Wheat straw, which is a carbon-rich precursor and a common agriculture waste in Sanandaj, was modified to produce hydrochar with high adsorption capacity by the hydrothermal carbonization (HTC) ...method. The hydrochars were tested as adsorbents to remove methylene blue (MB) from aqueous solution, and the effects of various interfering parameters, including pH, MB concentration, and adsorbent dosage, were investigated using artificial neural networks (ANNs) on adsorption modeling. Adsorption isotherms and kinetics were studied to explain the MB adsorption process. The prepared hydrochars were characterized using Brunauer–Emmett–Teller (BET), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDAX), and high-performance liquid chromatography (HPLC) instruments. The maximum MB removal efficiency achieved by hydrochar modified by KOH (0.1 M) and adsorption data fitted well with the Langmuir isotherm and pseudo-second-order kinetics. In terms of elemental composition, the hydrochar sample contained 52.19% carbon (C), 3.37% hydrogen (H), 0.1% nitrogen (N), 0.15% sulfur (S), and 35.66% oxygen (O). The ash content in the sample was 8.50%. The recorded hydrogen-to-carbon ratio (H/C) and oxygen-to-carbon ratio (O/C) indicated a shift towards humification, implying the influence of KOH addition during the hydrochar production process. Additionally, the specific surface area of the hydrochar, as measured by the BET method, was found to be 11.54 m²/g. Among the aromatics, a significant presence of hydroxymethylfurfural (HMF) was detected, with a concentration of 4.70 g/kg DM. The modeling results demonstrated that the concentration of MB had the most substantial impact on the predicted removal, followed by pH, adsorbent dosage, and contact time.
This study presents a new strategy for the production of sustainable manganese fertilizer based on artificial humic substances (AHS). AHS with different manganese concentrations (0‒20%) were ...synthesized from poplar bark under alkaline conditions via hydrothermal treatment. For the 20% manganese formulation, the interaction of manganese with AHS resulted in reduced solubility (from 25.2% to 12.3% organic carbon) and average molecular weight of humic acids (from 11.6 to 3.9 KDa), indicating preferential binding of the high-molecular-weight fraction. The formulation with 5% of manganese achieved optimal manganese loading without compromising the AHS solubility (19.4%). Structural analyses showed only minor changes in AHS in the presence of manganese, indicating that the main structural fragments of the AHS were preserved. Structural, morphological, and spectroscopic characterizations confirmed the formation of amorphous manganese complexes within the AHS matrix, primarily in the plant-available Mn(II) oxidation state. Plant bioassays showed increased manganese uptake with the application of AHS containing 5% Mn compared to MnCl2 alone (64 mg/kg vs. 40 mg/kg in dry cucumber biomass). Interestingly, unmodified AHS at higher concentrations (50 mg/L) further enhanced manganese (67 mg/kg) and iron (up to 209 mg/kg) uptake, highlighting the potential role of AHS in facilitating metal transport.
The existence of a humic substance in water causes the growth of microorganisms and reduces the quality of water; therefore, the removal of these materials is crucial. Here, the ZnO nanoparticles ...doped using transition metals, copper (Cu) and manganese (Mn), were used as an effective catalyst for photocatalytic removal of humic substances in an aqueous environment under ultraviolet, visible light, and light-emitting diode irradiations. Also, we study the effect of the sonocatalytic method. A solvothermal procedure is used for doping, and the Cu- and Mn-doped ZnO nanocatalyst were characterized by means of FTIR, XRD, AFM, SEM, and EDAX analyses. We investigate the effect of operational variables, including doping ratio, initial pH, catalyst dose, initial HS content, and illuminance on the removal efficiency of the processes. The findings of the analyses used for the characterization of the nanoparticles illustrate the appropriate synthesis of the Cu- and Mn-doped ZnO nanocatalysts. We observe the highest removal efficiency rate under acidic conditions and the process efficiency decreased with increasing solution pH, when we tested it in the range of 3–7. Photocatalytic decomposition of HS increases with a rise in catalyst dose, but an increase in initial HS content results in decreasing the removal efficiency. We observe the highest photocatalytic degradation of humic acid while using the visible light, and the highest removal efficiency is obtained using Cu.ZnO. The Cu.ZnO also shows better performance under ultraviolet irradiation compared to other agents.
