Residual Organic Compounds Research Articles

Thermodynamic Analysis and Synthesis of Metallic Molybdenum Powder via the Solution Combustion Synthesis Process

ABSTRACT This study investigates the production of metallic molybdenum powder through the solution combustion synthesis (SCS) method. Despite thermodynamic challenges posed by potential back-oxidation under equilibrium conditions, the non-equilibrium nature of SCS facilitates the formation of metallic molybdenum. Experimental evidence suggests that Mo6+ actively participates as an oxidizer in the process, leading to the reduction of Mo6+ to Mo4+. Subsequent reduction of MoO2 is primarily driven by reactions with methane, a byproduct of the SCS process. Characterization of the gel precursor reveals the formation of a molybdenum-citric acid dimer. The resulting molybdenum powder exhibits a semi-amorphous structure with a developed specific surface area and low metallic impurity content but contains a significant amount of residual organic compounds. While heat treatment does not effectively remove these impurities, future research efforts should focus on developing purification strategies to minimize organic contamination.

The Influence of Temperature and Stoichiometry on the Optical Properties of CdSe Nanoplatelets.

Colloidal quasi-two-dimensional cadmium chalcogenide nanoplatelets have attracted considerable interest due to their narrow excitonic emission and absorption bands, making them promising candidates for advanced optical applications. In this study, the synthesis of quasi-two-dimensional CdSe NPLs with a thickness of 3.5 monolayers was investigated to understand the effects of synthesis temperature on their stoichiometry, morphology, and optical properties. The NPLs were synthesized using a colloidal method with temperatures ranging from 170 °C to 210 °C and optimized precursor ratios. Total reflection X-ray fluorescence (TXRF) analysis was employed to determine stoichiometry, while high-resolution transmission electron microscopy (HRTEM) and UV-Vis spectroscopy and photoluminescence spectroscopy were used to analyze the structural and optical characteristics. The results showed a strong correlation between increasing synthesis temperature and the enlargement of nanoscroll diameters, indicating dynamic growth. The best results in terms of uniformity, stoichiometry, and optical properties were achieved at a growth temperature of 200 °C. At this temperature, no additional optical bands associated with secondary populations or hetero-confinement were observed, indicating the high purity of the sample. Samples synthesized at lower temperatures exhibited deviations in stoichiometry and optical performance, suggesting the presence of residual organic compounds.

Impact of environmental conditions on organic matter in astrophysical ice analogues

ABSTRACT The existence of organic matter presenting a high molecular diversity in extraterrestrial environments is well documented. To understand the origin of this organic diversity, laboratory experiments were developed and showed that irradiation and thermal alteration of simple molecules such as methanol, water, and ammonia in conditions mimicking astrophysical ice environments. Ices containing water, methanol, and ammonia (H2O: MeOH: NH3) photolyzed and monitored by infrared spectroscopy, while the organic matter formed at room temperature was analyzed in situ with infrared spectroscopy and ex situ with high-resolution mass spectrometry. Those ices irradiated at 77 K and 10−8 mbar shows a significant organic molecular diversity: residual organic compounds contain up to 78 C, 188 H, 123 N, and 37 O. Most of them contains all four CHNO atoms (76–86 per cent), followed by CHO (11–17 per cent), and CHN compounds (5–6 per cent). CHNO and CHO compounds are more aliphatic (34–53 per cent), while CHN compounds are mostly condensed aromatics (83–90 per cent). In this work, our objective is to investigate impacts of environment on this organic molecular diversity by focusing on three parameters: photon dose, pressure, and heating rate during the warming process. Analyses of the residue formed showed that the heating rate and pressure weakly alter the abundance of the final organic material, while the irradiation rate reduced its abundance at high photon doses by a factor of 8. These results give insights on the impact of icy environment conditions in the evolution of astrophysical organic matter.

