H2SO4 Pretreatment Research Articles

Preparation of V2O5 using Pb5(VO4)3OH recovered from Bayer vanadium sludge through H2SO4 pre-treatment, H2O2 leaching, V5O12∙6H2O and V10O24∙12H2O precipitation and oxidative roasting at 400 °C

Bayer vanadium sludge (BVS), discharged during the Bayer alumina production, is a promising secondary resource for the supply of vanadium. Previous vanadium extraction process involving Pb5(VO4)3OH precipitation by PbSO4, H2SO4 and (NH4)2SO3 leaching, (NH4)2S2O8 oxidation followed by ammonium vanadate precipitation, suffered from large amounts of reagent consumption and discharge of ammonia-containing waste. In this study, a cleaner and cost-efficient process based on H2SO4 pre-treatment, H2O2 leaching, hydrolytic precipitation, and preparation of V2O5 through oxidative roasting was proposed to reduce reagent consumption and waste. Results show that the maximum vanadium leaching efficiency reached 99.7 % under the most suitable conditions of H2SO4 pre-treatment with H2SO4/Pb5(VO4)3OH molar ratio of 6.5, pulp density of 250 g/L at 90 °C for 4 h followed by H2O2 leaching with H2O2/V molar ratio of 3.0 at 15 °C for 10 min. Furthermore, 96.5 % of vanadium was precipitated in the forms of V5O12∙6H2O and V10O24∙12H2O by heating the leach liquors to 100 °C for 60 min, followed by the oxidative roasting at 400 °C for 2 h to prepare V2O5 product with a purity of 99.2 %, with only H2O as a by-product. This research provides new insights into vanadium extraction in a cleaner, cost-efficient, and sustainable industrial process which saves 147.4 $/t Pb5(VO4)3OH.

Rapid and Convenient Potentiometric Method for Determining Fluorosulfate, a Byproduct of the Fumigant and Greenhouse Gas Sulfuryl Fluoride.

A fluorosulfate ion (FSO3-) is a hydrolysis product of sulfuryl fluoride (SO2F2), which is widely used to fumigate buildings, soil, construction materials, and postharvest commodities, and is a potent greenhouse gas. It is a potential marker for biological exposure to SO2F2 and for monitoring the progress of reactions used to scrub SO2F2 from fumigation vent gases. Here, we report a simple and inexpensive potentiometric method for determining FSO3- using a commercial nitrate-selective electrode and discuss its application. The method is suitable for solutions between 0.0025 mM and 660 mM FSO3- at initial pH between 5 and 9. Halide interference depends on its molar ratio to FSO3- and follows the sequence, F- < Cl- < Br- ≪ I-. Halide interference can be eliminated by adding silver sulfate. Interference by bicarbonate can be eliminated by H2SO4 pretreatment, and interference by phosphate or pyrophosphate by MgSO4 addition. Sulfate does not interfere, as it does in ion chromatography. Satisfactory method detection limits for FSO3- in spiked aqueous extracts of 11 fruits were obtained. The method accurately quantified the yield of FSO3- relative to that of F- in base hydrolysis of SO2F2. This study demonstrates that the developed method is highly selective, convenient, and sensitive and thus can be of great value in practice.

Biomass-based porous carbon from trachycarpus fortunei silk with the hierarchical oxygen-enriched structure for high performance flexible all-solid-state supercapacitor

