Oxalic Acid Treatment Research Articles

Colonies under dysbiosis benefit from oxalic acid application: the role of landscape and beekeeping practices in microbiota response to treatment

AbstractThe Varroa destructor mite causes severe losses of Apis mellifera colonies, requiring recurring treatments. One such treatment is oxalic acid (OA), considered ecological. However, it is unclear whether OA affects the honey bee gut microbiota or other hive-associated microbiotas. Herein, we studied the effect of three OA treatments (trickling at 2.1% or 4.2%, and sublimation through Varrox®) upon microbial communities associated with workers’ gut, hive bee bread and pupae, sampled from conventionally or ecologically managed colonies under different anthropization levels (located in urban, rural or mountainous landscapes). We hypothesized that treatment with OA would impact the diversity and composition of bacteria and/or eukaryotic communities, and that the effect would be dose-dependent and specific to the beehive niche. Results showed that the microbiomes of apiaries under different anthropization levels and management strategies differed prior to OA application. Neither the bacterial nor the fungal communities of bee bread and pupae shifted due to OA treatment. Independent of the dosage and the application method (trickling or sublimation), OA induced slight compositional changes in the bacterial profiles of honeybee guts. Those changes were stronger the higher the anthropization (in colonies from urban areas under conventional management). OA treatment reduced the relative abundance of several pathogens, such as Nosema ceranae, and decreased the overall bacterial diversity down to values found in less anthropized colonies. Thus, our results suggest that, aside from managing Varroa infestations, OA could have beneficial effects for stressed colonies while not impairing honey bee resilience from a microbial point of view.

Resistance of Varroa destructor against Oxalic Acid Treatment-A Systematic Review.

As Varroa destructor is one of the most important pathogens of Apis mellifera, there are numerous treatment methods, including pharmaceutical and biotechnological approaches. However, the rapid development of resistance to synthetic acaricides by Varroa destructor has become a significant concern. To date, there have been no investigations into the development of resistance to organic acids. This review examines the potential risk of oxalic acid resistance development by evaluating literature sources from the past 30 years following the PRISMA 2020 guidelines. Median annual efficacies are calculated and reviewed over time for several application methods. An efficacy higher than 70% is determined as not resistant. Independent of the method of application, no resistance development can be observed, although there are some outliers of the annual median. These outliers can be explained by brood status or study setting. However, the result is limited by the low number of efficacy values, and further standardised studies are needed.

Evaluation of heavy metal accumulation and tolerance in oxalic acid-treated Phragmites australis wetlands for textile effluent remediation

Water contamination with metals poses significant environmental challenges. The occurrence of heavy metals (HMs) prompts modifications in plant structures, emphasizing the necessity of employing focused safeguarding measures. Cadmium (Cd), lead (Pb), and chromium (Cr) emerge as particularly menacing toxins due to their high accumulation potential. Increasing the availability of organic acids is crucial for optimizing toxic metal removal via phytoremediation. This constructed wetland system (CWs) was used to determine how oxalic acid (OA) treatments of textile wastewater (WW) effluents affected morpho-physiological characteristics, antioxidant enzyme activity, oxidative stress, and HM concentrations in Phragmites australis. Multiple treatments, comprising the application of OA at a concentration of 10 mM and WW at different dilutions (25%, 50%, 75%, and 100%), were employed, with three replications of each treatment. WW stress decreased chlorophyll and carotenoid content, and concurrently enhanced HMs adsorption and antioxidant enzyme activities. Furthermore, the application of WW was found to elevate oxidative stress levels, whereas the presence of OA concurrently mitigated this oxidative stress. Similarly, WW negatively affected soil-plant analysis development (SPAD) and the total soluble proteins (SP) in both roots and shoots. Conversely, these parameters showed improvement with OA treatments. P. australis showed the potential to enhance HM accumulation under 100% WW stress. Specifically, there is an increase in root SP ranging from 9% to 39%, an increase in shoot SP from 6% to 91%, and an elevation in SPAD values from 4% to 64% compared to their respective treatments lacking OA inclusion. The OA addition resulted in decreased EL contents in the root and shoot by 10%–19% and 13%–15%, MDA by 9%–14% and 9%–20%, and H2O2 by 14%–21% and 9%–17%, in comparison to the respective treatments without OA. Interestingly, the findings further revealed that the augmentation of OA also contributed to an increased accumulation of Cr, Cd, and Pb. Specifically, at 100% WW with OA (10 mM), the concentrations of Cr, Pb, and Cd in leaves rose by 164%, 447%, and 350%, in stems by 213%, 247%, and 219%, and in roots by 155%, 238%, and 195%, respectively. The chelating agent oxalic acid effectively alleviated plant toxicity induced by toxins. Overall, our findings demonstrate the remarkable tolerance of P. australis to elevated concentrations of WW stress, positioning it as an eco-friendly candidate for industrial effluent remediation. This plant exhibits efficacy in restoring contaminants present in textile effluents, and notably, oxalic acid emerges as a promising agent for the phytoextraction of HMs.

