Effect of thermochemical treatment of sewage sludge on its phosphorus leaching efficiency: Insights into leaching behavior and mechanism.

Thermochemical conversion, including hydrothermal processing, pyrolysis and incineration, has become a promising technology for sewage sludge (SS) treatment and disposal. Furthermore, acid leaching is considered as an effective method to recover phosphorus (P) from SS and its thermochemical treatment products. This study has investigated the potential of P reclamation from SS and its thermochemical derivatives, including hydrochar (HC), biochar (BC), and SS incinerated ash (SA). Comparative analyses of physicochemical properties of these derivatives revealed a decrease in hydroxyl and aromatic groups and an increase in aliphatic and oxygen-containing functional groups in HC and BC. Leaching experiments using 1 M sulfuric acid (H2SO4) and 1 M oxalic acid (C2H2O4) suggested that H2SO4 slightly outperformed C2H2O4 in terms of P leaching efficiency. HC achieved 79.1 % optimal leaching efficiency in 60 min using H2SO4, while BC, SS, and SA required 360 min to achieve comparable efficiency. SS and BC reached optimal leaching efficiency at 74.1 % and 76.2 % in H2SO4, while SA achieved 80.9 % in C2H2O4. Importantly, HC and SA are more favorable for P extraction using acid leaching, whereas BC tends to be a potential P carrier. Time-dependent kinetics revealed a two-stage leaching process, i.e., fast and slow reaction stages. Shrinking core model indicates product layer diffusion as the primary rate-limiting step in both stages. Overall, these fundamental insights play an important role in practical P recovery through acid leaching of SS derived residues after thermochemical treatment.

Extracting bioactive compounds and proteins from Bacopa monnieri using natural deep eutectic solvents.

This study employed novel extraction methods with natural deep eutectic solvents (NADES) to extract bioactive compounds and proteins from Bacopa monnieri leaves. The conditional influence of ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and enzymatic-assisted extraction (EAE) on the recovery efficiency of phenolics, proteins, flavonoids, and terpenoids was evaluated. The conditions of UAE were 50 mL/g LSR, 600W of ultrasonic power, and 30% water content with 40°C for 1 min to obtain the highest bioactive compounds and protein contents. The conditions of MAE were 40 mL/g LSR, 400W of microwave power with 30% water content for 3 min to reach the highest contents of biological compounds. The conditions of EAE were 30 mL/g of LSR, 20 U/g of enzyme concentration with L-Gly-Na molar ratio at 2:4:1, and 40% water content for 60 min to acquire the highest bioactive compound contents. Scanning electron microscopy (SEM) is employed to analyze the surface of Bacopa monnieri leaves before and after extraction. Comparing seven extraction methods was conducted to find the most favorable ones. The result showed that the UMEAE method was the most effective way to exploit the compounds. The study suggested that UMEAE effectively extracts phenolics, flavonoids, terpenoids, and protein from DBMP.

The role of ubiquitous metal ions in degradation of microplastics in hot-compressed water.

Hydrothermal processing (HTP) is an efficient thermochemical technology to achieve sound treatment and resource recovery of sewage sludge (SS) in hot-compressed subcritical water. However, microplastics (MPs) and heavy metals can be problematic impurities for high-quality nutrients recovery from SS. This study initiated hydrothermal degradation of representative MPs (i.e., polyethylene (PE), polyamide (PA), polypropylene (PP)) under varied temperatures (180-300 °C) to understand the effect of four ubiquitous metal ions (i.e., Fe3+, Al3+, Cu2+, Zn2+) on MPs degradation. It was found that weight loss of all MPs in metallic reaction media was almost four times of that in water media, indicating the catalytic role of metal ions in HTP. Especially, PA degradation at 300 °C was promoted by Fe3+ and Al3+ with remarkable weight loss higher than 95% and 92%, respectively, which was ca. 160 °C lower than that in pyrolysis. Nevertheless, PE and PP were more recalcitrant polymers to be degraded under identical condition. Although higher temperature thermal hydrolysis reaction induced severe chain scission of polymers to reinforce degradation of MPs, Fe3+ and Al3+ ions demonstrated the most remarkable catalytic depolymerization of MPs via enhanced free radical dissociation rather than hydrolysis. Pyrolysis gas chromatography-mass spectrometry (Py GC-MS) was further complementarily applied with GC-MS to reveal HTP of MPs to secondary MPs and nanoplastics. This fundamental study highlights the crucial role of ubiquitous metal ions in MPs degradation in hot-compressed water. HTP could be an energy-efficient technology for effective treatment of MPs in SS with abundant Fe3+ and Al3+, which will benefit sustainable recovery of cleaner nutrients in hydrochar and value-added chemicals or monomers from MPs.

