Hybrid Pretreatment Research Articles

Thermal chemical pretreatment of waste-activated sludge for enhanced solubilization and biogas production: a review

ABSTRACT Waste-activated sludge (WAS) generation is increasing due to the increased generation of wastewater owing to industrialization and urbanization. The disposal of WAS is a significant environmental and financial concern that can be offset by stabilization and valorization via anaerobic digestion (AD). However, the biodegradation is limited due to microbial cells and extracellular polymeric substances (EPS). Physical, chemical, biological, and hybrid pretreatments and the addition of accelerant materials for enhancing direct interspecies electron transfer (DIET) are among the strategies to overcome the poor biodegradation of WAS. Alkaline pretreatment disintegrates the floc structure of WAS by increasing the osmotic pressure, while microwave irradiation has thermal and a-thermal effects and increases the availability of organics for biodegradation. Moreover, the combination of alkaline and thermal pretreatments has synergic effects on solubilization, biogas production, and dewaterability. The disintegration of WAS is recognized by alteration in volatile solid (VS) content, sCOD, BOD/sCOD, turbidity, nutrients solubilization, dewaterability, particle size, specific surface area, change functional group, alteration in microorganism community, microorganism abundance, color, moisture content, lag phase, and biogas production. Higher doses of pretreatment increase COD solubilization but not biodegradable COD. Maximum COD solubilization ranged from 2 to 37% in alkaline, 21 to 260% in the microwave (MW), and 28 to 624% in hybrid pretreatments.

Innovating Ferro-sonication approach for extracting microplastics from wastewater

For accurate and reliable analysis of microplastics (MPs) in wastewater (WW), it is imperative to comprehend the significance of pre-treating WW before analysis. The suspended solids (SS) in the matrix tend to adhere to the MPs during filtration, which interferes with the detection of the MPs. In this regard, the present study aims to develop and optimize a pretreatment method to improve the extraction efficiency of MPs from WW by reducing the SS. A combination of the Fenton reaction and ultrasonication, ferro-sonication (Fe-UlS), was proposed to digest and eliminate the SS from WW. This hybrid pretreatment, Fe-UlS, was optimized for ultrasonication amplitude, treatment time, and hydrogen peroxide dose using response surface methodology (RSM) with a Box-Behnken design, achieving a desirability of 0.984. The optimum conditions for the Fe-UlS, such as the (1:1) Fenton reagent ratio (0.05 M FeSO4: 30 % H2O2), ultrasonication amplitude (31 %), and total process time (30 min) were found to be statistically significant (p < 0.05). The developed method was then employed for the extraction of spiked polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) MPs in real WW and found efficient in removing 83 % of the TSS present in the primary influent were in 30 min at a temperature of 45 °C. Also, the method did not affect the physio-chemical characteristics of the MPs; however, the thermal analysis of PE and PP MPs showed a statistically significant decrease in the melting temperature, as proven by paired t-test analysis. Further, a non-targeted liquid chromatography-mass spectrometry (LC-MS) analysis proved that Fe-UlS is a stable process, as it did not cause any leaching of MPs under the optimum pretreatment conditions. Finally, Laser Direct-Infrared Imaging (LD-IR) analysis was conducted to validate the developed Fe-UlS pretreatment approach for MP analysis in real WW. About 3434 MPs were detected in 100 mL of WW primary influent, within the size range of 9 to 500 μm. This hybrid pretreatment approach not only streamlines WW sample processing but also reduces the required concentration of Fenton reagent and processing time, yielding accurate and reliable results for monitoring MPs in WW.

Synergic effect of thermo-chemical pretreatment of waste-activated sludge on bio-methane enhancement