Oxalic Acid Treatment: Short-Term Effects on Enzyme Activities, Vitellogenin Content, and Residual Oxalic Acid Content in House Bees, Apis mellifera L.

Honeybees (Apis mellifera L.) have to face many challenges, including Varroa destructor infestation, associated with viral transmission. Oxalic acid is one of the most common treatments against Varroa. Little is known about the physiological effects of oxalic acid, especially those on honeybees' immune systems. In this study, the short-term effects (0-96 h) of oxalic acid treatment on the immune system components (i.e., glucose oxidase, phenoloxidase, glutathione S-transferase, catalase activities, and vitellogenin contents) of house bees were preliminarily investigated. Oxalic acid contents of bee bodies and haemolymphs were also measured. The results confirm that oxalic acid is constitutively present in bee haemolymphs and its concentration is not affected by treatment. At 6 h after the treatment, a maximum peak of oxalic acid content was detected on bees' bodies, which gradually decreased after that until physiological levels were reached at 48 h. In the immune system, the oxalic acid treatment determined a peak in glucose oxidase activity at 48 h, indicating a potential defence response and an increase in vitellogenin content at 24 h. No significant changes were recorded in phenoloxidase, glutathione S-transferase, and catalase activities. These results suggest a time-dependent response to oxalic acid, with potential immune system activation in treated bees.

Optimization of oxalic acid treatment for ulvan extraction from Ulva linza biomass and its potential application as Fe(III) chelator

This study investigated the use of oxalic acid as an eco-friendly compound for extracting ulvan from Ulva linza biomass. The concentration of oxalic acid, temperature, and period of extraction were optimized using Box-Behnken design in response of ulvan yield, molecular weight (MW), sulphate content, uronic acid content, purity ratio (total sugars/total phenolics and proteins), and Fe(III) chelation properties. Under the optimized conditions (1.7 % w/v oxalic acid, 64 °C, and 2.63 h), ulvan yield, MW, sulphate content, uronic acid content, and purity ratio were 29.90 % (w/w), 32.22 kDa, 11.01 % (w/w), 8.12 % (w/w), and 12.84, respectively. The optimized ulvan exhibited good Fe(III) chelation of 18.58 % (w/w). The synthesized Fe-ulvan complex released approximately 73 % of the chelated Fe(III) under in vitro simulated gastro-intestinal conditions. Furthermore, both ulvan and Fe-ulvan complex exhibited potent antioxidant properties. FT-IR analysis confirmed the fundamental role played by hydroxyl, carboxyl and sulphate groups in the coordination of Fe(III). Furthermore, MW, MW/sulphate ratio, and MW/uronic acid ratio should be low to enhance the Fe(III) chelation properties of ulvan. The results of the present study shed light on the use of oxalic acid as a simple and environmentally-benign treatment for ulvan extraction, especially for the recovery of low MW ulvan with high yield and good Fe(III)-binding properties.