Hierarchical porous carbons with diverse pore scales are commonly chosen as electrode materials for high-performance supercapacitors due to their excellent electrochemical properties. Herein, a novel synthetic method, dilute H2SO4 pretreatment coupling with subsequent KOH activation, is adopted to prepare hierarchical oxygen-enriched porous carbon using trachycarpus fortunei silk (TFSPC) waste as the raw material. The optimized TFSPC2 possesses a 2049 m2 g−1 specific surface area, 1.58 cm3 g−1 total pore volume, and 22.54 at% oxygen-containing doping. Benefiting from such characteristics, the TFSPC2 electrode exhibits an excellent specific capacitance of 469 F g−1 at 0.5 A g−1 and remarkable cycling stability of only 4.94% capacitance decay even after 20000 uninterrupted cycles in a 6 M KOH electrolyte. Furthermore, the assembled flexible symmetric supercapacitor device TFSPC2//TFSPC2 achieves a high energy density of 14.60 Wh kg−1 in a potential range of 0–1.3 V when the power density is 320 W kg−1. More importantly, the TFSPC2//TFSPC2 device demonstrates superior mechanical flexibility and maintains 88.70% capacity retention even through 2000 cycles (90°) of reduplicative bending/recovering. The research provides a low-cost, green, and renewable strategy for the synthesis of hierarchical porous carbons for supercapacitors.

Impact of probe sonication and sulfuric acid pretreatment on graphene exfoliation in water

Graphene is a 2D material with promising commercial applications due to its physicochemical properties. Producing high-quality graphene economically and at large scales is currently of great interest and demand. Here, the potential of producing high-quality graphene at a large scale via water-phase exfoliation methods is investigated. By altering exfoliation parameters, the production yield of graphene and flake size are evaluated. Pretreatment of the precursor graphite powder using acidic solutions of H2SO4 at different concentrations is found to increase further the yield and structural quality of the exfoliated graphene flakes. These findings are confirmed through various spectroscopy and surface characterization techniques. Controlling flake size, thickness, and yield are demonstrated via optimization of the sonication process, centrifuge time, and H2SO4 pretreatment.

Crystal violet adsorption onto modified biosorbent prepared from agricultural waste: kinetics, isotherm and thermodynamic studies

The present study investigated crystal violet removal by modifying the chestnut shell with a chemical activation method. For this purpose, H2SO4 and NaOH pretreatments were applied to the chestnut shell and the pretreatment method that gave the best performance under the same conditions was determined. The best adsorption efficiency was achieved with the NaOH pretreatment (99.06%) and the crystal violet adsorption reached equilibrium within 60 min. After selecting the best chemical activation method, the modified chestnut shell was characterized before and after adsorption (FTIR and SEM). Furthermore, the effects of parameters such as pH, initial crystal violet concentration, adsorbent dosage, temperature, and contact time were observed. Moreover, isotherm, kinetics and thermodynamics of the adsorption process were researched in detail. The best results were obtained with the Langmuir isotherm model (R2=0.99) and the pseudo-second-order kinetic model (R2=0.99). Thermodynamic parameters showed that the adsorption process is spontaneous, endothermic and feasible.

Macro-micro structure engineering of bio-spore-derived hard carbon as an efficient anode in sodium ion batteries

Elucidating the macro–micro structures of hard carbon is critical to address the issues of deficient Na+ storage capacity at the anode in Na+ ion batteries. Herein, hard carbon materials with various macro–micro structures were synthesized by pyrolyzing the spores of Calvatia Gigantea (SCG) as precursors treated by a coupling strategy with a dehydration process via concentrated H2SO4 treatment and the removal of inherent Si species by NaOH. Research results demonstrate that the process of concentrated H2SO4 pretreatment can induce the collapse of original hollow spheres of SCG to form specific hard carbon hollow hemispheres, while the NaOH leaching treatment can further modulate the microstructures of hard carbon. Attributed to the unique characteristics of specific hollow hemi-spherical morphology, ultra-low surface area, rich closed pore and appropriate layer spacing, the hard carbon not only exhibits outstanding specific capacity up to 500 mA h g−1 with a high initial Coulombic efficiency of 90.23 % for Na+ storage, but also presents excellent high-rate capability with 254.88 mA h g−1 at 5 A/g and cycling stability with a capacity retention rate of ≥80 % after 4102 cycles. The outstanding performance exceeds the vast majority of reported hard carbons for Na+ storage. Theoretical analysis further reveals that increasing closed pores constructed by distorted graphite-like layers together with proper lattice distance and curvature in hard carbon is essential to improve Na+ storage capacity. The coupling strategy of tuning the morphologies and microstructures of spore-derived hard carbon in the work provides new insights for developing advanced hard carbon with efficient Na+ storage performance.

