Initial pH Value Research Articles

Application of electrochemical flow-through oxidation technology in the treatment of concentrated water from nanofiltration and reverse osmosis in the coal chemical industry.

In the coal chemical industry, the concentrated waters produced by nanofiltration and reverse osmosis are usually evaporated and crystallized. During the evaporation crystallization process, high COD levels can lead to problems such as the entrainment of liquid droplets and excessive amounts of mother liquor. Therefore, there is an urgent need to develop efficient, stable, and engineering-applicable organic matter degradation technologies before the evaporation crystallization process. In this study, Ti-ENTA/SnO2-Sb and GF-5 were combined as cathodes to form an electrochemical flow-through oxidation system to treat nanofiltration concentrate (NFCs) and reverse osmosis concentrate (ROCs). The experimental results show that within the current density range of 10–20mA·cm−2, the chemical oxygen demand (COD) removal rates of NFCs and ROCs are 55.3%–85.2% and 49.9%–93.6%, respectively. And the oxidation system can be used stably for a long time, fully meeting the practical application needs. In addition, this article further analyzed the effects of current density, initial organic matter concentration, pH value, and electrode spacing on COD removal. The results indicate that the COD removal efficiency is mainly affected by current density and initial organic matter concentration. Finally, a comprehensive comparison was made on the efficiency and cost of various advanced oxidation technologies in treating wastewater. The results indicate that the electrochemical flow-through oxidation system has significant cost advantages. The cost of processing NFCs and ROCs per cubic meter is $0.96 and $1.23, respectively. These findings indicate that the electrochemical flow-through oxidation system proposed is an advanced oxidation technology with economic benefits and practical application prospects.

Flavonoids, microbial load and quality parameters changes during shelf-life of fermented milk enriched with pasteurized fig purée

Fig puree is rich in natural bioactive substances including flavonoids and can be useful to produce functional foods. This study investigated the effects of incorporating fig puree into fermented milks formulations on various physicochemical properties, and nutritional and functional compounds during 30 days of refrigerated storage. Fig puree was incorporated into cow fermented milks at 0 g 100 g-1 (control), 10 g 100 g-1, 20 g 100 g-1, 30 g 100 g-1 and 40 g 100 g-1, respectively after fermentation. Initial pH values ranged from 4.48 to 4.84, with no significant changes observed during storage. Microbial counts remained above the acceptable threshold until 30 days in refrigeration. Color parameters indicated a decrease in lightness (L*) and hue (h) values with increasing fig puree content, while a* and b* values increased with increasing fig puree. The fig puree concentration dependently affected the texture analysis and revealed enhanced firmness, consistency, cohesiveness, and viscosity in yogurts with 40 g 100 g-1 of fig puree. Overall, texture stability was maintained during storage period, though slight softening was noted in some formulations. The addition of fig puree reduced syneresis compared to the control which could be attributed to the increase of pectin content. Total phenolic content and DPPH values increased with fig puree addition, with detectable anthocyanins and flavonols, predominantly quercetin-3-galactoside. Levels of these bioactive compounds increased during storage, with the highest amounts found in yogurts containing 40 g 100 g-1 of fig puree after 30 days of storage. These results suggest that fig puree enhances fermented milks properties and stability, offering potential health benefits due to increased bioactive compound content.

Levofloxacin degradation in electro-Fenton system with FeMn@GF composite electrode

In this work, a one-step solvent-thermal approach was used to synthesize an Mn-doped Fe3O4 modified graphite felt (GF) composite electrode material (FeMn@GF), which was then used as the cathode in an Electro-Fenton (EF) system. The levofloxacin (LEV) in wastewater can be successfully removed by the EF system, which can produce and activate H2O2 in situ. The successful fabrication of the FeMn@GF composite electrode was confirmed by employing the characterization techniques of Scanning Electron Microscope, X-ray Diffraction, and X-ray Photoelectron Spectroscopy. Additionally, the electrochemical performance test was conducted. The FeMn@GF composite electrode demonstrated a greater electrochemical activity and a more robust electronic transmission ability. The LEV degradation experiment demonstrated reached 98.9 % that under ambient temperature conditions, within 120 minutes, given initial LEV concentration of 20 mg·L −1, Na2SO4 concentration of 50 mM, applied voltage of 3.0 V, initial pH value of 3, and aeration rate of 3.0 L·min −1.The highest leaching quantities of Fe and Mn were 1.294 mg·L−1 and 0.675 mg·L−1, respectively, while the removal effectiveness of LEV remained at 85.2 % after five cycles. Experiments using radical quenching revealed that the main active species were ·OH. The reaction mechanism of the EF system with FeMn@GF as the cathode (FeMn@GF-EF) and the degradation pathway of LEV were investigated.