Sustainable and environmentally friendly energy production is feasible via anaerobic digestion (AD) of organic wastes, such as waste-activated sludge (WAS). However, due to its limited degradation, a pretreatment strategy is applied to WAS to enhance its bio-degradation and, thus, biogas yield. Alkaline (0.5%–9% g NaOH/gTS, 30 min), microwave (MW) (90°C–175°C), and hybrid (0.5% g NaOH/gTS +125°C) pretreatments were applied to WAS. The characterization of untreated and pretreated WAS revealed that with higher alkaline and MW pretreatment, the soluble chemical oxygen demand (sCOD), carbohydrate, and protein increased; however, the readily biodegradable COD (rbCOD) rate was unlike the sCOD. The sCOD was 7%–18%, 8%–23%, and 37% for alkaline, MW, and hybrid pretreatments, respectively. Stronger alkaline and MW pretreatment induced higher turbidity, capillary suction time, and lower average particle size. AD of alkaline-, MW-, and hybrid-pretreated WAS produced 94% (0.5% NaOH), 125% (MW at 125°C), and 199% (0.5% NaOH and MW at 125°C) increased biogas, respectively, compared to the AD of untreated sludge. The AD data on the alkaline-, MW-, and hybrid-pretreated BMP assays fitted well with the modified Gompertz model with a coefficient of determination above 0.95. The PCA analysis showed that biogas production is closely correlated with pretreatment temperature, VFA production, rbCOD, sCOD, and soluble carbohydrates and protein. Microbial genome sequencing analysis showed an improvement in microbial abundance and diversity. Acetoclastic methanogen (Methanothrix) growth was improved by 37% (MW pretreatment). Abundances of Methanosarcina, using all three metabolic pathways for methanogenesis, were 17, 21, 11, and 48% in the control, alkaline-, MW-, and hybrid-pretreated digestate, respectively, corresponding to 186% improvement in hybrid pretreatment when compared to the control.

Biogas enhancement in the anaerobic digestion of thermo-chemically pretreated sludge by stimulating direct interspecies electron transfer by biochar and graphene

It is necessary to pretreat waste-activated sludge (WAS) to disintegrate the sludge matrix and amend its anaerobic digestion (AD) with carbon-based materials (CMs) to accelerate direct interspecies electron transfer (DIET) in order to realize the maximum biogas potential of abundant and habitat-threatening organic WAS. The AD of WAS pretreated thermo-chemically at 0.5% NaOH (g/g dry sludge) and 125 °C microwave irradiation was amended by biochar doses of 0–40 g/L and graphene doses of 50–1,000 mg/L in the batch operation mode. Hybrid pretreatment of WAS deteriorated dewaterability but solubilized 38% of total chemical oxygen demand (COD). AD amended with 20 g/L biochar and 100 mg/L graphene had the optimum accumulative methane yield of 183.6 and 153.8 mL/gVS, respectively, which correspond to 42.8% and 24.8% increases compared to an unamended control assay with maximum methane content of 70.3% and 71.9%, respectively. The digestate of biochar- and graphene-amended assays resulted in higher TS% and alkalinity, reduced sCOD, VFA, and turbidity, and increased particle size distribution compared to control. Biochar-amended digestate had improved dewaterability, while digestate of graphene-amended assays resulted in worse dewaterability than control. The t-test showed a significant difference between the biochar and graphene amended batch assays, while principal component analysis (PCA) indicated that biogas yield was closely correlated with pH. CM-amended batch assays demonstrated superb fitting with modified Gompertz, logistic, and first-order models with a coefficient of determination above 0.97. Microbial community abundance and diversity were affected by CMs amendment, resulting in increased acetoclastic methanogen growth and transformed methanogenic metabolic pathways. An extended pilot-scale study and techno-economic and life cycle assessments are required to investigate environmental impacts and feasibility.

Investigation of pre-treatment techniques on spent substrate of Pleurotus ostreatus for enhanced biobutanol production using Clostridium acetobutylicum MTCC 11274

Addressing global energy demand, researchers sought eco-friendly biobutanol production from lignocellulosic waste biomass. In the present research work, five different pre-treatment methods viz., Microwave, Ultrasound, Alkali, Acid, and Hybrid, were investigated to explore its biobutanol production potential by utilizing Pleurotus ostreatus spent as substrate. The compositional and physico-chemical changes of the pre-treated Spent Mushroom Substrate (SMS) were assessed using SEM, FTIR, and XRD. Hybrid pre-treatment (Microwave, Alkali, Ultrasound) showed higher delignification when compared to conventional pre-treatment method. Hybrid pre-treated SMS resulted in higher total reducing sugars (521.53 ± 1.84 mg/g) than indigenous SMS (267.89 ± 1.53 mg/g). Fermentation of hybrid pre-treated SMS with Clostridium acetobutylicum MTCC 11274 produced the highest biobutanol concentration (9.84 ± 0.03 g/L) and yielded 0.38 ± 0.02 g/g of biobutanol. This study revealed that hybrid pre-treatment could be a promising solution for enhanced biobutanol production using SMS biomass.