Pursuing the circularity of wind turbine blades: Thermochemical recycling by pyrolysis and recovery of valuable resources

Wind turbine blades (WTBs) are the primary waste generated by the wind energy industry and represent one of the major challenges associated with renewable energy from a disposal perspective. Therefore, it is necessary to develop recycling processes to address this environmental issue as circular economy strategies are implemented. This work investigates the technical feasibility of a combined thermochemical process to recover high-quality glass fibers from WTBs while optimizing the composition of the liquid and gaseous fractions. For this purpose, a thermal pyrolysis process in the range of 450–500 °C was studied in a laboratory-scale fixed-bed reactor, followed by thermal cracking of the vapors between 300 and 700 °C. The fixed bed reactor in which the pyrolysis was performed was also used to study a secondary thermochemical process under oxidizing conditions in order to remove residual exogenous organic compounds from the recovered fibers (RFs). For the sake of comparison, a muffle furnace was also used in this second stage. The results indicate that high yields of RFs can be recovered (75.8–77.5 wt%) and, depending on the temperature used in the cracking reactor, either valuable gas (up to 12.9 wt%) or phenol-rich oils (in the range of 8.8–18.7 wt%) can be produced. In addition, carbonaceous compounds can be completely cleaned of RFs after an oxidation process in the same pyrolysis unit, providing a highly versatile process. As an additional advantage, it is observed that after oxidation the RFs are functionalized. This work aims at creating a resource-efficient circular economy, specifically for waste generated from end-of-life renewable energy technologies such as wind turbines.

Synthesis and characterization of Co(II) porphyrin complex supported on chitosan/graphene oxide nanocomposite for efficient green oxidation and removal of Acid Orange 7 dye

Catalytic degradation of Acid Orange 7 (AO7) by hydrogen peroxide in an aqueous solution has been investigated using cobalt(II) complex of 5, 10, 15, 20 Tetrakis [4-(hydroxy)phenyl] porphyrin [Co(II) TPHPP] covalently supported chitosan/Graphene Oxide nanocomposite [Co(II) TPHPP]-Cs/GO, as highly efficient and recoverable heterogeneous catalyst. The structures and properties of [Co(II) TPHPP]-Cs/GO nanocomposite were characterized by techniques such as UV–Vis, FT-IR, SEM, EDX, TEM, and XRD. The oxidation reaction was followed by recording the UV–Vis spectra of the reaction mixture with time at λmax = 485 nm. [Co(II) TPHPP]-Cs/GO nanocomposite demonstrated high catalytic activity and could decompose 94% of AO7 within 60 min. The factors that may influence the oxidation of Acid Orange 7, such as the effect of reaction temperature, pH, concentration of catalyst, Acid Orange 7, and hydrogen peroxide, have been studied. The results of total organic carbon analysis (TOC) showed 50% of dye mineralization under mild reaction conditions of AO7 (1.42 × 10−4M) with H2O2 (8 × 10−2M) in the presence of [Co(II) TPHPP]-Cs/GO nanocomposite (15 × 10−3 g/ml) and pH = 9 at 40 °C. The reuse and stability of the nanocomposite were examined and remarkably, even after six cycles of reuse, there was no significant degradation or deactivation of the recycled catalyst. Residual organic compounds in the reaction mixture were identified by using GC–MS analyses. The radical scavenging measurements and photoluminescence probing technology of disodium salt of terephthalic acid indicated the formation of the hydroxyl radical as the reactive oxygen species in the [Co(II) TPHPP]-Cs/GO nanocomposite/H2O2 system. A mechanism for the oxidation reaction has been discussed.

Impact of fiber structure on the heat and mass transfer characteristics of medium density fiberboard from fractal-based microstructure reconstruction

Microwave heating can rapidly desorb residual volatile organic compounds (VOCs) such as formaldehyde in medium density fiberboard (MDF) because of its penetration and selective heating characteristics. To further understanding the desorption of formaldehyde from MDF by microwave heating, it’s essential to reveal the relationship between specific fiber structure and the heat and mass transfer characteristics of MDF. The study used scanning electron microscopy (SEM) to acquire the microstructural characteristics of MDF before and after low-temperature (350 ℃) pyrolysis treatment, including porosity and pore size distribution. A reconstruction model of MDF incorporating fractal theory and microstructural information was developed to explore the impacts of fiber structure on the heat and mass transfer parameters. The results indicate that low-temperature pyrolysis has a minimal impact on the pore structure of MDF, the porosity increased to ∼ 45 % from ∼ 40 % after slightly pyrolysis while the average pore diameter is maintained at 7 μm, thus the changes in structure can be disregarded when studying microwave-induced desorption of VOCs in MDF. Further analysis combined with fractal reconstructed structure shows that the inherent fiber organization in MDF introduces anisotropy to the mass transfer parameters, resulting in approximately ∼ 10 % higher mass transfer capability perpendicular to the thickness direction compared to that along the thickness direction. However, the heat transfer parameters of MDF are not significantly affected by the fibre structure, which indicates its isotropy. This study provides a theoretical basis for future research on microwave-induced desorption of VOCs in MDF by offering insights into heat and mass transfer theory.

