Potassium Hydroxide Pretreatment Research Articles

Statistical Optimization of Tween-80-Assisted Potassium Hydroxide Pretreatment and Enzymatic Hydrolysis for Enhancing Sugar Yields from Corn Cob

With the addition of Tween 80, potassium hydroxide pretreatment and enzymatic hydrolysis were statistically optimized to maximize sugar yields from corn cob (CC). The results indicated that the sugar yields from CC could be influenced significantly by the potassium hydroxide concentration, temperature and time during pretreatment. The optimized pretreatment conditions were as follows: potassium hydroxide, 46 g·L−1; Tween 80, 3.0 g·L−1; solid dose, 200 g·L−1; temperature, 78 °C; and time, 50 min. After optimization, the lignin reduction and recoveries of cellulose and hemicellulose were 89.7%, 97.8% and 68.0%, respectively. In addition, sugar production could also be influenced by the biomass loading, enzyme loading and reaction time. A maximal glucose production (518.48 mg·gds−1, milligrams per gram of dry substrate) and xylose production (351.14 mg·gds−1), 97.2% cellulose conversion and 82.9% hemicellulose conversion from CC could be obtained when the biomass loading was 195 g·L−1 and the enzyme loading was 8.9 FPU·gds−1 (filter paper activity units per gram of dry substrate) and when the Tween 80 concentration was 3.0 g·L−1 at 50 °C for 30.4 h during hydrolysis. This is the first systematic study of combined Tween 80 pretreatment of CC by potassium hydroxide and hydrolysis of CC by cellulase preparation to increase sugar production.

Kraft lignin recovery from de-oiled Jatropha curcas seed by potassium hydroxide pretreatment and optimization using response surface methodology

The present study explores resource recovery from the de-oiled Jatropha curcas seed (DJS) using alkaline pretreatment. Potassium hydroxide (KOH) was utilized for the alkaline hydrolysis at a solid loading rate of 10 % w/v for the kraft lignin (KL) recovery. The process variables optimized were reaction time (6.36–73.63 min), temperature (85.68–156.3 °C), and KOH concentration (0.61–12.38 % w/w). Response surface methodology was used to optimize the process parameters. The maximum amount of KL recovered under optimal conditions was observed to be 89.6 %. The functional group changes in treated and untreated DJS were explored through Fourier transform infrared spectroscopy (FTIR) analysis. 1H NMR and FTIR techniques were employed to characterize recovered lignin. Nitrobenzene oxidation of the lignin was performed to understand the lignin monomer profile. The recovered lignin has an S/G ratio of 0.36. The pretreated DJS biomass can be subjected to enzymatic hydrolysis for enhanced sugar yield.

Enhancement of biomethane production and decomposition of physicochemical structure of corn straw by combined freezing-thawing and potassium hydroxide pretreatment

Enhancement of biomethane production and decomposition of physicochemical structure of corn straw by combined freezing-thawing and potassium hydroxide pretreatment

Effect of flotation and potassium hydroxide pretreatment of an antimonial refractory ore on the extraction of silver by cyanidation

In this study, potassium hydroxide leaching as pretreatment before cyanide leaching of a flotation concentrate of an antimonial refractory gold-silver ore was investigated. The ore assaying 1157 g/t Ag and 3.96 g/t Au was found to be composed of predominantly quartz, barite, kaolinite, clay, mica/chlorite, and dolomite/ankerite. Electrum, pyrargyrite, acanthite, and tetrahedrite were identified to be the most important silver-bearing phases in the ore. A flotation concentrate with a high silver grade (0.6% Ag) at 94.8% silver recovery, as well as high recoveries of antimony (86.8%), zinc (98.6%), and lead (84.7%), was produced in flotation tests. Gold recovery to the concentrate was limited to be 74.4%. The cyanide leaching of the concentrate has yielded consistently low extractions of silver (≤13.8%) confirming the refractory nature of the ore. Alkaline pretreatment of the concentrate was performed in which effects of potassium hydroxide concentration (0.05–3 mol/L) and temperature (20–80 °C) on the removal of antimony and subsequent cyanide leaching of silver were investigated. Extraction of antimony was substantially enhanced from 11.5 to 93.8% with increasing the concentration of KOH and temperature. The activation energy (Ea) for leaching of antimony was calculated to be ≈17 kJ/mol with the implication of a diffusion-controlled leaching reaction. Silver extraction in the cyanidation improved from 13.8% to 95.7% as a consequence of the removal of antimony (i.e. 93.8%) by the alkaline pretreatment. This improvement in the silver extraction can be attributed to the decomposition of silver-bearing antimonial minerals i.e. pyrargyrite, and tetrahedrite in the concentrate. These findings confirm that potassium hydroxide leaching is a suitable approach for the pretreatment of antimonial refractory silver ores.