Optimization of bio-oil extraction from Chlorella biomass via a green approach to obtain algal-based Di-ethyl phthalate.

This study focuses on determining the optimum external operating parameters of algal cell lysis for extraction of bio-oil from Chlorella biomass. Response surface methodology has been applied to a regression analysis model for optimizing solvent ratios, i.e., ethyl acetate to ethanol (E.A.:E) ratio for maximum extraction of bio-oil and aqueous deep eutectic solvent to biomass (aDES:biomass) ratio for algal pretreatment for the enhanced yield of bio-oil. Optimized process conditions were 15min of homogenization combined with ultrasonication (hybrid method). The aDES:biomass ratio of 8.25 caused the highest cell disruption efficiency to liberate bio-oil from encapsulated cells. The solvent ethyl acetate to ethanol ratio (E.A.:E) was optimum at 0.8 for maximum extraction of bio-oil, and studies indicated a maximum bio-oil yield of 94.0% using this hybrid pretreatment process combined with ultrasonication and homogenization. The GC-MS characterization technique was used to analyze the bio-oil, which showed it consisted of 67.93% Di-ethyl phthalate (DEP) and 32.07% esters compounds (C12-C40 hydrocarbons range). The produced DEP from Chlorella biomass using this sustainable green approach is very promising. The estimated cost was around Rs 49 per gm (equivalent to Rs 664.56 for 13.58 gm), which indicates the potential for a cost-effective method to produce pure DEP from Chlorella biomass.

Clean hydrogen energy production via purification of hydrogen sulfide thermolysis products employing supersonic separator

Catalytic thermolysis of hydrogen sulfide rich acid gases at elevated temperatures is a novel process to produce clean hydrogen fuel. Separation of the hydrogen gas from furnace effluents is rather a difficult task. Several approaches such as membranes, adsorption and absorption processes are traditionally used to achieve this goal. Each of these conventional processes has its own difficulties such as high capital and operation investments, large equipment sizes and elevated corrosion rates. Employment of supersonic separators for the above purpose strongly alleviates the above problems. The present work investigates the use of supersonic separator units both as a final separation device and also as a hybrid pre-treatment method via numerical simulation using MATLAB-Simulink toolbox. It was noticed that a single supersonic separator unit is unable to accomplish the target specification as a final separation device. Hence, consecutive combination of supersonic separator units is used to obtain the desired hydrogen purity. The performance of the entire supersonic separator network strongly depends on the inlet pressure of each individual supersonic separator unit. Detailed optimization of the entire process revealed that for the case study at hand, the optimal inlet pressure for all eleven required supersonic separator units would be around 7 MPa. The number of required 3S units and the overall power of compressors required between the 3S stages are used as the optimization merit functions. Furthermore, in a hybrid approach, a combination of supersonic separator units is used prior to absorption process to reduce the hydrogen sulfide concentration of the hydrogen gas product to less than 4 ppm. Use of four consecutive supersonic separator units along with the absorption process can lead to more than 95% saving both in DEA circulation rate and reboiler duty. The entire above issues have not been addressed previously in the literature.

Impact of sequential hybrid pretreatment in anaerobic digestion of food waste and garden waste co-digestion on waste characteristics and biogas production

Impact of sequential hybrid pretreatment in anaerobic digestion of food waste and garden waste co-digestion on waste characteristics and biogas production

Comprehensive Treatment Strategy for Banana Inflorescence Bract to Synthesize Biodiesel and Bioethanol Through Fungal Biorefinery