Effect of sulfuric acid pretreatment on flotation performance of calcite and fluorite

Difficulty in separating calcite and fluorite owing to their similar surface properties is the focus of research in the field of mineral processing. To increase the selectivity difference between these two minerals, sulfuric acid was introduced as a surface pretreatmentand, and aluminium sulfate was used as the flotation depressant. The effects of H2SO4 pretreatment on calcite and fluorite flotation performance and the mechanisms thereof were studied by combining microflotation experiments, solution chemical calculations, scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy, and density functional theory (DFT). Microflotation experiments showed that sulfuric acid pretreatment significantly reduced the flotation recovery of calcite to less than 10%, while it had little effect on fluorite, where the recovery reached greater than 80%. SEM-EDS and FT-IR analyses showed that, after sulfuric acid treatment, the surface composition of calcite was converted from CaCO3 to CaSO4, while the fluorite surface remained almost unchanged. DFT calculations showed that CaSO4 was more hydrophilic than CaCO3; therefore, it was more likely to interact with water molecules. The presence of water molecules affected the adsorption of the sodium oleate (NaOL) collector on the mineral surface. Therefore, the calcite surface adsorption ability of NaOL after sulfuric acid pretreatment was weakened, resulting in a significant decrease in flotation recovery.

Hydrolysate production from sugarcane bagasse using steam explosion and sequential steam explosion-dilute acid pretreatment for polyhydroxyalkanoate fermentation

Polyhydroxyalkanoates (PHAs) are potential alternatives to conventional petroleum-based plastics. One of the barriers to the commercialization of PHAs is its high production cost, which is primarily due to substrate. Agricultural lignocellulosic residues, such as sugarcane bagasse, can be used as substrates to lower production costs. In order to effectively convert the substrate to PHA, sugarcane bagasse must be pretreated. In this study, steam explosion and sequential steam explosion–dilute H2SO4 pretreatment of sugarcane bagasse were optimized to effectively release reducing sugars through enzymatic hydrolysis. Experiments using response surface methodology (RSM) revealed that steam temperature had the greatest influence on lowering sugar content for both sequential and steam explosion pretreatments. The optimum steam explosion conditions were 230 °C steam temperature and 701 s holding time. The concentration of reducing sugars in the enzymatic hydrolysate produced by the hydrolysis of steam-exploded sugarcane bagasse was 6.91 g/L (46.07% yield). On the other hand, the optimum conditions for sequential pretreatment were 230 °C steam explosion temperature, 137 °C dilute acid temperature, 42 min of dilute acid reaction time, and 4.75% w/v H2SO4 concentration, resulting in a hydrolysate with a reducing sugar content of 12.89 g/L (85.93% yield). When steam explosion and diluted H2SO4 pretreatment were combined, a yield increase of reducing sugar of 87% was observed. PHA in the form of polyhydroxybutyrate (PHB) was successfully synthesized using the hydrolysate through bacterial fermentation, with a concentration of 1.99 g/L (16.79% yield) after 24 h. As a result, sequential pretreatment was effective in producing enzymatic hydrolysates from sugarcane bagasse that could be utilized to produce PHA.

Recovering biogas and nutrients via novel anaerobic co-digestion of pre-treated water hyacinth for the enhanced biogas production

The present investigation explores the feasibility of generating biogas from water hyacinth (WH) through a pretreatment process. The WH samples were subjected to a high concentration of H2SO4 pretreatment to enhance biogas production. The H2SO4 pretreatment aids in breaking down the lignocellulosic materials found in the WH. Additionally, it helps modify the cellulose, hemicellulose, and lignin, which assists in the anaerobic digestion process. The samples underwent pretreatment with 5% v/v H2SO4 for 60 min. Biogas production was conducted for both untreated and pretreated samples. Furthermore, sewage sludge and cow dung were used as inoculants to promote fermentation in the absence of oxygen. The results of this study demonstrate that the pretreatment of water hyacinth with 5% v/v H2SO4 for 60 min considerably enhances biogas production through the anaerobic co-digestion process. The maximum biogas production was recorded by T. Control-1, with a production rate of 155 mL on the 15th day compared to all other controls. All the pretreated samples showed the highest biogas production on the 15th day, which is comparatively five days earlier than the untreated samples. In terms of CH4 production, the maximum yield was observed between the 25th and 27th days. These findings suggest that water hyacinth is a viable source of biogas production, and the pretreatment method significantly improves biogas yield. This study presents a practical and innovative approach to biogas production from water hyacinth and highlights the potential for further research in this area.