Three-Dimensional Hierarchical Porous Carbon Cathode Derived from Waste Tea Leaves for the Electrocatalytic Degradation of Phenol.

Tea leaves have been explored as an economically viable and environmentally friendly source of biomass carbon. Tea leaf porous carbon (TPC) with a three-dimensional (3D) structure was prepared by a potassium hydroxide pretreatment and high-temperature calcination method, and the preparation process was simple and self-templating. The prepared TPC has a large specific surface area (1620.05 m2 g-1), three-dimensional multilayer pore structure, uniform pore size, and high oxygen content (15.51%). Both the calcination temperature and the activation level have an effect on the structure and performance of the TPC. The TPC electrode can generate a large amount of hydrogen peroxide in the initial stage of the degradation process, thereby increasing the amount of hydroxyl radicals generated and removing organic pollutants. Therefore, phenol was used to test the degradation effects and evaluate the degradation performance of TPC. Under suitable degradation conditions, TPC-800-2 showed a 95.41% degradation rate after 120 min of degradation, which is superior to that of other calcination temperatures and activation levels. The removal efficiency of chemical oxygen demand after 180 min was 90.0% and showed good stability after being used 20 times. Our work illustrates that a simple, high-performance self-templating synthetic strategy for producing novel 3D-TPC from biomass sources can play a significant role in the actual wastewater treatment of other biomass materials.

A clean and effective potassium hydroxide pretreatment of corncob residue for the enhancement of enzymatic hydrolysis at high solids loading.

Corncob residue (CCR) is an economic feedstock with enormous potential for the production of bioethanol. In this work, potassium hydroxide (KOH) pretreatment of CCR was investigated under relatively mild conditions, and the effectiveness of KOH pretreatment was evaluated by enzymatic saccharification at high solid loading. Results showed that after KOH pretreatment (16 wt% KOH dosage at 70 °C for 90 min) and the enzymatic hydrolysis at 20% solids loading and 20 FPU g−1-substrate of cellulase loading, the glucose yield could reach up to about 91%, which was over 90% higher compared to the raw CCR without KOH pretreatment. Correspondingly, about 89% of lignin and 79% of extractives were removed after KOH pretreatment. In addition, the spent liquor of KOH pretreatment containing sylvite could be used as lignin-based fertilizer based on the concept of biorefinery. In this case, the entire process for the production of fermentable sugars was clean and sustainable, which is very vital for the conversion of lignocelluloses to bioenergy or chemicals.

A sustainable and effective potassium hydroxide pretreatment of wheat straw for the production of fermentable sugars

The development of sustainable and effective pretreatment technology is of critical importance for the conversion of lignocelluloses into bioethanol. In this work, KOH pretreatment of wheat straw with the supplement of anthraquinone (AQ) and sodium lignosulfonate (SLS) was investigated under the relatively mild conditions. The effectiveness of KOH pretreatment was evaluated by enzymatic saccharification. It was found that after the KOH pretreatment with 15% KOH, 0.1% AQ and 2% SLS at 120 °C for 40 min, the final total sugar yields (glucose + xylose + soluble xylan) could reach up to 80%, which was 16% higher as compared to the KOH pretreatment without addition of AQ and SLS under the same conditions. In addition, the spent liquor could be reused twice to maintain a relatively good effectiveness of pretreatment, and it could be used to produce fertilizer due to the high content of potassium.

Influence of potassium hydroxide pretreatment on the extraction of gold and silver from a refractory ore