Adsorptive Removal of Bisphenol A by Polyethylene Meshes Grafted with an Amino Group-Containing Monomer, 2-(Dimethylamino)ethyl Methacrylate

The adsorptive removal of Bisphenol A (BPA) with the PE meshes photografted with 2-(dimethylamino)ethyl methacrylate (DMAEMA) was performed by varying the grafted amount, pH value, BPA concentration, and temperature, and the adsorption performance was correlated by the equilibrium, kinetic, and isotherm models. In addition, the regeneration of DMAEMA-grafted PE (PE-g-PDMAEMA) meshes was discussed from the repetitive adsorption/desorption process. The adsorption capacity had the maximum value at the grafted amount of 2.6 mmol/g and at the initial pH value of 8.0. The increase in the protonation of dimethylamino groups on grafted PDMAEMA chains and the dissociation of phenol groups of BPA present in the outer solution during the adsorption process results in the increase in BPA adsorption. The adsorption process followed the pseudo second-order equation. The BPA adsorption was enhanced by increasing the BPA concentration and the equilibrium data fit to Langmuir equation. The adsorption capacity stayed almost constant with the increase in the temperature, whereas the k2 value increased against the temperature. These results comprehensively emphasized that BPA adsorption occurred through the chemical interaction or ionic bonding of a BPA anion to a terminal protonated dimethylamino group. Desorption of BPA increased by increasing the NaOH concentration and BPA was entirely desorbed at more than 20 mM. The cycle of adsorption at pH 8.0 and desorption in a NaOH solution at 100 mM was repeated five times without loss or structural damage. These results indicate PE-g-PDMAEMA meshes can be used as a regenerative adsorbent for BPA removal from aqueous medium.

Cultivation of Aurantiochytrium sp. Using Pickle Seasoning Liquid Waste and Application of the Raw Biomass for Fish Aquaculture

AbstractAurantiochytrium sp. strain L3W is a heterotrophic microorganism that produces docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which are essential for the growth of marine fish. In this study, pickle seasoning liquid waste was used for culturing strain L3W and the raw biomass of strain L3W was then fed to red sea bream fingerlings (Pagus major) to confirm its usability as a source of DHA and EPA. The strain L3W was cultured on the three pickle seasoning liquid waste samples, Akimurasaki, Hiroshimana, Shisohijiki, diluted with sand-filtered seawater at initial pH values of 4 and 7 under unsterile conditions. The growth of strain L3W was highest at 3.71 g/L on Hiroshimana at an initial pH of 7 with DHA and EPA production at 71.4 and 6.8 mg/g-biomass, respectively. Preparing the raw biomass of strain L3W by the 200 L-scale cultivation using the American Type Culture Collection 790By+ medium because of the DHA and EPA contents close to that produced in the Hiroshimana medium with an initial pH of 7, the raw biomass was spiked to the diet at 3%, 5%, and 10%. The final DHA and EPA contents in the whole body were increased by 4.26 and 3.03 times, respectively, by adding the strain L3W biomass at 10%. These results confirmed the feasibility of a carbon cycling scenario in which the strain L3W is cultivated using liquid food waste with the resultant biomass is utilized as a source of DHA and EPA for fish aquaculture. Graphical Abstract

Construction of BaTiO3/g-C3N4 heterojunction for promoting atrazine degradation of hydraulic-driven piezocatalytic ozonation