Influences of sodium hydroxide and oxalic acid treatments on physical, mechanical, thermal properties, and morphology of ramie fibers

The environmentally friendly properties of natural fibers cause their use as reinforcement in polymer matrices to continue to grow. However, its hydrophilic properties can significantly reduce interfacial interactions. Chemical treatment is one method used to reduce the hydrophilic nature of ramie fibers. This study aimed to investigate the effects on ramie fiber of three chemical treatments: oxalic acid at a concentration of 5 (wt.%), sodium hydroxide at 3, 5, and 7 (wt.%), and a combination of both treatments. Physical properties, moisture content, tensile strength, X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), thermal properties, contact angle, and morphology of ramie fibers before and after treatment were observed in this investigation. FT-IR test results showed a partial loss of amorphous content and more intense cellulose peaks in treated ramie fibers. The combination treatment of alkali and oxalic acid gave the best results, which initiated the dissolution of some of the lignin, hemicellulose, and extractive content. XRD results indicated the surface treatment also led to a 20.35% rise in the crystalline index. In addition, there was a significant increase in tensile strength of 136.10 % in fibers soaked with chemicals. The morphology of the fibers with treatment showed defibrillation and loss of contaminants on the fiber surface, which was the cause of the smaller fiber diameter. Therefore, this optimum treatment is expected to improve the interfacial properties of natural fibers and polymer matrices so that they can enhance the properties of composites when applied in industries.

Effects of summer treatments against Varroa destructor on viral load and colony performance of Apis mellifera colonies in Eastern Canada.

Despite the use of various integrated pest management strategies to control the honey bee mite, Varroa destructor, varroosis remains the most important threat to honey bee colony health in many countries. In Canada, ineffective varroa control is linked to high winter colony losses and new treatment options, such as a summer treatment, are greatly needed. In this study, a total of 135 colonies located in 6 apiaries were submitted to one of these 3 varroa treatment strategies: (i) an Apivar® fall treatment followed by an oxalic acid (OA) treatment by dripping method; (ii) same as in (i) with a summer treatment consisting of formic acid (Formic Pro™); and (iii) same as in (i) with a summer treatment consisting of slow-release OA/glycerin pads (total of 27g of OA/colony). Treatment efficacy and their effects on colony performance, mortality, varroa population, and the abundance of 6 viruses (acute bee paralysis virus [ABPV], black queen cell virus [BQCV], deformed wing virus variant A [DWV-A], deformed wing virus variant B [DWV-B], Israeli acute paralysis virus [IAPV], and Kashmir bee virus [KBV]) were assessed. We show that a strategy with a Formic Pro summer treatment tended to reduce the varroa infestation rate to below the economic fall threshold of 15 daily varroa drop, which reduced colony mortality significantly but did not reduce the prevalence or viral load of the 6 tested viruses at the colony level. A strategy with glycerin/OA pads reduced hive weight gain and the varroa infestation rate, but not below the fall threshold. A high prevalence of DWV-B was measured in all groups, which could be related to colony mortality.

Custom-tailored hole transport layer using oxalic acid for high-quality tin-lead perovskites and efficient all-perovskite tandems.

All-perovskite tandem solar cells (TSCs) have exhibited higher efficiencies than single-junction perovskite solar cells (PSCs) but still suffer from the unsatisfactory performance of low-bandgap (LBG) tin-lead (Sn-Pb) subcells. The inherent properties of PEDOT:PSS are crucial to high-performance Sn-Pb perovskite films and devices; however, the underlying mechanism has not been fully explored and revealed. Here, we report a facile oxalic acid treatment of PEDOT:PSS (OA-PEDOT:PSS) to precisely regulate its work function and surface morphology. OA-PEDOT:PSS shows a larger work function and an ordered reorientation and fiber-shaped film morphology with efficient hole transport pathways, leading to the formation of more ideal hole-selective contact with Sn-Pb perovskite for suppressing interfacial nonradiative recombination losses. Moreover, OA-PEDOT:PSS induces (100) preferred orientation growth of perovskite for higher-quality Sn-Pb films. Last, the OA-PEDOT:PSS-tailored LBG PSC yields an impressive efficiency of up to 22.56% (certified 21.88%), enabling 27.81% efficient all-perovskite TSC with enhanced operational stability.