Assessment of property profile of post‐industrial polypropylene recyclates through a multivariable recycling process

AbstractThis study provides key insights into the extrusion of a post‐industrial feedstock primarily composed of polypropylene (PP) and reveals its influence on the property profile of the recyclate. The objective of this study was to gain a fundamental understanding of complex process‐property relationships. Therefore, a two‐part experimental design was established. The first part aimed to analyze the feedstock variability by investigating key material properties of recyclates produced under constant processing conditions. The second part aimed to systematically evaluate the effect of the screw speed, filtration setup, and degassing setup on the properties of the recyclates. An industrial‐scale recycling extrusion line was used. The material evaluation included melt mass‐flow rate (MFR), ash content, oxidation induction temperature, tensile and impact properties, degassing performance, and residual volatile organic compounds (VOCs). Higher melt temperatures led to chain scission of the PP fraction, resulting in increased MFR and higher material stiffness. Additionally, a finer filtration positively contributed to the enhanced material stiffness. Furthermore, the mechanical properties were also influenced by the levels of inorganic fillers in the material composition of the feedstock. Finally, the filtration setup had a greater impact on degassing performance and residual VOC levels than the degassing setup and screw speed.

Engineered algal systems for the treatment of anaerobic digestate: A meta-analysis

The objective of this review was to provide quantitative insights into algal growth and nutrient removal in anaerobic digestate. To synthesize the relevant literature, a meta-analysis was conducted using data from 58 articles to elucidate key factors that impact algal biomass productivity and nutrient removal from anaerobic digestate. On average, algal biomass productivity in anaerobic digestate was significantly lower than that in synthetic control media (p < 0.05) but large variation in productivity was observed. A mixed-effects multiple regression model across study revealed that biological or chemical pretreatment of digestate significantly increase productivity (p < 0.001). In contrast, the commonly used practice of digestate dilution was not a significant factor in the model. High initial total ammonia nitrogen suppressed algal growth (p = 0.036) whereas initial total phosphorus concentration, digestate sterilization, CO2 supplementation, and temperature were not statistically significant factors. Higher growth corresponded with significantly higher NH4–N and phosphorus removal with a linear relationship of 6.4 mg NH4–N and 0.73 mg P removed per 100 mg of algal biomass growth (p < 0.001). The literature suggests that suboptimal algal growth in anaerobic digestate could be due to factors such as turbidity, high free ammonia, and residual organic compounds. This analysis shows that non-dilution approaches, such as biological or chemical pretreatment, for alleviating algal inhibition are recommended for algal digestate treatment systems.

UV/TiO2 photocatalysis as post-treatment of anaerobic membrane bioreactor effluent for reuse

Advanced oxidation processes have been widely applied as a post-treatment solution to remove residual organic compounds in water reuse schemes. However, UV/TiO2 photocatalysis, which provides a sustainable option with no continuous chemical addition, has very rarely been studied to treat anaerobically treated effluents. In the current study, the removal of organics and nutrients from an anaerobic membrane bioreactor (AnMBR) effluent is evaluated during adsorption and photocatalysis processes under various conditions of TiO2 dose and UV intensity and compared to the effluent from an aerobic membrane bioreactor (AeMBR). The sequence for preferential adsorption on TiO2 was found to be phosphorus, inorganic carbon and then ammonia/organic carbon were found. The competing effect between the organics and nutrients, along with the low UV transmission efficiency caused by the need for high doses of TiO2, ultimately compromise the organic removal efficiency in the AnMBR permeate. TiO2 dosage was found to have a greater impact than UV intensity on improving the overall removal performance as nutrients are competing for the adsorption site but are not photodegraded. Under the same operational condition, the UV/TiO2 photocatalysis displayed a higher removal efficiency of organic matter and phosphorus in the AeMBR effluent due to a lower initial organics concentration and absence of ammonia as compared to the AnMBR effluent.