Catalytic ozonation, as a popular water purification technology, was restrained with the dilemma of slow Me(n+m)+/Men+ redox cycle of the convention catalysts. To this end, BaTiO3/g-C3N4 (BTO/CN) piezoelectric heterojunction was designed to enhance atrazine (ATZ) degradation in piezocatalytic ozonation, utilizing the overlooked mechanical forces to activate O3 into reactive oxygen species (ROS). Characterization results demonstrated that the couple of BTO and CN successfully formed a Type-II heterojunction, enhancing the separation of piezoelectric carriers (e- and h+). Moreover, BTO/CN showed the better O3 affinity and O3 activation capability over that of BTO and CN. BTO/CN/O3 process achieved 90.1 % ATZ removal, which was 3.5 and 1.7 times over that of the BTO/O3 and CN/O3 processes, respectively. ATZ removal in BTO/CN/O3 process increased with the initial pH value. Cl-, SO42- and NO3- inhibited ATZ removal, but HCO3- enhanced ATZ removal. O3, •OH, O2- and 1O2 were all involved in ATZ degradation and •OH served as the main ROS, accounting for 79.3 % in degrading ATZ. The internal electric field along with the interfacial electric field synergistically boosted the separation and transfer of charge carriers to provide e- for O3 activation and ROS generation. This study broke through the basic need of continuous sacrifice of e- for O3 activation induced by metal redox cycle and provided a novel catalyst design strategy for piezoelectric ozonation.

MOF derived porous Fe-Cu@carbon catalyst for the degradation of bisphenol A through a persulfate-based advanced oxidation process

A calcination strategy based on the use of mixed MOF HKUST-1/MIL-100 as precursor was used for the obtention of a porous carbon composite (C-HKUST-1/MIL-100) containing iron-copper bimetallic particles within it. The prepared carbon was characterized by XRD, SEM, EDS spectroscopy and N2 adsorption-desorption, confirming the obtention of a micro-mesoporous carbon with Fe-Cu particles homogenously distributed within the structure. For comparison, Cu and Fe-carbons (C-HKUST-1 and C-MIL-100, respectively) were also prepared from the corresponding HKUST-1 and MIL-100 MOFs, respectively. The catalytic performance of the developed carbons as heterogeneous catalysts for persulfate-based advanced oxidation degradation of bisphenol A was evaluated. The Fe-Cu@carbon showed the best catalytic performance, leading to a total BPA degradation after just 10 min of reaction, which was closely related to the synergistic effect of iron and copper. The effect of some key parameters including initial pH value, PS concentration and catalyst dosage was investigated using the Fe-Cu@carbon. In addition, the developed carbon showed good reusability, with no apparent loss in BPA degradation, after five cycles and the ability to treat real water samples, with the advantage that the recovery process after degradation is facilitated thanks to its magnetic properties.

Garlic Peel-Based Biochar Prepared under Weak Carbonation Conditions for Efficient Removal of Methylene Blue from Wastewater

Background: Due to it containing cellulose, hemicellulose, and lignin with abundant specific functional groups which could interact with organic dyes, garlic peel (GP) might be used as an efficient biosorbent. The aim of this study is to evaluate the adsorption performances of GP-based bio-adsorbents and obtain optimum preparation conditions. Methods: GP-based bio-adsorbents were prepared by thermal pyrolysis under different temperatures (150–400 °C). The morphologies, chemical states, and surface functional groups of the adsorbents were analyzed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Batch experiments were conducted to investigate the adsorption of methylene blue (MB) under various conditions, including contact time, contact temperature, initial dye concentration, and initial pH value. The equilibrium adsorption data were fitted to different kinetic and isothermal models, and the adsorption thermodynamics were also calculated. Significant Findings: The physicochemical properties of the GP-based bio-adsorbents were primarily dominated by the pyrolysis temperature, because their morphologies and surface functional groups of GP-based bio-adsorbents significantly varied with the changes in pyrolysis temperature. The adsorption capacity of GP materials for MB decreased as the pyrolysis temperature increased. At an initial concentration of 50.00 mg L−1, GP150 possessed a higher adsorption capacity of 167.74 mg g−1 toward MB. The possible adsorbate–adsorbent interactions, including electrostatic attraction, hydrogen bonding, and π-π stacking, were recognized. After 10 consecutive adsorption–desorption cycles, GP150 maintained a high removal rate (88%) for MB, demonstrating its excellent adsorption performance, good reusability, and potential application in the treatment of MB-contaminated water.