Oxalic acid alleviates chilling injury and positively influences post-harvest parameters of sweet bell pepper by affecting glycine betaine accumulation, cells respiration rate and NADPH oxidase enzyme activity during cold storage

Bell pepper as tropical crop and warm-season vegetable is sensitive to cold storage under temperatures below 7.5 °C. The purposes of the current study were to investigate the influence of pre-harvest treatment of oxalic acid (OA 0, 1, 5, 10, and 15 mM) on some of most important morphological, physiological and bio-chemical characteristics of red bell pepper cv. "2090 Westland" at post-harvest stage, and assessment of mechanisms and enzymatic pathways of crop response to OA treatments. OA treatments greatly reduced the chilling index, and the positive effects of treatments enhanced by increasing the concentration of OA. The energy level (ATP content) of pepper fruits decreased with extending storage duration, but OA treatment maintained the ATP content of fruits. On 24 d of storage, the highest and lowest activity rate of NADPH oxidase enzyme was recorded in control and 10 mM-treated fruits. Extending storage duration led to a significant increase in cells respiration rate, but this increase was more pronounced in control. Oxalic acid as low-risk and environmentally friendly compound could be an appropriate choice to apply as pre-harvest treatment in order to extend shelf-life of bell pepper fruits during cold storage under 4 ºC. The most important mechanisms reaction of OA are enhancing of enzymatic and non-enzymatic antioxidant activities, increasing the accumulation rate of osmoprotectants and regulation of energy metabolism of cells. Pre-harvest treatment of OA 10 mM could be introduced as efficient technique to overcome adverse effects of chilling stress on post-harvest characteristics of bell pepper.

Integrated Pest Management Strategies to Control Varroa Mites and Their Effect on Viral Loads in Honey Bee Colonies.

Honey bee viruses in combination with varroa mite are very damaging for honey bee colonies worldwide. There are no effective methods to control the viral load in honey bee colonies except regular and effective control of mites. Integrated Pest Management strategies are required to effectively control mites with veterinary medicines based on organic compounds. We evaluated the effect of two brood interruption techniques, queen caging (QC) and trapping comb (TC), followed by an oxalic acid treatment, on the mite fall, colony strength, and viral load of Deformed Wing Virus (DWV) and Acute Bee Paralysis Virus (ABPV). In this paper, we report the data obtained in two experimental sites, in Slovenia and Italy, in terms of the varroacide efficacy, colony strength, and viral load. The number of adult bees after the adoption of the two techniques showed similar decreasing trends in both locations. The viral load of Acute Bee Paralysis Virus did not show any significant reduction after 25 days, reported as the number of Real-Time PCR cycles needed to detect the virus. The viral load of DWV also did not show a significant reduction after 25 days. The acaricidal efficacy of the applied protocols was high in both experimental groups and in both apiaries. Both the queen caging and trapping comb techniques, followed by an oxalic acid treatment, can be considered effective varroa treatment strategies, but further studies should be carried out to evaluate the long-term effects on viral loads to plan the Integrated Pest Management strategy with the right timing before wintering.

Oxalic acid treatment delays quality loss and biochemical changes of minimally processed leeks during storage

Oxalic acid treatment delays quality loss and biochemical changes of minimally processed leeks during storage

Pore surface engineering of FeNC for outstanding power density of alkaline hydrazine fuel cells

In alkaline hydrazine fuel cells (AHFCs), the rapid kinetics of hydrazine oxidation contribute to their superior power density compared to other liquid fuel cells. However, the optimization of oxygen reduction reaction (ORR) electrodes in AHFCs has received limited attention, despite the potential importance of ORR as a rate-determining step. The wettability and pore structure of ORR catalysts are critical factors in facilitating reactant supply (O2 and H2O) and improving catalyst utilization. In this study, we synthesized a hierarchical pore structure in a FeNC catalyst by excess iron incorporation and steam activation, and adjusted its water/oxygen gas contact property by oxalic acid treatment. The modified catalyst exhibited improved wettability and optimized triple-phase boundaries. Remarkably, utilizing a 25 cm2 electrode size and non-noble electrocatalysts, the resulting AHFC achieved a significant power density improvement from 630 to 1240 mW cm−2, setting a new record for AHFCs. This research highlights the importance of pore structure and surface engineering, including the role of excess iron, in enhancing the performance of ORR electrodes in AHFCs.