Banana inflorescence bract (BIB), an agro-waste is sporadically explored for second-generation biofuel production in spite of having considerable holocellulosic composition (cellulose-35.56%, w/w; hemicellulose-22.41%, w/w). In this study, an attempt has been made to utilize this substrate for fermentable sugars (pentose-C5 and hexose-C6) extraction which were employed for the co-production of microbial lipids and ethanol using Rhodosporidium toruloides NCIM 3547 and Saccharomyces cerevisiae respectively. Since, a considerable amount of lignin (8.78%, w/w) is present in BIB, a hybrid pretreatment and carbohydrate hydrolysis through microwave (160 W) assisted mild H2SO4 acid 2.5% (v/v) was adopted. The resultant liquor contains holocellulosic sugars (C5 and C6 sugars), out of which xylose (10.40 ± 0.49 g/L) and glucose (51.48 ± 1.14 g/L). Hence, it was used as the growth medium for R. toruloides to produce lipids i.e., single cell oil (SCO). The maximum lipid content was found to be 44.89 ± 1.25 (%, w/w) containing total saturated fatty acids of 89.07% which justifies its potential application in biodiesel production. On the other hand, the pretreated solid fraction containing cellulose was saccharified using cellulolytic enzyme produced by Aspergillus sp. with saccharification (%) of 69.99 ± 0.30 (%, v/w) and yield of 27.22 ± 0.33 g/L of reducing sugar. This enzymatic hydrolysate was used for ethanol production by Saccharomyces cerevisiae resulting in an ethanol yield of 12.70 ± 0.09 g/L and productivity of 0.132 g/L/h. Based on this outcome, a sustainable route for agro-waste management of BIB was laid by favouring the integrated production of biodiesel and bioethanol towards a biorefinery approach. Exploration and utilization of an agro-waste, banana inflorescence bract is established as a potent feedstock for the co-production of single cell oil and bioethanol is reported for the first time. Microwave-assisted mild acid pretreatment was performed for effective delignification and hydrolysis of holocellulosic components. The resultant liquid hydrolysate consisting of lignin degradatory compounds, pentose (xylose) and hexose (glucose) sugars was used as a growth medium for producing single cell oil, proving its potential application in biodiesel production. Further, the pretreated solid cellulosic fraction was saccharified using crude cellulolytic enzymes and an enzymatic hydrolysate was used for the production of bioethanol through two different fermentative strategies. This study reveals that banana inflorescence bract could act as suitable biomass towards the biorefinery approach. Its complete utilization paved the way for agro-waste management that is not in existence so far according to the authors’ knowledge

Advancements in Giant Reed (Arundo donax L.) Biomass Pre-Treatments for Biogas Production: A Review

Giant reed is a non-food, tall, rhizomatous, spontaneous perennial grass that is widely diffused in warm-temperate environments under different pedo-climatic conditions. In such environments, it is considered one of the most promising energy crops in terms of economic and environmental sustainability, as it can also be cultivated on marginal lands. Owing to its complex and recalcitrant structure due to the lignin content, the use of giant reed as a feedstock for biogas production is limited. Thus, pre-treatment is necessary to improve the methane yield. The objective of this review was to critically present the possible pre-treatment methods to allow the giant reed to be transformed in biogas. Among the studied pre-treatments (i.e., hydrothermal, chemical, and biological), alkaline pre-treatments demonstrated better effectiveness in improving the methane yield. A further opportunity is represented by hybrid pre-treatments (i.e., chemical and enzymatic) to make giant reed biomass suitable for bio-hydrogen production. So far, the studies have been carried out at a laboratory scale; a future challenge to research is to scale up the pre-treatment process to a pilot scale.

Insights into the recent advances in the pretreatment of biomass for sustainable bioenergy and bio-products synthesis: Challenges and future directions

Recently, biomass has shown its viability as an alternative to fossil fuels. Due to the growing trend in greenhouse gas emissions generated by the continual burning of fossil fuel products, it will be advantageous for humanity to seek a more sustainable and renewable source of energy. Due to its availability, biomass has a promising approach as a feedstock for bioconversion processes that produce energy, fuels, and other chemicals. The carbon dioxide generated by burning biomass has no influence on atmospheric carbon dioxide since it is derived from a renewable source. Despite these benefits, its adoption in bioconversion and biorefinery processes has traditionally been hindered by its recalcitrant nature, as indicated by its intrinsic characteristics. Prior to any conversion process, biomass must be pretreated to enhance product recovery. To satisfy the rising need for renewable and sustainable energy sources, the present conversion efficiency must be improved and the biorefinery concept must transition from using just one biomass component (cellulose) to utilizing the complete biomass component. This study examines numerous pretreatment procedures used prior to any conversion process, the challenges faced, and the future of biomass pretreatment technologies. Physical, hydrothermal, chemical, oxidation, biological, and hybrid pretreatment techniques are evaluated. The review indicates that the ideal approach to biomass pretreatment must be able to deal with the recalcitrant nature of biomass, enhance the crystallinity of cellulose, and provide the greatest recovery of biofuels, bio-char, sugars, and other industrially relevant bioproducts. The data offered in this study will equip readers with the knowledge necessary to effectively identify solutions to pretreatment problems and energy generation from pretreated biomass.