Incidence of Electric Field and Sulfuric Acid Concentration in Electrokinetic Remediation of Cobalt, Copper, and Nickel in Fresh Copper Mine Tailings

In the present study, the assessment of heavy metal contaminant migration from fresh mine tailings was conducted using the electrokinetic remediation technique (EKR). In this sense, a pilot EKR cell was designed to evaluate the recovery potential of copper, nickel, and cobalt species. In particular, the focus was on the impacts of electric field intensity and pH in initial mixture and testing their interaction in copper, nickel, and cobalt migration. Experiments were made using a 22 factorial experimental design with a central point, using DC electric fields from 1.0 to 2.0 V cm−1 and H2SO4 pretreatment solutions from 1.0 to 2.0 mol L−1, along with an ANOVA test with error reduction. The metal removal rates were approximately 7% for cobalt, neglectable for copper, and 6% for nickel. In the best cases, the highest concentrations by migration at the cathodic zone were 11%, 31%, and 30%, respectively. According to ANOVA tests, factor interaction was proven for each metal in the half cell near the cathode and the closest zone from the cathode specifically. Both factors affected metal concentrations, which indicates that when the goal aims for species accumulation in a narrower section, each factor has a significant effect, and their interaction makes a proven enhancement. Thus, using 2.0 V cm−1 and 2.0 mol L−1 showed a high improvement in metal concentration in the cathodic zone.

Elucidating thermochemical pretreatment effectiveness of different particle-size switchgrass for cellulosic ethanol production

Effects of switchgrass particle sizes (<0.25 mm, 0.5–1.0 mm, and 2.0–4.0 mm) on the effectiveness of H2SO4 and NaOH pretreatments were investigated. As particle size increased, glucan, xylan, and lignin contents in raw switchgrass augmented from 30.32% to 32.02%, 18.44% to 19.03%, and 14.78% to 15.33%, respectively. Glucan and xylan (58.54–60.94% and 18.55–20.01%) contents in NaOH pretreated switchgrass and their recoveries (91.95–94.69% and 47.91–52.31%) increased. The highest glucan content (55.76%) and recovery (79.72%) in H2SO4 pretreated switchgrass were reached by middle particle size. The lowest (59.39% for H2SO4 and 58.99% for NaOH) and highest (65.23% for H2SO4 and 66.15% for NaOH) CrI values were obtained from middle and small particle sizes, respectively. SEM images and FTIR spectra showed no visible variations in microstructures and chemical bonds among different particle sizes under the same pretreatment conditions. On the basis of pretreated switchgrass, the highest ethanol concentration and efficiency were reached by big particle size for H2SO4 pretreated (7.03 g/L and 49.28%) switchgrass, while they were achieved by small particle size for NaOH pretreated (11.68 g/L and 72.37%) switchgrass. The highest ethanol yield based on raw switchgrass was attained by big particle size for untreated (29.54%), middle particle size for H2SO4 pretreated (30.60%), and small particle size for NaOH pretreated (62.36%) switchgrass. These findings indicate that the optimal ethanol conversion performance is the result of the interaction between the pretreatment method and biomass particle size.