Quality and shelf life of strawberry fruit as affected by edible coating by moringa leaf extract, aloe vera gel, oxalic acid, and ascorbic acid

ABSTRACT In the current study, the most effective concentrations of moringa leaf extract (MLE), aloe vera gel (AV gel), ascorbic acid (1 mM) and oxalic acid (5 mM) were used. Physically mature fruits harvested from a commercial orchard were dipped in aqueous solutions of different edible coatings and kept at ambient conditions (25±2ºC & 55-60% RH) for evaluation of the quality and enzymatic parameters on daily basis till marketability. Current results revealed that 5 mM ascorbic acid treatment resulted in 57% reduced fruit weight loss; while 20% AV gel coating increased firmness by 60% over a 5-day ambient storage period. Application 6% MLE exhibited 50.7% and 49.7% reduced respiration rate and ethylene production respectively. Fruit biochemical quality parameters were also improved with the lowest accumulation of total soluble solids as a result of slow respiration, higher titratable acidity, ascorbic acid contents, carotenoids and anthocyanin contents in all treated fruit. While, total phenolic contents and total antioxidants along with superoxide dismutase, catalase, peroxidase, and anthocyanins were higher in ascorbic acid treated fruits. The activity of poly phenol oxidase enzyme was lowest in fruits treated with 5 mM ascorbic acid solution. Conclusively, the application of different edible coatings was proved to be beneficial as numerous fruit biochemical and antioxidative attributes were improved by ascorbic acid treatment; furthermore, MLE, AV gel and oxalic acid treatments were also helpful in maintaining fruit quality of strawberry fruits over a 5-days ambient storage period.

Phosphorus release and recovery by reductive dissolution of chemically precipitated phosphorus from simulated wastewater

Chemically mediated recovery of phosphorous (P) as vivianite from the sludges generated by chemical phosphorus removal (CPR) is a potential means of enhancing sustainability of wastewater treatment. This study marks an initial attempt to explore direct P release and recovery from lab synthetic Fe–P sludge via reductive dissolution using ascorbic acid (AA) under acidic conditions. The effects of AA/Fe molar ratio, age of Fe–P sludge and pH were examined to find the optimum conditions for Fe–P reductive solubilization and vivianite precipitation. The performance of the reductive, chelating, and acidic effects of AA toward Fe–P sludge were evaluated by comparison with hydroxylamine (reducing agent), oxalic acid (chelating agent), and inorganic acids (pH effect) including HNO3, HCl, and H2SO4. Full solubilization of Fe–P sludge and reduction of Fe3+ were observed at pH values 3 and 4 for two Fe/AA molar ratios of 1:2 and 1:4. Sludge age (up to 11 days) did not affect the reductive solubilization of Fe–P with AA addition. The reductive dissolution of Fe–P sludge with hydroxylamine was negligible, while both P (95 ± 2%) and Fe3+ (90 ± 1%) were solubilized through non-reductive dissolution by oxalic acid treatment at an Fe/oxalic acid molar ratio 1:2 and a pH 3. With sludge treatment with inorganic acids at pH 3, P and Fe release was very low (<10%) compared to AA and oxalic acid treatment. After full solubilization of Fe–P sludge by AA treatment at pH 3 it was possible to recover the phosphorus and iron as vivianite by simple pH adjustment to pH 7; P and Fe recoveries of 88 ± 2% and 90 ± 1% respectively were achieved in this manner. XRD analysis, Fe/P molar ratio measurements, and magnetic attraction confirmed vivianite formation. PHREEQC modeling showed a reasonable agreement with the measured release of P and Fe from Fe–P sludge and vivianite formation.

