Amount Of Humic Acid Research Articles

МОДИФІКУВАННЯ ДОРОЖНЬОГО БІТУМУ ГУМІНОВИМИ КИСЛОТАМИ

Modifying road bitumen of the BND 70/100 brand with humic acids was carried out. In particular, the influence of the duration of the process and the amount of addition on the quality characteristics of the binder was studied. It was established that humic acids negatively affect the plastic properties of bitumen (deteriorate the softening temperature, penetration, and ductility), positively affect its elasticity, and have practically no effect on the ability of the binder to adhere to the surface of the mineral material. The main modifying effect of humic acids is a positive effect on the processes of technological aging of road bitumen (the ability of bitumen to age is slowed down). In particular, residual penetration increases, ΔТ (change in softening temperature) decreases, and Δm (bitumen mass) practically does not change. To ensure the maximum positive impact, the optimal duration of modification and the amount of humic acids in the mixture with bitumen were determined.

Synergistic Effects of Humic Acid, Biochar-Based Microbial Agent, and Vermicompost on the Dry Sowing and Wet Emergence Technology of Cotton in Saline–Alkali Soils, Xinjiang, China

Soil amendments such as humic acid (HA), a biochar-based microbial agent (M), and vermicompost (V) can improve soil quality and promote crop growth. However, it remains unclear whether the co-application of the three soil amendments (HMV) has a synergistic effect on alleviating soil quality deterioration obstacles caused by dry sowing and wet emergence technology in Xinjiang cotton fields. A three-year field experiment was conducted in saline–alkali soils using plastic-film-mulched drip irrigation in Xinjiang, China. Through the orthogonal experiment method, the application amounts of HA, M and V were 75 kg ha−1, 75 kg ha−1 and 225 kg ha−1 respectively in 2021. In 2022, three application amount gradients were used for HA, M and V: 60 kg ha−1, 90 kg ha−1 and 120 kg ha−1 respectively. In 2023, the application amounts of HA, M, and V were 60 kg ha−1, 120 kg ha−1, and 120 kg ha−1. It should be pointed out that V contains HA in the range of 20–35%. This study aimed to explore the improvement effect of a single or combined application of HA, M, and V on soil quality and cotton emergence rate using dry sowing and wet emergence technology in Xinjiang cotton fields. The results showed that the single and combined applications of HA, M, and V improved the soil quality and water–heat–salt environment of the cultivated layer. In the combined application, the cotton seedling emergence rate and yield increased by 1.9–22.8% and 7.0–54.1%. Therefore, it is recommended to jointly apply HA, M, and V to promote cotton seedling emergence and increase yield using dry sowing and wet emergence technology in Xinjiang cotton fields.

Evaluating the suitability of sedimentological, geochemical, and biological proxies for reconstructing floodplain palaeohydrology

Fundamental insight into the long-term ‘geoecohydrological’ dynamics of rivers and floodplains is required for their sustainable management. To study these dynamics, a multi-proxy approach is essential. While suitable proxies are available for reconstructing floodplain geomorphology and past vegetation, the suitability of the available proxies for past hydrology to reconstruct floodplain wetness has not yet been evaluated. In this study, we apply a multi-proxy analysis combining testate amoebae and several geochemical proxies for decomposition (humification, carbon and nitrogen stable isotopes), in comparison to sedimentological (stratigraphy, loss on ignition) and palaeobotanical records, to obtain independent hydrological reconstructions of alluvial floodplains in contrasting environmental settings to explore the suitability of the available proxies for past hydrology to reconstruct floodplain wetness.This study concludes that testate amoebae cannot provide a continuous and reliable hydrological reconstruction, as they are insufficiently preserved in alluvial peat deposits. In addition, mineral particles within the tests size range hamper the analysis in mineral-dominated sediment units. As organic matter decomposition is low when water tables are high and vice versa, we expected the decomposition proxies to reflect the hydrological conditions. While the amount of humic acids appears to depend mainly on the substrate rather than the decomposition of the organic matter in it, the analyses of carbon and nitrogen stable isotopes provide promising results, for both peat and non-peat deposits.

