorus level were used as variables for investigation of alkali pretreatment conditions effects. The pretreatment was performed at 80°C and the optimized enzyme mixture was used. The maximum WSC yield was achieved using a 1 h reaction time, 1% NaOH and 50 g/L of M. sacchariflorus. Through a series of experiments, WSC yield was improved from 10 mg glucose/g M. sacchariflorus before optimization to 220 mg glucose/g M. sacchariflorus after optimization. Key words: Miscanthus sacchariflorus var., enzymatic saccharification, cellulase, hemicellulase, xylanase.

The effect of alkali pre-treatment on formation and adsorption of silver nanoparticles on cotton surface

This study is an attempt to investigate the feasibility of alkali pre-treatment to activate surface hydroxyl groups of cellulose fibers in order to enhance the deposition efficiency of silver nanoparticles (AgNPs) onto cotton fabrics. Cotton samples were pre-treated with various alkali solutions containing different earth metal hydroxides (LiOH, NaOH, and KOH). The as-prepared samples were then treated with aqueous silver nitrate followed by reduction treatment with aqueous ascorbic acid, which caused in situ formation of AgNPs on fiber surfaces. The surface structure of the fabrics was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis, and colorimetric data. The amount of silver was measured by using inductively coupled plasma-optical emission spectrometer (ICP-OES). Antimicrobial activity was measured against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria. It was established that alkali pre-treatment had a substantial effect on the formation and adsorption of AgNPs on the fibers. Alkali pre-treated samples were homogeneously coated by AgNPs with high surface coverage. Alkali type had significant effect not only on the amount of AgNPs on the surface but also on its size. High antibacterial activity against both Gram-positive and Gram-negative strains was also demonstrated, even after 10 cycles washing.

Effect of Alkali Pretreatment on the Structural Properties and Enzymatic Hydrolysis of Corn Cob

An effective alkali pretreatment which affects the structural properties of cellulose (corn cob) has been studied. The pretreatment of corn cob was carried out with different combinations of alkali at varying temperatures. The most effective pretreatment of corn cob was achieved with 1 % alkali at 50 °C in 4 h. The crystallinity index (CrI) and specific surface area (SSA) of untreated corn cob was 39 % and 0.52 m(2)/g wherein after alkali pretreatment CrI decreased to 15 % and SSA increased to 3.32 m(2)/g. The fungal organism was identified as Penicillium pinophilum on the basis of ITS sequence. At 5 % substrate concentration using a complete cellulase from Penicillium pinophilum the hydrolysis of untreated corn cob with 5, 10 and 20 FPU/g enzyme loadings were 11 %, 13 % and 16 %, whereas after alkali treatment the hydrolysis increased to 78 %, 90 % and 100 %, respectively. Further hydrolytic potential of commercial cellulases viz. Accellerase™ 1,000, Palkofeel-30 and Palkocel-40 were investigated under similar conditions.

In situ synthesis of silver nanoparticles on alkali-treated cotton fabrics

Cotton fabrics were alkali-treated with sodium hydroxide at different concentrations in the range from 1 M to 6 M in order to investigate the effect of alkali treatment on the formation of silver nanoparticles. Alkali-treated fabrics were dipped into the silver nitrate solution followed by chemical reduction, which caused in situ formation of silver nanoparticles on the surface of fabrics. As-prepared fabrics were characterized by scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction analysis and also antimicrobial test was carried out. In addition, the color variation, antibacterial durability, and mechanical properties of the fabrics were assessed. The considerable effect of alkali pre-treatment on loading and stabilizing silver nanoparticles was demonstrated. Fabrics treated at higher sodium hydroxide concentrations have higher silver content. Silver nanoparticles are homogeneous and evenly distributed on fibers with high surface coverage. Treated fabrics exhibit strong antibacterial activity against Escherichia coli and Staphylococcus aureus, even after 10 laundering cycles. This procedure is facile, cost-effective and versatile and provides a simple route to manufacturing of cotton textiles with high silver content.

The Effect of Alkali Pretreatment of Rice Straw for Anaerobic Digestion

The anaerobic digestion is an efficient utilization way of crop residues and alkali pretreatment are often used to enhance the degradation. Alkali pretreatment based on Ca(OH)2 addition of rice straw was studied.The tests of 3 g/l, 9 g/l Ca(OH)2 addition had an significant effect on enhancing solubilization and rapid acidification, the results were 1521.2 gCOD/l and 935 ml biogas yield of 3 g/l Ca(OH)2 addition, 1600.7 gCOD/l and 1200 ml biogas yield of 9 g/l Ca(OH)2 addition , compared to 405.5 gCOD/l and 1162 ml of control( 0 g/l Ca(OH)2 addition) . The results also showed that tests of 15 g/l , 21 g/l of Ca(OH)2 addition were entirely inhibited to biogas yield. The result of the present work implied that although alkali pretreatment to rice straw can significantly enhance solubilization, the inhibition to methane yield was liable to occur.