On the laser surface pre-treatment to enhance the surface texture, wettability and adhesion bonding strength of aluminium 7075-T6 laminates

ABSTRACT In this study, a laser surface pre-treatment strategy was applied to aluminium 7075-T6 alloy, in which the laser power, speed and frequency were varied to determine the best modified surface property in terms of surface wettability. Surface texture, topography, roughness, contact angle and adhesive bonding strength of the treated surface were measured and characterised. Results showed that the laser-treated surface at a laser power of 30 W, speed of 1.2 m/s and frequency of 8 kHz provided the highest surface wettability by showing the lowest contact angle of 17°, which was attributed to the deeper surface cavities and higher surface roughness. The laser treatment increased the adhesion strength up to 8.5 MPa which was 45% higher than that of the untreated surface (of 5.9 MPa). Its adhesion strength nearly matched with that of the oxalic acid treatment. The laser-treated failed specimen shows predominantly adhesion–cohesion failure mode with a strong interfacial bonding. FTIR spectra confirmed the presence of required functional chemical groups of the adhesive after curing, demonstrating a strong bonding force and affinity between the adhesive and the modified surface. The findings clearly indicate that the laser surface pre-treatment would be a viable surface modification strategy without environmental and health hazard to provide adequate strength in the adhesively bonded joints.

Determination of the Efficacy of Thymol, Eucalyptus and Oxalic Acid in the Control of Varroosis in Honey Bees

Objective: The subject of our study is to determine the efficacy and safety of non-chemical compounds thyme, eucalyptus, and oxalic acid against Varroa destructor ectoparasite, which is widely observed in honey bee (Apis mellifera L.) colonies both in our country and in the world. Materials and Methods: The study was designed of five groups and these groups were designed as group 1 (oxalic acid), group 2 (thymol), group 3 (eucalyptus), group 4 (positive control), group 5 (negative control). Seven honey bee colonies were included in each group. The first, second, and third groups were designed to form the treatment groups, and the last two groups to form the positive and negative control groups. Each group consisted of 7 hives. In the treatment groups, oxalic acid was dissolved in glycerin, thyme and eucalyptus were dissolved in ethyl alcohol, and they were absorbed into special towels. Two pieces per beehive were placed on the frames in the beehives. The treatments were applied weekly for 3 wk during the September. Treatment efficiencies were calculated with the Henderson-Tilton formula and the statistical difference between the oxalic acid, thyme, and eucalyptus treatment groups was determined by the General Linear Model procedure. Results: Treatment efficiencies were determined as 91.74%, 82.25%, and 79.2% in oxalic acid, thyme, and eucalyptus treatment groups, respectively. Conclusion: The findings revealed that completely natural herbal extracts and organic acids can be used instead of chemical drugs against Varroosis. Toxication and unnatural deaths were not observed in honey bees throughout the trials. &#x0D; Keywords: Varroosis, Oxalic acid, Thyme, Eucalyptus.

Quality maintenance mechanism of oxalic acid treatment in fresh-cut apple fruit during storage based on nontarget metabolomics analysis

A complicated storage reaction mechanism will occur during the storage period in fresh-cut apples, and oxalic acid could physiologically modify the flesh tissue to achieve preservation purposes. This study revealed the storage quality regulation mechanism treated with oxalic acid (3 mmol⋅L−1) in fresh-cut apples through nontarget metabolomics and physiological analyses. It was discovered that oxalic acid could enhance the antioxidant enzymes activities, i.e. superoxide dismutase, catalase, glutathione reductase, etc., contents of soluble solids, total phenolic and reducing sugar, postpone the enhancement of hydrogen peroxide and superoxide anion, and defer the decrease of titratable acid, hardness and total antioxidant capacity. 427 differentially expressed metabolites were identified by nontarget metabolomics. Among them, mainly involved in glycerol ester metabolism, phenylalanine metabolism, starch and sucrose metabolism, etc. were up-regulated treated with oxalic acid. In summary, oxalic acid could enhance the antioxidant properties and regulate metabolite synthesis, leading to delayed quality deterioration of fresh-cut apples.