Hydrothermal carbonization (HTC) solid and liquid products may inhibit seed germination, necessitating post-treatment. The hydrothermal humification (HTH) method addresses this drawback by ...transforming inhibitory compounds, such as aromatics, into artificial humic acids (AHAs) and artificial fulvic acids (AFAs). This study introduces a novel approach by investigating the substitution of the commonly used alkaline agent in HTH, KOH, with hydrated lime to develop cost-effective hydrothermal fertilizers from sugar beet pulp, enriching them with AHAs. It assesses the effects of lime on AHA production and soluble organic compounds compared to KOH. The results indicate that lime significantly reduces furans (from 560 to 3.15 mg/kg DM in solid and from 344 to 3.86 mg/L in process liquid) and boosts sugars and organic acids, especially lactic acid (from 4.70 to 65.82 g/kg DM in solid and from 4.05 to 22.89 mg/L in process liquid), increasing hydrochar yield (68.8% with lime vs. 27.4% with KOH). Despite the lower AHA production with lime compared to KOH (3.47% vs. 15.50%), lime-treated hydrothermal products are abundant in calcium and magnesium, boasting a pH of 7. This property presents a safer and more efficient alternative to hydrothermal fertilizers. The characterization of AHAs aligns with standard and natural humic substances, while lime-assisted HTH products, applied at a level of 0.01% w/w, could significantly enhance wheat growth and nutrient uptake compared to the control group. Importantly, these products show no toxicity on Daphnia magna, underscoring their potential for sustainable agriculture.
Hydrothermal carbonization (HTC) converts wet biomass into hydrochar and a process liquid, but aromatic compounds in the products have been reported as a roadblock for soil applications as they can ...inhibit germination, plant growth, and soil microbial activity. Here, we compared HTC and hydrothermal humification (HTH) of cow manure digestate while varying the initial alkaline content by adding KOH. HTH converted 37.5 wt% of the feedstock to artificial humic acids (A-HAs) found in both solid and liquid, twice that of HTC. HTH reduced phenolic and furanic aromatic compounds by over 70% in solids and 90% in liquids. The A-HAs in HTH resemble natural humic acids (N-HA), based on FTIR, UV–vis spectra, and CHN and XRD analysis. The HTH liquid possesses 60% higher total organic carbon (TOC) than HTC. Although one-third of TOC can be precipitated as A-HA, a high TOC concentration remains in the liquid, which is shown to be mainly organic acids. Therefore, we also evaluated the HTC and HTH liquids for anaerobic biomethane production, and found that compared to the original cow manure digestate, the HTH liquids increased methane yield by 110.3 to 158.6%, a significant enhancement relative to the 17.2% increase seen with HTC liquid. The strong reduction in organic acids during biogas production from HTH liquid indicates the potential for converting soluble byproducts into methane, while maintaining high A-HAs levels in the solid product.
Graphical Abstract
Highlights
Hydrothermal humification of the digestate feedstock created about 37.5 wt% artificial humic acids in both solid and liquid phases.
Increasing the alkaline content of the reaction media significantly decreased the aromatic content in the process liquid while increasing the concentration of organic acids and sugars.
There was little to no gas production observed in the HTH process at higher alkaline contents, indicating carbon preservation in the liquid and solid phases.
Anaerobic processing of the hydrothermal humification (HTH) process liquid resulted in a 158.6% increase in methane production compared to the primary biomass.
The organic acid concentrations decreased after the anaerobic fermentation, while the main HTH product, artificial humic acids, remained nearly unchanged.
This study investigated the efficiency of hydrochar derived from hydrothermal fulvification of wheat straw in adsorbing malachite green (MG) dye. The characterizations of the hydrochar samples were ...determined using various analytical techniques like SEM, EDX, FTIR, X-ray spectroscopy, BET surface area analysis, ICP-OES for the determination of inorganic elements, elemental analysis through ultimate analysis, and HPLC for the content of sugars, organic acids, and aromatics. Adsorption experiments demonstrated that hydrochar exhibited superior removal efficiency compared to feedstock. The removal efficiency of 91 % was obtained when a hydrochar dosage of 2 g L−1 was used for 20 mg L−1 of dye concentration in a period of 90 min. The results showed that the study data followed the Freundlich isotherms as well as the pseudo-second order kinetic model. Moreover, the determined activation energy of 7.9 kJ mol−1 indicated that the MG adsorption was a physical and endothermic process that increased at elevated temperatures. The study also employed an artificial neural network (ANN), a machine learning approach that achieved remarkable R2 (0.98 and 0.99) for training and validation dataset, indicating high accuracy in simulating MG adsorption by hydrochar. The model's sensitivity analysis demonstrated that the adsorbent dosage exerted the most substantial influence on the adsorption process, with MG concentration, pH, and time following in decreasing order of impact.