Regeneration of graphite from spent lithium‐ion batteries as anode materials through stepwise purification and mild temperature restoration

AbstractGraphite is one of the most widely used anode materials in lithium‐ion batteries (LIBs). The recycling of spent graphite (SG) from spent LIBs has attracted less attention due to its limited value, complicated contaminations, and unrestored structure. In this study, a remediation and regeneration process with combined hydrothermal calcination was proposed to remove different impurities as value‐added resources from SG. This study focuses on the application of different removal methods for different impurity metals by hydrothermal and acid leaching under different conditions for the removal of Cu, Li, Co, Mn, and Ni from SG. Then, mild‐tempreture calcination of SG was performed to remove residual organic compounds. The regenerated graphite (RG) was found to have a better morphology structure and increased pore volume, which is more favorable for the embedding and desorption of lithium (Li) in graphite. In terms of electrochemical performance, the first discharge‐specific capacity of RG at 0.5 C is 359.40 mAh/g, with a retention of 353.49 mAh/g after 100 cycles (retention rate of 98.36%). This study can be a green and efficient candidate for the regeneration of graphite from spent lithium‐ion batteries as anode material by reduced restoration temperature, with different metal resources as by‐products.

Electrocoagulation Coupled to Electro-Oxidation for the Electrochemical Treatment of Hemodialysis Wastewater

Hemodialysis is an extracorporeal kidney replacement procedure to remove impurities or waste products from the blood used to treat kidney failure. During this process, large amounts of water are used, which, lacking control, end up in sewage systems, potentially flushing high levels of organic and inorganic contaminants into the receiver’s aqua biota. In recent years, a hybrid electrocoagulation (EC) and electro-oxidation (EO) process in sequential or simultaneous coupling has been used for the treatment of wastewater.This research considered synthetic water from hemodialysis under acid and basic conditions. To better simulate the presence of organic compounds, 10 mg L-1 of amoxicillin (AMX), an antibiotic commonly present in wastewater from clinics and hospitals, was added. Laboratory and pilot tests were performed using coupled EC and EO. They used stainless-steel (SS-304) and aluminum (Al-6061) as sacrificial anodes that were compared in acidic and basic pH during EC. The SS-304 rod anode and a titanium (Ti) mesh cathode were used during EC in acidic conditions at a field strength of 3.0 V, which was applied for 60 min. After EC, the solution obtained was filtered to separate precipitates. The supernatant was then treated with EO using an IrO2-Ta2O5|Ti (70:30) anode and the Ti mesh cathode while applying 10 mA for 120 min. The wear of the SS-304 anode was identified by scanning electron microscopy (SEM) and microanalysis (EDS). Removal of organic compounds, including AMX, was significant. This result was confirmed by decreased concentration found by diode coupled chromatography (UPLC-UV-Vis) detection.In conclusion, combining EC and EO in a sequential arrangement for the treatment of hemodialysis wastewater was carried out. EC was performed using a cylindrical SS-304 bar electrode (f = 0.8 cm) as an anode and a concentric Ti mesh as the counter electrode. A 3.0 V cell potential was maintained over one hour of electrolysis in acidic pH (pH = 5.06, s = 227 mS cm-1). This treatment yielded a removal efficiency of 86 ± 1.25 % of AMX contaminate (pH = 8.21, s = 217.26 mS cm-1, i = 11.36 mA, E = 0.568 kWh m-3). After EC, it was necessary to include a filtration or separation process to remove the Fe(OH)3 and [AMX-cation-AMX] sludge generated (2.3 g). This separation employed a settler. Subsequently, the supernatant was placed in an EO cell to remove residual organic compounds as AMX. It used a similar cell arrangement as in EC but changed the anode to IrO2-Ta2O5|Ti (70:30) (f = 0.5 cm) to perform the EO of the pharmaceutical product. During this step, the team achieved an overall removal efficiency of AMX of 100 % (pH = 8.14, s = 179.83 mS cm-1, E = 500 kWh m-3). EO was performed using a continuous 10 mA cell current for 2 h. EO generated reaction products ADP 1, ADP 2, and ADP 3. Additionally, this process decreased the content of ‘salty’ cations: Na+, K+, Ca2+, and Mg2+, while generating Cl2 gas at the electrode.

Recyclability of Post-Consumer Polystyrene at Pilot Scale: Comparison of Mechanical and Solvent-Based Recycling Approaches.