Effects of Organic Substrate Amendments on Selected Organic Fractions and Biochemical Parameters under Different Soils.

The application of organic substrates can affect soil respiration, dehydrogenase (DH-ase) activity, dissolved organic carbon (DOC), and humic acid (HA) fractions. This study aimed to evaluate the effects of five organic substrates in the organic fractions of degraded alluvial soil, acid sulfate soil, and sandy soils and the physicochemical properties of the soil. Soil samples were amended at a rate of 5 tons ha-1 with (1) water hyacinth compost, (2) sugarcane filter cake compost, (3) biogas sludge-rice straw compost, (4) vermicompost, and (5) sludge. The results showed that soil respiration and DH-ase activity increased rapidly within the first 5 days of incubation, while the concentrations of DOC and HA decreased throughout the incubation period. The highest respiration and DH-ase activity occurred after the application of vermicompost. DOC was found to be the highest in soils amended with sugarcane. The highest concentration of HA was observed with the application of sugarcane residues, regardless of the type of soil. The application of water hyacinth and biogas sludge stimulated cumulative HA only in the acid sulfate soil, while vermicompost improved HA only in the degraded soil. The largest stimulation in respiration and DH-ase activity was observed in degraded and sandy soils, regardless of the type of amendment. In the acid sulfate soil (3.7 mg·C·g-1), larger amounts of DOC and HA were observed than in both degraded (1.7 mg·C·g-1) and sandy soils (1 mg·C·g-1). However, DH-ase activity was the lowest in acid sulfate soil.

Effect of ramial chipped wood and poultry manure amendments on soil chemical properties and fungal communities in Benin

This study investigated effects of soil amendments with ramial chipped wood (RCW) derived from Gmelina arborea and Sarcocephalus latifolius, together with poultry manure, on soil chemical properties and fungal communities in northern and southern Benin. The trial was a split-plot experiment, where treatments included volume of irrigation water (V1 and V2 = 0.5 *V1) as the whole-plot factor, with organic amendment (45 t/ha RCW; 15 t/ha poultry manure, PM; 45 t/ha RCW + 15 t/ha of PM, RCW_PM; and control) as the sub-plot factor. Topsoil was sampled before and after 24 months of in situ organic amendment application. Humic acid (HA) was extracted from soil and purified prior to FTIR spectroscopy, NMR, and Py-GC-MS analyses. RCW treatments (RCW and RCW_PM) contributed substantially to organic carbon storage and soil nutrient (N, P, K, Ca, Mg) increases (the latter by up to 1.5 times) compared to the control. Accordingly, soils that were amended with the RCW produced significant amounts of HA. High concentrations of lignin-related compounds were determined in pyrolysis products from humic acids in the RCW-amended soils. Using ITS2 region sequencing on the Illumina Miseq platform, RCW amendments markedly altered fungal compositions, with increased relative abundance of Ascomycota (up to 92% of total fungal community), Mucoromycota (2.7%), Basidiomycota (2.5%) and Rozellomycota (0.3%). These fungal phyla contain species that participate in organic matter decomposition and compound transformations but did not selectively degrade lignin in RCW. Our results suggest that RCW amendments significantly increased fungal activity and improved soil nutrient availability. Thus, this agrotechnology is recommended for regenerative agriculture.

Influence of organic matter on the photocatalytic degradation of steroid hormones by TiO2-coated polyethersulfone microfiltration membrane