Limited information is available about potential physicochemical changes that can occur in hydrochar post-production, e.g. during drying and storage. Understanding these changes is crucial not just ...for shaping future research plans, but also for future practical applications. Here we studied the effect of moisture (69.2% and 2.4%) and three storage temperatures (− 18, 4, and 20 °C) over a year on selected organic and inorganic compounds in hydrochar produced from the Hydrothermal carbonization (HTC) of digested cow manure. Comparison of the control wet hydrochars (WHs) and dry hydrochars (DHs) showed changes in organic compound composition due to drying. Overall, the total amount of the selected organic compounds was notably greater in WH (15.2 g kg
−1
DM) compared to DH (11.8 g kg
−1
DM), with variations observed in individual compound concentrations. Drying, however, had no significant influence on the identified inorganic compounds. Storage caused significant changes in both WH and DH, particularly in organic compounds after 12 weeks. Sugars (2–sevenfold), acids (36–371%), and aromatics (58–120%) in stored samples at week 52 were significantly higher than their control values. Changes in the inorganic elements (e.g., Co, K, Mg, Mn, P, S, Sr, and Zn) occurred faster in WH, with significant differences starting from week 1 compared to their control values, while DH showed fewer changes. Based on these changes in both organic and inorganic content, we recommend the optimal storage conditions for future HTC studies to preserve hydrochar properties. Finally, we discussed potential applications for stored hydrochars, with DH showing greater stability, especially at − 18 °C, making it suitable for various applications.
Graphical Abstract
Highlights
Drying of hydrochar and storage time affected concentrations of acids, aromatics, and sugars significantly
Changes were observed at all storage temperatures—dried hydrochar stored at − 18 °C exhibited higher stability.
Recommended storage conditions could be used for upcoming HTC research and hydrochar applications.
Exposure to bioaerosols causes infection, over-sensitivity, respiratory, and lung diseases. This study was conducted at Sanandaj wastewater treatment plant in three seasons of winter, spring and ...summer to investigate the type and density of bio-aerosols. Sampling was performed using a sampling pump with a discharge rate of 28.3 L/min at a height of 1.5 m above the ground; the samples were taken from five stations: treatment plant entrance, aeration tank, grit chamber, drying sludge bed and laboratory. At each sampling point, time, temperature, relative humidity (Soleimani et al.), wind speed and particulate matter were recorded. In order to identify the bacteria, polymerase chain reaction (PCR) and culture-based methods were applied. It was also found that there was not a significant relationship between bacterial count and RH, wind direction, wind speed and temperature. Regarding fungi, the results showed that RH and wind direction and wind has a significant relationship with the concentration of fungi. The most predominant bacteria and fungi were as follows:
Staphylococcus
,
Enterobacteriaceae
,
Bacillus
,
Acinetobacter
,
Micrococcus
,
Enterococcus
,
Neisseria
,
Listeria
, and
Pseudomonas
and
Penicillium
,
Aspergillus
flavus. The concentration of bacteria in the air was significantly correlated with < 4, < 5, < 7 and < 10 μm suspended particles. However, there was a correlation between particle number of 10 μm and fungi concentration in the air.
Hydrothermal carbonization (HTC) has emerged as a pivotal technology in the battle against climate change and fosters circular economies. Operating within a unique reaction environment characterized ...by water as a solvent and moderate temperatures at self-generated pressures, HTC efficiently converts biomass residues into valuable bio-based products. Despite HTC’s potential—from the management of challenging biomass wastes to the synthesis of advanced carbons and the implementation of biorefineries—it encounters hurdles transitioning from academic exploration to industrial implementation. Gaps persist, from a general comprehension of reaction intricacies to the difficulty of large-scale integration with wastewater treatments, to the management of process water, to the absence of standardized assessment techniques for HTC products. Addressing these challenges demands collaboration to bridge the many scientific sectors touched by HTC. Thus, this article reviews the current state of some hot topics considered crucial for HTC development: It emphasizes the role of HTC as a cornerstone for waste management and biorefineries, highlighting potentialities and challenges for its development. In particular, it surveys fundamental research aspects, delving into reaction pathways, predictive models, analytical techniques, and HTC modifications while exploring HTC’s crucial technological applications and challenges, with a peculiar focus on combined HTC, wastewater integration, and plant energy efficiency.
Background: Tea is one of most frequently consumed beverages in the world. Only in Iran, around 12000 tons of tea is annually used. Besides, green tea, which is made from Camellia sinensis leaves and ...buds, is very popular among people. Although teas have health benefits, since they may be much drunk, they may pose a threat to consumers’ health because of absorbing various ions in their leaves. Unfortunately, there are a limited number of studies on the health effects of green teas. Methods: It was a cross-sectional study performed in 2021. In this research, the concentrations of ions: fluoride (F), chloride (Cl), nitrate (NO3 ), sulfate (SO4 ), and phosphate (PO4 ) in the six bestselling green tea brands, both loose and bag, in Iran were detected by means of ion chromatography. Results: The highest amounts of F, Cl, NO3 , SO4 , and PO4 in the brands were found to be, respectively, in 0.27310, 0.62103, 0.83533, 1.28067, and 1.1037 mg/L. The concentrations of the ions in the both loose and bag tea samples were different significantly. Also, the content of F in the all samples was lower than those acceptable levels suggested by different organizations. Conclusion: It was found that the concentration of the ions was by far lower than those have been introduced as the standard levels. Nonetheless, the water used for tea infusion may contain high levels of these compounds and its volume drunk every day is also very important.
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