Multi-Criteria Analysis of the Influence of Lignocellulosic Biomass Pretreatment Techniques on Methane Production

Methane from environmentally friendly anaerobic digestion may be an alternative non-renewable source that is depleting. One of the substrates for that process may be lignocellulose-based materials. The article concerns comparing the environmental impact as well as technical and energy indicators of alternative ways of producing methane from the anaerobic digestion of Pennisetum hybrid. Five scenarios were analyzed: methane production from the anaerobic digestion of the raw grass, the grass subjected to alkaline pretreatment (with 2% NaOH solution at two temperatures), and the grass subjected to mechanical pretreatment (ground to obtain particle sizes &lt;0.18 mm and 0.25–0.38 mm). Multi-criteria decision (MCA) analysis was carried out with the use of five indicators, including life cycle assessment results as well as methane production parameters, in order to optimize this sustainable way of bioenergy production. The purpose of this study was to identify the most cost-effective and environmentally friendly method of Pennisetum hybrid pretreatment in order to optimize the methane production process in terms of environmental, technical, and economic aspects. According to the obtained results, it was stated that the most advantageous solution for the majority of the analyzed indicators turned out to be the mechanical pretreatment with grinding the lignocellulosic biomass into a particle size &lt;0.18 mm.

Effect of Laser Micro-Texturing on Laser Joining of Carbon Fiber Reinforced Thermosetting Composites to TC4 Alloy.

Carbon fiber reinforced thermosetting composites (CFRTS) and TC4 alloy are important structural materials for lightweight manufacturing. The hybrid structure of these two materials has been widely used in the aerospace field. However, the CFRTS-TC4 alloy joint formed by the traditional connection method has many challenges, such as poor environmental adaptability and stress concentration. Laser micro-texturing of metal surface-assisted laser connection of CFRTS and TC4 alloy has great potential in improving joint strength. In order to study the effect of laser micro-texturing on the laser bonding of CFRTS and TC4 alloy, the simulation and experimental research of laser welding of TC4 alloy and CFRTS based on laser micro-textures with different scanning spacings were carried out, and the interface hybrid pretreatment method of laser cleaning and laser plastic-covered treatment was introduced to assist the high-quality laser bonding of heterogeneous joints. The results showed that the established finite element model of CFRTS-TC4 alloy laser welding can predict the temperature field distribution of the joint during the welding process and reflect the forming mechanism of the joint. The laser micro-textures with different scanning spacings will lead to a difference in the temperature field distribution on the polyamide (PA6) interface, which leads to a change in heat input on the CFRTS surface. When the laser scanning spacing is 0.3 mm, the joint strength can reach 14.3 MPa. The failure mechanism of the joint mainly includes the cohesive failure of the internal tear of the carbon fiber and the interfacial failure of the interface between the PA6 resin and the TC4 alloy.

The Effect of a Hybrid Pretreatment Device for CEMS on the Simultaneous Removal of PM2.5 and Water Vapor

Stationary emission sources still account for a significant portion of total air pollution emissions. Continuous emission monitoring systems (CEMS) have been used to estimate the emissions of stack pollutants. A large amount of moisture and other interfering factors in the sample discharged from a stack result in the loss of target gases due to artifact formation or gas absorption, thereby reducing measurement accuracy. Therefore, a pretreatment process is essential. Among various pretreatment technologies available, a cyclone with a rapid cooling unit is a special one that can be applied to remove particles and water vapor at the same time in CEMS. This study aimed at the simultaneous removal of water vapor and particles by operating a hybrid pretreatment device at low temperatures such as −5, −15, and −25 °C. When using the hybrid cyclone under the conditions of high temperature (180 °C), humidity (150 g/m3), PM2.5 (1 mg/m3), and SO2 (105.2 ppm) concentrations, the reduction rates of water vapor and PM2.5 concentration and the recovery rates of SO2 concentration were 82.2, 80.2, and 96.4%, respectively. These data suggested that the hybrid cyclone could be used as a pretreatment device for CEMS.