Potassium hydroxide alkaline pretreatment of a refractory gold–silver ore containing 20g/t Au and 220g/t Ag was investigated with the purpose to evaluate its effectiveness on the extraction of gold and silver. The presence of antimony minerals such as stibnite (Sb2S3), zinkenite (Pb9Sb22S42) and andorite (Sb3PbAgS6) is the main reason for the refractory nature of the ore. Silver occurs as andorite, a Au–Ag alloy, tetrahedrite [(Cu,Fe,Zn,Ag)12Sb4S13] and in minor amounts in zinkenite whereas gold is associated with quartz and the antimony minerals. Cyanidation tests of the as-received ore show that the extraction of gold and silver is consistently low (i.e. ≤49.3% and ≤18.7%, respectively) over the leaching period of 24h. The effects of potassium hydroxide concentrations (0.5–5mol/L), temperature (20–80°C) and particle size (5–50μm) on the removal efficiency of antimony were investigated. Accompanying the removal of antimony, gold and silver recoveries improved with increases in the KOH concentrations (5mol/L) and temperature (80°C), and a decrease in the particle size (5μm). Gold and silver extractions during subsequent cyanidation were improved to 87.6% and 94.5%, respectively, corresponding to 85.5% Sb removal by alkaline pretreatment. The antimony removal is also evidenced by the disappearance of stibnite, zinkenite and andorite which formed 4.57wt.% of the original ore. The residual amount of antimony is due to the presence of unreactive Sb oxide and Pb–Sb sulphate minerals, sphalerite and tetrahedrite in the ore and Sb-bearing Pb sulphate compound(s) that formed during pretreatment. These findings indicate that potassium alkaline leaching can be an effective pretreatment method for refractory antimonial gold–silver ores.

Acid resistance of goethite in nickel laterite ore from Western Australia. Part II. Effect of liberating cementations on acid leaching performance

The acid resistance of some West Australian laterite ores has been reported to be associated with its cementation structure at submicron level. Although closely related, iron and silicon are found not to be intimately mixed in the goethite-silica/silicate cementations from the current Energy Filtered Transmission Electron Microscopy examination. The round or diamond tips of the liberated goethite crystals suggest slow crystal growth in high silicate conditions. The effect of pre-treating the cementation structure by potassium hydroxide liquor digestion upon the atmospheric pressure acid leaching performance is also studied in this paper. Both particle size analysis using laser diffraction and direct imaging using Transmission Electron Microscopy confirm the effective disintegration of the cementations and the liberation of goethite crystals. As a result, the leaching rates of these nickel laterite ores increase by more than 6 times; nickel recoveries of these laterite ores are also increased from under 50% to near 90% after 16h acid leaching. The accelerating effect of the potassium hydroxide pre-treatment upon acid leaching rates verified that an envelope of silica and/or silicates hindered the contact between acid and goethite crystals during atmospheric leaching of these nickel laterite ores.

Potential of Potassium Hydroxide Pretreatment of Switchgrass for Fermentable Sugar Production

Chemical pretreatment of lignocellulosic biomass has been extensively investigated for sugar generation and subsequent fuel production. Alkaline pretreatment has emerged as one of the popular chemical pretreatment methods, but most attempts thus far have utilized NaOH for the pretreatment process. This study aimed at investigating the potential of potassium hydroxide (KOH) as a viable alternative alkaline reagent for lignocellulosic pretreatment based on its different reactivity patterns compared to NaOH. Performer switchgrass was pretreated at KOH concentrations of 0.5-2% for varying treatment times of 6-48 h, 6-24 h, and 0.25-1 h at 21, 50, and 121 °C, respectively. The pretreatments resulted in the highest percent sugar retention of 99.26% at 0.5%, 21 °C, 12 h while delignification up to 55.4% was observed with 2% KOH, 121 °C, 1 h. Six pretreatment conditions were selected for subsequent enzymatic hydrolysis with Cellic CTec2® for sugar generation. The pretreatment condition of 0.5% KOH, 24 h, 21 °C was determined to be the most effective as it utilized the least amount of KOH while generating 582.4 mg sugar/g raw biomass for a corresponding percent carbohydrate conversion of 91.8%.

Bio-antifelting of wool based on mild methanolic potassium hydroxide pretreatment

Covalently bound lipids cover the wool surface and make enzymatic degradation of wool scales very difficult. In this paper, methanolic potassium hydroxide (MPH) pretreatment was used prior to enzymatic treatment of wool with protease, aiming at hydrolyzing the outmost lipids on the wool surface and promoting the subsequent proteolytic reaction. The efficacy of lipid removal from the fiber surface and the properties of the protease-treated wool were evaluated. The results indicated that mild MPH pretreatment with 0.10 mol/L MPH for 10 min improved the wettability of the wool without adverse impacts on its mechanical properties. The wetting time and area shrinkage of the wool fabric reached 0.5 s and 5.6%, respectively, and the strength loss was within the acceptable range. Pretreatment with high concentrations of MPH for longer times led to significant damage to the wool fibers and caused heavy strength loss, without improving the antifelting properties after protease treatment. Thus, the combination of mild MPH and protease treatments endowed the wool with desirable properties in contrast to the treatment with protease alone.