Pretreatment of refractory gold concentrate calcine using ammonium bifluoride and sulfuric acid solution

The secondary encapsulation of gold and silver by silicates and Fe-oxide during the roasting oxidation of refractory gold concentrate significantly influence the gold and silver leaching efficiency. In this study, a pretreatment method of refractory gold concentrate calcine using ammonium bifluoride and sulfuric acid solution is proposed. The effects of the NH4HF2 and H2SO4 concentration, pretreatment temperature, and time on the leaching efficiency of gold and silver were investigated in detail. The optimum conditions were determined to be NH4HF2 concentration of 1.5 mol/L, H2SO4 concentration of 2 mol/L, pretreatment temperature of 40°C, and duration of 90 min. The leaching efficiency of gold and silver reached 97.6 % and 94.8 %, respectively. The pretreatment process of refractory gold concentrate calcine can be expressed with Johnson-Mehl-Avrami (JMA) equation and depends on the diffusion. The pretreated residue was mainly composed of silicates and Fe-oxide minerals. The gold and silver can be exposed to the ore surface by NH4HF2 pretreatment, which helps to improve its cyanide leaching efficiency.

Impact of different pretreatments on the anaerobic digestion performance of cucumber vine

Copious amounts of cucumber vine (CV) derived from crop growing and harvesting are casually discarded in the field, posing severely negative impacts on public health and the ecological environment. Treating CV via anaerobic digestion (AD) could represent a promising approach while the recalcitrant lignocellulosic structure restricts its conversion efficiency, thus underscoring the importance of valid pretreatments. This study systematically investigated the effects of nine types of commonly applied chemical pretreatments involved H2SO4, HCl, H3PO4, NaOH, KOH, Ca(OH)2, CaO, H2O2, and alkaline hydrogen peroxide (AHP) pretreatments on methane production of CV. Results showed that alkaline and AHP pretreatments were beneficial to the methane production of CV and obtained the considerable cumulative methane yield and biodegradability of 194.3-241.5mL·gVS-1 and 47.59-59.15%, respectively, 36.83-70.07% higher than untreated. Analyses of lignocellulosic compositions and structural characterizations revealed that alkaline and AHP pretreatments well destroyed both hemicellulose and lignin, which commendably increased the accessibility of cellulose, facilitating the methane production. The findings of this study provide not only efficient pretreatment methods for the disposal and utilization of CV during AD process but also promising alternatives for enhancing methane production performance of similar vine residues, which would be greatly valuable for industrial applications in the future.

Bioethanol production from biodegradable wastes using native yeast isolates from Ethiopian traditional alcoholic beverages

Due to the existing energy crisis and scarcity of conventional supplies of fossil fuels, there is a strong desire for the production of bioethanol from sustainable biodegradable waste as an alternative energy source. The aim of this study was to produce bioethanol from grain waste flour (GWF), Tella spent (TS), pineapple (PAP) and papaya peels (PYP) using native yeasts isolated from Ethiopian traditional alcoholic beverages. Diluted H2SO4 was used to hydrolyze polysaccharides in the waste materials. Starch content from GWF and reducing sugar concentration from each hydrolysate were determined by the standard protocol. Seventy-five native yeasts were isolated from local beverages for ethanol production. The 2% H2SO4 pretreatment produced the highest reducing sugar of GWF (30.1%); PYP (28.6%); PAP (16.4%); and TS (10.4%). In addition to this, GWF had 60.6% starch content. Of 75 isolates, 12 were able to tolerate ≥8% ethanol concentration, and 2 isolates, Y10 and Y55 showed strong ethanol production capacity (glucose to ethanol conversion efficiency) with 8.2% (79.8%) and 9.6% (94.3%) from synthetic medium, respectively. The highest ethanol yields of 16.1%, 9.8%, 8.0% and 6.1% were produced from GWF, PAP, PYP and TS, respectively using isolate, Y55 (identified as S. cerevisiae) within 168 h for GWF, 120 h for PAP and 72 h for PYP and TS. This study revealed that native yeast isolates could be used for industrial production of bioethanol via cheap biodegradable wastes.