Alkaline Pretreatment Facilitate Mechanical Fibrillation of Unbleached Cellulose Pulps for Obtaining of Cellulose micro/nanofibrils (MFC)

ABSTRACT Energy expenditure is a limiting factor for the production of cellulose micro/nanofibrils in mechanical processing. This study evaluated the effect of novel alkaline pretreatments on unbleached Eucalyptus sp. pulps (hardwood) and Pinus sp. cellulose (softwood) to facilitate the production of cellulose nanofibrils by mechanical fibrillation and reduce the energy consumed by the mill. Pretreatments with NaOH in concentrations of 5% for 2 h and 10% for 1 h and 2 h and a hybrid pretreatment with 5%/16% NaOH/ H2O2 for 2 h were evaluated. The 10% pre-treatment was done at 1 h and 2 h to evaluate the effect of the less aggressive treatment (1 h). The morphology, chemical composition, turbidity of the fibers/suspensions, mechanical properties, fibrillation quality index and energy expended during the fibrillation were evaluated for each pretreatment. The less aggressive pretreatments produced micro/nanofibrils with fewer passes of the pulp through the fibrillator, which effectively facilitated extraction with lower energy consumption. The hybrid pretreatment did not show satisfactory results in reducing energy consumption, and the quality of the nanofibrils produced by this pre-treatment was inferior to the others. This study showed innovation in performing novel and efficient NaOH and hybrid (NaOH/H202) pretreatments on commercial unbleached pulps to obtain pulp micro/nanofibrils.

High-performance polylactic acid compressed strawboard using pre-treated and functionalised wheat straw

An eco-friendly pre-treatment coupled with surface functionalisation were developed to enhance the quality of wheat straw particles to be used for development of high-performance polylactic acid (PLA) compressed strawboard. Eco-friendly hybrid pre-treatment (i.e., hot water followed by steam, H+S) and surface functionalisation processes employing attapulgite nanoclay (AT) and graphene nanoplatelets (G) were used to obtain an appropriate wheat straw surface quality while increasing its compatibility with the PLA matrix. The successful pre-treatment and surface functionalisation of wheat straw particles was verified through characterisation techniques, including SEM, FTIR, XRD, Raman spectroscopy, and TGA. Tensile strength and water absorption properties of compressed strawboards were examined to investigate the influence of pre-treatment and surface functionalisation of wheat straws. The maximum tensile strengths of 28 MPa and 27 MPa were recorded for 10 H+S-AT and 10 H+S-G samples, respectively, which are considerably higher than the value (i.e., 9.7 MPa) registered for the sample without pre-treatment and surface functionalisation (i.e., 10UN). The lowest water absorption after 24 h of immersion was registered for 10UN-G (i.e., 1.6%), which is 11% and 31% lower than the 10UN and 10 H+S samples, respectively. The effect is attributed to an improved interfacial bond between wheat straw and PLA matrix due to the graphene surface functionalisation, as evidenced by the SEM.

Boosting Portland cement-free composite performance via alkali-activation and reinforcement with pre-treated functionalised wheat straw

Utilising wheat straw reinforced OPC-free composites in the construction industry requires efficient, eco-friendly pre-treatment coupled with surface functionalisation methods to turn it into a high-performance material. Herein, alkali-activated material (AAM) was used as an OPC-free matrix, while eco-friendly hybrid pre-treatment and surface functionalisations were applied to mitigate the surface quality deficiencies of wheat straw and improve its compatibility with low-carbon binders. Wheat straw particles were subjected to a mild physical pre-treatment (hot-water followed by steam) and surface functionalisation using attapulgite nanoclay and graphene nanoplatelets to improve their capacity as an effective reinforcing material in AAM. Comprehensive characterisation verified successful pre-treatment and surface functionalisation, which led to the improved interfacial bond between wheat straw and AAM. The best results were obtained for the AAM samples reinforced with pre-treated straw that was functionalised with attapulgite nanoclay (i.e., H+S-AT), in which the volume of permeable voids decreased by 18%, while compressive and flexural strength at 90 d increased by 41% and 27%, respectively, compared to the control sample. However, the effect on the thermal properties of the resulted composites was not significant.