Characterization of Corn Cobs from Microwave and Potassium Hydroxide Pretreatment

Characterization of Corn Cobs from Microwave and Potassium Hydroxide Pretreatment

Optimization of Two-stage Pretreatment from Soybean Hull for Efficient Glucose Recovery

Soybean hull is an attractive feedstock for glucose production. To increase the glucose conversion in acid hydrolysis, a pretreatment method combined steam explosion with alkali pretreatment for soybean hull was studied. For first step pretreatment, steam explosion conditions (log Ro 2.45) were optimized to obtain maximum solid recovery and cellulose content. In the second step pretreatment, the conditions for potassium hydroxide pretreatment of steam exploded soybean hull were optimized by using RSM (response surface methodology). The optimum conditions for minimum lignin content were determined to be 0.6% potassium hydroxide concentration, <TEX>$70^{\circ}C$</TEX> reaction temperature and 198 min reaction time. The predicted lignin content was 2.2% at the optimum conditions. Experimental verification of the optimum conditions gave the lignin content in similar value with the estimated value of the model. Finally, glucose conversion of pretreated soybean hull using acid hydrolysis resulted in <TEX>$97.1{\pm}0.4%$</TEX>. This research of two-step pretreatment was a promising method for increasing the glucose conversion in the cellulose-to-glucose process.

Cathode Spot Behavior Variation in Oxide Layer Removal Caused by Potassium Hydroxide Pre-treatment

Cathode Spot Behavior Variation in Oxide Layer Removal Caused by Potassium Hydroxide Pre-treatment

Sialylation patterns of the mouse parotid secretory granules. Combined deacetylation, enzymatic degradation and lectin-gold binding.

We investigated the lectin cytochemistry of control and sialidase-digested sections of the mouse parotid gland by postembedding techniques. PNA and DBA lectins were used and their affinity sites were localized by employing conjugates with horseradish peroxidase that then reacted with anti-horseradish peroxidase antibody and protein A-gold. Potassium hydroxide pretreatment also was used before sialidase/PNA and DBA binding to investigate sialic acid acetylation. Ultrathin sections were obtained from specimens embedded in the acrylic hydrophilic resin, Bioacryl. The acini of mouse parotid gland contained polymorphous secretory granules differentially stained by the two lectins; the use of sialidase digestion and KOH deacetylation revealed that the sialic acids linked to beta-galactose are restricted to the electron-dense concentric areas of target granules, whereas the sialic acids linked to alpha-N-acetylgalactosamine contain C4-acetylated groups and are preferentially located in the electron-lucent regions of bizonal granules.

Recovery of Yersinia enterocolitica from Surfaces of Inoculated Hearts and Livers

Approximately 100 cells of Yersinia enterocolitica were inoculated onto surfaces of beef hearts and livers among 1.6 – 6.6 × 104 indigenous bacteria. Two strains known to be sensitive to selenite were tested for recovery in a selenite broth: T AMU 54, which was isolated in an enteritis outbreak, was recovered in 16 of 20 trials, while a clinical strain, IP 107, was recovered in 9 of 20 trials. Variables tested in the enrichment procedure included selenite levels, beef extract levels and incubation periods. Selective agents encouraging recovery of the organism included both MacConkey agar with Tween 80 and refrigerated Bismuth Sulfite agar plates, with and without a potassium hydroxide pretreatment of the enrichment broth before streaking onto selective agars. Use of refrigerated Bismuth Sulfite agar and a 3-day incubation period of the enrichment broth provided the most consistent recovery of Y. enterocolitica.

The extraction and definition of non-exchangeable or fixed ammonium in some soils from southern New South Wales

The amounts of non-exchangeable or fixed NH4+ in six soils from southern New South Wales were determined by using three methods. Using a potassium hydroxide pretreatment 2-13 % of the total nitrogen in the surface soils was fixed and between 16 and 33 % in the subsoils. Different methods showed up to a threefold difference in the amount on some soils and non-significant differences in others. The interpretation of the part played by this fraction of soil nitrogen in the chemical and biological equilibrium of soil must be qualified according to the extraction method used. The use of soil samples having a larger particle size (&lt; 2 mm) than previously used (&lt;0.147 mm) was found to be adequate with the soils studied. As the present definition of non-exchangeable or fixed NH4+ is misleading, it is proposed that this fraction of soil nitrogen be called intercalary ammonium (NH4+). Intercalary NH4+ is defined as that nitrogen recovered from within clay minerals by hydrofluoric-hydrochloric acid treatment, subsequent to a potassium hydroxide or potassium hypobromite/potassium hydroxide pretreatment and 0 . 5N potassium chloride leaching to remove exchangeable NH4+ and organic nitrogen from the outside of the clay particles.