Optimizing Ultrasonic-Assisted and Microwave-Assisted Extraction Processes to Recover Phenolics and Flavonoids from Passion Fruit Peels.

This study optimized the ultrasonic-assisted extraction (UAE) and microwave-assisted extraction (MAE) processes to acquire phenolics and flavonoids from passion fruit peels using a mixture of ethanol, acetone, and water. An augmented simplex-centroid design was employed to find the suitable volume ratio among solvent ingredients to attain the highest extraction yield of phenolics and flavonoids. One-factor experiments were conducted to investigate the influence of UAE and MAE parameters on the recovery yield of phenolics and flavonoids before the two processes were optimized using Box-Behnken Design (BBD) models. The optimal UAE conditions for recovering phenolics and flavonoids from passion fruit peel powder (PFP) were 28 mL/g of liquid-to-solid ratio (LSR), 608 W of ultrasonic power, and 63 °C for 20 min to acquire total phenolic content (TPC) and total flavonoid content (TFC) at 39.38 mg of gallic acid equivalents per gram of dried basis (mg GAE/g db) and 25.79 mg of rutin equivalents per gram of dried basis (mg RE/g db), respectively. MAE conditions for attaining phenolics and flavonoids from PFP were 26 mL/g of LSR and 606 W of microwave power for 2 min to recover TPC and TFC at 17.74 mg GAE/g db and 8.11 mg RE/g db, respectively. The second-order kinetic model was employed to determine the UAE and MAE mechanism of TPC and TFC and the thermodynamic parameters of the extraction processes. The antioxidant activities of passion fruit peel extracts at optimal conditions were examined to compare the efficiency of UAE and MAE. This study establishes an effective approach for obtaining phenolics and flavonoids from passion fruit peels.

Ultrasonic-Assisted and Microwave-Assisted Extraction of Phenolics and Terpenoids from Abelmoschus sagittifolius (Kurz) Merr Roots Using Natural Deep Eutectic Solvents.

This research extracted phenolics and terpenoids from Abelmoschus sagittifolius (Kurz) Merr roots using natural deep eutectic solvent-based novel extraction techniques. Twelve natural deep eutectic solvents (NADESs) were produced for recovering phenolics and terpenoids. Citric acid/glucose and lactic acid/glucose, with a molar ratio of 2:1, were determined as the most appropriate NADESs for extracting phenolics and terpenoids, respectively. Afterward, the proper conditions for NADES-based ultrasonic-assisted and microwave-assisted extraction were investigated. Then, the time and liquid-to-solid ratios of ultrasonic- and microwave-combined extraction methods and the sequence of ultrasound and microwave treatments were examined. The conditions of ultrasonic-assisted extraction were 40 mL/g liquid-to-solid ratio, 40% water content, 30°C, 5 min, and 600 W ultrasonic power for the highest terpenoid recovery at 69 ± 2 mg UA/g dw, while 150 W ultrasonic power was suitable for phenolic recovery at 9.56 ± 0.17 mg GAE/g dw. The conditions of microwave-assisted extraction were 50 mL/g liquid-to-solid ratio, 20% water content, 400 W microwave power, and 2 min to acquire the highest phenolics and terpenoids at 22.13 ± 0.75 mg GAE/g dw and 90 ± 1 mg UA/g dw, respectively. Under appropriate conditions, the biological activities, phenolic content, and terpenoid content of obtained extracts from four extraction methods, including ultrasonic-assisted, microwave-assisted, ultrasonic-microwave-assisted, and microwave-ultrasonic-assisted extraction, were compared to select the most proper method. The conditions of ultrasonic-microwave-assisted extraction were 40 mL/g liquid-to-solid ratio, 5 min sonication, and 1 min microwave irradiation to obtain the highest phenolic and terpenoid contents (27.07 ± 0.27 mg GAE/g dw and 111 ± 3 mg UA/g dw, respectively). Ultrasonic-microwave-assisted extraction showed the highest phenolic content, terpenoid content, and biological activities among the four extraction techniques. The changes in the surface morphology were determined using scanning electron microscopy. This study demonstrated that ultrasonic-microwave-assisted extraction was an effective and sustainable method in food and pharmaceutical industries for recovering phenolics and terpenoids from Abelmoschus sagittifolius (Kurz) Merr.

Green extraction of phenolics and flavonoids from black mulberry fruit using natural deep eutectic solvents: optimization and surface morphology.