Evaluation of lignocellulose degradation and ethanol production via dilute acid and alkali pretreatment of hybrid Pennisetum

Chemically pretreating lignocellulose has been widely used in the production of clean energy. An energy grass called hybrid Pennisetum was pretreated with different H2SO4 and NaOH concentrations to analyse the effects of an acid and alkali pretreatment on the degradation of hybrid Pennisetum lignocellulose. The chemical composition, hydrolyzed sugar yield, and microstructure were determined. The results showed that a NaOH pretreatment retained more cellulose and removed more lignins, while a H2SO4 pretreatment significantly inhibited the removal of lignins and increased hemicellulose degradation. X-ray diffraction analysis indicated that increasing the concentration of NaOH or H2SO4 could intensify the cellulose polymerization; this effect was stronger with NaOH compared to H2SO4. Scanning electron microscopy images showed that the cellulose bundles pretreated with H2SO4 were arranged tightly, while the cellulose bundles pretreated with NaOH were loose. Fourier transform infrared spectroscopy exhibited that the ether/ester bond between lignins and carbohydrates was broken by the H2SO4 pretreatment. The NaOH pretreatment increased the number of carbonyl and hydroxyl groups, resulting in more hydrophilic lignins, enabling greater facile degradation. Although the two methods are different in terms of destroying the structure of lignocellulose, the NaOH pretreatment can retain more cellulose, which is beneficial to subsequent ethanol production.

Effect of H2SO4 pretreatment on alkali-resistance performance of FeZrCeTiOx/TNT catalyst for NH3-SCR reaction

CeTiOx catalyst has attracted extensive attention for its superior activity and N2 selectivity for NH3-SCR reaction. However, it still suffers a lot from the deactivation by alkali metals. Thus, it is vital to develop some novel alkali-resistant CeTiOx catalysts for application. In this work, we loaded FeZrCeTiOx component on TiO2 nanotube (TNT) support to obtain FeZrCeTiOx/TNT (FZCT/TNT) catalyst, and then simply pretreated it with H2SO4 to obtain H2SO4-pretreated FeZrCeTiOx/TNT (SFZCT/TNT) catalyst. Besides, the effects of H2SO4 pretreatment on catalytic performance, alkali-resistance as well as physicochemical properties of FZCT/TNT catalyst are comprehensively analyzed. The results manifest that excellent catalytic performance and alkali-resistance (mainly in 350–500 °C) are both achieved by simple H2SO4 pretreatment with only small amounts of active components. This can be mainly attributed to the enhanced acid sites (especially B acid), the prompted adsorption and activation of NH3 species and the inhibited too strong adsorption strength of NOx species.

Sequential mild acid and alkali pretreatment of rice straw to improve enzymatic saccharification for bioethanol production

Sequential pretreatment using different NaOH concentrations (0.5%, 1.0%, 1.5%, w/w) and 1% H2SO4 (w/w) was evaluated as a strategy for effective hydrolysis of rice straw. The efficiency of sequential NaOH and H2SO4 (SNA) pretreatment against sequential H2SO4 and NaOH (SH) was assessed. SH pretreated biomass attained more sugar yield compared to SNA pretreated biomass. The sugar yields from pretreated biomass improved with increasing NaOH concentration in both SH and SNA treatments. The maximum sugar release of 40.6 mg/ml (83.2% efficiency) was obtained from SH pretreated biomass when the stage 2 alkali treatment was performed at 1.5% w/w NaOH. The non-detoxified hydrolysate from this biomass was fermented with 96.8% efficiency.

The enhanced resistance to Na+-poisoning of MnCoCrOx SCR catalyst by acidity regulation: The mechanism of sulfuric acid pretreatment