Removal of arsenic from aqueous solution using magnetic biochar derived from Spirulina platensis

Arsenic contamination in surface waters and groundwater affects millions of people on a daily basis. Oxidation of As(III) to less toxic As(V) is a widely used strategy to enhance the removal of As from solution. This study developed and evaluated a Fe-modified biochar (FeSP600). Spirulina platensis (SP) is one of the most promising microalgae because of its physicochemical properties and potential applications. The high N content of SP may affect the physicochemical properties of the biochar, which could be used as an inherent N source for N doping biochar by carbonization. After Fe modification, the formed Fe species and N-containing components of SP were used to introduce pyridinic N, which can be coordinated with Fe to form Fe-N. We demonstrated that the formed Fe species (Fe0, Fe2+ and Fe3+) and the defective structures in FeSP600 could act as active sites for surface catalytic reactions. FeSP600 not only had magnetic properties but also could effectively remove As from an aqueous solution. These properties were attributed to the release of Fe2+ and the reactive oxygen species (ROSs) generated by the γ-Fe2O3 particles on the crystalline defect structure. As(III) and As(V) removal were affected by the initial pH values. The removal efficiencies for As(III) increased from 57.2 % to 94.9 % as the pH increased from 3 to 9, whereas that for As(V) decreased from 80.1 % to 46.8 %. The presence of coexisting ions either completely (PO43−) or partially (Cl−, CO32− and SO42−) inhibited As removal. The removal of As(V) depended on electrostatic interactions, but As(III) removal was a complex process, including both oxidation and surface adsorption, as the ROSs were able to oxidize As(III) to As(V). Our study demonstrates that FeSP600 has properties that are beneficial for the removal of As(III) and As(V) from aqueous environments. The findings of this study have potential for real-world application in treating As-contaminated water sources, particularly in improving drinking water purification systems in developing countries. More importantly, an assessment of the impact of FeSP600 usage on aquatic ecosystems is required to ensure the safe application of this technology. Therefore, developing methods for mass production of FeSP600 is essential for the commercialization of this technology, necessitating process engineering studies in this area.

Surface decoration of Nb2O5 hollow fibers by graphene oxide for enhanced photocatalytic degradation of methylene blue

AbstractThis paper describes the fabrication of ceramic Nb2O5 hollow fibers covered by a thin graphene oxide (GO) layer using the vacuum‐assisted dip‐coating process for the efficient photocatalysis degradation of methylene blue (MB) under UVC light irradiation. Pristine and GO‐coated Nb2O5 hollow fibers were evaluated for photocatalytic degradation at different initial dye concentrations and pH values. A photodegradation of 66.4% of the dye molecules was achieved using the pristine Nb2O5 hollow fibers at 57.4 ± 0.1 mg mL1, initial MB concentration of 10 mg L−1, and pH of 11. Under the same experimental conditions, the GO‐coated Nb2O5 hollow fibers degraded 100% of the MB molecules. Additionally, the GO‐coated Nb2O5 hollow fibers were successfully reused for four reaction cycles and exhibited suitable long‐term stability. Thus, the proposed ceramic Nb2O5 hollow fibers with a surface decorated by a GO layer presented suitable characteristics for use as a photocatalyst in MB degradation.

Zero-valent iron on graphite-cellulose biochar catalysts for the Fenton degradation of tetracycline from water

Tetracycline (TC), an antibiotic widely used in the treatment of animal and human diseases and promotion of animal growth. However, its uncontrolled discharge to water sources can also cause the promotion of antibiotic resistant bacteria and genes. In this study, graphite and cellulose were used as raw materials to construct a graphite-biochar (G-BC) by carbothermal reactions. This graphite-biochar was subsequently mixed with ZVI with various mass ratios by ball milling to produce graphite-biochars supported ZVI (ZVI/G-BC) catalysts, further used in the heterogeneous Fenton degradation of tetracycline. The materials were fully characterized by different techniques. The removal of TC by BC, G-BC and ZVI/G-BC was tested under different reaction conditions. The best synthesis conditions were achieved at a heating temperature of 700 °C, a graphite content of 20 %, a ball milling speed of 500 rpm, a ball milling time of 5 h, as well as a G-BC and ZVI mass ratio of 1:3. Graphite improves the conductivity and micropore area of the material, which enhances the removal of TC by ZVI/G-BC catalysts in Fenton-like reactions. TC was first oxidized to intermediate products and then further mineralized to CO2 and H2O. The best TC removal performance was obtained with a catalyst dosage of 1.1 g·L1, a hydrogen peroxide concentration of 140 mM and an initial pH value of 3. The reaction data fitted properly a pseudo first-order kinetic equation. TC removal as high as 91 % was achieved even in the 3rd round of reuse. This study reports a novel ZVI material with high conductivity and good TC removal performance.