Effects of laser hybrid interfacial pretreatment on enhancing the carbon fiber reinforced thermosetting composites and TC4 alloy heterogeneous joint

To enhance the carbon fiber reinforced thermosetting composites (CFRTS) and the TC4 alloy heterogeneous joint strength, an interfacial hybrid pretreatment of laser cleaning and laser plastic-covered processing was introduced. The laser cleaning applied to remove the epoxy resin on CFRTS surface and the laser plastic-covered processing was applied to produce a thermoplastic layer on the TC4 surface. The surface morphology of CFRTS after laser cleaning, the CFRTS-TC4 heterogeneous joint enhancement and failure mechanism was investigated. The result showed that the epoxy resin on CFRTS surface could be removed effectively with this laser hybrid pretreatment and the contact area between the CFRTS and TC4 alloy can be improved. Mechanical interlocks and chemical bonds were produced at the CFRTS-TC4 interface, which further enhanced the CFRTS-TC4 heterogeneous joint strength. The CFRTS-TC4 joint fracture occurred between the carbon fibers and polyamide-6 (PA6) resin inside the CFRTS, and the fracture mode is tearing of the CFRTS interlayer.

A hybrid pretreatment strategy for delignification of Aloe vera processing waste and its effectiveness towards saccharification

A copious amount of rigid Aloe vera leaf rind (AVLR) has been produced from the aloe gel processing industries are majorly disposed as wastes since it has no commercial value. The cell wall compositional analysis revealed that significant quantity of cellulose (46% ± 0.76, w/w) and hemicellulose (18.5% ± 0.24, w/w) which justifies as potent source for bioethanol production. However, high lignin content (13.95% ± 0.45, w/w) hinders depolymerization of polysaccharides into fermentable sugars and subsequent fermentation for ethanol production. In the present study, microwave-assisted alkali (MAA) pretreatment of AVLR biomass was carried out by varying the power level (160 W, 320 W and 480 W) which showed a maximum delignification (66.38%) at 320 W. Scanning Electron Microscope (SEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) based characterization were performed to study the extent of delignification in AVLR biomass. The Gas Chromatography-Mass Spectrometry (GC-MS) analysis was performed for the liquid hydrolysate obtained after MAA pretreatment at 320 W indicated that the hydrolysate contained more of oxidized phenolic hydrocarbons that can be potentially utilized for other value-added product synthesis. A comparison of saccharification efficiency was performed using two different cellulase producers namely Aspergillus niger and Aspergillus sp. A maximum saccharification of 68.5% ± 0.34 was achieved by Aspergillus sp., that was 2.8% higher on comparing with untreated AVLR biomass. This indicates the feasibility of MAA pretreatment for AVLR biomass in order to improve the accessibility of fermentable sugars available for ethanol production.

Enhanced lipid recovery from chlorella sp. Biomass by green approach: A combination of ultrasonication and homogenization pre-treatment techniques (hybrid method) using aqueous deep eutectic solvents

Microalgae is renewable and sustainable biomass with high lipid content to produce third-generation microalgal biofuels and is considered as one of the best alternative biofuels to replace non-renewable fossil fuels. Cell disruption is an essential pre-treatment, necessary for the efficient extraction of lipids from the biomass before processing in biofuel production, but high-value energy requirement is an important issue for low-valued biofuels. This study investigated the hybrid pre-treatment method of microalgae species: chlorella sp. for enhanced lipid extraction by using a green approach i.e., combination of homogenization and ultrasonication technique along with green solvents. The study found increased lipid yield that suggested rupture of the outer cell wall of chlorella sp. which was sufficient to allow for the diffusion of aqueous deep eutectic solvent (aDES) for lipid extraction. The study on the hybrid methods with aqueous deep eutectic solvents indicated that lipid extraction enhanced from 13.05% in case of untreated biomass to 19.20%, 26.3%, 29.41%, and 30.65% for hybrid method-I, hybrid method-II, hybrid method-III, and hybrid method-IV respectively. GC–MS analysis of the extracted lipids identified the major component as Diethyl phthalate with enhanced yield at 40% and 17% respectively by the hybrid method III and IV in comparison to untreated biomass which is a value-added product having potential applications as a plasticizer and use in pharmaceutical & cosmetic industry.