Water treatment in photocatalytic membrane reactors (PMR) holds great promise for removing micropollutants from aquatic environments. Organic matter (OM) that is present in any water matrix may significantly interfere with the degradation of steroid hormone (SH) micropollutants in PMRs. In this study, the interference of various OM types, humic acid (HA), Australian natural organic matter (AUS), worm farm extract (WF), tannic acid (TA), and gallic acid (GA) with the SH degradation at its environmentally relevant concentration (100 ng/L) in a flow-through PMR equipped with a polyethersulphone-titanium dioxide (PES-TiO2) membrane operated under UV light (365 nm) was investigated. Results of this study showed that OM effects are complex and depend on OM type and concentration. The removal of β-estradiol (E2) was enhanced by HA at its levels below 5 mgC/L while the enhancement was abated at higher HA concentrations. The E2 removal was inhibited by TA, and GA, while no significant interference observed for AUS, and WF. The data demonstrated diverse roles of OM that acts in PMRs as a light screening agent, a photoreactive species scavenger, an adsorption alteration trigger, and a photosensitizer. The time-resolved fluorescence measurement showed that HA, acting as a photosensitizer, promoted the sensitization of TiO2 by absorbing light energy and transferring energy/electron to the TiO2 substrate. This pathway dominated the mechanism of the enhanced E2 degradation by HA. The favorable effect of HA was augmented as increasing the light intensity from 0.5 to 10 mW/cm2 and was weakened at higher light intensities due to the increased scavenging reactions and the limited amount of HA. This work clarifies the underlying mechanism of the OM interference on photocatalytic degradation of E2 by the PES-TiO2 PMR.

Evaluating the impact of the humic acid amendment on antibiotic resistance genes reduction and product quality during swine manure composting

The overuse of antibiotics in livestock farms and their subsequent accumulation in manures lead to increase antibiotic resistance genes (ARGs) in the compost products. Yet, the function of humic acid (HA) in shaping antibiotics and ARGs abundances, microbial structure, and product quality during composting remains unclear. Here, the efficiency of added HA in reducing antibiotics and ARGs abundances during swine manure (SM) composting was studied using five rates of HA: 0%, 1%, 2%, 4%, and 6%. The findings indicated that the abundance of ARGs types such as LSM, bacitracin, macrolide, sulfonamide, tetracycline, and vancomycin and ARGs subtypes including MacB, MexD, OleB, SrmB, Sul1, VanHB, VanSB, pbp2b, tetPB, and tetX decreased significantly under 6% HA amount compared with CK compost (P < 0.05). Besides, the added 6% HA shaped the abundance of the bacterial community (notably Acinetobacter, Pseudoxanthomonas, and Luteimonas), as well as the level of carbohydrate metabolism and amino acid metabolism (6.9% and 5.4%, respectively), which can be taken as an indicator for microbial activity, thereby accelerating antibiotics decrease. RDA analysis revealed that TOC, moisture content, and pH considerably influenced microbial activity and ARGs reduction (P < 0.05). The estimation of compost quality indicated that 6% HA significantly improved the total content of humic substance and HA to 120.7 ± 1.02 g/kg and 62.3 ± 0.92 g/kg, and reduced the content of fulvic acid to 12.8 ± 1.22 g/kg, thus promoting antibiotics and ARGs reduction. Overall, this study offers a promising option for improving compost quality and safety and mitigating ARGs circulation in the natural environment.

Effects of Incorporating Different Proportions of Humic Acid into Phosphate Fertilizers on Phosphorus Migration and Transformation in Soil

Incorporating humic acid (HA) into phosphate fertilizers to produce HA-enhanced phosphate fertilizers (HAPs) can improve the migration and availability of fertilizer-derived phosphorus (P) in soil. However, the optimal proportion of HA remains inconsistent. Here, we investigated the effects of HAPs with different HA proportions (0.1–10% w/w) on water-soluble P fixation rate, P migration, P transformation, and soil microorganisms, and analyzed the main P forms in HAP using Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The results showed that incorporating 0.1% HA had no impact on P migration and transformation, whereas incorporating 0.5–10% HA increased the migration distance and cumulative migration of fertilizer-derived P by 0–5 mm and 17.1–30.3%, respectively, compared with conventional phosphate fertilizer (CP). Meanwhile, HAPs with 0.5–10% HA significantly reduced the water-soluble P fixation rate by 18.3–25.6%, and significantly increased the soil average available P (AP) content in 0–40 mm soil layer around the P application site by 6.2–12.9% relative to CP, partly due to the phosphate monoesters in HAPs. Clustering analysis revealed that 0.5% HA had similar effects relative to higher HA proportions (1% and 5%), and the inhibition of HAP with 0.5% HA on bacteria and fungi was also greater than that of CP due to the high concentration of soil P. Overall, 0.5% was determined to be the optimal amount of HA for HAP production, which provided a theoretical basis for the development of high-efficiency phosphate fertilizer.