Effect of natural plant-derived agents on the survival of the pathogenic bacteria Salmonella spp., Listeria monocytogenes in marinated chicken liver meat

This experimental study followed the survival (after inoculation of the bacteria) on non-marinated and marinated chicken liver meat (CLM) samples, with or without added antimicrobials (carvacrol; CA, garlic: G), stored at 4 and 10 °C for 14 days. A pomegranate pomace-based marinade (PPM) alone, or in combination with CA or G was used to monitor the survival/growth of Salmonella spp. and Listeria monocytogenes counts on CLM. A declining trend was recorded for both Salmonella spp. (4.1-4.4 and 3.8-4.3 log CFU/g) and Listeria monocytogenes (3.6-4.6 and 3.3-4.5 log CFU/g) populations in both marinated (absence of antimicrobials) and marinated (with antimicrobials) CLM samples, respectively, at 4 and 10 °C, on day 14 (final storage day). At 10°C, marination and antimicrobial treatments resulted in lower Salmonella spp and Listeria monocytogenes counts on CLM, compared to 4 °C (3.4-3.9 and 1.5-3.7 logs) in both marinated (absence of antimicrobials) and marinated (with antimicrobials) CLM samples, respectively, at 4 and 10 °C, on final day-14. Marination and combinations reduced the total plate count (TPC) by 0.3-0.9 and 0.2-0.6 log CFU/g, as compared to the control (non-marinated) in CLM samples (absence of inoculated bacteria) on final day-14. Concluding, it can be stated that a microbiological shelf-life extension of 9 and 11 days, as compared to the control’s shelf-life, was achieved at 4 and 10 oC, respectively. The initial pH values of the control (non-marinated) and marinated CLM samples at 4 and 10 oC, were 6.62 and 3.12, respectively. During the storage period, pH values for the control CLM were found to be higher, as compared to the marinated samples, and irrespective of storage temperature.

The evaluation of Starmerella magnoliae X3 as a biodiesel feedstock based on triacylglycerol (TAG) production, lipid productivity, and fatty acid profile under nitrogen limitation and acidic pH conditions.

The effects of four initial culture pH values (3, 4, 5, and 6) and nitrogen limitation on growth, TAG accumulation, lipid production, fatty acid profile, and estimated biodiesel quality of Starmerella magnoliae X3 were investigated. TAG and lipid levels were measured by Nile Red fluorescence and sulfo-phospho-vanilin (SPV) techniques, respectively. The results showed that a combination of nitrogen limitation and acidic pH significantly (p < 0.05) increased TAG accumulation, total lipid contents, and lipid productivity in Starmerella magnoliae X3 compared to the control group. Under nitrogen limitation, the highest TAG accumulation was achieved at initial pHs of 3 and 5 after 72h of cultivation, and the highest lipid productivity (0.306g L-1 d-1) was observed after 48h at pH 3; the major fatty acids at the four pH values were oleic acid (63.6%-64%), palmitoleic acid (11.3%-12.5%), stearic acid (9.7%-11.4%), and palmitic acid (9.4%-10%). In addition, both stresses were associated with lower iodine value and higher cetane number of the biodiesel compared to the control. These findings suggest that cultivation in a low-nitrogen medium at an initial pH of 3 or 5 holds promise in increasing TAG production in Starmerella magnoliae X3.

Kinetic, equilibrium, and thermodynamic studies of adsorptive interactions of eosin-B on chemically treated orange peels

The present study investigated the adsorption of eosin B on the surface of powdered and chemically treated orange peels, along with this process’s condition optimizations, kinetics, and thermodynamics. The adsorbent dose (0.1–0.5 g), temperature (298, 303, 308, and 313 K), contact time (15–120 min), initial pH value (2–11) of the solution, and interfering salts (0.01 and 0.1 mol L−1) were all taken into consideration during the experiments. At all investigated temperatures and pH of 2, adsorption was more favourable. Although the Langmuir model might also represent the adsorption data, the Freundlich and Dubinin–Radushkevich (D–R) models provided a good description. The pseudo-second order kinetic model was followed during the adsorption process. The mechanics of the rate-controlling step were examined by applying the intra-particle diffusion-based mass transfer model to the experimental data. It was discovered that the only process that controlled the rate was intra-particle diffusion. The adsorption process appears to be spontaneous, and endothermic and involves van der Waals forces based on thermodynamic data.