This study deployed ultrasonic-assisted extraction (UAE), combined with natural deep eutectic solvents (NADES), to extract phenolics and flavonoids from the black mulberry fruit, and the antioxidant activity was examined. The extraction yields of NADES-based UAE were assessed based on the yields of phenolics and flavonoids extracted from the black mulberry fruit. This study selected the molar ratios of hydrogen bond acceptors (HBA) and hydrogen bond donors HBD at 1:2 from previous studies. Choline chloride-lactic acid showed the highest solubility with phenolics and flavonoids among NADES systems. One-factor experiments evaluated the effect of UAE conditions (liquid-to-solid ratio (LSR), water content in NADES, temperature, and time) on TPC, TFC, and antioxidant activity. The suitable NADES-based UAE conditions for extracting phenolics and flavonoids from the black mulberry fruit were 60 ml/g of LSR, 40% water content, 70 °C, and 15 min. Response surface methodology with the Box-Behnken design model optimized the NADES-based UAE process based on response (TPC, TFC, ABTS, OH, and DPPH). The optimal conditions for the NADES-based UAE process were 70 ml/g of LSR, 38.9% water content in NADES, 67.9 °C, and 24.2 min of extraction time. The predicted values of the Box-Behnken design were compatible with the experimental results. Moreover, scanning electron microscopy (SEM) was used to survey the surface of black mulberry fruit with and without sonication. SEM can assist in demonstrating the destructive effect of NADES and ultrasonic waves on material surfaces. SEM findings indicated the high surface destruction capacity of NADES, which partially contributed to a superior extraction yield of NADES than conventional organic solvents. The study proposes an efficient and green method for extracting bioactive compounds from black mulberry fruits. The black mulberry fruit extracts can be applied to meat preservation and beverages with high antioxidants.

Producing bacterial cellulose from industrial recycling paper waste sludge.

This study aimed to produce bacterial cellulose from paper waste sludge (PWS) as a method of utilizing the cellulose source from the remaining pulp in the material. Initially, PWS was hydrolyzed by sulfuric acid to create an enriched-reducing sugar hydrolysate. One-factor experiments were conducted with a fixed amount of PWS (5 g) to investigate the influence of hydrolysis conditions, including water, sulfuric acid addition, temperature, and retention time, on the production yield of reducing sugars. Based on these results, the Box-Behnken model was designed to optimize the hydrolysis reaction. The optimal hydrolysis conditions were 10 ml/g of the sulfuric acid solution (30.9%) at 105.5 °C for 90 min of retention time 0.81 (gGE/g PWS), corresponding to a conversion yield of 40.5%). Subsequently, 100 ml of the filtered and neutralized PWS hydrolysate was used as the culture to produce the bacterial cellulose (BC) using Acetobacter xylinum, which produced 12 g/L of bacterial cellulose. The conversion yield of bacterial cellulose calculated as the ratio of the weight of produced bacterial cellulose to that of cellulose in PWS reached 33.3%. The structure of the obtained BC was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to indicate the formation of nano-cellulose fiber networks. This research proposed a combined method to convert paper waste sludge into bacterial cellulose, demonstrating the potential for waste utilization and sustainable production of paper industries for added-value products.

Green extraction of total phenolic and flavonoid contents from mangosteen (Garcinia mangostana L) rind using natural deep eutectic solvents.

This research combined ultrasonic-assisted extraction (UAE) and natural deep eutectic solvent (NADES) to recover phenolic and flavonoid components from mangosteen rind. The antioxidant activities were determined using DPPH, ABTS+, and hydroxyl assays. NADES prepared from lactic and 1,2-propanediol had the highest extraction efficiency based on the total flavonoid content (TFC) and phenolic contents (TPC). Single-factor experiments were employed to assess the influence of UAE conditions (liquid-to-solid ratio, temperature, water content in NADES, and time) on TFC, TPC, and antioxidant activities. NADES-based UAE conditions were optimized using response surface methodology with the Box-Behnken design model on five dependent responses (TPC, TFC, DPPH, ABTS, and OH). The optimal conditions for the lactic-1,2-Propanediol-based UAE process were 76.7 ml liquid/g solid with 30.3% of water content at 57.5 °C for 9.1 min. Scanning electron microscopy (SEM) was applied to examine the surface morphology of mangosteen rind before and after sonication. This study proposes an efficient, green, and practical approach for recovering phenolics and flavonoids from mangosteen rinds.

Extraction and Emulsification of Carotenoids from Carrot Pomaces Using Oleic Acid.