Solvent-based and mechanical recycling technology approaches were compared with respect to each process's decontamination efficiency. Herein, post-consumer polystyrene (PS) feedstock was recycled by both technologies, yielding recycled PS resins (rPS). The process feedstock was subjected to four recycling cycles in succession to assess the technology perennity. The physico-chemical and mechanical properties of the rPS were then evaluated to discern the advantages and drawbacks of each recycling approach. The molecular weight of the mechanically recycled resin was found to decrease by 30% over the reprocessing cycles. In contrast, the solvent-base recycling technology yielded a similar molecular weight regarding the feedstock. This consistency in the rPS product is critical for consumer applications. Further qualitative and quantitative analyses on residual organic compounds and inorganic and particulate contaminants were investigated. It was found that the solvent-based technology is very efficient for purifying deeply contaminated feedstock in comparison to mechanical recycling, which is limited to well-cleaned and niche feedstocks.

Surface oxygen vacancies of TiO2–x enabled water transfer photocatalytic hydrogenation of nitrobenzene to aniline without use of co-catalyst

Water transfer photocatalytic hydrogenation of nitrobenzene to aniline is an attractive and environmentally friendly process in chemical manufacturing. Herein, through an in-situ CO reduction pathway, the TiO2-based photocatalysts with surface and subsurface VOs are prepared for water transfer hydrogenation of nitrobenzene to aniline. The CO originated from incomplete combustion of residual organic compounds of the TiO2 precursor (tetrabutyl titanate), can react with the lattice oxygen of TiO2 and obtain rich surface and subsurface VOs TiO2-based photocatalysts without additional reduction reagent. The as-prepared TiO2 catalyst exhibits a desired band structure and rapid separation of photogenerated carriers. Besides, the TiO2 catalyst with surface and subsurface VOs can stabilize intermediates for water transfer hydrogenation. Thus, compared with heteroatom doping and poor-VOs TiO2, the TiO2 catalyst exhibits highly selectivity and conversion for photocatalytic hydrogenation of nitrobenzene substrates without the use of any cocatalyst and reductant H2.

Moving bed biofilm reactor combined with an activated carbon filter for biological nitrate removal

Abstract A massive use of nitrogen based fertilizers in agriculture is worldwide one of the main causes for nitrate contamination of groundwater. Methods for removing nitrate from aquatic environment through physical and/or chemical processes often turn out to be not applicable because of unaffordable financial resource as well as essential infrastructure lack. On the other hand, biological processes seem to have potentiality to overcome these limitations since they are less expensive and easier to be performed. Accordingly, in the present work, a moving bed biofilm reactor (MBBR) filled with Kaldnes K1 as carrier media was used to remove nitrate from a synthetic groundwater at bench scale. Acetate was used as organic source. Different operational conditions were tested: influent nitrate concentrations of 30, 40, 50 and 60 mg/L; hydraulic retention times of 24, 18, 12 and 8 h; and COD/NO3-N mass ratios of 3.00 and 2.98. Experimental results showed that NO3-N = 60 mg L−1, HRT = 8 h and COD/NO3-N ratio = 2.98 were the optimal operating conditions that allowed achieving a NO3-N removal by 99 % and a COD removal by almost 100 %. Moreover, almost no NO2 −-N accumulation and null COD concentration were observed at the optimal operating conditions. An activated carbon filter was placed downstream to remove residual organic compounds prior to disinfection unit, thus avoiding the potential formation of harmful disinfection by-products (e.g. trihalomethanes (THMs)). The MBBR was able to show a rapid recovery whenever the operating conditions were defined as more severe, thus proving that the operating conditions can vary over a wider range. Furthermore, the results showed that the MBBR system can be used effectively as a biological process to remove nitrate from groundwater.

Electrobiochemical skills of Pseudomonas aeruginosa species that produce pyocyanin or pyoverdine for glycerol oxidation in a microbial fuel cell