The Adsorption Behaviors and Mechanisms of Humic Substances by Thermally Oxidized Graphitic Carbon Nitride.

Thermal oxidation is efficient for enhancing the photocatalysis performance of graphitic carbon nitride (g-C3N4), while its effect on adsorption performance has not been fully studied, which is crucial to the application of g-C3N4 as adsorbents and photocatalysts. In this study, thermal oxidation was used to prepare sheet-like g-C3N4 (TCN), and its application for adsorption of humic acids (HA) and fulvic acids (FA) was evaluated. The results showed that thermal oxidation clearly affected the properties of TCN. After thermal oxidation, the adsorption performance of TCN was enhanced significantly, and the adsorption amount of HA increased from 63.23 (the bulk g-C3N4) to 145.35 mg/g [TCN prepared at 600 °C (TCN-600)]. Based on fitting results using the Sips model, the maximum adsorption amounts of TCN-600 for HA and FA were 327.88 and 213.58 mg/g, respectively. The adsorption for HA and FA was markedly affected by pH, alkaline, and alkaline earth metals due to electrostatic interactions. The major adsorption mechanisms included electrostatic interactions, π-π interactions, hydrogen bonding, along with a special pH-dependent conformation (for HA). These findings implied that TCN prepared from environmental-friendly thermal oxidation showed promising prospects for humic substances (HSs) adsorption in natural water and wastewater.

Influence of Peat Soil Environment on Mechanical Properties of Cement-Soil and Its Mechanism

The influence of peat soil environment (PSE) on the mechanical properties of cement-soil in the area around Dianchi Lake and Erhai Lake in Yunnan Province has attracted much attention. This study explores the change law of cement-soil UCS in the PSE, and provides guidance for the development and sustained usage of peat soil foundation. The paper discusses the preparation of cement-soil samples by adding humic acid (HA) and cement to cohesive soil with low organic matter content (blending method) and soaking it in fulvic acid (FA) solution and deionized water (steeping method) to simulate the actual working environment of cement-soil. Unconfined compressive strength (UCS), acid consumption, ion leaching, scanning electron microscope (SEM), and X-ray diffraction (XRD) tests are carried out on cement-soil samples soaked for 90 days. The results show that HA can significantly reduce the UCS of cement-soil. FA can reduce the UCS of cement-soil when the content of HA is less than 18%. However, when the amount of HA is more than 18%, the UCS of cement-soil increases slightly. FA makes the deformation and failure type of cement-soil gradually change from brittle shear failure to plastic shear failure. FA reacts with the cement hydration products in the sample so that the cumulative acid consumption of the cement-soil sample continues to increase, and the dissolution of Ca2+, Mg2+, Al3+, and Fe3+ in the sample increases the ion concentration of the soaking solution. In addition, SEM and XRD show that HA can increase the macropores and connectivity of cement-soil, while FA fills part of the pores of the wetting layer. In the PSE, FA can strengthen the inner structure of HA particles and fill and cement the layers of cohesive particles, enhancing the construction of cement-soil with HA content greater than 18%, so that its UCS is relatively improved. However, when the amount of HA is less than 18%, there are more small pores in the cement-soil. The interaction between FA and HA in the cement-soil is weak. The influence of FA on cement-soil is mainly a weakening effect, and its UCS is relatively reduced.

