Hydrolysis of wheat straw hemicelluloses for maximum xylose extraction

The aim of the study is to select reaction conditions for hydrolysis of wheat straw with dilute sulfuric acid for maximum xylose extraction under mild conditions (at atmospheric pressure and temperature of 100°C). The authors found that maximum glucose yield (72.4-77.1 weight % of the initial content of hemicelluloses in wheat straw) is achieved at a concentration of H2SO4 2-3 weight % and the hydrolysis process duration of 5 hours. Analysis of the obtained hydrolysates showed that they contain cellulose (56.8-70.4 weight %), lignin (19.8-28.8 weight %) and hemicelluloses (2.8-15.3 weight %).

Study on antibacterial papermaking for food packaging using rice straw nanocellulose and nanochitosan

In this study, the antibacterial bleached hardwood kraft pulp-based paper sheets with a base weight of around 125 g/m2 were made with surface sizing by a mixture of oxidated starch and additives from acetic acid-treated nanochitosan and nanocellulose prepared from limited hydrolysis of rice straw by dilute sulfuric acid with added hydrogen peroxide. The characteristics of nanomaterials were analyzed by SEM and XRD. The barrier and antibacterial properties of paper were investigated to assess their ability to contain liquid and food products. Using the sizing mixture which has a solids content of 8% with additives improved the mechanical strength of the paper. The best value of tearing strength of 18.94 mN.m2/g was obtained with adding of 0.5% of nanocellulose and 1.5% of nanochitosan. The burst index of paper reached its highest value of 5.07 kP.m2/g when both nanocellulose and nanochitosan were used at the dosages of 1.0%. The antibacterial features on E. coli clearly showed in papers with 2% of nanochitosan or with the mixture of 1% nanocellulose and 1% nanochitosan addition.

Exploring the Additive Effects of Aluminium and Potassium Sulfates in Enhancing the Charge Cycle of Lead Acid Batteries

The adoption of aluminium sulfate and potassium sulfate as electrolyte additives were investigated to determine the possibility of enhancing the charge cycle of 2V/ 20AH lead acid battery with reference to the conventional dilute sulfuric acid electrolyte. The duration and efficiency of lead acid batteries have been a challenge for industries over time due to weak electrolyte and insufficient charge cycle leading to sulfation. This has affected the long-term production output in manufacturing companies that depend on lead acid batteries as alternative power source. Hence there is need to explore the use of specific sulfate additives that can possibly address this gap. The electrolyte solutions were in three separate charge and discharge cycles involving dilute sulfuric acid electrolyte, dilute sulfuric acid-aluminium sulfate mixed electrolyte and dilute sulfuric acid-potassium sulfate mixed electrolyte for one hour each. The total voltage after 30 minutes charge cycle was 2.3V, 2.35V and 5.10V for dilute sulfuric acid, aluminium sulfate additive and potassium sulfate additive respectively. The cell efficiency for dilute sulfuric acid, aluminium sulfate additive and potassium sulfate additive electrolytes are 77%, 77% and 33% respectively. The electrolyte sulfate additives were of no positive impact to the conventional dilute sulfuric acid electrolyte of a typical lead acid battery due to the low difference in potentials between the terminals.

Potentiality of caro’s acid in leaching of uranium and radioactive measurements from Abu-Rusheid mylonitic gneiss rocks, South Eastern Desert, Egypt

Abu Rusheid area is located at the Southern Eastern Desert of Egypt and composed of Mylonitic gneiss rocks (mineralized rock), Serpentinite rocks, Ophiolitic metagabbro, Ophiolitic mélange, Monzogranites, post- granitic dykes (lamprophyre and dolerite), veins and recent alluvial deposits. This paper is concerned with the study of potentiality of sulphuric and caro’s acid in uranium dissolution from Abu Rusheid mineralized rocks. For this purpose, many batch dissolution experiments were conducted. The obtained results showed that 91.5% and 52% uranium leachability for Caro’s acid and dilute sulfuric acid respectively. The reaction mechanism was described using shrinking core models.