Pseudomonas aeruginosa can produce pigments, which mediate external electron transfer (EET). Depending on the mediator, this species can be explored in bioelectrosystems to harvest energy or to obtain chemicals from residual organic compounds. This study has compared the performance of microbial fuel cells (MFCs) inoculated with a Pseudomonas aeruginosa isolate, namely EW603 or EW819, which produce pyocyanin and pyoverdine, respectively. The efficiency of these MFCs in glycerol, a typical residue of biodiesel production, were also compared. The MFCs exhibited different performances. The maximum voltage was 411 and 281 mV m2, the power density was 40.1 and 21.3 mW m−2, and the coulombic efficiency was 5.16 and 1.49% for MFC-EW603 and MFC-EW819, respectively. MFC-EW603 and MFC-EW819 achieved maximum current at 560 and 2200 Ω, at 141.2 and 91.3 mA m−2, respectively. When the system was operated at the respective maximum current output, MFC-EW603 consumed the total glycerol content (11 mmol L−1), and no products could be detected after 50 h. In turn, acetic and butyric acids were detected at the end of MFC-EW819 operation (75 h). The results suggested that P. aeruginosa metabolism can be steered in the MFC to generate current or microbial products depending on the pigment-producing strain and the conditions applied to the system, such as the external resistance. In addition, gene cluster pathways related to phenazine production (phzA and phzB) and other electrogenic-related genes (mexGHI-opmB) were identified in the strain genomes, supporting the findings. These results open new possibilities for using glycerol in bioelectrochemical systems.

Membrane distillation for separation and recovery of valuable compounds from anaerobic digestates

Digestate - the wet by-product of the anaerobic digestion (AD) of organic waste - is composed of a mixture of residual organic matter, microbial biomass and inorganic compounds. Although digestate is rich in nutrients, the occurrence of high levels of salinity and soluble ammoniacal nitrogen (N-NH4+) limits its direct exploitation as organic fertilizer and imposes a complex disposal.This study assesses at laboratory-scale the potential of Direct Contact Membrane Distillation (DCMD) for the separation of nutrients and the recovery of water from the liquid phase of the digestate produced by a digester that treats cattle manure and agricultural residues. Experimental tests, carried out at different feed temperature (50–70 °C) and initial pH (6–8.2) of the liquid digestate, aimed at investigating the effect of the operating conditions on the transmembrane flux of water vapor, the concentration of N-NH4+, P-PO3-, and Chemical Oxygen Demand (COD) in both permeate (also referred to as distillate) and retentate streams.For raw digestate, the initial transmembrane flux enhanced from 1.83 L·m−2·h−1 to 5.55 L·m−2·h−1, in response to increasing temperature gradient. Overall, the highest achieved water recovery factor was 40% at a feed temperature of 70 °C. The pH had a limited impact on the transmembrane flux, whereas notably affected the DCMD performance in terms of separation efficiency. In particular, a pH reduction from 8.2 (raw digestate) to 6 was able to completely avoid the transfer of N-NH4+ into the distillate. Compared to the concentration in the raw digestate, the reduction of COD and P-PO3- in the distillate was 99.0% and 99.9%, respectively. Regardless feed temperature, the performance of the process was subjected to a significant decline of evaporation rate due to occurrence of membrane fouling; however, cycles of cleaning with citric acid allowed to partially regenerate the membrane by removing the reversible cake of foulants accumulated on the surface. The results demonstrate an adequate performance of MD process for recovering water and nutrients, leading to a dehydrated fraction of the digestate phase that can be easily stored and used in agronomic practices.

Study on potential microbial community to the waste water treatment from bauxite desilication process.

Discharging waste water from the bauxite desilication process will bring potential environmental risk from the residual ions and organic compounds, especially hydrolyzed polyacrylamide. Characterization of the microbial community diversity in waste water plays an important role in the biological treatment of waste water. In this study, eight waste water samples from five flotation plants in China were investigated. The microbial community and functional profiles within the waste water were analyzed by a metagenomic sequencing method and associated with geochemical properties. The results revealed that Proteobacteria and Firmicutes were the dominant bacterial phyla. Both phylogenetical and clusters of orthologous groups' analyses indicated that Tepidicella, Paracoccus, Pseudomonas, and Exiguobacterium could be the dominant bacterial genera in the waste water from bauxite desilication process for their abilities to biodegrade complex organic compounds. The results of the microbial community diversity and functional gene compositions analyses provided a beneficial orientation for the biotreatment of waste water, as well as regenerative using of water resources. Besides, this study revealed that waste water from bauxite desilication process was an ideal ecosystem to find novel microorganisms, such as efficient strains for bio-desilication and bio-desulfurization of bauxite.