Sustainable Removal of Cr(VI) from Wastewater Using Green Composites of Zero-Valent Iron and Natural Clays

Composites for efficient removal of hexavalent chromium Cr(VI) from industrial wastewater were obtained by deposition of nano-zero-valent iron (nZVI), synthesized by environmentally friendly synthesis using oak leaf extract, on inexpensive, natural, readily available and cheap natural raw materials, sepiolite (SEP) or kaolinite/illite (KUb) clay, as support. nZVI particles were deposited from the FeCl3 solution of different concentrations, with the same volume ratio extract/FeCl3 solution (3:1), and with different masses of SEP or KUb. Physico–chemical characterization (SEM/EDS, FTIR, BET, determination of point of zero charge) of the composites and nZVI was performed. The results of SEM and BET analyses suggested more homogeneous deposition of nZVI onto SEP than onto KUb, which ensures greater availability of the nZVI surface for Cr(VI) anions. Therefore, the higher Cr(VI) removal at all investigated initial pH values (pHi) of the solution (3, 4 and 5) was achieved with the SEP composites. The adsorption results indicated that the elimination of Cr(VI) was achieved via the combined effect of reduction and adsorption. The removal of total chromium at pHi = 3 was approximately the same as that of Cr(VI) removal for the KUb composites, but lower for the SEP composites, indicating lower removal of Cr(III) compared to the reduced Cr(VI). The SEP/nZVI composite with the highest removal efficiency was applied for Cr(VI) removal from real wastewater at pHi = 3 and pHi = 5. The results demonstrated the high Cr(VI) removal capacity, validated the assumption that a good dispersion of nZVI particles is beneficial for Cr(VI) removal and showed that the produced green composites can be efficient materials for the removal of Cr(VI) from wastewater.

Efflorescence and mitigation of red mud–fly ash–phosphogypsum multicomponent geopolymer

In this study, the efflorescence formation of geopolymers synthesized from red mud (RM), fly ash (FA) and phosphogypsum (PG) was evaluated to investigate the influence of different proportions. The mechanical properties, leaching properties and microstructure of the geopolymers were studied through compressive strength test, visual observation of efflorescence, leach properties and a series of microscopic tests by changing PG content (0–25 %), reducing precursor alkali concentration (4–10 %) and changing FA content (0–300 g). The results show that PG rich in SO42- lead to the formation of a new efflorescence product Na2SO4, the presence of Aluminum (Al) in FA is beneficial to the polymerization degree and chemical stability of the geopolymer gel, and excessive or insufficient alkali content will affect the polymerization reaction and the efflorescence resistance of the geopolymer. The geopolymers are synthesized with 55 % RM, 25 % FA and 20 % PG as precursors and activated with 10 wt% Na2O, which shows good strength and resistance to efflorescence. Proper alkali content is conducive to the formation of geopolymer strength phase. The initial pH value required for the suitable effective strength and strength development of the multicomponent geopolymers in this study is about 10.5–11.3, which can provide a reference for the synergistic utilization of RM-FA-PG.

Synthesis and characterization of magnetic carbon dots (CDs)-based hybrid material as an adsorbent for the removal of organic dye from water

In recent years, the rapid advancement of materials science and the desire for new functions has led to an enormous demand for novel materials, which could be used in various applications. As a result, hybrid materials have gained the interest of the scientific community due to the infinite combinations of individual components, which could lead to materials with unique properties. In this study, a carbon dots (CDs)-CuFe2O4 nanohybrid material was successfully prepared through a solvothermal process and utilized as an adsorbent for the removal of Congo Red (CR) dye from aqueous environment. The nanohybrid material combines interactive surface functional groups due to CDs and high magnetic saturation due to CuFe2O4 nanoparticles, resulting in enhanced selectivity towards CR dye and easy separation after utilization with an external magnet. The as-prepared material was characterized by various techniques, including XRD, micro-Raman, FT-IR, HR-TEM/EDS, N2 porosimetry, and SQUID. Finally, its capability in the removal efficiency of CR dye was investigated at different initial CR concentrations, contact times and pH values via UV–Vis spectroscopy.