Purification of the Acidic Vanadium-Bearing Solution with a Novel Approach of Chemical Precipitation

Calcified roasting followed by dilute sulfuric acid leaching is a promising process for cleaner vanadium extraction from converter vanadium slag. However, some impurities, like Ca, Mg, Mn, Si and Al, also transfer into the leaching solution, accompanying V during the dilute sulfuric acid leaching, leading to the product of vanadium pentoxide prepared from this acidic vanadium-bearing solution, inferior to the product from the traditional process of sodium roasting and water leaching. A chemical precipitation method was firstly proposed to purify this acidic vanadium-bearing solution with a new prepared remover of MnNH4F3, which combines neutralization and fluoride precipitation into one operational step to remove impurities of Ca2+, Mg 2+, Al3+ and Si4+ in an acidic pH range, simultaneously. Effecting factors involved in the purification process were investigated. It was found that removals of Ca, Mg and Al were all over 95% and around 55% of Si was removed as well at stirring speed of 200 rpm, adding coefficient of 1.6, temperature of 50 °C, reaction time of 30 min and pH of 4.50 ± 0.05, while the loss of vanadium was kept lower than 5%, which was attributed to the reason that the purification reactions mainly proceeded on the surface of the remover. Adding flocculant of polyacrylamide was conductive to accelerating sedimentation of the precipitate and reducing the loss of vanadium. Meanwhile, the filter aid of diatomaceous could improve the filtration performance of the slurry. Ammonium persulfate could effectively oxidize and separate Mn2+ in the form of MnO2 from the vanadium-bearing solution which had been treated by MnNH4F3, but performed less selectivity over Mn2+, and the loss of vanadium was unacceptable. The product of vanadium pentoxide prepared from the purified vanadium-containing solution satisfied the requirements for the standard of grade 98.

THF co-solvent pretreatment prevents lignin redeposition from interfering with enzymes yielding prolonged cellulase activity

Background Conventional aqueous dilute sulfuric acid (DSA) pretreatment of lignocellulosic biomass facilitates hemicellulose solubilization and can improve subsequent enzymatic digestibility of cellulose to fermentable glucose. However, much of the lignin after DSA pretreatment either remains intact within the cell wall or readily redeposits back onto the biomass surface. This redeposited lignin has been shown to reduce enzyme activity and contribute to rapid enzyme deactivation, thus, necessitating significantly higher enzyme loadings than deemed economical for biofuel production from biomass. Results In this study, we demonstrate how detrimental lignin redeposition on biomass surface after pretreatment can be prevented by employing Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment that uses THF–water co-solvents with dilute sulfuric acid to solubilize lignin and overcome limitations of DSA pretreatment. We first find that enzymatic hydrolysis of CELF-pretreated switchgrass can sustain a high enzyme activity over incubation periods as long as 5 weeks with enzyme doses as low as 2 mg protein/g glucan to achieve 90% yield to glucose. A modified Ninhydrin-based protein assay revealed that the free-enzyme concentration in the hydrolysate liquor, related to enzyme activity, remained unchanged over long hydrolysis times. DSA-pretreated switchgrass, by contrast, had a 40% drop in free enzymes in solution during incubation, providing evidence of enzyme deactivation. Furthermore, measurements of enzyme adsorption per gram of lignin suggested that CELF prevented lignin redeposition onto the biomass surface, and the little lignin left in the solids was mostly integral to the original lignin–carbohydrate complex (LCC). Scanning electron micrographs and NMR characterization of lignin supported this observation. Conclusions Enzymatic hydrolysis of solids from CELF pretreatment of switchgrass at low enzyme loadings was sustained for considerably longer times and reached higher conversions than for DSA solids. Analysis of solids following pretreatment and enzymatic hydrolysis showed that prolonged cellulase activity could be attributed to the limited lignin redeposition on the biomass surface making more enzymes available for hydrolysis of more accessible glucan.