Effect of humic acid on phytoremediation of heavy metal contaminated sediment

The phytoremediation performance of Mentha Aquatic, Typha Orientails Presl, Tagetes Patula L. and Iris Tectorum Maxim was investigated by pot experiments to remediate the heavy metal contaminated sediment added with 1‰, 3‰, and 5‰ humic acid (HA), respectively, over 60 days. The results showed that the four hydrophytes could get a better accumulation for Cd, Cu, Pb, and Ni from sediments with 3‰ HA as amendment. While, Mentha Aquatic, Typha Orientails got the maximum accumulation amount of Cu, Pb with 5‰ HA as amendment. As for Typha Orientails Presl, Tagetes Patula L. and Iris Tectorum Maxim, 3‰ HA was the optimum addition for sediments to accumulate Cd, with over 10% increase compared to the control sediment. An appropriate amount of HA as amendment can decrease the percent of residual fraction and improve the phytoremediation for metal contaminated sediments.

Determination of Humic Acid Content in Sapropel

The agricultural industry, in particular crop farming, is in need of using biological plant and soil protection products, as well as mineral fertilizers. A number of problems associated with soil contamination with substances of chemical nature that are part of mineral fertilizers can be solved through the use of biofertilizers based on humic acids (HA). HA can also be used as plant growth stimulants, restorers of disturbed soils and sorbents of toxic pollutants. One of the promising sources for obtaining HA is sapropel obtained during the reclamation of reservoirs. The study was conducted in order to determine the concentration of humic acids in sapropel harvested in the water bodies of the Republic of Mari El (RME) and to identify the method that assumes the best yield of HA. The object of the study were sapropel samples of various water bodies of the RME. Humic acids were isolated by two methods: the method of alkaline extraction and the method of aqueous extraction. According to the results of the study, significant differences in humic acid concentrations in sapropel samples were noted. It was found that sapropel of the Lake Vodoozerskoye deposit is characterized by the highest content of humic acids. It was also determined that the sapropel of this deposit is the leader in the amount of HA, regardless of the extraction method.

How and why does time matter - A comparison of fouling caused by organic substances on membranes over adsorption durations

This study investigated the effect of time on the severity of adsorptive fouling on polyvinylidene fluoride (PVDF) membrane surface. Sodium alginate (SA), bovine serum albumin (BSA), and humic acid (HA) were selected as representative membrane foulants. We examined the fouling behavior of these three selected model foulants over different adsorption durations (i.e., ~2300 and ~20,000 s). The fouling experiments were performed under conditions with and without the presence of Ca2+. For the SA-Ca2+ system, a longer adsorption duration slightly increased adsorption amount of SA but sharply reduced the reversibility (from 86.8 % to 12.9 %). For BSA-Ca2+, extended time did not change the deposition amount of BSA on the membrane surface, but led to more residual BSA after cleaning (reversibility decreased from 11.3 % to 4.5 %). Similarly, in the HA-Ca2+ system, adsorption duration barely influenced the adsorption amount of HA, while reduced its reversibility from 39.4 to 32.2 %. Therefore, time duration significantly influenced the amount and reversibility of membrane fouling depending on their chemical property. Corresponding results can be well reflected by a selected mathematical model. Further investigation on relevant mechanisms was conducted, quartz crystal microbalance with dissipation (QCM-D) and atomic force microscope (AFM) measurements indicated that longer adsorption duration resulted in more compacted fouling layer and stronger foulant-membrane interaction force. Our results suggest that time (adsorption duration) plays an important role in determining the reversibility of membrane fouling, while the severity is related to the inherent characteristics of foulants.

Removal performance and mechanism of the dissolved manganese in groundwater using ultrafiltration coupled with HA complexation