Construction of heterojunction superparamagnetic Cd0.5Ag0.5Fe2O4 nanocomposite photocatalyst for simulated textile effluent oxidation

Abstract Significant attempts have been recently made regarding nanomaterials due to their several environmental applications especially in wastewater treatment technologies. Among the available nanoparticles, ferrite based substances are gaining a special interest since their superior characteristics such as their magnetic nature, high adsorption capacity and large specific surface area. In this regard, Cd0.5Ag0.5Fe2O4 was prepared using the green simple co-precipitation route. Then, the sample is characterized via Scanning Electron Microscopy (SEM) that proved the produced material’s surface morphology. The substance is then employed as a catalyst source for Fenton reaction to oxidize textile effluent solution containing Rhodamine B (Rh-B 6G) dye. The oxidation experiment conducted under ultraviolet (UV) light with the ferrite-based Fenton catalyst supplemented with hydrogen peroxide showed an exceptional removal rate of up to 94% removals. Notably, the oxidation system is significantly impacted by the operational variables. The oxidation efficiency of the dye was maximized at pH 3.0 and 50 mg/L and 1600 mg/L for ferrite-based Fenton catalyst and H2O2, respectively. The impacts of the operational factors, i.e. initial pH value, initial dye concentration, catalyst, and H2O2 concentrations were also investigated. This perspective introduces the role of a superparamagnetic material to be a recyclable sustained catalyst.

Machine learning-assisted optimization of food-grade spirulina cultivation in seawater-based media: From laboratory to large-scale production

The shortage of food and freshwater sources threatens human health and environmental sustainability. Spirulina grown in seawater-based media as a healthy food is promising and environmentally friendly. This study used three machine learning techniques to identify important cultivation parameters and their hidden interrelationships and optimize the biomass yield of Spirulina grown in seawater-based media. Through optimization of hyperparameters and features, eXtreme Gradient Boosting, along with the recursive feature elimination (RFE) model demonstrated optimal performance and identified 28 important features. Among them, illumination intensity and initial pH value were critical determinants of biomass, which impacted other features. Specifically, high initial pH values (>9.0) mainly increased biomass but also increased nutrient sedimentation and ammonia (NH3) losses. Both batch and continuous additions could decrease nutrient losses by increasing their availability in the seawater-based media. When illumination intensity exceeded 200 μmol photons/m2/s, it amplified the growth of Spirulina by mitigating the light attenuation caused by a high initial inoculum level and counteracted the negative effect of low temperature (<25 °C). In large-scale cultivation, production efficiency would be reduced if illumination was not maintained at a high level. High salinity and sodium bicarbonate (NaHCO3) addition promoted carbohydrate accumulation, but suitable dilution could keep the required protein content in Spirulina with relatively low media and production costs. These findings reveal the interactive influence of cultivation parameters on biomass yield and help us determine the optimal cultivation conditions for large-scale cultivation of Spirulina-based seawater system based on a developed graphical user interface website.

Controllable Synthesis of Magnetic Composite Derived from MIL-88D and Study on Adsorption Properties of Cu2+

In this paper, MIL-88D (Fe) with spindle shape was prepared by the hydrothermal synthesis method, a metal oxide with a new structure was obtained by calcination at different temperatures as a precursor, and a magnetic iron oxide composite was prepared successfully. At the same time, it was used as an adsorption material for the adsorption of heavy metal ions Cu2+. The influence of the initial pH value and adsorption time on the adsorption effect was investigated, the adsorption kinetics and adsorption isotherm were further fitted, and the adsorption mechanism was preliminarily analyzed. The results show that the magnetic iron oxide composites have a good adsorption capacity for Cu2+. The pH value is an important parameter that affects the adsorption effect. The adsorption of Cu2+ by magnetic iron oxide composites reached adsorption equilibrium in 30 min. The adsorption of Cu2+ by magnetic iron oxide composites conforms to the second-order reaction kinetics and Langmuir adsorption isotherm equation, which indicates that the adsorption process mainly occurs through chemisorption and typical single-molecular-layer adsorption.