This study aimed to use oleic acid-based ultrasonic-assisted extraction (UAE) to recover carotenoids from carrot pomace and emulsify the enriched-carotenoid oleic acid using spontaneous and ultrasonic-assisted emulsification. The extraction performance of oleic acid was compared with traditional organic solvents, including hexane, acetone, and ethyl acetate. The one-factor experiments were employed to examine the impact of UAE conditions, including liquid-to-solid ratios, temperature, ultrasonic power, and time, on the extraction yield of carotenoids and to find the conditional ranges for the optimization process. The response surface methodology was employed to optimize the UAE process. The second-order extraction kinetic model was used to find the mechanism of oleic acid-based UAE. After that, the enriched-carotenoid oleic acid obtained at the optimal conditions of UAE was used to fabricate nanoemulsions using spontaneous emulsification (SE), ultrasonic-assisted emulsification (UE), and SE-UE. The effect of SE and UE conditions on the turbidity of nanoemulsion was determined. Then, the physiochemical attributes of the nanoemulsion from SE, UE, and spontaneous ultrasonic-assisted emulsification (SE-UE) were determined using the dynamic light scattering method. The extraction yield of carotenoids from carrot pomace by using sonication was the highest. The adjusted optimal conditions were 39 mL/g of LSR, 50 °C, 12.5 min, and 350 W of ultrasonic power. Under optimal conditions, the carotenoid content attained was approximately 163.43 ± 1.83 µg/g, with the anticipated value (166 µg/g). The particle sizes of nanoemulsion fabricated at the proper conditions of SE, UE, and SE-UE were 31.2 ± 0.83, 33.8 ± 0.52, and 109.7 ± 8.24 nm, respectively. The results showed that SE and UE are suitable methods for fabricating nanoemulsions. The research provided a green approach for extracting and emulsifying carotenoids from carrot pomace.

Optimized Cellulase-Hydrolyzed Deoiled Coconut Cake Powder as Wheat Flour Substitute in Cookies.

Deoiled coconut cake powder (DCCP) was hydrolyzed to reduce the ratio of insoluble/soluble dietary fiber (RIS) by partially converting insoluble dietary fiber to soluble using Celluclast 1.5 L, a commercial cellulase preparation in citrate buffer medium. Firstly, the influence of citrate buffer amount, enzyme concentration, pH, and retention time on the enzymatic hydrolysis efficiency was investigated. Then, response surface methodology (RSM) was employed to optimize the process in which the insoluble and soluble dietary fiber contents were the responses. The results revealed that 10.3 g buffer/g of materials, 3.7 U/g of the materials, and 60 min of retention time were the optimal conditions for the enzymatic hydrolysis to obtain the insoluble and soluble contents of 68.21%db and 8.18%db, respectively. Finally, DCCP or hydrolyzed DCCP (HDCCP) was partially substituted for wheat flour at different replacement ratios in a cookie recipe at 0, 10, 20, 30, and 40%. The cookies with a 10% replacement ratio of hydrolyzed deoiled coconut cake powders had a lower RIS by more than two folds those of DCCP and had the same sensorial score as the control sample. This study proposed that Celluclast 1.5 L effectively reduced RIS by partially converting insoluble to soluble dietary fiber, improving the soluble dietary fiber content in fiber-enriched cookies.

Optimization of the ultrasonic-assisted extraction process to obtain total phenolic and flavonoid compounds from watermelon (Citrullus lanatus) rind.

This context presents the study of ultrasonic-assisted extraction (UAE) to obtain phenolic and flavonoid compounds from watermelon rind powder (WRP). The antioxidant activity of the extracts was investigated using DPPH and ABTS+ assays. One-factor experiments were conducted to examine the effect of each factor (solid-to-liquid ratio (SLR), acetone concentration (AC), temperature, and time) on the UAE of WRP. Box-Behnken Design (BDD) model was employed to optimize the UAE conditions based on total phenolic contents (TPC), total flavonoid content (TFC), and their antioxidant activities. The optimal conditions were 1:30.50 SLR, 70.71% AC, 29.78 °C, and 10.65 min extraction time. There were no significant differences between predicted and experimental results (less than 6.0%), recommending a feasible and innovative process of deploying UAE to extract phenolics and flavonoids effectively from watermelon rind.

Effects of hydraulic retention time on biohythane production via single-stage anaerobic fermentation in a two-compartment bioreactor.

Hythane has been well known as a mixture of hydrogen and methane gases but their production is mostly in a different way. The present study dealt with the potential biohythane production in a two-compartment (lower, hydrogenesis; upper, methanogenesis) reactor via a single-stage anaerobic fermentation at mesophilic temperature. The effect of hydraulic retention time (HRT) was tested at 10-2 d using food waste substrate. HRT 2 d resulted in (1) maximum removal efficiencies for COD, carbohydrate, lipid and protein contents with values of 58.5, 58.4, 62.6 and 79.1%, respectively; (2) peak hydrogen and methane production rates of 714 and 254 mL/L-d, respectively; and (3) biogas contents of hydrogen 8.6% and methane 48.0% in the produced gas. At this HRT, Clostridium sensu stricto 2 and Methanosaeta were dominant species in H2 and CH4 compartments, respectively. The novelty of this work is creating a novel two-compartment reactor for single-stage anaerobic biohythane fermentation.