Ultrafiltration (UF) coupled with humic acid (HA) complexation is used to remove manganese (Mn) in groundwater, performance, influencing factors and mechanisms are investigated. The UF alone couldn’t remove the dissolved divalent Mn(Mn(Ⅱ)) effectively, but dosing of a certain amount of HA increased the removal efficiency. The maximum removal efficiency (> 90%) was observed at a C/Mn molar ratio higher than 50, and the corresponding Mn(Ⅱ) concentrations in permeate were less than 0.05 mg/L. In addition, the Mn(Ⅱ) removal was also interfered with the transmembrane pressure (TMP), solution pH, and coexisted cations. The mechanisms of Mn(Ⅱ) removal were analyzed by atomic force microscope (AFM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), 13C cross polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR) and two-dimensional correlation spectroscopy (2D-COS) analysis. The results showed that the macromolecular complexes were produced by the complexation of Mn(Ⅱ) and the carboxylic (-COOH) and phenolic hydroxyl (phenolic-OH) groups of HA. Subsequently, the complexes could be effectively rejected by the UF membrane and formed the cake layer with the filtration time. It should be noted that Mn(Ⅱ) removal became higher than HA at higher C/Mn molar ratios, which indicated the Mn(Ⅱ) removal was not only by the way of molecular sieving but also by the electrostatic attraction of the cake layer. In the continuous tests, the combined process could remove Mn(Ⅱ) availably and the irreversible fouling of UF membrane could be avoided through the proper operation. These results suggest that UF coupled with HA complexation can be used as a viable strategy for the removal of dissolved Mn(Ⅱ) from groundwater.

Humic Acids Formation during Compositing of Plant Remnants in Presence of Calcium Carbonate and Biochar

The investigation of the mechanisms organic matter transformation in compost organic fertilizers is an urgent task of modern soil ecology and soil chemistry. The main components of such fertilizers are newly formed, weakly humified labile humic acids (HAs). The objective of the study is to determine the mechanism of converting the newly formed HAs into the forms with increased resistance to microbiological and biochemical influences. Obtained during the plant residues decomposition, HAs were studied in the incubation experiment (0, 30, 90 days). Calcium carbonate and biochar produced by rapid pyrolysis from birch and aspen wood, at 550 °C, were used as the composting mixture compounds. Decomposed plant residues—fresh aboveground mass of clover (Trifolium pratense L.), rye (Secale cereale L.), as well as dry oat straw (Avena sativa L.) were the material used for humification. To obtain Has, 0.1 M NaOH and 0.1 M Na4P2O7 were used. Then, HAs were separated from fulvic acids (FAs) using a 0.5 M H2SO4. The amount of labile HAs (HAs1) was estimated by their content in 0.1 M NaOH. The amount of stabilized HAs (HAs2) was calculated by the difference between the HAs content in 0.1 M Na4P2O7 and 0.1 M NaOH. Preparation of HAs for elemental composition and NMR analysis was performed according to the International Humic Substances Society’s recommendations. The possibility of converting newly formed HAs into stable forms (calcium humates), whose share in the HAs composition reaches 40–50%, has been shown. However, the mechanism of HAs transformation under the studied reagent’s influence was different. In the presence of calcium carbonate, it is caused by the physicochemical processes of newly formed HAs rearrangement. However, in the presence of biochar, this is due to the humification processes’ intensification and to the increase in the aromatization degree confirmed by the increase in the optical density, as well as by the increase in carbon and oxygen proportion, and by the decrease in hydrogen proportion in HAs molecules. The understanding of HAs formation and transformation mechanisms at the early humification stages can help to optimize the methods of obtaining organic fertilizers.