Low-temperature NH3-selective catalytic reduction (NH3-SCR) catalysts with enhanced resistance to alkali-metal compounds are urgently needed for glass furnace, biomass boilers, etc. flue gases denitrification. A sulfuric acid pretreatment approach, which would be more widely applicable relative to the metal oxides addition method at present, was carefully explored for the excellent MnCoCrOx (MCC) catalyst in this work. The catalytic performance tests show that the decrease in de-NOx efficiency and N2 selectivity caused by Na+ poisoning could be well alleviated via H2SO4 pretreatment. 0.1 M sulfuric acid-treated 1 wt.% Na+ poisoned MnCoCrOx (0.1S-1Na-MCC) catalyst still exhibits a broad T90 (the temperature when de-NOx efficiency reaches 90%) window between 199 and 400 °C. The characterization results demonstrate that H2SO4 pretreatment well restrains the blockage of pore channels and loss of specific surface area caused by Na2O species deposition. A majority of acidity and redox ability of 0.1S-1Na-MCC catalyst were also retained compared with fresh MCC catalyst, which was essential to the SCR process. Sulfuric acid could introduce excessive Brønsted acid sites and cut the loss of Lewis acid sites effectively by the presence of Na2O. Besides, the as-formed HSO4− species would serve as acid sites for NH3 adsorption and activation. The above findings provide new insights with respect to improving the tolerance of metal oxides SCR catalyst to alkali metals by tuning the surface physicochemical properties by acid pretreatment.

Tamarind extract pretreatment: Valorization of sugarcane bagasse for cellulase production by Aspergillus flavus

Effective pretreatment is crucial for cellulase production from sugarcane bagasse. Pretreatment with tamarind extract could reduce the hazardous effect associated with chemical pretreatment. The present work investigated tamarind (Tamarindus indica) extract in combination with H2SO4 and thermal pretreatment of sugarcane bagasse for cellulase production by Aspergillus flavus. The sugarcane bagasse was pretreated with tamarind extract pH 2 and pH 4, followed by 1% H2SO4 and thermal treatment at 121°C for 15 min. The pretreatment slurry was analysed for reducing sugar while solid bagasse was analysed for weight loss. Aspergillus flavus grew on sugarcane bagasse under solid state fermentation and the Carboxy Methyl Cellulase (CMCase) and Filter Paper Assay (FPA) activities were compared on the various pretreatments. The pretreatments changed the visible morphology of the sugarcane bagasse observed by the swelling, fibrous appearance and colour change. Pretreatment slurry yielded highest soluble reducing sugar at 60.01 mg/ml in tamarind extract (pH 4/1% H2SO4 ) and highest weight loss of solids at 73.70% in tamarind extract (pH 2/1% H2SO4 /thermal 121°C). Aspergillus flavus performed better on tamarind extract (pH 2/1% H2SO4 ) by producing optimal CMCase and FPA activities at 0.100 U/ml and 0.409 U/ml respectively after 3 days of fermentation. Cellulase was maximally active at temperature of 50 °C. The tamarind extract pretreatment successfully proved to be an alternative organo-chemical pretreatment of sugarcane bagasse as evidenced by the physical properties, soluble reducing sugars and cellulase activities.&#x0D; Keywords: Aspergillus flavus, Cellulase, Pretreatment, Sugarcane bagasse, Tamarind extract

Combination of ultrasonic and acidic pretreatments for enhancing biohythane production from tofu processing residue via one-stage anaerobic digestion

Tofu processing residues (TPR) have received more attention as a source of bioenergy. However, their low solubility has hindered biohythane generation. Consequently, the ultrasonic and H2SO4 pretreatments were combined and compared for the first time to improve the hydrolysis of organic matter and carbohydrate and increase free amino nitrogen generation from TPR. Besides, the impact of pretreatments on biohythane generation was investigated. Under the optimal conditions of 7.54% substrate level, 8% H2SO4 concentration, 80 °C and 50 min, the coincident ultrasonic-H2SO4 pretreatment enriched the contents of soluble chemical oxygen demand, reducing sugar, and free amino nitrogen to 49675 mg/L, 26 g/L, and 1721 mg/L, respectively, greater than individual pretreatments. Also, Biohythane yield increased by 4.24–13.61% over control (389.42 ± 23.7 ml/g-VSfed). Furthermore, hydrogen yield at 42.5 ± 2.08 and 28.1 ± 1.07 ml/g-VSfed and sulfate removal efficiency at 93 and 92% were significantly improved with ultrasonic-H2SO4 and H2SO4 pretreatments, respectively, indicating acidogenic and sulfidogenic activity enhancement.