Role of Postharvest Oxalic Acid Treatment on Quality Properties, Phenolic Compounds, and Organic Acid Contents of Nectarine Fruits during Cold Storage

Due to the soft texture of the nectarine fruit, there are difficulties in long-term storage of this fruit. Therefore, it is of great importance to extend the postharvest storage period of this fruit species. In this study, the effect of postharvest OA (Oxalic acid) applications (0, 0.5, 1 and 1.5 mM) on the quality and biochemical contents of nectarine fruits was investigated. On the 40th day of storage, 1.5 mM OA doses reduced weight loss (1.96%) and fruit flesh firmness (36 N) by approximately 44% and 20%, respectively, compared to the control group. The most effective dose in reducing the respiratory rate was again 1.5 mM OA. The 1 mM OA dose was determined to prevent the decay rate approximately by 16% compared to the control group. Organic acid contents showed a continuous decreasing trend during storage and malic acid was determined to be the dominant acid in nectarine fruits. At the end of storage, it was determined that a 1.5 mM OA dose prevented the decrease in malic acid content approximately 35% more than the control group. Chlorogenic acid and rutin were detected at a higher rate than other phenolics. It was observed that 1.5 mM OA dose prevented the breakdown of chlorogenic acid and rutin compounds more so than other doses during storage. In this study, it was determined that a 1.5 mM OA dose especially protected the quality properties and biochemical contents of nectarine fruits in the cold storage more than the control group.

Synthesis of high hydrophobicity USY zeolite with excellent VOCs adsorption performance under humid condition: Combined strategy of high temperature steam and acid treatment

Y Zeolite and its ultra-stabilized hierarchical derivative (USY) as absorbents have low adsorption capacity for VOCs under humid conditions thus limits their industrial applications. It is well known that high SiO2/Al2O3 ratio (SAR) can improve the hydrophobicity of zeolite, and the increase of pore volume can enhance the adsorption performance. In the present work, SAR and the pore size of CY were enlarged by oxalic acid-high temperature steam-citric acid treatment, as the framework aluminum in the zeolite was removed and maintaining its structural integrity. The surface morphology and structure of samples were characterized by XRD, BET, TEM, SEM and TG. 27Al MAS NMR, XPS and Pyridine infrared analysis the mechanism of aluminum removal from the CY framework. The dynamic adsorption properties of the samples were systematically investigated with toluene selected as representative volatile organic compounds. The hydrophobicity of the samples was investigated by static water adsorption, and the adsorption kinetics model of the samples were plotted to study their adsorption characteristics. N2 adsorption-desorption results showed that the modified CY material has larger surface area, wider pore size and larger microporous volume than the raw material. On the other hand, with the improved SiO2/Al2O3 ratio and hydrophobicity, the modified USY also exhibited excellent adsorption performance under humid conditions, with 4.2 times more capacity to adsorb toluene. Therefore, this method can provide effective adsorption of VOCs in humid environments.

Response of growth and Pb accumulation characteristics of plants with intercropping Arabis alpina-Zea mays to exogenous oxalic acid

In order to study the effects of oxalic acids on plant growth and Pb accumulation in different parts of the plants of intercropping Arabis alpina and Zea mays, pot experiment was conducted to investigate the changes of oxalic acid contents of the plants and Pb accumulation through exogenous oxalic acid addition (0, 5, 25 and 50 mmol kg−1). The results showed the root biomass of intercropped A. alpina and total biomass of Z. mays increased by 3.22 folds and 2.97 folds with 5 mmol kg−1 oxalic acid treatment. The oxalic acid contents of shoots and root secretions decreased by 86.5% and 44.3%, respectively. The BCF (bio-accumulation factor) and TF (translocation factor) of intercropping A. alpina reduced under 25 − 50 mmol kg−1 oxalic acid treatments. There were relationships between exogenous oxalic acid treatment concentrations and oxalic acid contents of A. alpina shoots, Z. mays root secretions. The Pb contents of shoots of A. alpina and Z. mays were related to exogenous oxalic acid additions and oxalic acid contents of shoots. In general, 5 mmol kg−1 oxalic acid treatment, that can improve plant growth of intercropped A. alpina and Z. mays, which Pb translocation and accumulation of A. alpina were promoted, whereas Pb accumulation of A. alpina was inhibited with 25 − 50 mmol kg−1 concentrations addition. This study will provide a basis for promoting the application of phytoremediation techniques and efficient crop production in heavy metal contaminated areas.