STUDY OF BIODEGRADABLE FILMS BASED ON CELLULOSE ETHERS WITH BACTERICIDAL PROPERTIES

The article shows research on the development of the latest biodegradable films with bactericidal properties based on hydroxypropylmethylcellulose modified with brown coal humic acids. Hybrid biodegradable films with bactericidal properties were obtained by pouring solutions of hydroxypropylmethylcellulose with a concentration of 2 wt.%, to which different amounts of humic acid were added. When obtaining biodegradable films with bactericidal properties, hydroxypropylmethylcellulose of the Walocel™ brand manufactured by Dow Corning (USA) was used. As hybrid modifiers, humic acids were used, obtained by extraction of brown coal with an alkaline solution of sodium pyrophosphate, followed by extraction with a 1% sodium hydroxide solution and precipitation with mineral acid. Determination of water absorption of samples of biodegradable films in cold water was carried out according to ISO 62:2008, tensile strength properties of biodegradable films were determined according to ISO 527-2:2021, to measure the gas permeability of biodegradable films, the differential pressure method and a vacuum tester VAC-V1 were used. The effect of the hybrid modification of hydroxypropylmethylcellulose with lignite humic acids in terms of the studied performance characteristics increased in the direction of lignite humic acid types No. 3&gt; No. 2&gt; No. 1. It has been shown that hybrid modification by the mechanism of matrix synthesis of biodegradable films with bactericidal properties based on hydroxypropylmethylcellulose with brown coal humic acids makes it possible to reduce their water absorption, increase the basic strength characteristics and impart antibacterial properties to them, which is confirmed by the data on the time of mold appearance. Optimum in terms of strength and performance characteristics are biodegradable films with bactericidal properties at a content of 10% wt. humic acids No. 3. In general, it has been established that hybrid modification with humic acids according to the mechanism of matrix synthesis of biodegradable films based on hydroxypropylmethylcellulose makes it possible to obtain durable water-soluble films with antibacterial properties for use as packaging for dry food products (bread, cereals, nuts, etc.) with an extended shelf life. storage.

Effect of HumicAcid-Heavy Metals on the Nitrogen Removal Performance of ANAMMOX Bacteria and Its Kinetic Analysis

The effects of two typical heavy metal ions[Cu(Ⅱ) and Ni(Ⅱ)] and humic acid on ANAMMOX nitrogen removal (SAA) were studied through batch experiments, and the kinetic model was analyzed. At the same time, the effects of humic acid-heavy metal on ANAMMOX nitrogen removal were discussed. The results showed that ANAMMOX was promoted when ρ[Cu(Ⅱ)] and ρ[Ni(Ⅱ)] were 3 mg·L-1, and SAA was increased by 8.64% and 7.78%, respectively; ANAMMOX was inhibited when the ρ[Cu(Ⅱ)] and ρ[Ni(Ⅱ)] were 20 mg·L-1 and 5 mg·L-1, respectively, and the inhibition effect was more significant with the increase in heavy metal ion concentration. The index fitting showed that the IC50 of Cu(Ⅱ) and Ni(Ⅱ) on ANAMMOX were 29.67 mg·L-1 and 28.75 mg·L-1, respectively. SAA was increased by 7.37% when the ρ(humic acid) was 1 mg·L-1, and the inhibition rate reached 36.80% when the humic acid concentration was 40 mg·L-1. The linear fitting showed that the IC50 of humic acid on ANAMMOX was 58.36 mg·L-1. The modified Michaelis-Menten model could better describe the inhibitory kinetic behavior of heavy metals and humic acid on ANAMMOX. The model fitting showed that the complete inhibition concentrations (I*) of Cu(Ⅱ), Ni(Ⅱ), and humic acid on ANAMMOX were 49.59, 74.46, and 84.27 mg·L-1, respectively. An appropriate amount of humic acid was beneficial to improve the inhibition of heavy metals on ANAMMOX bacteria activity, and excessive humic acid would cause inhibition on ANAMMOX bacteria again.

Improving faba bean seed yield, protein and chlorophyll content by foliar application of humic acid

Humic acid (HA) can be considered as an important alternative to chemical fertilizers in sustainable agriculture. For this purpose, an experiment was conducted for two years (2014–2015) as a factorial in the form of randomized complete block design (RCBD) with three replications in Chalous city. First factor included time of application (T1 – application of HA before planting, T2 – spraying HA at middle of vegetative growth, T3 – spraying HA at early time of reproductive growth). Second factor included the amount of HA as foliar application at four levels (0 (control), 200, 300 and 400 mg l–1 ha–1). The results of the mean comparison show that the highest seed yield was obtained by spraying HA at 200 and 300 mg l–1 ha–1 at the beginning time of reproductive growth and recorded 2821 and 2773 kg ha–1, respectively. The results also show that the highest percentage of protein were recorded by foliar application of HA at 300 mg l–1 ha–1 during T2 treatment. The use of HA at 200 and 400 mg l–1 ha–1 treatments and T2 treatment had the highest protein percentage and protein yield. The results showed that the use of HA at different concentrations had a positive effect on chlorophyll a, b and total chlorophyll, seed yield and protein yield. Also, the time of application of HA had a significant impact on the measured traits. It seems that foliar application at the early period of reproductive growth has improved growth, increased flower fertility, and seed yield by increasing the absorption of nutrients. According to the results, foliar spraying with 300 mg l–1 ha–1 HA at the T3 is the most appropriate treatment for proper faba bean.