Preparation of Cu-Ce@γ-Al2O3 and Study on Catalytic Ozone Oxidation for the Treatment of RO Concentrate Water

In this paper, a high-efficiency and stable Cu-Ce@γ-Al2O3 catalyst was prepared by taking the reverse osmosis (RO) concentrated water of a sewage treatment plant as the treatment object and activated alumina as the carrier. The preparation factors that affected the catalytic activity of Cu-Ce@γ-Al2O3 were investigated. SEM, EDS, XRD, BET, XRF, and XPS techniques were applied to characterize the catalyst. Optimal working conditions, and degradation mechanism of RO concentrated water were researched. In comparison with the ozone oxidation alone, the Cu-Ce@γ-Al2O3 catalytic ozonation has more reactive groups, significantly improving the treatment effect. Characterization results show that Cu and Ce are successfully supported on the surface of the activated alumina support and mainly exist in the form of oxides (e.g., CuO and CeO2). The loading of metal led to a larger specific surface area and pore volume. The repeated use had an insignificant effect on the peaks of Cu2p and Ce3d energy spectra and caused a small loss of active components. Under these conditions, the removal rate of COD from RO concentrated water by Cu-Ce@γ-Al2O3 catalyst was 85.2%. The stability and salt tolerance of Cu-Ce@γ-Al2O3 catalysts were investigated by catalyst wear rate and repeated use times, respectively. The degradation of organic matter and residual tryptophan-like organic compounds were observed through UV absorption spectroscopy and 3D-EEM. Hydroxyl radicals participated in organic pollutants degradation. Finally, a multi-level-fuzzy analysis evaluation model was developed to quantitatively assess the catalytic ozone oxidation system of the Cu-Ce @γ-Al2O3 catalyst for the treatment of RO concentrated water.

Use of sequentially inoculation of Saccharomyces cerevisiae and Hanseniaspora uvarum strains isolated from honey by-products to improve and stabilize the quality of mead produced in Sicily

Mead is a beverage produced by alcoholic fermentation of honey-must. The starter yeasts that are commonly used for the alcoholic fermentation of honey-must are oenological Saccharomyces cerevisiae strains. The objective of the present work was, for the first time, to apply yeasts of honey by-products origin to evaluate the influences the taste-olfactory attributes of mead. For this purpose, three experimental productions were set up, which included: (i) single inoculation of S. cerevisiae; (ii) single inoculation of Hanseniaspora uvarum; (iii) sequential inoculation of H. uvarum/S. cerevisiae. Two control trials were performed, using a commercial strain of S. cerevisiae of oenological origin and a spontaneous fermentation. The results of the chemical parameters showed differences between the trials in terms of residual sugars, acetic acid, glycerol, ethanol and volatile organic compounds. Sensorial analysis also showed a high heterogeneity among trials. The attributes of sweetness, honey and floral were found in mead fermented with H. uvarum, whereas all meads obtained with S. cerevisiae were dry, balanced and without off-odors and off-flavours. The results obtained showed that the controlled application of conventional and non-conventional yeast strains isolated from honey by-products origin could be a promising approach to improve the quality of meads.

Adsorption of neutral and negatively charged low-molecular-weight carbonyls in reverse osmosis permeates by ion-exchange resins

Reverse osmosis (RO) has been increasing widely used in water and wastewater treatment to provide high-quality water, such as in industrial pure water production and municipal (non)potable water reuse. However, some low-molecular-weight (LMW) compounds, such as LMW carbonyls, penetrate through RO membranes and are present in the RO permeate, resulting in potential risk to human health or industrial production. Ion-exchange (IX) resins are widely used to help eliminate residual LWM organic compounds from RO permeates, but their elimination performance for carbonyls is not well understood. In this study, seven commercially available resins were employed to explore the adsorption performance for the elimination of representative carbonyls in RO permeate. In general, the adsorption performance of selected resins with regular polymer composition, pore structure and functional group was poor for LMW neutral carbonyl compounds, but efficient for carboxylic acids (number of carbon atoms is less than 4). Among target carboxylic acids, the gel-N+(CH3)3 resin exhibited rapid adsorption kinetics, performing better in the removal of LMW carboxylic acids with shorter alkyl chains and more carboxyl groups. In particular, binary carboxylic acids were adsorbed 3–5 times faster on resins compared with their monoacid counterparts. Charge density was the dominant factor affecting the adsorption performance of carbonyl compounds, followed by hydrophobicity, molecular chain length, and the presence of H attached to the carbonyl C. This study implies that neutral carbonyls cannot be efficiently eliminated by IX resin, and green oxidation processes, such as vacuum UV oxidation, are suggested for the conversion of such compounds to readily removable negatively charged carboxylic acids.