Research on preparation and properties of a multifunctional superabsorbent based on semicoke and humic acid

. • A novel superabsorbent composite was prepared by introduction of SC and HA. • Superabsorbent composite showed water retention and slow-release fertilizer functions. • Composite containing 15 wt% of HA and 6 wt% of SC could remarkably improve water retention. • The growth promoting effect of plants was clearly found by adding of PAA/SC/HA in soil. Superabsorbent integrated multiple functions, including absorbing water, preserving water and controlled releasing for fertilizer, which has attracted extensive attention in modern agriculture. In this study, a novel multifunctional superabsorbent of polyacrylic acid/humic acid/semicoke (PAA/HA/SC) with high water retention and favorable slow release performance was developed by incorporation of humic acid (HA) and oil shale semicoke (SC) via a simple free radical polymerization. The water retention, swelling kinetics, pH-dependent and swelling reversibility were investigated systematically. The water retention results showed that the prepared superabsorbent exhibited outstanding water-retention capacities of 824 g/g and 80 g/g in distilled water and 0.9 wt% NaCl solution respectively, as 15 wt% of HA and 6 wt% of SC were introduced into the three dimensional polymeric network of PAA. The slow release behaviors in distilled water and various salt solutions indicated that the release amount of HA was relatively fast in the initial stage, and then became flat after 16 days. Besides, the soil column leaching experiment revealed that the release amount of the HA reached the maximum value of 222.14 mg/L after 9 days, and potted experiment confirmed the growth-promoting effect for plant of PAA/HA/SC. This work explored the practical application of SC in green and sustainable chemical engineering area, also provided an important reference for application of multifunctional superabsorbent in modern agriculture.

Enhanced water permeability and fouling resistance properties of ultrafiltration membranes incorporated with hydroxyapatite decorated orange-peel-derived activated carbon nanocomposites

Hydroxyapatite-decorated activated carbon (HAp/AC) nanocomposite was synthesized and utilized as a nanofiller to fabricate a novel type of polyethersulfone (PES) nanocomposite ultrafiltration (UF) membranes. Activated carbon (AC) derived from orange peel was synthesized by low-temperature pyrolysis at 400 °C. A hydroxyapatite/AC (HAp/AC) nanocomposite was developed by a simple one-pot hydrothermal synthesis method. The UF membrane was fabricated by intercalating HAp/AC fillers into PES casting solution by the non-solvent induced phase separation (NIPS) process. The prepared membranes exhibited a lower water contact angle than the pristine PES membrane. The hybrid membrane with 4 wt% HAp/AC nanocomposite displayed 4.6 times higher pure water flux (~660 L/m2 h) than that of the pristine membrane (143 L/m2 h). In static adsorption experiments, it was found that the amount of humic acid (HA) and bovine serum albumin (BSA) adsorbed by the HAp/AC-PES hybrid membrane was much lower than that of the original membrane due to the electrostatic repulsive forces between them and the surface of the membrane. Irreversible fouling was reduced from 33 to 6 % for HA and from 46 to 8 % for BSA after HAp/AC was incorporated into the PES matrix. After 7 cycles of water-BSA-water, the HAp/AC-PES hybrid membrane maintained a high pure water flux of 540 L/m2 h with an excellent flux recovery ratio (FRR), demonstrating the long-term stability of the membranes. The developed UF membranes outperformed the original PES membranes in terms of permeability, selectivity, and antifouling.